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Accelerator : System X / Speed Zone
by Jérôme Daoust. Created 2001/4/24, revised 2002/12/11.

I ordered mine from Snowdon Gliders in the UK since I could not find a local reseller in the USA.  With tax and shipping, it came to about 41 $US and I received it 6 days after placing the order.

 

The speedbar I received, differs slightly from the picture below.

  1. I have rivets (lighter) instead of bolts where the lower step meets the strap connecting it to the top bar.
  2. The plastic on the lower step is red (instead of black).

 

 

I set it up and added elastic lines running parallel to the lower accelerator lines (both pass through the lower pulley), so that the speedbar always remains close to the harness while kiting the wing or in flight.  This does not add significant tension to the accelerator lines, only about 2x the speedbar weight. In flight, there is about 2 inches (5 cm) of slack on the accelerator lines, and the bar is snug up to the harness, thanks to the elastic lines. It is very easy to put my foot into the lower (1st) step and I can keep looking ahead while doing so. Fully pushing the 1st step, picks up the initial slack of my accelerator lines and extends them such that the wing's airspeed rises to its best glide (with respect to ground) with a 20 km/h headwind.  Full range of acceleration is achieved with the 2nd step.

 

Concerns :

  1. The thin transparent plastic used on the straight top bar.  Maybe it will rip/split after intensive "2nd stage" speedbar usage.  But that seems to mainly serve an esthetic purpose.
    Update (2002/12/8) :  This has not been an issue, after about 200 hours of flying.
  2. During the summer of 2002, I noticed that the "U" step (1st bar) had been bent.  I don't know if this occurred during transport or launching/landing.  It has been un-bent a few time since (Picture of partially straightened "U" step, Detail).  But I'm afraid that the next time it may fracture due to metal fatigue (bending and unbending).  Note that bending instead of breaking, is a good thing.  A new one is on the way.
    I asked Snowdon Gliders about having a solid link between the “U” and straight bars instead of the webbing link.  Brad Nicholas replied with the following, which makes sense :

I created several prototypes, which do not have the webbing link but instead have a continuous loop of tube. The problem with this idea is that the camming effect, when one pushes on the lower step, forces the top step into the back of your leg behind the knee. Not only is this annoying and distracting but the smooth-running of the system is hampered by the top bar having to slide along the underside of leg/flying suit. By retaining the webbing link the pressure on the back of the leg is reduced and the overall operation is smoother.

Even with my original speedbar getting deformed after about 200 hours of flying, and in need of a replacement, the cost was 0.21 $/hour, making it a low cost accessory.

 

 

Conclusion

 

·        A step forward in speedbar design.  What I wanted is to perform the basics very well :  A two step speedbar system that activates without using the hands and is out of the way while my feet are still on the ground.  This has been achieved with an appealing simplicity.

·        I don't need a "stirrup".  Those things should remain in the equestrian world.  Also, many of those limit the range of action for the accelerator lines.

·        I don't care for a footrest.  I have no problem getting into my harness and I prefer to have my feet free to cross my legs in flight as a complement to weight shifting.

·        Update (2002/12/11) :  The design is a good compromise between cost, longevity and weight.  I would buy one again today if I had to.