Jim Stewart wrote:
John D. wrote:
On Mon, 1 Mar 2010 17:52:39 -0500, "Ed Huntress"
wrote:

"Bill McKee" wrote in message
m...
"RAM³" wrote in message
. 10...
"Bill McKee" wrote in
m:

Why not aluminum? I have an aluminum boat trailer. Works very
well.
3400# boat. The Covette has an aluminum frame as well as the
Cadillac
bodied Vette. Look at a Corvette and see what they use. Airplanes
have aluminum frames. And as long as you design well, the flex
should
not be a problem.

Boat trailers are rarely twisted the way that off-road vehicles
routinely
are.

The same thing applies to Corvettes.

After all, when was the last time that you went rock-crawling with
your
'Vette? Grin

How about mud-bogging or bouncing around on deeply-rutted roads?

Jeeps are expected to do all of these and more without any ill
effects.
(Getting dirty/muddy is, for a Jeep, a good thing!)
Hell, I raced a vette, steel chassis, and it got to rock clrawing a
couple times. :) And boat trailers are regularly towed over
uneven ground.
With three points taking out the loads -- hitch and suspension
supports, which generally are paired but close -- there is no
significant torsional load on a boat trailer. It's all simple
bending. You can deal with that, but if you towed your boat 100% of
the time, I think you'd develop fatigue problems in aluminum.

The aluminum Corvette chassis are semi-space-frame with some shear
panels. The subframes resolve their loads in three dimensions. There
isn't much flexing there.

The same applies to aircraft, which often are near-monocoque. If
they flex, you die.

Error.. ever see the wings on a B-52? When they taxi out for take-off
both outrigger wheels are on the ground; when they come back one
outrigger will be ten feet in the air. But not only the wings, a B-52
on the ground has large wrinkles on each side of the fuselage, forward
of the wings; flying the fuselage is smooth.

For what it's worth, I was told that the fuselage
skin on a B-52 was unwrinkled until they started
flying them at 100ft off the ground at 500mph or
something...

I can't vouch for the flying condition as I haven't seen a flying B52
that close, but the one parked at Boeing in Wichita around 1981-2
matched the John D description nicely, the wings drooped and the sides
were puckered in the parked configuration. IIRC the angle of the pucker
was mirrored either side of the wing indicating the direction of the
stresses in the panels due to the loadings when on the ground.