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PostPosted: Fri May 19, 2017 9:51 am 
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Masts are a part of any sailboat that are subject to high loading, but they need to be lighter weight and flex. They are not tree trunks by design requirement. This can make them susceptible to damage from capsize, improper handling and over stress loads. If we made them strong enough to handle all the potential abuse... they would not perform well... they would be heavy...

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PostPosted: Sun May 21, 2017 3:10 pm 
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I took a look at my mast on the weekend. Have had the boat for about a year now and been on maybe 10 outings on her. Obvious scoring of the surface of the mast can be seen. I plan to tape the mast and the back of the cleat to nip this in the bud, but I'm also keen to understand the extent to which scoring of this type could affect the integrity of the carbon fibre mast.

The scoring isn't around the whole circumference of the mast, but is limited to 25-30% it appears.

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PostPosted: Sun May 21, 2017 4:49 pm 
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Smithcorp,

That looks similar to my scoring. I plan on picking up some PTFE or UHMW tape to stop the chaffing. I'm not a carbon fiber expert or a marine engineer so I'm taking a conservative approach to this. I think all we are looking for is for Hobie to address this with the engineers and let us know if the scoring can result in a mast failure. If so re-engineer the cleat attachment for future models. Matt Miller's comments earlier were somewhat dismissive. We're all sailors and we understand that a mast can't be a tree trunk. More weight aloft is always bad. But, we're not talking about the masts being under engineered. Obviously they are not otherwise we would have a lot more mast failures. What we're asking is, is there a correlation between the chaffing from the cleat and recent mast failures?

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PostPosted: Sun May 21, 2017 6:44 pm 
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Those pop rivets holding the cleats are not going to score all the way around--they'll only score while the sail is moving from one side to the next (gybes mostly). They could also score while furling or while transporting but probably not as much. Heading upwind the mast bends away from the cleat. Downwind, the mast bends toward the cleat--if you don't release downhaul tension to go downwind (as you should), the cleat has even more tension against the mast.

I would not recommend tape as a temporary fix. The sharp edges on the pop rivets will still provide a point load for mast failure. Drill them out--why futz around? After reattaching the cleat (if you choose to do so-lotsa alternative methods for luff tension) you may want to add some thickened epoxy to the score marks.

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PostPosted: Mon May 22, 2017 10:41 am 
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tpdavis473 wrote:
the pop rivets will still provide a point load for mast failure.


There is no "point loading" from the rivets. The concern is chaffing of the mast material. I still do not see a failure directly related... just near by.

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PostPosted: Mon May 22, 2017 11:00 am 
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Don't be stupid.

First, it is chafing, not chaffing. If you are going to act like you have superior knowledge at least get the spelling right.

Second, look at the rivets. Look at the POINT that is left behind by the pop rivet shaft.

Third, EVERY brittle failure of material has a point of initiation. All those mast failure photos show brittle failure. QED.

Fourth, don't argue with a nuclear engineer about material failures.

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PostPosted: Mon May 22, 2017 11:47 am 
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tpdavis473 wrote:
it is chafing, not chaffing.

I think autocorrect got me on this one. :oops:

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PostPosted: Mon May 22, 2017 1:36 pm 
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Wow... an incorrect spelling does not make one "stupid". Gee... thanks for that... I don't think I am, but may sometimes be a sloppy typer. I reply to a lot of posts and am often distracted while doing so.

Thanks also for clarifying your field of expertise. I don't believe you have an Island though, correct?

I don't believe there is a point load issue... There is no "pressure" against the cleat towards the mast. That is what I would call "point load".

Quote:
Point load (P) is a force applied at a single infinitesimal point at a set distance from the ends of the beam. Return to Calculator. Uniform Distributed Load (q) Uniform distributed load (q) is a force applied over an area, denoted by q which is force per unit length.


Related? I have not seen a failure that appeared to be directly related to this area of "chafe". Failures that I have seen appear well above this point. If I can get more direct evidence of a correlation, I can pass that on.

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PostPosted: Mon May 22, 2017 1:55 pm 
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mmiller wrote:
Wow... an incorrect spelling does not make one "stupid". Gee... thanks for that... I don't think I am, but may sometimes be a sloppy typer. I reply to a lot of posts and am often distracted while doing so.

Thanks also for clarifying your field of expertise. I don't believe you have an Island though, correct?

I wouldn't take it personally Matt. I couldn't figure out who "tpdavis473" was referring with his remark, "Don't be stupid." Frankly, I found him to be amazingly arrogant, especially for someone who apparently does not own an Island.

Keith

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PostPosted: Mon May 22, 2017 3:29 pm 
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Hobie might want to get the opinion of their mast supplier. Its not an issue of point loading, its simply that the sleeve of sail moves with respect to the mast during normal operation of the boat (such as tacks or furling) and the rivets on the cleat are very likely wearing a groove in the mast. It looks like to me in the picture someone posted that the groove likely even cuts through the glass or carbon fibers in the mast.

Im not a mechanical engineer but I believe the highest structural strain is at the very outer surface of the mast and also near the bottom of the mast where it attaches to the cross beam. That is exactly where the rivet is cutting the groove. It takes years of movement between the mast sleeve and the mast to wear the groove so is that really an issue or not to Hobie.. dont know.

About everyone who inspects their mast will see some stage of the picture below.. I checked mine and I had some wear on the mast and I think the original poster had it correct.. its the rivets that are causing the wear and the wear is in a really bad spot.

Picture below was posted earlier in this thread. No longer an issue for me as the rivets and cleat are now gone on my sail and of course I could be wrong. Its an overall small thing to nit pick on and I also think the Hobie TI is about the coolest sailing vessel I have ever owned.. I just love mine.

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PostPosted: Mon May 22, 2017 3:37 pm 
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Yes, I am arrogant. It is very difficult to deal with folks who don't know what they are doing when one does. No reason to be humble when you are always right, right?

As I pointed out in a previous post on this topic, the point load is created because when traveling downwind the mast bends forward at the top, but the bottom bends back TO THE CLEAT=specifically to the pointy piece of material left of the mandrel of the pop rivet. I don't have to own a TI to be able to figure that out--especially since one of my boats is very similar (the Triak). The load comes when someone incorrectly fails to release the downhaul when going downwind thus creating a load on the shaft of the mast.

Heck, the pop rivets themselves are probably not creating the scoring, it is likely only the pointy piece of the mandrel--grind that off with your dremel and repair the mast with thickened epoxy--good to go. I recognize that most TI owners are novice sailors and unaccustomed to taking care of their own stuff...I routinely browse these lists since I am knowledgeable about a very many aspects of sailing and willing to help out floundering folks. I certainly haven't learned anything new here.

Masts should not break. They do fail, but they ought not break in half. I don't know who determined the carbon layup for this mast, but it does appear "different" than most carbon masts I've seen.

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PostPosted: Mon May 22, 2017 3:55 pm 
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You sort of lost me when you corrected someones spelling but really lost me on that last post..


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PostPosted: Mon May 22, 2017 4:46 pm 
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FYI, the first picture is of the backing assembly for the cleat that I removed (2015 TI). I took this picture and posted it here to show that the rivets used in the original sail construction are "smooth" on the side that contacts the mast. On the right side you can see a bur but that was created when I used pliers to keep the rivet from spinning so I could remove it.

Image

This second picture is from the original poster whose mast busted. You can see that the rivet used is different than the stock and I think the OP said the original rivet had failed and was replaced. It is a different type of rivet and you can see the post or mandrel that breaks off in the center of the rivet. I think even the smooth rivet will create wear given enough time but that sharp point created when the mandrel breaks off could certainly accelerate cutting into the mast.. I wonder how long before the mast broke was the rivet replaced with the one shown in the second picture?

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PostPosted: Mon May 22, 2017 5:06 pm 
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Good eye walt.

It looks like one of the rivets on yours was worn flat?

Fyi... the location of the cleat does rub harder on the mast when the sail is sheeted hard, but this location is the same as from day one of Island series boats. It likely gets the majority of "chafe" from the furling action or rotation during tacks when not as loaded.

We did experience some mast failures early on that were (for sure) not related to this as they were too early on to have been worn in this way. That was a mast manufacturer issue that caused us to do 100% stress testing of the masts. As a side note, The mast maker is a World leader in windsurf and kite products. I don't think they are trained as a nuclear engineers though.

I asked our Senior VP of engineering to have a second look.

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PostPosted: Mon May 22, 2017 5:08 pm 
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Quote:
It looks like one of the rivets on yours was worn flat?


More likely caused by me trying to keep the rivet from spinning with some type of pliers when I drilled it out from the other side..


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