Mast types...? Through deck on deck...? - Page 3 - SailNet Community
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post #21 of 42 Old 01-18-2007
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Thanks for posting the photo G-. I had saved it to my computer but, as usual, couldn't get it on to a post! Now could you put the Ken Barns photo up???

I may be wrong, but I just don't see a keel stepped mast taking out a section of deck. It seems that the mast would exert lateral force on the partners during a dismasting which would be far less likely to fracture the deck than upward or downward force.
I do agree that neither options is more, or less likely to fail, if built correctly. Dismasting would be more of a failure of the rigging and chainplates than the mast itself.

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post #22 of 42 Old 01-18-2007
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I think johnsail could provide some real insight into this. I think he wrote a book on the Fastnet race. Again, we are talking extreme conditions, but I would love to hear from another expert.
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post #23 of 42 Old 01-18-2007
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I envision several mast failure modes but the most likely that I see is a stay failing and the resultant assymetrical forces breaking the mast. In this case the lateral forces on a keel stepped mast would make the failure point either the deck (if the deck is stronger on a horizontal plane than the mast) or {horror} the mast pivoting around the keel mounting point and tearing away a large chunk of the deck before {hopefully} being pulled out. This mode couldn't happen with a deck stepped mast, even after sliding off the mounting harpoint the forces would be more lateral than vertical.
look at 2 distinct failure modes - mast breaking above deck and


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post #24 of 42 Old 01-18-2007
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Quote:
Originally Posted by T34C
Thanks for posting the photo G-. I had saved it to my computer but, as usual, couldn't get it on to a post! Now could you put the Ken Barns photo up???

I may be wrong, but I just don't see a keel stepped mast taking out a section of deck. It seems that the mast would exert lateral force on the partners during a dismasting which would be far less likely to fracture the deck than upward or downward force.
I do agree that neither options is more, or less likely to fail, if built correctly. Dismasting would be more of a failure of the rigging and chainplates than the mast itself.
At your service.....

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post #25 of 42 Old 01-18-2007
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Thanks G- !!

I would guess that is typical of deck stepped mast breakage like the previous photo. The force being applied at the masthead by the halyard and having an oposing force at the lower shrouds.

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post #26 of 42 Old 01-18-2007
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I think the reason a keel stepped mast often damages the deck is that it does break higher up..and the mast falls and punches a hole through the deck where it hits. A deck-stepped mast usually breaks at the mast step and gets swept from the deck, not damaging the deck much otherwise.

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post #27 of 42 Old 01-18-2007
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Both masts on my ketch rig are deck stepped, and based upon the conclusive reasoning in this thread, I'm glad I have less potential for double trouble.

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post #28 of 42 Old 01-18-2007
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SD- I think that is a good point, but with the force on the sail I would guess the masthead is "most likely" going to fall over the side. There is the possibility that I think Jeff mentioned that the keel stepped mast wouldn't shear off or break, but bend over (fold) and need to be cut off of the stump.

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post #29 of 42 Old 01-18-2007
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OHHHH My!!!! Jesus, Mary, and Joseph!!!

Where this is going.....soon Michael Moore will be writing about this, too
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post #30 of 42 Old 01-18-2007
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I think this thread has already included more facts than MM.

Boy G- you sure know how to throw fuel on the fire!!

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