PVC catamaran

So I was thinking of building a catamaran out of two pieces of PVC pipe, either 6 inch or 8 inch. I don't know how long it would have to be to support me or maybe others. Does anyone know of a buoyancy calculator I could use to try to figure this out? Or maybe I could use ABS plastic. This is very easy to heat and bend. This way I could actually shape it a little more, instead of having it just be round and less controllable.

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kayakertom2 years ago

I sent money to Marjamada for the dvd for rebelcat5 and he hasn't responded to my order or even ackowledged my payment. Apparantly this site of his is a hoax and should not be taken seriously. I have sent two requests to him for acknowledgement and have received nada, nothing. So far, I am out the money I sent him but there are ways of payback for such criminal behavior as this.

rtaber6 years ago
where would you buy pvc me and my dad plan on making one
http://rebelcat.com/Flotation-Chart.html DO NOT USE ABS PLASTIC! It is soft in the middle betweeen the inner and outer walls.
To calculate the bouyancy, simply find the volume of the PVC pipe. The weight of the water that can fit in that volume will be how bouyant it is
Marjamada10 years ago
I'm pleased to find a discussion of one of my favorite topics - PVC pipe catamarans. I have made three and now have considerable experience with them, up to 20' and 15" diamater (RebelCat.com, Cat 4). My site has plenty of techniques and materials to check out. I wish someone had pioneered this when I was stumbling around. On the other hand, I like sharing what I've learned.
Hi Marjamada.

Nice Catamarans! Your website has a lot of pictures.
I have a project for a PVC Proa (an Oceanic Outriger).
I made a model at 1:5 scale.
You can see pictures at:
The original idea is from Othmar Karschulin, but he didn't build one yet.
I want to know why you change from bolted to tie ratched pontoons?
What you think about what Toxonix says "Also, PVC becomes unstable when heated enough to re-liquefy the monomer matrix. Its plasticity is reduced, making it more likely to crack and fail. "?
In my design I cut the pontoons and use epoxi to make the shape. But I don't know if this is a better solution.
(sorry about my English I'm from Argentina)

Gracias, Andre, I'm glad you like my work. The reason I no longer bolt the frame and deck to the PVC pipes is because this is PIP thinwall, the thinnest pipe available, for lightness. It is difficult to get a good connection by bolting to such thin (weak) pipe walls. Also, I found that straps give a better flexible joint, because the pontoons move independently - fixed joints will break if they don't allow movement. The heated and shaped parts of my RebelCat 4 are extremely strong, but I did not "re-liquefy" the PVC, only softened it enough to shape it. Epoxy is okay for small pipe like you used, but do you know how much epoxy is needed to fill a 15" pipe? Also, epoxy is heavy and expensive. My shaped PVC pontoons are strong and light. Alternatives are traffic cones and megaphones.
I thinking use a thin layer of epoxi over plywood, not to fill all the 15" pipe. But I will try your technique in furder tests. Thanks for your advise and recommendations. I like your RebelCat4 with that wedge shape. Are you not afraid that the pontoons rotate in its own axis?
if your thinking of useing plywood, I would look into "stitch and glue" boat building.
Andre, yes the pontoons do tend to rotate, but very little. This is easily corrected by cementing curved strips of the same pipe material on the pontoons next to the feet to prevent rotation. Believe me, the pontoons move up and down when they encounter waves, and they meet waves at different times. So the joints where the deck/frame meet the pontoons must 'flex'. RebelCat 2 had the frame bolted to the pontoons, and that was a serious mistake. Remember, these cats are made to be taken apart and carried on top of a car or in a pickup, so the joints - where things connect to other things - cannot tolerate the strain like cats made from much stronger and heavier materials. They are made for the ocean, mine are for calmer lakes. Two very different worlds. -Martin rebelcat.com
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