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Originally Posted by Yskonyn
(curious now as how a sub keeps itself from rolling to a side in a turn).
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It has to do with the center of bouyancy being above the center of gravity. When submerged and in proper trim that is a HUGE 'righting force' that keeps the hull upright. A submarine is at its most unstable period when it is diving. If I remember correctly a 688 gets down to about 3 feet of difference at one point when first submerging and that is why they want to get down to PD fast on the dive. Anyone who has served on one can remember that about halfway through the dive the hull 'wallows' and seems to take a abeam sea rather badly. They always want to dive into or away from the wave movement if possible to lessen this effect.
Someone here asked about turning radius and how it is determined. It is rather complex but I will try to remember what one VERY enlighted LTjg on my boat taught me.
Pardon the crudeness of this, but it was shown me with drawings and I am going from 15 year old memories here.
There is a center of mass on the boat and the hull basically pivots on that point in all three axis. In nuke boats that mass would more than likely be the reactor plant and subsequent shielding. They are by far the single heaviest item in the hull. You have to measure the turning radius as a function of the distance from that center to the force that is causing the change in direction (the rudder). The same is true for the stern and fairwater/bow planes. The father away they are from the pivot point the GREATER force they will provide in a direction change for a given amount of exerted force.
Thus larger and more massive boats may well have a smaller turning radius. It all has to do on where the center of mass is that they are turning on. Also, the sterns swings out and the bow moves in the oposite direction, again, with someplace on the hull the pivot point. If the center of mass if NOT in the middle of the hull, IE father forward, then the turning raduis will be smaller as measured at the bow.
I hope this is not too confusing. It is a complex set of mathmatics and I had the pleasure of learning from someone who was working on his OOD quals and had all the actual number and drawings to work with. It was fascinating stuff at the time.