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Date Posted: - Tuesday - 10/13/09 - 8:39pm
Author: Randall, Murre, M31
Subject: Welcome to the Club!
In reply to: manana 's message, "mainmast on m31" on - Tuesday - 10/13/09 - 6:01pm

Ah, my friend, welcome to the M31 mast bend dilemma club. Two dilemmas you will face immediately are the “How-the-heck-did-this-happen?” dilemma and the “How-do-I-fix-it?” dilemma. Neither, it seems, comes with a readily accessible resolution, which I guess is why we call them dilemmas.

As to the first, there are several lines of speculation. One could easily blame it on a previous rigger who felt that mast bend was modern and might afford the M31 a few much needed seconds at the Friday beer can races. But that so many of us from different ports of call have this issue makes it unlikely to be the fault of a fad among riggers. Others have suggested that as the coach roof subsided over the years from the pressure of the main mast, a bend formed as owners took up the slack in their forward shrouds. I tend to think there’s a lot to this idea.

And when considering the second… god help us. I spent several hours on Sunday attempting to tune out the bend in my main mast and only succeeded in confusing myself utterly. After endless fiddling, I thought I’d got everything just right, forestay extended, uppers and lowers taut and even, the mast more or less straight and with a few degrees of aft rake, and only then did I realized that the backstay was hopelessly looser than I had run on the turnbuckle.

So maybe you are better than I, smarter, handier with rigging screws. But those are the two dilemmas I face.

And if your question was meant more to ask is the mast safe to sail in its bent form—well, I don’t know, but I’ve been sailing Murre hard for several years that way.

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Replies:

[> [> Indeed, Randall! -- Gitano, - Thursday - 10/15/09 - 1:36pm

I just stepped a brand new Sitka Spruce main mast, which was perfectly straight until tuning the rig. Once everything was tuned, including split backstay, forestay, capstays and shrouds, the mast now has a slight aftward bend. Maybe its optical, but I think the boat was designed that way with placement of the chainplates and bowsprit. Besides, a slight pre-bend is desireable. http://www.zsparsuk.com/mhsstune.htm


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[> [> Interesting... -- Randall, - Thursday - 10/15/09 - 6:54pm

Hey Bruce, I was wondering how your new mast turned out. Thanks for sharing. It was sure a beauty on horses.

I tend to think you are right on both counts.

Some of the bend is an illusion in that the mast (at least my mast) has taper, but the taper is all in the leading edge, which creates the impression of aft bend when viewed from the mast's base.

Beyond that, though, I still have real bend, and try as I did, and even after giving the masts so much rake that Murre began to look like a bugeye ketch, I couldn't get all the bend out. More importantly, I couldn't get the spreaders to even up--they still had significant aft sweep, even with way more rake than I'd ever run with.

So I'm beginning to think that the M31 spec drawing on the MOA site (where the masts are straight and the spreaders at right angles) aren't what got built, and that the bend and spreader sweep was intentional (weird, but intentional).

More as it develops...


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[> [> [> Optical -- Bruce (Gitana Vela, M31 #95), - Thursday - 10/15/09 - 7:25pm

Yes, I remember Brion Toss mentioning is his last talk at Spaulding Wooden Boat Center, "when you step the masts, rake the mizzen back further than you would normally think is necessary because when you look at both masts from a distance, the perspective will make them seem parallel. Otherwise, they will look like they point together slightly" Anyway, My old main mast definately also had an aftward bend as well, so I figure thats how it is supposed to be.


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[> [> Mast bend -- jason elder, - Monday - 10/19/09 - 12:07am

Well everyone, I appreciate all the feedback.....sounds like everyone has a slight bend in their masts, so I will not worry alot until I send out in heavy winds, just reef it down. I have located the 1968 M31 hull#10 "MANANA" I purchased a week ago from a guy in Moro Bay Ca.She has a sound hull from the report I recieved from a hull diver I coax to check her out after he finished cleaning the neighbors hull, he said its amazingly sound no scuffs,or blisters. BUT...the cabin house is not to hot, around the portholes and the gangway..how can I find info on repairing the wood and frp? please help, as I want to restore this beauty, its my dream boat.


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