This is the first tank, with cut lines drawn onto it.

Here is the tank with the long triangular cuts made. I did not cut it while it was standing up on end, nearly all cuts, welding, and squashing was done with the tank on it's side. Tis more stable and easier on me.

You see on the bottom right, the cut was done with a cutting torch, while the remainder was done with a abrasive disk in a body grinder. The glass coating on the inside of the tank made torch cutting rather explosive, so i stopped that.

Here the bottom was cut out, and the top slit in two. Note the hinge left uncut, on both sides, about 4 inches from the top. This is absolutely necessary to maintain alignment / registration between each half as the tank is squashed.

Opps, cut thru a hinge on the second tank, so i tacked on a replacement.

Two views of the first squashing. I call it the "first" only because there is no attempt to fit the perimeter of the cut edges to the pipe insert. The pipe insert is the outline of the bow, bent from 1/2 inch water pipe. The tank metal is welded to that, not to the opposite side of the tank. You can see the pipe inside the tank between the visegrips in this next pic. The visegrips and hinge was added prior to getting to the "second" session.

The "second" session, when the squashed tank metal is pressing out and hitting the threaded rod of the squasher jig. At this time, i also must watch that the tank metal isn't pressed inbetween the pipe outline, but is squashed only to tangent of the round pipe, where it will be finally trimmed and welded. You can see the hinge was removed and the tank metal is clamped to the pipe at a couple places, mostly to stop the pipe from wandering around inside. As it's my reference to trimming the leading edge, it must not move after it is referenced to the opposite end of the tank.

Note the silver colored rod sticking out, it is temporary, just laying there, and holding the pipe inside roughly centered as i grind and pound the tank.

Here i am welding the tank metal to the underlying pipe, trimming the tank metal to size as it's vise-gripped to shape. Obviously, the chain holds the visegrips in place on the variably curved tank. I adjusted the chain length as i went back from the bow point. This proceedure was a huge mental block when i was making the mental movie of how to manufacture the bows, as i have no way to precut this complex curve and then hold it in place with a jig while welding. You see i removed those silver rods and tacked the pipe near the hinges left uncut near the tank top.

All the bow edges are welded. The tank still has foam insulation on it. It's dark, i stop working on it, as sanding this stuff is way too dirty to do inside.

Sanded it, done outside. The welding is cleaned of slag and flux in prep for a 2nd pass of welding, as needed. A couple days ago, it looked like the tank standing up in the background.

The second welding and recleaning done, i brought it inside and applied Bondo to the edges. The bondo makes a finer edge (the pipe edge alone is almost an inch wide!), and covered a lot of welding sins.

The first bow tended to draw inwards along the top and bottom long welded lines on the pipe, and altho not noticeable on the boat, i tend towards perfectionism if there's no drawbacks, and added spreaders in an attempted to make it look better. Turns out, there's not difference in appearance between the finished pontoons. Despite the cutting and rewelding to make it perfect, spreaders weren't worth the effort.

I know the magic-marker line is curved down at the ends, but really, referenced to the centerline of the bow when horizontal, it's a straight line, and matched perfectly to the end of the pontoon.

Here i am using two come-alongs to winch the bows hard over and onto the pontoon tank ends, which i beveled to match the taper of the bows at that mating edge. First bow pic, then second bow pic.

During the weldup. I tacked the bows to the main pontoon section 6 inches around, aligning as needed by applying a board to the pointy end of the bow and whacking it firmly with a sledgehammer.

Once i see it lines up nicely, and repeatedly cleaned, welded, and closely inspected....

... it was treated to bondo-ing to cover and blend the curves, remove the dings and gouges of the chains, ropes, and come alongs, and then a couple coats of paint were applied.

Here's the two bows after welding onto the pontoons, set beside each other, one top one is upside down, the bottom one is right side up. The lines are as perfectly aligned as i could have hoped for. The transition from bow to the straight-sided main pontoon sections is abrupt as seen here, but once the deck is attached and the hold-on strap installed, the transition appears very smooth.

The afore mentioned pipe insert / weld backer / outline. It's common 1/2 inch water pipe, bent to shape, and then cut to just under 4ft in length. The two spreaders were installed for the second bow, and really a waste of time from an appearance point of view, altho they surely added some strength.