Sail Fail - Sort of

Introduction

This week project involved the addition of a sail to the Aquamarán. The idea behind the sail is to provide additional means of propulsion when kayaking out at sea. Now that the kayak has been stabilized with the pontoons the only other thing that I think is missing is a way to improve the propulsion when doing long kayaking trips out at sea.

After seen a fair amount of videos on the internet about what people do to kayaks I discarded the gas motors because it is a noisy and messy addition to the kayak. Another option is an electric trolling motor, but it seems to me limited in terms of battery life. I finally decided that a sail could provide adequate propulsion specially on open waters which is my target medium. It is completely clean, doesn't add significant weight to the kayak, and has potentially unlimited energy resources available.

Design

I watched as many ideas as possible on the Internet on how to build the appropriate sail for the kayak.  I decided that the new windpaddle type of sail weren't good enough since it works only when "running" i.e. going in the same direction as the wind. So I decided to build a more typical type of sail. I wanted the sail to be on the same frame I built for the pontoons.

I selected "ballistic nylon" which I found on a local fabrics warehouse because of its strength and impermeability. To provide the internal rigging of the sail I used remaining carbon rods I had from a camping tent, (these are the ones with a bungee elastic inside). I wanted the look and feel of the sail to be that of a fish dorsal fin, so I used two reinforcing rods. The mast was built using PVC tube schedule 40 of 1" diameter. The horizontal support was built using 1/2" PVC tube. For the base of the mast I used a concoction made out of plumbing PVC parts. The base is essentially a toilet flange of 3" with a reductor to 1-1/2". Inside the reductor there is another reductor to 1-1/4" and a 6 inches long piece of 1-1/4" PVC schedule 40 tube. All this makes a sturdy base for the mast which easily rotates when inserted because the 1" tube fits snuggly in the 1-1/4" tube.

The mast has a cross tee union that provides two lateral sockets. These were intended to provide some sort of handles to be able to change the position of the sail while sitting in front of it. The end result looked good and is easy to assemble.

Performance

Unfortunately the performance test wasn't good.  I struggled to find the best orientation of the sail mainly because being behind me I couldn't see how the wind was affecting it. The sail did picked up the wind but only when running in favor of the wind. Even then I found it hard to control the direction of the kayak using the rudder. I think that being on the back of the kayak the force exerted by the wind on the sail worked like pushing a pencil on the tip. The front of the kayak "anchored" to the water rendering the rudder ineffective for steering. 

On the good side the overall size of the sail did not affect the stability of the kayak. Maybe this is part of the reason the performance was so poor, but it seems it is one of the good aspects of the design. 

In conclusion, I am planning of relocating the sail on the front of the kayak were ironically visibility of the sail is important to its control. I will also consider using a different material and sail design, something more lightweight than the ballistic nylon. We'll see. 

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