Some years ago I observed a building technique that may be of interest. The catamarans were Wharram designs but maybe the technique could be extended or modified for other designs. No complex molds required.
On a workshop floor, a smooth surface of Masonite - a hard thin very smooth material -was laid and checked for "flatness". A release agent was applied and then fiberglass
and resin (probably polyester, but vinyl ester or even epoxy
could be used considering the relative merits and costs of each). I assumed the builders knew what layup
was required. the glass was hand laid and long broom handled resin rollers kept the resin /glass ratio under some control.. The sheets
were then lifted off the masonite with "perfect" surface finishes. Four sheets
were produced and these four sheets essentially made up the two hulls. (Wharram hulls are slab sided). The hull
frames were straight edged wood and the sheets were attached using glass and resin. The curved keels were glassed in PVC pipes about 200 mm diameter, which also served as water tanks
. The hulls were built upside down. After inversion, some extra glass was applied to the inside where required. Decks for the hulls were then constructed using the same flat sheet technique.
The company making these hulls did it as a side line from making large industrial/farming water tanks
. The large flat sheets made up the tank cylinders. The reason they used this method was that they could put many flat pack sheets on a truck and then attach the bases on site at the farms.
Wharram hulls don't necessarily appeal to everyone but I am sure the technique could be modified for multi-chine hull
forms. For a multi-chine hull form, bonding at the chine joints may be an issue, but I am sure any reasonably competent glass supplier would have solutions.
for thought. The glass hulls over wooden frames gets around the wood/sea water problem but still allows a wood finish interior
where wood rot
is far less likely.
What this technique does provide is a good water tight hull form along with a perfect surface finish
- minimal sanding
Probably heavier than some other materials, but definitely very much faster and cheaper. Most bridge deck
structures are also flat (ish) so this technique may also be used there if needed.