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Boomer506

Well Known Member
I'm wondering if anyone has advice for hole preparation for the CS4-4 pop rivets used on the aileron bottom skins. Do you dimple for a -3 rivet then drill out to 1/8th inch? Or do you dimple for a -4 rivet from the start. I've worked with some practice material using both methods and they both seem to work OK, but I worry about a larger dimple on the aileron spar. Thanks in advance for any advice.
 
CS4-4 rivets have a 1/8" shank so you drill to #30 and then dimple. They actually have a different countersink angle (120 vs 100 degrees) than other countersunk rivets we use. Many folks just use their standard dimple dies but 120 dimple dies and countersink bits work a little better. They are available through Avery, Cleaveland, etc.

Bob
 
If you can located someone building a 12 nearby, they will have both 120 degree dimple dies & countersink.
 
double dimple - for the perfectionist

If you drill #30 and dimple 120 degrees the hole will come out big, nearly .140"
So big the clecos barley hold.
If you care to, you can drill #40 and dimple with your 3/32" x 90 degree set.
Then cleco it all up again, drill 1/8" (not #30) and dimple 1/8" x 120 degrees.
If you do all this, the hole will be .130 or so. And the 1/8 clecos will hold solid.
 
markscogg said:
If you drill #30 and dimple 120 degrees the hole will come out big, nearly .140"
So big the clecos barley hold.
If you care to, you can drill #40 and dimple with your 3/32" x 90 degree set.
Then cleco it all up again, drill 1/8" (not #30) and dimple 1/8" x 120 degrees.
If you do all this, the hole will be .130 or so. And the 1/8 clecos will hold solid.
Click to expand...

Drill #30 and use your 100 degree dimple die for the CS4-4 rivets. If you must, use 120 degree dimples dies - but not necessary.

re Marks comment: 120 degree dimple is shallower than the 100 degree dimple. Never had a problem with 100 degree dimples so I doubt 120 would be an issue.

See page 7 of this document
http://www.vansaircraft.com/pdf/revisions/RV-ALL_Section-5.pdf

We don't use 90 degree dimples.
 
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