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By Tom Raidna - Wake Forest, North Carolina - USA

 

When I decided to build my current boat, I did not set out to build a trimaran, but rather I had some specific criteria that I wanted and needed to meet in a sailboat. (1) it could be car topped (later this requirement changed), (2) didn’t require a motor (3) could be stored in the 2' x 3' access to the crawl space under my house, (4) It could be managed by myself. It turns out that the answer to these was the Jim Michalak designed Trilars.

The Trilars is a 15’ trimaran, whose main hull can also be used as a double paddle canoe. The sail rig consists of at set of 2X4 cross braces (akas), 12’ floats (amas), mast, sail, rudder and leeboard. The boat can be disassembled and transported on a roof rack or utility trailer. It can also be trailer in its assembled state. All can be done single handed. In order to build the Trilars one needs to purchase two sets for plans (supplied by Duckworks of course) the Larsboat plans (main hull a.k.a. the vaka) and the Trilars sail rig which includes the details to build the floats and cross braces (amas and akas), rudder, leeboard, mast and sail. The cost of these plans together is less than half that of other trimarans the same size.

The boat is built using the stitch and glue method for the Larsboat main hull and amas. Leeboard, rudder and other sail rig parts are made from ¼ and 3/4” plywood, the mast is made from 10’ and 12’ 1x3 pine and boom was cut from a 10’ 2x4. Provided here is a high level look at this boatbuilding method another great article on this topic is Gary Blankenship’s article of building a Wooboto.

Building the Larsboat Hull

From the plans the bulkheads and temporary forms are measured and cut out of ¼” plywood. Then framing sticks are glued along the edges. The hull sides, bottom and bilge panels are lofted on to two sheets of ply which are coupled together with a 3” wide butt strap (I piece of ply glued to the sheets set end to end). Once the panels are cut out you end up with a set of parts that looks like a boat kit.

The sides, bilge and bottom are attached to the frames and bulkheads, nailed and glued with thickened epoxy.

The panels are stitched together then seems are filled with thickened epoxy and covered with fiberglass tape soaked in epoxy, both inside and outside seams.

A layer of fiberglass cloth is applied to the bottom, followed by a couple of coats of epoxy mixed with graphite for extra abrasion resistance.

The rear deck is attached with caulk and screws, the front deck is set up has a hardtop convertible. Note the screw out port to allow access to the rudder hardware under the rear deck.

Finally primer and paint and you have a boat.

Making the Sail Rig

The sail rig consists of basically five components, rudder, leeboard, cross braces, floats and the mast, boom and sail. Each is described below:

Rudder - the rudder is set up to be a kick up style. It is composed of the rudder cheek, the rudder blade, a set of standard dinghy pintles and gudgeons and a push pull steering stick. The blade and cheek are made from layers of ¼” ply glued together. The blade is the feathered to produce an efficient profile. The rudder blade pivots on a bolt that passes through the rudder cheek. The push-pull steering stick is attached via an eye bolt and wing nut from the control arm thorough a hole in the stick.

Leeboard – the leeboard set up is very simple, extra blocking is attached to the side of the main hull. A pivot bolt is inserted from inside the hull, through the blocking and leeboard. The leeboard guard is bolted to the gunwale and stops keeps the board vertical when there is lateral pressure while under sail. I added a releasing cam cleat to the top of the leeboard guard and a small diameter rope is tied through a hole in the leeboard and is held fast by the cleat, this keeps the leeboard from floating up.

Akas or Cross Braces – these are made from 8’ 2x4 studs. The front brace is built with a cradle to fit the front deck and ¾” blocking on the ends. The rear brace fits on the rear deck and the blocking is in the section that sits on the deck. Both braces are bolted to the gunwale which is double thickness at the connection points.

Amas or Floats – These are built up with the same basic steps as the main hull, except with a square cross section with the ends pulled together and slightly upturned at the bow. A set of frames are cut with ¾” framing, sides, bottom and deck are nailed and glued to the frames. Seams are filled with thickened epoxy and reinforced with fiberglass tape and epoxy. A 1” x ¾” sheer strake is added so the deck can be caulked and screwed into place. The strake is doubled up where the bolts for connecting to the akas will be used. Two screw-out ports are used for ventilation. Finally sanded primed and painted.

Mast, Boom, and Sail

Mast – the mast in the plans is 16 ½’ long and roughly 2 ¼” in diameter at the base tapering to 1” at the top. It is made from 3 layers of 1x 4 glued together then planned to the specified thickness. I was satisfied with the basically round shape I was able to achieve with a hand plain, there are lots of other ways this could be done. (Fancy sanding devices with a drill, using a table saw to make an octagonal shape, birds mouth etc.) Mast step and mast partner from ¾” plywood, primed in grey in picture below. I made the 10’ by 1 ½” square boom by simply cutting down a 10’ 2x4.

When I first built the boat I had purchased a used sail (International Penguin) on ebay. It worked well and I needed to make the mast longer than the one provided in the plans. I probably could have made it even longer for better head clearance. This past summer I made my first polytarp sail.

I would say the main hull could be built in 60 to 100 hours based on the skill level of the builder and the level of finish. 40-50 hours for the sail rig. For me this period of time took 4 years, but we also moved twice along with a lot of other “excuses”. That does not include sail making time, I purchased a sail on eBay, later I made one of white polytarp, as the cost of a new sail is a bit painful.

Building a Trilars could probably be done for as little as $300 if using standard lumberyard/home improvement store grade materials (luan or BX plywood) and Fiberglass Resin. I imagine using marine grade Okume or similar and epoxy could double, triple or more the cost – the decision of what materials to use is an age old debate, and you can find opinions all over the internet. I used Luan ply and epoxy. I had some problems with the Luan on this boat, and I didn’t with a Toto canoe I had built some years back. It seems the quality can be hit and miss.

For additional information and pictures of the Trilars see the
Trilars homepage at http://buildboats.com/trilarshome.html

Also see the Small Trimarans website: http://smalltrimarans.com/blog/?p=1637

And, Issue #64 of the great magazine Small Craft Advisor.

Plans here on the Duckworksbbs:

Larsboat (main hull):

http://www.duckworksbbs.com/plans/jim/larsboat/index.htm

Trilars (sail rig):

http://www.duckworksbbs.com/plans/jim/trilars/index.htm

*****

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