Airglide compass, painted, what about adjustments?

[sdowney717]

I took this apart and repainted it.
Compared to my smartphone compass app, I made some compensation adjustments.
Not sure how accurate either compass really is.
I have 3 compasses here and they all read differently.

If the slots are vertical, I read no compensation?

 

[Gdavid]

I'm not sure of your question but don't bother trying to calibrate it till it is back in place in the boat with all gear in its normal position.

 

[Larry M]

I'm not sure of your question but don't bother trying to calibrate it till it is back in place in the boat with all gear in its normal position.

We've had our primary compasses professional spun/calibrated on our last boat, in place, with all the electronics on, while underway. In the end, we were issued a card for the compass listing the minor deviations at various points. How important is it today to have an accurate compass when we use mostly electronic navigation?

 

[sdowney717]

We've had our primary compasses professional spun/calibrated on our last boat, in place, with all the electronics on, while underway. In the end, we were issued a card for the compass listing the minor deviations at various points. How important is it today to have an accurate compass when we use mostly electronic navigation?

Of course it is more of a fancy looking toy today compared to my gps chart mapping software.

When boating, I rely on the GPS and look at the compass just to see how far off it is.

 

[ulysses]

As stated earlier, your compass should be mounted on the boat prior to making any major adjustments. Two items effect the accuracy of any compass. 1. Where you are on the surface of the world. 2. The magnetic influences surrounding your individual compass at its individual location on your boat. Variation and Deviation are the two factors. It is not difficult to correct for either or both items. Any decent navigation book and/or Chapman's will explain how, including making your individual compass card.

 

[RT Firefly]

Greetings,
I use the compass a fair bit. Ours is directly in front of the wheel and takes but a quick glance to read. GPS is offset and takes more of a direct look to actually read. IF I ever get around to it, we'll have both compasses swung (upper and lower).

 

[sdowney717]

Greetings,
I use the compass a fair bit. Ours is directly in front of the wheel and takes but a quick glance to read. GPS is offset and takes more of a direct look to actually read. IF I ever get around to it, we'll have both compasses swung (upper and lower).

Same here regarding compass placement, it is where it was from 1970 in front of the wheel.
I have the monitor off to the left on the chart table. It is no problem looking to the screen to find the heading. I use a desktop PC running Linux Mint with OpenCPN for the charts and a usb Delorme LT-20 GPS. Picks up the signal through the window glass easily.

My PC is in a side cabinet with 15 foot cords for HDMI, USB to a hub on the chart table.
I have a remote on-off switch with little leds light for the control of the PC. I found an unused space behind a panel. So I cut an opening and created a hinged door and also made my own motherboard mounting cutup from an old desktop case so it fits sideways. A standard case is too tall to fit by about an inch. Doing this let me have a PC for the boat built using cheap standard parts.

I also if I want, HDMI carries audio, so I have audio runs to the stereo. When set stereo to aux, I can play videos and hear the sound from radio speakers. The device that breaks the sound out from the HDMI cable to a stereo audio standard port was $5 on ebay.

 

[Larry M]

sd: By the way, nice job on the paint job. The compass looks great!

 

[sdowney717]

sd: By the way, nice job on the paint job. The compass looks great!

Thanks, pretty good for a compass from mid 70's.

I found ceramic stove top polish-cleaner will remove scratches and marks in the dome of these things.
Simply rubbing on with your fingers.

 

[Gdavid]

I would guess that very few recreational boaters establish, use and maintain a deviation card. Personally, I do a crude check just to insure that I don't have anything 5 degrees or greater on any course, as long as it is below that 5 I ignore it because I'm unlikely to maintain a course that accurate steering by compass alone. Variation around me is significant and I account for it. It is interesting to me that most texts assume there is no deviation for a hand bearing compass which is a bit silly as it is subject to magnetic disturbances around the boat as well.

 

[Paul M]

It is easy to swing a compass in this GPS era. On a calm day steer due North using your GPS (or chart plotter) for heading. Of course, using an autopilot helps holding course. Then once established on the North heading, look at the compass and note the difference. Adjust out the difference using the lateral (side) adjusting screw for the compensating magnet on the compass. Once you have the North aligned turn 180 degrees due South. Note the difference between the compass and GPS and adjust out 1/2 of the difference. Turn back to North and now note the difference. It should be exactly the same degrees out as the South reading. You may want to adjust by 1/2 again, but rarely is it needed. The final difference should be noted for your compensation card. East and West alignment is done exactly the same except you use the fore/aft (sometimes referred to as the vertical Axis) adjusting screw. Once the East - West compensation is completed then you can make your compensation card, if you like by noting the final difference between headings. In this day and age compensation cards are not used very much and personally I wouldn't bother. Swinging a compass is a fun exercise if you've never done it before and it is easy and painless.

 

[sdowney717]

Do you set the compensators to straight up and down slots first?

Sounds interesting, this summer will try that with compass on boat.
I will try that too with compass here at home, see how it goes. Do this outside in the yard.
I can use the smartphone compass. I went into settings, it said with Phone GPS on, results are highly accurate on that android app.

It is an Airguide, not Airglide compass, I got the name wrong.

 

[psneeld]

Pretty sure when using gps to calibrate a compass...the easiest is to just set the gps to give magnetic headings, bearings....not true.

From Ritchie compass website


Installation, Compensation,
For all
RITCHIE®
Compass Models
Made in U.S.A.


Method 2. (Requires the use of GPS)
In this method you will be using a GPS as your reference.
1. Your GPS must be set to provide you with Magnetic, not True headings. Check your Manual.
2. GPS provide headings based on COG (course over ground). Compasses provide heading based on the direction
the boat is actually pointed. Because of Tides, Currents and Winds, the boat may not always point in the same
direction as COG. Pick a time and location that will minimize these effects.
3. Because the GPS calculate COG based on current and past positions you will see greater heading accuracy
while traveling at higher speeds. We recommend at least 10 knots.

 

[Paul M]

A compass swing to be done properly needs to be installed on the boat in its normal position so that anything that has influence on it is accounted for in the adjustment. However for fun and learning sake, your house will be fine.

I do not make any movement of the adjusting screws until I'm ready to actually compensate the compass. It takes just a very small - almost tiny - movement to adjust for as few as 10 degrees.

 

[psneeld]

Found this interesting from the same site...

Select a location that has no more that 20 degrees deviation on any of the four cardinal points (N S E and W). Most
compasses have a built in compensation system that will correct for fixed deviation up to 20 degrees. It is important
to realize that proper compensation is not possible when a compass is subjected to a magnetic field that is variable.
Some shipboard devices can cause varying magnetic fields. Devices such as windshield wipers, high current carrying
wire and even some steering wheels must be considered when selecting a location for your compass.




Note the auto compensation found in most compasses comment.....

 

[sdowney717]

I was reading with an android phone compass, turn off data and wifi and gps will make the compass a magnetic only one using only the magnetic sensor, it will not have internet location data to compensate for deviation.
And to calibrate , wave phone in a figure 8 pattern.

Turning the compensator screws a little can make the wheel move a lot sometimes.

And it is 40* outside today, so not going to do it today.

 

[Heron]

Use Non-magnetic tools for adjustment!

https://www.amazon.com/s/ref=nb_sb_ss_rsis_1_4?url=search-alias%3Daps&field-keywords=plastic+screwdriver&sprefix=plas%2Caps%2C154

 

[sdowney717]

yes, a small steel screwdriver affects it. I think you can move it a little then take it away from the compass.

 

[RT Firefly]

Greetings,
For a non magnetic adjustment screwdriver, simply take a piece of solid copper house wire and flatten one end and bend the other end