> Learning to use a hi-start

http://www.rcsoaringdigest.com/pdfs/RCSD-2008/RCSD-2008-03.pdf Page 25

For a typical thermal glider launch, hook goes between 1/2 and 1/8" in front of the CG.  The closer to the CG the steeper the climb and typically the greater the height.  Steep climb at a moderate rate of speed.  The steeper the climb the more the stress on the wing, but with a properly sized hi-start gliders typically handle this quite well.

For a zip, usually the hook goes near the nose.  Plane goes really fast with little climb, as in the video.  When you come off the line you pull up and turn the speed into height.   A very sharp pull up can put a lot of stress on the wings.

Natuarlly you can go somewhere between depeding on your goals.  the key is the closer to the nose the more speed, less climb on the line.   Closer to the CG the steeper teh climb and the less the speed of the clim.

Put it 1/2 way and you will be somewhere between those two extremes.

On my winch launched contest gliders the hook is almost on the CG and can stand on the pedal. But my woodies can't take that. 

My less strong sport gliders might have it 1/4 to 3/8" in front of the CG and I don't push the winch as hard, or I use a hi-start.

I only use zip starts on my Zagi flying wing.  There the hook is about 2" back from the nose.


For typicaly HS launches from near the CG, for a 2M glider I would likely use 5/16" latex tubing that has 1/8" walls or something like that.  As covered in the article at the links above, you want 3-6X the weight of the glider in terms of pull for a typical hi-start launch.
 

(in reply to Art ARRO)

(in reply to aeajr)

(in reply to Art ARRO)

Videos on this page - around post 158.

(in reply to Art ARRO)

(in reply to aeajr)