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Carbon Fiber Masts #102473
03/31/07 03:41 PM
03/31/07 03:41 PM

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I am interested in learning more about beach cat carbon fiber masts and their construction. The resent failure of an ACat mast vs. the I20s where I have never heard of a mast failure makes me think that they can be constructed with greatly different factors of safety.

It seems (I have not looked at the math) that the primary loading is going to be a compression load down the length of the mast. Does this mean they use primarily unidirectional cloth oriented vertically? This seems to have the added benefit of allowing the mast to bend more to flatten the sail. There are bending loads so there probably has to be some unidirectional or bidirectional fiber oriented in the horizontal direction.

Has anyone ever seen a lay-up schedule for a mast or looked at a failed mast and seen how many layers of cloth was laid up and/or how they were oriented?

Are carbon masts are much stiffer than aluminum masts? If so, how does this affect de-powering?

An idea of the differences in Sail design between carbon and Aluminum masted boats?

-- Have You Seen This? --
Re: Carbon Fiber Masts [Re: ] #102474
03/31/07 08:28 PM
03/31/07 08:28 PM
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I know that carbon masts are more rigid than aluminum, but as for everything else you asked, dunno. I think it may be harder to depower a carbon mast than an aluminum mast, but it would be more a function of the downhaul which would need to be stout enough to bend the carbon masts

Re: Carbon Fiber Masts [Re: ] #102475
04/01/07 08:01 AM
04/01/07 08:01 AM
Joined: Jun 2001
Posts: 305
toronto, canada
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basket.case Offline
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toronto, canada
about 70% of the fibres are in the 0 deg direction. the off axis fibres are there to hold the 0s in column and stop them from bursting when the mast flexes.
the first carbon mast i built for my boat had 2 plys of 200 gram fibre glass cloth at 0/90, 4 plys of 300 gram standard modulas carbon uni at 0 and one ply of 500 gram fibre glass at 45/45. it failed after six years of use. snapped just below the hound. we put it back together in two days and finished the season with it.
the new section i am building is out of 200 gram t 700 high modulas carbon, one ply at +/- 60 degrees, 5 plys at 0 and one ply at 90 degrees. we are adding a web in the centre built out of 1 ply at 0, 3 plys at 90 and one ply at o.
the first tube was 65 pounds and all wet laminate. i am hopping the pre preg mast will be about a pound a foot for its 35 foot height.

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Re: Carbon Fiber Masts [Re: ] #102476
04/01/07 08:06 AM
04/01/07 08:06 AM
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South Carolina
Jake Offline
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There have been plenty I20 mast failures - probably inline with the frequency of aluminum mast failures on other boats.

I think the carbon N20 mast is a bit more flexible than some other masts but it's a pretty small section.


Jake Kohl
Re: Carbon Fiber Masts [Re: ] #102477
04/01/07 08:33 AM
04/01/07 08:33 AM
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uk
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one of the main advantages of the carbon masts is that they can be built to any stiffness - anything from a telegraph pole to a flyfishing rod. The amount of flex can be varied by the lay-up used.
Yes n20 masts do break! - very loudly![99 percent of the time due to operator error]


Paul

teamvmg.weebly.com
Re: Carbon Fiber Masts [Re: Jake] #102478
04/01/07 08:47 AM
04/01/07 08:47 AM
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Quote
There have been plenty I20 mast failures - probably inline with the frequency of aluminum mast failures on other boats.

I think the carbon N20 mast is a bit more flexible than some other masts but it's a pretty small section.


Thats funny, no one ever quotes how often the masts break on I20s as evidence of them being such underbuilt, bad boats

Re: Carbon Fiber Masts [Re: PTP] #102479
04/01/07 09:37 AM
04/01/07 09:37 AM
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Posts: 6,049
Sebring, Florida.
Timbo Offline
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You can destroy anything if you try hard enough. Remember the one year of the Worrell when the surf was huge and on the nose, when the I20 fleet tried to launch through it at the start, most of them broke something, rudders, masts, etc. I think only 5 of the 21 boats made that leg, the others trailerd to the next stop.

I don't blame the boat for that, and just like snapping the mast if you are doing something wrong, it's not the mast's fault.

Heavier usually means stronger until you change material. We know a "strong" fiberglass 20' cat is going to weigh 400 lbs. But carbon is stronger and lighter than aluminum, and fiberglass, that's why Boeing is now building the 787 with as much carbon as they can. All the new Unlimited Aerobatic Competition airplanes are being built of carbon. The A cats are all carbon. Carbon is the future if you want to go faster. But Carbon is expensive. So all we have to do is mass produce it cheap enough to replace fiberglass.

I don't have any knowledge of what it costs to produce carbon vs. fiberglass. If there are any carbon industry experts here, I would love to know. Is it the raw material that makes it so expensive or the manufacturing process, or limited supply or all of the above?

Last edited by Timbo; 04/01/07 09:39 AM.

Blade F16
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Re: Carbon Fiber Masts [Re: Timbo] #102480
04/01/07 10:44 AM
04/01/07 10:44 AM
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Thats funny, no one ever quotes how often the masts break on I20s as evidence of them being such underbuilt, bad boats


Your defensiveness over the HT is really getting bitter, ain't it?

Re: Carbon Fiber Masts [Re: MauganN20] #102481
04/01/07 10:46 AM
04/01/07 10:46 AM
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Michigan
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Quote
Quote
Thats funny, no one ever quotes how often the masts break on I20s as evidence of them being such underbuilt, bad boats


Your defensiveness over the HT is really getting bitter, ain't it?


Horribly bitter... about everything these days. I think I just want to start a fight. You should see how bitter I am at my crappy job. I have said it before, and will say it again... NEVER take a job you can't quit.

Re: Carbon Fiber Masts [Re: PTP] #102482
04/01/07 10:50 AM
04/01/07 10:50 AM
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I understand man, I get the same way about things that really bother me.

Re: Carbon Fiber Masts [Re: MauganN20] #102483
04/01/07 11:03 AM
04/01/07 11:03 AM
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And if this thing with Iran gets out of hand, I may not be able to finally quit when I am finally able to.

Re: Carbon Fiber Masts [Re: MauganN20] #102484
04/01/07 11:08 AM
04/01/07 11:08 AM
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Quote
Quote
Thats funny, no one ever quotes how often the masts break on I20s as evidence of them being such underbuilt, bad boats


Your defensiveness over the HT is really getting bitter, ain't it?


You really like stirring the pot! I think I'll rename you spoon.

Re: Carbon Fiber Masts [Re: PTP] #102485
04/01/07 11:24 AM
04/01/07 11:24 AM
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Panama City, Florida
Redtwin Offline
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Quote
Horribly bitter... about everything these days. I think I just want to start a fight. You should see how bitter I am at my crappy job. I have said it before, and will say it again... NEVER take a job you can't quit.


I'd say you are at about stage two. To see what is to come in the following stages see the link below.

http://youtube.com/watch?v=prdwiy37pXQ&mode=related&search=

My favorite is depression.
<img src="http://www.catsailor.com/forums/images/graemlins/crazy.gif" alt="" />


Rob V. Nacra 5.2 Panama City
Re: Carbon Fiber Masts [Re: ] #102486
04/01/07 12:17 PM
04/01/07 12:17 PM

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Thank you all for the replies, very interesting. Anyone have any other info?

Re: Carbon Fiber Masts [Re: ] #102487
04/02/07 08:56 AM
04/02/07 08:56 AM
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Posts: 778
Houston
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Houston
Quote
Thank you all for the replies, very interesting. Anyone have any other info?


I have a section Marstrom A-Class mast, it's about 3mm including core. I am surprised at how light it is.

Also, A-Class pitchpoles are violent things. It doesn't happen often and usually happens when the boat has been pushed way past anything normal or you are just plain unlucky.

Re: Carbon Fiber Masts [Re: ] #102488
04/02/07 09:09 AM
04/02/07 09:09 AM
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LA
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I've seen the majority of A-cat mast failures occur in a downwind capsize and typically if the downhaul is still on tight. We always tell new A-cat sailors to be sure they ease some downhaul tension downwind in heavy air. This takes some of the compression loading out of the mast which seems to make it vunerable to breakage if you flip over. Other than that scenario, the masts seem pretty durable and reliable. In 7 years of racing in the class, I've yet to break a mast (knock on carbon!).

The most durable carbon mast I have seen is the Riba section made for the Bimare F-18HT. I've never seen one break and I've had some pretty violent flips in that boat and the mast seemed to take it all well.

Bob Hodges
A-Class USA 230

Re: Carbon Fiber Masts [Re: Acat230] #102489
04/02/07 09:29 AM
04/02/07 09:29 AM
Joined: Jun 2001
Posts: 160
Connecticut
Eric Anderson Offline
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Eric Anderson  Offline
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Connecticut
Masts.

I am certainly not an expert on mast construction, but I have observed quite a few failures of masts, aluminum as well as carbon, on Hobies, Nacra’s, Supercats, Darts, Tiapans, A cats etc as well as a lot of iceboat masts. All masts will break if used incorrectly, abused or pushed beyond the design limits. Masts seem to fail for several major reasons. A common way is fitting failure. I.e. a diamond wire becomes unattached or breaks under load and the mast breaks. This has cost me 2 aluminum masts.

The mast actually breaks in compression not in tension. Generally speaking it is a buckling problem. Think of an aluminum beer can empty. It is strong in compression until there is a little crease forming on one side and then the wall collapses and the can is crushed. A mast acts the same way. When the forces of compression or side loading exceed the ability of the mast to resist it, the wall compresses, buckles and breaks. In general the greater the wall thickness of a tube, the more it takes to collapse it. If you take a mast for a catamaran, to get the stiffness required takes a lot less carbon oriented in the vertical direction then Aluminum of the same mast section. The problem is then the walls of the tube are very thin and like the beer can have a big problem with buckling. If you add a lot more carbon (greater wall thickness) to resist buckling it becomes way to stiff. The answer it to use a lot of unidirectional carbon fiber oriented around the mast. (90° to the long axis of the mast) This increases the hoop strength (resistance to buckling) of the mast without increasing stiffness.

The other part of the equation is increasing compression strength by manufacturing method. If you go from hand layup to vacuum bagging you gain quite a bit in compressing strength because the fibers are more compact, (straighter) and there are fewer tiny voids in the laminate that can cause micro buckling which breaks individual fibers, cascading into total failure. Modern building uses fibers that are preimpregnated with the correct epoxy ratio prior to use. These materials are laid out on the tool one layer at a time and smoothed, they are then put in a vacuum bag and placed in an autoclave where they are cured at higher temps ~ 120°C with about 6 atmospheres of pressure on the bag. When this cures the fibers have much less small voids and are straighter then if it was done with conventional vacuum bagging. This gives much better compression strength, as much as 30% compared to vacuum bagging.

Now the more material you put into hoop strength, the heavier it weights. Now the trade off is weight for strength. Each group makes there own decisions as to what is reasonable. A class masts are very light, but will break if they are dropped in the parking lot while rigging, if you run into the mast while trailering or if the boat blows over on the beach. On the water mast failures are fairly infrequent. The only ones I have observed were from pitch poles where the diamond wires and downhaul were cranked on i.e. big compression loads and then big impact as the mast hits the water (think lever arm). I don’t think I want to sail a boat where the mast can’t be broken if pushed hard enough. The question is what failure rate is acceptable?
Cheers,
Eric

Re: Carbon Fiber Masts [Re: Acat230] #102490
04/02/07 09:52 AM
04/02/07 09:52 AM
Joined: Aug 2005
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Michigan
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Quote
I've seen the majority of A-cat mast failures occur in a downwind capsize and typically if the downhaul is still on tight. We always tell new A-cat sailors to be sure they ease some downhaul tension downwind in heavy air. This takes some of the compression loading out of the mast which seems to make it vunerable to breakage if you flip over. Other than that scenario, the masts seem pretty durable and reliable. In 7 years of racing in the class, I've yet to break a mast (knock on carbon!).

The most durable carbon mast I have seen is the Riba section made for the Bimare F-18HT. I've never seen one break and I've had some pretty violent flips in that boat and the mast seemed to take it all well.

Bob Hodges
A-Class USA 230


I have heard the same about the Riba mast on the HT.. but I don't want to say it out loud <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
BUT.. could this be!!!! A statement about how strong part of the HT is!!!

Chip on my shoulder,
pp

Re: Carbon Fiber Masts [Re: PTP] #102491
04/02/07 10:53 AM
04/02/07 10:53 AM
Joined: Oct 2001
Posts: 395
LA
Acat230 Offline
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LA
In my experience with the HT, the foils seemed to be the weak links (we broke one rudder and one daggerboard in 18 months of sailing). The platform and mast were reliable and strong and we did push the boat hard.

Bob Hodges

Re: Carbon Fiber Masts [Re: Acat230] #102492
04/02/07 08:15 PM
04/02/07 08:15 PM
Joined: Oct 2003
Posts: 63
jdaf31r Offline
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I was thinking the weak link is the stupid little double gudgeons, broke 2 in a year. Thankfully no broken boards.

Jon


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