Van's Air Force
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twisted elevator
- Thread starter Paul B
- Start date
If I am right, the -9 has a trailing edge wedge like the -10 rather than a folded skin. In any case, one of the things that is NOT made clear in the general instructions is the importance of not starting at one end on a spar etc and working along although they go into length about doing it with a trailing edge. I got through 3 trim tabs before I worked it out!!
As for fixing it, you may be able to drill out and re-rivet but it's a lot of holes and you are inevitably going to end up with several over-sized and/or damaged holes. I don't think there is any way you can "ease" the twist out once it is in. Maybe it's better get new parts - all part of the learning process, although I appreciate the elevator is a lot of work to redo.
My suggestion when riveting skins to a spar is to ensure everything is square and clamp it to the workbench using a flat board if necessary. (Note to self - make sure workbench is square/flat). Then when you rivet, use a semi-random pattern - a couple of rivets in each panel and then fill in the gaps -keep halving the spaces - much like the instructions for the trailing edge.
Since I starting working like this I have had great success, with immaculately square control surfaces.
As for fixing it, you may be able to drill out and re-rivet but it's a lot of holes and you are inevitably going to end up with several over-sized and/or damaged holes. I don't think there is any way you can "ease" the twist out once it is in. Maybe it's better get new parts - all part of the learning process, although I appreciate the elevator is a lot of work to redo.
My suggestion when riveting skins to a spar is to ensure everything is square and clamp it to the workbench using a flat board if necessary. (Note to self - make sure workbench is square/flat). Then when you rivet, use a semi-random pattern - a couple of rivets in each panel and then fill in the gaps -keep halving the spaces - much like the instructions for the trailing edge.
Since I starting working like this I have had great success, with immaculately square control surfaces.
i also had a trist but it was on my vertical stab. i called vans and they said it would be ok and didnt think it would be necessary to rebuild but might have to use a tab, which i dont mind doing. i noticed it by laying it flight on the table during tail assy. my jaw dropped but i felt a little better knowing i might not rebuild but every time i go to bed and think about it, well we all know that feeling so for now, i leaving it alone. mine got that way from clamping down the skin a little too much during riveting. i think the only solution would be to drill the forward spar. i say build on.
Well, everybody has to make their own decisions as to what is acceptable and what is not. Small movements of control surfaces have a large effect on flightpath. Soooo.... it seems to follow that small warps in a control surface are going to have a large effect.
I scrapped 3 trim tabs on my -10 because of a 1/8th warp before I worked out how to keep it straight. Maybe that's over the top but in the big scheme of things it didn't cost that much or take that much time to fix. To me, 3/8th on an elevator sounds like a lot of warp. Average that over the length and it's equivalent to 3/16th movement.
To my mind, there is too much gung ho "build on" advice on this forum. That's not to say that there is not a lot of good gen - I have listened to and taken away a lot of it. You just need to have the gut feeling.
Whenever I have had an issue, my inspector has asked me "are you going to be happy with that when you look at it when you have it flying". The gut instinct has always worked.
I scrapped 3 trim tabs on my -10 because of a 1/8th warp before I worked out how to keep it straight. Maybe that's over the top but in the big scheme of things it didn't cost that much or take that much time to fix. To me, 3/8th on an elevator sounds like a lot of warp. Average that over the length and it's equivalent to 3/16th movement.
To my mind, there is too much gung ho "build on" advice on this forum. That's not to say that there is not a lot of good gen - I have listened to and taken away a lot of it. You just need to have the gut feeling.
Whenever I have had an issue, my inspector has asked me "are you going to be happy with that when you look at it when you have it flying". The gut instinct has always worked.
mikehoover
Well Known Member
I have 3/8" of twist in my right elevator. When I discovered it, I called the Mother Ship, who said, "Don't worry about it. 3/8" of twist is aerodynamically insignificant. You'll never know it in flight." I was happy to take their advice.
This is great to hear! I have about 3/8" twist in my right elevator. I was told to not worry, build on and once flying, if this caused undesirable flight characterists, to deal with it then. Here's a picture showing a length of twine stretched the entire length of both elevators, showing the right one with twist upward towards the inboard. The twine is out of focus, but you can see it well enough. The left elevator/trim tab line up nicely (though shown here the trim tab is hanging down):
http://www.aclog.com/rv-9a/images/Fuselage/00ccb145212b0f7ef447730e0888dbf030780_DSC_0246.JPG
n2prise
Well Known Member
Avoiding twists in control surfaces...
When I first built my work bench, it had some minor sag in it from end to end. By the time I got to the flaps and ailerons in the wing construction, I built a raised and perfectly straight BOX from parts of the wing spar shipping crate. It was great for drilling holes to let clecoes pass through during riveting, etc.
You can read all about it on my page 11 at this URL:
http://www.n2prise.org/rv9a011.htm
I got lucky with the elevators being straight on the trailing edge. I suppose it was because I built them near the end of the table, not across the sagging edge near the middle. Here is the first photo of the work bench on wheels before the airplane construction began.
For you guys who are thinking about building in a one-car garage, take a look at my PAGE 1 when I built the "Enterprise" RV-9A.
http://www.n2prise.org/rv9a001.htm
When I first built my work bench, it had some minor sag in it from end to end. By the time I got to the flaps and ailerons in the wing construction, I built a raised and perfectly straight BOX from parts of the wing spar shipping crate. It was great for drilling holes to let clecoes pass through during riveting, etc.
You can read all about it on my page 11 at this URL:
http://www.n2prise.org/rv9a011.htm
I got lucky with the elevators being straight on the trailing edge. I suppose it was because I built them near the end of the table, not across the sagging edge near the middle. Here is the first photo of the work bench on wheels before the airplane construction began.
For you guys who are thinking about building in a one-car garage, take a look at my PAGE 1 when I built the "Enterprise" RV-9A.
http://www.n2prise.org/rv9a001.htm
twisted aileron
my first aileron turned out fine.
the second one, not so much.
I drilled out all the rivets and started over - no joy
I finally ordered all new parts and got it right the third time.
Maybe it was acceptable the first time but I wasn't sure. I think we tend to become too critical of our own work.
Mostly, it seems like Van's advice is to build on and address the imperfections later.
I've seen more rudder & ailerons trim tabs on certified planes, so maybe we should ease up on the perfection
Dave
-9A FWF kit (done - now its time to paint...)
N514R
my first aileron turned out fine.
the second one, not so much.
I drilled out all the rivets and started over - no joy
I finally ordered all new parts and got it right the third time.
Maybe it was acceptable the first time but I wasn't sure. I think we tend to become too critical of our own work.
Mostly, it seems like Van's advice is to build on and address the imperfections later.
I've seen more rudder & ailerons trim tabs on certified planes, so maybe we should ease up on the perfection
Dave
-9A FWF kit (done - now its time to paint...)
N514R
I'm building another one
The e-mail response from Vans indicated that less than 3/4" twist in the elevator wouldn't cause a problem, and I should continue with what I have.
However . . . when both elevators are on the HS, I believe even a casual observer would notice something wasn't right and I certainly would notice every time I looked at the plane! So subtract about $300 from my checking account and add a few pounds to my aluminum scrap barrel. I will certainly check this new elevator more often during it's construction. Thanks everyone for your tips!
The e-mail response from Vans indicated that less than 3/4" twist in the elevator wouldn't cause a problem, and I should continue with what I have.
However . . . when both elevators are on the HS, I believe even a casual observer would notice something wasn't right and I certainly would notice every time I looked at the plane! So subtract about $300 from my checking account and add a few pounds to my aluminum scrap barrel. I will certainly check this new elevator more often during it's construction. Thanks everyone for your tips!
