RE: [PSUBS-MAILIST] FW: sub ops

["Hugh Fulton" <hc.fulton@gmail.com>]

Sean,
Under ABS rules there is a stability check for maximum movement of personnel
etc within the confines of a sub. It would be an interesting excercise to
have that comparison made on BG or a Kittredge design under 7-10.2 of ASME
PVHO. This is for underwater stability but righting moments etc for on top
with metacentric height etc can be calculated.  This is one of my big
concerns.  I think I remember throwing out that thread on stability some
time last year but there was no interest at the time. I am considering
putting a diaphragm on the base of the MBT so that in the event of a tail or
nose entanglement blowing of the MBT's will not result in burping at a
severe angle. 

After testing of the Comsub I have tried to alter the various components
like an Ali rudder instead of SS as the moment was too great and it was tail
heavy on test, also increased drop weight, lighter batteries. However these
are minor changes to what you are alluding. Hugh




-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Sean T.
Stevenson
Sent: Monday, 17 January 2011 12:41 p.m.
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] FW: sub ops

Dean - check your email settings.  Your messages are showing up in a 
huge font on my system.

As for your comments - I'm sure every designer has their reasons for 
keeping their designs as light as possible, but it is an interesting 
thought exercise to consider the actual downsides to incorporating 
larger main buoyancy tank volumes, in conjunction with additional lead 
ballast, to increase the righting arm of any given boat for the same 
freeboard.  Lead is relatively cheap, and exterior MBTs would seem to be 
one of the easiest structural / mechanical retrofits that can be 
effected.  The obvious downside being the necessary power to drive the 
boat at the same speed, but for most PSub applications (Cliff excepted), 
we're not racing around down there.  Perhaps designing for sufficient 
stability to support a load on the weather deck is worth the additional 
displacement?  Even without changing displacement and ballast, it might 
be possible to lower the position of fixed ballast on a given design in 
order to increase stability?  I am curious to know if anyone on the list 
has, after completing and testing a sub, opted to make modifications in 
order to change the stability.  Comments?

-Sean




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