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Wing Angle of Incidence

Louavul

Louavul

Well Known Member
I'm nearing wing mate and drilling of the rear spar. The plans say to use a level and a "block" at the rear spar to get the 1 degree angle of incidence per drawing 38.

I've examined drawing 38 and find mention of the "block" but no measurements to fab the thing.

Is the "block" somewhere in the parts, already made, or do I craft it out of something to dimensions I don't seem able to find?

Thanks,
Steven L Hild
Belen, NM
RV-7 FUS
 
Gauge block

As to material to fabricate a block, I am planning just to use the stack of receipts obtained so far.
 
Last edited:
Good one

captainron said:
As to material to fabricate a block, I am planning just to use the stack of receipts obtained so far.
Click to expand...

That's rich!!!! If you're like me you'll probably have to pull a couple out to get it down to 3".

I used a piece of wood carefully cut and sanded to 3".
 
Transit

Hi Steven,
A builder's transit is much more accurate. The airplane can be levelled fore and aft and sideways with it as well.

Place the transit about ten feet from one wingtip and level it. Then have a buddy hold the blank side of a yardstick on the main spar while you sight through the transit and he can make a pen mark where the crosshairs aim. Then make another mark three inches above that one and place the yardstick on the rear spar and while you're looking through the transit, someone else can raise or lower the rear spar until the crosshairs align with the mark. Clamp the rear spar and then drill it.

Without moving the transit, do the other wing the same way.

Regards, :)
 
KISS

If the span dimension is, oh, 30 inches, and the block 3, the included angle is 5.71 degrees. A block 3 1/16 would produce 5.83 degrees. You are not going to notice this difference from the cockpit, but you will notice if the two wings are at different incidences no matter your block dimension. So be very consistent with your measuring technique; the precision of the block is not at issue. A bubble level works fine. It's sensitive enough to detect if you compress the wing metal gaps more or less on either end and the plane doesn't even have to be level (although it needs to be level to set sweep).

I would not recommend Pierre's method as it introduces more set-up error potential and must close dimensions across the shop floor and needs two people; too complicated. You'll also want the bubble level to verify flaps are stowed at the same angle, and back-up your aileron rigging by checking for identical angle-of-the-dangle.

John Siebold
Boise, ID
 
Yes, with the longerons level and the block in place, you want 0 degrees on the level. I think what John was getting at was that if the front and rear spars were at exactly the same height (not what you actually do) and the block was three inches, that the level would be at 5.71 degrees. If the block were 3 and 1/16, then you'd get 5.83 degrees instead. The point is that you don't need to have NASA build the block for you.
 
I've noticed a few builder sites that have pics of the wing leveling being done and have noticed on more than a few that the edge of the three inch block is lined up on the rivet line rather than on the front edge of the spar as per plans. So much for sanding the block to an exact 3". Back in that area of the wing there is enough rise in the curvature of the wing that it seems like it would make a signifigant bit of difference. Wherever you set your block make sure it's the same place on both sides.
 
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