Team Scarab Multihulls

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Fran Sneesby

Fran Sneesby lives in S.E. Queensland building multihulls for Yendys Multihulls.

Part 1 Starting a new boat

Sunday, December 7, 2008
This is the second Scarab 18 we have built so we already had a frame and plywood templates so we had a good start. The supplies arrived without any great drama. Luckily we have good carriers and the price of fuel is starting to drop. A glimpse outside the shed shows how blessed we are with our location.


The foam was cut to length and joined with polyester resin and aerosil, covered with glass, resin and peel ply. We cover the glass with peel ply to fill the weave in the cloth and make the boat easier to finish. We found it also makes the glass adhere to the shape when glassing around corners.

panel beam

The panels for the mainhull shell and both float shells are finished and cut out using a jig saw with a special blade. We use Makita jig saws and either 42 (flat top) or B21 (shovel top).
One of the beams was also built during this time. When working I like to have as many jobs going as possible to ensure the most efficient use of time and resources.

Total time so far 43 hours.

Scarab 18 folding trimaran Part 2

Sunday, December 14, 2008
One more beam finished (two down – two to go). I’ve been asked to provide more information and more pictures, so here we go. The mould was built using form ply. It is readily available here, is relatively inexpensive and has a smooth surface so the glass doesn’t stick (but plywood will work as well). Pilot holes were drilled as markers for the pins that hold the folding system. The mould was waxed and polished a couple of times. Then mould release was wiped on with a cloth. The pilot holes were blocked with a small bit of filler (resin and Q cells works well).

mould cutter

The glass was cut out using a battery powered cutter. We found this cutter saves many hours and RSI. Because this job is tedious and time consuming I cut glass whenever there is spare time. This might be a job you could delegate to someone who wants to help.
The first layer is chopped strand mat. This gives the finished beam a smooth finish. There are many consecutive layers of triaxial, unidirectional and double bias glass layered, wetted out and compacted.
After a couple of days the beam can be removed after drilling the pilot holes. Because polyester shrinks it is relatively easy to remove. A couple of hardwood wedges and a wooden mallet should do. Epoxy resin doesn’t shrink as much as polyester so you may have to use water or water under pressure to remove the beam.


The main-hull panels were attached to the frame and screwed in place with gyprock (drywall screws). With a plywood boat the panels can be attached using pieces of copper wire.

main hull main hull

All the rest of the panels were cut out.

Total time 82 hours

Scarab 18 folding trimaran Part 3

Saturday, December 20, 2008
Joints on the main-hull were filled, sanded and faired. The bottom three panels were covered with double bias glass cloth over the joints. This provides extra protection if the boat is pulled onto the beach. The other joints were taped with double bias tape. Because the bottom three panels are hard to get to when the boat is upright, they were filled and sanded.

main hull main hull

The main-hull was lifted off the frame and turned over. The boat was allowed to rest on a piece of plywood on the floor eliminating an extra frame. It also makes the boat low enough so it is easy to work inside.
The float frame was set up and levelled. Panels for the first float were attached as the main-hull panels with screws.

Total time 119 hours

Scarab 18 folding trimaran Part 4

Tuesday, December 23, 2008
The first float joints were filled, sanded and faired. The float was glassed the same way as the main-hull (double bias cloth over the bottom 3 panels and double bias tape on the other joints).

float float

The float was removed from the frame and taped inside.
The other float was built on the frame in the same way and glassed outside.

Total time 151 hours