Category Archives: Trimarans

23′ Trimaran Update

I finally got the first run of modeling the updated 23 daysail trimaran. Version B will have ama rudders and the even hotter version C will have foils. It is a developed plywood/epoxy unit with core vacuum bagged onto the flat surfaces needing that. And carbon fiber where it helps. At around 360 kg lightship weight, it can be built for around $5000 us in construction materials. The connecting beams should be carbon mast sections. The camper version comes next.





40′ Performance Trimarans

One of the guys from Steamradio just had a 40’ performance trimaran designed by Shuttleworth. I was surprised how much it resembled a study that I did for Phil Steggall a few years ago. It didn’t get built and I forgot about it. It is almost the same sailor use program. And it was based on improvements to my 40’ tri, the Geko. The Geko was optimized for singlehanding and light weather. The two trimarans above are for more wind than Geko usually found.


The beams are not swept forward on Phil’s boat. I asked multihull engineer and composites god Ronnal Reichard about that. He declared it an inefficient idea as it introduces an added twisting moment to the main beams. He dismissed the advantages of helping the ama bow as the ama has much more section property to work with, to ease that stress.   The tri had square L/B design of course.
It has been suggested that swept forward beams keep the weight of the beams forward. The vast majority of the bending load, and thus the laminate, is near the middle and aft.

The biggest improvement to the Geko would have been adding the flare to the main hull. Any crew or guests need to toss their bags and foulies somewhere, out of the middle. I forgot about that. I thought everything else worked pretty well, for a shorthanding fast 40’ tri.
Boards in the amas solves the board intrusion in the main hull, but if short tacking, one needs a crew or it is more difficult to tack smartly. I wanted smart tacks on the Geko.  Not everybody has to short tack all day in light weather.


Where to helm from is an interesting exercise. And I found that it is most dependant on the crew or lack of. Reflexively, everybody should be up on the high side. These boats typically have almost deck sweeping mains, and are doing twice the speed of anything else out there. Anything could be happening behind that main. I always ended up in the cockpit, down low, so that I could see traffic approaching from the low side, helm in one hand, and mainsheet in the other.

13939350_10154467187463628_6421360100843937345_nWith a crew, that is not a problem, but where to steer from depends on how much the helm (owner usually?) trusts the mainsheet trimmer. I pretty much only trust myself when it’s gusty, unless Dave Calvert is crewing….
Is that a pair of main winches I see on the top view on the back beam? That suggests it’s optimized for at least double handing or a crew then. Double handing I was told.


the Shuttleworth tri

It’s all very interesting, imagining how design affects life blasting upwind.  And the interesting ways that a design can be fitted to the owner’s individual needs.

More R2AK in Seattle

This Melvin and Morelli tri was hauled out recently in Seattle. It is intended for the R2AK race this summer.
I understand that it is all carbon fiber, which can make it light. And the amas look full length, which is good.

Now, I am assuming that the first 3/4 of the race after Victoria will basically be like sailing in the San Juans in the summer.  Light, shifty air.  Short tacking, and again, and again.  Through kelp beds.  Crew on the leeward side to drape some shape into the jib and pull the wider main hull out of the water.

If I may, those amas look to me like they were designed for tradewind conditions, not 4 knots true.  They look like they were designed by someone who had never sailed in the San Juans in the summer.   The fat waterplane down low is draggy in light wind.   And why don’t the amas join at the inboard side, instead of the middle.  That would save weight and make the beam and the join stiffer.

I would offer them some improved amas that would increase light weather speed compared to these.  They could slide right on, and even improve the BOA.  I won’t hold my breath.  With the MM plans costing 10 times what mine do, they surely have Stockholm syndrome and will ignore the physics.





“the Making of Sumo” Picture Sequence

I had not before seen this sequence of pictures of the making of Pat LeMehaute’s KHSD 37 trimaran at Islamorada, FL.  The link is only on Face for now so you have to be from there to see it.  Foam/glass.  What an amazing job.

OK I find that none of the Facebook links work.  Will see what I can do to get the sequence here.  Kludge would be to go to Pat’s Face page and find the albumn.1931459_100834349939918_2630693_n


32′ Trimaran Runabout

I went rogue on a 32′ power tri runabout design. hope customer likes it. communication difficult on the road here.  Foam/glass.  30 hp gives low 20 knots empty and 45 hp full load.

Tried to make a radical look functional.  Opening doors on each side of cockpit.  Steps are aft to motor.




38 Power Trawler

I finally got my first pictures of the actual KHSD 38 power trimaran trawler completed.  It is for sale for a crazy low price. Construction looks great. The amas look way too small to me. In the design, they go up to the underside of the cross tubes and have rounded deck. An easy fix that one is.  New versions of it have even bigger amas, though friend Steve Scheidler crossed Pacific in about same size boat with same size amas as designed. 

And I had the motors on the sides of the main hull so it could turn in its own length.

Scroll down the page and turn down your speakers. I could not grab any pictures from it.