I didn't want to argue but I was serious about filling it with water and applying air pressure and heat to the damaged area. It has worked for me in the past on aluminum vessels but they were thicker. Water and air are like Hydraulic ram. That how we bring 10' dia pressure vessel up to 3000psi to test for certification.
5150, as usual you are right, the boiling water would be a probelm. The 200 pins, he could tac weld a long piece of alum sq tube across the dent and pulls straight. Forget the heat. Just use air and water and take it to the max slowly. If it blows, he will get wet. There is not enough air in there to hurt anyone but the pontoon. Your in command admiral. ha ha Seriously, do you think that will be safe, you know more about toons than me. We need to figure out how to fix these dents.I certianly don't want to step on your toes lucky but this is an old pontoon tube not a pressure vessel, too much air in a pontoon equals explosion, a presure vessel is designed to hold pressure from the inside out, a pontoon is designed to hold pressure from the outside in, your welds are x-rayed and certified, a pontoons aren't, they are made by a guy named Greg that wants to get home and drink beer.
Also pressure is pressure, it doesn't know where the dent is and will exert the same pressure over the entire inside of the tube and the aluminum will pull out but only where the pin is so you would need to weld 200+ pins on the tube to pull this huge dent out and then it would look like a golf ball with 200 dimples on it.
And last, aluminum aneals just below the melting point which is well above the boiling point of water and to heat the aluminum you would have to heat several hundred gallons of water to a crazy high heat, so poor Sam is standing there with a pontoon tube under pressure with several hundred gallons of boiling water inside, sounds like a recipe to make the evening news.
That's what I was thinking. I've always associated the pointy toons with Riviera. How bout it, samo?
Like I said, the tube is already dead so you can't kill it anymore so anything you do to it can't hurt it.
Of the ideas presented I would go with the big hammer and a 4x4 block and cut access holes in the top of the tube and try to pound out what you can get, Maybe throw some heat on in , especially on the big creases, weld the hole and any leaks shut and see what you have.
I am pretty spoiled, I would just throw it in the pile and have another one built, then again it isn't coming out of my wallet.
Last week I threw away a 28' tube for a scratch 2'' long but on a boat that costs $80,000+ you need close to perfection.
A new good-quality (American-made) 28' pontoon should cost you around $1,800 for what it's worth.Can I buy the 28' is what i need for my 3rd. Wonder what they would sell it for?80k wow. I got a price on 5052 1/8" 6' x 12' $258. Special order, 7' x 12' $297. With this, the can would be 27" dia x 12'. 2 cans= 24' and less than $600. Add a nose section 4 x 8' $200. You have $800 in material. You told me your man was fast. I'll give you 4 hours labor @ $50 an hr. $200. $1000 for each toon $80,0000. Some one is making some money. The Koreans will be making those and shipping over here if they find out. That what they did to the vessel business 10 years ago. Most all are not made here anymore.
Rather than attempting to make the existing pontoon "dentless", it might be worthwhile to think about TIG-welding some sort of shell or facade over the damaged area. Just a thought...
If there's not much of an indentation on the original pontoon then displacement remains about the same and thus, buoyancy. Adding a facade/shell in theory would return it to the original or better displacement (minus the weight of the added aluminum). Assuming that the original pontoon has no holes and assuming that the newly-added subsection under the shell does leak then the worst-case scenario seems to be that you're back to the original displacement minus the weight of the new aluminum (and a pontoon boat that lists to one side a little since the other pontoon still has the additional buoyancy).I was wondering about that also. You'd have to make it water proof so that water did not flow through it and then one side would be a bit heavier than the other. But it is an idea.