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Title: Broken shroud - Avoiding the problem Post by: Ken Smith on January 01, 2007, 09:23:33 AM The set up:
Side shrouds are fastened to a flat plate hound or a longer hound extender. The shrouds have nice swaged end fittings with forks at the end. The fork on the end is pinned directly to the hound. The problem: When the mast rotates, the lee shroud relaxes and is bent. When you tack, the tension comes back on, and the bend is concentrated right at the end of the swage. The wire starts to accumulate high-stress fatigue cycles. Finally, it breaks a few strands then the wire parts. Peter Haeper experienced this at the Western Challenge. Many have seen or will see this problem. Been there, done that. :o The solution: A fitting needs to be present to alllow the shroud to remain straight. You won't see this problem with a swage-lock eye because a shakle is present in the system. [Shackles introduce another failure mode, the lost-pin phenomena). In standing riging, I personally avoid anything threaded... Choices: http://www.bosunsupplies.com/images/168-0.jpg www.bosunsupplies.com part S0168-0006 (about $6) is a toggle that is a male and female fitting. The the male fastens to teh shroud fork, and the female to the hound. The two pins pivot axes are 90 degrees apart so the toggle lets the shroud stay straight. http://www.bosunsupplies.com/images/0737-0.jpg Next time you are making shrouds, the same company sells a swaged marine toggle, part number S0737-005 (3/16 wire, 3/16 pin) $20 or S037-007 (1/4 inch wire, 1/4 inch pin) $38 that would have the toggle part of the shroud. OR Wicks Aircraft Hardware. www.wicksaircraft.com http://www.wicksaircraft.com/catalog/images/thumb/2405_t.jpg CABLE SHACKLE DR3/16 ( AN115-21 ) - - Shackles listed are cadmium plated steel. ... Our Price: $10.29 CABLE SHACKLE 1/4 X 7/16 ( AN115-32 ) - - Shackles listed are cadmium plated steel. ... Our Price: $18.90 These shackles use pins, and are designed to handle loads up to the rating of the cable. To avoid dropping the rig in the middle of a race, renew the pins in the forestay before a big regatta and ensure your side shrods are not fatigued at their top fiting. Reliablity in the rigging.... ;) Ken Title: Re: Broken shroud - Avoiding the problem Post by: DN 805 on January 03, 2007, 07:17:26 AM Ken has accurately described the cause of rigging failure at a swadge fitting that has no universal joint in the system.
When we swadge DN rigging at Sailing Specialists, if the sailor is using a wide or flat hound triangle fitting, we swadge on a Hayn toggle fork at the top end of each side shroud. The cost is the same as the regular aircraft fork that has been customarily used at the top end of the rigging. We discount swadged rigging prices for DN sailors. I will be happy to email the DN parts list to anyone who is interested. My email is sailing19@charter.net Jane Pegel DN 805 Title: Re: Broken shroud - Avoiding the problem Post by: DN 805 on January 03, 2007, 07:43:21 AM With respect to the fork at the top end of the side shroud, I must amend my terminology. It is a Hayn RIGGING EYE TOGGLE. This is a swadge fitting that is a a toggle fork with a universal joint. Really slick.
...Jane Pegel Title: Re: Broken shroud - Avoiding the problem Post by: T Thieler US 5224 on April 11, 2007, 07:56:37 PM Another way to avoid the broken shroud issue is to try one of the T-Hound / spreader bar / mast rotator fittings that Eben Whitcomb and I have developed. You may have seen mine in action on DN 5224 (the neon yellow boat at the 2007 Worlds).
There are a number of makes and models in use but if I may say so, these things are pretty sweet. They all but eliminate mast inversions, are very clean aerodynamically and allow full articulation at the shroud attachment, thus minimizing the risk of broken shrouds. We have them for sale- Call or email for pics and price! t_thieler@yahoo.com 401-258-6230 Think Ice, T. Thieler |