[SvingenB]

I am sure this problem must have surfaced for many. According to the plans the HS-406 tip ribs shall be parallel to each other and perpendicular to the aft spar. A problem arises when the fwd spar is too large/small forcing the fwd tips on the HS-406 out or in. Mine are forced a bit out, so the should probably be fixed with new tip flanges on the fwd spar.

But, I can't find anywhere in the documentation what the tolerances are (how perpendicular and parallel is good enough, the tip ribs are far from a perfect shape so there will be large errors in measurement alone). Another thing is that this shall be done before the skeleton is put in the jig for skinning. I can then end up in the situation where the tips are 100% OK, but the rest of the ribs and spars are skewed.

I am wondering what others have done.

I have looked for tolerances in the drawings, but so far (emp) I have found none, not a single one. Are there some general set of tolerances somewhere in the documents that have missed my eyes?

 

[Rick RV-4]

Me too . .

That was a while ago for me, but mine were not perfect either. Your skin should overhang the ribs a little when you're done skinning, so you can trim the skin to a more "perpendicular" fit. I think mine were within 1/8 inch or so but I can't remember.

Even if you don't get a good 90 degree angle after that, you can vary the angle (slightly) on the elevator counterweight arms to match up with your horizontal stab skins.

This are truly hand built airplanes!

Rick

 

[SvingenB]

Ok, thanks. I understand it is not a big deal then. My tip ribs were slightly curved from top to bottom, like the side of a bottle. When I got that straight it was much better, the difference is now at least less than 2 mm, probably around 1 mm from what I could measure. It was about 5 mm before, but even that would be OK.