"Garland Gray II" wrote:

..
If I were to wax the outside of a piece of 2 1/2 inch pvc pipe about
6 feet
long, and then lay up several layers of fiberglass and epoxy, would
the
resulting tube slide off the pvc easily enough after curing ?

NO.

Or would I
need to first wrap the pipe with sheet plastic or similar ?

Depends.

Easiest solution is to glass pvc tube and leave it in place.

It what I did to make a shaft tube.

Next approach was using an 8" PVC pipe for a mold to fabricate a bow
thruster tube..

First you slit the PVC pipe on one side using a table saw.

Then you plug the ends of the slit tube with wooden plugs.

Next, cover slit pipe completely with clear contact paper.

Support tube on each end.

Next, using light weight glass, say 17 OZ, double bias, wrap tube in a
continuous wrap until yo get req'd layers.

When cured, cut off plugs and break PVC pipe in pieces to remove.

Doubtful you can do this on a small pipe such as 2-1/2".

If you must remove PVC tube, the cover it with contact paper and wrap
2-3 layers of glass.

When cured, slit both glass and PVC tube with a saw, the spring
lamination open to remove PVC tube.

Repair cut in glass, then use a mold to finish layup.

I've done all of them.

Have fun.

Lew