CatamaYak: How to Build a Kayak Catamaran

We happen to own four identical kayaks, we bought the Equinox 10.4 kayaks at Costco, and we started working on ways to hack them to make them even better! First, I hacked a motor onto my kayak, and then I thought I’d give it a shot and see if we could build a catamaran out of a couple of em.

The CatamaYak Concept

When we go out on the water there is usually a group of us. Some are faster than others, and some just enjoy a leisurely time on the lake. We wanted to be able to turn a couple of kayaks into a floating relaxation station and give it a motor so that a couple of people could simply sit back and relax while still being able to tag along.

The CatamaYak needed to have a few important characteristics:

• be light and easy to assemble at the lake
• be extremely waterproof and not get slippery
• be durable enough to take a pounding from the waves
• be rigid enough to deal with the forces encountered

Given the design considerations I took a few measurements and drew up a quick sketch of the components and how I imagined they would fit together.

If you are going to design your own there are a few important things to keep in mind.

• The bow (nose) of the kayak is generally narrower than the stern (rear). So don’t just make the front and rear crossbeams the same length or it will look funny and not perform as well.
• You could substitute wood 2x4s for PVC in my design, but its not going to last as long and its going to flex and expand as it takes on water. Its also going to be a LOT heavier.
• If you intend to add a motor like I did you must make sure that the distance between the two kayaks in the center is sufficient for the motor to turn 360 degrees without the blades hitting the side of the watercraft.

The Kayak Catamaran Parts List

Everything I used for this experiment came from Lowe’s. I’m sure you could also find it at Home Depot or other home improvement stores.

• 3 – 10′ sections of 2″ PVC pipe
• 4 – 2″ PVC T sections
• 4 – 2″ PVC end caps
• PVC cleaner and cement
• 1 – 18″ x 72″ wood board
• 4 – 2″ stainless steel U bolts with lock nuts and washers
• 4 – 5″ stainless steel eye bolts with lock nuts and washers
• 1 – 8′ 2×4 (or a couple of 8″ scraps)
• 2 – 8″ 5/8×16 bolts with lock nuts and washers
• 4 – Ratcheting straps

I also needed a rubber mallet, wrenches, a drill, a set of drill bits, and a table saw. You could do without the table saw by having the store cut the wood for you.

Building the Kayak Catamaran

The first thing I did was set the two kayaks beside one another and lay the crossbeam PVC pipes on top of it. This allowed me to take measurements and make sure my design was roughly accurate.

It turns out that the exact finished dimensions worked perfectly for my kayaks and particular brand of trolling motor (Minn Kota 30 pound unit). See the design sketch above if you have Equinox 10.4 kayaks and want to exactly duplicate this build.

I then cut all the PVC pipes and dry fit the pieces. I used my table saw to cut the PVC, but you could use a hacksaw and do it by hand, or you could use a reciprocating saw or basically anthing with a blade long enough to go through 2″ of PVC. Its a very soft material so its easy to cut – but keep your cut very straight as you go. The pieces won’t fit properly if the cuts are all crooked.

Then it was time to attach the pieces. First, you must start with the rectangular center frame, and you have to be VERY careful when assembling this piece to make sure you get it extremely straight!

I carefully cleaned and cemented each fitting and lightly attached a T union to one end of the support frame. I then VERY QUICKLY laid it on the flat piece of wood to make sure the T’s were pointing straight. After a little adjusting I took a rubber mallet and pounded the T’s on as far as they would go.

You’ll know when the pieces are fully inserted because there is a little ridge in each connector or end cap that won’t let the pipe go any farther. So you don’t need to worry that you put it in too far. In fact, if you follow my design its extremely important that all PVC is assembled as tightly as possible for proper fit and structural integrity.

If done right you can look inside the T fitting and see there are no gaps and some of the cement is pretty much sealing all the way around the tube where they meet.

First glue up both end pieces, then attach the two long PVC supports to one end, and follow up by attaching the other end piece – which will require you to glue up two pipes at the same time. Work quickly as the PVC cement drys fast! And remember – HAMMER EVERYTHING TOGETHER WITH A RUBBER MALLET!

After that you’re in the home stretch. Time to glue on the cross beam pieces. These are the most critical joints so make sure they are very clean and you have plenty of cement. You don’t want these to break on the water! Also, notice again that in my design the front and rear are different lengths. Here is a photo showing just one side glued up.

Once you’ve finished connecting all the PVC joints and adding end caps, you can lay the frame back down on your kayaks and begin attaching the connecting hardware. First up, the wooden platform needs to be connected on top. This serves two purposes. First, it provides a lot of torsional rigidity. And secondly, it gives you a spot where you can put stuff!

I used 4 long eye bolts pointing upwards to connect the wood to my PVC frame by drilling down through the wood and directly through the center of each of the 4 T-connectors in the corners. By using the eye bolts it gives connection points in each of the 4 corners that can be used for lashing things to the top, or could even be used for lifting / hanging the platform.

You’re going to attach 4 eye bolts pointing downward from the end of each crossbeam. These are going to be used for connecting the ratcheting strap to hold the kayaks in place.

The other end of the strap mounting is a U bolt mounted directly on the platform. Make sure and leave enough room that the ratchet can be entirely on top when its mounted securely. This does a couple of things, but most importantly it allows you to ratchet it up a little while on the water if it loosens up, which it will do a bit when it gets wet. I’ve already proven out this point on the Lake, so don’t skip it.

You’re about done at this point! Now if you intend to mount a motor on it you need to add a wood block that will fit it. I accomplished this by cutting two 2×4″s down to 8″ wide. These were attached with several stainless steel screws and an L bracket (found near the fencing stuff in the lumber department) for some added rigidity. I wanted to make sure there was NO flex with the motor so all of the power translated to forward momentum instead of any wiggle in the mount.

At this point you should be done and ready to simply slip a ratcheting strap under each mounting point, front and rear, on both Kayaks and secure them tightly.

We took the double Kayak Catamaran out on the lake for the day and it performed FAR better than I ever expected! The little 30 pound Minn Kota trolling motor was able to EASILY push the watercraft! By the way, you need to really watch the video I did about the single Kayak motor mount in order to see how to wire it up and which battery to use, etc. But even with the little trolling motor battery I used we were out on the lake messing around with the motor in use for over an hour and only used 20% of the battery life.

Not only was this rig able to easily push and steer the CatamaYak, but we were able to even TOW both of the other Kayaks without any issue! Amazing.

A couple of last little things. You’ll see in all of the photos that the wood panel in the middle is exposed untreated wood. That’s because we bought some special textured extremely waterproof paint to cover it with, but I didn’t do it before the first trip out to the lake. We’ll be painting it for long term durability soon.

Finally, if you do this, you’re technically changing your kayak into a home built motor boat. And in Texas, and probably most states, you’re going to have to register it as a watercraft. It costs like $30 in Texas to do it, but be warned that if the lake police come by you could be ticketed for taking this on the water without registration. So make sure you’re covered so you don’t worry about it.

Oh, and be prepared for a LOT of attention on the water! Because no one has ever seen anything like this before so they’ll all want to be checking it out!

So, that’s it! I hope you guys enjoy the hack / build. Let me know if you have any questions in the comments below and I’ll help as best I can. This is a project that you can build in just a couple of hours if you have the right tools, and the entire cost was around $100 including PVC, wood, bolts, paint, etc. So that’s a pretty good value!