The snap roll effect is discussed in Burcher and Rydill's book. Essentially, at any angle of attack other than zero, the foil shape of the conning tower fairing (necessary to eliminate drag) also creates lift. Thus, upon initiating a turn, the foil is presented to flow at an angle and the lift effect rolls the hull accordingly.
I had always wondered if one could use a rotary joint on such a structure to keep it oriented in the direction of flow at all times. I don't really know what the practical issues are, though. (i.e. how many structures are actually housed within the fairing, and what is the space requirement?) As an aside, I recently had another read through Phil Nuytten's patent on the Newtsuit joint, and the concept got me thinking - extrapolating that idea to much larger cross sectional areas, it is theoretically possible to create a modular vehicle of jointed tubular hull construction that could reconfigure itself to assume a particular structural configuration depending on the mission requirements - I wonder if that could apply to surface / subsurface operation?
-Sean
On Aug 29, 2008, bottomgun@mindspring.com wrote:
You have to be careful of asymmetrical fin surfaces if you are going to operate at speed. They cause a snap roll effect to the outside in the direction of the hull they are on. The US Navy would like to get rid of conning towers because of this effect. The need to stow masts and have a safe position above seas to operate the boat from on the surface has precluded this change. There is a great SNAME paper from the mid 80s that describes the snap roll issue. Depending on what speed you expect to go in an ambient, this shouldn’t be an issue.
R/Jay
Respectfully,
Jay K. Jeffries
Andros Is., Bahamas
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