Why not Spectra ?

[Joe Henderson]

Dear Brion,

How nice to have an owner with the vision and courage to break out of the wire rope standing rigging alley and allow you to explore other avenues. I am very jealous!

You are quite right. I should have written stretch or elongation instead of creep.

I did find that the nearer to the breaking load we got with the pre stressing the less creep crept into the equation. This is what I expected with constructional stretch but not with deformation of the material.
Maybe what we have been thinking of as creep, in the context of spectra, is just another manifestation of constructional stretch but at a higher percentage of breaking load.
It is a long time ago but it did occur to me that as I loaded the stuff up it seemed to give and hold in steps. Initially quite a lot of give then holding for a while then giving again as the load increased until the strain seemed to plateau as the load got to 75/80%.

All this is purely observational on my part, and I did not have the time to do a proper test and repeat and the dynamometer I was using could have had some error, so it is all open to challenge and query! not only that but the core I had to work with was not of the highest quality. ( I used to dream of getting hold of some Sampson Spectron 12!)

With some sense of frustration and in an attempt to get an idea of what was happening inside the material I left a pair of runners in the loft stressed to 80% of their break load over the christmas holidays and when I snuck back to look at them on new years day they had lost about 5% of the load and one pump on the Tirfor (about 15mm on the runners) set it back up.

In the end I was stressing the material to about 75% of the makers listed breaking load of the Spectra core, serving very tightly with Dacron V.B.cord and coating with polyurethane.

It all got a bit sobering when I thought long and hard about the consequences of a failure while my wife was putting on the serving and anyway Vectran had become available at a reasonable price so we did not have to keep scaring ourselves!

During the rigging program for the halyards on the maxi we came to the conclusion that the spectra jib halyards may have been stretching/ creeping during a beat because we were not stressing the material highly enough.

After a lot of buggering about with smaller and smaller rope which needed larger and larger covers to work in the clutches, we got rid of most of the elongation by using good old cheap, unfashionable, fragile kevlar in the straight runs and inserting spectra portions at the hounds and at the deck turning block and clutch. quite simple to do and it worked, we never broke a halyard in normal use, which probably means they were too big. The kevlar we used was actually some left over from Australia III's Fremantle A.C.campaign which was in the hundred or so assorted reels I bought when the rope makers were clearing their stock room.
I still have a reel of 12mm lurking at the back of the loft for that special job that is always just around the corner!

In regard to using vectran for drop over eyes, I wonder if inserting a short length of spectra at the top end for the eyes would be the way to go. It would mean that you wont have the ease of replacement inherent in your system, which I can see will be important with fibre shrouds, so maybe not.

Did you leave the cover on the Vectran?

Regards, Joe Henderson.

[Ian McColgin]

Ahoy gang,

It's great to see new developments.

The big question for folk like myself, who want to use things as long as possible:

Is there enough experience yet to determine how to inspect fibre stays for replacement prior to failure?

G'luck

Ian

References have been made to tightly serving the line and painting it with a polyurethane. I am supposing the serving is just to protect the line from chafe and uv, as opposed to keeping water out like with wire ?
I was planning on using a cover (common polyester braided line cover, like yales TST) over the shrouds, which after further thought will probably be of vectran as opposed to spectra.

I had considered machining some alum deadeyes so that we can get away with smaller lanyards, which I feared may split the original wooden ones...
Just as an interesting note I am planning to use harken carbo air blocks with 5/16" thick wooden cheeks to 'hide' them on the boat. probably maple for the cheeks, unless there are any other suggestions.

Thanks for the input and I will be sure to let you know how the job progresses.

[Joe Henderson]

Dear All,

I have no idea how long this tuff will last in standing rigging.

I know that fragile Kevlar lasted around the world on Rothman's runners, checkstays and upper diagonals, so who knows.

I suppose it will be up to us collectively, as a trade, to do the best job we can, try to second guess and pre-empt some of the more obvious failures and pitfalls and then back the work up with vigilant inspections when possible. Pretty much what we have all been trying to do for the past thirty or so years.

I pre-stressed and served more in an attempt to hold the elongation on the runners than any anti chafe measure.

In the end I just used Vectran in it's normal polyester cover.

I do think that service will be a good thing on fibre standing rigging. It's hard-ish exterior should guard against chafe from sheets and will let you know early if something untoward has happened to the stay. I think it is likely that you will see some distortion of the serving which will draw your attention to a potential problem. I also reckon it looks better than a bit of braided cover and it will be easier to keep ratlines in place.

I like the idea of the alloy deadeyes. We made some out of Tuphnol a while ago and they went ok. We made sure that the laminates of linen were aligned across the load paths etc. I imagine the load directions are pretty much the same as in a sheave with the pin taking the place of the lanyard etc. On the smaller stays rig we actually used some Main Marine Tuphnol sheaves and just drilled and scored some new holes for the lanyard, round off the lips of the sheave and it looks like a bought one..

The timber shelled modern block is a great idea and works really well. Lets you have all the fun of varnishing without the pain of friction-plus blocks. Our grandfathers would have used them like a shot if they had been available, same as most things.

Make sure you don't glue the block shut. You do not want to have to break the timber to dismantle and repair the block like I did. Who knew that a bit of Sika could end up costing me so much!

Regards,
Joe Henderson

[Jak Mang]

A few questions on the modern ideas for traditional boats -

Are deadeyes/lanyards used for fore and back stays as well? I don't remember seeing them on traditional boats, but I also have not been looking for that detail. If not, what method is used for adjusting tension?

Anyone have a good source for deadeyes? I'd be interested in bronze or wood.

On a related subject, I saw some nice Lewmar blocks (on Brion's handy billy) that looked like they were made to accept small screws on the outside of the body. Is there any problem using these to attach wooden cheeks? Are you guys making your own cheeks or do you have a source?

Thanks,
-jak

[Jak Mang]

Has anyone tried Spectra for bobstays? Is there any data on long term exposure to saltwater?

I'm also interested in tensioning alternatives to deadeyes for this use. Brion mentioned a horror story in a class about turnbuckle below the water line on a bobstay. Obviously, the turnbuckle should have been on the upper end. This lead to a hint that perhaps the turnbuckle could/should be eliminated all together. Is there a way to pre-calculate tension on fixed-length gangs and install them under load? This would save a lot of hardware and weight.

I apologise for the novice questions. I'm trying to immerse myself in the technology.

Thanks,
-jak

[osteoderm]

Jak,

Chafe is a major issue with bobstays. You'll often see chain bobstays where wire would suffice (strength-wise) for just this reason. Anchor rodes, floating debris, docks, dinghies, etc., will all likely be found chafing away at your bobstay at one time or another. For the same reason, i think rod bobstays are a bad idea too; with no resilience, the inevitable impacts are bound to severly stress the metal.