Taken from [SAL glider] Digest 481 8th January 2003
Message: 8 Date: Wed, 08 Jan 2003 15:41:29 -0000
From: Phil
Barnes Subject: Re: Launch methods and height.
In SALglider@yahoogroups.com, "Peter Williams" wrote:
Lots of
interesting stuff lately for a scratch builder like me. Looks like I found the
true home of the scratch builder in this group. - Yipee!
At present in no wind I get 37m launches measured with my LoLo and talk of 50M launches has me extremely envious. I am using a home brew design 9.2 oz with AG455 46 47 no gyro and a great vertical climb out with rudder and elevator preset. Still air times 1.30. I have tried 1.5oz ballast and if anything this hurt the height by a couple of meters.
Don't know if ballast hurts or helps launch height. (I'll bet the theorists know) My LoLo measured launches in NC with Oleg were in a plane that must have been 12oz. with the LoLo in it.
Particularly for Phil and Oleg and Joe? was there a point at which you really started launching higher...any particular techniques or habits that got you this high. Any particular practice routines that got you more height.
I have tried really trying to wind up my lower body before then pulling/swinging arm+model and I am always running forward when doing this.
Phil Barnes answers:-
I was one of the lucky ones. My launches were high almost from the first day. For my first ever discus launch I just grabbed my trusty old javelin Logic by the wing tip and let her rip. That first discus launch was higher than eny javelin launch I ever did. Needless to say, great launch height improvements came as I learned to build better and better Discus planes, you can't get much worse than a javelin Logic for discus throwing. I think all of my launch improvements have come from building better airplanes not from throwing better.
Here are some thoughts on what might make a good discus throw: I agree completely with Joe W's recent post about the body as a torsion spring idea. I came to that conclusion some time ago myself. The new element from his post, for me, was the idea that the arm is just along for the ride. He may be on to something here. I was still thinking that after unwinding the torsion spring of the lower body, you should then try to get some arm action going. Not any bendig of the elbow or wrist, but maybe rotation of the arm around the shoulder. I had at times attempted to get more power into that part of the throw and I'm not sure it ever helped.
I don't think that running forward as you throw is a big positive or negative. I think I take two or three (not even sure) steps as I throw but for no particular reason. I can get 70-80 percent of a full launch from a standing throw. This means my left foot pivots but I wouldn't get called for traveling in a basketball game. It's all in winding up the lower torso and then unwinding as fast as possible.
Some things not to do for sure are bending the wrist and elbow. This only shortens the moment arm to the plane and makes the plane do really awkward things. At some point earlier on I used to concentrate on keeping my elbow straight. I never played baseball but a couple people who did have told me that there is a lot of wrist action involved in throwing a baseball and you really need to concentrate on not snapping the wrist if you have that habit.
The recent things I have tried to improve my throw have had only negative effects. I started trying to throw up rather than straight out (recent posts have talked about this) and this has only led to ground strikes. I agree with Craig on this one. keep the very slight up preset and throw straight out not up. I was trying to get more arm power into the throw but I now I may try to improve my lower body strength for torsion motions.
The elements of a good discus plane:
Everything must be stiff and not flutter or deflect in improper ways. Especially the tail boom. Use an allegra boom or equivalent. Control linkages tight and strong , especially the rudder, make it pull for outside rudder- I hate pull-pull systems.
Use a large vertical fin extending about 1/3 below the boom.
Thin airfoil. The Drela airfoils or whatever the Encore has.
Flutter proof flaperons. They may flutter even if you don't hear it. stiffer is always better.
Phil "torsion spring" Barnes