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Bottom skins on the -12

pierre smith

pierre smith

Well Known Member
I started on the emp section today and after joining the flat, bottom skins, the curved side pieces came next. For the life of me, I can't get them to lay flush against the bulkheads...there's about a 1/4" gap between the skins and the bulkheads in the curved section.

What's the secret, guys?

TIA,
 
Shims. Van did it on his as well, I believe. It's been discussed quite often on the RV-12 forum. I didn't bother with shims on mine, and once the tailcone is fitted to the fuselage the problem seems to largely go away, although not entirely.
 
No shims needed.

I consulted with Ray Lawrence, a multi time (16+) RV's builder and he said to put cleco's in every hole in the curved part of those lower side skins. After a bit of wrestling and the use of an icepick I managed to cleco every hole and whaddya know...voilaaaaa...a snug and perfect fit with no need for any shims at all. You can jiggle the cleco's sideways and fore and aft and see the skin and bulkheads slowly nestle into perfect position!

Some valuable advice there.

Best,
 
Good solution Pierre. Come to think of it, I don't recall having any problem with the curved side/bottom pieces, but the flat side pieces seem to be the ones that cause a problem and that some builders have shimmed. You can find some discussion on this in the RV-12 forum. The flat sides tend to oil-can a bit between the fuselage formers.
 
If I were to build another RV-12 tailcone, I would pay particular attention to ensuring that the various angles of the tailcone bulkhead flanges match the angles of the adjacent tailcone skins. Remember, it's a cone, not a cylinder.

Having said that, when you finally attach the tailcone to the forward fuselage things seem to fit magically (thanks to Van's and CNC) and most all of the potential oil-canning worries go away.
 
DHeal said:
Having said that, when you finally attach the tailcone to the forward fuselage things seem to fit magically (thanks to Van's and CNC) and most all of the potential oil-canning worries go away.
Click to expand...

David,

Are you saying you didn't shim the sides and had oil canning when you built the tail cone, but when you attached the tail cone to the forward fuselage, the oil canning went away?

Thanks,
 
I'm sure David will respond too, but that's what happened in my case. My side skins still `pinch in' slightly at the first two formers when the light's in the right position, but certainly not enough to bother me.
 
The skin of the tailcone is relatively thin and literally reflects every curvature or slight bulge/depression. My RV-12 is not yet painted so the reflections from certain angles are more obvious. This is more noticeable to the critical builder than to anyone else. You do the best that you can, don't obsess about it, and build on. As I said earlier, when the tailcone is riveted to the forward fuselage, most of the looseness goes away.

ps - I did not shim anywhere in the tailcone.
 
Tail cone

We were early builders (120002). Put a cleco in every hole and things moved nicely into place. No shims. I have not noticed oil canning. Have 600 hrs on it so far. An amazing, very capable airplane.

Rich
 
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