BALSA CORE and FOAM SANDWICH
Balsa Sandwich Technique involves the use of
a frame and batten mould and balsa sheets of approximately 16" x 3 are
sewn into the mould. The outer skin is laid up over this. The balsa comes in approximately
2" square blocks which are glued onto a scrim to make up the 16" x 3
panel.The balsa is
quite flexible and lays around most compound curves without giving any unfair surface.In
general balsa is limited to use above the water line although we do extend the balsa down
to the cabin sole,cheap foam is used during the laying up stage and this is later removed
from the inside to give a single skin area below the cabin sole and down into the keel
where the floor will be bonded in.Balsa sandwich generally is
made up in 3/8", ½" or ¾" thicknesses. It can also be two layers of
3/8" with a layer of chopped strand mat between the layers of balsa. This double
balsa technique provides an extremely strong and stiff hull, however, the technique is a
little more expensive than using the single layer of balsa.The inner skin on a balsa
sandwich vessel usually is one third of the thickness of the outer skin. Balanced
laminates can be used but we feel that the extra laminate on the outside is required to
provide the necessary impact As mentioned before the first step is building the mould. How to is
described step by step in the plans. The materials for the mould are quite inexpensive and
second hand timbers are ideal for this purpose. If your lucky someone nearby will be
inspired by your efforts and purchace the mould of you when your've finished to build his
own boat allowing you to recover some of your costs. When the mould is finished the foam
or balsa is attached via stitching , toggling or nailing. The outer laminations of
fiberglass and resin, as per the specification in your plan, are then applied. The hull,
with the mould inside, is then rolled over and set up in a suitable cradle after which the
mould is then lifted out of the hull and once again recycled as After the hull shell has been trued up and the sheer line faired with battens the next stage is to cut channels through the core in certain stress areas. These areas are shown clearly in the plans.Reinforcing strips of extra fiberglass are layed in these areas attaching to the outer skin. The whole of the interior is now laminated with the inner layers of fiberglass. Bulkheads and solid floors are now installed as per the plans. You can how proceed to start on the interior fitout. |