Failing to Adjust a Compass.

Robin said:
Only once ever used a 'pro'adjuster, as a package deal with several clubmates. What started as a compass with no obvious deviation detected became one with very definite error thsat he grudgingly had to return to correct blaming me for moving something when I had not. After the second visit we made a cross Channel trip and 'missed'by a mile or two west of intended landfall which, trust me, was rare to non existent before. Did a quick swing by handbearing compass and driving down a charted leading line in Cherbourg and yes there WAS an error again still. After that I bought me a pelorus, made a sun shadow pin and used that to make my own deviation chart on multiple headings round the clock when in a suitable stable place like a marina berth and with sun available. It took several weeks to collect all the headings and create the chart but after that all was well. Quite probably had I removed the magnets said 'pro had added I could have left it alone, but my card was with everything as left by 'pro' . It served me very well and proved very accurate. When we bought a bigger boat I made a 'temporary' card by comparing COG to compas on different headings at slack water neaps in a sheltered bay and again in a current free location in the Vilaine above Arzal Dam I also used the pelorus as before over many weeks and confirmed in fact my 'temporary' card created by comparing dGPS v compass V COG display was indeed pretty darn good.

Note 1 My exercise was to create a deviation card, not to adjust out deviation on all headings to zero.

Note 2 My pelorus was a Davies plastic one, bought in the USA for not a lot, later sold on YBW to another forumite, for less than a lot.
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My guy with the magnets got it so small the deviation card was fairly redundant.
 
Elessar said:
My guy with the magnets got it so small the deviation card was fairly redundant.
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someone later told me my guy was a renowned drinker-never book him except early mornings, after lunch is bad news. I Think ours never needed adjusting in the first instance, but once 'done' the card was essential. IIRC there was around 10 degs error on an easterly heading.
 
A quick update. We were moored in Bembridge heading 250 degrees on Sunday morning but the compass was reading 270 degrees and tempted me to have another go at adjusting it. Got it reading the same as the hand bearing compass while on the berth and compared the two on N, S, E, and W headings on the way back. All looks good (certainly much better than before) but I need to do a proper deviation card some time.
 
GHA said:
Slight thread deviation ( ;) ), but anyone using a raspberry pi can have an accurate compass for a few quid..

https://www.ebay.co.uk/sch/i.html?_...13.TR3.TRC2.A0.H0.TRS0&_nkw=MPU-9250&_sacat=0

Then have heading data on any device which can receive nmea over wifi -

AJldujQ.png
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Looks to me as though he is lost :nonchalance:
 
Daydream believer said:
If one bar passes through the other bar ( as it appears to do in the picture) then one bar cannot possibly rotate
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Looks to me like each bar has a bevelled cutout in it so that they can fit together more closely. Of course they still can't have their centrelines passing through exactly the same point, and so the bar running up and down the picture is sitting on top of the one running across.

Pete
 
I have a Sestral gimballed grid compass. There is a section below the compass that is held by 4 small brass screws that are corroded in place. Before I risk breaking them off & having to drill them out & fit new ones, can anyone please tell me if the adjustment is done in the void enclosed in this area.
 
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