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

[jimtoddpsub at aol.com]

Alan,
Thanks for digesting and presenting all that.  The summary and comparison of ABS and Germanischer Lloyd (GL) is very helpful.  Did you look at Lloyds Register (London) any?  Was there something that made you gravitate toward GL instead of LR?
Jim


-----Original Message-----
From: Alan James <alanlindsayjames at yahoo.com>
To: psubs.org <personal_submersibles at psubs.org>
Sent: Thu, Dec 5, 2013 3:09 am
Subject: [PSUBS-MAILIST] G.L. Summary Stability & Buoyancy











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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