Lloyd:
From what I have read it’s not that Carbon Fiber masts are more susceptible to lightning strikes it’s that the lightning strikes are more devastating to carbon fiber. As I recall the reasoning is this. Both Aluminum and Carbon fiber mast are conductors. Both will provide electrical paths to the ground/water in a lightning strike (in a properly grounded boat). It just that aluminum is a much better conductor i.e less resistance. Less resistance to electron flow equals less heat. Carbon Fiber is not as good. Soooo there is more heat built up in a lightning strike in the carbon fiber material. Which tries to expand because of the heat induced by the strike but can’t do it fast enough so it shatters and/or cracks. The danger is not when the Carbon Fiber shatters as it should be obvious from the pieces of mast on the deck, It is if it only cracks The damage may not be seen because it is hidden behind the coating applied to the Carbon Fiber masts to protect them from UV rays. Failure of the mast can come at anytime after that with no indication before hand.
Mike
BIANKA
1986 30U
— On Thu, 6/11/09, Lloyd Robbins lrobbins@QTRLAW.COM wrote:
> From: Lloyd Robbins lrobbins@QTRLAW.COM
> Subject: Re: Nonsuch Luck de-masted
> To: NONSUCH-L@LISTSERV.AOL.COM
> Date: Thursday, June 11, 2009, 4:36 PM
>
> Thank you for the photos of the mast. . You should challenge your insurer . As a lawyer who deals with insurance claims I would not accept their position. These masts do not fail as a result of ordinary wear and tear. Insurance companies always start with this position .
>
> I have an older nonsuch . I do not have a mast collar . I have a fitting which is riveted onto the mast. I have been thinking of getting a mast caller but after looking at your pictures I wonder if the collar does not actually make a greater stress point. Are there any experts that can comment on this.
>
> Instead of having a collar could a fitting be bolted through deck sepreate from mast or would that cause too much strain on the deck.
>
> I once was considering getting a carbon mast. I talked to a rigger friend who has considerable experience and his one comment was that the carbon mast was more susceptible to lightening . Can anyone comment.
>
> —
>
> From: Nonsuch Yacht Owners Discussion List [mailto:NONSUCH-L@LISTSERV.AOL.COM] On Behalf Of John Newell
> Sent: Thursday, June 11, 2009 10:32 AM
> To: NONSUCH-L@LISTSERV.AOL.COM
> Subject: Re: Nonsuch Luck de-masted
>
> Bob,
>
> I guess part of the cause from looking at your excellent photos is that salt accumulated below the collar over the years permitted electrolosis to reduced the strength of the aluminium below the collar giving you a clean break at that point. Being close hauled would exert stress at the base of the mast and the time for a weakened mast to break. Those who tend to over sheet risk premature mast failure apart from sailing on one’s beams end at reduced speed and increased leeway.
>
> If I am right, it would be a good idea for the Nonsuch fleet to ensure the mast is washed thoroughly below the collar and a protective coating applied on a regular basis especially when sailing in salt water. Rain will wash the mast down to the collar but brine will accumulate under it. If I am wrong, washing below the collar will do no harm.
>
> Replacing the mast with a carbon fibre spar as you suggest seems to be the logical thing to do in salt water. I hope the US manufacturer can give you a good price. Exchange rates should work in your favour, but I doubt that they could supply you with a replacement mast in time for the Around the Island Race. It would not hurt to ask for your money back or at least allow you to enter next years race. Seems only fair.
>
> John
>
> > ----- Original Message -----
> >
> > From: Bob Illingworth
> >
> > To: John Newell
> >
> > Sent: Thursday, June 11, 2009 5:31 AM
> >
> > Subject: Re: Nonsuch Luck de-masted
> >
> > John,
> >
> > Thanks for your message; we were well sheeted in so the end of boom would have been immediately above the starboard aft rail.
> >
> > Bob
> >
> > From: John Newell
> >
> > Sent: Thursday, June 11, 2009 1:40 AM
> >
> > To: Bob Illingworth
> >
> > Subject: Re: Nonsuch Luck de-masted
> >
> > Bob, I am so sorry to hear it and just before your big event. Bad Luck…
|
very in depth discussion of happy decision to fit bluewater cruiser with a carbon rig from Hall: includes a detailed argument on lightning from Ben Hall. This particular owner did a very thorough refit and felt that the new carbon stick was the best thing he did:
http://www.morganscloud.com/indepth/inbrpart1.html#lightning
A carbon stick from a builder like Hall or Composite is an excellent choice. While you are at it get them to make you carbon wishbones.
Mike I love your electric engine. If you ever want to sell your boat let me know.
Joe Thompson NS26U “Cato”
Mike is correct.
In a tragic example some years back, a manufacturer of helicopters leasing
rotary wing aircraft to a British aviation company servicing the North Sea
oil rigs upgraded the tail rotors on their choppers from magnesium aluminium
alloy to carbon fibre in a sincere effort to improve tail rotor performance.
They had done all that was required, tests and so forth, to meet stringent
FAA code including how carbon fibre would perform with a lightning strike.
Unfortunately they underestimated the power of a maximum strike. Eventually
Murphy's Law prevailed. In very inclement weather one day some many miles
North of Aberdeen, a helicopter ran into a storm, and the tail rotor was
struck with a particularly powerful bolt. The result was the rotor shattered
as it could not dissipate the heat, the aircraft lost stability and its fate
was sealed. I believe they went back to metal rotors.
Carbon fibre is a very poor conductor and would not take to lightning well
at all. I think I like my metal mast!
Paul
The Enlightenment #338
Paul is not alone in his love of aluminum stick. This is why I offered an alternative to “going carbon”. I have been hit by lightning in a boat with wooden spars but a good grounding system and nothing serious happened. I have seen a number of well grounded aluminum masts that have been hit with minimal damage. On the other hand, I have a friend who shall go unnamed who is sailing right now with a carbon mast that he had to repair due to lightning strike. He is babying that stick and has noticed various irregularities which he is nervously watching.
It is really unfortunate that aluminum mast structure was not better known when the early NS’s were manufactured. As for the fleet, I think it is imperative that we start to consider a full tool kit of preventive actions of the type and even further than those recommended by the able Mr Quill. Without so doing, I am afraid that we will be reduced to being a bunch of run to carbon Chicken Littles. Not that I don’t like carbon altogether, as if truth be known and I was given a choice, I would probably choose carbon. But right now I like most in the fleet have aluminum (I have 2 of them). Just as with the splice fixes, engineering needs to be put into place to stabilize the bases where the greatest stress levels are now occurring.
Carbon has it’s own logic and that logic must be understood, as West System technical advisor for South Florida in the early 1980’s, I was in on various advanced composite materials testing by the Gougeon brothers. This and well known failures has shown me that there are weaknesses, but not among them is weight savings. Weight savings and overall reduction of stress is a major benefit, but the are prone to being fried when hit by lightning. Two other factors strike me (pun intended); 1) while very strong in tension, carbon is weak in compression and 2) when failure occurs, it is catastrophic. Net net, there is no perfect world with the exception of the one in our dreams. All materials, like man and womenkind, all have some weakness, and as the man says, “ones got to know your (or their) limitations”.
Regards to all (even the carbon loving ones amongst us),
Barry & Brigid Michaels
NS 36’ # 9 Cat Ketch “Tally-On” (One-of-a-Kind)
St. Augustine, FL