Building a Sailing Trimaran - Page 2

Here are the panels for the floats. I deviated from the plans here to make the entry of the bows more curved and gradual, instead of the abrupt and blocky shape shown in the plans. My hope is that they will handle better in rough water like I'm probably going to experience at the coast. Instead of digging straight in to oncoming waves, these might glide over top of them.

These are the internal bulkheads for the floats. These are also not all cut to the plans, because I widened the gap between the two middle bulkheads for each float to allow room for a centerboard trunk and centerboard to be placed in each one. This gets the messy leeboard the plans call for off the center hull, and they will actually allow me to sail closer to the wind. When sailing at any angle other than 90 degrees off the wind, the submerged areas of the two boards will actually add together to decrease the boat's tendency to slip sideways (more underwater lateral resistance means less leeway.)

The bulkheads each get limber holes cut from the bottom corners, and the two aft and forward bulkheads get large ventilation holes. The two center bulkheads do not get ventilation holes because they will actually form the aft and forward edges of the centerboard trunks. All the bulkheads get blocking around the sides for attaching the panels during construction. Also, the stems are cut out from 2x4 lumber with the table saw.

The gunwales for the center hull run the length of the boat, so they need to be almost 16 feet long. Since high-quality lumber is not available in this length, scarfing will be necessary. Here, I take 3 pieces of 8-foot select pine, cut a 9 degree bevel on the ends with the table saw, then epoxy them together. Counting for the overlap, this leaves me enough material to make over a 20-foot gunwale if I want to...

A round cutout for the forward hatch. This will be the only store-bought hatch in the boat, and is the round "turn to lock" variety seen on many homemade boats. The hatch is offset slightly to starboard to allow for it to be easily opened when the mast is installed.

The sides of the floats are temporarily screwed to each of the four bulkheads. When they are glued together, these screws will serve as cheap "clamps" that will hold the pieces in place.

The sides are now epoxied to the floats, and the gunwales are clamped in place so they will hold the correct shape while the epoxy hardens. The gunwales will actually be attached once the bottoms are on and the outside is fiberglassed.

Gunwales cut and epoxied to the main hull. Those beveled wood strips are under a lot of tension, so we need LOTS of clamps.

All we can do here is pray the epoxy hardens correctly and the gunwales won't fly off as soon as the clamps are removed...

There I am making some minor adjustments. There's a whole lot of wood planing involved if these don't get glued in the right spot.

The gunwales are attached nicely, and the excess has been sawn off at the stem and stern.

Now, back to the floats for a little while. These are the bottoms, which have been cut to shape by laying the plywood board on the bottom of the now-epoxied floats and tracing out the shape. The bulkhead locations were marked on the sides of the pieces, so from that information I could cut out the slots for the centerboards. These should pivot down neatly between the two center bulkheads when it's all said and done.

The bottoms are stitched in place on the floats. This will hold them in place for filleting with thickened epoxy later.

The aluminum mast and boom also arrived today, and since the mast is 18'6" long, it had to be delivered via freight carrier on a tractor trailer. Here is the mast, running almost the entire length of my garage.

The bottoms are now filleted in place and the wire twists removed.

More filleting all around the insides of the floats. Now the insides are totally sealed up.

Framing sticks around the edges of the side panels for the centerboard trunks. These will be epoxied between the two center bulkheads in the floats to provide watertight slots through which the centerboards can pivot.

The framing sticks are set in place, and the centerboard trunk sides are much more rigid.

Filleting around the insides of the framing sticks to make them hold on tighter.

Fiberglass for "outer" sides of the centerboard trunk pieces. Since these will be exposed to water when the boat is in use, I want them to have the same abrasion resistance and protection as the rest of the hulls. Also, since the centerboards will be pivoting up against these, I don't want the pivoting motion to wear away at the wood.

Fiberglass for the forward and aft sections of the centerboard trunks (also serving as bulkheads), so the pivoting centerboards won't eat away at the wood here either.

Now the epoxy and fiberglass on the centerboard trunk sides has hardened and the excess is cut off.

They are sanded a little to rough up the first coat of epoxy, and another coat is added for a more glossy finish. I'll let that harden here on the floor.

Meanwhile, the forward deck support stick is added. It's beveled 23° on each side to allow the peaked decking to sit flush when it's glued in place. Also notice the notch on the starboard side of the forward bulkhead upper framing stick - I had to chisel this out to allow for the screw and nut that hold the forward hatch in place at this position.

Here are the pieces of 1x10 pine shelving board I'll use to make the centerboards. They will be rounded off on the tops and bottoms, and a diagonal lever piece will be joined on using wood dowels in the holes you see on the side. With the dowels and thickened epoxy in place underneath a protective layer of fiberglass, these should be as strong or stronger than a single piece of wood.

The insides of the floats get a coat of epoxy throughout for waterproofing. You can see my newly epoxied and hardened centerboard pieces leaning on the floats to the right.

The insides of the centerboard trunk side pieces get an epoxy coating too, but it's easier to do this before they're installed in the floats.

The forward decking support piece is glued in and sanded flat, and gets another coat of epoxy all inside to provide a smooth, watertight compartment. This will be ready for the decking to be glued in place next.

Here are the centerboards again. They look a lot like pieces in the video game Tetris right now, but you will soon see their true shape...

Half of the forward decking is screwed in place. So far, we fit very snugly with the gunwales and forward decking support.

All the decking is screwed in place. Now, the excess overhang on the sides can be traced out with a pencil and cut off for smooth side lines.

The forward decking gets fiberglassed on the underside for a little more strength and to provide a strong surface for through-bolts and nuts to grab onto. Lots of things get attached to this deck, and I don't want any of them being ripped out at precisely the wrong moment.

A look from inside the forward compartment back toward the stern. I'm taking this picture now, because once it's sealed up, I won't be able to really see inside there any more.

A view from inside the forward compartment looking forward toward the stem.

Close-up picture of the stem. Once the decking is in place, I'll need to know where I'll have wood and material to screw the stem fitting in to.

Now the forward decking is epoxied in place, using just a few clamps.

The aft end is held down using a 2x6 piece of scrap lumber and a box of screws.

Now the epoxy has hardened and the decking is locked in place. Here's Jack admiring my handiwork.

The floats now get the centerboard trunk sides epoxied in, with screws holding them in the right place. At this point, both floats now have through-slots that are totally sealed off from the inside, except for two holes cut for the bolts that will hold the centerboards in place.

A downward view through the centerboard trunks. Hopefully these will stay watertight!

The crossbeams ("akas") are made from 10-foot 2x4 douglas fir lumber. Douglas fir is light, strong, has good rot resistance, and is slightly pinkish in color so it will match the finished decks of the boat. Here, I have planed a slight bevel from the center outwards on each end of the boards. This taper will reduce unnecessary weight and look stylish when the boat is assembled. Also, one of the centerboards has been cut to shape, and here I test its fit in the centerboard trunk of one of the floats.

The deck coaming is installed on the main hull and epoxied in place.