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


"Bill McKee" wrote in message
news:qZ6dnaBKsPYVoxHWnZ2dnUVZ_uudnZ2d@earthlink. com...

"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.


John D.
(johnbslocombatgmaildotcom)

I don't know what the structure of a B-52 looks like, John, but it must be
far removed from a true monocoque. If a monocoque's skin wrinkled in
compression, all integrity would be gone, and it would completely collapse.

The wings contain spars -- the skin is stressed in tension but takes no
compressive loads. That's stressed-skin but not monocoque. Most metal
aircraft wings are made like that.

I was referring to the fuselage, of which there are many different designs.
As far back as the British Mosquito bomber of WWII, some aircraft have had
near-monocoque designs, which depend on the skin (which sometimes is cored
sandwiches, as on the Mosquito, and not a single sheet) to handle tensile,
compression, and shear loads. As you approach a true monocoque, any
stringers and ribs are there to help keep the skin's shape, rather than to
directly take out the major loads.

--
Ed Huntress