Rail guides

Delrin, plastic, aluminum, acetal, conformal...
What are the best and most durable rail guides to use, and what is the best method for attaching them to the airframe (epoxy, screw with backing plate...)
Thanks

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It depends on the rocket. How about some particulars?
Size, weight, expected speed, describe airframe thickness and composition etc. Phil

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Well, right now I'm building two:
1. 5 lbs, 7 ozs, 0.125" fiberglass, 54mm MMT, about six feet in length.
2. 3 lbs, 14 ozs, 0.125" phenolic (non-fiberglassed), 38mm MMT, about 4.5 feet in length.
Weights without motors, not sure about expected speeds at this point.

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Oh, and both are 4" in diameter.

NaCl wrote:
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Use delrin (or some other plastic) buttons that are attached in such a way that they are easy to replace. It is much simpler to replace worn buttons than it is to repair or replace munged launch rails.
I like to screw them into a centering ring if one is handy. If it isn't, I cobble up a backing plate from plywood sanded to match the tube profile and a t-nut in the plate. This way I can easily replace the buttons if they become worn. But I haven't had to replace any yet.
The aluminum rail guides that I have seen look like they were designed to damage launch rails. The part of the guide that rubs against the launch rail has a sharp 90 degree edge which will dig into any imperfection on the rail. Why they don't at least break those edges is beyond me.

I use nylon buttons from www.railbuttons.com and a self-clinching nut on the inside of the airframe and tack with 5 minute epoxy. If the button is in the path of the recovery system I "cover" the nut with epoxy clay. This adds very little weight and makes the buttons easy to change similar to David's method described below.
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