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Old 26-11-2010, 10:06   #1
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Broken Mast - How Can I Repair ?

I Own Brown Searunner 37 and I am currently in Guaymas, Sonora Mexico. Had a starboard chain plate give way and brought down the mast at the first spreader. Masthead, twin spreader rig 44 feet high. What techniques or advice can you offer for repairing the mast via sleeving and welding? Cross section of the mast is 9.5X5.5" Elliptical, 9/64' wall thickness. Ron Auth S/V Hotspot

Help!! Any advice on sleeving the mast and welding the break. has anyone done this on a mast of our size(see above)

Have a local shop here in Guaymas says he can do it, but some say not to. Any advice appreciated and things to watch out for if I decide to sleeve.

Thanks

Ron
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Old 26-11-2010, 12:12   #2
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Sleeve it. It's best to make a sleeve from the same mast section, but of course this may not be possible in your situation. So make it up from aluminum of similar thickness. Make it fit well and tight. Maybe about 3 feet long. Use rivets spread around about 3" apart. S/S Rivets of about 1/4" should work. You can weld the mast ends together, or not. Don't weld the sleeve to the mast sections. Preserve the length of the mast to avoid endless other problems.

Almost all masts longer than 40' are sleeved somewhere.
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Old 26-11-2010, 13:33   #3
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Agree with Daddle. Build or buy a sleeve. Tight fit, attach with many rivets. No welding, it will weaken the aluminum.
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Old 26-11-2010, 14:01   #4
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I have tried to weld masts before, and in spite of 30 years welding experience, a VERY expensive TIG machine, and tons of patience, it was never quite right. Don't get me wrong, they have held up; they just didn't look good. I suppose if one had a jig big enough to keep the mast true it would work OK, but making the jig would cost more than a new mast. Similarly, fabricating a sleeve for an exact fit would be pricey, as would the possible need of smaller sails, rigging, etc.

My $0.02? Get another mast!
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Old 26-11-2010, 15:06   #5
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G'Day Hotspot,

First, condolences on the breakage... not fun, and usually expensive.

AS to the repair... the above responses that advocate sleeving are correct, maybe!

The issue is getting a sleeve that fits very well indeed. Masts that come from the spar builder with a sleeve invariably use an extruded section that fits the main extrusion perfectly. This is usually just a section of the "next smaller" mast section from the same manufacturer. AS noted, this method of splicing works just fine, and is holding many masts together throughout the world.

But, with your rather old mast, such a bit may be difficult to source. If you can't get the right section the chances of fabricating a sleeve from scratch are not good IMO. If you intend to use the boat where having the repaired mast fail would put you at risk, I'd think seriously about replacing the whole spar. I know that isn't what you wanted to hear, mate, but being dismasted far at sea is a distressing event. Don't ask how I know that!

Good luck with your search and your repair.

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Old 26-11-2010, 21:41   #6
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Sorry about the break.

Pulse welding would work with an insert sleeve but the rivets are far simpler. Rivet every square 1" if bucked style and 3/4" if blind rivet style.
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Old 26-11-2010, 21:50   #7
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Rivet every square 1" if bucked style and 3/4" if blind rivet style.
I've not seen a sleeve with that many rivets from the spar factory. About a tenth of that is typical. Maybe your number is for ultimate strength, which is probably not a concern for masts as they always break after bending.
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Old 26-11-2010, 21:56   #8
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Hey Daddle.

Most masts are about 40K torsional yield. I was thinking of sheer of the rivets in light material. Any idea of wall thickness?
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Old 26-11-2010, 22:01   #9
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oops 9/64"I see it.
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Old 26-11-2010, 22:53   #10
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Ronnmexico,
I'll second the above posts. My Isomat mast was repaired using a pair plates as a sleeve and ss rivets. The plates were made specifically to fit the mast. After three years no problems.

Paul
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Old 26-11-2010, 23:18   #11
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Paul where in Houston are you? I am in Houston. You can reach me at jimships@yahoo.com
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Old 27-11-2010, 04:37   #12
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Check your mast section with Dwyer (> Dwyer Aluminum Mast Company- Manufacturers of Quality Sailboat Masts, Booms, Hardware and Rigging Since 1963. <) and see if they've got the extrusion you need (very likely), as the proper fitting extrusion makes a huge difference in the repair. Dwyer routinely buys up the dies for common sections.
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Old 27-11-2010, 07:05   #13
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Broken mast repair

Thanks to all that have commented. the issue seems to be the welding. Everyone agrees that sleeveing is an efficient way to repair the mast but there is disagreement on welding. here is the problem: where mast broke it made a nasty tear that would require cutting off at least 3-4 inches on each side of the break to clean up hence the mast is 6-8 inches shorter. I don't have that leeway. Shop here in Guaymas says don't trim the tear. Flatten out and weld along the ragged edge thereby saving the height of the mast and repairing it to it's original length. But when he welds the break, he will weld the sleeve as well. This is where the "welding weakens the metal"crowd come in. It will weaken the mast but the sleeve is to be made out of a harder alloy(according to the shop) and so the weakening,although present, is far less than one would think. The repaired mast(according to the shop) even with the weld, will be far stronger than the original mast.

Other solutions that have come up are cut off a piece from the bottom of the mast, trim away tear debris on break, and insert sleeve and bottom section of mast at break, weld.

What do you think? Weld the ragged tear or trim and fill the space with piece from bottom of the mast.

Of course that would then require raising the mast step a distance equal to what was removed from the bottom.

Great comments so far, now some specifics please.
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Old 27-11-2010, 07:38   #14
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As I said.... I've been welding for years... I've NEVER had a mast turn out satisfactory for me. I've sleeved/riveted with some success, but that will shorten the mast and require the sails and rigging to be similarly shortened.

The problem with the welding is loss of temper. I did a mast once that looked perfect until it was loaded, then it had a distinct bend at the joint.... It was discarded! IF you decide to have a local shop weld the mast, INSIST on payment only after satisfactory installation and full loading on the boat. I'll bet the shop declines, as they know it will bow at the mend!

OEM masts that are welded (which are rare) are post-tempered, thus welding is not an issue
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Old 27-11-2010, 07:52   #15
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Sleeve AND weld, or just sleeve.

I will be sleeving the mast, the question is how to close the break. Should I allow it to be welded? Strength will be in the sleeve, BUT, when the break is closed it will weld the sleeve at that point. I will of course rivet or machine screw the sleeve BUT, again it's the welding thing--what to do?

And how to close the break in the mast.
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