In have noticed small cracks (2 to 3 cm) on both the port and starboard side in the manufacturer's weld towards the top of the mast where the mast taper is attached. Has anyone else had this problem?
Crack in mast of Beneteau First 40.7
- Thread starter Ian Lewis
- Start date
Like the First 36.7, the 40.7 was originally spec'ed and designed for fractional kites. Due in part to the ease on switching to masthead (the halyards actually are masthead that run down to a restrainer at the hounds) many owners (in particular in light are venues) switched to run masthead. There is a ratings hit of course but in light airs it can pay. There has been many debates on the soundness of the thinking of doing so, and how the unsupported part of the mast might handle the load in particular when reaching. FYI.
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I don't know about the stresses resulting from flying fractional vs masthead kites, I defer to Jack's expertise there... but I do know welds and why they crack. The welds themselves become thicker than the surrounding metal, and because of the heat it becomes more brittle. The additional stress, from what I gather Jack is pointing out, is causing stress that trying to flex the mast from the taper upward, and that stress is being focused in the thicker weld bead that is far less flexible than the surrounding material. Aluminum needs to be annealed, applying low temperature heat realigns the mono-crystaline structure of the molecules. Thats why you never quench an aluminum weld, rapid cooling makes it brittle. To my knowledge, because I'm not an aircraft welder, structural welds are kept hot with low temp like an acetylene torch without the oxy, or even propane, to keep it warm and cool slowly... this maintains the annealing in the welded aluminum because aircraft frames flex a bunch. Sorry for the long version, but I can't say it was a faulty weld... probably shouldn't have run a masthead kite, the tapered mast wasn't intended for that. You'll need to de-rig and un-step the mast, have it professionally welded.