Broken mast Halo Wind

[Sebsky]

Hi,

Last Saturday was gusty in Brest but not to the point that I’d say that the dogs where off their chains (15-20 kts).  Even though, while bearing away, two on the wires, up to put the kite up, the mast broke.  Hopefully, the main and jib remained unaffected. 
Back onland, we discovered that the mast has broken some 80 cm below the first spreader.  We suspect a mechanical weakness there to be the underlying cause since none of the textile shrouds has broken. 
We’ve already found a windsurf mast that fits ideally within the cherub one and providing we find a long and wet enough place it should soon be fixed.
It is also planed to replace the textile shrouds by new ones made of steel.
Does anyone know if our diagnostic about the mast failure is the good one or do we have to put more weight on the progressive stretching through aging of the textile shrouds to explain where the failure occurred. 
Although we have a quite clear idea of how to fix the mast, any advices would be welcome.

[roland_trim]

A mast breaking 1/2 way between goose-neck and first spreaders is a break we have not seen in the UK for the past few years*

I think I follow your comments about more flexible shrouds causing a problem. It would help to know your rig layout - could you send a sketch of your rig (i.e where the mast steps, lowers, uppers and/or d2s?)


(* except Beans and hers broke in so many pieces who can tell)

[Sebsky]

here's a picture highlighting  the rig layout and where the mast broke

[phil_kirk]

You said that the break happened when you were bearing away to hoist the spinnaker. Did the broken ends move to the windward side of the boat with the top of the mast falling to leeward or the other way round.

If the break moved to the windward side I would agree that the D2's and lowers were too stretchy.  If the kicker was also tight and the boom eased for the bear away this would pull the mast tip to leeward putting bend in the mast.  If the cap shrouds were also stretchy the top of the mast would be allowed to bend.

We use 3mm wire on our main shrouds our D2's but have SK78 dynema for our cap shrouds and lowers. You ocassionally have to tighten the Dynema shrouds as they do creep with age. 

[Sebsky]

the broken ends of the mast moved to the leeward.


thanks for the tip 

[Stuberry]

Is it the original mast from Halo Jones? I think that was the first c-tech mast for a cherub in the northern hemisphere, about 10 years ago. So it's very old and maybe failed due to it's age.

[Sebsky]

I'm not quite sure about whether it is (was?) the original mast of Halo Jones but investigating this way is likely to provide some additional answers.

[JimC]

Well its certainly not Halo's original mast because that's tin and in my garage... The C-tech spar that went to France with Halo was delivered in August 2002. It was of course specified for single string (but heavy crew) and a 12.5m2 rig.

Any chance there was any kind of loss of rig tension? Or conversely might you have been running more tension than normal?

You've got a mast stump to gooseneck still I presume, is that right? Halo's rig when it went to France had the caps coming back to near the bottom of the stump terminating in forged shackles with carbon uni bandages onto the spar, and a bit of reinforcement on the spar. Then there was just a short tenon on the stump into the spar which wasn't supposed to contribute anything more then locate it in place.

If so the break really is in a funny sort of place because in my day there was nothing locking the mast in place below the checks, so maybe some kind of compression failure. Hard to believe there coule be anything in the spar coming to light after all these years, and the lower section really was quite substantial. Any chance of any impact damage - a big bash on shore or something that could have hurt the tube?

[Sebsky]

Halo Wind doesn’t have a mast stump to gooseneck.  So, before last Saturday it used to be in a single piece.

Even if hardly noticeable, some loss of rig tension may have occurred through creeping of the textile shrouds.

I can’t remember of any big bash on shore but it’s likely that the mast have suffered a bit from the previous week end when we sailed and capsized two days in a row in 20 kts +.  While the gooseneck has been torn out on the first day, sailing on Sunday seemed to prove the whole rig to be trusty.

[phil_kirk]

Thankyou for the detailed description. 

I tend to agree with Jim that it could be some kind of compression failure but combined with the mast being allowed to bend a bit + a small hidden defect within the laminate that helped the mast to buckle.  Micro cracks or delaminations in the laminate would seriously weaken the mast but be completely visually undetectable from the outside.  Could be the combination of a number of knocks and scapes from over the years.

[Sebsky]

Now this discussion has arguably shed light on the most likely factors that led to failure, I’ll be glad to learn more on the tension ranges to put on the shrouds, and how often the tension of those made of textile should effectively be checked.

[Sebsky]

Now she’s sick of her broken mast, Halo Wind tends to warm up at pepperoni on the fire parties . Just hope she’ll quickly loose this bad habit to go back on the water soon.

[JimC]

Halo Wind doesn’t have a mast stump to gooseneck.  So, before last Saturday it used to be in a single piece.

OK, so not the ex Halo Jones mast then. Were there lowers? How was kicking strap induced bend controlled?