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prkaye

Well Known Member
What will the symptoms be of a wing with a slight twist?
I am just at the point of riveting my top wing skin on. I've been using the plumb-bob method to measure twist (as described in the plans). I've got wooden wing stands and a very uneven garage floor so it's been a lot of shimming and clamping the ends of the main spar to try to get the twist out before I rivet the skins on. Right now I've got it just barely to Vans' published tolerance (3/32 inch difference between inboard and outboard plumb-bob string to rear spar flange distance).
I have a strong suspicion that even though I'm able to clamp the twist mostly out now, after I rivet the skins on and un-clamp the wing it will do what it wants to, and I doubt it will have zero twist. Does this create a very dangerous situation?
With such a long spar (-9A) getting rid of wing twist seems to be quite a challenge (to me)!
 
Hopefully there's some tolerance

I have QB wings and the finished product had 0.3 degrees of twist in them. That works out to be about a .5" offset between the tip and root (y=tan(0.3) x (9x12)). I think the wing panel is about 9' if memory serves me.

-Rick
 
Small amounts of twist will cause a small increase in drag, and may cause you to spend a few additional hours in the flight test phase tweaking ailerons and flaps to get the aircraft to fly hands off. There may also be a bit more of a tendency for one wing to drop at the stall. If you have effective stall warning, and you recover at stall warning if you ever inadvertently encounter it, then this is probably quite acceptable. If you don't have effective stall warning, a wing drop at the stall probably increases the risk of an accident.

Do the best you can to build a wing without twist, and then never measure it again.
 
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