BUILDING HULL BOTTOMS AND COMPOUND SURFACES

Strips of PVC foam with carbon unis both sides as planking for a 42' trimaran hull
Strips of PVC foam with carbon unis both sides as planking for a 42' trimaran hull

The most popular method used in conjunction with panel kits is strip planking, usually with PVC foam planks that have been laminated with a light layer of unidirectional glass or carbon.

The foam panels are joined end to end to the full length of the hull and laminated both sides with the fibres parallel to the length of the hull. Then the panels are ripped into strips of varying width depending on the degree of curvature in the hull. When the planking is completed the surface is faired and a second laminate is applied both sides to complete the structural requirements.

Optional Planking materials:

1. Western Red Cedar

2. Duflex Strips: PVC cores with Hoop pine veneers both sides. More pleasant to work with than glass laminates and doesn't blunt the saw blades so quickly.

We advise against using balsa cores.



OTHER METHODS FOR HULL BOTTOMS

1. Batten mould:

Temporary mould frames are set up and then battens run at approximately 150mm centres.  PVC foam sheets are then laid over the stringers and the skin laminates applied over the external surface after the foam core is in place. The internal surface is laminated after the hull is turned and released from the mould frames.

 

2. Male Plug.

Many professional builders prefer to to build a solid male plug and vacuum laminate over the plug. This method is more attractive if a number of boats are to be built to the same design.

 

Note that both of the above methods require that the mould frames be offset for the thickness of the mould material (the battens in case 1. or the plug planking material in case 2.)  as well as the actual hull planking, whereas for strip planking the mould frames or permanent BH's in the setup are only offset for the hull planking.

This needs to be considered when ordering plans.

Foam Sheet Planking
Foam sheets over a batten mould for a Barefoot 40 Catamaran.