D

dinowal

Active Member
A cautionary tale for those builders who have not yet constructed the flaperons. Page 18-06 step 1 instructs us to "check that the inbd. & outbd. Flaperon skins are bent properly as in Figure 2." Mine were not, the V bend at the trailing edge needed closing up. I first tried squeezing the trailing edge between two pieces of flat timber 3 or 4 feet long; even with plenty of pressure this had no effect. My next move was to do as Step 1 also says: " work the skins by hand until they lie flat against the main ribs". This certainly closed the V in the skin up, but unfortunately on inspection after, I could see that my manual squeezing had produced a series of wriggly looking dents along the trailing edge, even though I don't think I have particularly strong hands. Disappointed, I moved on, & squeezed the other skins by hand between 2 pieces of smooth timber about 9 x4 inches with an old soft towel over the trailing edge, producing almost perfect results. Now I have one really nice flaperon & one not quite so nice. This may be one of the rare times when it pays to ignore the Vans instruction, or at least proceed with extreme care.... Cheers, DEAN... Moving on to Fuse..
 
Dean, just to add to your very good description. Being a novice builder at the time, I didn't "get" how much squeezing I should do, and didn't do nearly enough. When I first started to fly the airplane, it exhibited "aileron snatch" when moving the stick off center. I had to do some research, and found this to be a result of those rounded trailing edges. I used a padded edge seaming tool to carefully do the required squeezing, and at the same time corrected for a wing low tendency. Your advice is good info for those newer builder's. Do the squeezing while you are building - get those trailing edges right the first time - it's easier that way!
 
My worst part of the project is my ailerons also. I did not quite understand what I was supposed to be doing, and have considered doing them over with new skins. I too would appreciate more info on what you did to salvage yours.

BigJohn said:
Dean, just to add to your very good description. Being a novice builder at the time, I didn't "get" how much squeezing I should do, and didn't do nearly enough. When I first started to fly the airplane, it exhibited "aileron snatch" when moving the stick off center. I had to do some research, and found this to be a result of those rounded trailing edges. I used a padded edge seaming tool to carefully do the required squeezing, and at the same time corrected for a wing low tendency. Your advice is good info for those newer builder's. Do the squeezing while you are building - get those trailing edges right the first time - it's easier that way!
Click to expand...
 
When I bent my skins I did it in increments and kept slipping them over the ribs until I got them to just lay fat. I had a heavy right wing in testing and never got the trailing edge squeeze to work at fixing it. I ended up riveting trim tabs to the ailerons and that did the trick. Purists may not like the look of tabs, but they give you a lot of flexibility. I also put a tab on the rudder.

I've never experienced the aileron snatch some describe.
 
Aileron snatch?

I have not heard the term "aileron snatch" before, - it doesn't sound good, - can someone describe it? thanks, DEAN...
 
If you do a search of these forums with the word "snatch" you will get a lot of hits. As I understand it, in a full blown aileron snatch, the stick is actually snatched from the pilots hand and goes to a full deflection. In my reading, this seems to be a phenomenon that one would only see in extreme situations - with airplanes, control deflections, and at speeds way out of what we would see in an RV-12. What I experienced in my plane, and have also found in another RV-12 that I test flew for another builder, is where when the stick is moved slightly off center, there is a little bump or jerk that pushes the stick off center a bit further. It is not dangerous or even very exciting, just a bit annoying. When I investigated this behavior I was told it was "aileron snatch". I think there was an article in an old RVator, but I can't find it now. Perhaps "aileron snatch" is not the proper terminology to use for this, but that is what I was told at the time. At any rate, the cure was to properly form the trailing edges of the flaperons. Here is a link to my original post: http://www.vansairforce.com/community/showthread.php?t=68976&highlight=snatch
 
dinowal said:
I have not heard the term "aileron snatch" before, - it doesn't sound good, - can someone describe it? thanks, DEAN...
Click to expand...

In fact "aileron snatch" is described in the "RV-12 Acceptance procedures" in section F0 - Flight Test Procedure - Lateral(roll) trim. Its effect is described as John Peck did experience. It is caused by a large trailing edge radii on the aileron. I quote: "correcting aileron snatch can usually be accomplished by reducing the trailing edge shape and radii to that shown on the plan". Easier said than done but I think using a padded edge seaming tool as mentioned by John should help.
 
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