Line III

[RC Storick]

Line III now available from Stunt Hangar download section or at this link

http://www.stunthanger.com/temp/LineIIISetup.exe

[Bill Gruby]

Robert;

Without sounding to illiterate, what pray tell is "Line III". Is it something that I really need?

I know in this computer age it's difficult, but in giving your reply could you keep it kind of simple. I'm still trying to get to level  2 with this thing.

Bill Gruby

[RC Storick]

Line III will help you set your initial line rake for bench trimming.

[Bill Gruby]

Thanks Robert--------Sounds simple enough--------Will take a peek.


Bill Gruby

[Bill Smith]

Thank You
 
 Tried it and compared it to two planes that I think are setup right and they are a close match. So from now on I will use this for the initial setups and save myself some guessing.

[Bob Disharoon]

Robert;

Without sounding to illiterate, what pray tell is "Line III". Is it something that I really need?

I know in this computer age it's difficult, but in giving your reply could you keep it kind of simple. I'm still trying to get to level  2 with this thing.

Bill Gruby

"BG.".I can't believe you actually said that.Is there anything YOU really don't need ?....lol..."HD"

[Peter Germann]

Line III will help you set your initial line rake for bench trimming.

Related to LineIII, two questions I wish to clarify are:

1.) On may latest airplane the location of the C.G. varies approx. 1/2 in between full and zero fuel. IF, as I assume, LineIII's "Leadout position behind C.G."  is calculated from on the in-flight C.G. (with fuel), is it correct to use 3/4 fuel load when defining the airplane weight and the location of its C.G.?

2.) With LineIII giving the leadout position for level flight (with 3/4 fuel on board), what can I do to get the proper leadout position when flying overhead through the top of circle with only 1/4 fuel left?

rgds  Peter Germann

[Bob Reeves]

Hi Peter,

The best person to answer your questions would be Pete Soule but he doesn't hang out here. My answer is to do what everyone else does, use LineIII for a starting point and fine tune from there.

[Peter Germann]

Hi Peter,

The best person to answer your questions would be Pete Soule but he doesn't hang out here. My answer is to do what everyone else does, use LineIII for a starting point and fine tune from there.

Thanks, Bob.
Trying to simulate the overhead situation, what I did was playing with input numbers (airplane weigth) until Line III returned a line pull figure being equal to the line pull in level flight minus the weight of the airplane. (-1G) Resulting was a leadout position approx. 1/2 in rearward from the number for level flight. Assuming that this setup leads to accurate tangency of the fuselage when flying through the top of the circle, I would hope to prevent drag caused by yaw in a place where I cannot afford to have it. Yes, I do realize that a line leadout position "optimized" for overhead flying will lead to a bit of yaw to the outside in level flight, but I believe this is a trade-off I can accept in exchange against better line tension where it counts more...
Considering the substantial difference of leadout positions between "level flight with full fuel" and "overhead  flight with min. fuel" I would really like to know whether my assumptions are correct. When you are mentioning Pete Soule, does this mean he is the author of LineIII?

[Bob Reeves]

Pete was the brains behind the math, I put a user interface on his work and out came LineIII. The LineIII download should have included a couple pdf files written by Pete that go deep into the mechanics of his work.

Never really thought about the overhead situtation but what you are saying sorta makes sense. The only issue that comes to mind is that we typically start moving the leadouts forward if we have overhead line tension problems. Maybe someone that really understands this stuff will chime in. Sure is a great question...

[Mark Scarborough]

what Bob says is true, typically to enhance overhead line tension (all other things being trimmed close) you move the leadouts forward, which decreases the speed you scrub off overhead, the speed is what maintains line tension overhead more than anything else. a couple other things to think about, I have had problems with fuel feed if the airframe is yawed out to much, I am talking moving the leadouts less than a 1/4". had it quit in the clover, ie low speed and corner g forces. Before comments are made, my tanks have a offset in them so the pickup is outboard to begin with. The other issue that would concern me is the yaw introduced in square manuevers by having the leadouts trimmed intentionally "off" normal position.

[phil c]

As somebody said someplace else, the calculation is a tentative place to start, not an unchangeable design feature.  Set the initial position via Line III and then trim as necessary.  I believe most people find themselves moving the leadouts forward for better overhead tension, once they fly the plane, but it all depends on how the thrustline, balance point, wing offset(if any), rudder offset, and other little vagaries balance out in the air.

[FLOYD CARTER]

What Bob Reeves said, and the usual practice of having the lines exit about 3/4" behind the CG is really all you need to know.  The smart trick is installing an adjustable leadout gadget.  It only takes a couple flights to get the leadouts in exactly the right place.

I know some people spend a lot of time writing some computer programs for a procedure which is so very easy to zero-in, with only a flight or two.

Floyd in OR