Kayak to Trimaran Conversion

After seeing snippets from the WaterTribe Everglades Challenge I knew I wanted to build a small trimaran. I go sailing with friends in the Narragansett Bay often but I don't have a sail boat and have never been a "sailor". I've always loved the trimaran styling and figured that if I ever got a sailboat, that would be the route I'd go.

A couple years ago I purchased a windsurfer 2nd hand and gave that go for several summers. I could get around my local cove - and I loved the feel when the wind caught it... but I just couldn't get proficient with it. After the mastfoot broke, I decided I would try to get the sail mated with my 16ft Old Town kayak.

The proof of concept "worked" but I quickly learned that 1. Kayak didn't have a keel and 2. There just was no way to safely balance the boat when it the sail caught wind.

So, the plan was put in action. I would make amas for it and device a plan for a keel.

 

As I thought about the keel it bothered me a lot. I didn't like the idea of leaboards (probably the most practical for a kayak), nor did I want to make any permanent change to kayak, which pretty much eliminated daggerboards or keels.

I thought, why couldn't the amas have keels on them?

And then I thought, why couldn't the amas ACT like keels? So armed with enough experience and knowledge from building RC airplanes and having a passible idea of how airfoils worked, I embraced this idea more.

So what I came up with is an ama that is designed like a flat bottom airfoil (AG35 is what I came up with) with the flat bottom facing away from the main hull. The mental gymnastics went like this:




As the boat is pushed to the side, the leeward ama would act like a snow plow, giving resistance and persuading the boat to move more forward than downwind. Additionally the airfoil shape would be lifting up (if dipped over far enough) and windward (giving a righting moment beyond the buoyancy of the ama)

 

As is obvious by the images previously posted, I made the amas out of foam (8ft long) and covered in fiberglass and --- wait for it ---- Polyurethane.

Why?
Well I wanted the foam to be protected, strong and rigid. But polyester resin would eat the foam. Polyurethane ended up being super easy to work with - and while I would go with Epoxy for a longer lasting more professional result, for a quick and dirty (and cheap) alternative this was fine and has lasted two outing so far. If a I get full season out of the amas next spring/summer I will be happy. This has all been a learning experience and proof of concept.

Also used Bondo for filling and shaping the bows. I had to be careful about applying too much (again it would eat the styrofoam), but it worked out pretty well. Where the amas would attach to the akas I fiberglassed in wooden blocks.

 

Attaching the akas to the main hull of the kayak was another challenge - one that I absolutely love how it turned out. The challenge (again) was to not make any permanent changes to the kayak and what was born was system that is not only convertible, but converts very quickly (5 minutes to setup, 2 minutes to take down). No tools, and no permanent changes.

The front aka mounts to a shaped board that attaches via rope. The rear is a board that clamps to the gunnel in the cockpit.

The front takes advantage of loops that were installed so items could be bungee-corded to the top of the kayak. I 3d printed a couple of clam cleats for quick attachment and removal.

 

I had originally thought that I would attach the amas to the akas with bolts. But the PVC 90 degree angle doesn't have enough overlap to be able to do this. So instead I went back to the rope idea. A short piece of rope is knotted inside the aka and after attaching the PVC connection I have a small hole in the connector that I can thread the rope through and back to the aka where another clam cleat is is installed. This basically ensures the pipe used for the aka is stays snug in the connector attached to the ama. Sorry I don't have a picture of this. Suffice to say it works really well and again no tools are necessary to put it together - and it dissembles in seconds.

What I learned after the first 2 outings sailing the kayak is that keeping the mast stable and rigid is critical. I added rope to rig the mast. First just to the bow. That made a major increase in performance. Then added rigging to the sides of the mast and got an equal jump in performance. I have put the boat up for the winter, but in the spring I'm anxious to try my new mast tension plate and collar that I 3d printed.

 

thanks for letting me share