Montgomery 15 Gaff Cutter Conversion

by · May 26, 2010

by Doug Kelch

I have always admired traditional rigs with a special place in my heart for the gaff cutter rig. I cam close to buying one on several occasions, but they were always wooden boats that were older and larger than I wanted. In reading a number of books on traditional rigs that implied a traditional rig on a modern hull could be very effective, and reading about the amazing accomplishments of Charles Stock (70,000 nm in a 16-foot gaff cutter), I decided to convert my Montgomery 15 to a gaff cutter.

I hoped the conversion would result in a more versatile sail configuration without giving up too much of the nice performance of the Montgomery 15 Bermuda sloop rig. Charles Stock’s analysis made me nervous as he predicted as much as a 10 degree loss in pointing ability. If this turned out to be the case the conversion would be a nice exercise, and would satisfy my curiosity, but would not be retained for any length of time.

I needed a new set up sails so I bit the bullet and did the design work using a combination of technical information, advice from knowledgeable people ( John Harris @ Chesapeake Light Craft, Jerry Montgomery, and Douglas Fowler Sailmaker), rules of thumb, and cosmetics. I patterned the overall sail plan after Charles Stock’s boat and went with a low to moderate peaked gaff with two nearly evenly divided foresails.

The results?

Outstanding! I don’t believe I lost more than 1 – 3 degrees in pointing ability but, with the increased power in the lower sail area, the velocity made good to weather is at least as good as the Bermuda sloop rig. The boat gets up to hull speed in a lower wind range than before and yet does not require a reef until 3 – 5 kts more wind than the original sail configuration.

At the Lake Havasu poker run there were very few boats who showed the ability to move in the light air as easily as the gaff cutter.

With the lower center of effort the gusts do not affect the boat as quickly as before and sailing range of wind speeds seems much broader. The first day of sea trials it was gusting near 30 mph and handled well without a reef. The boat heels less quickly in the gusts which makes the gusts seem less powerful.

Another M15 sailor invited me out to play in a wind forecast of 28 mph gusting to 40 so off we went. I was a bit later into the water than the other boat so we did not have any time to do a side by side comparison. However with just the small staysail and a double reefed main I was able to punch through the waves on Lake Pleasant, AZ ( 2 – 4 ft) and keep the boat speed between 4 and 4.5 kts. The local weather recording systems confirmed that the steady winds were 28 mph but only recorded gusts to 33 mph. It was so much fun that I sailed the 10 miles to the end of the lake and spent the night on board.

I attribute much of the performance to an excellent set of sails by Douglas Fowler.

Concerns? No concerns about sailing ability or cruising, but is does take longer to rig and get into the water. It has a removable bowsprit that cannot be mounted while on the trailer. The lower, spread out sail plan increases the turning resistance and she is slower through a tack.
I am very very happy with the rig and look forward to the opportunity to cruise or race with other M15 s to complete the comparison.

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Discussion2 Comments

  1. charles morris says:

    I live in Jacksonville FL. & have been thinking of changing my rig to a balanced
    Would you have any input to such a conversion.
    For starters I need to lighten the mast raising issue as I’m 69 & look for an easy launch & retrieval.
    I figure to keep cost down I will make a poly sail intially & figure out the sticks material after I arrive at a measurement.
    Did you have any issues with center of effort or balance with you conversion & did you work from the orginal mast step location as I don’t want to reposition the mast?

  2. John Shepard says:

    I see you installed a Bowsprit, “It has a removable bowsprit that cannot be mounted while on the trailer.” in your conversion. I am working on adding one. How did you fasten your sprit to the bow? I have a 4 ft aluminium pole, and a couple of plugs for the end which will permit my ‘tack’ line to pass through the bowsprit. I am challenged with a method to simply attach and remove the pole without loosing strength in the process. Suggestions about just screwing it down are unworkable, as they do not solve the removable/reusable function.

    Thanks for your thoughts.

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