"Bruce" wrote in message
...
On Sun, 1 Jan 2012 08:07:17 -0800 (PST), Bob La Londe
wrote:

On Dec 30 2011, 6:15 pm, Bruce wrote:
On Fri, 30 Dec 2011 12:22:14 -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)?

Bob, you probably know this but sheet aluminum has a "grain" and
bending with the grain is different then bending across the grain.
Also aluminum bends are not sharp 90 degree bends but have a small
radius and require a "bend allowance" for this radius. Depending on
hardness of the aluminum you can make sharper bends across the grain
then parallel with the grain (without cracking, that is :-)

I would assume that you would have at least a bench brake, with say 36
inch capacity, if you were going to start building an aluminum boat,
and depending of course on the design I would look around for a sheet
metal business that might have a brake large enough to make any long
bends as it will certainly make of a nicer looking finished project.

I'm not really a tin-bender but I believe that there are brakes that
will allow bending only part of a piece so that you can bends say 24
inches then slide the work and another 24, etc. Try google "box and
pan brake".

You an bend aluminum sheet by clamping it to a male "mold" that has
the correct angle and a radius for the allowance and then bending or
hammering. Or you could build a "press brake" die which is a vee
shaped female die and a matching vee shaped male die - with built in
clearance - these will bend up to 90 degrees, or less, depending on
how deep the male penetrates the female die.

Lastly, (again as you may know) soft aluminum distorts extremely
easily and it is easy to fall into the trap of bending something a bit
wrong and thinking "Oh, I'll just straighten it out", only to discover
that the aluminum just grew a little longer where you bent it.

I suspect that bending up a pirogue might be fairly easy but one you
your 900 HP Bass Boats will be a bit difficult.

Oh. Yes, try to find a copy of "How to building a tin canoe" if you
possibly can. It is a great boating book and does have instructions
for building a boat out of galvanized iron :-)
--
Cheers,

Bruce

Bruce,

Thanks. I will see if I can find a copy of that book. No this
application is not for a 900HP bass boat. LOL. Think 16-20 HP mud
motor. Purpose built shallow water brush country beaver dam jumping
mud boat. As light as possible and still make it home... mostly in
one piece.

P.S. The motor on my big bass boat only puts out somewhere between
250 and 270 at the prop shaft. (Depends on the temperature and
humidity.)

Bob

Bob, Obviously I was being a bit facetious with the 900 H.P. but after
all I'm a guy that's sitting in my 8 ft. punt with the 2 H.P motor
watching the bass boys roar by :-)


Oh! Well in that case I can brag about how fast my bass boat is... unless
one of those Bullet or Allison guys is within earshot. LOL.

Seriously. If conditions are ideal I can hit mid to high 70s (MPH), and I
can run 70+ under most conditions. I usually run in the mid 60s and my
motor sounds like its loafing. Same motor on a 20' Bullet will run high
80s, and on a 20' Allison they can hit 90. Faster on one of the old Allys,
but its to heavy for them.

Right now I want something that will do 15-20 with just me and my gear in
shallow stump infested beaver dam addled feeder streams. I can run them in
my canoe, but I have to get out and drag my canoe over the beaver dams. My
feet actually got wet out duck hunting yesterday. I couldn't take the cold
after 6 or 7 hours. Brrrrrrr.... It only warmed up to the low 70s (F)
yesterday. LOL. Actually it was a pretty nice day on the water wet feet
and all. Sadly I only plugged three of them pesky little entrees, and I
lost one in the brush. You should have seen me wading through the cat tails
chasing one little green wing teal that just wouldn't die.

Bob