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GMT's Furling BoomGMT introduces carbon boom with no mandrel through the mast. From "Shoreline" in our January 2009 issue
Article Supplied by Cruising World
By Andrew Burton
Andrew Burton
The system operates via a hydraulic motor situated inside the boom's mandrel.
I've always liked the convenience of a roller-furling main, and I've always liked the power and balance that a full-battened main gives a boat. Unfortunately, the two often are mutually exclusive.

In-boom furling systems, in which the main is raised like a window shade going up, are changing that. I recently went for a sail aboard Sonny, a 70-foot Bristol that uses GMT's new carbon-fiber furling boom. GMT takes in-boom furling a step further than the norm with a silent hydraulic furling motor that's in the boom itself, eliminating the need for a mandrel through the mast and the complications of a universal joint at the gooseneck and mounting the furling motor in the mast.

A criticism of many in-boom furlers has been the need to have the boat pointing absolutely straight into the breeze so the sail furls properly or hoists without damage. This orientation isn't necessary with the GMT boom. With the GMT, we successfully hoisted and furled the main with the wind on the beam; whether the sail was full or luffing made no difference in the 12-knot breeze. As with other in-boom furlers, the boom vang does have to be set to keep the boom at the correct angle; it takes practice to figure out, but it's not rocket science.

Because of the cost of the new boom, GMT president David Schwartz thinks it unlikely that he'll sell many of them to owners of boats much less than 50 feet, but he avers that his boom becomes a pretty good deal on bigger boats, when compared with similar systems. The in-boom furling setup on Sonny cost about $120,000.
GMT's new carbon-fiber furling boom (www.gmtcomposites.com) is definitely a step forward in this technology, and I look forward to hearing from Sonny's captain about how well the boom performed at sea.
Andrew Burton
 

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in boom furling

I had a similar system on a 157 foot ketch. The Main mast was 198 foot off the water so it was a big sail. The rig was built in New Zealand and I had remotes for hoisting and furling both the main and mizzen. It was a bit more than 120K. I had two complaints with it, first the boom had to be exactly perpendicular to the mast otherwise the sail would wind up away or too close to the gooseneck. I had a little light on the boom that would glow green when it was correct but it was not accurate and we had problems with it. Also if it did not furl tight it would move forward or aft when stowed causing it not to feed correctly. The second problem was at the feeder, it would sometimes fold the luff tape and bind, I normally had to have a man at the feeder making sure it fed correctly.
In theory it was good. But in practice it caused a lot of work, and I at times wonder if it would not have been simpler to just use lazy jacks.
I used to sail an 80 foot cutter that I took around the world often with just two or three of us aboard. I had a full batten main with Harken cars and lazy jacks that were attached to the boom and were led forward when hoisting and sailing. I had hardly a problem with them. I tried a 'dutchman' system, but it gave me problems.
Sometimes simple is the best.

Michael
 

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I have a boom furling main on a peterson. All you said is true with the problems and benefits. If short handed ( two of us) and we always are; we reduce sail early and I can control the halyard and the boom furler at the same time - we do round up a bit to take the pressure off. I find I have to release the boom vang in order to raise or lower the main.

Does anyone else have this drama????
 
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