Aquamarán

Birth of an idea:

The idea behind the concept of the aquamarán stemed from an unpleasant experience during one of my journeys into the sea alone. I wanted to test my kayak handling waves and all went well while I was tracking against the waves head on. But I needed to return to shore, and while turning the kayak a wave caught up with me before I could turn it completely. The surf caught the kayak and pulled it from underneath me violently even taking away my paddle. The wave took the kayak away from me about 20 feet, so I rushed into catching up with it. I finally grabbed one end of the paddle and climbed up as fast as I could. While getting ready to paddle again to the shore another wave hit me and again pulled the kayak from beneath me, only this time I held on to the paddle which was tied with a leash to the kayak and that made the difference since I was already too tired to swim again.

This experience taught me a lesson: a kayak is not meant to handle surf well. So I decided I needed to do something to improve my chances when in rough waves (5-6 ft). This is why I built the catamaran accessory for my kayak which we called the Aquamarán.

Design:

My kayak is a 2013 Wilderness Systems Tarpon 140. One of the features of this kayak is the SlideTrack which runs on the sides of the pilot and on the sides of the cargo area behind the pilot. I decided to build my design using the these tracks. I had to create custom nuts to tighten it up using an aluminum flat piece 3/4"width. I tapped it with a 1/4"-20 tap to use 1/4" SS screws to hold the Aquamarán to the kayak. Based on the above experience I selected the following design criteria:

1. Be as light as possible
2. Provide as much buoyancy as possible, allowing to add even more weight to the kayak cargo area
3. Provide as much stability as possible, allow an adult to stand up in the kayak while at sea with as less effort as possible
4. Create as little drag as possible
5. Be as sturdy as possible, resist an adult climbing through it onto the kayak
6. non-functional requirement: Look Good!

After measuring the kayak and entering it on a CAD program these where the dimensions I got for a six feet wide catamarán:

Result:

I ended up using galvanized steel 3/4" squared rods for most of the frame mainly because of its availability and price. I used 1" galvanized steel plate 1/4" thick for the plate that holds the pontoons screws and the plate that holds the frame to the SlideTrack. Being a prototype this resulted in a surprisingly lightweight and sturdy frame to attach the pontoons. The pontoons are made of PVC tube 4" in diameter, heat molded to provide as less drag as possible. These are sealed with liquid foam and the ends are epoxy sealed. Even though each one is 5 feet long, they are surprinsingly lightweight as well.

The whole Aquamarán sits just a few inches above water level when the kayak is not occupied and barely touches the water when occupied. This was essential to limit the drag on the kayak.  The prototype result is shown in the following video.

Next Steps:

The next steps include:

1. Determine how to mass produce the pontoons
2. Build the frame using aluminum or stainless steel
3. Add a sail to the frame to provide thrust in choppy waters
4. Design frames for other models of kayaks