Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen

There may be some set screws on each or any side of that circular compass.
Usually to compensate for where you have to place it on your ship to correct
any magnetic conflict.

Try to place it on your ship where there will be no interference but that
may seem impossible. Install it where you like, which may cause this
interference and then adjust those screws (if it has them) to the true north
and that should take care of it.
Could depend on the southern or northern hemisphere compass. Where was the
compass originally purchased for? Some compasses have weights on the
opposite leg to the north in order to eliminate it from digging into to its
own board. For example, if you have a northern hemisphere compass, there
will be a little weight on the needle, this prevents it from digging in or
aiming right at true north (through the earth). But if you take that same
compass down to Australia, it will dig in and not be usable.
But in reality, when you go down to Australia, you are actually going up. In
relative prospective, Australia is actually on the top of the world, not
like the maps you are used to in grade school.







"Jürgen Spelter" wrote in message
...
Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen

I sure hope one of you "experts" out there will comment on this. I can
hardly wait.

" Tuuk" wrote in message
...
There may be some set screws on each or any side of that circular compass.
Usually to compensate for where you have to place it on your ship to
correct
any magnetic conflict.

Try to place it on your ship where there will be no interference but that
may seem impossible. Install it where you like, which may cause this
interference and then adjust those screws (if it has them) to the true
north
and that should take care of it.
Could depend on the southern or northern hemisphere compass. Where was the
compass originally purchased for? Some compasses have weights on the
opposite leg to the north in order to eliminate it from digging into to
its
own board. For example, if you have a northern hemisphere compass, there
will be a little weight on the needle, this prevents it from digging in or
aiming right at true north (through the earth). But if you take that same
compass down to Australia, it will dig in and not be usable.
But in reality, when you go down to Australia, you are actually going up.
In
relative prospective, Australia is actually on the top of the world, not
like the maps you are used to in grade school.







"Jürgen Spelter" wrote in message
...
Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen

You've got to do a compass swing to determine the effects of the ships
magnetic interference.

Quite a few steps and you need a means to determine the magnetic heading of
the ship usign an external reference, preferable but is probably beyond the
means of most of us. Alternative is a GPS set to magnetic reading or if you
have local magnetic variations, then you can use the true North and apply
the variation.

In the following steps, try to be as close to the cardinal points as
possible.

1. Point ship North, take compass reading. Take reference reading. Note
error. If compass underreads, error is negative.
2. Point East, note reading. Take reference. Note error again.
3. Point South, note reading. Take reference. Note error.
4. Now, calculate North-South compensation. Sum both error and divide by
2.
5. Point North or South (easier to keep the South you are in)
6. Ajust the N-S screw to change reading by the results.
Example,
North your compass reads 003 deg, your external ref is 359deg ,
error is +4deg,
South compass reading 185deg, external ref is 180deg. error is 5deg
Step 4 calculation gives (4+5)/2=4.5 degrees.
Point South, first reading 185deg (assuming you managed to get the
same heading), adjust N-S screw until you get 180.5deg (185deg - 4.5deg)
7. Note new South reading and external reference reading. Calculate new
error.
8. Point West, repeat readings.
9. Calculate correction like in step 4.
10. Point West. Adjust E-W screw like in step 6 and example.
11. Note new West reading and external reference reading. Calculate new
error.
12. Point North, take compass and external ref reading.
13. Point East, take readings
14. Calculate index error, sum all 4 errors and divide by 4.
15. Physically rotate compass mounting to corrent for the error calculate
in step 14.
16. Now go through all the 4 cardinal headings, preferably 8 (the 45 deg
positions) and note compass readings and tabluate a Steer-by card.
17. You should get reading that are slightly out by 1 or 2 deg when you
tabulate the steer-by card and set you heading to those readings and you
will get the actuals.
Example: If the Steer-by card says 46deg for NE, it means you are
actually pointing 45deg when the compass is reading 46deg

Hope this helps.

Tan PS


"Jürgen Spelter" wrote in message
...
Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen

Oh, I forgot to mention.

Before you begin, make sure that the compass adjustment screws are set to
zero and all electrical and electronics equipment that will normally be
turned on should turned on and operating throughout the process. Also mount
the compass as closely aligned to the fore-aft axis as possible.

For night equipment like Nav and Anchor lights, the wiring should be kept
away from the compass vincinity, if unavoidable use twisted wire pairs.
Check for any interference by observing the compass and turning the
equipment on/off.

Good luck.

Tan PS


"Tan PS" wrote in message
...
You've got to do a compass swing to determine the effects of the ships
magnetic interference.

Quite a few steps and you need a means to determine the magnetic heading
of
the ship usign an external reference, preferable but is probably beyond
the
means of most of us. Alternative is a GPS set to magnetic reading or if
you
have local magnetic variations, then you can use the true North and apply
the variation.

In the following steps, try to be as close to the cardinal points as
possible.

1. Point ship North, take compass reading. Take reference reading.
Note
error. If compass underreads, error is negative.
2. Point East, note reading. Take reference. Note error again.
3. Point South, note reading. Take reference. Note error.
4. Now, calculate North-South compensation. Sum both error and divide
by
2.
5. Point North or South (easier to keep the South you are in)
6. Ajust the N-S screw to change reading by the results.
Example,
North your compass reads 003 deg, your external ref is 359deg ,
error is +4deg,
South compass reading 185deg, external ref is 180deg. error is
5deg
Step 4 calculation gives (4+5)/2=4.5 degrees.
Point South, first reading 185deg (assuming you managed to get the
same heading), adjust N-S screw until you get 180.5deg (185deg - 4.5deg)
7. Note new South reading and external reference reading. Calculate
new
error.
8. Point West, repeat readings.
9. Calculate correction like in step 4.
10. Point West. Adjust E-W screw like in step 6 and example.
11. Note new West reading and external reference reading. Calculate new
error.
12. Point North, take compass and external ref reading.
13. Point East, take readings
14. Calculate index error, sum all 4 errors and divide by 4.
15. Physically rotate compass mounting to corrent for the error
calculate
in step 14.
16. Now go through all the 4 cardinal headings, preferably 8 (the 45
deg
positions) and note compass readings and tabluate a Steer-by card.
17. You should get reading that are slightly out by 1 or 2 deg when you
tabulate the steer-by card and set you heading to those readings and you
will get the actuals.
Example: If the Steer-by card says 46deg for NE, it means you are
actually pointing 45deg when the compass is reading 46deg

Hope this helps.

Tan PS


"Jürgen Spelter" wrote in message
...
Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen

Tan PS wrote:
You've got to do a compass swing to determine the effects of the ships
magnetic interference.

Quite a few steps and you need a means to determine the magnetic heading of
the ship usign an external reference, preferable but is probably beyond the
means of most of us.

Not really, most ports have a compass swinging place set aside have a
look at the charts or ask. It usually has a set of posts you can tie to
& hold the boat on the various headings & "usually" they're sited so
there are at the very least a set of transits (2 or more landbased
objects that are on the chart & when in line mean your boat is pointing
to a known true heading as close to nth as reasonable given the
available transits)

Alternative is a GPS set to magnetic reading or if you
have local magnetic variations, then you can use the true North and apply
the variation.

Notwithstanding even some cheap compass manufacturers suggest this;
it's not a goer & indeed is just more of the dumbing down of things in
general.

A GPS has no clue which way the bow of the boat is pointing & this is
what you're trying to determine. All a gps can do is tell you your
history track across the seabed & clearly you need to be moving for it
to even be able to tell you that.. You might be moving sideways,
backwards or whatever the GPS will not know so can't tell you.

If you use this method it's OK for runabouts or gin palaces but yours
sounds like a proper boat & few boats travel through the water in the
direction the bow is pointed, even a slight cross wind will slightly
heel the boat so changing it's shape enough that it actually crabs
along, then if there's any sort of cross tide/current the game is off
anyway, so if you're serious DON"T use a GPS to swing a compass. The
object is to make you confident you know what your compass will read
when the bow is pointed in a certain direction, experienced boaters of
course know only too well that the boat won't be going there, but with
experience you can then make your course to steer adjustments from that
known starting point

I also note point 15 below??? DON'T ever do this, the compass must be
mounted so it's aligned with the boat's fore/aft centre line. It doesn't
need to be "on" or even near the centre line but must be completely
parallel with it. Otherwise every time you turn 180 degs the error will
just reverse & multiply. It's tempting for play boats but again not a
proper boat where you'll rely upon the compass as more than a talking
point at the club bar:-)


K


In the following steps, try to be as close to the cardinal points as
possible.

1. Point ship North, take compass reading. Take reference reading. Note
error. If compass underreads, error is negative.
2. Point East, note reading. Take reference. Note error again.
3. Point South, note reading. Take reference. Note error.
4. Now, calculate North-South compensation. Sum both error and divide by
2.
5. Point North or South (easier to keep the South you are in)
6. Ajust the N-S screw to change reading by the results.
Example,
North your compass reads 003 deg, your external ref is 359deg ,
error is +4deg,
South compass reading 185deg, external ref is 180deg. error is 5deg
Step 4 calculation gives (4+5)/2=4.5 degrees.
Point South, first reading 185deg (assuming you managed to get the
same heading), adjust N-S screw until you get 180.5deg (185deg - 4.5deg)
7. Note new South reading and external reference reading. Calculate new
error.
8. Point West, repeat readings.
9. Calculate correction like in step 4.
10. Point West. Adjust E-W screw like in step 6 and example.
11. Note new West reading and external reference reading. Calculate new
error.
12. Point North, take compass and external ref reading.
13. Point East, take readings
14. Calculate index error, sum all 4 errors and divide by 4.
15. Physically rotate compass mounting to corrent for the error calculate
in step 14.
16. Now go through all the 4 cardinal headings, preferably 8 (the 45 deg
positions) and note compass readings and tabluate a Steer-by card.
17. You should get reading that are slightly out by 1 or 2 deg when you
tabulate the steer-by card and set you heading to those readings and you
will get the actuals.
Example: If the Steer-by card says 46deg for NE, it means you are
actually pointing 45deg when the compass is reading 46deg

Hope this helps.

Tan PS


"Jürgen Spelter" wrote in message
...

Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen

Some clarifications.

"K. Smith" wrote in message
...

Not really, most ports have a compass swinging place set aside have a
look at the charts or ask. It usually has a set of posts you can tie to
& hold the boat on the various headings & "usually" they're sited so
there are at the very least a set of transits (2 or more landbased
objects that are on the chart & when in line mean your boat is pointing
to a known true heading as close to nth as reasonable given the
available transits)

You will have to keep the boat aligned and that's probably by keeping it on
the move along the line of sight. Tying it to posts that probably contain
steel reinforcements isn't a good idea. If you can keep it in a straight
line against a landmark, a GPS will work. Yes, you are correct about being
mindful of cross-track movements.


A GPS has no clue which way the bow of the boat is pointing & this is
what you're trying to determine. All a gps can do is tell you your
history track across the seabed & clearly you need to be moving for it
to even be able to tell you that.. You might be moving sideways,
backwards or whatever the GPS will not know so can't tell you.

The suggestion provided assumes a knowledge of GPS usage and remains a valid
suggestion.

I also note point 15 below??? DON'T ever do this, the compass must be
mounted so it's aligned with the boat's fore/aft centre line. It doesn't
need to be "on" or even near the centre line but must be completely
parallel with it.

The steps preceding 15 are used to determine the index error, that is how
much the compass is not aligned to the fore-aft axis of the boat. Hence it
is necessary adjustment by rotating the compass to bring it into alignment.

Tan PS

Tan PS wrote:
Some clarifications.

"K. Smith" wrote in message
...


Not really, most ports have a compass swinging place set aside have a
look at the charts or ask. It usually has a set of posts you can tie to
& hold the boat on the various headings & "usually" they're sited so
there are at the very least a set of transits (2 or more landbased
objects that are on the chart & when in line mean your boat is pointing
to a known true heading as close to nth as reasonable given the
available transits)


You will have to keep the boat aligned and that's probably by keeping it on
the move along the line of sight. Tying it to posts that probably contain
steel reinforcements isn't a good idea. If you can keep it in a straight
line against a landmark, a GPS will work. Yes, you are correct about being
mindful of cross-track movements.


Tan,

I think we're at crossed purposes here, I think GPS is the single
biggest contributor to boat safety ever no exceptions. However it's
totally different method of navigation if indeed it can even still be
called navigation.

If the magnetic compass of any type is to be employed for navigations
then it needs to have a starting point & that's usually knowing which
way the bow of the boat is pointed & after that the navigator can make
decisions, mostly by calculation but eventually with ingredient "X",
which comes with experience & in small craft particularly knowing the
boat itself.

We've all come across the nuff nuff who's done all the nav courses etc
& will mindlessly hold a compass course straight up onto the bricks,
such is the belief that boats actually go where they're pointed over any
sort of distance.


A GPS has no clue which way the bow of the boat is pointing & this is
what you're trying to determine. All a gps can do is tell you your
history track across the seabed & clearly you need to be moving for it
to even be able to tell you that.. You might be moving sideways,
backwards or whatever the GPS will not know so can't tell you.


The suggestion provided assumes a knowledge of GPS usage and remains a valid
suggestion.

I explained my position so I guess you'll explain why you hold yours, I
can assure you there is no manner the gps knows which way the bow is
pointing.


I also note point 15 below??? DON'T ever do this, the compass must be
mounted so it's aligned with the boat's fore/aft centre line. It doesn't
need to be "on" or even near the centre line but must be completely
parallel with it.


The steps preceding 15 are used to determine the index error, that is how
much the compass is not aligned to the fore-aft axis of the boat. Hence it
is necessary adjustment by rotating the compass to bring it into alignment.

This is patently incorrect for any sort of proper compass Tan for the
reason already given. Again you need to know which way the bow is
pointing so you can apply various & varying adjustments, a skew wiff
mounted compass is an ornament.

K

Tan PS

"Jürgen Spelter" wrote in message
...
Hi,

I bought a dutch steal steel shipband I want to install a new compass.
Has anybody a tip how to adjust compass deviation?

regards

Juergen


You must take my advise with a grain of salt, as I don't hold a certificate
of proficiency in compass deviation:

http://www.tc.gc.ca/marinesafety/TP/...-chapter24.htm

With this in mind, I will point you to an authoritative source:

http://www.uscg.mil/hq/g-o/cgaux/Pub...w/chap14-c.pdf
and
http://www.woodfreeman.com/pdf/compasses-nautical.pdf

I seem to remember something on the topic in Bowditch.
http://www.marineplanner.com/bowditch/chapt-06.pdf

If you like to approach the procedure in an organized way:
http://www.tpub.com/content/administ...s/14221_73.htm

Naturally, there are books on the topic:
http://www.sheridanhouse.com/catalog...mpasscorr.html
and
http://www.maritimeusa.com/metconts/section11.html

What boats.com has to say on the topic:
http://www.boats.com/content/default...contentid=1139

The last time *I* had to do this, I just followed the card that came with my
compass - things seem to have worked out OK, so I can say that it is
possible to get success. It did not take much adjustment to get satisfactory
results. The adjustment were very touchy.

Best of luck,

Mark Browne