NormanS
Well-Known Member
Oh, for goodness sake grow up, the pair of you. All this willy waving is getting quite tedious.
Steel boat as a long-term liveaboard (in a warm(er) climate).
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Oh, for goodness sake grow up, the pair of you. All this willy waving is getting quite tedious.
john_morris_uk
Well-Known Member
When someone arrives on here making expansive claims about their experience and sounding off about how their designs and building materials and techniques are superior to all others, and furthermore extolling the benefits of practices that are dangerous, it’s not willy waving to challenge their claims.
Im not the only one to point out the faults in his posts.
I’m sure Brent has some good experiences and valuable knowledge to share but he loses all credibility with some of his assertions. Furthermore some of his suggestions really are dangerous and need to be challenged.
john_morris_uk
Well-Known Member
There are lots of ways of checking the compass and producing a deviation curve for a boat. Steel boats present particular problems but none are insurmountable. The GPS only shows your ground track and even that is being averaged over a determined period. It doesn’t know which way your boat is heading. (Using the technical sense of ‘heading’ vs ‘course over ground’. )
Traditionally you swing a compass on a steel boat using a pelorus against a known mark from a known charted position. The large scale charts of Portsmouth Harbour used to have marks and bearings shown for exactly this purpose.
GHA
Well-Known Member
Possible but not ideal, gps gives you course over ground but not heading, if you're sure there's no tide then it works. Sestrel Moore is ideal for a steel boat, calibrate it and forget. No big deal. Using a hand bearing man sometimes get a bit annoying if you are trying to identify a headland or ais target, but not the end of the world. It's more likely to use a hand bearing compass to check for collision avoidance so it's more the change in bearing that's of interest rather than a precise reading.
Robin
Well-Known Member
Well said and politely too!
MY smartphone has a compass App that you wave around to calibrate, works on land not sure about a steel boat or if it could be trusted. I have successfully used GPS track to produce a deviation curve in tideless conditions once in Studland Bay, inshore, at slack water no wind, once in the tideless stretch.of the Vilaine above the Arzal Dam and below La Roche Bernard in S. Britany. In both cases later confirmed by pelorus, shadow pin and sun sights comparisons(and time from GPS!). Using the GPS track the boat needs to be on a steady heading and speed for 30 seconds or more at least for accuracy I also calibrated the speed log same time.lpdsn
Well-Known Member
On the contrary, I think John_Morris is doing a good job to give BS a fair hearing whilst challenging his statements where necessary. Doubt that would happen on other forums. In fact I'm pretty sure it wouldn't. I'm interested to see where it goes.
D
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SlowlyButSurely
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Yes but in practice how do you personally check your magnetic compass on your own boat.
We have a fluxgate compass on our boat which makes it really easy to swing the old magnetic compass which is a Sestrel Moore btw.
john_morris_uk
Well-Known Member
I swung a compass on a steel boat last year, but my current boat is GRP so it makes it a bit less of a challenge.
I find a mark where other fixed objects several miles away are visible.
I choose a position on the boat (usually standing on the aft deck near the backstay on mine) where I can use a hand earring compass. The boat is circled slowly in very small circles while a distant object is monitored through the hand bearing compass. The bearing to the object should remain constant and if it does then that shows there’s no deviation affecting the hand bearing compass at that position. You then start sighting up the centre line of the boat and comparing hand bearing readings with main steering compass readings. Plot a curve/apply corrections using the adjuster magnets as appropriate.
I invariably cross check everything. In other words I do a compass check by azimuth bearing when I get the chance, I check the autopilot reading against the ships compass (the autopilot flux gate compass is often well out despite being swung in accordance to Raymarine instructions and I always have to remind crew to set the course by the binnacle compass as it’s more accurate.). I also sometimes check the handbearing against the main compass as I’m a cynical old navigator who remembers sailing round with no electronic aids whatsoever.
SlowlyButSurely
Well-Known Member
Thanks for that explanation.
In addition to the above, when steering by the compass, we check the COG from the GPS against the expected track as I suspect most people with a GPS do.
Brent Swain
N/A
The course made good between noon sights does show course steered, and in mid Pacific there is not much to hit in the mean time. I always gave reported shoals a wide berth. Back then, GPS meant "Gray plastic sextant."
Brent Swain
N/A
If my ideas are dangerous, then why have they worked for so many people over decades, with no problems?
Seems your predicting the sky will fall, was disproved decades ago.
Brent Swain
N/A
Check it against your GPS course.
A professional compass adjuster here said fluxgates made more work for him than they cost him.
Brent Swain
N/A
Tried to upload my first passport ,1973 ,with all my "Port of Papateete "stamps, but I'm told it is too big to fit here.
Pictures I have already posted, cover the subject well enough.
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john_morris_uk
Well-Known Member
I’m afraid it doesn’t.
It doesn’t allow for leeway and drift from any ocean currents.
In fact it’s a particularly crap way of checking your compass and goes into the same box as ‘welds never fail’ ‘my steel never rusts’ ‘I only do two hours maintenance a year on my steel boat’ and ‘people who sail steel boats don’t need to get a lifer raft’ and ’you can easily close off the air supply and put out fires on steel boats’.
john_morris_uk
Well-Known Member
One swallow doesn’t make a summer. A few stamps prove nothing. I’m sure you’ve sailed across the Pacific, but I suspect that myself and many others are not so convinced by the multiple times you claim. You keep showing old photos of old boats from years ago. So what?
I’ve got old passports with stamps in them for all over the world, but so what.
Sorry to call your bluff, but the killer argument for me is nothing to do with passports. It’s the fact that all the other highly experienced sailors I know and have sailed with (and I know a few and they include some of the names you’ve mentioned!) are very measured about their responses to questions. In life living at sea and in yacht design and building there are lots of compromises and choices you have to make. Very experienced people know that and your fixation and single mindedness doesn’t seem to reflect the experience you claim.
Uricanejack
Well-Known Member
Mostly I don't bother my boats glass. From time to time I check my compass. Usually by taking a transit. I steer directly on the transit then I compares the steering compass to the transit on the chart. Pretty much any darn transit will do. This of course just gives me my error on that particular heading but routinely taking transits here and there tells me my deviation is pretty much negligible.
My Uncle and I had a big argument once upon a long time ago and far away. He asked me what compass course he should steer. So I told him.
He said it was bolocks.
I said it was right.
"If I steer that we will go aground".
"No you won't" "You will go down the middle of the channel".
"No I wont I'm heading down the channel right now".
"Then you don't need a compass course" " by the way there something wrong with your compass".
"No there isn't I just had it adjusted".
"The adjuster got it wrong".
Then my aunt found the hacksaw blade we had left beside the compass. "Do you think this will make a difference dear".
When she removed the hacksaw blade, everything was fine
My navigation his steering and the compass all agreed which way to go.
It's always worth while to check your compass JIK. If something doesn't look right then something is wrong, It might be me, or it might be the compass.
I also do the occasional amplitude or azimuth. If I'm in the mood.
As JM has pointed out steel is a bit more complex. Than my GRP or old wooden boat.
Checking the compass is one thing.
Swinging the compass another.
To swing a compass As JM said pick a good easily seen mark a couple of miles away. you don't want it to be two close or you will get an error.
What you need to check is your steering comass or main compass. If you can take bearings from it good if not you need to comare headings and bearing.
The advantage of a pelourus is you can put it in a place you can see 360 from and align with the boats centerline. The bearing you get will be relative. Doing it with a HBC still can be done but is probably less accurate.
Best to have at least one possibly two helpers. You need a steady course while you take the bearings. So someone steering for you.
Make sure you turn slowly or the lag of the compass will produce an error. Known as apparent E.
Traditional you do take the bearings in a particular order. It is important to do everything in the right order if you are going to fanny about with Lord kelivin's balls, magnets or Capt. Flinders bar (some of his surveys were still in use 30 years ago)
To get a devetion card you can start with any cardinal or inter cardinal. I start with N just because.
Start at N steer N steady and take the bearing while steering North. Write in Note book
Then turn to NE and repeat Followed by E, SE round to N Steer steady on each cardinal and inter cardinal and take the bearing.
If you used a pelorus all the bearings a relative bearing from your compass heading.
Convert the relative bearings to compass bearings.
Add all 8 together and divide by 8.
This will give you the magnetic bearing of the distant object you were using.
Compare each bearing to the Magnetic bearing and it will give you the deviation for each of your main and inter cardinals.
Plot these on a graph. It should be an equal wave each side.
Plotting it on graph paper the guestimating the deviation every 10 deg is quite easy. There is an actual formula for calculating the curve which I have long since forgotten.
Even compass adjusters usually just plot it.
So long as your deviations are small its all you need to do.
If its a wood or glass boat and there is a spike on your curve or its something is to close to the compass.
Even on a steel boat unless the compass is off to one side or the steelwork is unsymmetrical the deviations may be quite large but they will equal out on both sides on the line.
Adjusting the compass is best not done at home, Get an actual adjuster to do it.
Adjusting, Voodo Majic, and takes quite a while to learn. Compass adjusters tend to be a bit eccentric. Sort of like water diviners.
Actually if you understand all the different effects and coefficients it can be resolved mathematically cant say I ever really understood it.
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Uricanejack
Well-Known Member
I was on one when it was hit by lightning. Very loud, So loud and bright I was quite stunned, and blind.
And the compass was completely F!@#$%.
Uricanejack
Well-Known Member
A Whale sank a Maple leaf?
I have sailed a Maple Leaf. If I was going to sail offshore a Maple Leaf would be on my list of possibilities. Built like a plastic tank.
SlowlyButSurely
Well-Known Member
Any other damage? What about the electronics?
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