Michael Burbidge

Michael Burbidge

Well Known Member
I have a question on the very first step of the RV-9 empennage.

The directions say to cleco the HS Spar halves together with the spar doubler plate and then match drill all the pre-punched 1/8" holes. It seems straight forward. But there are three 1/8" holes in the spar doubler plate that aren't in each of the spar halves. Why is that, and should I drill those out creating brand new holes in the spar halves?
 
Michael,

Looking at the plans, I see four holes that are left open for attaching to the fuselage later on. Other then that, I think all the holes are marked for a specific rivet so they should be drilled. Read the plans carefully, as some of the holes will be countersunk. Have fun!
 
Alignment hole for attach angle...

I recognize the 4 larger attachment holes that you are referring to. The three holes I'm referring to are 1/8" holes. One of them I now see is the alignment hole for the attach angle for accurate positioning. The other two are above it, along the spar doubler edge. According to the plans these two should receive the same kind of rivets as the other 1/8" holes. So I'm going to drill them out to #30 like the others. Still not sure why the spar doesn't have pilots for these. In the next paragraph I'm instructed to drill the alignment hole. So I'll do that then.
 
Michael,

Are these the additional holes for the attach angle? If so, you should drill these with the attach angle in place (i.e., through all three pieces, the angle, doubler, and spar).

greg
 
Missing Spar Holes

It's because, IIRC, and that's rare, the front spars (HS-902) are identical... no left, no right. The section between the inboard rib holes and the 4 rows of three in the inboard edge, where your fabricated attach angles go, must be blank. The holes in the spars are match drilled using the doubler and your attach angle as guides.

I think what you may be unsure of is the order of things... Match drill the spars for the three unknown holes using the doubler as a guide. The attach angles will be fabricated and the 9 holes on the vertical flange are drilled based on accurate measurements (Plans say Accurate positioning required). Then the angles are cleco'd to the spar sub-assembly (doubler and spars together), and the remaining holes are drilled to the doubler and spars using the attach angle holes as guides.
 
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[email protected] said:
I have a question on the very first step of the RV-9 empennage.

The directions say to cleco the HS Spar halves together with the spar doubler plate and then match drill all the pre-punched 1/8" holes. It seems straight forward. But there are three 1/8" holes in the spar doubler plate that aren't in each of the spar halves. Why is that, and should I drill those out creating brand new holes in the spar halves?
Click to expand...

Michael-
These holes are not punched at Van's because not doing so allows them to use the same spar for both the left and right side of the HS. You first decide which one is left and right. Once you match drill them they will be permanently left or right. Hope this helps.
 
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