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JamesTXSD



Joined: 01 Mar 2005
Posts: 7444
City/Region: from island boy to desert dweller
State or Province: AZ
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: "Wild Blue" (sold 9/14)
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PostPosted: Tue Feb 02, 2010 1:58 pm    Post subject: Reply with quote

Jim & Dara wrote:
We recently had some of our soft keys as well as the Lat/Long read out fail on our new Raymarine C-80. I realized it is time address the compass I have taped to the dash.

After purchasing a Ritchie at West Marine I've been reluctant to permanently mount the compass because I don't understand how to verify that the compass is reading true or adjust it if required. My internet searches haven't been fruitful to date...

Does anybody have advice for a rookie?

I would like to mount it next to my chartplotter


Due to interference from metals or electronics, you may not be able to mount it right next to the chartplotter. We've found that the most accurate place in our boat is on the dash, above the opening to the v-berth... it is further away from the metal, electronics, and windshield wiper motors. Even so, the deviation varies from 4 to 9 degrees, depending on direction. The best way to determine deviation is to get the boat pointed in a known direction (such as tied to a dock). Check the compass with the known heading and make a note of the deviation. Rotate the boat and do the same. Then, determine the deviation for every 10º. You can get a deviation card to keep note of this, or you may find that the variation is such that you can "make a mental note" of how far off the compass is. Frankly, on a small boat, if I can get to +/- 5º for any particular heading (depending on wind and sea state), I figure I'm doing pretty good. Wink

Be sure when you put your compass in place, you take readings with all electronics off and then turn them on one-by-one to see what (if any) effect each of those has on the compass.

Hope that helps.

Best wishes,
Jim B
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Westfield 11



Joined: 13 Mar 2008
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City/Region: Woodland Hills
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PostPosted: Tue Feb 02, 2010 2:30 pm    Post subject: Reply with quote

Larry H wrote:
What's a compass?

It's the thing that can point the correct direction to get you out of the fog AFTER THE GPS QUITS due to power failure, broken antenna or wire, or the chip inside the GPS just dies. Teeth


If the GPS that's built into my boat fails, I'll just use one of my two handhelds. If they fail I guess it's back to the Nav program on my laptop with the USB antenna.

BTW, the units I have used will show the boat swinging at anchor and which way the bow is pointing. In other words it does not take much movement at all to give a directional input.

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Not a C-Dory owner but a lover of the forum and the spirit of adventure found here. This is the best small boat cruising resource I have found to date. The travelogues are very inspirational and a great reminder of why we go down to the sea in ships (or small boats).
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Jim & Dara



Joined: 25 Aug 2009
Posts: 43
City/Region: Santa Rosa
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C-Dory Year: 2008
C-Dory Model: 25 Cruiser
Vessel Name: PLAN B
Photos: Jim & Dara (TBD)
PostPosted: Tue Feb 02, 2010 3:40 pm    Post subject: Reply with quote

[/quote]

Due to interference from metals or electronics, you may not be able to mount it right next to the chartplotter. We've found that the most accurate place in our boat is on the dash, above the opening to the v-berth... it is further away from the metal, electronics, and windshield wiper motors. Even so, the deviation varies from 4 to 9 degrees, depending on direction. The best way to determine deviation is to get the boat pointed in a known direction (such as tied to a dock). Check the compass with the known heading and make a note of the deviation. Rotate the boat and do the same. Then, determine the deviation for every 10º. You can get a deviation card to keep note of this, or you may find that the variation is such that you can "make a mental note" of how far off the compass is. Frankly, on a small boat, if I can get to +/- 5º for any particular heading (depending on wind and sea state), I figure I'm doing pretty good. Wink

Be sure when you put your compass in place, you take readings with all electronics off and then turn them on one-by-one to see what (if any) effect each of those has on the compass.

Hope that helps.

Best wishes,
Jim B[/quote]

Jim,

Thanks for the tips I'm going to get this mounted as soon as the storms pass.

Are you able to read the compass easily with it mounted over the v-berth or do you rely on your crew to monitor compass headings?

Thanks again for the info,

Jim C
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breausaw



Joined: 18 Jan 2006
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PostPosted: Tue Feb 02, 2010 5:37 pm    Post subject: Reply with quote

If I had to rely on my compass and charts to navigate in unfamiliar waters I would be in a world of hurt. I assume who ever mounted my compass on the dash in front of the wheel had it collaborated, it’s right on when correlated with my GPS. Either way, I am not that concerned if it is off by a few degrees; it serves as a valuable tool when trying to steer a straight course..A course established with GPS technology. If it were mounted about the v-birth its value would be diminished unless your normal helm position is standing up. And if in fact the chart plotter does throw it out of whack some, so what? As long as the compass is accurate with the electronics turned off, this is how it would be used as back-up.

Back in the 80s I worked on fishing boats ranging in size from 32 to 66ft mostly around the Kodiak Island group. Loran was a pain so most navigation relied on knowledge of the area, charts, radar, sonar and the compass in front of you. Once you knew where you where going compass and radar got most of the attention, especially at night, and the chart was always close at hand.

For me having the compass anywhere but smack dab in front of the wheel would just be wrong.

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2007 22ft C-Dory Triple J 2007-2012
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JamesTXSD



Joined: 01 Mar 2005
Posts: 7444
City/Region: from island boy to desert dweller
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C-Dory Year: 2007
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Vessel Name: "Wild Blue" (sold 9/14)
Photos: Wild Blue
PostPosted: Tue Feb 02, 2010 7:40 pm    Post subject: Reply with quote

Using the compass when it's offset really isn't a big deal. On a couple of our sailboats that didn't have a binnacle, the compass was mounted on the cabin bulkhead, not on the centerline of the boat or of sight. Use one of the tic marks on the compass as your reference... glance at the compass from straight on, use the tic mark that lines up with the helm, and use that heading. Any change of course right or left will be reflected the same on the tic mark. It's just a matter of getting used to something in a different location - it still works the same.

As long as one has something they're comfortable with for a back up (another GPS, another 'nother GPS, a fixed compass, binoculars with a built-in compass, a Droid phone with a compass app, radar, a depth finder to follow contours, tossing out the anchor and waiting for better vis, follow the sun, follow the stars, a boat to follow, or an island to go ashore with your man Friday), you're good to go.

Best wishes,
Jim B.
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bjidzik



Joined: 21 May 2007
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PostPosted: Tue Feb 02, 2010 7:49 pm    Post subject: Reply with quote

I'm thinking about having an Azimuth 1000 fluxgate compass installed to get the radar overlay feature functional on a C90W display. I'd like to have both the magnetic compass & the Azimuth 1000 mounted on the dash somewhere but they need to be at least 3' apart per the manual(s).

Are there any issues installing or having both compasses on the dash?

For redundancy, I do carry a spare magnetic compass & a battery powered Garmin GPS in a ditch bag. I also carry a pair of 7x50 binoculars with internal compasses for obtaining bearings in case I have to revert to paper charts.

There are lots of areas in SE Alaska where magnetic compasses are extremely unreliable. I assume fluxgate compasses would also be adversely affected.

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journey on



Joined: 03 Mar 2005
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PostPosted: Tue Feb 02, 2010 8:18 pm    Post subject: Reply with quote

To beat everything to death, now that the '63 runs and doesn't leak, the GPS system does not provide anything but position and time.

The computer in the GPS receiver then differences successive positions and the corresponding time and calculates a velocity vector, showing the information as speed and bearing. So if you're at anchor, the noise in the GPS reading will produce speed and bearing readings, based on how you're swinging and the inherent noise in the GPS signal. You can bet on that bearing, but..

The compass (and/or flux gate ) provides a direction (and only direction) by measuring the Earth's magnetic field. So even if you're sitting still, you get a direction that's based on real information.

Though if you're in Alaska, or any other northern clime, where the magnetic field is coming down and entering the Earth (so to speak,) use judgment.

And I've used a depth sounder to tell me when I've reached shore in a fog, prior to Loran and GPS and Chartplotters and Radar and Steam Power Plants and Fire.

Boris
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thataway



Joined: 02 Nov 2003
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PostPosted: Tue Feb 02, 2010 9:12 pm    Post subject: Reply with quote

I have to disagree with Westfield. There are GPS compasses (Furuno SC50, $3600) but the standard GPS reciever will not show a direction, unless there movement of the vessel. An exception is the i phone 3 GS, but that is a hybrid fluxgate compass. Even walking around a room with a hand held GPS will not give a reliable compass bearing on the direction of walking--unless you go for a significant distance, and constant direction.

There are two excellent resources which every boater should own:
Chapmans "Piloting and Seamanship"--and "American Practical Navigator" by Bowditch. (on line at: http://www.irbs.com/bowditch/ ) Chapter 6 is compass compensation. There is a small boat edition of the latter. Both have excellent sections on compass installation and compensation.

As for mounting the compass--yes, you can mount it off center, and use one of the 45 degree lubber lines to use for a bearing. But you must have the primary lubber line absolutely straight fore and aft.

I prefer to mount the compass in front of my noise, so I don't have to take my eyes far off the water (same with the chart plotter etc).

Any compass needs to be swung--or compensated and a deviation table established.

I like to use a "sun compass"--see: http://www.lowpressure.com/combo.html
is a Dietz sun compass, identical to the one I own.
Other sun compasses and a brief explaination at: http://www.lowpressure.com/comcor.html I prefer to use the sun compass, rather than the method described in the next link.


Compensation of a compass is addressed at: http://www.ritchienavigation.com/service/compensation.html

Here is a post on Trawlers and Trawlering, by Capt. Will (deseased) in 1998. This a variation of the sun compass.

There are at least three things that make a magnetic compass in good repair not read true north.


1. Variation: This is the offset between the geographic North Pole and the
magnetic north pole (yes I know this is a little generalization, but it's
close enough for gov'ment work).


2. Deviation: This is the result of magnetic disturbances on the boat
that have an effect on the compass.


3. Misalignment: This really doesn't make the compass read incorrectly, but
it makes our interpretation of it incorrect. Misalignment means that the
lubber line is not parallel to the keel. When this happens, we think the
compass is showing us the course we are traveling, but it does not.


It is difficult to find information which is of value to yachtsmen on this
subject.. The compass manufacturers tell you to find ranges and adjust your
compass from that. Those instructions are useless. Professional maritime
texts tell you how to construct a deviation table. This procedure does not
correct the compass. What follows is a method to actually correct the
compass.


We can only correct for Items 2 and 3. Item 3 is the simple, but sometimes
difficult, task of making sure the lubber line is parallel to the keel.
This should be checked on every vessel. It is a very common and
unfortunate cause of magnetic compass problems. This epistle will not deal
with this subject, but don't overlook it.


All magnetic navigation compasses provide a means of making adjustments to
compensate for deviation, and vessels constructed of different materials
require more or less means of adjustment. Steel vessels are a special
problem and will not be discussed here. Vessels constructed of Fiberglass or
any other non-magnetic material present few problems so that they can almost
always be solved by making adjustments to the compass, or by relocating
equipment and/or wiring.


If after going through a complete compensation procedure, the compass is
still not compensated, the most likely problem is that the magnetic
deviation is caused by electrical equipment installed too close to the
compass. In that case, either the compass or the offending equipment must be
moved. The offending equipment could be electrical wiring. Just remember
that all of the 12 volt DC wiring close to the compass should be of twisted
pairs. That's another problem that we won't cover here.


******************************************
The Nature of the Beast


There's nothing wrong with your compass. It is aligning the "needle" with
the magnetic fields it finds itself in. It can be influenced by three
magnetic fields:


1. The magnetic fields of the earth.
2. The magnetic fields generated on the boat.
3. The magnetic fields of the adjustment mechanism in the compass. These
are really magnets set 90-degrees apart.


The whole compensation exercise it to remove the influence of 2 and 3 so
only the magnetic fields of the earth operate on the compass. If we do that,
the compass will display the correct magnetic directions.


It is important for you to know that no compass, to my knowledge, comes from
the factory with the adjustment magnets in any but random positions. That
means that your compass will almost certainly read incorrectly when you
first get it, even if you have no magnetic disturbance on the vessel. All
new compasses should be compensated.


******************************
What Before How


CaptnWil's second law is, "You must answer What questions before you can
entertain How questions."


Here's what we're going to do:
1. Take the compass off the vessel.
2. Put it in a magnetic free area
3. Remove all the effect of the adjustment magnets
4. Return the compass to the vessel
5. Using the adjustment magnets, counteract the magnetic disturbances
produced by the vessel, which act on the compass.


Then your magnetic compass will tell you the truth about magnetic
directions.


****************************
The General How


The compass itself will be used to make corrections to itself using the
following fact.


If you turn the compass 180-degrees physically, it should show
that 180-degrees change on the card.


If it does not, some magnetic influence is affecting the compass besides the
earth's magnetic field. Our job is to make the compass reflect the
180-degree physical turn accurately by canceling or removing the other
magnetic influences on the compass. We will concentrate on canceling those
influences.


The very first time we do this, we must first perform this exercise off the
boat and then on the boat. After the first time, you'll just need to do it
on the boat. The procedure on and off the boat will be different, but the
result will be the same. It is important for you to fully understand that in
both cases, we are going to make the compass card reflect a measured
physical direction change of 180-degrees. That's all there is to it. Any
procedure which does that can be used to compensate a compass. In our case,
our only problem is how to measure the physical 180-degree direction change
we will force upon the compass.


****************************
Off The Boat
We take the compass off the boat to remove all of the existing adjusting
forces so that our job on the boat will be easier. We will have much more
control, and the exercise will be much easier, on land than on the sea.


You will need:
1. Some means to make the compass sit flat on a surface. The shape of the
compass may well allow this, but if not, anything non-magnetic that will
hold the compass will be fine.


2. Some flat object with square sides to hold the compass. A large book, a
piece of wood cut square, a small cardboard box, etc.


3. Another flat object to place Item 2 on.


4. The adjustment key that came with your compass. What, you don't have it?
You must find a non-magnetic blade of some kind to turn the adjustment
screws. Some electronic stores have plastic screwdrivers. But it must be
non-magnetic. I've made such a tool from a penny with a file. If you do
this, be sure to wash the finished tool to take off any steel residue.


5. A straightedge: A yardstick or non magnetic carpenter's level will do.


Item 2 should be smaller than Item 3. We're going to rotate Item 2 on Item
3, guided by the straightedge. A book would serve well for Item 2. A wine
case would serve well for Item 3. Just don't drink the wine till we're
finished compensating the compass.


Work on any level surface away from any magnetic influences. Indoors is
generally bad because of magnetic influences. Remove your watches, knives,
belt buckles, or any other material that may be magnetic.


Place Item 3 on the level surface. Then place Item 2 on Item 3. Then place
the compass in Item 1 on item 2. You now have a compass on a "book" on a
"box." I'll use the book and box identifiers for what follows.


These are the steps:
A. rotate Item 2 (the book which holds the compass) until the lubber line
of the compass is either on East or West.


B. Place the straightedge along side of Item 2 (the book). Then, being
careful not to disturb the compass on Item 1, and holding the straightedge
firmly, turn Item 2 (the book) 180-degrees. The straightedge lets you do
this perfectly. Presume you started with the lubber line reading 90-degrees.
It should now read 270
degrees (90 + 180 = 270). If it does not, you have a compass error.


C. Correcting the compass error will always be done in the same way. Using
the adjustment key, remove ONE-HALF of the error. If your compass reads 280
degrees, you would adjust it while keeping it firmly in place so that it
reads 275-degrees. When you are making adjustments for the E/W direction,
adjust the screw adjacent to the N/S lubber line. The adjustment magnet is
always 90-degrees from what you want to adjust for.


D. Repeat steps A thru C until there is no error. Notice. you are changing
where the compass says East is every time you make a correction. The
wonderful compass is telling you about its errors itself. You will be able
to adjust it until you get no error if there are no magnetic disturbances
and you do the job properly.


F. Now go through the steps A thru D again, except use North (0-degrees)
and South (180-degres) instead of East and West.


G. When all the error is gone, make a final check. You'll find that you
have a compass that tells you the truth.


Make sure you are friendly with what we just did. It will help you on the
boat if you are completely friendly with this procedure. If you are not
friendly with this, do it again until you are.


*******************************
On The Boat


We now have a compass that reads the correct magnetic directions when not
under the influence of magnetic disturbances. When we mount it on the boat,
we must check it to see if we have placed it in any magnetic disturbances.
If we have, we'll make adjustments to the adjusting magnets and cancel those
disturbances.


**************************


What We Will Do


We'll use the compass itself again to check itself. Remember, all we must
do is prove that the compass card accurately reflects the 180-degree
physical turn we make to the compass. Instead of turning the "book" on the
"box" 180-degrees to turn the compass, we will turn the boat 180-degrees,
and that will turn the compass 180-degrees. Our main problem is what to use
for the straightedge we used with the "book" and "box." We'll use the SUN
and the shadow it casts as our straightedge. You can buy the tools
necessary for this work from navigation supply places, but a device you make
yourself is easier to use and much easier to store.


***********
The Tool


We're going to end up with a piece of wood about 3-inches square and about
1-inch thick - the exact dimensions are unimportant. On one side, you
scribe a line from one edge, through the center to the other edge. This
piece of wood will have a pin attached to it at the mid-point of the line
about 3-inches high and perpendicular to the piece of wood. The pin is
called a SHADOW PIN, and the piece of wood is called the SHADOW BLOCK. When
the shadow block is level, we can use the shadow cast by the sun shining on
the shadow pin as our straightedge. The only requirements are that the
shadow block is level and the shadow pin is perpendicular to the shadow
block, and that the shadow block remains motionless during our work.


To meet the three requirements stated above:


1. Get a square or rectangular Tupperware container to put the shadow block
in. This will be called the SHADOW DISH. The shadow block should fit
easily into the shadow dish. When we use this device, we will float the
shadow block in the shadow dish. This will keep it level. The shape of the
dish will keep the shadow block stable. If the shadow block hangs up on the
edge of the shadow dish while it floats, the shadow block is too large and
must be trimmed. If it lets the shadow block move around a lot it is too
small. It needs to be just right.


2. The shadow pin is easily made from a piece of brazing rod. That rod is
non-magnetic and serves well. Just drill a hole into the shadow block using
a drill press to accept the pin. The use of the drill press will keep the
shadow pin perpendicular to the shadow block.


Got the picture? We just have a block of wood floating in a container with
a pin in the center with a line scribed on the block. This tool is easy to
make and will serve you forever. I made mine in 1965.


*************************
The On Boat Procedure


These instructions are for situations where one person can get to both the
tool and compass, and the tool is exposed to the sun for 360-degrees.


We're going to do exactly the same thing on the boat as we did on shore.
The boat needs to be at no more than idle speed. The seas need to be calm.
The sun needs to be 30-degrees or more above the horizon. Insert the shadow
pin into the shadow block, and place the shadow dish with the floating
shadow block where you can get to it easily.


A. Steady the boat up on either 90 or 270 degrees. We'll assume 90. Rotate
the SHADOW DISH until the shadow from the pin falls on the scribed line. It
is important that the vessel compass reads exactly 90 and that the shadow is
exactly on the scribed line.


B. You have five minutes for this next operation - read carefully. Look at
the shadow block - DO NOT look at the vessel compass (I wish I could
underline that last sentence because it is so important). Turn the boat
slowly to cause the shadow to go around the shadow block. Steady the boat
up so the shadow from the shadow pin stays on the scribed line 180-degrees
from where it started. When it does, you have turned the boat exactly
180-degrees.


C. Now, and only now, look at the vessel compass. It should read 270. If
it does not, keep the vessel steady so the shadow stays on the scribed mark.
The shadow dish must not move until this step is finished. Observe the
compass reading and change the compass heading half of the error by turning
the adjustment screw. For example, if the compass reads 290-degrees, adjust
it to read 280-degrees. Extra Emphasis! Make the adjustment only when the
shadow is exactly on the scribed line. When you are finished, the compass
must read 280-degrees while the shadow is on the line.


D. Repeat A thru C until you have no error, or you can't make the error any
smaller.


E. Do exactly the same thing for the North/South headings.


F. Recheck it one final time. Most likely you will find that you cannot
read any error.


should check it at least once a season, after bad electrical storms, and
anytime you add or move magnetic stuff around.


You can carry this procedure further by checking the compass at every
45-degree interval, but making corrections in directions which are not E/W
or N/S is very difficult because both adjustment screws would need to be
turned to make any adjustment. That's beyond what most of us can do
successfully, but it does no harm to check as many directions as desired.


************************


Problems


Often the adjustment screws on compasses are hard to get to on yachts, and
often the shadow dish must be located away from the compass station. In
those cases, you will need some help. At most, you will need one person to
steer and read the compass, one person to make the compass adjustment
itself, and one person to tend the shadow dish. The only problems these
situations create is one of communication. If you work that part out,
you'll have no problems with making the adjustments.


Sometimes you just can't get all the error out. In fiberglass boats, the
most common problems are wiring and electric motors. In those situations,
you must either move the compass or the offending stuff. I have always
managed to fully compensate any compass on a fiberglass boat. I have even
compensated the compass on my dinghy.


One little known hazard is to have two magnetic compasses too close
together. You can never get them compensated since they present rotating
magnetic fields that change every time the direction of the boat changes.
Be especially careful of mounting an electronic flux-gate compass near a
magnetic compass. Neither will work well at any time.

_________________
Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
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Sea Angel



Joined: 29 Dec 2003
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PostPosted: Thu Feb 11, 2010 4:22 pm    Post subject: Reply with quote

THATAWAY;

Thumbs Up Bob, great instruction on the 'alignment, care and feeding' of our
Ol' reliable STBY Compass. How well I remember having to take our
squadron's S2F ASW aircrafts out on the Compass Rose to swing the STBY
compass.

Art

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versatileman



Joined: 20 Oct 2009
Posts: 2

PostPosted: Fri Apr 02, 2010 10:15 am    Post subject: Reply with quote

What is so bad about living in van down by the river? Smile
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Levitation



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PostPosted: Fri Apr 02, 2010 4:35 pm    Post subject: Reply with quote

I have a flux gate compass on Levitation... The sensor is mounted at the forepeake of the Vee Berth... Now, the chain bundle is right in front of it and you would think that it would befuddle the sensor, but the flux gate agrees with the GPS (when corrected for declination) and with the whiskey compass in front of the wheel, most of the time..
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marco422



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PostPosted: Fri Apr 02, 2010 6:28 pm    Post subject: Reply with quote

I've had my GPS "fail" twice in awkward situations. One was a Garmin GPSMAP 178s that suddenly went blank on me. I think it was a momentary electric failure rather than a GPS circuitry failure, as it restarted OK.

The second time I was in the SW entrance to Active Pass with a Garmin 545s and I decided to sort of explore the reefs a little bit there (!!). Suddenly my position started jumping all over the chart and I stopped the boat and restarted the GPS. It was fine after it restarted. Fortunately, there was little tide running at the time.

I have had my position start jumping around before and have had the same happen with my handheld. I have assumed this was a "feature" of GPS. Do others experience this as well?

As to compasses, I use a small Ritchie Explorer mounted in front of the helm and have it swung to about 2-3 degrees in all directions. I just can't see the point in sweating over getting it more accurate than that. My ability to keep a course is not that sophisticated and the exaggerated movement of a small 16-footer precludes it. I check it every so often against the GPS, but GPS is mainly what I use. I usually have a medium scale kayaking chart open to get an overview of plans & progress. I usually use Kimantas' chart atlases.
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C-Hawk



Joined: 02 Nov 2003
Posts: 2145
City/Region: Carpinteria / Channel Islands
State or Province: CA
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: C-Hawk
Photos: C-Hawk
PostPosted: Fri Apr 02, 2010 8:39 pm    Post subject: Reply with quote

versatileman wrote:
What is so bad about living in van down by the river? Smile


What C-Dory do you have? or do you live in a van down by the river?

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Roger
2002- CD22- "Fishtales" returned to factory 2008
2008- CD22- "C-Hawk" Sold
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A Brat I am, At sea I be
God is Great, Beer is Good.... and People are Crazy
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Barry Rietz



Joined: 21 Jun 2006
Posts: 409
City/Region: Sierra Vista
State or Province: AZ
PostPosted: Sat Apr 03, 2010 4:31 am    Post subject: Compasses! Reply with quote

A "magnetic compass" should always be the primary navigation device aboard any vessel doing coastal or offshore work! And this is one piece of gear where you should never compromise quality! Pick one with the largest diameter "rose" that will fit your vessel's console. Keep it as far from any magnetic influence as possible. Then have the compass "swung" and "compensated" by a professional. They will provide a "compass card" that will allow for compensation of any "deviation" that might be induced by on board influences. If you are cruising long distances out of sight of land, and do not have an "auto-pilot", steer by your compass and it will never let you down!
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Plan C



Joined: 16 Apr 2004
Posts: 243
City/Region: Port Townsend
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Plan C
PostPosted: Sun Apr 04, 2010 1:36 am    Post subject: Reply with quote

I had a Ritchie compass on my boat for 5 years and don't recall using it once. When I replaced the GPS, I decided the compass was taking up too much real estate, and yanked it. I do agree it is important to carry a compass, so I have replaced it with a Suunto sighting compass, which though smaller and unlighted, has more utility, plus it takes up no space. If there is any question of interference, I can carry it somewhere else, like the cockpit.

I still haven't used the Suunto on the boat, but at least it takes up less space.

Dave
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