chopping and joining windsurf mast?

[sigurd]

should I use an inside wood dowel or outside glass mat/epoxy sheathing for the join? the purpose is to have a collapsable mast.

[frosh]

Sigurd, have a look at a standard 2 piece windsurfing mast to see how the join is made. The lower section has a thickened and reduced section at the top which is part of the structure, not added later. The top section of the mast slides over this reduced section and makes a very neat connection to the lower half. The windsurfing sail exerts pressure pushing the two halves together.
I dont know if you can manufacture a satisfactory join yourself. Better to buy a 2 piece mast.