Re: [PSUBS-MAILIST] Rebar/Fiberglass Hull- 1 ATM design

[Dan h <machine@epix.net>]

Sorry Ryan, but I agree.
Not that rebar is inferior steel, it's standard A-36 grade, but the round
shape isn't the best use of the material for the strength you need.  I
disagree with square tubing also but for a different reason.  Square tubing
isn't bad for the strength you'll get for the material but it's harder to
form in the shapes you need with out kinking it.  Also with any hollow
material, there is the chance of getting water trapped inside and no way to
inspect for possible internal deterioration from rusting.  You might think
you'll have it welded so water can't enter, but I've seen it many times,  it
usually gets in.

If your going to use a steel outer skin, angle iron or T iron is the best
shapes to use.  They're used with one leg inward or the head of the T
inward.  When welded inside, the hull's skin acts as part of the member for
strength.  If your not using steel, then preferably use an I shape.  If not
that that flat steel bar rolled the hard way.

A word of caution though, a 1 atmosphere sub hull isn't anything to guess
at, as was pointed out to you already.  Only 30 feet of depth is near 15
PSI.  That's over 2000 pounds pushing against every square foot.   Step on a
piece of rebar and see what happens.  Don't guess at hull calculations!

Dan H.

Coalbunny wrote:

> NOT good Ryan.  You see, rebar is not good when it comes to strength.
> It's great for pouring concrete and setting forms, it then provides a
> non-permiable ribbing to keep the concrete from separating when
> cracked.  It's strength is in the linear sense.  Not good for anything
> structural like a sub frame.  Maybe, if it was unmanned.  But I doubt
> you're gonna do that, right?
>
> Square tubing would be best for a secondary frame (would have to sketch
> out what I'm talking about for you to really understand that thought,
> I'm sure).  For bulkheads, I'd say use thick sheet steel.  Of course I
> ain't the engineerin' type.  Just thinking of what I've seen in books
> and such.
> Carl
>
> Rf3500psi@aol.com wrote:
> >
> > I had an idea for a hull that I wanted to run by you guys and get an
> > opinion-good, bad, or indifferent.
> >
> > The hull is frame based.  The frame is made of 5/8" rebar, bent and
> > welded into circular rings, spaced 1' apart along the length of the
> > keel.  For the nose cone, rebar lengths would be bent into oval or
> > parabola shaped sections and then crosed and welded.  The tail would
> > go the same way, shaping sections of rebar and welding.  Then, the
> > frame would be covered in a thin, flexible plywood.  We are also
> > considering a sheet metal layer on top of this.  Finally, the hull
> > would be coated with fiberglass.
> > Penetrations would be sealed with o-rings and a sealant.
> >
> > So,what do you think?
> >
> > Thanks,
> > Ryan
> >
> > P.S. What do you guys think of a spray on bedliner layer somewhere
> > in/on the hull?  Just some half-baked idea my colleague had; figured I
> > should ask.
>
> --
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