A full service instrument shop specializing in sales and service of marine compasses. Suppliers of genuine replacement parts for Danforth, Aquameter, Ritchie, Kelvin White, Dirigo and Star compasses
All Magnetic Compasses are vulnerable to magnetic interference, which will produce errors, called deviation. It is the Owner/Operator and/or Helmsman’s responsibility to make sure the compass is properly installed and compensated. Compensation is the act of correcting for deviation. Magnets (speakers, microphones etc.), ferrous metals (steel, iron, etc.) and current carrying devices are common causes of deviation.
Please read the Instructions completely before beginning installation.
SELECTING A LOCATION
The compass should be close enough to the helmsman and positioned below the helmsman's line of sight so it is easily read during normal operating conditions.
You will need a flat and level surface (when the boat is on a level keel). Many boats have a curved mounting surface and if this is the case, a fairing block should be utilized to bring the compass to a level position.
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.
TESTING YOUR LOCATION FOR DEVIATION
Use your compass to test a location.
1 Start by setting the compensation screws to neutral.
There are two brass rods near the bottom of the compass which rotate 360 degrees, the slotted ends may be all that is visible. To neutralize the comp-rods turn the rods so the the slots are in a horizontal position.
2 With the the boat heading North or South, begin your test by holding the compass away from any possible interference and observing the compass reading. Then move the compass into position carefully; keeping it pointed in the same direction. If the compass reading is different without a change in direction you are observing deviation. You will then need to do the same thing on East or West (You need to find a location that has less that 15 degrees of deviation on the 4 cardinal points if you intend to adjust your compass using only the built-in compensator rods.
After finding a location you should test for intermittent changes in the magnetic field. With the compass mounted temporarily in its intended position try moving the steering wheel, throttle controls or anything else that might cause deviation. It is also advised to turn electrical devices off and on. Please be advised that a changing magnetic field can not be corrected with compensation and you will need to find another location for your compass.
MOUNTING THE COMPASS
Great care must be taken to mount the compass so that it is aligned with the keel of the boat. An ALIGNMENT error is a constant error on all headings caused by the compass not being pointed in the same direction as the boat. One recommendation is to temporarily mount the compass using one fastener so if an alignment error is detected it is easily corrected. Masking tape can be used as a reference or to keep the compass steady during installation.
If you are mounting to a bulkhead that is not perpendicular to the centerline of the boat, a fairing block must be used.
Due to variations in bulkhead and deck materials, mounting screws are not usually supplied by the manufacturer. Use hardware that is suitable for your specific installation. SELECT MOUNTING HARDWARE THAT IS NON-MAGNETIC. Most quality stainless steel and solid brass fasteners can be used. If you are unsure test them with a magnet.
Most models have built-in lights which will require routing the wire or wires to your power source. To assure a clean installation you may want to wait and drill the routing holes after you are satisfied with the compass alignment.
A built-in correcting magnet system consists of two sets of magnets fixed to two adjusting rods with slotted ends. The slots should be horizontal before starting the adjusting procedure. A small non-magnetic screwdriver is provided for this purpose.