Small Catamaran Hull Joins

[Pouakai]

Hi All,

I'm looking into methods of joining catamaran hull halves as part of long term project.

The last time (many years ago) I was involved in building a production beach cat it was done by joining the hull and deck via a flange or coaming (like a Hobie 16), simple but detracts aethetically.

I know that the latest boats are joined from vertical halves through a combination of a tongue and groove joint in the flat areas of the hull and a wide flange in the bow areas, the gel coat is then filled and faired at the join. What I can't work out is how to do this using a method like VI, does anyone have any knowledge on how this is achieved in a female mold? Anyone got any better ideas for achieving a good join?

[Pouakai]

Ian Farrier has this excellent summary of female mold join options, doesn't give detail on the method of constructing the join though.

http://www.f-boat.com/pdf/FloatOptionsCompared.pdf

[idkfa]

I've seen a modified version of the vertical joint, where the deck area between the crossbeams is made as third part to the mould, giving access to the inside, for taping, bulkheads, chainplate etc. and then the deck is capped on.

Also you can fit the halves together and then demould, helps align the edges.

[Pouakai]

Thanks for the info, I've seen versions of that construction too. There are a few pictures showing that on Bimare website as well.

I guess what I'm really interested in is the details of the construction of the tougue and groove joint - how deep is the groove, how is each half of the join constructed - especially if it has been vac'ed down.