Pocket Transit Compass On a Steel Boat?

[micah719]

Anyone used one on a steel boat? Any good, or do I have to hop in the dinghy and pay out some line to take a bearing (ie impractical for anything but dinghy/shore work)? Used them before with non-vehicular ferrous objects nearby, but held a prudent distance away....just wondering how far away to hold 15 tons of steel...

Any input appreciated...

[conachair]

Originally Posted by micah719

Anyone used one on a steel boat? Any good, or do I have to hop in the dinghy and pay out some line to take a bearing (ie impractical for anything but dinghy/shore work)? Used them before with non-vehicular ferrous objects nearby, but held a prudent distance away....just wondering how far away to hold 15 tons of steel...

Any input appreciated...

I got an autohelm off ebay a while ago, like this one.

Autohelm Personal Navigation Compass for Yachting, etc. | eBay

Nice to have it, after experimenting it's not too far off in one corner of the cockpit. But the main reason I would ever see the need to use one would be to check on relative bearings of a big boat which might hit me. Ais does away with that need. But still nice to have onboard.

[micah719]

Grabbed this from the users manual:

http://www.raymarine.com/submittedfi...al_compass.pdf

§ Keep compass well dear of magnetic devices such as
loudspeakers.
In difficult conditions, take multiple bearings and average. The
fluxgate compass hasa resolution of 1°, and an accuracy of ±2°
or better.

The Brunton has accuracy of .5 degree, rare earth magnet, and can do a whole lot of nifty stuff like vertical angles, heights and inclines as well....just not a marine-specific device. One acessory is a non-magnetic tripod. Oh well, guess I'll have to try it and see what's better, rare earth magnet or fluxgate use on steel hulls. Hmm, might grab a Brunton weather station as well, it has a fluxgate iirc, and some rather nice weather data...

[Stumble]

This article may be dated, but 10 years ago was pretty up to date. Steel Boat Compass Problems

[Astrid]

I have a steel boat and use a compass with compensating weights--i.e., a compass intended for use on steel vessels:


Compassman,Dan's: Why Does My Steel Boat Magnetic Compass Come With Two Balls?

[micah719]

Hmmm, no steel balls on the Transit. The attraction of the pocket Transit was that it needs no batteries. It also has a nifty mirror for shaving while you wait for the attractive female USCG rescue swimmer to drop by. Not sure about how useful it is for taking sights, particularly in a small boat, but if not too rough I guess it can be used for measuring heights of landmarks, like hills, or bridges. Ok, sextants are used for that, but the Transit is waterproof and handier.

Thank you all for your replies.

[Astrid]

I have a Brunton very similar to yours except for being calibrated in mils, but have never tried to use it at sea. It's a bit too sensitive for use on a moving platform.

[micah719]

Hmmm, nice articles, thanks for the links....won't go gyro or fluxgate (other than handheld like conachair's), so it will have to be the ol' magnetic compass with compensators, and we'll see what the Transit does....at least useful for calibrating landmarks around an anchor point and then using these to check the main boat compass. Still, it's a nice little reliable gadget, and I'd like to be able to use it for bearings. That's another thing...anyone got a pelorus? I suppose we're going to have a chat about gimbals next...

[Astrid]

A pelorus is a very handy thing to have for taking relative bearings.

[gjordan]

I cruised about 5000 miles in a 37 foot steel boat. It had a large compass built for steel boats with the large correcting balls. Since the boat was tiller steered the compass was mounted to the rear bulkhead of the bridge deck, which is probably the worst position on a steel boat to mount a compass. The aft bulkhead of the cabin was also steel so that would have been no better. When I launched the new(to me) boat a friend came out and we motored around and adjusted the compass until it was close. I also had bought a remote mounted compass and put the sensor about 12 feet up the mast. I did some sailing around Long Island sound and didnt notice anything becouse it was all eye ball navigation. When we cast of for Bermuda it didnt take long to figure out that for every differant angle of heel the compass would change dramaticly. The remote was steady enough for decent navigation, but it packed up two days out. From that point on I would go to the mast with a hand bearing compass and yell back to the wife what our real course was and see what the ships compass read and keep it on that until the wind got lighter or heavier and then have to do it all over again. What a PITA! If your boat has pedastal steering the problem would be less but could still be a pain. Do I consider a good hand bearing compass imortant? HELL YES! The wife put her foot down at the end of a year and said no more steel boats. I still like steel boats but would do things differant if I had one now.____Grant.

[boden36]

Astrid's right, make yourself a pelorus, and your bearings will have the accuracy of your main compass.
Regards,
Richard.

[conachair]

Originally Posted by boden36

Astrid's right, make yourself a pelorus, and your bearings will have the accuracy of your main compass.
Regards,
Richard.

I have a pelorus but it's not very useful. The main compass (sestral moore) is calibrated only in it's home position which is under the sprayhood so you can't actually see anything to line it up with.

Though to be honest I can't think of a situation where I actually had to use a hand bearing compass. Pre AIS it would have been useful for relative bearings on ships, I used a couple of clothes pegs, one on the spray hood and one on the life line to keep an eye on the big boys. Smaller boats without ais are easy to dodge round anyway so not much of a problem.

But still nice to have a hand bearing one onboard and fun to play with, handy for identifying headlands when sailing along a coast.

[micah719]

Downloaded the manual on the Is-Was, a USN WW2 sub instrument used for tracking bearing, speed and course of another vessel relative to own vessel. Would be an interesting and easy project to make and a handy bit of kit to improve on guesswork. No batteries required, just some perspex sheets and a rivet. No, not the golden one.

Submarine Attack Course Finder Mark I Model 3 Manual

[S/V Alchemy]

I have the Richie Globemaster on my steel cutter. Beautiful thing and usually within a degree or two to judge by straight-line GPS runs on known bearing to distant landmarks.

My KVH AC103 fluxgate is a little better, however. Could be because its sensor is mounted atop the alu pilothouse roof.

I can get wacky bearings out of the compass in my Suunto watch on the aft deck, but if I hold it close to my eye, i.e. about five and half feet or so above the deck, the compass doesn't seem to be affected much by the steel deck.

[micah719]

Thanks, that's reassuring. Might build the binnacle out of wood or alloy, and keep the interference away.