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-   -   Minimum reasonable breaking load for forestay of 31' ketch? (http://www.sailnet.com/forums/gear-maintenance/101924-minimum-reasonable-breaking-load-forestay-31-ketch.html)

rhumbunctious 07-29-2013 11:42 AM

Minimum reasonable breaking load for forestay of 31' ketch?
 
Last year I replaced all the rigging on my '79 Westerly Berwick ketch, including a roller furler system that works with hank-on sails. It basically is a pair of barrel swivels with a drum which is attached as part of the forestay, so that the entire forestay rotates when furling the sail.

http://rullfock.se/bilder/CU%2013%20Big28.jpg

The main mast rigging, which is an exact copy of the original rigging, aside from the furler, has a breaking load of 3500kg but the furler has a breaking load of only 2700kg. The manufacturer assures me that it is more than strong enough for the boat, but I can't stop worrying anytime the wind picks up whether I'm going to lose my forestay.

Am I worrying needlessly? What is a minimum reasonable breaking load for a forestay for this size of ketch?

chucklesR 07-29-2013 12:02 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
You can pretty easily look up the breaking load of the original forestay -

Wire Rope (Trawl Rope) - Galvanized, Bright, Stainless, IWRC, Fillerwire & Rotation Resistant | WorldWide Enterprises, Inc.

Stainless Steel Marine Rigging Wire Ropes - Loos & Co., Inc.

My guess, the original was 7/16 inch.

Wire Rope - Strength

overbored 07-29-2013 12:08 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
7/16" on a 32' boat? no. 1/4" would be used on most boat that size. 2700kg is a bit should be ok. if you have 5/16" then it would be a bit light. I have a 33" racer and the forestay is 3600 kg breaking strength. and a lot more sail area on the main mast then a Berwick

rhumbunctious 07-29-2013 12:17 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
Previous and current wire for main mast is 1/4 inch wire with 3/8 inch clevis pins.

rhumbunctious 07-29-2013 12:24 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
Quote:

Originally Posted by overbored (Post 1066003)
7/16" on a 32' boat? no. 1/4" would be used on most boat that size. 2700kg is a bit should be ok. if you have 5/16" then it would be a bit light

The clevis pins used in the roller furler are 5/16" (8mm). I don't know if there would be any benefit (or even drawback) to drilling those holes out to accommodate 3/8" (9.5mm) clevis pins.

All the other rigging components and connections, such as the turnbuckle and including the holes at the top of the furler drum, accomodate 3/8" clevis pins...

rhumbunctious 07-29-2013 12:44 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
Quote:

Originally Posted by chucklesR (Post 1066001)
You can pretty easily look up the breaking load of the original forestay -

...

Stainless Steel Marine Rigging Wire Ropes - Loos & Co., Inc.

...

Well, according to the Loos site, 1/4" 1x19 316 stainless (which is what I have) has a breaking strength of 6900lbs which is 3130kg, so that's not too far off from 2700kg. Not sure how much that 430kg difference makes in practice...

Wouldn't the crimped terminals have a lower breaking strength than the wire itself? I.e. the actual crimping?

overbored 07-29-2013 02:08 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
both swaged and nicro press ends are rated at 100 % of the wire

rhumbunctious 07-29-2013 02:11 PM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
Quote:

Originally Posted by overbored (Post 1066065)
both swaged and nicro press ends are rated at 100 % of the wire

OK, so the question then remains whether that 430kg difference in breaking strength has any practical significance such that I should be worried in heavy weather....

zz4gta 08-02-2013 11:29 AM

Re: Minimum reasonable breaking load for forestay of 31' ketch?
 
Man there are a lot of potential failure points on that thing...


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