[VAC] Re: Structural loading / aircraft flooring

[Sarah Calhoun <srcalhoun@xxxxxxxxxxxxx>]

> Strength is
> proportional to the fourth power of the spacing.

Ah so that's why a 5" beam is so much stronger than a 3".

> The channel is pretty
> well spaced by the web.

What web is this, you mean the cross-members in the frame?

> There is a strong
> tendency for the top and bottom to try to slip with respect to each
> other under a bending load. The filler has to handle that shear load. As
> flanges are strengthened that shear load on the filler gets greater.

This all makes some kind of sense but wouldn't the main purpose of the filler be
to spread the load and keep the steel from getting to the collapsing point in
the first place?  Once it's at that point I can't imagine a foam or honeycomb
material that's going to stop it.  I mean, noncompressible is all very well but
the stuff is still going to be friable.  And nothing fries you like an angry
piece of moving steel!

> Aluminum can be
> light, but with two skins and spacers, the full skin probably weighs
> more.

I was forgetting about the inner skin, just thinking of those photos of 2 guys
holding up a full shell between them, looks like on 2 fingers but probably
isn't.  Hey!  How about filling the space between the skins with HELIUM?  They
put argon gas in double-pane window assemblies for insulation; could helium
serve a similar purpose?  Or is it too small and leaks out?  Yeah, I suppose if
they could make skins that would never loosen around the rivets or leak, that
would be something in itself.

> If you doubled the load carrying capacity of the frame by fitting more
> frame elements side by side to the original, and of the same size, and
> reduced the floor weight by going to honeycomb, you'd maybe come out
> even because the doubled frame would probably weigh as much as the
> improvement in floor. Then you still have to contend with axle, bearing, and
> tire load carrying capacity.

I thought the idea was to fill in the spaces between existing members with some
lightweight, solid material, instead of adding more frame members?  And then
also lighten the floor and maybe also make it stronger (?) with the aircraft
flooring (is that stuff lighter AND stronger, or just lighter?).  So then you
have saved some amount of net weight AND your floor is stronger by "some"
because of the filler and maybe some more because of the flooring.  Probably not
enough to add a waterbed but even a couple hundred pounds could be significant,
if you are already pushing the tolerance.  At the very least it's a better
safety margin for the same amount of "stuff."

> Water is very heavy and some water beds have been known to crunch houses.
> Maybe there's the equivalent of an air mattress in a THIN waterbed.

Collapsing houses, I thought that was just a myth landlords made up to keep from
renting to hippies.  At one point I remember figuring out that a waterbed
doesn't load the floor any more than a full refrigerator, per square foot.  And
if a building is up to code it is supposed to be able to support a
refrigerator.  If it's not, that's another story.  But, code for buildings
doesn't appy to airstream floors anyway.

Well hopefully this all isn't just totally a flight of fancy; for someone
already doing a frame-up restoration who could locate some honeycomb or foam
filler, it's not too much of a stretch to think about using these ideas to beef
up the frame anyway, right?  Especially for adding holding tanks and a battery
of batteries to a unit that never had them, for example?  As long as you placed
them correctly and were careful about traveling with the tanks full, seems like
it all only makes sense at least to consider it.

Or, another option:  boondock only near bodies of potable water, crap in the
woods like all the other creatures, have all our little solar this and that, and
forget all this bells & whistles stuff!  I mean, a little aluminum box to sleep
in, some folding chairs, fire and maybe a little firewater, we're already way
ahead on the deal, right??  all this, PLUS thumbs and the wheel?  Hey, then all
we need is to grow fur on our bodies and we're home free!

--Sarah