Michel,
The parts to make them watertight will not be installed until after the floats and beams are joined. Only because it will be easier to do the glassing of the fwd beam to the bulkhead without them being in place.
They are nothing fancy just straight out of the plans.
They are not complete yet but I'll try to remember to take a pic of where they are at and post it so you can see. I will be drilling drainage holes so any water that get past the hatch seal will be caught in a channel and leave via the drainage holes.

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!