RV-14 rear spar attach point / wing alignment

Having built an RV-8A previously, one thing that surprised me on the -14 wings is that the rear spar attach hole is drilled and reamed to final size during the wing construction process. On my -8A and other RV models that friends are building (including the -7 and -10), you don?t drill the rear spar attach hole until the wings are attached to the fuselage. You install the wings on the fuselage using temporary bolts in the main spar, then carefully align the wings to have the same angle of incidence and make sure the wingtips are the same distance from the aft end of the fuselage. Then you match drill the hole in the wings and fuselage together.

Looking at pics of the fuselage from other builders, the -14 appears to have the rear spar attach holes also drilled to final size apparently without ever mounting the wings. Is this correct? I know the prepunching is very accurate, but people are managing to build twist into prepunched control surfaces. There?s got to be a tolerance stack up between the two wings, the fuselage alignment between front & rear spars, and the process of the builder enlarging the holes to final size. It doesn?t take much to get a slightly different incidence in each wing which would lead to it being out of trim in roll and/or drop one wing first in the stall.

Has anyone installed wings on their fuselage and checked incidence to confirm both wings are the same?

Yep.

Mark, the -10's are also pre-drilled and that's a shortened -10 wing on the -14. My -10 flies incredibly straight. Yes, they are that good

Best,

Ok, sounds good. I asked a friend who has a -10 with over 1000 hrs on it and he remembers match drilling them the same way I did on my -8A kit, so either he remembers incorrectly or else there was a change in the -10 kit before you built yours.

Either way, it's pretty impressive that the parts align that well, and it eliminates yet another tedious step I had to perform when building the -8A.

Interesting that a couple friends who are building RV-7A's are still required to align the wings and match drill the holes in the rear spar the old fashioned way. One of them just did that step over the weekend on an QB kit he bought a little over a year ago. I wonder if the design of the -7 is not as accurate as the 10 & 14, or if that's an improvement that just never made it back into the older kits...

Thanks,

pierre smith said:

Mark, the -10's are also pre-drilled and that's a shortened -10 wing on the -14. My -10 flies incredibly straight. Yes, they are that good

Best,

Click to expand...

The -10 does have a pre-drilled hole for the rear spar, but it's only half the final diameter. So while the instructions just say to cleco, clamp, and sequentially drill up to final size, there is some opportunity to move it up or down a bit first, if needed. I don't know how many builders check this before drilling; I know I did, and I couldn't detect any error in the hole placement.

czechsix said:

I wonder if the design of the -7 is not as accurate as the 10 & 14, or if that's an improvement that just never made it back into the older kits...

Click to expand...

There is more to it than that....

The RV-7 wing is also used on the RV-8 with some builder trimming to the rear spar attach parts depending on which airplane they are used on, so that is one of the main factors but there are others.