Introduction: 24 Foot Sailing Trimaran

About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific I…

Indonesian style, built out of recycled stuff.
Here we are busting out through the surf in 30mph winds at Stinson Beach California on the maiden voyage. The boat works great! There are no swimmers or surfers out because of the rough conditions. The kids are on the beach making forts out of their boogieboards instead of surfing.

Hull Length 24 ft at deck
Hull 22" wide amidships at deck, 18" wide inside hull (there's a wide lip at deck)
Hull 24" deep amidsnips. The hull round bottom is a semicircular arc of 8.25" radius.
Hull rocker is about 4" measured from points 16' apart.
Outrigger crossbeams are 14' 7" long 3.5"x2.5" fir beams tapering to 3x2.25" at ends
The outrigger floats are 4.5" diameter, 19 feet long with foam plugs in ends. ~134lbs buoyant.
The plugs in the front of the floats are shaped into a nose that protrudes 6.5" more.
1.5" diameter stainless steel tubing connects the crossbeams and floats.
The Sail is an 8 sq. meter crabclaw / leg-o-mutton sail on 14ft. windsurfer masts.
The mast is supported by three stainless steel cable stays.

Total cost of materials was $200 or less.
The outrigger floats are fiberglass chemical pipes full of empty plastic soda bottles.
The main hull is made from a pair of old 16' catamaran hulls cutoff and glassed end-to-end.
Junked catamaran hulls are easy to get. If you can't find a free hull, build a hull like the Kenya Canoe but bigger. Use scavenged plywood from crates if you want it free.
The wood for the crossbeams came from a big pallet, with the nails and crossboards pulled off. Then I scarfed them together for extra length.
The sail is blue tarp on windsurfer mast spars.

Great action photos by kenny

Step 1: Beaching After the Maiden Voyage

Star, Damon and myself rode the boat in on the back of a big wave, just like the Malibu Outrigger manual recommends. Then we carry the boat up the beach. The sail helps us and we scamper up the beach and get clear of the break zone before the next wave hits. What a great boat.

Unlike trials of previous boats in Mexico and Kenya which got badly damaged by surf landings, this boat is fine. It helps that there's a lot of wind and the boat is faster than the waves.

Step 2: Cartopping

Here it is on top of the ugly truckling.
It assembles quickly without tools. The main hull is the heaviest part, about 90 lbs. It takes two people to lift it onto the roof rack because it's so big. The other parts are a lot lighter and one person can handle them.
4 or 5 people can ride in the cab of my truck. The boat could carry that many also, so it's a good match.
We could only get three people to volunteer for the maiden voyage because the conditions were so rough, but there was room for more.

Step 3: Or on a Trailer

To launch it from a trailer, you drive to the boat ramp, assemble the boat while still on the trailer, then launch and land it in the usual way.

Step 4: Inspiration

I once tried to sail to Cuba in an outrigger canoe.
There were some problems. When I was almost to Havana my rudder broke so I couldn't sail, the current carried me away, I was caught in a storm, etc. etc. I spent a lot of time trying to not to die and hallucinating from exhaustion.
I also spent a lot of time thinking about the perfect hull shape for a sailing canoe.

In the following year I traveled to Indonesia and Papua. I learned a lot by gaping at and measuring sailing canoes there. Here are some Makassarese (Sulawesi) canoes I saw in Jayapura Harbor, Papua.

In severely technical terms, here's what I was looking for in a hull:
1) High prismatic coefficient (fat ends)
2) Round bottom
3) Straight sides in the middle
4) Just the right amount of rocker. Curved like a banana.
5) A beam to length ratio of around 12:1

Step 5: Cut and Paste Catamaran Hulls Together End-to-end

I found a pair of 16' catamaran hulls for sale on craigslist that were exactly what I was looking for.
By no coincidence, they were designed and built by Karl Westbroek, an engineer from Malang, Java, Indonesia. They were a nice bright yellow that emphasized their banana-like shape. Hence Karl's original name for his catamaran, "Bananas".

I wanted my hull to be pointy at both ends. These hulls had square transoms at the stern.
So I had to cut off the sterns and butt up the pointy ends to make my hull.
To figure out the right place to cut them I slid a piece of paper over the hulls to find a special transverse curve called the "Geodesic". That's the shortest path between two points on opposite sides of the hull. I cut the hulls, butted them up, and checked to make sure the keel and sides met at a reasonably fair curve.

Step 6: Thinning the Edge

Before we can start glassing, we need to grind down the existing fiberglass so it's a smooth transition.
Michael Kearney helps me out by grinding the edge thin on the inside of the joint.

Step 7: Jigging It Up

Next we clamped and screwed a bunch of sticks to the outside of the hulls to hold them in alignment.
Jrlee checks that the decks are parallel.

Step 8: Glassing

Jrlee mixes some epoxy. We cut and lay out strips of fiberglass cloth on a piece of plastic on the deck. We soak the cloth with epoxy. We layup the glass into the hull, squeegeeing and painting the epoxy so the cloth is fully saturated. The wider strips of cloth go over the narrow strips, so the rough edges of the cloth aren't exposed.

Step 9: Rough Fairing

I mix some glass microballoons with epoxy and slather that all over the outside of the hull.
When it sets up I grind it flat with a sanding disk. While I'm doing that Danny comes and suggests a better way.

Step 10: Rapid Fairing

He's glued a board to a sanding pad and glued a full sheet of 80 grit sandpaper to that. He creates an artificial snowstorm while sanding the hull, and in a few seconds it's smooth and faired. Wow.

Step 11: Glazing and Finish Sanding

Next I squeegee some body putty over the nicks and imperfections. When that's dry I wet-sand it with a sanding block.

Step 12: High Build Sanding Primer

Next come a couple of coats of fast-dry high build sanding primer, then some wet-sanding with a sanding block, and finally a coat of yellow paint. The hull is all one hull now.

Step 13: Outrigger Floats

A friend gave me some fiberglass chemical pipes. They are 19 feet long and 4.5" in diameter.
I would have been worried about the chemicals but the pipes were brand new.
Actually they might be intended as covers for glass pipes.
I tied strings to the necks of some 2 liter soda bottles and shoved them into the pipes. The string is to keep the bottles from floating away in case of a disaster.
I carved some minicel closed cell foam to make plugs for the pipes. I shaped the front plugs into the noses seen here. The flat front feature is like the "manu" on the front of a Hawaiian canoe. As it plows into a wave, it sprays the water away forming a giant air bubble around the float. The bubble rises through the wave, pulling the float up with it.
It works really well.

Step 14: Float Blocks

The outrigger floats are 4.5" diameter fiberglass chemical pipes.
I made some wooden blocks to rest on them. They will be the "feet" of some short legs made of stainless steel tubing. Those in turn get connected to the crossbeams. Just like Ezekiel, the foot bone's connected to the leg bone, the leg bone's connected to the thigh bone.

Here I am testing the first block I made to see if it fits the pipe right.

Step 15: Cutting Curved Grooves With a Tablesaw

I setup my ghetto tablesaw, which is a circlesaw screwed to a board.
Yes, it's very dangerous. Don't do it.

I set up the fence at an angle to the blade.
I made a lot of cuts of increasing depth in a block of wood until I had a nice round trough cut in the bottom of the block.

Step 16: Wooden Shoes

Then I repeated the process on some narrower blocks, cut holes the right size all the way through with a hole saw.

Step 17: More Wooden Shoe Cobbling

I glued a wooden disk in the bottom of the hole so the tubing leg wouldn't touch the float directly.
I heated up the block to cure the epoxy quicker. Don't breathe those buttery fumes!
When the epoxy was set up I shaved the protruding plugs off with the tablesaw.
I drilled some lashing holes in the sides of the blocks and cut the corners off the ends so they would enter the water better.

Jumping ahead, let's go sailing and I'll show you how this stuff turned out.

Step 18: Hot Spring Break

Star organized a trip to a hotspring on the coast that's only exposed at the lowest tide of the month.
We camped nearby on friday night, woke up at 5 am to hike down. It's pretty amazing. There's a main pool and also a cave full of hot water that goes back into the cliff face.
We relaxed in the hot spring until the tide rose and waves of cold water started washing into the spring.

Then we hiked back up to the truck and it was time to put the yellow canoe in the water.
So we drove to Stinson Beach and parked as close to the beach as we could.
We unloaded the canoe parts onto the grass in the park there.

Step 19: Lashing It All Together

We swarmed over the canoe, lashing all the arms and legs to it with bicycle innertubes.
The front beam takes most of the load, so it has a double tube 'H' shaped stainless tubing leg that connects the beam to the float. The foot of the 'H' rests in sockets in a wooden block.
The bottom of the wooden block is carved to fit the top of the float tube.
The float is lashed to the block with spectra string and innertube. That part stays lashed permanently.

Step 20: Carry It to the Beach

We had plenty of help from relaxed sleep-deprived pals from the hotspring trip.
When it was all tied together we picked it up and carried it to the water.

Step 21: Please Return!

In case something went wrong and we lost the paddles we wrote plaintive messages on them in hopes that someone would return them. These are instant paddles made in a few minutes from a hockeystick, a board and some string, but they're so nice it would be a shame to lose them.

Step 22: Farewell Hugs

The wind had increased to a gale. The sea was rough.
Time for farewell hugs!

Step 23: Raising the Sail

We hoisted the sail and watched the waves. The surfers were all on shore so we couldn't use them to judge the size of the waves. But at least we didn't have to worry about hitting them.

Step 24: Launching!

Star, Damon, and I carried the boat to the water just as a big wave washed ashore. We jumped on, sheeted in the sail, and started paddling at the breakers.

Step 25: So Far So Good

The boat took off like a racehorse. It's easy to steer with a paddle. It goes to windward just fine.
We sped toward the outer break. Wait a minute. That's a big wave coming!

Step 26: What's Going to Happen?

We hit the wave and there was whitewater everywhere. We kept going through it, and when we could see again we were still moving fast and there was hardly any water in the hull. The boat works in surf!

Step 27: Sailing and Landing

We sailed around until one of the lashing buttons broke, then decided to head back in.
We surfed in on a wave, outran it, and executed a perfect landing on the back of a wave.
Jubilation! The boat could have handled more passengers and rougher conditions.

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