Cruisers Forum
 


Join CruisersForum Today

Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 12-01-2019, 16:03   #31
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 5,669
Re: Racing sailor killed due to splice failure

72:1 is the gold standard. With a brummel or good stitching, about 40:1 has proven 100% strength.


Remember that these preventers are attached end-of-boom; snapping the boom isn't really a risk... but I'm not arguing pro-con on the issue. That said, no engineering number was presented, which should be case if it was a designed fuse (electrical fuses are not selected at random). If you are claiming something was a "fuse," you should be able to show, with calculations, how the value was chosen.



And you must train the crew not to loiter in the path of the traveler. That was another of the MAIB findings. But could there have been anyone on the boat that didn't already know that? If so, the crew screening process is nonexistent. And it's not the kind of thing an experienced sailor forgets either. It is ...basic and obvious.
__________________

__________________
Gear Testing--Engineering--Sailing
http://sail-delmarva.blogspot.com/
thinwater is offline   Reply With Quote
Old 12-01-2019, 16:08   #32
Registered User

Join Date: Mar 2016
Posts: 76
Re: Racing sailor killed due to splice failure

Why is the taper necessary? It seems like tapering would make the bury more likely to slip, and so one would need to make the bury longer to compensate.
__________________

Caddy Shack is offline   Reply With Quote
Old 12-01-2019, 16:08   #33
Registered User
 
Training Wheels's Avatar

Join Date: Aug 2014
Location: Left coast.
Posts: 939
Re: Racing sailor killed due to splice failure

I’d think there’d be more chance of damaging the boom or gooseneck with the hard slam shortly after the preventer parting. Perhaps if your using the preventer strictly as a preventer, and not to stop the boom from moving around, a line with some stretch would be better.
Training Wheels is offline   Reply With Quote
Old 12-01-2019, 16:19   #34
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2005
Location: Bellingham
Boat: Outbound 44
Posts: 6,389
Re: Racing sailor killed due to splice failure

Quote:
Originally Posted by Caddy Shack View Post
Why is the taper necessary? It seems like tapering would make the bury more likely to slip, and so one would need to make the bury longer to compensate.
With no taper the outer strands make a sharp turn. Since they don't stertch the forces are focused on individual strands. The splice will be weak at the sharp transition.
Paul L is offline   Reply With Quote
Old 12-01-2019, 21:34   #35
Registered User

Join Date: Mar 2009
Location: Southern Chesapeake Bay
Boat: Norseman 430, Jabberwock
Posts: 833
Re: Racing sailor killed due to splice failure

Paul, thanks for the photo of what the "before" would've looked like. That's what I had suspected, but when it was termed a "splice", I ruled it out, because as others have mentioned, that isn't a splice.

Regarding the mechanics of the Dyneema splice, I cut apart a splice I had made years before, and was impressed with what I found. The uniform taper was almost rock hard and completely covered by hard, sharp little bumps made by the pressure from the braided (of course) outer cover. It would even say it was beautiful. Cover and core were virtually locked together.
ggray is offline   Reply With Quote
Old 13-01-2019, 08:05   #36
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: The boat: Cowes (Winter), Above 60N (Summer); me: somewhere in the air!
Boat: Cutter-Rigged Moody 54
Posts: 22,902
Re: Racing sailor killed due to splice failure

Quote:
Originally Posted by thinwater View Post
. . . And you must train the crew not to loiter in the path of the traveler. That was another of the MAIB findings. But could there have been anyone on the boat that didn't already know that? If so, the crew screening process is nonexistent. And it's not the kind of thing an experienced sailor forgets either. It is ...basic and obvious.

Another useful habit is to lock the traveler down from both sides -- don't leave the lazy side uncleated or off the winch. I am amazed at how often I see this being done.




As to preventers being "fuses" -- I don't think anyone knows how much force their preventers can take, and I am under no illusions whatsoever about mine.


What people forget about is the GEOMETRY. What angle is your preventer at, to the boom? Do you know what the multiplier factor is, for that angle? I think in many cases, especially for boats with aft swept spreaders, like mine, which keep you from getting the boom that far out, it's going to be 5:1 or more, so just 1 tonne of force will put 5 tonnes on the preventer, say.


I don't have any illusions about my preventers surviving any kind of snatch load, so I am very careful to keep them tight at all times. If the boom end kisses the water, I figure there will be mayhem. Fortunately it's hard to touch the boom to the water on my boat as the aft-swept spreader keep the boom from going out very far, and the boom anyway is more than 2 metres above the water. The boom is 6 meters long and the beam of the boat there is almost 5 meters, so I would need to be nearly knocked down, or caught by some really weird wave. YMMV.
__________________
"Parce que je suis heureux en mer, et peut-ętre pour sauver mon ame. . . "
Dockhead is offline   Reply With Quote
Old 13-01-2019, 22:36   #37
Registered User

Join Date: Aug 2007
Location: Adelaide, South Australia, sailing in the Med.
Boat: Beneteau, Oceanis 50
Posts: 532
Re: Racing sailor killed due to splice failure

Quote:
Originally Posted by rmlarson1098 View Post
Sir Robin? As in Robin Knox-Johnston? Sir Robin had nothing to do with this tragedy, unless perhaps he was the captain of the vessel. Which he was not. It wasn't Knox-Johnston's race, and even if it were the ultimate responsibility rests with the skipper. Ocean sailing is dangerous, ocean racing ridiculously so. Sir Robin is a legend, as he should be. No one had ever done what he did - which MANY people felt was impossible - and no one else ever will. Leave him alone.
HEAR, HEAR !
__________________

David B is offline   Reply With Quote
Reply

Tags
racing, sail

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hunter sinks at Catalina due to bow cleat failure autumnbreeze27 Monohull Sailboats 550 11-04-2016 22:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:14.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.