Dyneema backups for standing rigging. Why is it not done?

F

fredrussell

Well-Known Member
Joined
24 Mar 2015
Messages
4,153
Visit site
Given the huge cost of a new rig, why do boats not have backup shrouds, forestay etc made from dyneema/spectra etc?

I guess I mean lines that run parallel to standing rigging, but that are tensioned to lesser extent, and attached to either same points standing rigging attaches to or, ideally, separate mounting points. It wouldn't add a lot of weight aloft and the cost wouldn't be that much would it?

I'm not thinking of doing it, just musing really.
 
Thats a good idea,how would you stop the dyneema humming or frapping, I'm going to put this on this winters list, thanks
 
JumbleDuck said:
What about creep?
Click to expand...

Dyneema is sized for creep, not maximum breaking load.

Which could well be a downside for having loose secondary rigging made from dyneema, as there is next to no stretch in the dyneema the dynamic loads if the wire rigging goes will be colossal when the dyneema gets the load.

Good chance there will be 2 bangs instead of just one..
 
fredrussell said:
Given the huge cost of a new rig, why do boats not have backup shrouds, forestay etc made from dyneema/spectra etc?

I guess I mean lines that run parallel to standing rigging, but that are tensioned to lesser extent, and attached to either same points standing rigging attaches to or, ideally, separate mounting points. It wouldn't add a lot of weight aloft and the cost wouldn't be that much would it?

I'm not thinking of doing it, just musing really.
Click to expand...

I've had inner, intermediate and forestay break at various times. If you're a reasonably competent seaman it's unnecessary to lose the rig.
Making up special HDPE standing rigging is probably not worth the trouble as it's far too stretchy to replace wire without effective turnbuckles to tension it.
Usually one uses the main, genoa or spinnaker halyard to replace the broken, standing rigging. All my halyards have been in HDPE for the last 18 years.
 
Flica said:
I've had inner, intermediate and forestay break at various times. If you're a reasonably competent seaman it's unnecessary to lose the rig.
Making up special HDPE standing rigging is probably not worth the trouble as it's far too stretchy to replace wire without effective turnbuckles to tension it.
Usually one uses the main, genoa or spinnaker halyard to replace the broken, standing rigging. All my halyards have been in HDPE for the last 18 years.
Click to expand...

I not sure I agree with your comment "If you're a reasonably competent seaman it's unnecessary to lose the rig." if the rigging goes when the load is high there a good chance of losting the mast , no matter how good a seamen you are .
Although I won't be going through the trouble of added Dyneema to my rig.
 
GHA said:
Dyneema is sized for creep, not maximum breaking load.

Which could well be a downside for having loose secondary rigging made from dyneema, as there is next to no stretch in the dyneema the dynamic loads if the wire rigging goes will be colossal when the dyneema gets the load.

Good chance there will be 2 bangs instead of just one..
Click to expand...

Size for size, dyneema is roughly as strong as stainless steel in terms of breaking strain. but a fraction of the weight.
But, it stretches more than steel and creeps.
Depending on the application, Vectran may be better.
When all is taken into account, people are still using ss wire because generally it's right for the job. There are exceptions, but they tend not to be counting the pennies. Or looking beyond the ten year service life that ss wire seems to reliably deliver.
 
I have a keel stepped, masthead, twin parallel spreader rig now so tension is set at 10% .
The original tall rig was fractional and was set up at 15%.

Creep is a factor I admit but in my experience having used it on my race boats it only needs tweaking, (half turn) every couple of months or so during the season.
Also I'll be using super stretched SK99 not the normal SK78 or pre-stretched SK98.

Noise generally comes from the caps and inters, not so much with the lowers, baby stays.

I will use left handed thread toggles with the same bottle screws with T-terminals with smooth eyes for the mast.
 
sailaboutvic said:
I not sure I agree with your comment "If you're a reasonably competent seaman it's unnecessary to lose the rig." if the rigging goes when the load is high there a good chance of losting the mast , no matter how good a seamen you are .
Although I won't be going through the trouble of added Dyneema to my rig.
Click to expand...

Your opinion is at odds with that of two riggers with whom I've spoken.
 
Presumably it must be worth long term sailors carrying dynema as a backup because if they see a shroud begin to "strand" when away from a place where a repair can be undertaken they can at least make a temporary spare with a dynema, tensioned with a block & tackle provided they carry a hook bolt for the upper end
 
Last edited:
In our travels I've seen well over 1,000 yachts and none had back up rigging, I don't see the need for it. The only boat I saw dismasted was in Bonaire when it fell down after the boat caught fire.
 
KellysEye said:
In our travels I've seen well over 1,000 yachts and none had back up rigging, I don't see the need for it. The only boat I saw dismasted was in Bonaire when it fell down after the boat caught fire.
Click to expand...

Yes, the majority of pix I've seen of dismasted yachts are those who have fallen over whilst out of the water. Usually the result of high winds and the domino effect.
Though I have had a fatigue fracture of a keel-stepped mast, that had nothing to do with broken standing rigging but rather a design error, attempting to ape "bendy-mast" racers.
The replacement mast, worked out by the mast manufacturer, from base principles, had a 45% greater cross-sectional area but was only 9% heavier.
As Lulu said;- "masthead rigs seldom break, even if the boats don't sail well".
 
In practice you have halyards that can act as temp shrouds.
I carry dyneema on board that could be used for either not specifically shrouds.

Last year i was off Orford Ness where a Sadler 34 was struggling with a broken forestay.
The baby stay was the only thing keeping the rig from falling backwards.
They were motoring into the wind and chop whilst a poor crew member was desperately trying to control the flogging sail and forestay.
I went closer as fast as I could and screamed at them to sail downwind, which they duly did and everything became a lot easier.

Its true that rarely have I seen the wires fail on a rig.
Normally its a chainplate failure, pin's falling out or mast fitting failure and I've also seen three cast alloy mast feet that have integral halyard sheaves collapse under compression.

Compression post failures are pretty common on deck stepped rigs, had to fix two of these this year...
 
When I had my rigging changed I kept a forestry and one of the shrouds. They coil up quite well and stored away in the lazarette. I then have a load of heavy duty wire rope grips and feel that I could make a reasonable good repair if needed.

That said I have 3 forestays, 3 shrouds, 2 backstays and two duneema running back stays all on a keep stepped mast. I think it's pretty strong but a big knock down with canvass up could probably take it down.
 
GHA said:
Dyneema is sized for creep, not maximum breaking load.

Which could well be a downside for having loose secondary rigging made from dyneema, as there is next to no stretch in the dyneema the dynamic loads if the wire rigging goes will be colossal when the dyneema gets the load.

Good chance there will be 2 bangs instead of just one..
Click to expand...
I'd agree with this, the shock loads will be many times static so you'd likely just get the double bang. I've only experienced forestays going in both cases the sail kept the mast up long enough to get a halyard on the toe rail as we bore off downwind to take the load off. Inspecting rigging and not being over canvassed or avoiding sea/swell direction the pounds the boat and pumps the rig are my approach.
 
northcave said:
When I had my rigging changed I kept a forestry and one of the shrouds. They coil up quite well and stored away in the lazarette. I then have a load of heavy duty wire rope grips and feel that I could make a reasonable good repair if needed.

That said I have 3 forestays, 3 shrouds, 2 backstays and two duneema running back stays all on a keep stepped mast. I think it's pretty strong but a big knock down with canvass up could probably take it down.
Click to expand...

Rather than rope grips have you considered Stalok fittings? We carry a 12mm and a 10mm eye fitting so we can shorted a failed wire and install dyneema lashings. We have had to do this a number of years ago when a babystay failed mid Atlantic. Worked well. You just need to carry some small diameter dyneema to do the lashing. Back to the traditional sailing rig solution of square riggers
 
You must log in or register to reply here.

Share this page

Top