[PSUBS-MAILIST] buoyancy

[Cliff Redus via Personal_Submersibles]

Hank I agree with Alec on risk associated with pressurized composit tank.
If you lost air pressure, these tanks are not designed for external
pressure.

Steel is cheap.  Why not fabricate some 1 arm buoyancy tanks with
construction like a conventional  internally stiffened 1 atm pressure
hull.  Use ABS stress spreadsheet to get right shell and stiffener
details.  You could use OTS semielliptical or hemi heads.  The would be
relatively cheap compared to syntactic foam.  With your welding skills,
this would be easy.

Cliff

On Wednesday, November 11, 2015, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> Alec,
> I am in agreement, the trawl floats work out to about 3 dollars per lb
> buoyancy.  My deep diver is a little piggy so it will cost under 3K for
> buoyancy, that is not bad.    Also with the small floats, it will be easy
> to house them.
> Hank
>
>
>
> On Wednesday, November 11, 2015 7:22 AM, Alec Smyth via
> Personal_Submersibles <personal_submersibles at psubs.org
> <javascript:_e(%7B%7D,'cvml','personal_submersibles at psubs.org');>> wrote:
>
>
> Good creative idea, I hadn't thought of pressurizing a tank to increase
> its depth rating. But the downside is more complexity, and I would still
> dislike not knowing what the external pressure rating of the tank would be.
> The complexity probably has very, very low risks, but they do exist. Like a
> risk of the tank inadvertently leaking its air before a dive, or the risk
> of the tank rupturing on the surface for whatever reason (e.g. careless
> impacts, trailer accident, too hot in the sun, etc...) My new boat is a
> pursuit of simplicity, so if it were me I would go with floats just because
> they have no moving parts and known ratings.
>
> Best,
>
> Alec
>
>
>
> On Wed, Nov 11, 2015 at 8:33 AM, hank pronk via Personal_Submersibles <
> personal_submersibles at psubs.org
> <javascript:_e(%7B%7D,'cvml','personal_submersibles at psubs.org');>> wrote:
>
> I was thinking about using CNG (compressed natural gas)  tanks for
> buoyancy.  The type 4 tanks are carbon fibre and rated for 3,600 psi and
> very light.  My idea was to keep the tanks full of compressed air so they
> can withstand the sub depth rating plus a safety margin.   I am liking
> trawl floats may be better now because they are rated high enough and not
> air filled.  The CNG  tanks are much cheaper and conveniently shaped.
> Hmmm not sure now.??
> Any thoughts or concerns anyone????
> Hank
>
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