mid-boom sheeting break on Beneteau

[somedaypam]

Does anyone know if there is a history of (or higher than "normal" incidence of) booms breaking when rigged with mid-boom sheeting? My boom broke recently and I'm needing to deal with the insurance company and want to educate myself on the dynamics of a break of this type. On my Beneteau Oceanis 390 the main sheet bridle is located in the middle of the boom. There are three blocks- 1 is connected to a bale that's attached to the boom (this is where the boom break occurred) and the other blocks are on bales that slide along a track (groove in extrusion) on the underside of the boom. I was tacking in 15kt winds and going from a beam to a beam, didn't pulled my sheet in and when the boom came over it just kept going and split in two pieces just at the fixed bale. Not sure if its significant or not but I'd just changed to a new loose footed mailsail. I also had the vang on but not too tight and I'd tightened the toppinglift about 3 inches earlier in the day in order to take up excess stretch from the new line. The insurance company wants to say that its a result of "corrosion" in the aluminum under the fixed bale but there's certainly more to this story. I've been sailing for 28 years and never seen anything like this. Any info, insights or similar stories would be helpful. Thanks

[sailingfool]

Mid boom sheeting does put a big strain on the boom. I've broken two booms with this configuration but on smaller boats. The first was a Rhodes19 with the sheet connected mid-boom via a single bale. This boom broke at the bale beating in 20+ knots, with three adults hiking - just too much load. This is a common Rhodes 19 failure. The replacement boom with two mainsheet blocks attached via eye straps about 18" apart has serviced fine for 6 years. A second time, getting underway on a heavy weather day in a 21' daysailer with mid-boom sheeting, again a single block, as we trimmed the main to closehauled the boom immediately broke - and I realized that we hadn't eased the topping lift after setting in the reef. If the topping lift is tight, trimming the mainsheet hard will break any boom.

I would think having a bale through the center of the boom was not good, and a tightened topping lift also a factor, especially if you gybed the boat so the main had some momentum when the sheet caught it...it's hard to imagine where the force came from in a tack and 15 knots of wind. If this is a model used by some of the yacht charter services and its a common problem with that boom, they would know so. You might try them.