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Rudder skeleton drilling question

J

JurgenRoeland

Well Known Member
Bit confused on the directions in the plans for the RV7 in the section "building the rudder skeleton".

Near the end of this chapter Vans states:
"The aft three 3/32 holes in the upper edge of R901-L and R901-R should be drilled #30 and dimpled. These holes will later be used to attach the R-909 rudder tip. While the holes could be opened to #30 when drilling the tip to the rudder, it would be nearly impossible to dimple the skins because the rudder is so narrow at that location'.

I assume they are refering here to the top row of prepunched holes in the skin (the line above the R903 rib). The rib itself goes with 3/32nd rivets, the line above for attachment of the fiberglass rudder tip calls for CS4-4 pop rivets.

Why do they talk about dimpling here ??? A pop rivet needs no dimpling ? Or does it.

Thanks for the help.
 
The CS4-4 pop rivets called for in that location are flush rivets. So the skins need to be dimpled, and the rudder tip will be countersunk. Vans is suggesting to dimple the skins now because it's much easier to do it now. Once those skins are riveted to the rudder skeleton, it will be very narrow and nearly impossible to get dimple dies and a squeezer yoke to fit in there.

Hope this answers your question.
 
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CS in the rivet designation stands for "counter sink", it is a flush pull rivet. The other common designition, LP is for pulled rivets with a "low profile" head that does extend above the surface being riveted, as a round head/universal rivet does.
 
I learned something!

I didn't know that, Wil. Thank you! Here I've built almost an entire airplane and didn't know that. Thanks for shedding the light.
 
One thing I wish I'd known about earlier in the build, but found out midway through...

If you're countersinking for CS pulled rivets, use a 120 degree countersink.

I believe there is also 120 degree dimple dies, too, but didn't need them anywhere after the empennage was done, as far as I can remember.
 
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