Magnetic Compass Dinghy Install

   I'm planning to install a Silva 103 on my Spice using a Selden Mast Mount. I know that ferrous metal fittings can cause deviation, and I know that stainless steel, while barely magnetic is still a ferrous metal alloy. However, how much effect (if any) are things like ss kicker fittings (no wire rope just dyneema) going to have, and should I use brass bolts to fix the compass to the bracket or are ss ok?

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Sam.Spoons Send Private Message Find Member's Posts Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3400	Post Options Post Reply Quote Sam.Spoons Report Post Quote Reply Topic: Magnetic Compass Dinghy Install Posted: 25 Jan 17 at 2:24pm
	I'm planning to install a Silva 103 on my Spice using a Selden Mast Mount. I know that ferrous metal fittings can cause deviation, and I know that stainless steel, while barely magnetic is still a ferrous metal alloy. However, how much effect (if any) are things like ss kicker fittings (no wire rope just dyneema) going to have, and should I use brass bolts to fix the compass to the bracket or are ss ok?

Noah Send Private Message Find Member's Posts Really should get out more Joined: 29 Dec 04 Location: United Kingdom Online Status: Offline Posts: 611	Post Options Post Reply Quote Noah Report Post Quote Reply Posted: 26 Jan 17 at 10:15am
	I've never considered potential variation in my dinghy compass, which happens to be a tacktick. Given that we're never out of sight of land (excepting fog!) and its use is tactical, not navigational, I think any errors are irrelevant. Happy to hear conflicting views though...
	Nick D-Zero 316

pondlife1736 Send Private Message Find Member's Posts Posting king Joined: 17 Jan 14 Online Status: Offline Posts: 106	Post Options Post Reply Quote pondlife1736 Report Post Quote Reply Posted: 26 Jan 17 at 6:20pm
	Marine grade austenitic 316 stainless steel should be OK as it is barely magnetic. The problem is when it is cold worked or welded which can change the micro-structure into ferritic, ie much higher magnetic susceptability. Easy to check with a magnet though.

Time Lord Send Private Message Find Member's Posts Far too distracted from work Joined: 03 Dec 13 Location: Warwickshire Online Status: Offline Posts: 301	Post Options Post Reply Quote Time Lord Report Post Quote Reply Posted: 26 Jan 17 at 10:33pm
	Or even simply putting the bit in question near to the compass and see what happens to the needle as you move the bit around.
	Merlin Rocket 3609

Sam.Spoons Send Private Message Find Member's Posts Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3400	Post Options Post Reply Quote Sam.Spoons Report Post Quote Reply Posted: 26 Jan 17 at 11:46pm
	Brilliant, WTF didn't I think of that will do.