Useful Tips

Measuring Mast Height

Source: Joe Rocchio; SV Onward; Dec 09

I did surveying work as a summer job during college so that gave me confidence to do the measurement myself - but the process is easy.  Here is what I did.

I had a friend haul me up the mast (I've got an electric winch that makes that easy) with the reel end of a 50' tape.    I  then measured from the flat plate at the top of the mast to the deck at the base of the mast.  I also took measurements of how much my Windex, tricolor light, and anemometer projected above the flat plate.  I take a small FRS radio up the mast with me so I can dictate measurements back to the guy on the deck.   Take a short straight-edge and a short measuring tape up also to do the measurements at the top of the mast.

Back on the deck, I used a straight-edge and a level to go from the base of the mast to the edge of the deck.   I then measured from the bottom edge of the straight-edge to the waterline.   I did this on both port and starboard sides to account for any minor list and took the average.

So mast clearance is:  waterline to base of mast + base of mast to top plate of mast + height of instruments above mast top plate.

I took the measurements a couple of times for each part to be sure I didn't make a mistake. Onward had full fuel and water tanks at the time of the measurement.

Write these measurements down in notes you will be able to find as you'll refer to them many times!

By doing it yourself you'll have the confidence of knowing the numbers are good.

Updated: 3 Dec 2009