Re: [PSUBS-MAILIST] Intact Surface Stability

["Gary R. Boucher" <protek@shreve.net>]

Just a thought here...

I have no idea what "Sea State 3" encompasses, but I would think the wave 
height (perhaps wind?).  The height of the hatch above the water would be 
the obvious factor in not taking on water.  But, that is given by ABS, I 
believe.  I would think that the values of, and distances between the CB 
and CG and the "righting" torque they produce would also be a factor.  One 
other factor that might come into this is the rolling Moment of 
Inertia.  To not use dive planes on my sub I have to have the CB and CG 
closer than most.  Thus, the amount of torque to say tilt my sub to 30 
degrees from vertical is considerably less than for most.  However, due to 
the concentration of mass in the hull (18 inch radius), the keel's mass, 
and the sail's mass, my boat takes applied force longer to obtain a 
rotational velocity.  Thus, it does not roll badly in the wake of a 
relatively large wave.  But be careful getting in and out and standing on 
the hatch.  At least get in and out quickly!

I know I am not answering the question.  But, in lieu of any guidance from 
ABS or others with knowledge on this, one might make an intelligent 
argument based on these factors.

Gary Boucher



At 08:13 PM 9/30/2002, you wrote:
>ABS Rule 3.19.1a states that "All submersibles are to have at least one
>hatch.  The unit is to have sufficient intact stability on the surface so
>that in the worst loading conditions when subjected to a roll expected under
>sea state 3 the unit will not take on water through any hatch."
>
>Can someone that classed a boat with ABS and met this requirement explain
>what calculations you can make to meet the roll constraint above?
>
>Cliff