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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