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RE: [PSUBS-MAILIST] Loss of Buoyancy Accident (was Submarine motors)



Ken,

Depending on the hull design, a submersible may actual lose some buoyancy when bottomed out.  In addition, there may be bottom suction that must be broken through to start ascent.  Due to the bulk of the hull, you will probably find it difficult to control two bags and if there is loss of buoyancy when bottomed or bottom suction present, the stranded submersible (DISSUB) will make a VERY rapid ascent that could cause deco issues for you.

 

When conducting a professional salvage, the lift bag should be sized to the load to be lifted so that it is near 100% filled with air when lifting starts…thus buoyancy will be automatically controlled on ascent as the expanding lift gas will be vented off instead of increasing lift.  Loss of buoyancy due to bottoming or bottom suction should be negated with a much smaller bag in addition to the main bag; this can be quickly dumped once ascent is started.  Additionally bottom suction can be broken by jetting air under the submersible.  The most maddening thing is to have 1 ½ tons of lift rigged to a goody on the bottom in 120 fsw, having it buoyant enough to bounce on the bottom and relatively easy to move, and then find that you need one more small bag, a bit more lift gas, and more bottom time.  With an impending gale rolling in, it really hurts to have to cut the lift away, return to the surface empty handed, and have to chase your lift bags downwind.

 

You also have to take into consideration at what depth the DISSUB is at when starting the lift, the deeper the stranding the more gas you are going to need for lift.  A much simpler solution that involves a lot less logistics and is often much more timely is to just attach a heavy line to the DISSUB and haul it to the surface.  Two men on the surface can easily pull up a 200 pound load to the surface.  Once in shallow water, it should be easy for a diver to knock loose the emergency ascent weight to gain sufficient buoyancy to put the conning tower out of the water for crew egress.  We have raised a 28 ft. Novi lobster boat in 130 fsw in New England with little more than a good anchor winch.  Once at the surface, we slung it between two boats and pumped it out…it was back lobstering in 3 days.  That water is cold in December!

 

This issue and many others are being reviewed for the paper Contingency Planning that I will be giving this summer at the Holland gathering.

R/Jay

 

PS:  A properly rigged 55-gal. poly drum has about 465 lbs of buoyancy in salt water if I remember correctly.

 

 

Respectfully,

Jay K. Jeffries

Andros Is., Bahamas

 

A skimmer afloat is but a submarine, so poorly built it will not plunge.

 

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Ken F
Sent: Tuesday, May 08, 2007 3:15 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Submarine motors

 

Yes, MBT's are flooded, as well as VBT(s), and the weight is not droppable (i was goin for worst case scenario).  I dont know if it applies, but if it ever did, it'd sure be a crappy situation.  
150lbs?   So If I controll the ascent using two  250lbs Commercial lift bags with dump valves, and on each side on the underside have strapped a 250lb lift pillow bag...  hmm, I suppose i'd really have to try it in order to see if it'd work or not...   I figured on using the commercial lift pieces on whatever hooks are used with a crane, and just under the surface, pillow bags would be attatched to the sides, and the commercial bags could be used as well if necessary.  One of the other methods of dual-side flotation when the surface has been aquired is modified 55 gal poly drums.  But that really takes away from the "portable" issue.

Ken

 

I figured on overkill in case the sub had been partially flooded....   in either case an extremely controlled descent would be required incase the occupant lost 1ATA.

"Smyth, Alec" <Alec.Smyth@compuware.com> wrote:

Ken,

 

When you say "deballasted" do you mean a situation where the MBTs are flooded and for whatever reason you cannot blow them? The buoyancy of the sub in that condition is normally zero. So any little bit of buoyancy will raise you, but what you'd really need is enough buoyancy to lift the coning tower clear of the water to open the hatch. In the case of a K-250, on account of the acrylic dome you will need more than in a sub with a flatter hatch. I'd have to work out some basic numbers, but off the top of my head I'd say about 150 lbs should do it for the K-250.

 

rgds,


Alec

 


From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Ken F
Sent: Tuesday, May 08, 2007 10:45 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Submarine motors

I'm actually in Chicago, but in 3 months I'll be moving back to Southern Cali.  (somewhere between Lancaster/Palmdale and Bakersfield).  I have alot of design concepts for almost every stage of my sub's production kickin around in my head, in various forms of dissaray, and some things out on the computer, but currently im spending every spare minute trying to learn how to use SolidWorks 2004 so that I can put something together that's more finite and...um...solid?  Lol.

 

The submarine escape simulator sounds really interesting.. 

I'd like feedback from everyone on a project I'm working on.  Its a highly portable, compartmentalized, flexible, custom, adjustable (more adjectives!!!!) system for diver assisted submarine recovery in a condition of full ballasting loss, and takes into consideration the possibility of not being able to release the manual drop weight.  

I'm a certified and well practiced deep diver and have been (breifly) down to 220 feet on normal air.   So i'm comfortable with depths that some people might not be comfy trying to escape unnasisted from.   Anyhow, I've contacted a couple salvage companies, and even gotten OEM pricelists in order to put my system together.   If I can get a working iteration of it before the conference I'd like to try it on someone's "artificially stricken" sub if we have time.   It is designed not only to raise the sub to the surface completely standalone of the sub's own ballasting system, but in a controlled manner and also, to provide enough freeboard at the surface for safe evacuation and sub stability.

What I need from you all....  
1) A rough idea of how many pounds of positive buoyancy would be required to raise your stricken sub.  Note: im not looking for the dry weight of your sub, rather the um..."wet" weight, your buoyancy displacement when fully deballasted including your dropweight.
2) If you think this is stupid or not... tell me.   I've already got it all figured out, have already begun purchasing supplies.


Ken

I wasnt sure yet if I was intending to produce a completed product, and market it extremely affordable to the Psub community, or if I just want to get units out there to our various locations in order to add an extra degree of safety for all my water-faring brethren... 


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