thank you rubi, jake and the other authors again for the detailed informations and and very helpful hints.

rubi, I totaly agree that the only forces I expect the extended bows have to deal with are those from the waves.

while those can be significant, I also believe that the blue foam would be stiff enough if coated well on the outside.

how thick would you suggest to make the skin if using glassfibres? would 2 layers of 160 g /m² do the job?

I will try to use the vacuum principle to get a good connection between the glass and the foam.

anyhow, will surely keep track with a camera once action starts and will report progress than. :-)