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To all,

I wanted to take my time to talk about the dramatic failure of the foremast case on my Tiki38 Pilgrim last saturday.

here is what happened: Going upwind in a 25/30 knots of wind, one reef in each sail, speed 7/8 knots, choppy water. Fast and tight.

As soon I noticed slack in the leeward shrouds and the mast case movin laterally, the case boke in 4 different places and the mast went down between the hulls. We managed to get everything back on the boat and lost nothing. Foredeck + mast case have to be rebuilt. Pilgrim will be hauled out tomorrow.

I called James Wharram the next day and got Hanekke on the phone. She knows me, and actually was waiting for my call as news go fast with the Internet. I emailed her pictures, and we rediscussed later.

We agreed on these points (from her email), and I appreciate very much her attention and openness about the problem:

"Thanks for keeping me informed. The photos are very clear. I think the breakage is a combination of

1) structure not enough safety factor

2) fatigue in the plywood after many cycles of pumping action in chop and waves

3) boat being sailed hard regularly

The structure has stood up for many years, but has eventually failed. We need to get a structure with high enough safety factor. I think the beefing up of the step with the extra pieces of hardwood will have done enough to strengthen it, but maybe a different design would be better still."

I want to add this: Aluminium masts are fine but have a tendancy to "pump" in heavy winds. So, I think there was also a resonance factor with chop, tight sheets and mast "pumping" which completely destroyed the box.

I will clean and rebuild, certainly with an improved design for the box, including materials like carbon and may be a dolphin striker.

To all T38 sailors: When going upwind, don't push too hard and keep an eye on your foremast.

To all T38 builders: you can already think about add strength to your box. It is not that difficult to do at this stage. I will keep you informed how the fix will go.

Cheers.

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We strengthened the underside of Peace's forward mast case by making bigger fillets which has been effective.  And also at the top we added bigger fillets and lots of fiberglass wrapping.  We also strengthened the bases of both masts and put a large block ahead of both masts to prevent them "walking" forward at the bases.  No problems since.  Inspect, inspect, inspect!  Ann and Nev

Fix is on its way.
1.Stronger plywood (moabi) twice stronger than okoumé
2. The big stringer of hardwood on the outside on the whole length
3. Deeper box

See pic attached. Hope that will be enough. Mast case is a lot heavier though.
Attachments:

If you care to wander, you can see what we did at ACatNamedDog.com.

Attachments:

sorry to read only now this posts and to have not informed then my experience.

in 2010 my T38 showed crack in the fore part of the mast case and we had to reinforce it.

no more problems since then.

In 2012 I had also with my Jumpa Lagi the same failure as Jacques describes, and it happended in the same conditions: beating against 20-25k wind and waves. The pictures (see below) are strikingly similar. The causes have been documented, the main one being that it's a weak point of the design, that has been now corrected. The case was repaired with plenty of additional strength and since then, no problem anymore, even in similar wind conditions. I can't advise too strongly all T38 owners to reinforce their mast case support before it happens. Although I was lucky and there was very little collateral damage (planks from the deck around the mast and one solar panel whose wire was crossing the boat right under the mast), it is a very stressful experience.

Hi Jacques and others.

I have just bought a 12 year old Tiki 38 in Melbourne, Australia. Her name now is Sarayu, but previously was Electric Guitar, so I dont know if anyone knows her. Anyway, her hulls and crossbeams are in excellent condition, a testament to the original builder and the effectiveness of ply/glass/epoxy building techniques. Her tabernacle is made of 300 x 38mm hardwood, and one side is showing signs of distress. I will try to mend it by clamping and glueing, and keeping an eye on it for more stress. However, it seems to me to confirm what Jacques said about sideways stress on the tabernacle. The rig is fairly loose, and I wonder what kind of tension should be on the foremast. I think I remember Neville saying something about tensioning the rig to improve the pointing, obviously to keep the forestay taught for the jib. One of the things which attracts me to the Wharram design philosophy is the low tension rig and the organic nature of the system, and I wonder what kind of tension the tabernacle was designed to take. 

Regards,

Dave E

Trying to get the best tension without bending the mast (Aluminum). I changed lashing to dynema which helps a lot.

That is a compromise. Lack of tension will mean sideway moves, too much tension will mean more stress on the mast case.

I am obviously not a good example to follow !!!

i realize one good thing among the bad ones: it seems that the masts didn't break!

Sarayu's masts are wood with glass/epoxy coating and seem to be as strong as Fort Knox. I think the mast would go through the tabernacle before it would start to bend, so I guess the question is, "How strong should the Tabernacle really be?"

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In my case it is not the tabernacle itself that broke but its aft part, its support sitting on the cross beam. This is a crucial part because it bears a significant part of the weight of the tabernacle itself, plus the mast, the mast compression when sailing, the anchor, the chain, the adjacent wooden deck and the people walking on it!  After the accident, I noticed that this crucial part supporting a considerable weight on a small area was partly made out of plywood and that it was rotten. As we know plywood is very sensitive to any water infiltration, especially in tropical environment. It has probably been enough that a minimal amount of water has penetrated the epoxy coating to weaken a crucial point of the structure and cause a failure.

I guess the remedy has since been well described by the designer: reinforce the tabernacle by long/ full length plain wood stingers on both sides. For Jumpa Lagi, this is what has been done when repairing (probably overkill by the way:-) and I'm not worried any more with this issue!

Fix is on its way:

* Deeper box

* Best plywood (Moabi)

* Two additional stringers in hardwood

* Filets everywhere, glass everywhere

Hi Alf, would you mind to post a foto or send me ine? I am not sure I completly understand your mast case design, but I wouöd like to do something about re-inforcement, since I had several rot areas in the mast case.

Kind regards,

Helles



Alf Bangert said:

Dave,

I totally agree with not using shims between the mast and the top of the case;  there is no way even a very strongly built case could restrain the sideways loads of the foremast under sail.  In fact,  those forces may have been instrumental in several failures.  I keep the rigging on Kattu tuned so there is an equal gap behind the mast as at the sides,  and the mast never touches the case even in heavy weather.   I also agree that the rigging should not be overly tight;  there is no advantage to that on the wingsail rig and tight rigging adds to the compression load at the mast step. 

I checked out Wharram's improvements to the mast case,  and perhaps they do not go far enough.  When building Kattu's mast case,  I increased the sides thickness to 18 mm,  and increased the overall depth of the sides from 280 mm to 406 mm,  so that the bottom of the case is flush with the bottom of the beams.  This makes for a vastly stronger truss,  which in effect the case is.  It also provided nice chain fall from the windlass,  with the chain storage imediately below and forward of the windlass instead of in front of the mast....automatic chain feed in or out and the weight is further from the bows.  Mostly I stuck to the plans,  but when I saw the foremast case drawings my intuition kicked in and said "make that much stronger"....I'm so glad I listened!

-Alf

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