Re: concrete weight

[shawl@torchlake.com (Jonathan Shawl)]

Hi all,
I was thinking about the weight problem also. If you have a concrete hull 4 or
5 inches thick as was suggested earlier, I think you would use up most of the
reserve buoyancy and you could not put as much lead weight on the bottom to
make it stable in the water. And to make things worse the conning tower section
may have a negative buoyancy. It may roll too much, and be too unstable to
climb in and out of. I haven't run any figures yet but I have a feeling it may
turn out that way. Does anyone have a concrete hull example with the buoyancy
calculations done yet? I for one would be interested to see how it turns out.
Will there be enough reserve buoyancy left over to support the payload of
people, batteries, tanks, motors, arms, equipment, etc.? Maybe concrete is
better for only larger hulls like navy subs? What was that hull thickness to
dia. ratio again? I would like to do some of my own calculations to see how it
will turn out.
Just trying to encourage some thought also.

Jon Shawl

PS. Now if I can add something, toung in cheek...
It's been a quiet e-mail weekend so far. A concrete sub may very well be the
fastest way to get to the bottom... I wonder if everybody is at the lake with
there new concrete subs they built this week. :-o
Humm... . ;-)

protek@shreve.net wrote:

> Jon,
>     By now everyone knows what I think of the concrete idea, but here is a
> thought.  My sub has a 36 inch outer diameter and a wall thickness to the
> steel of 0.360 inch (almost 3/8 inch).  I did not until tonight know what
> concrete weighed, but you stated that it weighs approximately 150
> pounds/cubic foot.  Steel weighs approximately 490 pounds/cubic foot.  This
> means that steel weighs 3.27 times as much as concrete.  Now, if I had
> built my sub out of concrete, then the hull would be 3.27 times 0.360
> inches or 1.17 inches thick.  Imagine a hull 3 feet in diameter and 1.18
> inches thick made from concrete.  One might say "Make the hull thicker",
> but weight come into play here.  Would anyone be satisfied with a 1.2 inch
> thick concrete hull?
>
> Just trying to encourage some thought here...
>
> Gary Boucher