[PSUBS-MAILIST] Stability & Buoyancy

Sat Nov 30 18:48:54 EST 2013

ROVs 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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