Even though people say, in this Forum and elsewhere, that too much downhaul will rather tear the sail than break the mast, I did break my mast the other day by using a winch. Mine was a constant curve 460 cm Gun mast only used a few times . Yesterday, to my surprise, it snapped, under the tension of the winch, fortunately when I was still rigging the board on the beach. The section that cracked was the upper one, right at the junction, where the inner prong starts . It was a clean longitudinal crack ,and followed the vertical seam of the mast for about 4-5 ''. I took a chance and sawed the cracked section off by about 15 cm. I then rerigged the sail with the shortened mast and downhauled carefully. It seemed to work, or at least the mast did not break again. Perhaps I have lost some performance, but I am not too fuzzy about it.
Any comments about possible safety issues?

Thanks

Francone

Montreal, Canada

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Francone said..

Even though people say, in this Forum and elsewhere, that too much downhaul will rather tear the sail than break the mast, I did break my mast the other day by using a winch. Mine was a constant curve 460 cm Gun mast only used a few times . Yesterday, to my surprise, it snapped, under the tension of the winch, fortunately when I was still rigging the board <nobr>#</nobr>. The section that cracked was the upper one, right at the junction, where the inner prong starts . It was a clean longitudinal crack ,and followed the vertical seam of the mast for about 4-5 ''. I took a <nobr>#</nobr> and sawed the cracked section off by about 15 cm. I then rerigged the sail with the shortened mast and downhauled carefully. It seemed to <nobr>#</nobr>, or at least the mast did not break again. Perhaps I have lost some performance, but I am not too fuzzy about it.
Any comments about possible safety issues?

Thanks

Francone

Montreal, Canada

The mast broke bec of too much force exerted, and possibly some weakness in mast. If you'd down hauled by hand to the same extent it still would have broken. The only danger is you may have downhauled and applied extra pressure using a winch, which you may not have done downhauling by hand, as you are more likely to feel the force being exerted. As for safety issues re repaired mast? Not sure, let a tech head answer that one.

Any possibility that the two sections weren't together properly? Sounds like the bottom half mast may not have been fully inserted.

Of course this is a guess and I could be completely wrong.

Canada eh? Probably made brittle by the cold...

I'm with Benkirk, a lot of people tape the 2 sections together before rigging, this keeps grit out of the joint so it doesn't lock up, and makes sure the 2 halves are fully together. The bigger the gap in the join the more likely it is you'll get a longitudinal split.
Masts normally have a reinforced area around the joint to take the splitting load, if your mast had one you've now cut it off!
It would be a good idea to wrap a few layers of carbon around the new end.

There have been several reports of masts breaking here in the last couple of years, some while rigging and some not long after, with no impacts to cause them, and the only damage to sails caused by sharp broken bits of carbon tearing them. No sign of sail itself giving way because of too much downhaul. Obviously the people who say the sail will tear before the mast breaks, aren't always right.

spot on Decrepit, happened to my son twice in two months with the same sail. First was a hot sails mast 65% and then a loft mast 100%.

Both broke when rigging (no winch,just the little bloke) no damage at all to the sail. (ox webbing though on the Hot GPS)
Nothing to do with adjustment as they both broke at the top of the bottom section....

Generally when I have over cranked, the DH rope was first to go!

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decrepit said..


Masts normally have a reinforced area around the joint to take the splitting load, if your mast had one you've now cut it off!
It would be a good idea to wrap a few layers of carbon around the new end.

Never thought to wrap around a few layers of carbon ! It would be easier with fiberglas,though, but probably it won't work, because a friend of mine did it and the mast ripped apart again right on the same spot. But where do I get the carbon for the repair and how do I do it?
Incidentally,if I look at the cross-section of the mast after sawing it off,( i.e. the thickness between outer diameter and inner diameter) the mast seems now to be visibly thicker at the joint than before, so may be it is stronger now, after all.

Any comments or suggestions ?

Thanks

Francone

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BenKirk said..

Any possibility that the two sections weren't together properly? Sounds like the bottom half mast may not have been fully inserted.

Of course this is a guess and I could be completely wrong.

I doubt it, because the two sections fit together completely by hand and the pressure of the downhaul is such that the two sections cannot possibly move apart.

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Francone said..
. . . the two sections fit together completely by hand and the pressure of the downhaul is such that the two sections cannot possibly move apart.

The mast sections may have been correctly fitted together to start with, however, by the time you have threaded the mast along the mast sleeve, concertina-style, the sections could well have moved apart. Downhaul applied at this time will not bring the sections back together; there's too much friction in the join.

Either duct-tape the sections together, as Decrep suggests, or, before downhauling, check for a gap by running your fingers over the sleeve where the join would be.

If there's a gap, you have virtually no choice but to remove the mast mostly from the sleeve, remove the gap, and reinsert. And, of course, check that the gap is now not there, before downhauling.

hate duck tape - leaves sticky residue + large
prefer lektric - smaller n many colours

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Francone said..

Never thought to wrap around a few layers of carbon ! It would be easier with fiberglas,though, but probably it won't work, because a friend of mine did it and the mast ripped apart again right on the same spot.

Hmmm, you have to think clearly here, just because your friends attempt didn't work, doesn't mean the idea isn't worthwhile.
I'm not suggesting a repair to a cracked mast with just a few layers of carbon, that just isn't adequate. What I'm advocating, is replacing the end reinforcing, that's removed when you shorten the mast.

If the mast hasn't been shortened enough and there's a hair line crack left, that will be a weak spot, it will need a lot of fibres there to be strong enough.

If it's a fibreglass mast, a fibreglass repair is the way to go, but if the mast's carbon, fibreglass won't do much good. Carbon is soo much stiffer than glass, that in a glass/carbon mix, the carbon ends up taking all the load, if there's not enough carbon there to do that, it will fail, causing a weak spot, then the glass will also go.

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But where do I get the carbon for the repair and how do I do it?

,
I've no idea about Montreal but in Perth, the same people that sell fibreglass also sell carbon.
An other alternative is an online order from the USA, I bought my last lot of carbon that way, was almost 1/2 the price I could get it locally.

For this repair I'd prefer a unidirectional tape, rough the mast end up with about 100grit sandpaper, then with a small brush, paint a bit of epoxy resin on the mast where the carbon is going, start wrapping the carbon over the resined area, twist the mast and keep repeating the process until you have 4 or 5 layers. Wind the carbon as tight as you can, paint a thin layer over the outside carbon so it's all "wetted out". Then you can wrap a wider strip of thin plastic over the carbon, again as tight as you can, keeping as smooth and free of wrinkles. Then tape that as tight as possible to stop it unwinding. That will squeeze out surplus resin and give you a nice smooth finish.

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Incidentally,if I look at the cross-section of the mast after sawing it off,( i.e. the thickness between outer diameter and inner diameter) the mast seems now to be visibly thicker at the joint than before, so may be it is stronger now, after all.

Any comments or suggestions ?

Thanks

Francone

That may be a manufacturing defect, the end reinforcing may not have been at the end!
That could be the reason the mast split, and as you say may no be at it's correct strength.
Is there any way you can work out how far up the mast the extra thickness goes?
As the split is going to start from the end it probably doesn't need to be the full length of the join.