Steel pontoon boat ideas?

[GTS225]

FNG here. I didn't see an area for intro's, so maybe one isn't needed.

Have a mental building plan for a small pontoon boat, and figure multiple brains are better than my shoulder-mounted vacuum chamber.
I'm also a scrounger, so if I can do this low-budget with recycled materials, so much the better.

I have the idea that I can recycle water heater tanks, and weld them together end-to-end, to form a compartmentalized pontoon. Sure, the steel will make them a bit fat, weight-wise, but I'm thinking the trade-off in cost savings and safety is worth it.

I have already collected two, 50-gallon electric heater tanks, stripped them, and managed to get the hard water deposits cleaned out. This gives me a tank that is 16" diameter, and 53" tall. The bottom is concave, while the top is convex with pipe fittings welded in. At this time, I don't know the thickness or weight.
My plan is to plug the fittings, and with minor rework, the tops and bottoms will nest together for a good weld seam. This will allow me to weld up a pontoon any length of my choosing, with the added benefit of compartmentalization.

From there, it seems a relatively simple task of adding a deck, transom, railing, and small pilot station, giving me a great little weekend outing vessel for lakes or lazy rivers.

Any thoughts or suggestions? Shoot down the idea on safety issues?

Thanks.....Roger

[gonzo]

You should start by weighing the tank. If it is very heavy, the reserve floatation will be very little. Also, there are plenty of cheap or even free old pontoons.

[GTS225]

Damn!.....This thing weighs 65#! (I was expecting something closer to 40.)
Using the formula posted by Alan White in another thread,
(Calculate the volume of the pontoon in cubic feet and multiply by 31 lbs. That puts the pontoon halfway submerged.)
I come up with 188# of floatation, but subtracting the tank weight, I have only 123# available.
I'm quickly coming to the conclusion that my idea will be impractical. I can build the pontoons, but I get a single, 13.25' 'toon weighing 195#, and have only 369# of available support.
I suppose I could go with three 'toons, but then the finished boat gets really fat. I really don't want to worry about max load going over bridges.
I'm thinking I need to keep an eye out for a couple aluminum pontoons.

Thanks for the reply, Gonzo.

Roger