Rolf,
The excess resin comes out the join in the mould.

I've made half a telescopic spinnaker pole the same way
36mm dia. (Just carbon uni and a light layer of glass to make handling the carbon easier after its wet out)
The female section will have a 40mm internal dia. There will be two built up bands on the inside section of pole to take up the slack when the pole is fully extended.

I think it will be a good thing to have if I can make it work. Apart from making it easty to transport it would be good to get rid of that extra windage upwind.

Just another thing to play with.

Regards,
Phill

I know that the voices in my head aint real,
but they have some pretty good ideas.
There is no such thing as a quick fix and I've never had free lunch!