Braking Aluminum

Ooooh! Now that sounds fun.

Let me correct something I said about the tooling. In production, a big aluminum-forming die for explosive forming typically would be Kirksite, or ductile iron for a long run, and enough of it to sink a ship. That's what I've seen in operation.

But they do make dies out of concrete and concrete/fiberglass for very short runs. I don't know if they're for standoff forming or contact, but I suspect you need the standoff method to form boats.

That involves an explosive pressure upwards of 40,000 psi. How they contain that with fiberglass or concrete is beyond what I know.

In any case, it's one heck of a lot of concrete and fiberglass.

Has anyone mentioned a wheeling machine (english wheel) yet? They do seem to get mentioned in various boat hull related places.

See

for one, maybe larger than you need.

I have played around in my head with some variations of roller type forming operations. They big problem is 5052 and 5086 work harden. If you need to make multiple progressive passes to get the shape you want (such as a hard chine) you would need to setup back to back rollers each with a progressive angle from the last close enough so that the flex of the metal never stops from one end of the process to the other. Setting up a single set of rollers might be pretty doable, and even economical if they can be repurposed from something you already have, but building an array of them and setting them up to do a job like this could be cumulatively as expensive as a large brake if you can find one at salvage. For something like a round chine they can do multiple passes because only the area being immediately worked hardens. The next pass will be next to rather than on the previous pass.

Its an interesting problem.

there's also hydro-forming, but you may face similar $ related problems.

and it's not as much fun.

and there's the mixture of both types:

Explosive hydroforming

For large parts, explosive hydroforming can generate the forming pressure by simply exploding a charge above the part (complete with evacuated mold) which is immersed in a pool of water. The tooling can be much cheaper than what would be required for any press-type process. The hydroforming-into-a-mold process also works using only a shock wave in air as the pressuring medium. Particularly when the explosives are close to the workpiece, inertia effects make the result more complicated than forming by hydrostatic pressure alone.

There are so many ways to skin cats. Hydroforming used to be a very tooling-intensive process, but the last I looked was ten years ago. And that was GM, hydroforming truck chassis.

Anyway, I'm going to watch and see what the others come up with. I still don't know how you'd do a one-off small boat in aluminum without frames and/or stringers, and lots of welding or riveting.

I thought I recalled seeing making of the likes of chines in the centre of a bonnet (US hood) with a wheeling machine in the book by Ron Fournier but couldn't find it. I recall it involved tipping the lower wheel over on one side by spacing it up on one side so the side edge radius did the work but can't currently find the detail.

Other than that I might try a progressive approach with a former like a boat prow and work your way from one side to the other then start at the beginning again repeatedly until you have the chine shape. The former possibly having the full shape but not used all at once to prevent to much localised deformation of the work. The former could be pushed into rubber, polyurethane, air maybe. I did something vaguely similar recently to form some 300mm dishes with about a 250mm radius for a lighting job in 5mm aluminium. I used a radiused former to push the aluminium into the end of a pipe, I had some 5mm UHMWPE sheet between the pipe end and the al to prevent marking. I was using a fly press so was able to strike rapidly with measured blows and each item took about

5 minutes to form once I had done a practice piece. Forming just required repeatedly working around the circular blank until it had an even radius. I suspect a chine would be more work but could be tested on a small scale to see if the technique was viable.

I formed this bucket from 0.050" stainless by hand, by clamping the bend line to the edge of a steel welding table and hammering the flaps over with a large hammer and wooden block:

back is a shallow 4-sided tray, the bottom a square-ended U, stick welded with 312 rod.

As you wrote the bend has to be done progressively, maybe ten degrees at a time, to avoid stretching and warping the metal.

Though I don't have any photos to prove it 0.062" 6061 is bendable in large sheets the same way. 5052 is easier.

jsw