Purpose To-Do List Market Comparison Price Feedback First Step First step features Research and development General Fin design Main Bar Main bar features Retraction system Research and development Main bar length Main bar material Main bar interface with harness lines Build It Yourself Parts Tools Procedure Installation Other Ideas Main bar with built-in retraction system First step with 3 fingers General Blog Latest entry

Video of the auto-deployment (691 kB, *.mp4, MPEG-4 H.264) Video of in-flight activation (910 kB, *.mp4, MPEG-4 H.264)

Purpose.

I invested much personal time (and money) towards achieving a better speedbar design because of disapoinments with available designs. See Market Comparison. My guess is that I spent 250 hours on this project so far (2005/12/15). This page is to share the knowledge learned along the way.

Pilots are free to use the ideas shown here to build a similar unit for themsleves. If someone wants to mass produce this design, that should lower the purchase price for buyers. All I ask in exchange is a small recognition fee as the inventor (I'm easy to negotiate with). In the meantime, I will hand-craft one unit at the time for those who immediatly want to purchase (Price) this speedbar.

To-Do List.

This used to be a long list, now it is simple:

1. Make a reasonable effort to find/work with a high-volume manufacturer, to lower the Price.

Market Comparison.

Who is this design for? There are many different "ideal" speedbar designs according to the rest of your equipment setup. This design is best suited for pilots who:

• Use their speedbar to optimize glide during a transition. They want to be able to use it often and find it easily without their hands.
• Do not use a footrest. This design would loose its benefits if its gets tangled with something else.
• Use a regular harness (legs remain exposed) so the speedbar can hang.
• Can spare an extra second (not in panic mode to activate speedbar when launching in excessive wind) to insert the second foot onto the first bar to assure a symmetric line extension.
• Have a retraction system in their harness to keep this unit snug against it and avoid stepping on it during launch/landing.

It only made sense to provide a new design, if there could be improvements over what is available on the market.
This Excel spreadsheet shows the advantages over existing speedbar designs.

Price.

The J-Rod: Think of it as the "Hot Rod" of speedbars. It is designed to best match a list or requirements (see Market Comparison). Low production and hand-crafted.

The price (subject to change) is 248 $US + packaging & shipping.
Payment must be made in advance. Send me an email to place your order.
Thank you for supporting better product development.

Price justification: I have to make it worthwhile for me to build one unit at a time for pilots. Materials are cheap, I will guess at about 20$. There is fuel and driving+shopping time to get the parts. But the big thing is my personal time to do the manufacturing work. I'm guessing 2.5 hours of manufacturing work at this time (until I find shortcuts). Difficult to price my personal time away from my wife on evenings and weekends, but I am setting it at 75 $/hour. All the time I spent researching and developping this product is not part of the price as I did it all for myself, following my quest of better equipment.
So: 188 (2.5 hours times 75$) + 20 (materials) + 40 (acquiring materials: fuel, driving and shopping time) + 0 (250 hours of research & development) --> 248.

You can Build It Yourself for your personal use.

The best thing to happen for everyone...
Would be for someone to start manufacturing this product in Europe (where most PG pilots are) and distribute from there. Price would be reduced for buyers, I just ask for a small inventor's fee on each unit (I'm easy to negotiate with), and the manufacturer would make a profit. If you know someone who wants to manufacture this product, now is a good time to start discussing this. Please put me in contact.

Feedback.

Pilots who purchased:

• Richard Hammer, 2006/11/28: RidgeDancer Article.

Pilots who followed the Build It Yourself instructions:

• Rusty Harrison, 2006/4/15: It feels wonderful to just lift my foot and catch the first bar with my heel. Full message with pictures.
• Joe DeBriyn, 2007/2/1: It works great. Picture.
• Paul Schwartz, 2007/4/24 (source): Thanks Jerome, I followed your instruction set and made a J-Rod speedbar for my son Allen. He always had trouble getting hold of his speedbar before, but not anymore. Being small and light on his wing he is in need of the bar quite often. I think your design saved his butt a few weeks ago when he launched in strong winds and rose into even stronger winds above. He was unable to penetrate forward laying back flat as possible, on full speedbar, with hands at his sides off the brake toggles. He was able to manuever to the side of the ridge and out of the compression and strong wind to find an alternate LZ. I shudder to think about what could have happened had he not been able to get a hold of his speedbar like before. Thanks again for sharing your potentially life saving design. Sincerely, Paul & Allen.

Others:

• James Bradley, 2007/3/3: I was asked to demo a glider recently that by chance had one of the few production J-Rods on its harness. So, incidentally, I got to demo the J-Rod. I found it always right under my foot. The first step is a bar, not a wire loop, and I much prefer the bar. There is no loss of travel as there is with some other two step solutions. It was completely unobtrusive and undistracting and did what I would like it to do. In short, it works great. Nice one, Jerome! Disclaimer: I do know Jerome, but so far he has not paid me anything.

First Step.

First step features

• Easy grab with a foot (no hand). Video of in-flight activation (910 kB, *.mp4, MPEG-4 H.264).
• Grab quality is constant over time.
• Easy entry of the 2nd foot.
• It is a bar instead of a wire loop, so your feet are not squeezed together. Prolonged use remains comfortable.
• No significant loss of leg extension before the first step starts pulling the accelerator lines. This contrasts with wire loops which must first straighten.
• Collapsable to an almost linear dimension (easy storage).
• The fins automatically return to their in-flight location after being collapsed for storage (nothing to forget). Note that the fins have limited rotation to achieve this goal. Video of the auto-deployment (691 kB, *.mp4, MPEG-4 H.264).
• Simplicity, and minimization of relative movement between parts.
• Resistant to storage abuse by allowing overall structure to collapse.
• Will not lock into a groove of your boot.
• Adjustable bar spacing, adaptable to your wing's accelerator travel range. The line between the bars can easily be replaced by the owner, using 3 mm static cord. Note: The default 22 cm bar spacing (distance between foot contacts) is judged a minimum to allow easy grabbing of the first step, while still providing significant first step acceleration: 1/3 accelerator travel for a wing with 33 cm travel.
• Corrosion resistant.
• Fins also serve as leg protectors (extra radius at bar ends), in the event the bar gets between the legs while running.
• Dead weigth used as balance counterweight, is minimized by use a leverage effect. Only 14 g (0.5 oz) needed.

	2006/4/15. In flight.
	This graphically demonstrates why a small forward displacement of the first step, makes such a significant difference in ease to grab it with the foot.
	2006/11/24. Global view. Total weight is only 165 g (5.8 oz).
	2005/12/10. Fins folded for compact storage. Notice how the tail end of the fins meet perfectly, without overlap. Update needed: Picture to show relocated (closer to main bar end) line going to the first bar.
	2005/12/10. Detail of the end of the first step bar. Rotation of the fin is limited (desired effect) by the 2 bungee lines on either side of the load line (blue).

Research and development

General

	2005/11/24. Bar length. It was found that a free span of 23.5 cm is required to comfortably apply both booth soles. To this span is added 0.65 cm (1.5 mm cord radius + 5 mm hole axis from end) at each end, for a total length rounded to 25.0 cm. Note: The effective load span (between line axis) is 24 cm.
Decision matrix (Excel spreadsheet)	2005/11/9. Finding the best way to connect the line from to the main bar onto the 1st step's bar. The "Simple_InOut_2" concept (picture) is chosen as the best.
Decision matrix (Excel spreadsheet)	2005/11/11. Finding the best way to compress/center the end fins onto the bar ends. The "SingleBungee_OutInFin" concept (schematic drawing) is chosen as the best.
Bar Material Selection (Excel spreadsheet)	Bar material selection. All other parts related to this bar have been designed with the consideration that this bar's cross-section dimensions can change without significant re-design work. 2005/11/16. The Aluminum bar (5/8" OD, 0.093" wall or about 7/16" ID) alone (no fins, bungee, counterweights) is 68 g (2.4 oz) for a 25 cm length. Stress analysis (see spreadsheet) indicates a safety factor of 5.8 for a 175 lb pilot and 3:1 accelerator pulley ratio. 2005/11/18. I found a better compromise between safety factor, weight and cost (see spreadsheet). This bar will be changed to 2024-T3 Aluminum, 0.5" OD, 0.065" wall. Stress analysis (see spreadsheet) indicates a safety factor of 3.2 for a 175 lb pilot and 3:1 accelerator pulley ratio. This bar is less critical that the main bar, which in a worst case scenario of 1st bar failure, the main can still be used (just need a hand to help place a foot on the main bar). I expect a weight saving of 2 oz (considering the equivalent reduction in counterweight).

Fin design

Dimension optimization (Excel spreadsheet)	2005/12/2. Study of optimal overall dimensions between the forward displacement of the bar, and dimension to the point where the line is held. Selected dimensions: 4.0 cm forward first bar, with Theta = 35°.
	2005/12/6. Design parameters: Planar dimensions: Bar end protection: 1" diameter disk. Horizontal length: The distance between [rearmost hole axis of bungee line feeding into bar] to [fin rear end] must not exceed 12.5 cm (1/2 bar length) + 1 mm (bar end "snap-in bushing" thickness) to avoid fin overlap when folded for storage. Load line exit (at the top): Location: The load line will bend to vertical, 4 cm back from bar center axis, 5.71 cm above it. This produces the desired 35° lower line angle, with 1.26 cm lost 1st step travel. Fixation: Two 3/32" holes, separated (center axis) by 4.5 mm, allow the passage of a 3/32" width cable tie (3" long, rated at 18 lb), to hold the line passage position. Virtual line joining the holes, to be perpendicular to the lower line axis, so that the prescribed location (where the 3mm line bends) is above it, reducing the height of the fixation point, reducing the needed physical fin height. Load line slip is allowed with some friction. Holes for 1/8" bungee line. 2 holes made with 1/8" drill (same diameter as bungee line is OK), with axis spaced by 7.5 mm. When bungees are tensioned they have smalled OD, and the under-tension external spacing of the 2 bungees lines will fit the bar Nylon "snap-in bushing" ID without looseness. Relative hole placement is rotated: Considering a line between the 2 holes, its normal must pass by the point where the fin holds the line. Personal safety: No pointy ends which could hurt legs. Loads: Sufficient bending strength at the bar end circumference, in the event the bar gets caught between legs, so the extra diameter serves as a load distribution protector. Note: Bending moment of inertia grows with the cube of the thickness. No creep deformation while fins are collapsed, and being under constant bending load from the recoil bungee. While fins are collapsed, and squeezed under storage between bar and harness. These loads are difficult to predict, but we can assume bending loads in proportion to the fin's overall dimensions. So there should be more material width, perpendicular to the longest dimension. Material compliance can help as long as it return to its original flat shape. Minimize weight, at least in the forward part where it is not usefull for leverage. Options: Weight-reduction holes: We can use a thicker material to have better strength where needed, and reduce weight elsewhere. A surface film can be used to provide a smoth outer surface if desired. Different materials in different areas: Thicker/stronger near bar end, Thinner/compliant elsewhere. Adhesives (Tried Krazy Glue) not usefull so far, so mechanical fasteners would be used to join different materials.
	2005/12/9. Materials: Requirements: Must not be fragile, and "snap" when bend. Must not creep under folding bending load. Candidates, by order of preference: Blue clipboard plastic. 0.133" thick. 3.57 kg/m2 surface weight. Adhesives: Krazy Glue not good. The fins in the 2005/11/1 prototype weigh 20.4 g (0.718 oz) each or 40.8 g (1.436 oz) for both, and together represent 20.5% of the currently predicted total weight (7.0 oz). Good: Stiff, does no creep under folding bending load. No obvious "snap-in bushing"/fin wear, where a concentrated compression load occurs during fin folding. Some ductile bending phase before snaping under excessibe bending. Bad: High rigidity makes it gather more stress loads during storage. Black clipboard plastic. 0.12" (guess) thick. Found at Staples. Good: Black color is cool. Stiff, so would probably no creep under folding bending load. Bad: Under excessive bending load, it snaps without warning. High rigidity makes it gather more stress loads during storage. White translucid binder plastic. 0.080" thick. 2.15 (guess) kg/m2 surface weight. Adhesives: Krazy Glue not good. Good: Compliant, so will tolerate unexpected bending during storage. Does not "snap" break. Bad: Requires assistance from an additional structure to avoid creeping under folding moment, even when maxing the planar width near the bar end. Obvious "snap-in bushing"/fin wear, where a concentrated compression load occurs during fin folding. Thin material makes it difficult to create enough hole edge radius.
	2005/12/15. Counterweight: 14 g (0.5 oz) needed with 2005/12/10 design. Material: Avoid lead (as in wheel balancing self-adhesive weights) or seal it to avoid its toxicity. Stainless steel (about 2/3 the density of lead is good) would be a better choice. The self adhesive foam tape used in automotive lead weight, would require a safety fixation. Avoid metal-metal contact as between a bolt head to secure the counterweight and the bar. Possible solutions: Protective tape ( also serve to improve bar grip? ), or use plastic fasteners. Potential solution (2005/12/13): Material. Stainless Steel fender washers, 0.045" thick, 7/32" ID (3/16" Nominal), 1" OD. Each fender would weight 4.37 g (0.154 oz) for a density of 7930 kg/m3, so using 2 of them on each end fin (total weight of 17.5 g, 0.62 oz), and considering their CG slightly forward of the more concentrated lead weight, could make this right. See related Excel worksheet. Also making an extra securing hole would be OK, as we have some spare weight. Fixation. The fin + 2 washer thickness is 0.223" (0.133" + 2 x 0.045"). Options considered, by order of preference: Option 1 (Selected). A 13/64" hole is made in the fin. From the outside of the fin, use the female part of an Aluminum "post with screw", 3/16" OD, min clamp length of 3/16" (0.1875"). From the inside, use a 8-32 thread white Nylon plastic "binding head" bolt, 1/2" length. Plastic bolt is reduced in length prior to insertion. With only plastic on the inside of the fin, the bar will not get scratched. 90% solution: I just wish the plastic bolt head was not so thick, but that is just a cosmetic issue. Option 2. A 13/64" hole is made in the fin. From the inside of the fin, use the female part of an Aluminum "post with screw", 3/16" OD, min clamp length of 3/16" (0.1875"). From the outside, use the male screw part. Bar has some potential for getting scratched, so a plastic film should separate the Aluminum parts. Loctite should be used to prevent the screw from loosening. 75% solution. Option 3. A 13/64" hole is made in the fin. From the outside of the fin, use the female part of an Aluminum "post with screw", 3/16" OD, min clamp length of 3/16" (0.1875"). From the inside, use a black plastic 5/32" "hole shield clip". With only plastic on the inside of the fin, the bar will not get scratched. The plastic clip is pushed into the Aluminum post, its "gills" producing a tight fit insertion. Washers can be separated from the fin, using thumbnails. Maybe if I added an adhesive when the clip is inserted? 75% solution.

Main Bar.

Main bar features

• Accelerator line length and retraction bungee lines are easy to attach to the end loops. For easy adjustments, a Bowline is recommended.
• Protective end caps protect your legs, equipment, and keeps the inside clean (also avoiding extra dirt weight).
• Resistant to storage abuse.
• Corrosion resistant.
• Neglectible caming effect (pressure discomfort on calves during 1st step acceleration) thanks to the bar's large diameter.
• "Short legs" option. For those with short legs, having to push the main bar with your toes to achieve maximum speed, there is a solution: Increase the Main bar length to match the harness' line exit holes. Just measure the spacing on your harness between the line exit holes (typically 37 cm) and a custom-length bar will be made. The compromise is that the longer bar will also use a thicker wall (0.065" instead of 0.049") to maintain the same strength safety factor, both contributing to a weight increase. For a 3/4" OD, 10 cm longer (and thicker wall) bar the weight increase is 39 g (1.4 oz).

	2006/11/24. Top view of the bar end.
	2006/11/24. Bottom view of the bar end.

Retraction system
Why you want one: Bars are retracted for easier running on the ground. Did you ever see a pilot trip on his own bar? Some believe it also offers a safety advantage following a Frontal Collapse (Recovery), where the loss of tension in the A riser will have it dislodge from your feet, and swing back extended to the rear bottom of your harness where it can lock.
Although I am a believer in bar retraction systems (typically an elastic bungee cord that pulls the bar back up) I also believe it should be integrated inside the harness: More room for it, and its mechanism does not contribute to the weight to be lifted. Note that a Main bar with built-in retraction system has proven possible. More harness models are arriving on the market with built-in retraction systems (not all equally good). Make sure your retraction system does not rely on riser tension, and avoid mechanisms you can forget to set like accelerator line cord locks. In the meantime it is not too difficult to devise your own retraction system with an elastic bungee cord attached to the main bar and enough length to allow the extension of the main bar. The design of this main bar does not include a built-in retraction system, but is adapted to connecting with the end of an elastic bungee cord of 3 mm (1/8") diameter.

Research and development

	2005/12/10. Main bar length. For reference, I measured the line spacing (between cord axis) of a few manufactured main bars:       25.9 cm for the Nova standard bar (0.86" OD, 0.035" wall).       26.5 cm for the Sup'Air (0.635" OD)       28.3 cm for the SystemX (obsolete). Feet width spacing: The minimum length for this bar is dictated by: 24 cm line spacing on the first step bar + two ( 2.0 cm distance to bar end to allow for X-Lock holes ): 28.0 cm minimum. Aside from the weight saving (for same strength safety factor) benefits, I found negative side-effects of a shorter bar (see image on the left): Change in line paralellism, reduces bar travel efficiency. This effect is at its worst during initial extension. Reduced line slack at trim: OK as long as some remains. This is the most noticeable effect. You will loose as much accelerator line slack at trim speed (not accelerated) as there is an offset between wher the line exits your harness and to where it connects on the main bar. Example: Harness with line exit spacing of 38 cm, line spacing on the main bar is 25 cm. Doing the math, you loose 6.5 cm (2.6") of line slack. This corresponds what I noticed when recovering line slack after replacing as Sup'Air bar, with a bar matching the exit holes on my harness, going approximatly from 5 to 10 cm slack. Since I currently have about 10 cm of line slack at trim with a full-length prototype bar, I could theoreticall shorten it by 20 cm, before having my speed line under tension at trim: From the full-length 38 cm -> 18 cm minimum. Bar spacing needs to be reduced: Bad, but neglectible effect. The bar spacing needs to be reduced in relation to the line angle change between: Full extension of the first and main step. Example: Harness with line exit spacing of 38 cm, bars are pushed 45 cm from harness edge with legs extended, line spacing on the main bar is 25 cm, main bar will be pushed 22 cm more after full use of the first step (another 2/3 of acceleration for a 33 cm line accelerator travel, and less than that spacing make it difficult to grab the 1st step). Doing the math, the lines are extended 21.57 cm (compared to the 22 cm push). So there is only 0.43 cm missing (0.17") from our push. Conclusion: Not a significant concern. More line friction: Not a significant concern. The lines leaving the harness in a non-parallel manner, will induce friction at their exit point. This causes wear on both the lines, and harness contact points. In practice, I don't see this as a significant concern, also justified by most manufactured bars being about 10 cm shorter than the line exit points on the harness. With the current Aluminum bar (0.75" OD, .049" wall), each cm saved represents about 1.88 g (0.066 oz). Decision: Respecting the largest minimum (28.0 cm), the length will be changed from the current full length of 38 cm (loaded lines remain parallel outside a Sup'Air Profeel XC2 harness), to 28.0 cm (27.0 cm axial spacing of lines arriving from harness). Note: The effective load span (between line axis) is 27.0 cm.
Bar Material Selection (Excel spreadsheet)	Main bar material. All other parts related to this bar have been designed with the consideration that this bar's cross-section dimensions can change without significant re-design work. 2005/11/16. The Aluminum bar (1" OD, 0.060" wall) alone is 117 g (4.1 oz) for a 38 cm length. Stress analysis (see spreadsheet) indicates a safety factor of 7.0 for a 175 lb pilot and 3:1 accelerator pulley ratio. 2005/12/10. I found a better compromise between safety factor, weight and cost (see spreadsheet). This bar will be changed to 2024-T3 Aluminum, 0.75" OD, 0.049" wall, 28 cm length. Stress analysis (see spreadsheet) indicates a safety factor of 5.1 for a 175 lb pilot and 3:1 accelerator pulley ratio.
#1:  #2: No picture. #3:  #4:  #5:	2005/12/26. Main bar interface with harness lines. From the options listed below, the best compromise was selected for durability (accelerator and bungee line wear), easy fabrication, easy line adjustments/disconnect (no tight knots to undo). Adjustments are typically limited to when changing wing or harness, but we still want to avoid having dealing with knot difficult to under after being loaded. By order of preference: 90%: Line loop for everything + Single bar hole. A simple loop provides an attachment point for everything (accelerator and bungee line). Fabrication is very easy: One hole, and a short length of line with internal knots. Simulated fatigue abrasion test showned almost no wear. In the worst case, the loop is inexpensive (10 cm of 3 mm diameter static line) and easy to replace by the owner. Positive: Easy fabrication (only 1 hole). Intuitive interface (attach everything to the exposed loop). Easy connection inspection (knots still tight). Neutral: Adjustments of line lengths using a Bowline: Easy to undo after being loaded, but length adjustment has to be measued away for the bar. Negative: Cosmetic: Exposed excess accelerator line. 80%: Line loop for everything + Double bar hole. A simple loop provides an attachment point for everything (accelerator and bungee line). Fabrication is very easy: Two hole, and a short length of line with internal knots. Positive: Easy fabrication (2 holes). Intuitive interface (attach everything to the exposed loop). Easy connection inspection (knots still tight). Neutral: Adjustments of line lengths using a Bowline: Easy to undo after being loaded, but length adjustment has to be measued away for the bar. Negative: Cosmetic: Big hole in end cap to cover both bar holes, so loop can the threaded. Cosmetic: Exposed excess accelerator line. 50%: Accelerator line X-Lock + Bungee loop is locked inside by accelerator line square knot. This eliminates the main problem of excessive wear of the bungee line loop in the Accelerator line X-Lock + Bungee loop is locked inside by accelerator line design. Positive: Easy and precise accelerator line length adjustments. Excess accelerator line hidden inside the bar. Negative: Non-intuitive interface. Complex threading pattern to learn. Many holes need to be made at precise locations for the X-Lock. Connection inspection required removal of end caps. 30%: Accelerator line X-Lock + External line loop for the bungee. A combination of other ideas. This eliminates the main problem of excessive wear of the bungee line loop in the Accelerator line X-Lock + Bungee loop is locked inside by accelerator line design. Positive: Easy and precise accelerator line length adjustments. Excess accelerator line hidden inside the bar. Negative: Short loop for bungee line attachment needs to be remove/inserted when the acclerator line is removed/inserted. Non-intuitive interface. Threading pattern to learn. Many holes need to be made at precise locations for the X-Lock. Connection inspection required removal of end caps. 10%: Accelerator line X-Lock + Bungee loop is locked inside by accelerator line. There is a problem with having a bungee loop inserted through a hole and locked internally with the accelerator line: The bungee line under tension will reduce in diameter and partially pull the loose end of the locking accelerator line into the hole, until the bungee line friction on the hole edge stops the motion. This caused excessive wear on a prototype I had been using in flight for about 15 hours. Positive: Easy and precise accelerator line length adjustments. Excess accelerator line hidden inside the bar. Negative: Excessive wear on the bungee line. Non-intuitive interface. Threading pattern to learn. Many holes need to be made at precise locations for the X-Lock. Connection inspection required removal of end caps.

Build It Yourself.

Parts. You should have these:

• First bar end Nylon "snap-in bushing" (You need 2). They need to fit snug on the inside diameter of your first step bar, and provide a low friction contact for the fins when the are folded for storage.
  • USA: Suppliers (by order of recommendation):
    • McFadden-Dale. Available at their Anaheim location, but not in Santa Ana. Picture of the part (left one). This is the one I used. I like how the flange OD matches the bar OD: Picture.
      Reference: Servalite Products Inc, Moline IL 61265. No, NSB-2030, Nylon Snap Bushing, 1/4 in ID, Fits 3/8 in hole, Regular. Written on flange end: KSS, SB-10.
    • DeNault´s TrueValue Hardware. Reference: "Nylon Snap-In Bushing", 1/4" ID Regular, 3/8" Hole size, 66382-B from Midwest Fastener Corporation.
      Note: This bushing is slightly different from the one available at McDadden-Dale. Made for the same hole size, but its wall is a bit thicker (smaller ID), and the diameter of the flange head is slightly smaller. I put one inside the end of the tube for a first bar: It was snug enough, but the flange OD was visibly smaller thant the bar's OD, with maybe 0.5 mm missing in radius.
  • Europe: Need to find closest equivalent to a Nylon "Snap-in bushing": 9.53 mm hole size (must fit snug inside you first bar ID), 6.35 mm ID (big enough to allow one 3 mm line and 2 bungee lines), 12.7 mm flange OD (must match first bar OD). In red, are suggested dimensions. It is important to find a part that will offer low friction for the fin when its is folded for storage, and fit snugly inside the bar end.
• First bar: 2024-T3 Aluminum (no substitute, strength dependant) round tubing.
  • USA: 0.5" OD, 0.065" wall, 25.0 cm length (clean straight cuts). Suppliers (by order of recommendation):
    • Aircraft Spruce & Specialty Co. From their Round Aluminum tubing page, select: Alloy = 2024T3, Outside Diameter = 1/2, Wall = .065. You can get just the length you need: 1' (for 3.75$).
    • McMaster-Carr. Look under: "Pipe, Tubing, Hose and Fittings ", "Metal Tubing", "Aluminum", "Round", Outside Diameter = 0.5", Wall Thickness = 0.065", Pick the shortest lenght (6', but you only need 1').
  • Europe: Need to find closest equivalent to: 12.7 mm OD, 1.65 mm wall, 25.0 cm length (clean straight cuts). It is important to: Find a matching end "Snap-In Bushing", and to pass the required safety factor in Bar Material Selection. I can help with selecting a material if you give me available tube sizes near the suggested dimensions (in red).
• Main bar: 2024-T3 Aluminum (no substitute, strength dependant) round tubing.
  • USA: 0.75" OD, 0.049" wall, 28.0 cm length (clean straight cuts). Suppliers (by order of recommendation):
    • Aircraft Spruce & Specialty Co. From their Round Aluminum tubing page, select: Alloy = 2024T3, Outside Diameter = 3/4, Wall = .049. You can get just the length you need: 1' (for 3.15$).
    • Note: McMaster-Carr does not offer this size.
  • Europe: Need to find closest equivalent to: 19.05 mm OD, 1.24 mm wall, 28.0 cm length (clean straight cuts). It is important to pass the required safety factor in Bar Material Selection. I can help with selecting a material if you give me available tube sizes near the suggested dimensions (in red).
• Aluminum surface polish:
  • USA: Products (by order of recommendation):
    • "Blue Magic - Liquid metal polish".
  • Europe: Products (by order of recommendation):
    • Need to find equivalent.
• Soft end caps for the main bar ends. Do not get the heavy/thick chair leg end caps (easy to find those), get the general purpose lighter/thinner softer ones.
  • USA: 3/4" end cap. Suppliers (by order of recommendation):
    • McFadden-Dale: The one in Santa Ana has them (but not in Anaheim). Picture of the part.
      Reference name: 3/4 Vinyl Cap.
  • Europe: Products (by order of recommendation):
    • Need to find equivalent.
• Counterweight parts: Picture.
  • USA:
    • Weight. 4 stainless steel fender washers (2 for each fin), 0.045" thick, 7/32" ID (3/16" Nominal), 1" OD. I found them at DeNault´s TrueValue Hardware, but most hardware stores should have them.
      Reference: Midwest Fastener Corp, 3/16 X 1 Fender Washers, 0.45 $, 63387 G.
    • 2 female parts of an Aluminum "post with screw". 8-32 thread. 3/16" OD, min clamp length of 3/16" (0.1875"). I found them at DeNault´s TrueValue Hardware, but most hardware stores should have them.
      Reference: 0.49 $, 66963 C.
    • 2 (white) Nylon plastic "binding head" bolt, 1/2" length (will be cut). 8-32 thread: They need to screw into the female part of the Aluminum "post with screw". I found them at DeNault´s TrueValue Hardware, but most hardware stores should have them.
      Reference: 0.24 $, 62523 C.
  • Europe:
    • Weight. 4 stainless steel fender washers, 1.14 mm thick, 5.56 mm ID, 25.4 mm OD. The total weight for each fin must be 7.1 g (0.25 oz) or slightly more. Supplier.
    • 2 female parts of an Aluminum "post with screw". Thread dimension must match the corresponding Nylon bolt. 4.76 mm OD, min clamp length of 4.76 mm. Supplier.
    • 2 (white) Nylon plastic "binding head" bolt, 12.7 mm length (will be cut). Thread dimension: They need to screw into the female part of the Aluminum "post with screw".
• 2 small (blue, black...) cable ties: About 2 mm in width.
  • USA: Sold as 3" long and rated at 18 lb. Found blue ones (matching my fin material) at McFadden-Dale in Santa Ana.
  • Europe: Need to find equivalent. They must fit snugly through the holes at the top of the fin.
• 1/8" (about 3 mm) elastic bungee line. At least 60 cm (2').
  • USA: Found at Adventure 16 in Costa Mesa. Picture.
  • Europe: TBD.
• 3 mm static (low stretch) line. At least 90 cm (3').
  • USA: Found at Adventure 16 in Costa Mesa, 0.15 $/ft. Picture. Label on the roll: 3MM x 500 Accessory Cord LT, 3801-03-00500, 00340234 | 051121305.
    Manufacturer: New England Ropes. Color: "Light Blue/Purple".
  • Europe: TBD.
• Fin material: 0.133" (3.38 mm) thick rigid plastic, typically used for clipboards. Look for it at your local office supply stores. Pick a cool color.

Tools. You should have these:

• Drill, ideally an drill press with table vise.
• Drill bits: diameter size 3/32", 1/8", 5/32", 13/64".
• Deburring tool, for reaming both the outside and inside of holes in Aluminum. The one I have.
• File or something to smooth the edges of the fins.
• Ruler, in cm.
• A stencil to draw 1" diameter holes.
• Pen to mark over plastic and metal.
• Hole punch to pierce the main bar end caps. The hole size is like that for paper in binders.
• Scissors to cut bungee line, static line.
• Lighter to seal the ends of the cut bungee line, static line.
• Dozen sheet of paper towels, when chemically polishing the tube outer surface.
• Optional: A workbench vise with soft jaws to help you hold the first bar while assembling it.

Procedure. Follow these steps:

Please...	Please make a donation, to reward the ridiculous amount of time I spent designing and testing this product. My goal was to demonstrate that a better speedbar is possible, but it would feel good to have your encouragement. It will also motivate me to find ways to reduce fabrication cost for those purchasing a pre-built unit, and make this innovation more accessible to all pilots.
	Note your start time.
	1st bar: Cut to 25.0 cm. Remove sharpness of ID edge mostly (for easy insertion of "snap-in bushing" later), only removing shards for the OD edges.
	Main bar: Cut to 28.0 cm. Remove sharpness of ID and OD edges.
	Polish the bars using a de-oxydant made for Aluminum like "Blue Magic - Liquid metal polish". It does a great job on the otherwise typically dull 2024-T4, but produces a messy black residue which needs to be wiped off until the chemical reaction stops.
	1st bar: Prepare end "snap-in bushing", removing the "grips" that normally hold it into a thin plate hole. This will allow to pass a line through the opened space. Also, shave the raised lettering on the surface of the "snap-in bushing" where it contacts the fin.
	1st bar: At both ends, drill 5/32" holes through both sides, at 3 mm hole edge distance from the bar ends (or 5 mm from hole center from bar end). Remove sharpness of holes edges (outside and inside of the bar). The hole axis should be parallel for both bar ends (for the same line entry angle).
	1st bar: Insert both "snap-in bushing", aligning the openings with the bar holes.
	Fins (2): Follow the plan (try printing at 28.5% of size), to : Cutout the shape for each fin. Smooth all outer edges, using a file. Mark holes, drill with the appropriate bit diameter size (3 different sizes). For Europe, holes sizes must be adapted. Remove sharpness of edges (both sides), mainly where the bungee line needs to pass.
	Fin Counterweights. Cut the Nylon bolts such that they will not protrude the outside of the female parts of an Aluminum "post with screw" when 2 washers and the fin are held by them. Weight: For each fin, the sum of parts for the counterweight is 9 g (0.32 oz) ideally, with 7 g (0.25 oz) as a minimum. When the assembly of the first step is completed, verify that the bottom edge of the fins is horizontal when the first step is suspended.
	Fin Counterweights. Assemble for each fin, using for each one 2 washers. Use the Nylon head on the side of the fin which will contact the bar, the Aluminum head on the outside.
	Fins (2): Use the 1/8" bungee line to compress the fins agains the bar ends, making a square knot in the line that gets sent inside the bar, by passing it through the "snap-in bushing" ID at one end. Don't make this ultra tight, make sure you can pull one fin away by 5-6 cm. Otherwise there would be a higher (unnecessary) bending load on the fins when folded. Only a light compression is needed in flight.
	Main bar: 1) On one side (towards the 1st bar), for both ends, make 5/32" diameter hole at 5 mm from the bar end to the hole center. Note: This provides a 27.0 cm spacing for the lines going to the first bar. The ideal spacing allows for a linear width increase from the first bar: 24 cm at 0 cm distance from first step bar, 25 cm [25.0 (1st bar length) + 2x0.15 (flange heads) - 2x0.15 (cord radius)] at 6.34 cm (variable C in "Dimension Optimization" worksheet), 27.17 cm (obtained by linear width increased) at 20.10 cm [22.0 (ideal step spacing) - 0.75x2.54 (main bar diameter)] 2) On the other side (towards harness), for both ends, make 13/64" diameter hole at 6 mm from the bar end to the hole center (or 3 mm margin between the hole edge and the bar end). 3) Remove sharpness of all holes edges (outside and inside of the bar).
	Main bar: Connection loops. Cut two 14 cm lengths of 3 mm static line. Make 2 knots in them with 5.0 cm spacing after being under tension: about 25 kg (55 lb). Seal ends with a flame. Using a thin cord, pull center (between knots made) through the remaining bar holes, from the inside out.
	Bar connection lines. Cut two 35 cm lengths of the 3 mm static line, and make a tight knot near one end of each. Seal ends with a flame. Load those knots by pulling about 20 kg (50 lb) on the line. Insert the long end of the lines from within the main bar, and outside the holes on the side where they are closest (towards the first bar).
	Main bar: End caps. Using a paper hole punch, make holes to allow for the passage of the connection loops and lines going to the first bar. Thread the connection loop and lines through the holes, and slip the caps on.
	Bar connection lines. Pass loose end through the first bar holes, and thread between the bungee lines. BTW, this is what prevents the fins from freely rotating, when not in flight. Make knots in the line, under the bar, so that bar spacing is 22 cm (the remaining loose knot will render about 15 mm when tightened by stretching the line by the bars). Bar spacing is measured between where your feet make contact on the first and main bars. Tighen all knots, verify bar spacing. Cut excess line length under the first bar, seal with a flame. Note: 22 cm bar spacing (distance between foot contacts) is judged a minimum to allow easy grabbing of the first step, while still providing significant first step acceleration: 1/3 accelerator travel for a wing with 33 cm travel.
	Fins: Use the small (blue) cable ties to secure the passage of the line at the top of the fin. Put the cable tie head on the inside of the rearmost hole (behind line). Close the cable tie snug, but do not tighten so the line cannot slip. Cut excess length of cable tie.
	You're done. Verify that the bottom edge of the fins is horizontal, and that the first step bar axis is 4 cm forward of the vertical lines under the main bar. Note how much time the fabrication took you, and let me know.

Proceed to the Installation. Send me a picture of your creation, I would like to see it.

Installation.

	The J-Rod is designed to rely on a Retraction system. It would be a shame to have you step on your new equipment while launching/landing. If you harness is not already equiped with retraction bungee lines, you can add them yourself. Verify the elastic lines will allow for a 40 cm extension.
	The ideal accelerator line length is achieved when your riser pulley start contacting when your legs are fully extended with your feet on the main bar. More info: Accelerator Adjustment.
	The ideal retractor bungee line length is such that the main bar retracts to the front edge of your harness seat.
	Bowline. The bowline forms a secure loop that will not jam and is easy to tie and untie (even after being loaded). The "Option" in the image, is for stiff lines submitted to shocks which could loosen the knot, but you can use it as an extra safety for this application after your length adjustment is finalized.

Other Ideas / Main bar with built-in retraction system.

2005/6/23. From the inside view, one can see the elastic bungee line going around the internal end rollers then exit through the side hole. Internally, along the length of the bar, the bungee line goes back and forth as a single line (facilitates replacement if ever needed). The threading of the elastic bungee line is such that it rotates in the same direction on the roller to reduce line-to-line friction there. I used one for about 20 hours (then got a harness with built-in retraction system). 2 have been sold (I keep in contact and feedback is good). Although I believe that the burden of the retraction system should be inside the harness, having the retraction inside the main bar provides an option until most harnesses provide this utility. Aside from the obvious advantages during launching and landing (having bars always retracted, even after use) I hear that speedbars without a retraction system provide the risk of getting locked on the rear of the harness following a frontal collapse and remaining activated during recovery.

2005/7/25. I prefer a rigid bar as the first step myself, but this is a conceptual design, combining a self-retracting main bar, and a cable loop as a 1st step. The 3 images are a graphic representation of the concept. Colors: Red is steel cable. Yellow are the cable crimps (ferrules). Green is the elastic cord. White/gray are the sliding surfaces for the elastic cord. Note that images do not show: Plastic tube covering the 1st step loop. Shrink-wrap over the furrules (what crimps the steel cable). How the top elastic line guide is secured to the top of the cable. The main tube end caps. The design achieves the desired functionality: Loop as the first step. 1st step easy to grab from trim speed. 1st step easy to grab from using the last step. Self-retracting. Easy to manufacture (less hole drilling). No bolts (avoids the home-made look). Its components are from proven designs: Self-retracting internal bungee has worked well for me for about 20 hours airtime. Cable setup is already in commercial use. Examples: Sup'Air, Gin Gliders. For this design the top cable does not need to be as long as the Sup'Air and Gin Gliders version, since the extra weight of this main bar will compensate to balance the weight from the first step with less length. The novel idea is to combine the two, and use the cable inside the main bar as the axis for the elastic cord (bungee) roller (does not need to turn when made of Nylon).

Other Ideas / First step with 3 fingers.

This bar has been strength tested, applying my full weight of 175 lb (more than double the real life load, due to accelerator line pullies and riser tension distribution) at the center of the bar with a single foot. There is a hole in the center of this bar, but it is strategically placed on the neutral axis (where the material is neither in tension or compression).

Open issues (highest priority first):

1. Add bar end padding for the event of the bar getting caught between legs while running. On 2005/10/31, I chamfered the edge of bar tube end which were still semi-sharp before. Tried "chair leg cap" plugs but it looked dorky and did not help much. This will remain an issue, and any bar can hurt if caught between the legs, unless a significant contact surface is provided (large disk or 90° bent tube).
2. Complex: One can either like or dislike the appearance of this design, but it remains somewhat complex to fabricate.
3. Cable sticking in the end finger passage loop: 3 sources to the problem: Loop diameter too small, loop with plastic tube has a friction coefficient too high, edge of Nylon tube end is too sharp. On 2005/10/31, I chamfered the edge of the Nylon tube end (that helped), installed 10 mm metal rings with a split (until I can find ones without a split).
4. Have a more esthetic counterweight at the end of the middle finger. Solution: Considering collar clamps with 3/8" ID. Needs to weigh about 2 oz (60 g).

In flight.

	2005/10/29. Relaxed flying at trim. Lower legs hanging with no effort. There is a light contact between the 1st step bar and the leg (not annoying).
	2005/10/29. Bringing forward my feet, so the 1st step hangs freely. 1st step bar is forward of its hand point by 4cm. Ignore the small quick-link between the main bar and the 1st step bar, it is only for me to quickly detatch the 1st step for more prototyping work. In its final state, the line from the first step will directly attach itself to the short loop (hidden in this picture) under the main bar.
	2005/10/29. Reaching for the 1st step by lifting one foot and bringing it down vertically. In this picture, the angle in the line between the bars show no pressure is yet applied, and that the bar naturally locates itself under the foot (the main goal).
	2005/10/29. Foot having found the first step. Light pressure appied (straight cord line between the bars). Notice the opening angle in the vertical finger to bar interface, confirming that the 1st step bar line hole is now aligned with the load path and this will allow the middle finger bar hole to be in the bending neutral axis, making that hole near stress-free at the bar center.
	2005/10/29. Fully extending the 1st step. Ignore the appearance of the end of the middle finger with a collection of dead weights wrapped with beige marking tape, a more esthetic dead weight will replace it. Getting the 2nd foot on the 1st step is easy. The camming effect of the main bar is not annoying partially thanks to its large diameter. Transitioning to the main bar is easy.

Development pictures

	Older design. Since then, the rear-facing middle finger lays horizontal to optimize its leverage. 2005/10/23. In comparison to the System X (obsolete, but now available as the AIM speed bar). The system X had its first step about 2.5 cm forward from the vertical drop point. The J-Rod design is currently set at 4 cm forward. Ignore the clumsy weights added to the end of the center finger (work in progress). Both designs use a rear balancing weight, but this one can better leverage that "utility" rear weight.
	2005/10/25. General picture of the first step mechanism. Ignore the clumsy weights added to the end of the center finger (work in progress). Total mass is 0.14 kg (5 oz), including the dead weights (2 quick-links) shown in this picture. This design has the middle finger under more than double compression of the end fingers, to match the torque induced by the 2 end fingers, and the center finger extra leverage (33% longer). The side view shows the middle finger near horizontal, using its length for maximum leverage of the rear weight. 1st step bar is 4 cm forward of the vertical drop point. By comparison, the AIM speed bar is only forward by 2.5 cm. In-flight and ground handling testing will soon reveal if 4 cm is too much, in which case the length of all the fingers can easily be scaled back, and the rear dead weight could be further reduced.
	Older design. Now the load lines hole are offset 30° from the fingers faces. 2005/10/23. One of the vertical fingers of the first step bar. It is made of a series of plastic tubes kept compressed by an internal bungee cord, which is doubled to also help alignement. Not sure how the small O-ring will stand up to the constant pull of the doubled bungee running inside the plastic tubes. I'm just concerned with rubber becoming brittle over time, so I will look for alternate maerials.
	2005/10/25. The holes for the main line connecting the bars is set at 90° from the middle finger hole so that one remains in the bending moment neutral axis (almost stress-free). Once load is applied the end fingers re-align with the load line and we observe the pictured gap at the finger/tube interface.
	2005/10/25. Fingers collapsed (low DHV recovery I promise) into a near 1-dimensional space. Very low storage bulk, and unbreakable since it easily bends!
	Older design. Now the load lines hole are offset 30° from the fingers faces. 2005/10/23. Detail of the first step bar and finger interface at the end. A special deformation tool allowed to create a flat face, while avoiding ovalisation of the tube. For all finger interfaces: When bent at the bar, the internal elastic bungee cords slip out of the Nylon tubes, not from the metal bar. This way, the is less friction against the metal hole. The Nylon tube inner hole is less abrasive, and will prolong the life of the elastic bungee cords.
	2005/10/23. This is the tool that allows to press-deform a flat face onto the bar, while maintaining the round shape on the opposite side of the tube and avoid ovalisation. Bar deformation is controlled by a large vise. I spent a ridiculous amount of time designing this tool which now looks so simple.

Fatigue test

2005/10/27 The picture captures the appearance of the joint after being submitted to 1000 maximum flex/collapse motions (did it while watching TV), all in the same bending direction (worst case for localised wear on the Nylon tube). The 1000 cycle test represents the use of a recreational pilot (2 storage folds per week) over 10 years. I was initially concerned (2005/10/26) with the sharp outer diameter edge of the tube loosing its sharpness after a few bending motions. The edge of the tube being slid under under load across the Aluminum flat face, and passage over the edge of the metal hole seemed abrasive. But after the edge starts getting a small radius, the process seems to stabilize after about 200 cycles, not showing significant more abrasion after 1000 cycles. Performing the test on the middle finger wich is more compressed by its internal bungee cords, was also a worst case scenario. 2005/10/27. General: Detail of the first step bar and finger interface at the center. A special deformation tool allowed to create a flat face, while avoiding ovalisation of the tube. Although maximum bending is at the center of the bar, the hole is on the neutral axis (where the tension and compression stress and balanced). Wearing a shoe, I can put my whole weight (80 kg, 175 lb) on the center of this bar, having this hole in the neutral axis (determined by the structural hole position at the ends of the bar).

Other Ideas / General.

	2005/6/11. The tongue on the main bar would lift the first bar (not just a cable loop) as the first and main bars where connected by springy piano wire. The tongue's angle was a friction fit, so it could be rotated for storage. Apco's Wonder Bar is another twist on the same tongue concept. A couple things I disliked (I tested in flight) about a tongue: 2D object for storage (not a big deal). One could launch with the tongue over the front edge of the harness. Just need to be re-positioned in flight. If tongue can not be rotated, then it creates extra bulk for storage, and there is the risk of the tongue getting broken (not so bad if semi-rigid). About the semi-rigid link between the bars, I dislike it as it is still vulnerable to storage abuse. Those piano wires, although flexible can be bent near the rigid bars. And you still have to deal with a 2D shape for storage (fit in inside harness?).
	2005/6/11. I thought the idea of having the elastic bungee cord leaving the end at any angle would be good. It is not a bad idea but adds complexity to the fabrication, and the tool to make that nice inner radius costed 75$ (anybody needs it? I will sell cheap). 2005/6/18. The 3rd and 4th picture are in-flight testing of the ease to grab a vertically dangling bar. Notice that it is not being pushed back much by the airflow and rests behind the heals. About 20 hours of flying with a simple straight bar hanging vertically, allowed me to conclude there is a 75% chance to grabe the bar on the first try with one foot. Not too bad, and the worst case is that you will most likely get it on the second try. Once can also hit the bar backwards and catch it on the forward swing (is this acro?).
	2005/6/12. Cable connection between the bars. I thought of using thimbles for efficient cable connections. They look ugly.
	2005/6/19. I considered a cable stop and a simple ovalisation deformation on it. I know that a special tool is need for a proper swaging application: Swage-It, Nicopress. Just simple pinching of the cable stop proved that the special tool would be required as a good pull was able to dislodge it. Regardless, I prefer to avoid steel cables which can end up bent at a bar hole under storage.
	2005/6/23. One way to cap the 1st step bar. The rubber cap material makes it possible to remove it and adjust the X-lock line threading pattern to adjust the spacing between the bars, and it also prevents the line from slipping in the X-lock when no tension is in the line.
	2005/6/23. The "X-lock", here first used on a main bar with built-in retraction system. It is a novel way to attach the acelerator line to the main bar without loosing line length for external knots (image sequence is from left to right, then onto the next row). This "X-lock" pattern has 3 advantages: Near-zero line consumption for external knots. Good when line slack is marginal (wings with big line travel and harness with long seat). Inside the bar, where the line first makes its high-tension bend, it does so on itself which reduces friction against metal edges. Can easily be loosened and adjusted for length, even after being unter high tension. No tight knots to undo! The big "access" hole on one side of the bar may not be there if a threading tool is chosen to be provided to facilitate initial threading of the speed line. I'm also considering just including pre-threaded lines you just need to attach to the riser's Brummel hooks.
	2005/7/17. 1st step forward displacement idea: A cable loop tongue allows to rotate forward a portion of the rope cable going down from the main bar. Either the loop tongue could use the harness to help it rotate (become harness shape dependant) or could be weighed at its rear-most point to use gravity (soft cable become a problem). An idea with merit, but I prefer to avoid steel cables which can get deformed in storage.
	2005/7/17. 1st step forward displacement idea. Use of semi-rigid cables, where a weight (not shown here) would be at the rear center of the loops and force forward by gravity the 1st step bar. This idea later put me on the path of the "finger" bar.
	2005/7/19. A small diameter piano wire runs along the length of the main bar and is held from rotation at its center, while its ends are bent to be aligned with a 1st step cable loop. I don't like cable loops as the 1st step, but wanted to explore the idea. The angle of the small diameter torsion rod is difficult to set, and should be mechanically controlled by stoppers at the start of the cable loop. The torsion rod, is vulnerable to deformation during storage.
	2005/10/19. Metal Epoxy to shape the surface of an Aluminum tube to create raised "flat spots". I used Loctite Epoxy for metals, and after roughing an Aluminum tube and doing a proper application with overnight cure, the rigid epoxy should be machined into a flat face. But using a rigid blade, I could flake off portions of the raised flat spot. Fear that long-time use of Exoxy on Aluminum would be unstable, I abandon this idea.
	2005/10/21. I tried finding a 5/8" square tube of aluminum with soft corners as the diagram show. Someone called it "unobtainium". I found stainless steel in this shape, did the math to see if it would be load-resistant enough and purchase a length. But the Stainless Steel tube was too heavy. The goal was to use the square shape for the "finger" bar idea so there would be no need to create flat spots at 90°. But I have found out since, that the angle between the flat spot to the fingers should not be at right angles. So no need for square tubes.
	2005/10/30. Loop used to attach the line coming from the 1st bar. The line from the first bar will use a Non-slip loop knot on this loop. The quick-link in this picture is just for my personal testing allowing for quick disconnection. Inside the bar, the loop is held by 2 knots (one for each side) plus an extra set of backup knots. All these knots have been pre-tensioned, so this loop with not lengthen under load.
	2005/10/30. Stuff the end of the line inside the bar, and plug the bar end with the end cap. Ignore the patch of duct tape covering an unnecessary test hole. Also, the small white cable tie used to crimp the elastic bugee cord, may not be final.
	2005/11/1. Early prototype. 1st step bar is balanced 4 cm forward from its hang point, by a counterweight at the end of the fins (blue). A simple solution was found to prevent the fins to rotate about the bar's axis: A knot is added after the loop holding the bar connection cord, limiting the amount of cord which can be rolled around the bar. The fins are held perpendicular to the bar, by a light tension from an elastic bungee inside the length of the bar. The width of the bungee loop holding the fin, alows it to auto-center itself with the bar's inside diameter. To prevent abrasion of the fin from the Aluminum bar, a washer is placed in between. I am considering adding Nylon "snap-in bushing"s (I have seen those at my favorite hardware store) to reduce friction during fin collapse, of the elastic bungee at inside edge of the bar ends. The washers used for counterweight are just an initial idea (although not a bad idea). This design is much easier to fabricate than the First step with 3 fingers and does not require to make a hole or deform the center of the bar (stronger). Over-designed for strength, there is room for weight reduction, and effect would be doubled by a matching reduction of counterweights. The current design only weighs 9 oz (250 g) including counterweights.
	2005/11/1. Early prototype. Detail of an end fin. I just cutout the shapes from a rigid plastic clipboard. Not sure if this is the ideal material, althouth not a bad choice at the moment: Very light for its rigidity (need to be cut with a hacksaw), and does not shatter. These end fins also serve a protection purpose: Cut with a larger radius than the metal bar, it offers a greater contact area in the event of leg contact when pinching the bar between the legs while running. This is better than having a rubber cap at the bar ends. These fins have a low frontal area, not contributing to significant drag. The elastic bungees cords holding the finds perpendicular, do not have to counteract the weight of a cantilever part, as was the case with the First step with 3 fingers, but only to stabilise the fins. I can see a cool logo go on these fins. Maybe the final design will have a cutout to reduce fin mass (although already light).
	2005/11/1. Early prototype. View of the collapsed fins, for storage purposes. By laying the main bar next to this bar, we have a compact package for storage which should be resistant to handling abuse. The elastic bungee cord holding the fins has extra extension margin. I may use a stronger bunge cord in the next iteration, although this one seems acceptable.
	2005/12/8. Shape B + Blue clipboard plastic (0.133" thick). Good: End bar leg protection: Sufficient. Creep: Non-issue: No apparent deformation when fin is folded. Bad: Shape no good: Too narrow near the bar, in the even of leg impact loads. Concave edges focus deformations. Narrower shape increases effect of folded fin creep.
	2005/12/7. Shape B + White translucid binder plastic (0.080" thick). Good: End bar leg protection: Sufficient. Bad: Shape no good: Too narrow near the bar, in the even of leg impact loads. Concave edges focus deformations. Narrower shape increases effect of folded fin creep. Notice the change of plane in the picture.
	2005/12/14. Accelerator line X-Lock + Bungee loop is locked inside by accelerator line. See comparison study in: Main bar interface with harness lines. The blue line connects the main bar to the first step bar. The black line is loop of elastic bungee of 1/8" (about 3 mm) used to retract the main bar to the harness. A tape was used to illustrate that a loop must be made at end end of the line. It is the responsibility of the pilot to decide how this loop is achieved: I recommend not doing a knot which will be hard to undo, instead consider a series of cable ties (which can be cut and replaced). The red line is the accelerator line going to the risers. In this case, it is at the maximum diameter of 4 mm (3 mm recommended). The black cap, with 2 holes, is used for: Leg and equipment protection, dust cap, accelerator line X-Lock consolidator (so it cannot slip when unloaded). 1) Thread the red accelerator line through the upper black cap hole. 2) Thread the black bungee line loop through the lower black cap hole. The black bungee line loop will have to later thread through the largest bar hole. 3) Thread the red accelerator line through the smallest of the 2 ajoining holes, then out the X-Lock (patter of 4 holes) hole closest to the bar end. 4) Thread the red accelerator line back into the bar using the furthest X-Lock hole, and out one another X-Lock hole. 5) Pass underneath the first bend, which will avoid the most loaded part of the line to rub against the edges of the metal holes. 6) Thread the red accelerator line back into the bar through the remaining X-Lock hole, and out the end. 7) Thread the black bungee line loop through the last (and largest) hole into the bar. 8) Lock the black bungee line loop by passing through it, the red accelerator line. 9) Tighten the red accelerator line on its X-Lock and send the excess line into the middle of the bar. 10) Pull tight (towards the outside) the black bungee line loop. 11) Slip the black cap onto the bar end, making sure to cover the lines looping in the X-Lock, which will prevent slipage when the line is unloaded.
	2005/12/26. Accelerator line X-Lock + Bungee loop is locked inside by accelerator line square knot. See comparison study in: Main bar interface with harness lines. The red line connects the main bar to the first step bar. The black line is loop of elastic bungee of 1/8" (about 3 mm) used to retract the main bar to the harness. A Bowline is used to create a loop at end end of the line. The blue line is the accelerator line going to the risers. In this case, it has a diameter of 3 mm (recommended). The black cap, with 2 holes, is used for: Leg and equipment protection, dust cap, accelerator line X-Lock consolidator (so it cannot slip when unloaded). Construction notes: Hole pattern (drawn on masking tape) for side with 5 holes: All 5/32" dia holes, aligned holes centers are 5, 12.5, 20 mm from bar edge, pair of holes centers at 8.75 mm from bar edge are 12 mm centers apart. On other side, one of the hole (for accelerator line) is a continuation of the one on opposite side closest to edge. The other hole (for bungee loop) is 13/64" diameter (the only one of that diameter on this bar), and made at a 45° angle with same hole edge distance from bar edge as the adjoining hole. 1) Thread the blue accelerator line through the upper black cap hole, the through the smallest of the 2 ajoining holes, then out the X-Lock (patter of 4 holes) hole closest to the bar end. 2) Thread the blue accelerator line back into the bar using the furthest X-Lock hole, and out one another X-Lock hole. Pass underneath the first bend, which will avoid the most loaded part of the line to rub against the edges of the metal holes. 3) Thread the blue accelerator line back into the bar through the remaining X-Lock hole, and out the end. 4) Thread the black bungee line loop through the lower black cap hole, then through the last (and largest) hole into the bar. 5) Lock the black bungee line loop by passing through it, the blue accelerator line, forming a square knot. It is important to create a square knot so we do not rely on the hole edge friction to block the line from exiting the bar, which would accelerated the wear on the bungee sheathing. 6) Tighten the black bungee line loop square knot with the blue accelerator line and pull it to its final location. 7) Tighten the blue accelerator line on its X-Lock and send the excess line into the middle of the bar. Slip the black cap onto the bar end, making sure to cover the lines looping in the X-Lock, which will prevent slipage when the line is unloaded.

Blog.

2005/2/15	Around this date, I starting designing main bars with self-retraction system, as the harness I had at the time, had no built-in speedbar retraction system.
2005/5/1	Now having a harness with built-in speedbar retraction system and in need of a new speedbar, I started focussing on a better 2-step speedbar with easy foot-grab of the 1st step. Discussion on ParaglidingForum.
2005/10/24	First step with 3 fingers: The longer single center finger can not support as much torque as the sum of the 2 end fingers. This is because it uses the same elastic tension inside it, and is disadvantaged by its longer length and lesser count (one finger matching the torque of 2).
2005/10/25	First step with 3 fingers: Good ideas... 1) Center finger angle. Center finger should not be at 90° of the end fingers, but more around 60°. That way, the center finger will have max leverage when the end fingers are rotated 30°. It would allow the length of the middle finger to be reduced about 13% [1-cos(30°)], or generate more usefull torque from the same dead weight. The bar's center hole can still be on the neutral axis (where there is no tension or compression as a result of a bending load) by setting the end holes for the cords going to the main bar, at a 90° angle from the center hole, or 30° ahead of the end fingers. 2) Increased finger compression. The end fingers use 2 strands of 1/8" (about 3 mm) elastic bungee cord, as did the center finger. I was successful in fitting 2 stands of 4 mm bungee cord, which also has a sheathing allowing for more extension (about +200% instead of +100%). When at about 90% of its maximum extended length, 2 cords of the 1/8" bungee have a total tension of 1.44 kg, while 2 cords of the 4 mm bunger generate 3.50 kg (more than double). So it is very feasible to increase the middle finger compression this way and the middle finger can be made to surpass the torque load of the 2 other end fingers. Another way is to pass 3 strands of the 1/8" bungee, but that would not increase the compression as much. 3) Increase middle finger diameter. Possible but would require re-tooling to deform a larger face of the aluminum tube at its center (not a good thing to do since that is a critical bending strength area). No need for this at this time, since increasing finger compression seems like an easier solution.
2005/10/25	First step with 3 fingers: Good progress. I did a new prototype of the first step finger bar, and it is mechanically near perfect. This one has the center finger at 60° from the end fingers, a boosted middle finger compression to match the torque capacite of the 2 others, and structural cable holes at 90° from the center hole (so it is in the bending neutral axis). And when it hangs, the middle finger is near horizontal, optimizing its leverage. Total mass is 0.14 kg (5 oz), including the dead weights (currently using a small and a large quick-link). Pictures of 1st step bar updated.
2005/10/26	First step with 3 fingers: Nylon tube outer edge in contact with the bar, is being shaved. To simulate usage, the middle finger (the one under most compression) hab been repeatedly flexed. The edge of the Nylon tube shows wear, and is not longer sharp. The main cause is that when this joint is bent the Nylon edge slipt towards and slightly into the Aluminum passage hole for the bungee cord, and when released the pastic edge is being shaved for the tube to return to is stable position. I need to establish a representative test for a recreational pilot, I'm thinking of a 1000 flex motions (2 re-packing per weekend over 10 years). Possible solutions (ranked by interest): Additional Nylon washer of slightly larger diameter (7/16") than the Nylon tube (3/8") so sliding will be Nylon against Nylon. Washer hole edge on the Nylon tube side would be smoothed so it would not shave the tube OD edge. The additional face contact may slightly increase free play, but it is unlikely as the finger is under significant compression. Current Aluminum flat face and hole edge reaming are rough. Both could be improved by using a 7/16" drill (Nylon tude is 3/8" OD) with self-taping tip to create a smoother face and radius into the hole. I just need to buy that size/type of srill but and test. Offer a set of replacable Nylon washer (same ID/OD at the Nylon tube), which would bend with the first tube segment. Washer would be split, so they could be easily swapped when the wear becomes an issue. Add a resistant end cap. But this shift the wear problem to the Aluminum tube. Conic interface - Nylon point. There would be an angle of conicity for which the Nylon tube OD edge would not contact the through-hole in the Aluminum tube. This will complicate fabrication to create the matching conic faces. The Aluminum tube would need to be further deformed inwards (so no to thing its wall) but that may lead to excessive deformation. I am also concerned about the increased bungee cord shearing motion as the interface would start promoting rotation slip. Conic interface - Aluminum point. The Nylon tube OD would be less likely to slip towards the Al hole, and would more likely hinge about a point on the Nylon tube OD edge. Less slipping would reduce the friction wear. This will significantly complicate fabrication to create the matching conic faces. I'm not currently equiped to solder on Aluminum, but I have found that 0.5" Copper tubing neatly fits the 5/8" OD of the Aluminum bar, and the Copper material can easily be soldered upon to generate the metal hump which then can be machined into a cone shape. Non-issue (2005/10/27). See Fatigue test. The middle finger's 4 mm bungee outer sheathing is loosing tension at the finger/bar interface, and is becoming vulnerable to pinching between the bar and first finger segment. Need to investigate why the sheathing is bunching up there. The other bungee (1/8" or 3mm) does not seem to do this for the end fingers. Possible solutions (ranked by interest): Change bungee cord material. Maybe 4 strands of the better 1/8" bungee can be used instead of these two 4 mm. Nylon tube ID can easily be increased by reaming if needed. Use static cord + compression spring for the middle finger. Added weight would contributed to the needed rear dead weight anyway. This will require time to identify the appropriate parts. Avoid the center finger (replace with 2 end fingers) less compressed. This would hurt my sense of esthetics. Non-issue (2005/10/27). After doing the 1000 cycle test with the initial design, the outer sheathing seems to have balanced its tension. I am now thinking that the proximity of internal knots had induced bending in the bungee and unloaded sides of its sheathing. Under repeated use, the tension in the sheathing would have re-distributed. Inadequate rubber O-ring cord guides. As anticipated the small O-rings used as cord guides on the end fingers are inedequate. The soft rubber allows them to creep into the hole of the Nylon tube, from the pull of the elastic bungee. Possible solutions (ranked by interest): Small diameter slotted ring. Small diameter crimped ring (like a chain link). Hard plastic O-ring. Closed O-rings make the finger's Bungee cord harder to assemble. Solution (2005/10/28): Replaced by a small cable tie and protective flexible tube to both prevent the acble tie from further shortening and protect the load cable slipping through it.
2005/10/28	Main Bar: Good progress. Had good ideas to make a main bar that is simple to build, offers easy connection to the harness retraction bungee cord, and allows easy threading an accelerator line length adjustment.
2005/10/29	First step with 3 fingers: First flight: Observations: Ease to find/grap the 1st step bar in flight: Easy! 95% chance of grabbing the 1st step on each try (did about 24 tries). It makes it convenient to use the bar, even when you know you only need for a very short period of time (like a sink zone). Connecting the main bar to the harness and accelerator line. Did that last night, was simple, no tension knots required (easy to undo or adjust). More pictures/info on the main bar later, to show its features. Catching the 1st step bar between legs while running. I did 4 launches, 3 top landings and one landing with an unuasual amount of running time to then drop the wing where I wanted in the folding area (cool thing to do). I don't know when it happened, but at the end of the day, I noticed symmetrical brusing (same height spot on both legs) on my lower legs, indicating that I piched the end of the first bar between them at one point. At the moment, there is almost no bar end protection: Just a tube hole filler plug which does not cover the hard/sharp end edges. I will increase the level of padding at the ends of the 1st step bar. Normal flight. The J-Rod is discrete while flying at trim. Insignificant pressure on the calves from the 1st step, and the main bar automatically locates itself under the forward edge of the seat, and you don't feel it during launch or in flight. Foot caught between both bars in flight. After my first use of the main bar, I ended with one foot between both bars after release. I think it is because I let the main bar snap-back and the 1st step looped during the jerk back. I used the main bar about 8 times after, and it did not happen again. Noted here for diligent reporting, but I don't see this as a problem, and in the worst case, it was easy to dislodge foot using just one hand. Vertical finger cable passage loop. On one occasion (on the ground), I noticed the cable betwen the bars was restrained by the passage loop at the end of one vertical finger, which kept the finger bent. It easily released, but I will slightly increased the diameter of that loop. Retraction sytem bungee cord end loop. I had quickly set a cable tie to form a loop in the bungee cord. But it still allowed the loop to tighten on itself (I prefer it not to). I will find a better way to make a solid (yet easy to undo) loop in elastic bungee cord. Accelerator line slack. Soon after launch I wanted to verify that the accelerator system was not engaged. I was surprised by the amount of slack in the accelerator line. Before I had about 4 cm, but observed about 10 cm. Thinking my initial adjustment for having pulley contact with legs extended on the main bar was wrong, I fully extended the main bar and observed the adjustment was correct. The reason comes from the fact that I changed from the Sup'Air speed bar which consumed a lot of slack from the steel cables above its main bar. The J-Rod's main bar design has zero slack consumption as the line enters the bar without prior knots or stoppers. It is nice to increase the slack margin. The worst case scenario comes from wing with large accelerator travel, combined with a harness having a long seat board. Accelerated flight: 1st bar. I had some low-level concern about the camming effect: The pressure on the calves of the main bar when legs extended on the 1st bar. Fully extending the first bar about 12 times in flight (1/3 acceleration range), revealed insignificant inconvenience. The large diameter main bar only had a comfortable push on the calves. A non-issue. Bar spacing. I had pre-set a distance of 22 cm (2/3 of the Nova/Tattoo C accelerator range) in order to be 1/3 accelerated when fully extending the 1st step bar. The 1/3 acceleration was visually confirmed by riser pully relative displacement. Although the spacing cn be made shorted between the bars, it would increase the difficulty to raise the foot enough to grab the 1st step. 1/3 acceleration is a good compromise. If you are in the market for speedbars, beware of larger bar spacing which may render the first step almost useless towards an airspeed increase, and this effect is increased as your wing's accelerator line travel is shorter: Do the math!
2005/11/1	First step - "End fins" concept. I will prototype a different approach to achieve the same goal of balancing the 1st step forward. A simple bar with ends used by vertices of soft triangular fins, used to balance the bar forward. The soft fins would collapse onto the bar for storage. This could be much simpler than the "finger" bar, and simultaneously create bar end padding in case of leg contact.
2005/11/2	Proof of concept (rough prototype) done for the First step - "End fins" concept. Purchased more parts today, to make a better prototype. Excel spreadsheet referenced in the Market Comparison has been updated.
2005/11/4	Chose a new line material for connecting the 1st step to the main bar. The new line has more abrasion resistance (thicker sheathing), no sheathing slippage issue, and has a safety facor of about 7: Line can support about 200 lb tension with knots (400 lb rating), and line only need to support about 30 lb (half of about a third the pilot's weight).
2005/11/4	Ready-for-flight prototype of the "End fins" concept. 1st bar is 4 cm forward of hang points. Mass of 0.32 kg (11.3 oz), including both bars and 1st step counterweights.
2005/11/5	Favored 1st step concept: "End fins". Preferred over the previous First step with 3 fingers.
2005/11/6	Creation of a decision matrix (Excel spreadsheet) to find the best way to connect the line from to the main bar onto the 1st step's bar.
2005/11/7	Document revisions, and setting a clear path of remaining action items.
2005/11/9	With the use of a Decision matrix (Excel spreadsheet), the best way to connect the line from to the main bar onto the 1st step's bar was found: The "Simple_InOut_2" concept (picture).
2005/11/11	With the use of a Decision matrix (Excel spreadsheet) the best way to compress/center the end fins onto the bar ends was found: The "SingleBungee_OutInFin" concept (schematic drawing).
2005/11/13	First Step: First flight: Using an early prototype (does not have the optimal load line connection knot, the final bungee knot configuration, or the optimized fin shape), a very encouraging day: Ease to find/grap the 1st step bar in flight: Easy! 100% chance of grabbing the 1st step on each try (did about 10 tries). Catching the 1st step bar between legs while running. I did 2 launches/landings. The bar did not interfere (I forgot it was there). At some point in the future, the 1st step bar will probably get caught between my legs, and I will report then how the fins did their job at protecting the legs from their large contact area. Normal flight. The J-Rod is discrete while flying at trim. I forgot about it during my flight when I was focused on thermalling. Accelerated flight: 1st bar. I used this amount of speedbar to clear a sink zone. No issues to report. Easy to put 2nd foot on the first step. Storage. The fins are easy to fold and return to their in-flight configuration after unpacking. No damage observed on the fins from being in use, storage or transport.
2005/11/15	Considering locally available materials. Creation of a spreadsheet to compare materials and tube sections: Bar Material Selection (Excel spreadsheet).
2005/11/16	Doing a test on currently used Aluminum tube reveiled a 293 MPa stress yield limit. Not bad considering the highest values (7075 alloys) are around 500 MPa. My guess is that the tubes I have now are 6061-T6 Aluminum, rated at 275 MPa (typical).
2005/11/16	Based on Bar Material Selection (Excel spreadsheet), if I were to switch to a 7075 alloy, I could save about 30% of the total weight (considering the 1st bar counterweight reduction). This seems worthwile, so I will try to find a supplier.
2005/11/17	Rejecting composite tubes. I was considering fiberglass (and composites in general) tubes (Max-Gain), but I do not like the thought of machining holes to accomodate the design (4 holes in first step bar, 10 in the main) and how those holes will withstand the lines trying to pry them open to pull a knot through, just where the material has been weakened from the machining operations (damaged fibers and matrix). A different approach to line connections and considerable re-design would be required. Also, machining composite materials is a dirty job (I have a background in composites).
2005/11/17	I found suppliers ( American International Metals + Metal Express) for 7075 Aluminum tube in these sizes: 1/2" and 3/4" OD, 0.035" wall. But the minimum order is about 400 $ to account for the minimum 12' ordering lengths. Expensive just for getting a few feet for building a prototype, but OK later if I use all the purchased lengths for production. The price of 7075 Aluminum tube (about 25$ worth for first+main bars in each set) should not be a deterrant in comparison to the price of workmanships to build the bars, and may contribute to a "coolness" factor when feeling the super-light bars. Weight savings. I updated the Bar Material Selection (Excel spreadsheet) to see if those thinner wall thicknesses would be OK, and they would be: Safety factor of 3.0 for the first step (less critical if fails), 4.1 on the main bar. This could be the perfect material, I just need to decide on spending 400$ to build a better prototype using it, and having the extra material in stock for making more speedbars. I'm wondering if I should set an early-adopter pre-order price to help me get the ball rolling with optimized materials. I like the idea that 5.2 oz could be saved: 46 % of the total weight (from 11.3 to 6.1 oz). This is starting to compare well with other designs (example: 7.7 oz for System X).
2005/11/18	First bar material selection. I found a better compromise between safety factor, weight and cost: Bar Material Selection (Excel spreadsheet). The first step bar will be changed to 2024-T3 Aluminum, 0.5" OD, 0.065" wall. I expect a weight saving of 2 oz. I will need to re-design the Nylon end fitting and fabrication.
2005/11/19	Main bar material selection. I found a better compromise between safety factor, weight and cost: Bar Material Selection (Excel spreadsheet). The main bar will be changed to 2024-T3 Aluminum, 0.75" OD, 0.065" wall. I expect a weight saving of 0.9 oz.
2005/11/21	Main bar material. Got the new bar material: 3/4" OD, 0.065" wall, 2024-T3. Main bar end caps. I'm thinking that an external thin/soft cap (instead of an internal end plug), would serve double-purpose to secure the lines threaded through the X-Lock. Similar to what I had done in a past for a 1st step which had an X-Lock (Pictures: Cap OFF + Cap ON ).
2005/11/22	First bar material. I received the first bar material.
2005/11/23	Found missing parts. I found/purchased candidate Nylon parts for 1st bar ends, and end caps for the main bar (I have a choice of external and internal to try).
2005/11/24	Main bar length. Revised length is 27.5 cm, 10.5 cm less than before. For related information see Research and development. Bar Material Selection (Excel spreadsheet) was updated for the change.
2005/11/24	First step bar end "snap-in bushing". Using Nylon spacers (0.5" OD, .194" ID, 0.5" long) I sucessfully reduced the OD to 0.364" for all but a 2 mm remaining flange, so it slides into the Aluminum tube without play until its flange. I used a lathe cutting tool and my drill press to achieve this, using a machine head bolt (hex) with spacers holding the Nylon spacers during machining. The result is satisfying, and the Nylon ID allows to pass the 4 mm bungee (unloaded) easily.
2005/11/27	First step bar: Connections. I found a more satisfying solution to attach the load line, and secure the fins. More esthetic (no apparent bungee line knot), easier to fabricate (off-the-shelf "snap-in bushing" for bar end), and potentially stronger. Also, there would be no longer a need for a mid knot in the load line, to prevent the fin from rotating by compressing the fin.
2005/11/28	Anodized finish. I tested the scratch finish resistance of anodized Aluminum tubes. Not good: Scuff marks add up quickly, and deeper scratches are accentuated by the color contrast.
2005/11/28	Main bar material selection. I found a better compromise: Bar Material Selection (Excel spreadsheet). The main bar will be changed to 2024-T3 Aluminum, 0.75" OD, 0.049" wall. I expect an additional weight saving of 0.5 oz.
2005/11/29	Main bar material. I now have some 3/4" OD, 0.049" wall, 2024-T3 Aluminum tube.
2005/11/30	First step: Fin weight. I measured the exact weight of the clipboard panel material (3.57 kg/m2). In my early prototype, I used about 1/3 of a (22.5 x 31.75 cm) board, which results in 85 g (3.0 oz). That is a significant portion (45%) of the currently predicted total weight (7.0 oz). The fins will go on a diet as part of their re-design.
2005/12/2	First step: Fin math. Established the equations between the dimension variables. See Fin design. Selected dimensions: 4.0 cm forward first bar, with Theta = 35°.
2005/12/5	First step: Fin material. Purchased a few plastic materials in a quest to either replace, or be bonded to, the existing thick+rigid blue clipboard plastic (0.133" thick). Using "Krazy Glue" nothing would bond to each other, so either a different adhesive, or mechanical fasteners will allow to join them. One of the new materials (0.080" thick) is 60% of the thickness and seems rigid+compliant enough, so it could serve as a single material to make the fin.
2005/12/6	First step: Fin design. Established better design parameters: Fin design.
2005/12/7	First step: Fin design. Pictures added under Fin design.
2005/12/8	First step: Fin design: Upper line fixation. Two 3/32" holes, separated (center axis) by 4.5 mm, allow the passage of a 3/32" width cable tie (3" long, rated at 18 lb), to hold the line passage position. Load line slip is allowed with some friction.
2005/12/9	First step: Fin design: Revised planar parameters.
2005/12/10	First Almost-Ready prototype. Built a new prototype with all the latest design changes. Needed counterweight is established at 14 g (0.5 oz). Only need to finalize the counterweight type and fixation. Pictures taken (See First Step and Main Bar), as well as a movie of the fin deployment from their storage position (under First Step). Total weight is only 165 g (5.8 oz). This is better than my expectation. 2024-T3 Aluminum finish. Using "Blue Magic" Liquid Metal Polish makes the dull bars shine.
2005/12/12	1st step counterweight. Found a potential solution with Stainless Steel fender washers. New requirement: Avoid metal-metal contact of moving parts (bolt head <-> bar).
2005/12/13	1st step counterweight. Selected materials: Stainless Steel fender washers: 1" OD, 7/32" (nominal 3/16") ID, 0.045" thick. 2 washers for each fin. Main bar: Good idea: Use the excess accelerator line to lock the bungee loop, instead of its first passage through the bar, avoiding friction motion.
2005/12/14	1st step counterweight. I have found an excellent fixation method. Only plastic will contact the bar, and only one hole needs to be made in the fin. And it looks clean. Added a graphical explanation of why just having the first step a bit forward helps so much to grab it. Made an updated series of pictures for the main bar connections.
2005/12/15	1st step end fins. Added the planar shape dimension schematic: Image. Selected a counterweight fixation method ( Outside picture, Inside picture ), and updated the prototype. Design is done and I built a unit for myself A purchase Price has been set.
2005/12/17	Main bar. The Main bar interface with harness lines needs improvement. The bungee line from the harness was submitted to excessive wear. Until I find the ideal interface, I eliminated the bungee line abrasion by modifying my latest protype to have an external loop to attach the bungee line: Picture.
2005/12/18	Main bar. Selected a better Main bar interface with harness lines. Reduced Price thanks to less manufacturing time: Single hole instead of 5 for an X-Lock. Completion of the Build It Yourself and Installation instructions.
2005/12/19	Enhanced the Build It Yourself instructions. Providing more details on part suppliers in the USA and Europe.
2005/12/26	Although there is no design change, I documented an option: Accelerator line X-Lock + Bungee loop is locked inside by accelerator line square knot. Satisfaction is achieved when knowing all options have been explored.
2005/12/27	Minor improvement reflected in the Procedure to build a unit: The lines leaving the main bar (towards the first bar) are moved closer to the end of the main bar ends. This allows for a linear increase in the line separation between the bars, so the fins do not need to compensate for any side load. It wasn't a problem before, as the fins had enough compression load to over-compensate the small side load at the top of the fin, but we may as well make this design perfect.
2006/4/16	Feedback is a new section of this web page.
2006/10/27	End Fin template. Creation of a template (made from a plastic sheet) to easily sketch the contour of an End Fin and hole locations.
2006/11/24	First client: Richard Hammer. Delivery of the 1st unit.
2006/11/28	Testing tools to fabricate the fins. Thanks to Rob von Zabern for using his water-jet cutting machine, as it made an easy job of cutting the outer shape of the fins. Also, thanks to Don Mies for having me test cutting fins on his scroll saw, which proved it was not an appropriate tool (melts the fins).
2007/2/7	Second client: Mark Harrah.
2007/2/15	Real-life testing. 126 hours airtime with the 2005/12/18 version. So far so good: No sign of accelerated wear, good usage behavior. Abuse resistance: Speedbar was used many times to induce full-speedbar collapses during wing tests, which make it snap back against the harness. I stepped on it once or twice while setting up my gear. I banged it between my legs while running (first bar fins leg protection does work). Picture of April 15, 2006.
2007/2/16	No EBE here: I want to reassure everyone that the development of the J-Rod is not linked in any way to reverse Engineering of extra-terrestrial technology (reference).
2007/2/17	First step: Fin material: Lexan. 2 weeks ago, pilot Joe De Briyn showed me his self-built unit: Picture. He used and suggested using Lexan for the plastic fins, also giving me a sample I can test to destruction. I am starting to like Lexan. It's tough stuff and remains transparent until failure (no opaque whitening when bent). Common uses of Lexan: Aircraft canopies, windscreens and other windows. Household items: Bottles, compact discs, and DVDs. Bullet-resistant glass. At the movies: Featured on Star Trek IV and described as "transparent aluminum".
2007/2/19	Video of in-flight use. There is a new video added, showing an in-flight activation. See First step features.
2007/3/3	Feedback from James Bradley.