Vertical Stabilizer Spars - counter sink or dimple?

[JVolkober]

I am about to counter sink the spars on the vertical stabilizer. It looks like dimpling would be a good alternative. Does anyone have a recommendation one way or the other?

 

[scard]

If I remember correctly, that spar is .040. Dimpling a spar like that induces the risk of deforming it slightly along its length. My opinion is machine countersink. But be very careful to not over due it and make the hole too big. I say it is better to be a hair short on the countersink than to make the hole too big. I think this is a reasonable rule for the new builder when in doubt (short of all the micro analysis technical details).

http://rv9a.card-net.org/archives/category/empennage/vertical-stabilizer/

 

[JVolkober]

Thank you

Thanks for the response. I spoke with Van's and they also warned about possibly deforming the flange but thought with the narrowness of the flange the risk was minimal.

By the way, your web site has been very helpful to me. It led me to the work bench design and I intend to build the spray booth using your design.

John