Build a "Dogamaran": a Catamaran-style Float for Small Dogs

In the warmer summer months in the midwest, one of my favorite ways to get out of the house with my dog is to take him fly fishing with me. I often fish the banks of local small streams and keep him tethered to a waist belt, but when it get's hotter, I prefer to be in the water (usually wet-wading to stay cool). As a smaller dog (he's a Jack Russell Terrier), he's too little to wade with me, so I built a little catamaran-style boat that is fastened to me on a drag-line attached to my belt so he can tag along with me and enjoy some quality time on the water. It's easy for him to get on and off the raft as long as the water isn't deep, so he gets ample opportunity to check for fish and cool off in the river.

The video above shows the first version of the dogamaran that I built, which is being used by my daughter's dog, Lottie, while my dog, Charlie, rides along in my packraft. I prefer the dogamaran because it's smaller, lighter, and easier to inflate and carry from the car to the river, so I decided to build a second dogamaran to use when my daughter joins me on our outings. I thought I'd document the process of building one in case folks here have an interest in building something like this.

It's relatively inexpensive (about $90 US) and super easy to make if you re-purpose the fabric from a dog bed. I've been using one for the past two summers, so it's proven to be very durable as well. Note that my dog is about 15" tall at the shoulders and weighs about 18 pounds, and I'd say that's near the upper limit for this craft.

My dogamaran is built on a pair of SUP stabilizer floats from Amazon, which currently cost about $40 US. The first ones I used were even less, and were slightly bigger than the ones shown in this project. For the "trampoline", I used the fabric from a $25 dog bed for my first version, but for the one shown here I made my own trampoline from fabric that I had left over from my ultra-portable dog cot (also described here on Instructables). I'm not going to cover making the trampoline from scratch in this Instructable since it's probably almost as cheap to use a dog bed and is certainly a lot easier. The frame is built from a 10' length of 1/2" PVC pipe and a handfull of T and elbow fittings. I also used some 15mm wide straps with clips to hold the frame ends/pontoon holders in place, but you could also just secure them with screws or with paracord, or you could just re-purpose the straps and clips that you'll remove from the SUP stabilizers. I didn't do that route because I wanted my straps to be smaller and I had the materials on hand.

Here's a list of what you need to build one of these:

1. SUP stabilizer floats - you’ll want the ones with a longer and flatter profile, like those pictured. Avoid the ones that are curved along the entire length as these will not provide enough stability.
2. Dog bed with a removable fabric cot (I used an 18" by 24" bed)
3. 10' length of 1/2" PVC pipe
4. Eight 1/2" PVC elbows
5. Eight 1/2" PVC T-connectors
6. About 3 feet of 15mm polyester strap with 4 clips (or you can use paracord and fashion sliding knots)
7. Four feet of paracord (for the pulling harness)
8. PVC cement (to glue the pontoon attachment frames together)

For tools, here's what you need:

1. Saw to cut PVC to length (a japanese pullsaw works great, but a bandsaw makes easy work of modifying the four T-connectors that form part of the pontoon connector assemblies)
2. Seam ripper to remove the SUP stabilizer straps
3. Scissors to cut the paracord and the strap material
4. Lighter or small kitchen torch to seal the ends of the paracord and strap material and to prevent fraying
5. Tape measure
6. Permanent marker to mark the PVC for cutting

The easiest way determine the frame size you need is to measure the dimensions of the frame that came with your dog bed and cut the PVC pieces to make the same sized frame. If you don't have the frame, you can proceed as follow:

1. Lay the bed on the floor bottom-side-up and fasten the Velcro flap.
2. Measure the bed from the edge of the Velcro-closed end to the opposite edge and cut two pieces of PVC to this length minus 1-1/4 inches. This will give you two side tubes that are slightly longer than you need, but you will trim them for a snug fit later.
3. Insert the two pieces of PVC that you just cut into opening that run perpendicular to the Velcro flap and attach a T-connector to the same end of each length.
4. Push the two pieces of PVC apart to put maximum tension on the bed and measure the distance between the T-connectors as shown in the first two photos above.
5. Cut two more pieces of PVC to this length plus 1/4” to ensure a nice, tight fit.
6. Open the Velcro flap and assemble the frame into the bed as shown.
7. Close the Velcro flap around the pipe and pull it as tight as you can and check the alignment of the two pieces of Velcro. Your goal is to have them mate perfectly with the bed stretched tight, so you’ll need to measure the difference in their alignment (as shown in the photo) and trim the two side lengths of PVC by this amount.

Once you have the frame fit properly to the bed, you’re almost ready to start working on the means for attaching the trampoline frame to the floats, but first you have to prepare the SUP stabilizers so they can be used as pontoons.

I designed my dogamaran to use the PVC fabric loops on the SUP stabilizers to attach the pontoons to the frame, but for this to work, you have to remove the straps that are sewn to the PVC loops that are bonded to the front and rear of the floats. I used a seam ripper to remove all of the stitching without damaging the PVC loops. Work carefully with the seam ripper to remove the stitches from the PVC fabric side (it’s easier). I found it easiest to get the point of the seam ripper under the thread in approximately the middle of each run of stitches, and then work back to the corner pulling the thread out from under each stitch loop. Once you’ve pulled all of the backing thread, you should be able to separate the polyester strap from the PVC, leaving with just the PVC loops as shown in the last photo above.

The bed frame attaches to the pontoons with 4 smaller frames that are fit to pull the PVC loops together and hold the pontoons in place under the main frame. I sized these so that the trampoline frame sits back of center, so that the dog's weight stays back. This helps the dogamaran ride better, especially since I'm fishing and the dog riding on the raft wants to be as close to the action as possible. For this version, the distance between the PVC loops is small enough that I could connect the inner part of the pontoon attachment frames to the main frame with a T-connector that I modified to slide over the main frame. In my first version, the loops were much farther apart, so I had to use a different approach that's shown in the photo with the orange pontoons. For this version, I also realize that I could have simply shortened the frame tubes and used a full T-connector with a very short length of pipe after it, so you could also take that approach. In any case, here's how I made the pontoon attachment frames.

Start my mofidying four T-connectors to hold the inside pipes of the attachment frames so they can slip over the trampoline frame.

1. Cut off one end of the T-connector as shown.
2. Use a Dremel with a coarse sanding drum to remove the raised part inside the inner section of the T-connector so it will slide over the frame pipe. I've tried to show the raised section and then what it looks like after removal in the photos above.
3. Disassemble the frame and slide the modified T-connectors onto the frame as shown and re-assemble the frame.

Now measure the width of the PVC loops and make the rear pontoon attachment frame so that it is just long enough to let the strap sit on the PVC pipe between the connectors. Keep in mind that the PVC pipe goes about 5/8” into the connectors, so the pipe should be cut 1-1/4” longer than the width of the PVC loop material.

Once the rear attachment frames are made, insert them through the rear PVC loops on each pontoon so you can measure the size of the front pontoon attachment frames. After you’ve got your measurements and made the front attachment frames, assemble everything to confirm the fit. when everything looks good, I cemented just the outboard part of the pontoon attachment frames so that I can attach each frame to the main frame as a unit, but can also easily remove the frame to separate the f race assembly from the pontoons and can also completely disassemble the entire dogamaran.

I made the tow harness from paracord, as follows.

1. Tie a bowline around the trampoline frame as shown.
2. Wrap the cord twice around the front of the pontoon attachment frame as shown.
3. Wrap the cord around the other pontoon attachment frame and fasten to the trampoline frame with another bowline.
4. Make an Alpinist Butteryfly knot in the center of the tow harness line as shown. Check YouTube for videos on how to tie this knot. I centered my knot by moving my hand to the center between the two pontoons after making the three wraps around my hand.

Since the pontoon attachment frames are not cemented to the trampoline frame, you need another way to secure the pontoon frames to the trampoline frame. In the first version I made I just used paracord, tying a bowline around the trampoline frame and then tying a locking slip knot around the front of each attachment frame. However since I had some 15mm straps material and clips, I decided that on this one I would use the straps and clips to give it a more polished look. To make the strap for each frame, I fastened one part of the clip to the end of the strap using the D-ring to hold it in place, and then measured enough strap to wrap around the attachment frame and trampoline frame plus a couple inches of slack. Make sure you melt the ends of the strap after cuttin to prevent fraying. After threading the other end of the strap through the mating clip with the cinching slot, thread the strap around the attachment frame and trampoline frame, clip it together, and then tighten the strap by pulling on the end of the strap where it comes out of the cinching slot. This will suffice to hold the attachment frame to the trampline frame, but will also allow you to easily remove the frames for disassembly.

Since both mine and my daughter's dogs are excited enough about fishing that they will try to stand on the front of the pontoons, for this version of the dogamaran I decided to try and deter that by adding wedge-shaped "shields" to cover the pontoon. These are just rectangles of corrugated plastic that are cut down the middle on one side so they can fold. I then designed and 3D-printed 4 clips that are attached to the shields with stainless steel panhead screws that are set into a reinforcing "backer" on the other side. You can make your own shields to fit the dimensions of your setup, but I've included photos of the dimensions of my shields to provide a starting point. I've included the 3D model files that you can use to print your own parts.