"Tim Wescott" wrote in message
...
On Fri, 30 Dec 2011 12:22:53 -0700, Bob La Londe wrote:

I have a copy of Pollards aluminum boat building book, and I have read
it. It looks like he mostly plans on boats to be all cut pieces and
welded. That's great for big boats or even for some small boats, but
braking seems like it would make more sense if you have access to a
brake big enough. Some of the small boat designs (think shallow draft
skinny water boats) would really benefit from a mostly bent hull.
Aluminum sheet can be had in pieces large enough to make most of a hull
out of one sheet. Some cutting and welding is still needed obviously,
but if you could brake the keel, chines, and bottom of the transom only
welding the front and the sides in the back you would have an inherently
stronger and more rigid boat for rough service.

The problem of course is how do you brake a piece of metal that big?

Yeah I know a giant hydraulic brake would be a good answer for the
commercial boat builder once they have the capital for it, but how does
the backyard boat builder do it? Are they stuck with all cut and welded
pieces, or hauling their sheet to somebody with a giant brake to do it
for them (if there even is somebody with a brake big enough in the area
that hires out)?

If you could limit yourself to mostly long skinny pieces, and
particularly if you never "asked" for more than a 90 degree bend or so,
then you could make a brake out of a couple of sections of (big) angle
iron and a bunch of C-clamp-ish thingies.

Make your brake by holding the lower angle open side up, with clamps
distributed along the length to push the upper angle down into it. Put
in your long skinny piece of metal, then run back and forth tightening
clamps (evenly) until you get the bend you want.

It's slow, goofy-looking, and imprecise -- but it's also cheap, easily
made, and should be effective.

If you want to achieve an actual 90 degree bend you'd need to use U-
channel for the lower part, and either augment the upper angle with a rib
along the point (to get a tighter-than-right-angle bend), or just
fabricate your upper angle to have a 60 degree bend or whatever.

I have actually considered some things like that, only I would need C clamps
with a 30 to 40 inch throat. I also considered trying to setup something I
could just drive over with a truck. LOL.