NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Automatic deviation calculation by electronic compasses
From: George Huxtable
Date: 2009 Nov 25, 00:45 -0000
From: George Huxtable
Date: 2009 Nov 25, 00:45 -0000
Joe Schultz described fluxgate compasses as "First tried at the fleet level in the first gas-turbined frigates (US Navy) at least 25 years ago." To which I replied- "I wonder: were those "first gas-turbined frigates" that Joe refers to, built of steel? If so, I'm interested in what, if anything, was in place as a first-order correction for deviation, if these were, as Joe's words "self-correcting" compasses. Did they have the familiar correction magnets, and the hollow soft-iron spheres placed to port and starboard of the compass housing? I would be surprised if any electronic correction algorithm, such as we have been discussing, was capable of tackling the enormous deviations that a steel vessel gives rise to, without some such first-order corrections." And Joe has responded-"Yes, George, US Navy ships are made of steel. Very, very special steel..." ============== Well, it wasn't such a dumb question as that. Some Royal Navy vessels have been designed with aluminium-alloy superstructure above a steel hull, (with fatal consequences in the Falklands war). Which would reduce, though not eliminate, the need for correction for induced magnetism. And he added- "The advantage of these "electronic" compasses is that you can put the sensor assembly anywhere you want - no need for "Navigator's Balls." Find the sweet spot and put it there." Tell us how well that works, please, Joe. I can see that a remote-reading compass can be put at the top of a mast (with which warships bristle) and that could perhaps move it far enough away from hull-influence, so that internal-correction might suffice. But can Joe's "sweet spot" be located anywhere below (where accelerations will be less) in a steel hull and still avoid the need for the iron balls? Joe seems to be speaking with some authority on this topic, and I hope we can discover more. George. contact George Huxtable, at george@hux.me.uk or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. -- NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com