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Building Tips and technical articles. => Building techniques => Topic started by: Mike Quinn on February 11, 2020, 01:08:05 PM
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Hello
Hello
For a Cardinal type and sized profile model ... what would you guys recommend for the elevator and flap horns. I've been looking at the StuntHanagr shop products.
https://stunthanger.com/hobby/index.php?cPath=24_49
When would you use the different sizes of flap and elevator horns, adjustable, bushed or ball link. First time I've built a flapped model so any help appreciated.
Cheers
Mike
PS also, I've seen some suppliers where the horns are straight and some cranked. What's the difference per se?
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These are Tom Morris units. It's what I use. Be careful to specify lengths of horn. I like Ball Link connections.
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PS also, I've seen some suppliers where the horns are straight and some cranked. What's the difference per se?
I assume you mean the upright of the horn. Most of then have a clearance near the base (where it connects to the cross-bar) to permit the horn to move without having to put a long groove in the wing for clearance.
Some of them have an angle in the upright itself, to try to correct some of the geometry problems that lead to inconsistent rates of travel between "up" and "down". Generally it is an attempt to make the angle formed by the pushrod-ball link-crossbar 90 degrees at neutral, particularly the pushrod from the bellcrank to the flap horn. It's actually a complex 3-d geometry problem to get it perfect, but you can get pretty close with much simpler corrections.
This is extremely important to having consistent and predictable control response.
Brett
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Use the 1/8 " wire ones . NOT the 3/32 " . Theyre like Fox .35 ones .
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Use the 1/8 " wire ones . NOT the 3/32 " . Theyre like Fox .35 ones .
3/32" suffices for elevators. Even so, I'd like to find a lighter way to make an elevator control horn.
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I've seen some suppliers where the horns are straight and some cranked. What's the difference per se?
As Brett said, it's a 3D problem. Turns out you can make either of those flap control horns give a linear relationship between leadout travel and control deflection by fiddling with bellcrank position and bellcrank output hole location. I haven't looked into figuring out simpler corrections. I suppose I oughta. I just do the full zoot 3D analysis on each airplane.