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Pops

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Down flaps with up elevator did wonders in being able to do sharp corners on CL stunt models.
 

Wild Bill

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Dec 11, 2013
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Vidalia, GA
On the subject of control line models. CL planes are really only “free” on the pitch axis. Yaw and roll are locked in to some extent by the lines running through guides in the inboard wing tip.
Those lines have a substantial load on them, so the model can only move a relatively small amount on the roll/yaw axis. Some CL models don’t even have any vertical surfaces at all.

When I read that section in Ribletts book I thought about a couple of RC models I experimented with.
The first example was a low aspect ratio flying wing. It had washout, a modest amount of sweep, and a lot of taper. It was also heavily loaded.
When inverted this model should have had horrible stall characteristics when inverted right? It actually flew better inverted in all phases. Leading up to, during, and post stall.
I thought that maybe fying wings were such a mixed bag that it wasn’t a good example.
So the next model I experimented with was a typical acro monoplane. It had a symmetrical section with washout and no dihedral. Also it just so happened that it had tube spar plug in wings with the spar and pins on the zero line at the root. So I could put the wings on upside down.
Again the thinking I had was that in a configuration where the wings had washin (either flying inverted or wings on upside down) stall characteristics should be bad.
But they were not. It didn’t really make any difference.
This may not scale up well but it did make me wonder if washout was really needed.

On certain GA planes the use of washout may not have been done specifically for stall qualities, but more for structural reasons.
To me it seems like trying to design specifically for stall characteristics shouldn’t be a primary objective for a one of a kind homebuilt.
If a plane has bad stall characteristics, then you just avoid stalls.
 

mcrae0104

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To me it seems like trying to design specifically for stall characteristics shouldn’t be a primary objective for a one of a kind homebuilt.
You seem to disagree with the designer of your aircraft. I am not aiming for a spin-proof aircraft, only one with consistent and manageable stall characteristics. This should be a prerequisite for any aircraft design.

After spending the better part of the holiday weekend with Gudmunsson, Raymer, Perkins & Hage, and Abbot & von Doenhoff, I have concluded that Riblett's claim that only thickness tapering, not planform taper, governs stall progression, is unfounded. NACA TR 572, covering cl distribution of tapered and twisted wings, was the clincher.
 

Lendo

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Feb 6, 2013
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Brisbane
If you want to manage the possibility of stall, do what a lot of designers do - limit Elevator travel.
George
 
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