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  #1  
Old 11-13-2013
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Replacing forestay wire with dyneema?

My forestay broke a few weeks ago though the jib stayed in place and I was able to keep sailing, which is the beauty of a free-standing rig. I jury rigged it for a while and took it down this weekend to get a new one built. Now I'm wondering if I should replace it with the same wire or go with Dyneema or other such rope. Dyneema has higher breaking strength, but I assume it won't last as long because of UV exposure so would need to be replaced/maintained more often. What is the consensus on this for rigging?
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Re: Replacing forestay wire with dyneema?

Dyneema generally is not sutable for standing rigging. It has too much stretch and creep, as well as requiring larger sizes to try and compensate for these.

An annealed form of dyneema called Dynex Dux is being used for standing rigging, though I don't think for forestays under roller furling. Unlike wire it must be sized for creep control not breaking strength, so significantly stronger Dux is typically specified relative to the wire it replaces.

John Frapta at Colligio Marine or Brion Toss would be the ones I would call if I was considering taking this approach. Luckily my Corsair uses Dux from the factory, so I didn't have to figure out the details myself.

As for UV. The expected life span is about 8 years for the line, which is relatively easy to replace when needed. The fittings are reusable for pretty much ever since they are anodized aluminium.
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Re: Replacing forestay wire with dyneema?

You might want to contact New England Rigging in concord, MA. A year ago I lost my forestay on my F38. He made up a replacement. At the time we discussed a dyneema alternative which he had said he had used in similar applications and recommended if I again lost this replacement due to the stresses placed on the bottom fitting by the camber spar, at least in my case.

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Re: Replacing forestay wire with dyneema?

I would imagine the fact that the F38 has a free standing spar and the forestay isn't your typical rig support would put a different spin on the dyneema question...
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Re: Replacing forestay wire with dyneema?

Quote:
Originally Posted by ereiss View Post
You might want to contact New England Rigging in concord, MA. A year ago I lost my forestay on my F38. He made up a replacement. At the time we discussed a dyneema alternative which he had said he had used in similar applications and recommended if I again lost this replacement due to the stresses placed on the bottom fitting by the camber spar, at least in my case.

Regards
Yeah, that metal to metal rubbing has been a disturbing feature. I'll ask about chafe, too. Thanks to all for the suggestions. At least now I know where to start and perhaps be asking the right things.
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Re: Replacing forestay wire with dyneema?

if the forestay broke it must have tension on it. on a freestanding mast the forestay is to support the jib and the only way to change the luff curve is to tighten up on the mainsheet . when beating to weather the forestay will have the same load on it as a stayed rig
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Re: Replacing forestay wire with dyneema?

Quote:
Originally Posted by gamayun View Post
Yeah, that metal to metal rubbing has been a disturbing feature. I'll ask about chafe, too. Thanks to all for the suggestions. At least now I know where to start and perhaps be asking the right things.
Chafe can be solved by using soft shackles to attach the jib instead of bronze hanks.

You will find lots of info at this link: Colligo Marine - Rigging reduced to its elegant essentials. - Colligo Marine - Synthetic Rigging
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Old 11-14-2013
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Re: Replacing forestay wire with dyneema?

After discussing this with 2 riggers, I decided to stay with wire. The extra cost, half life, stretch features, extra chafe potential, etc., of the synthetic don't make it the best choice for the forestay.
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Re: Replacing forestay wire with dyneema?

Quote:
Originally Posted by overbored View Post
if the forestay broke it must have tension on it. on a freestanding mast the forestay is to support the jib and the only way to change the luff curve is to tighten up on the mainsheet . when beating to weather the forestay will have the same load on it as a stayed rig
I've read this several times and the mechanics of it seem correct, but I'm not sure how much mainsheet tension matters in the luff or even in the jib overall on a Freedom rig. When the forestay broke, the hanked on jib kept sailing in 17 knots of wind although when we were head-to-wind on the tacks, the jib was "shaky" and the luff seemed loose. It wasn't until I saw the forestay wire dangling off to one side that we figured out what was going on. I guess if we had gone downwind, the illusion of stability in the jib might have failed, but the jib doesn't do much for me downwind anyway. So when everything is working on a beat to weather, tightening the mainsheet doesn't seem to make much difference on the jib configuration. I'll pay better attention to that next time and try to see if it does. I am still (and probably for a long time yet) trying to figure out how this boat sails at its optimum.
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