[PSUBS-MAILIST] G.L. Summary Stability & Buoyancy

Thu Dec 5 12:47:14 EST 2013

Which suggests a big inner tube if you want to convert a DW2000 to that definition. Otherwise, keep the door shut, or prepare to swim.
Vance

-----Original Message-----
From: Phil Nuytten <phil at philnuytten.com>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Thu, Dec 5, 2013 11:11 am
Subject: Re: [PSUBS-MAILIST] G.L. Summary Stability & Buoyancy

The minimum hatch to waterline measure applies to those submersibles ‘intended to be entered while afloat’ - 
Phil

From: Jon Wallace 
Sent: Thursday, December 05, 2013 7:33 AM
To: Personal Submersibles General Discussion 
Subject: Re: [PSUBS-MAILIST] G.L. Summary Stability & Buoyancy

I think the first sentence is key, "Submersibles will be assigned Class only after it has been demonstrated that their buoyancy and their static and dynamic stability in in tact condition is adequate FOR THE SERVICE INTENDED".  Some of the lack of specificity is because they can't conceive of every possible application.  They do however have quite a few specifics as you outlined.  Some of the testing won't apply (ie fuel load) and it's possible that a narrow scope of service might lower number of tests required.

On 12/5/2013 4:08 AM, Alan James wrote:

I'm afraid there is   nothing simple in this section. It is lacking in a lot of specifics.

There are statements   such as "shall generally meet the standard defined

in the following   unless special operational restrictions reflected in the class

notification allow a   lower level. & ...Depending on the type of submersible & the 

operation area, the   distance between the waterline in fully surfaced condition

and the upper edge of   entrance openings, air pipes,etc. which may be open

for surfaced   operation, has to be approved by G.L.

   ABS has   a minimum distance from the waterline to the hatch opening of 30"

whereas G.L. states;   For surfaced; a   minimum distance between   metacentric height & center of gravity of 10cm. (4")   And for submerged, a   minimum distance between center of buoyancy & center   of gravity of 5cm (2")   (same as ABS). At no stage will G be above B. (including after dropping the   drop weight)

In   the initial paper work sent before construction, a detailed analyses of   stability is to

be   included.  This   takes the form of analyzing the heeling levers of 10 different load cases in   fresh & salt water, 6 on the surface & 4   submerged & at 6 different heeling

angles. So looks like   120 calculations. Heeling forces from   free liquid surfaces, turning circles, wind, ice loads, transference   of   equipment & personal & payloads from working devices have to be   considered.

There needs to be   sufficient ballast to keep a minimum of 10% of the pressure

hull out of the water.   The draught line has to be marked on the hull. 

When one major ballast   tank is damaged the hatch has to be able to open without

water coming in &   the heeling angle shouldn't exceed 22,5 degrees.

There is an operational   in water test at the end of construction with evaluation

of the center of   gravity upon which the pre build calculations were based.

Alan

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