[PSUBS-MAILIST] Stability & Buoyancy

[brian]

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-----Original Message-----
From: "Pete Niedermayr" <freepetesub at yahoo.com>
Sent 11/30/2013 3:48:54 PM
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Stability & BuoyancyROVs are like phone sex- that should be on a tee shirt
--------------------------------------------
On Sat, 11/30/13, vbra676539 at aol.com <vbra676539 at aol.com> wrote:
Subject: Re: [PSUBS-MAILIST] Stability & Buoyancy
To: personal_submersibles at psubs.org
Date: Saturday, November 30, 2013, 1:16 PM
Jon and
all,
The A-boat sail was pirated directly from the
Pisces mold and serves as a splash guard for emergency
egress on the surface. The initial MBT design was for a
wraparound set of tanks, which were expanded to the broad
topped triple tank setup that is still on board today. Maybe
that was an ABS requirement for larger tanks. I don't
know. You can't see it, but the primary tanks are
U-shaped on the bottom and mostly flat on top. They straddle
the hull with a central vent each and stainless steel straps
running from one side to the other and out the bottom
openings to bolt to the pressure hull.
Perry designed their conning tower as a primary
observation point for the pilot and built accordingly. With
Aquarius, it was definitely secondary (used mostly around
structure and while surfacing or on the surface, and often
with creative invective as the ports are so damned small).
Remember the old cameras? A compact one was the size of an
Aladdin thermos, and the pan and tilt units were big and
clunky and expensive. These days, small cameras can do a lot
of that from-the-top kind of viewing.
The A-boat sail itself is screwed down to the deck
and is completely free flooding, essentially open all the
way around to the space under and between the MBTs under the
outer skin. The open portion in back of the conning tower
provides a route for the aft lift strap, which is why you
usually see the lift rig sort of draped out of the sail and
onto the deck forward. If you look carefully, you can see
the pressure hull and a ring stiffener back
there.
A
side note is that the same sail drained through rubber
scuppers on a Pisces. The idea was that you after you were
on the surface, it would drain down enough to allow the crow
to open the hatch in an emergency. A lap full of water was
probably eminent if you had to do it, but you also probably
wouldn't lose the sub.
I
ran Leo for a season (Pisces with a big window) but never
had the need to see if the scuppers were effective.
That's a good thing. Eventually, we replaced the main
hatch with a regular conning tower built by Hyco and did
away with the sail entirely, which was an infinite
improvement for the close observation work in bad conditions
we often did in the Gulf of Mexico where we were
operating.
These days, they have cameras and light systems
that can see more than what the US Navy calls the Mark I
Human Eyeball, but back then, I was all there was, and no
matter what kind of equipment we had, I always wanted to SEE
stuff for myself. Still do, come to that. If I wasn't so
stubborn about it, I'd probably be running ROVs, which
isn't any fun at all in comparison. Like our Dr. Phil
says, ROVs are like phone sex. Okay in a pinch, but nothing
like the real thing.
Vance
-----Original
Message-----
From: Jon Wallace <jonw at psubs.org>
To: Personal Submersibles General Discussion
<personal_submersibles at psubs.org>
Sent: Sat, Nov 30, 2013 11:18 am
Subject: Re: [PSUBS-MAILIST] Stability & Buoyancy
Excellent point and great photo to illustrate
it.  I notice that
the sail on Nutyco's Aquarius is completely vacant
aft of the
hatch to quickly release trapped water and of course
doubles to
provide easy access for entry.  Also the
deck/ballast is high (at
the hatch thru-hull) and very wide providing excellent
stability.
On 11/30/2013 5:51 AM, MerlinSub at t-online.de
wrote:
Hi Alan,
additional the sub can dynamic unstable during
surfacing.
 
There is a lot of water in the free flooding open
sail.
If you surface fast and with to small opening in the
bottom of the free flooding sail the extra weight
can 
move the CG so high that the sub tends to
get heavy
side angles during surfacing until the water rush
out. 
The picture 8382a shows the higher waterlevel during
surfacing
in the sail and the MBT sadlle tanks still
under water
but for this sub the extra weight was not critical.
But on a military one with there tons of
water in the sail during a fast emergency surfacing
it can be a problem.
By the way Euronaut has no Kingston valve without
any problem
and a positve GB alltimes greater than 2".
On dive station or surfaced.
And great openings in the bottom of the sail.
Boats without Kingston valve tends to lost some
bouancy during rough sea. The tanks and the
seastage
work like a air pump and some water enter the
tanks.
On the otherside a boat with Kingston and a
compressed air blow out system can blow away the
tanks very fast if you forget to open the Kingstons
during blowing the tanks or have a air leak
in the in the pipe to the tanks.
vbr Carsten 
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