Boat Rat: Zero Your Sailboat Compass for Sailing Safety

Captain John of www.skipperMake sure your steering compass keeps you in safe water and out of harm's way. Zero your compass once each sailing season for peace-of-mind underway.tips.com shares the importance of zeroing out your compass and how to do it.

Can you trust that sailboat compass mounted on your cockpit bulkhead or inside your binnacle stand? Perform this vital task once each sailing season for sailing safety. Follow these seven simple steps for safer sailing navigation anywhere in the world!

During shipping from the manufacturer, vibration or rough handling can lead to internal compass errors. Even a small compass error could cause you to miss a landfall or lose your way in pea-soup fog. This table links compass error and miles to sail to end up one mile off of your course…

Miles to Sail to be One Mile Off Course
Compass Error Miles to Sail
1 degree 57 miles
2 degrees 28 miles
3 degrees 19 miles
4 degrees 14 miles
5 degrees 11 mile

Zero the compass to remove this error before you install a new compass aboard. Check an installed compass if you are unsure whether it was zeroed before installation.

Remove the compass from the bulkhead brackets or binnacle housing. Find a table or floor ashore well away from any magnetic influences.

Tools You Will Need

  • Flat head jewelers screwdriver (non-magnetic)
  • Hardback book
  • 12″ square piece of plywood
  • Duct Tape
    Seven Steps to Zero a Steering Compass

    1. Locate the compensating screws on the side and front (or back) of the instrument case. You might need to remove small covers to access the screws.

    2. Draw a straight line down the center of the board, parallel to one side. Mount the compass so that the lubbers line lies over the pencil line. Screw or duct tape the compass in place.

    3. Turn the board until the compass points to 000 degrees. Place the edge of the hardback book along the right or left side of your board.

    4. Hold the book in place. Slide the board away and rotate it so that the compass now faces in the opposite direction. Slide it back up against your hardback book.

    5. Read the compass heading. If it reads 180 degrees, it has no error on north-south headings (go to step 7). If it reads something different, remove one-half of the error. Turn the screw on the side of the compass up or down until it reads half the error.

    For example, if it reads 174 degrees, turn the screw until it reads 177 degrees (halfway between 174 degrees and 180 degrees).

    6. Reset the board and book so that the compass now points to 180 degrees. Hold the book and rotate the board so that the compass faces the opposite direction. Butt it up against your hardback book and read the compass.

    If it reads 000 degrees, you have zeroed out all error on north-south headings. If it reads something different, remove one-half of that error. Turn the compensating screw up or down to do this.

    For example, if it reads 002 degrees, turn the screw until it reads 001 degrees (halfway between 002 degrees and 000 degrees).

    7. Repeat steps 3 – 6 until the compass reads exactly 000 degrees and 180 degrees. Next, follow the same exact procedure for east-west headings. Start with board and book aligned to 090 degrees. Make sure you use the other compensating screw to remove error on east-west headings.

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    Use these seven easy steps to remove any hidden errors from your sailboat compass. This will give you peace-of-mind that your #1 sailing navigation instrument will lead you home every time!

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