One compass, or two?

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Svip

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My Olsen Nimbus "Krydser" has tiller steering, so I will be sitting one side or the other, and not in the centre, like with a wheel.
Do I mount a compass on each side of the dog house bulkhead, or one in the centre, below the companoinway hatch?
If I mount one in the center, I won't be looking directly at it, and it will have the engine below it, not good.
If I mount one either side on the bulkhead, will they interfere with each other, being only about a meter apart?
Also can anyone recomend a good compass manufacturer? I want a glass sphere, not plastic.
Thanks, Svip /forums/images/graemlins/smile.gif
 
Go into a chandlers and put two compasses some distance apart, then get someone to bring one closer while you watch the other. I think you will find there is no change in reading until you getg within about 2 ft. I have a Plastimo sphere. I don't know if it is glass or plastic but it still looks perfect after 5 years (though I keep it covered when not in use.

A bulkead mounted compass usually has to be read edge-on which means you have to reverse your actions when steering a course. Make sure you are happy with that.
 
If you are on one tack, for a long passage for example, especially at night I have found that both parallax and distance from the lit bowl tiresome, so two compasses will at least resolve the parallax problem.

A better arrangement depending on your deck layout is twin, lit compasses flush mounted in the deck ahead and close to the helmsman, protected by a s/s bowl guard= easily seen even through rain
 
And then you spend

all your time trying to get the two to agree on all points of sailing in all areas oin which you sail.

Of course they're all magnetic compasses subject to the same anomalies (except the fluxgate reacts rather more strongly to a beer can ring-pull).

How about a gyro compass - ship it instead of ballast.
 
Re: and then you spend,One compass or two?

Thanks for the replies. Good idea Snowleopard! I'll pop into my local chandlers and play! I think I can get used to the anomolies.
Dylan, good idea, but......
I really want to get away from electronic gagetry, keep it basic, keep it simple. I spend my working life fixing floating "apartments" for people with no basic seamanship skills. Spend thier passages staring at a little flashing boat on a screen!
My boat is my escape from all that!
(Apart from a speed/depth log.)
 
Re: And then you spend

No parallax - but more difficult to steer to and when all my electronics go phut than I know my compass still works.

To answer the real question:

A compass in front of you is possibly easier to steer to - but most people get used to what is fitted. Most people very quickly get used to 'which way to steer'.

Obviously magnetic compasses do interfere with each other - but only when they get too close. Check the manufacturer - they will give safe distances.

Why do you want a glass sphere? A friend of mine has launched a submarine that he has built for a private American buyer (very wealthy!) . The main domes are made of a plastic polycarbonate type stuff, and if they are good for 500 Metres safe working depth, they will be good enough for your compass... Plastimo make very good compasses at a reasonable price and all their spheres are plastic.
 
Re: And then you spend

Actually I find the digital readout easier to steer by. Like on the jumbo jets I used to fly, I only have a magnetic compass onboard in case of emergency. It's a matter of choice.
 
Re: And then you spend

Hi John, I want a glass compass sphere becuase the plastic ones go yellow after too much exposure to the sun.
I live in Mallorca.
I'm thinking of going for the C. Plath compasses, these seem to be really good quality, and have glass spheres.
 
Re: And then you spend

Regarding the plastic going yellow a far grater problem is the fluid heating in the sun expanding and leaking through seals. So you have to cover a compass. As for 2 commpasses I wonder just how much you will be steering by compass? If you are so far from shore there are no landmarks you probably need an auto pilot. It seems to me that in these days of GPS an accurate compass course is less critical if you can use the GPS to correct steering errors. You might find a h/h GPS is cheaper than a second compass.
I think you will find the engine can be a problem for compasses whether centre or side mounted. I guess that could depend on angle of heel.
anyway go one compass and add another if you really need it in practice.
regards olewill
 
Re: And then you spend

Hello again John, you can't cover your compass when you're using it! I also have sailed, and worked aboard in the tropics, and nothing surprises me what the sun can do, anyway really for me, pshycologically, a glass sphere smacks of quality, and the Plastimo ones, although they would probably do the job just as good as a more expensive one, seem a bit Micky mouse! You have to ask yourself, how important is the compass, would you buy a plastc sextant?
William, using a GPS to correct your steering errors, instead of steering a good course, is a pretty dodgey thing to do? GPS should be treated as an aid, not a navigation tool.
I run a large motor yacht for a living, I have two seperate GPS antennas, running 4 plotters/radars, for all the wizardry, I only ever use them to take a position, to put on my paper charts.
Like I said before, my boat is my escape from electronics, satelite TV, air conditioning, vacuum toilets, and people who think boats are like apartments.
 
Re: And then you spend

your time happily misled by spurious accuracy of a digital readout?

I'd rather rely on a good old-fashioned, swung magnetic compass.

As already mentioned parallax is not really a problem on many compass installations.

I've had both for the last 14 years and found the magnetic rather more consistently reliable.

If I move cruising ground more than about 300nm I re-calibrate the fluxgate compass, usually you find a small difference in local magnetic variation - the size of the vernier scale on your average 120mm compass makes the difference almost indistinguishable.
 
UV degradation

of polycarbonate is negligible.

My Plastimo has been in the Med for the last 4 years (most of the time farther S than Mallorca) and the previous 11 years in the Western Approaches, and the bowl hasn't deteriorated. Rather the inclinometer lines have lost their white infill.

The trick is to use the plastic cover that comes with the unit - after all you spend 90% of your time stationary with no need to use the compass.

I suspect you'll have a fruitless search for a new compass with a glass bowl at an economic price.
 
Re: UV degradation

Yes, it's very easy to rely on the evil flashing boat! I agree Charles, it will spend more time covered than used. A Plath would be a little over twice the price of a Plastimo, but relative against the value of the boat, and I have to buy one (or two) anyway?
Anyway, thanks all, for helping me decide. It has to be one on each side of the bulkhead. I just need to check on safe distance apart.
But I would still like to know of any other manufacturers? Any suggestions?
 
My Plastimo Contest ...

Lost its cover 7 years ago and is exposed every day .... OK its UK sun - but it is as clear and good as first day.
As another has said - the white lines for incline wear away ...

I have about 1.5 - 2m between sides where compasses would be sited - IF I had twin installation ... my single is to port :>

April21_2005c.jpg


and I have no problem with reading from either side .... I also have a Suunto Commander HH compass in a bracket inside main cabin ...... which gives me a second compass station when inside etc. to check auto-helm / helmsman is ok !!

S_annejuly04003.jpg


which you can see just below the Navtex to viewers left of SWMBO ....


There is a third compass which is a "flat" Suunto tactical race compass ....very accurate that is designed to be fixed to a flat surface and read from above .... this sometimes I used to place under the tiller at the back of the cockpit .... This is not fixed and can be placed anywhere you want - just remembering to align lubber line with fore and aft.

My engine "top" is about 1m lower and to centre of my Plastimo contest and has little effect on it. Second my VHF radio is on the inside of the bulkhead behind the compass ... again little effect even when transmitting .... not often I might add.
 
Re: My Plastimo Contest ...

Two compasses! Perhaps becouse my boats have been very old and so the compasses twice my main steering compass has broken its expantion diaphram. The first a Danforth constelation, that slowly lost fluid, so i could have it repaired in port,
This year my cassens and parth hamburg diphram burst! I lost ALL the fluid within half an hour!! I have a second small main compass plus the fluxgate compass readout on my autohelm--not an idea main compass but at least it shows your heading!!
Definatly i would say for offshore sailing a second "main" compass plus a good handbearing back up

Ive been lost WITH a compass without i wouldent know if i had just found Corsica ir Italy for example!!!
 
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