Bendy carbon masts

I'm pretty sure carbon masts lose some stiffness. It maybe just a very small amount and probably shows itself by the mast being less crisp feeling in it's responsiveness.
But with a Merlin of that age (wooden Chipstow perhaps?) I would think it's more likely to be the boat flexing and allowing rig tension to vary in turn allowing the mast to bend more. ie the shrouds and spreaders, which should be keeping the mast in the shape you want it are allowing the mast to bend as the rig tension drops when you hit a wave or get a gust etc.
Or it maybe as simple as not having enough lowers on when you apply the kicker in windier conditions...

I only know of unstayed carbon masts on Byte C2. My friend is sailing regularly with a nine year old mast including winning two championships. He is on his third boat but has retained the original mast. He is happy with the mast characteristics and sees no reason to change. 

Yes, the stiffness of a carbon composite will drop as it is fatigue cycled. If you are into this sort of thing here is a link.

http://web.ornl.gov/~webworks/cpr/v823/rpt/106099.pdf

The graph on page 57 shows how the strain ( equivivilant to deflection on a mast) changes if it is cycled at 1/2 its ultimate strength. After 10,000 cycles ithe strain goes from 0.8 to 1.0 % which doesnt sound much but is a 20% increase

Interesting... I haven't studied the paper properly but I note that it says that (para 4.1) in the composite they used "fatigue is unlikely to be a problem when cyclic stresses coincide with the fiber orientation". Of course in a mast nearly all the fibres are oriented the same way and so are all the stresses.

Merlins are intrinsically not the best engineered of boats, it might be worth taking measurements to see if the hull is distorting. The trickiest, because the foredeck is in the way, but possibly most useful is across the hull midway between bow and mast. Between the shrouds is good as well of course.

Edited by JimC - 31 May 15 at 3:24pm

Originally posted by JimC Interesting... I haven't studied the paper properly but I note that it says that (para 4.1) in the composite they used "fatigue is unlikely to be a problem when cyclic stresses coincide with the fiber orientation". Of course in a mast nearly all the fibres are oriented the same way and so are all the stresses. Merlins are intrinsically not the best engineered of boats, it might be worth taking measurements to see if the hull is distorting. The trickiest, because the foredeck is in the way, but possibly most useful is across the hull midway between bow and mast. Between the shrouds is good as well of course.