Boat compass...

MystyBlue2

MystyBlue2

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Hi folks im planning on fitting a fixed boat compass with me wanting to go a bit further afield a think its time to install one for this upcoming season.

I already have a handheld compass in a dry bag incase my garmin decides to give in.

My questions are do they come calibrated? And can you check for calibration yourself or is this verified by a company that knows what they are doing? Ive never had a fixed one before so this is all new to me.

Can you literally just unbox and mount (away from elecs ofcourse) and forget about it and most importantly TRUST IT?

Thinking of this one...Any opinions?

A Set Compass Red LED Light Sea Marine Electronic Digital Car Boat Truck Black | eBay

Cheers
 
In theory you find a local compass swinger to come out and do a test for you.

In reality I doubt whether many of us do that - I’ve had two boats from new, either of them swung. Common sense on mounting, and cross reference to the other nav equipment.

If you have a clear day go out and compare your new compass to your handheld and to the compass on your phone.
 
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girlofwight said:
In theory you find a local compass swinger to come out and do a test for you.

In reality I doubt whether many of us do that - I’ve had two boats from new, either of them swung. Common sense on mounting, and cross reference to the other nav equipment.

If you have a clear day go out and compare your new compass to your handheld and to the compass on your phone.
Click to expand...
Nice one thank you very much ? ?
 
Thanks for your helpful comments folks.

Well seen as i have NO clue what im doing looks like i will have to get a company to do it for me.

On the plus side it will be 100% accurate and i know its done properly, Way i see it, It will be as good as a chocolate fireguard if its not accurate and might as well not have one in the first place.

I'll speak to a friend of mine hes a retired RYA instructor and see if he could help or point me in the right direction of a swinger.

Cheers folks ?
 
Dan208 said:
Thanks for your helpful comments folks.

Well seen as i have NO clue what im doing looks like i will have to get a company to do it for me.

On the plus side it will be 100% accurate and i know its done properly, Way i see it, It will be as good as a chocolate fireguard if its not accurate and might as well not have one in the first place.

I'll speak to a friend of mine hes a retired RYA instructor and see if he could help or point me in the right direction of a swinger.

Cheers folks ?
Click to expand...

Don’t call him that! You need a Compass Adjuster.

They can be found at commercial ports as merchant ships still need to have their magnetic compasses swung and adjusted.
 
Compass adjuster probably in the phone book if such books still exist in your local.

for a small GRP boat. Compass on center line clear of electronics or ferrous metals should be fine.
even off centered unlikely to be a problem on a GRP boat unless there is a lump of metal near by.

For simple check.
take boat out with your hand compass and new fitted steering compass.

you can use a transit to check error.

taking bearings of the transit when steering on each of the cardinal and inter cardinal courses.

or

you can pick a prominent object at least a couple of miles away.
and
while steering on each of the cardinal and inter cardinal course.

add all the bearings up divide by 8 should give you the magnetic bearing of the object.

Plot the error on each magnetic bearing for each cardinal and inter cardinal on a graph.
it should be a nice sign wave pattern equal on both sides.

if it doesn’t equal out there is an issue with what’s known as an apparent E (coefficients get complex and make my head hurt)
the most likely cause.
you turned to fast and the compass didn’t get a chance to catch up.

so try it again turning a bit more slowly,

if it persists there is something offset to one side on the boat causing the error and you will need a chap who knows what he is doing to help.

Chances with a small GRP boat you will not need to compensated by adding corrective magnets are pretty good.
 
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Deviation may not be the same for each point of the compass if you have boat interference. I'd swing it myself against the chart plotter every 20 degrees of travel and note the difference. A compass does not have to be extremely accurate to bring you home. Go on try it. When the mist descends or you loose any sightlines you will end up steering a zig zag course. It's inevitable, as your steering becomes reactive as opposed to proactive. Use the compass, and as you close in, a depth sounder to bring you in if there is any deviancy by following a contour line on a chart. However at the end of the day it would be much safer to have something like Navionics which is dirt cheap for what it is (even just plain old google maps) on a smart phone as a redundant measure against chart plotter failure. Keep it on a USB charger for the duration though, it chews batteries.
 
Well all I wanted it for was if i was couple of miles offshore and fog blew in and i lost sight of land it was just going to point me in an appropriate direction until i can see land again and then when i can see land i can work out where i launched from by eyesight.

I have a mounted garmin gps and nav.

Backup navionics on a tablet and smart phone in waterproof cases.

And ive just downloaded a compass from the android play store....im starting to think a mounted compass is pointless for the distance i plan to go and with all of the devices i have as it would be really bad luck if the all failed at once

Also my wife and my brother (either one is always a passenger) has navionics and compass downloaded too.

It seems too much hassle for what its worth especially when i have other programs aboard to do the same kind of job.

Do you think its still necessary to have a mounted compass or will the devices i have suffice?
 
If you don’t already have any why not get a pair of binoculars with a bearing compass? Two for the price and storage of one.
 
Are you proposing to go out in a boat without a compass that does not rely on electronics ?

"Too much hassle" ? It is more like imprudent seamanship.


There is no need to bring in an adjuster; I think you are aiming for too much precision. Course to 5 degrees in a small boat is more than can be expected. Buy a decent deadbeat compass that is 'tuned' for N or S hemisphere, site it sensibly away from large chunks of metal, don't go near it with beer cans or metal-rimmed specs, run up a deviation card (20 minutes work, max), and then if all the electronics are attacked by gremlins, you have a way of getting home.

The only problem with a compass is if the boat is hit by lightning, and then there may be other priorities.
 
Most small boat compasses are only graduated in 5 deg intervals, so any fine adjustment is a waste of time and a compass adjuster a waste of money. -, if it is placed off the centre line you will have an unsymetric deviation anyway (similar to coefficient 'A' -, to those who know!).
Just get to know your compass by comparison to your other devises.
 
A compass without charts is ropey and thinking you will see land when you are close to shore is also a phallacy. When the mist rolls in you quickly become blinded and hopelessy disoriented.

Those electronic Nav aids become priceless. You can put yourself on a dime even in rocky and treacherous waters.

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A curious thing about sea mist. All of my crew without fail get seasick and start playing bucket wars. If you are prone to seasickness avoid going out when there is a mist forecast. As I said it quickly becomes disorientating.
 
Yeah i got cought out about 5years ago in a small SIB about 1mile up and 1 mile out from where i launched from.

I instantly went from a man to a boy wanting his mummy as i felt the color drain from my face and the feeling of dred came over me as it was the VERY first time this had ever happened and i NEVER plan to ever do it again.

Like most things on my small boat i want it for "another measure of safety" than daily use. Its always a "just in case"
 
I laugh. I dont have auto pilot so steer by compass using the charts for reference. As a result my heading is a series of 15 to 30 degree arcs everytime I take my eyes off the compass. There is usually a gaggle of boats behind me. All of which have autopilot, but no, they'd rather wander a zig zag course in my stern wake as I make six knots blowing my horn every 30 seconds incase some numpty comes roaring out the mist. It appears they consider Formula's as expendable. :confused:
 
BruceK said:
Deviation may not be the same for each point of the compass if you have boat interference.
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And changes as metalwork on the boat gets magentised.

Dan208 said:
Yeah i got cought out about 5years ago in a small SIB about 1mile up and 1 mile out from where i launched from.

I instantly went from a man to a boy wanting his mummy as i felt the color drain from my face and the feeling of dred came over me as it was the VERY first time this had ever happened and i NEVER plan to ever do it again.

Like most things on my small boat i want it for "another measure of safety" than daily use. Its always a "just in case"
Click to expand...

Similar, but I was caught by fog half way across the Straits of Gibraltar in the middle of the TSS.
 
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