David's method has the advantage of being able to use the centering rings and possibly cones for the core diameter. You can built up the cones by "fiberglassing" using a worn out nylon stocking and using either finishing epoxy resin or polyurethane to fill the weave. Because the nylon is stretchy it will conform to the contours of the cone. Pull the stocking over the cone and then "paint" the resin or polyurethane into the weave using a cheapy brush. Repeat the painting until the weave is filled.

Apparently, a stocking in the trash does NOT necessarily mean it's being thrown away; it may be in there for discipline. So always check with SWMBO before using an old stocking for this technique.

Don't ask me how I know.

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NAR 79743
NARTrek Silver
I miss being SAM 062

Awaiting First Launch: Too numerous to count
Finishing: Zooch Saturn V; Alway/Nau BioArcas; Estes Expedition; TLP Standard
Repair/Rescue: Cherokee-D (2); Centuri Nike-Smoke; MX-774
On the Bench: 2650;
Dream Stage: 1/39.37 R-7