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Do Masts Degrade with time?
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DanWeiss



Joined: 24 Jun 2008
Posts: 1933
Location: Connecticut, USA

PostPosted: Sat Apr 13, 2013 8:59 pm    Post subject: Reply with quote



This chart illustrates the wide variety of carbon fibers in the market. Note that high tensile modulus is almost inversely proportional to tensile strength. As the fibers become higher modulus, they also tend to become less strong and less stiff. Modulus is a measure of elasticity as I understand it, and commonly mistaken as a measure of stiffness. Stiffness is more a function of the matrix used when assembling a resin-fiber laminate -how the resin/epoxy bonds to the fibers and how the carbon fibers align to the forces applied

As we've seen most racing masts use high-mod fiber, we can expect and do see that they are less strong and will fail with less force applied than masts with different lamination matrices. I suspect this has much to do with a compromise between making a mast sufficiently elastic (high mod) and sufficiently sting but not too heavy. And not too expensive.

Carbon fiber masts will fail just as any mast if the matrix fails. Simply using a modern carbon mast (cycling it in and out of column) should not show a marked drop in breakage resistance, nor a meaningful drop in performance. But any damage to the matrix may either individually or in concert with other damage, cause the mast to fail.

UV degradation of the epoxy is one way to damage the matrix. Dropping it on a rock and point loading are others.

Sitting inside a bag, inside a shop, a mast will not "age" of loose any noticeable strength or performance unless damaged by impact or fire or something.

As for bikes, they must not only deal with moving in and out of column but point loading and torsional forces. And, making a bike frame has more in common with making a boom than a mast.

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GURGLETROUSERS



Joined: 30 Dec 2009
Posts: 1336

PostPosted: Sun Apr 14, 2013 4:06 am    Post subject: Reply with quote

Thanks Dan. I believe my bike is T 700 carbon .

As an aside, it has been claimed that fibre glass hulled yachts moored and sailed only in fresh water will suffer hull weakening over time, owing to the resins being leeched out of the hull. (A form of osmosis.) Those sailed in the sea are unaffected.

Does the same apply to the resins used in carbon masts?
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U2U2U2



Joined: 06 Jul 2001
Posts: 3056
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun Apr 14, 2013 2:35 pm    Post subject: Reply with quote

what I find amazing on this is how quickly the boat sinks

http://www.youtube.com/watch?v=8Yau9A7XDHs

some carbon here..? lot of

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DanWeiss



Joined: 24 Jun 2008
Posts: 1933
Location: Connecticut, USA

PostPosted: Sun Apr 14, 2013 5:39 pm    Post subject: Reply with quote

Leeching is inherent in underwater applications using one of the types of epoxy curing agents called amine. Amine curing agents will "blush" during cure when done in the presence of humidity, creating a waxy surface and leeching out toxins. Nasty stuff.

Modern epoxy curing agents that don't blush easily tend to be less UV stable and therefore yellow naturally. West System and System 3 exhibit this, so it's very common to paint on the outside surface of a windsurfer lamination rather than under it like polyester resin/"glass" boards.

The best stuff doesn't blush and doesn't yellow, but it won't fully cure at room temperature. That's the stuff for autoclave ovens and maybe the stuff in many iterations of pre-prey cloth?

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mat-ty



Joined: 07 Jul 2007
Posts: 1065

PostPosted: Mon Apr 15, 2013 6:37 am    Post subject: Reply with quote

I remember a carbon fiber tail snapped off a plane over a NYC suburb about ten years ago. Something about extreme turbulance from the vortex of a previous plane. It will be interestng to see how the Dreamliner holds up.
I have always bought 70 to 100 percent carbon mast and have never broke one. I think in the end go with the brand that has a proven history of quality. Take good care of it , use a mast protector or make sure to keep your boom connection super clean, and do not over tighten your mast clamp.
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