Stainless bottle screws Vs Dyneema

That's exactly my point but I had intended using plastic tubing to cover and protect against UV damage , that way I can slide the tube clear to allow for regular inspection , and if there's any damage it can be replaced in seconds . If a bottle screw goes along the line of a hairline crack it just snaps , no warning and you'll be lucky if you can see the crack developing

Another point I'm thinking about is the possibility of losing the mast . Very unlikely to happen I know , but if it did go , how long would it take to cut the rigging free ?
With bottle screws ?
With this stuff I can cut the rigging clear in seconds which could make a big difference on a little boat
 
"With this stuff I can cut the rigging clear in seconds which could make a big difference on a little boat "

That's a good point that hadn't occurred to me. It would make an even bigger difference on a bigger boat I would have thought.
 
The TSYT brig Stavros is around 50m long and 500 tonnes displacement, and her very tall steel masts have very stout wire shrouds with loops and deadeyes in the lower ends - these are secured to the chain plates with rope lashings, and then the ends of the ropes are simply secured by seizings.
These rope lashings are probably about 30 mm diameter - I will take a photo or two when the brig returns here next weekend at the end of her current youth voyage.
 
Well it certainly sounds to me like it's a go though I'll be very interested in the photo's from Bajan , the more I think about it the more sense it makes . I wonder how many others will re-think previously long held convictions ?
Even if one of them does break , how long would it take to remove the broken parts of a bottle screw , locate the replacement that you were sure was in that locker , and install it to full tension , compared to grabbing a length of this stuff and fitting it . Makes sense to me
 
As someone who has a lot to do with dyneemas, spectras, and so on I wouldn't rush into removing my rigging screws.

Spectra lashing is more fragile than a rigging screw, won't last as long, cost more done properly and will not allow real fine tuning of your rig. It is also very possible you will see and get no warning of an impending failure.

Yes it is used by many top line race boats but then they swap it out often and spend a lot of money doing it right.

I use fancy fibres extensively on my boat, 3mm headsail sheets and so on but I'm staying with my rigging screws for the time being. The technology is out there but still costly and has reliability issues.
 
The trouble with dynema and similar materials is that they must be curved round quite a large radius otherwise the internal fibre strands will just break.

Even when using normal rope for rigging on older style ships fairly large bullseyes are used.

It also does not articulate like a toggle without wearing very quickly.

Whilst yes, dynema will be easily strong enough to hold the mast up in the static condition. I would be quite concerned if using it when actually sailing.

I sugest you look very closely at the reduction of strength when it is set around a tight radius.

Whilst it is fine on racing yachts on which much of the rigging is replaced on a regular basis I would not expect kevlar to have anything like the life of bottlescrews.

I am not saying don't try it (anything that can save money is a great idea) but look at all the potential problems first.

For example - what would your insurance say in the event of loosing a mast?

If it was at all viable all the mass builders would be throwing out bottlescrews and replacing them with kevlar and none of them do why?

In spite of what I have said when I was rebuilding my gaff rigged one rater many years ago I did use several loops of rope instead of turnbuckles on the standing rigging but the rope I was using was capable of bending over quite tight radii with little loss of strength.

Iain
 
"If it was at all viable all the mass builders would be throwing out bottlescrews and replacing them with kevlar and none of them do why?"

That's a red herring IMO - lots of things are viable but inertia and conservatism are widespread in the sailing world. I'm not saying that isn't right regarding the present topic, but it is also viable to build boats whose keels don't fall off, whose shaft seals are easily accessible, whose anchors store and deploy easily, whose cockpits are secure and comfortable, whose deck fittings can be accessed from beneath etc etc.
 
Just to be clear on this
The bottle screws I have are totally unusable so I'm not suggesting that everyone removes good ones just to use dyneema
Mine is a relatively small boat and is not in any way ever going to race unless anyone considers 4knots max to be a racing speed , so the tension on the rigging isn't going to be that critical , or even that tight , and I do intend curving rather than bending the lines
However , if I do lose the mast I think insurance is going to be the last thing on my mind
 
From Sailing by E. F. Knight

The shroud lanyards are of rope, but are not long enough to give sufficient play by stretching; however, they do give some hfe and spring to the rigging, whereas the iron screws with which the shrouds on some small yachts are set up cannot give and take in the least, must strain the boat, and seem to us wholly objectionable, though they do save some labour to an indolent mariner.

To set up a shroud, get it taut with a watch tackle (see Fig. 12) — the smallest yacht ought to carry at least one watch tackle, or "handy billy," as sailors call it; it is useful for a variety of odd jobs — then reeve the lanyards through the dead-eyes and make the ends fast.

When a yacht is under way in a fresh breeze the weather shrouds are very taut and the lee shrouds slack. So the lee shrouds can easily be set up by hand, and when the vessel has gone about on the other tack the other shrouds will become the slack ones and can be set up in the same manner.
 
To echo and expand on GMac's post:

IMHO any rope lashing in place of a metal turnbuckle is only a viable alternative if you are prepared to spend more time on inspection / maintenance, and have the skills to do it right.

Top end race boats use lashings because they are lighter, and they are saving ounces everywhere they can. The trade off is using a material that is more prone to certain types of failures (e.g. abrasion, cutting) and requires more frequent replacement (apparently by skilled fitters - I wasn't aware of this). Dyneema and other fibres may be stronger than steel, but that doesn't mean they can replace steel in all applications.

Compare with a bottlescrew, which is very nearly "fit and forget". When I was racing big boats we would do a full rig check after every race, but in the cruising world annual inspections are the norm and probably fine. Insurers will probably insist on replacement of standing rigging after about 10 years, so the risks of failure of a bottlescrew (even one that has never been inspected or maintained) are probably pretty low.

As I see it, the only comparative advantages of using Dyneema are (1) its low weight - probably not an issue for most club racers, let alone cruisers, and (2) possibly, the ability to cut the rig away in a dismasting (and with this one, I am not entirely convinced that it would be so easy to cut through several turns of loose rope).

OTOH, the disadvantages are: (1) more susceptible to environmental damage, (2) more frequent inspection regime, (3) more frequent replacement, (4) higher skill needed for replacement, (5) more difficult to adjust.

For me the balance stays with bottlescrews.
 
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