Sestrel Moore compass on steel boat: refurbish or get new?

[phipseml]

Hi,

We have an old Sestrel Moore compass that came with our 40 foot steel boat. It doesn't work as it is now since one of the welded on correction magnets fell off, but it is possible to get them as spares from sirs.co.uk.

My question now is if it is worth fixing it, considering it's intended to be used on a steel boat. As I understand it, specific steel boat compasses have large steel balls on each side to compensate for magnetic influences of the hull etc., and the Sestrel Moore does not have this. Does anyone know this type of compass and can explain why i was fitted on a steel boat?

Another question is the positioning of the compass. It was originally fitted on the cabin roof, I suppose to keep it away from steel - which doesn't work since the cabin is made of steel, too. I was considering the steering pedestal, but that's steel, too, with a heavy chain from the wheel inside. Any suggestions on how to solve this, with either the Sestrel Moore or a new compass?

Cheers,
Phil

[PaulSommers]

Replace the missing part, or better, replace the entire compass with a Ritchie compass that comes with two iron balls bolted onto fittings with slots so that they can be moved closer or further away from the compass. You said that that your original compass had welded on balls, which sounds like a system that cannot be adjusted. The whole point of the balls is to create a way to adjust the compass for the deviation created by the steel on the boat. Put the compass on your pedestal to maximize visibility when steering by compass. It has to be mounted exactly in line with the fore/aft axis of the boat or the adjustment process will not work. Then hire a compass adjuster to do his magic to get the balls and the internal adjustment mechanisms of the compass in the best location given the surrounding steel objects.

[phipseml]

Hi Paul,

Thanks for your reply. The Sestrel Moore doesn't have large iron balls on the sides, only four small magnets underneath the actual compass, I assume for heeling error correction. See this link for an example: SESTREL "MOORE" TYPE COMPASS . The guy who built this boat usually did a good job in fitting the right gear the right way given what was available in 1988, so I wondered if this compass is a good one for the purposes even though it has no balls.

Also finding a specialist to adjust might be hard where we live (small town in northern Norway), so we might have to try to adjust the compass ourselves as good as possible, and get somebody when we cruise somewhere else next summer to adjust it properly. But I haven't checked this yet, and there's lots of fisheries here, so maybe someone knows somebody who has a cousin...

I am considering getting a new one. I have looked at Ritchie compasses, which seem good. I think we would have to import one from the US to Norway, since I couldn't find a retailer in Europe, and that adds expensive import tax. Therefore I'm looking at Garmin Silva compasses, which don't make a good impression, and at a German brand called Cassens und Plath, which make a very good impression. Any quick tips on what else to look out for except big balls?

Our steering pedestal has a wooden lid to take off to inspect the chain inside - which is generally good. However, the lid is not completely rigid in how to put onto the opening, i.e. it can turn a few degrees. Not much, but maybe important when you say that the compass has to be exactly aligned?

Cheers,
Phil

[Wotname]

A couple of data points.

IIRC, the "balls" that are seen on a steel boat compass are made from soft iron and as such do not hold a permanent magnetic field. They are not always necessary and their use is best determined by a compass adjustor (or a magnetic surveyor). Sometimes only one is necessary, sometimes two and sometimes none. You can make them yourself if so inclined.

The magnets under the compass maybe for heeling error or horizontal error depending in what plane they are mounted.

A Flinders bar may also be used to correct for errors. This is vertical soft iron bar mounted below the compass.

I would be surprised if the correction magnet is welded on as welding would destroy the permanent magnetic force. They are usually glued into place. Mine where just held with "bluetack" for several years until I got around to using real glue (epoxy ). Soft iron may have been welded even though this would "harden" it magnetically somewhat.

The Sestrel is (was?) a good compass. It easy to check how good it still is by:
1. looking at the fluid - is it still clear and without bubbles?
2. is the legend (the numbers) still clearly readable?
3. is the needle point bearing still OK? Bring a small piece of steel near the compass until it just moves a little, 1 degree (or 2 at the most), now remove the steel and the compass should return back to the original heading. If it does, the bearing point is OK. If you have to move say 5 degrees before it will return to the original heading, the bearing is on the way out.

If the compass is good, then all other errors can be adjusted, either by an compass adjuster or by yourself if you some serious reading.

However these days many many sailors don't even bother to use a compass. BTW, I'm not one of them . So you could just not worry to much about correcting it and just make up a deviation deviation card from the raw (uncorrected) readings. Keep this card handy for the day you have to use the compass in earnest. The rest of the time, use it as source of relative bearing information.

[Wotname]

FWIW, here is some serious reading
http://msi.nga.mil/MSISiteContent/StaticFiles/HoMCA.pdf

But never fear, it is easier than this article would suggest. Read it and understand as much as you can, then look at the basics - "A" error, "B" error and "C" error.

"A" error is removed by rotating the compass horizontally and usually if you get the lubber line aligned fore and aft, there will be no "A" error.

"B" & "C" errors and are adjusted by getting N/S and E/W errors removed as much as possible with small correction magnets. Make a deviation card for remaining errors on cardinal points and the other semi-cardinal points and go sailing

[NSboatman]

Sestrel compasses are wonderful pieces of gear. I've seen many of them on steel boats too - they seem to be more adjustable/impervious to magnetic interference than standard binnacle type compasses. Not exactly sure why, but the one I had for many years had small compensator magnets on it that seemed to hold that thing rock steady.

I don't profess to know a lot about different compasses in relation to each other - but I did really like that sestrel.

One minor issue I had with it was that the mounting seemed to be a magnet for catching lines - the hook arrangement isn't great if there is any possibility of a line sweeping the cockpit. I actually ripped it off the cabin top once, but thankfully grabbed it before it went over the side!

...imagine that call - "...um, excuse me, passing freighter - do you have a spare compass I can borrow? mine went away...". Yikes!

good luck!

[boden36]

I have found an electronic VDO Fluxgate compass really good on our steel yacht. We have had it mounted about 6ft up the mast for about 25 yrs and it has not given any trouble.
Our hull causes so much deviation that a standard compass was pretty useless.

Regards,
Richard

[Boracay]

Boracay came with an old Suunto compass that had been "modified" to suit the steering pedstal. I checked it out and it didn't look too bad but it was never going to give the accuracy needed for proper navigation.

I would have put in a fluxgate compass but at the time they were pretty esoteric and very expensive. Just had a quick Google (limited to posts in the last year) and quite a few basic units showed up. They were all battery poweered but one had a note that it used very little power and a backup battery was easy to arrange. Some had their own display and others integrated into plotters and autopilots. The most expensive looked to cost more than a quality steel boat compass but several looked to be much cheaper.

So my suggestion is to check out the deviation on your current compass. If it's consistent then consider if you can live with it or do a deviation card. Swinging a compass was an art I never managed to understand. It looked time consuming and expensive and maybe not neccessary in this day and age. Something about filling those hollow steel balls with steel shot.

In practice I found that initially setting the course on paper charts, then setting it up on the plotter and using the Mk I eyeball and the existing compass gave enough information to set an initial course and once clear of all obstacles and the boat was alighned on the course set up on the plotter I'd dial in the course into the autopilot and make fine adjustments until the track corresponded with the set course.

The information from the magnetic compass is allways good to have but I've never used it as a primary navigation tool. This is the 21st century after all.

[David M]

The hollow steel balls on each side are called quadrantal spheres. They correct quadrantal deviation which is the horizontal component of the earths magnetic field induced into the iron of a steel hull.

[phipseml]

Hi everybody,

Thanks a lot for your advice, really appreciated.

Just to get the welded on magnets clear: there are four horizontally aligned small pieces of pipe under the compass which are welded or maybe glued on, as you mentioned. They contain small magnets which positions can be adjusted lengthwise in the pipes with plastic screws. One of the pipes fell off and is gone. There is also a small vertical magnet of some sort - could that be the Flinder's bar? Maybe 2cm long. You can check out pictures of the Sestrel Moore in the internet to see what I mean. The compass is in the shed now, but I'll go and check more details this week.

In case the fluid and bearing are OK, it seems that it might be worth getting the spares and refurbishing the existing compass, which is good news. It's impossible to make a deviation card as it is now, since it always shows 270 deg and at a certain angle jumps to 80 or so. Also, as mentioned, getting a professional adjuster is likely not possible here, but we might do that once we sail south to civilized worlds.

I am not very comfortable to rely on electronic navigation only, especially when a great alternative like a magnetic compass exists which doesn't rely on power - this type of independence gives me peace of mind, and I like non-electric appliances that do the same job. And in fact I think it's even a bit easier to steer after and to communicate with inexperienced crew where to go with a real compass. We do use chart plotters and eyeballing for coastal cruising at the moment, but it almost feels a bit like cheating and I feel some of the fun is missing. We will get our first off-shore experience next summer, but I imagine when following the same course for days it's a bit unnecessary to have electronics running all the time if you have a _reliable_ non-electronic alternative that gives you the same information? It's just personal preference, and for me sailing is all about total independence, and the compass is just one part of it.

Cheers,
Phil

[David M]

I agree with you on having a non-electronic very reliable instrument that gives you heading. Having a backup and one more tool in your navigation bag is always a good thing.

I would hire a compass adjuster to adjust your compass. Hire one that uses the Magneuto system for producing a deviation table. It is not necessary to swing the boat with this method. And yes, it is approved by the USCG for commercial inspected vessels. You don't see ships out there being swung, and they do have at least one magnetic compass that backs up their gyro compasse(s).

A well adjusted compass will get you under 10 degress of compass error (deviation). The compass adjuster will tell you what magnets you need, what each one is and does and where it goes. They will also adjust the distance of the quadrantal spheres from the compass.

All magnetic compasses need to be adjusted periodically and a new deviation table made, because the deviation does change over time.

[gjordan]

In the 80s, I bought a 37 foot steel boat. I dont remember the compass brand, but I decided to have it professionaly swung. We went out and motored around, and lined up with known marks, etc. Made up a deviation card that was larger numbers than I wanted, but figured I could deal with it. On my first real sail, I discovered that the deviation would change for every little angle of heal. It had the vertical magnet under the compass, but it was horrible. I installed a remote sender on the mast and a readout in the cockpit, which worked OK. Left for Bermuda, and the electronic compass only lasted a day or two before it packed up. I would figure out what course we were on by going to the mast and standing as tall as I could, and holding up my hand bearing compass. This was a very poor system, but Bermuda came up on the horizon, just like it should have, and it got me through almost 2 years of cruising, so it can be done. I am not a lover of expensive/high teck electronics, but on a steel boat, I think that a good remote compass, and/or a couple of simple GPSs that give you course made good, are really necessary. Just make sure one of them is battery powered and have back up batteries. Just my 2 cents worth. ______Grant.