On Thu, 05 Jan 2012 12:55:51 -0700, chaniarts
wrote:

On 1/5/2012 12:54 PM, chaniarts wrote:
On 1/5/2012 9:30 AM, Ed Huntress wrote:
On Thu, 5 Jan 2012 09:23:48 -0700, "Bob La Londe"
wrote:

wrote in message
...
On 1/1/2012 9:34 AM, Bob La Londe wrote:
snip

perhaps switching to explosive forming would be easier/more fun?

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.

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.

sigh 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.

--
Ed Huntress