Tugw
Member
Just a pasing thought really,But does anybody actually have a deviation card made up for thier boat? and what about compass correction? do this still get done?
Deviation
- Thread starter Tugw
- Start date
D3B
New member
Deviation card when she was new two years ago.
according to the gps they still appear about the same.
according to the gps they still appear about the same.
Kawasaki
Well-known member
I don,t think many do nowadays.
It is worth getting the Compass "swung" though.
So then You know it,s ok.
Most boats have so much gismos, mobile phones, toasters (sorry that was another thread some time ago about Guy who stuck loads of gadgetts onboard) and other leccie stuff close.
One begins to wonder if all that stuff would affect the Compass anyway!
Tend to use the Compass Myself.
Tend to use a paper chart.
Tend to look at the GPS/Plotter thinghy to check the Compass and leccie thing agree.
They usually do.
Compass wobbles(like they do) Gps / Plotter thinghy tends to catch up.
Have never used a Deviation Card.
Depends a bit on what Your boating trips are going to be I suppose.
Where I am based, tiss 65 miles ish before I hit another shore.
Except for crawling along the Coast.
IE ,Ireland is 60 away and IOM is roughly the same and Liverpool is about 50.
So not much in the way of Deviation is a big concern.
Unless I go to Portmadoc Yacht Club.
There are some real Deviants in there! /forums/images/graemlins/ooo.gif
It is worth getting the Compass "swung" though.
So then You know it,s ok.
Most boats have so much gismos, mobile phones, toasters (sorry that was another thread some time ago about Guy who stuck loads of gadgetts onboard) and other leccie stuff close.
One begins to wonder if all that stuff would affect the Compass anyway!
Tend to use the Compass Myself.
Tend to use a paper chart.
Tend to look at the GPS/Plotter thinghy to check the Compass and leccie thing agree.
They usually do.
Compass wobbles(like they do) Gps / Plotter thinghy tends to catch up.
Have never used a Deviation Card.
Depends a bit on what Your boating trips are going to be I suppose.
Where I am based, tiss 65 miles ish before I hit another shore.
Except for crawling along the Coast.
IE ,Ireland is 60 away and IOM is roughly the same and Liverpool is about 50.
So not much in the way of Deviation is a big concern.
Unless I go to Portmadoc Yacht Club.
There are some real Deviants in there! /forums/images/graemlins/ooo.gif
Solitaire
Active member
All MCA coded boats have to have a deviation card on-board. We recently had to change the rev counters on Motala due to the engine change - they are more modern than the old ones and we now to have the compass swung again - it's now 20 degrees out! The swinging of a compass and the resultant production of the deviation card is an interesting experience.
hlb
RIP
Sheesh, glad I have never been on any courses. I'd have just been swinging the wheel, right or left before the crash!! /forums/images/graemlins/laugh.gif
grumpy_o_g
Well-known member
What's he actually doing then? I'd always assumed you simply took a transit on something to make sure your boat was pointing where the GPS said it was and drove round in a circle measuring compass against GPS and putting in variation from the chart. That all looks very complicated and mystic to me.... /forums/images/graemlins/confused.gif
Solitaire
Active member
The boat is taken out - in this case into the middle of the Hamble at certain points and then a Pelorus is used as the boat is turned onto various headings.
The compass can be adjusted up to a point and then the deviation card is drawn up. In our case the compass deviation is not more than 1 degree East. That is until the new rev counters were put in - we have to go through the whole process again now.
The compass can be adjusted up to a point and then the deviation card is drawn up. In our case the compass deviation is not more than 1 degree East. That is until the new rev counters were put in - we have to go through the whole process again now.
nonitoo
New member
You should use a pelorus but practically you can use a hand bearing compass as long as it is operated in a position close to the main compass (usually above).
Run the boat along a known transit inwards and outwards and note the headings (easy). Cross the transit heading N/S and E/W if possible and also NE/SW/NW/SE and note the bearing reading of the transit. Compare this to the known transit bearing.
This gives the compss error and after applying the variation, hey presto, you have a deviation card.
Don't forget, error west - compass best, error east - compass least.
This method may not satisfy the purist because you are actually obtaining a deviation card for the hand bearing compass but, provided the hand bearing compass is used close to and above the main compass and where the main compass is only graduated in 5 deg increments anyway it is quite good enough.
Now, when it comes to adjusting the compass, I draw a veil over the arcane art of adjusting the quadrantal compensators and placing magnets to remove the various co-efficients.
Besides modern compasses only seem to have a couple of screws that I assume vary coefficients B&C - never tried it as deviation has always been acceptable.
Run the boat along a known transit inwards and outwards and note the headings (easy). Cross the transit heading N/S and E/W if possible and also NE/SW/NW/SE and note the bearing reading of the transit. Compare this to the known transit bearing.
This gives the compss error and after applying the variation, hey presto, you have a deviation card.
Don't forget, error west - compass best, error east - compass least.
This method may not satisfy the purist because you are actually obtaining a deviation card for the hand bearing compass but, provided the hand bearing compass is used close to and above the main compass and where the main compass is only graduated in 5 deg increments anyway it is quite good enough.
Now, when it comes to adjusting the compass, I draw a veil over the arcane art of adjusting the quadrantal compensators and placing magnets to remove the various co-efficients.
Besides modern compasses only seem to have a couple of screws that I assume vary coefficients B&C - never tried it as deviation has always been acceptable.
Solitaire
Active member
[ QUOTE ]
You should use a pelorus but practically you can use a hand bearing compass as long as it is operated in a position close to the main compass (usually above).
[/ QUOTE ]
Our compass was fine until we put in the "new" rev counters. Surely by simply placing the handbearing compass above the fixed compass the magnetic effect that has caused the fixed compass to deviate still exists?
You should use a pelorus but practically you can use a hand bearing compass as long as it is operated in a position close to the main compass (usually above).
[/ QUOTE ]
Our compass was fine until we put in the "new" rev counters. Surely by simply placing the handbearing compass above the fixed compass the magnetic effect that has caused the fixed compass to deviate still exists?
Gludy
Active member
I have a deviation card showing max 1 degree out so the compass was swung to within one degree - by the same chap as in the images above.
I think that it is a major safety feature to have an accurate compass - I once has my electronics go dwon and needed it to steer any sort of course.
There is no piont in having a compass unless its swing and you know the deviation curve.
I think that it is a major safety feature to have an accurate compass - I once has my electronics go dwon and needed it to steer any sort of course.
There is no piont in having a compass unless its swing and you know the deviation curve.
Poignard
Well-known member
Is the man in your photos a professional adjuster? If so, can you provide contact details?
oceanfroggie
Well-known member
Yes there's one on our Broom factory calibrated.
Might need to be reswung if you ever fit any new gear or do recabling anywhere near the compas. It's not as critical as it used to be because in the GPS and Autohelm era the compass is really only a backup, and the GPS's heading is more accurate (once your making way that is).
Also most modern Autohelms have a calibration process that will automatically calibrate and make corrections for the fluxgate compass. This involves driving the boat in circles in flat calm conditions and often a zig zag course, etc. The Autohelm will compare the electronic compasses readings with the true heading from the GPS and automatically adjust readings for every heading.
Might need to be reswung if you ever fit any new gear or do recabling anywhere near the compas. It's not as critical as it used to be because in the GPS and Autohelm era the compass is really only a backup, and the GPS's heading is more accurate (once your making way that is).
Also most modern Autohelms have a calibration process that will automatically calibrate and make corrections for the fluxgate compass. This involves driving the boat in circles in flat calm conditions and often a zig zag course, etc. The Autohelm will compare the electronic compasses readings with the true heading from the GPS and automatically adjust readings for every heading.
nonitoo
New member
Solitaire,
You either have to accept that new deviation values or twiddle the B&C adjustment screws beneath the compass and swing again to reduce these errors.
Alternatively move the compass away from these rev counters. This would be the preferred action as the errors caused by the new equipment seem to be rather high - too much to be adjusted out.
You either have to accept that new deviation values or twiddle the B&C adjustment screws beneath the compass and swing again to reduce these errors.
Alternatively move the compass away from these rev counters. This would be the preferred action as the errors caused by the new equipment seem to be rather high - too much to be adjusted out.
Andrew_Fanner
New member
Is it an expensive process? Looks feasible to DIY with transits etc but a bit of a palaver.
Gludy
Active member
On the south cioast is costs about £180 to do the two compasses on a flybridge boat - I was charged almost £500 because the boat was in Swansea.
I see it as very important to have a working compass. I have had the fluxgate on the autoheml fail and was out of site of land.
If you want a compass for more than decoration then it has to be swung and that takes a pro swinger to do ity - normally to withing one degree. My compass was 33 degress out on one heading and he still got it to one degree - so I can ignore deviation.
I see it as very important to have a working compass. I have had the fluxgate on the autoheml fail and was out of site of land.
If you want a compass for more than decoration then it has to be swung and that takes a pro swinger to do ity - normally to withing one degree. My compass was 33 degress out on one heading and he still got it to one degree - so I can ignore deviation.
billskip
Well-known member
Nice piccis ....but shouldnt the guy be looking out the window...!!!!! /forums/images/graemlins/laugh.gif
Solitaire
Active member
[ QUOTE ]
Is the man in your photos a professional adjuster? If so, can you provide contact details?
[/ QUOTE ]
He is - based in Hamble 02380453533, called Robinson, Farther and daughter operation.
Is the man in your photos a professional adjuster? If so, can you provide contact details?
[/ QUOTE ]
He is - based in Hamble 02380453533, called Robinson, Farther and daughter operation.
Gludy
Active member
And he is very good - normally adjusts to within 1 degree so you can ignore deviation.
He did the QU2 compass so he covers the range of boats /forums/images/graemlins/smile.gif
He did the QU2 compass so he covers the range of boats /forums/images/graemlins/smile.gif
Solitaire
Active member
[ QUOTE ]
Is it an expensive process?
[/ QUOTE ]
£125 plus VAT per boat
Is it an expensive process?
[/ QUOTE ]
£125 plus VAT per boat
Poignard
Well-known member
Thanks