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I was of the impression and one given to me by a few ex US navy sumariners I have chatted with that the larger sails of the US submarines increased the snap roll probability due to the fact that although it might have a larger lever action it also generated lifet. We all know that underwater in a turn due to the bernoulli effect (spelling?) you get lower pressure on the side of the sail that is on the inside of the turn, thus the sub rolls in that direction, much like how a wing generates lift. It is from this that I surmised that although Russian sails being squater would have less of a lever moment they would generate less "lift" on the inside of the turn and thus not roll so much.
Hmmm, any of you ex subbies here able to help me out.
You got it right.
It's called 'foil roll' and is different from the vortex shear that precipitates the infamous 'snap roll.'
Foil roll is incremental and is proportionate with the boats angle of attack about the yaw axis as the rudder is put over. Snap roll is sudden and dangerous.
Class design evaluation (physical and computer model runs) and post build, pre-commissioning trials of the lead boat verify or modify the projected handling characteristics. The findings are working into a ships characteristics book that defines the boats performance envelope: such-and-such will happen if you do this-and-that.
These perimeters are drilled into the Ship Control Party. Foil roll, snap roll, c.g./c.b./c.p. shifts and the like are understood in the context of what they mean to ship angle, roll, response, speed, recovery times and excursion depth anticipated. Recovery/avoidance moves are constantly drilled on in both a shore-side team-trainer simulator and aboard the boat.
Simply put, the Conning Officer directs his ship control party to stay out of situations that do bad things to the boat. Where the bad things hide is known, it's simply a matter of running the boat so as to avoid straying into those bad places.
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That's a reply to a post I made on another forum where there are quite a few ex US navy submariners.
It seems we are confusing 'snap roll' with 'foil roll' Snap roll being a sudden departure foil roll being a result of water flowing round the sail as described in the quote. Size of sail does influence how much 'foil roll' you get and therefore Russian subs suffer from it less.
This is shown with further clarification below.
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OK so it doesn't cause snap roll, but a taller sail does produce a larger bank and would I be right in assuming at a higer rate of roll too for any given speed?
Yup.
Skipjack is the worst.
David,
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Also I was passed on a message to the effect that the Alfa had no problems making full speed turns...