Not the Brightest Bulb

[Event Horizon]

I've tried several types of fin alignment guides on BT80 tubes, but was never happy with them. For my 3" scratch build, I tried the downloadable fin guide from Payload Bay, and never looked back. The slots are indexed perfectly, and the only coast is the foamcore—$1.99 for a 20"x30" piece at Hobby Lobby.

https://www.payloadbay.com/index.php?page=Tools&action=FINGUIDES2
I used the alternate fin guide, taped it to a piece of foamcore, then made the straight cuts using a box cutter and heavy straight edge, and the circle cut using an X-Acto knife. (Go slowly and you'll get a nice cut on the circle.)

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Great photos Dane, That's the exact method I described 4 or 5 posts earlier, except cardboard was used instead of foamcore because it was easily available at home. I couldn't remember where the d/l was so thanks for sharing that information