Stainless vs Dyneema for my boat

[leecea]

Regarding service life, Collingo Marine's FAQ is currently saying 5 years or more but they hope this goes up as they get more data.

[BBill]

Originally Posted by pbmaise

Chotu,

I went with a galvanized forestay and Crosby poured in place fittings.

I made certain the galvanized wire rope I ordered was the type that didn't have a core to attract moisture. I then soaked the entire wire in synthetic linseed oil. This provided an extra barrier coat to salt.

Wow, I grew up using galv wire and poured sockets on standing rigging...the fiber core in galvanized wire is to absorb oil and keep the wire from rusting. Otherwise you have to oil it way more often. Just sayin...

[pbmaise]

Originally Posted by BBill

Wow, I grew up using galv wire and poured sockets on standing rigging...the fiber core in galvanized wire is to absorb oil and keep the wire from rusting. Otherwise you have to oil it way more often. Just sayin...

I am sure there are lots of debates about whether a cored or uncored galvanized wire is better.

On the big sailing vessel I used to sail on we utilized the oil approach with a core.

I elected to utilized synthetic linseed oil instead of oil. It is a bit more expensive however, doesn't wash off after it is cures. I learned the hard way to keep a drop cloth below any line I touched up for at least a day. Drops would fall off hours later and harden and stick like glue to the deck.

Overall I just wanted to bring up to Chotu that there was a third option. His vessel and loads are large enough to consider galvanized. Most larger vessels utilize it because it is

...less expensive
...stronger
...can be maintained fairly easily
...is great for a DIY.

[skenn_ie]

Dynema, AFAIK, was developed for climbers. It is a shock/energy absorbing line that loses it's strength relatively quickly. It is not, IMO, suitable for high loads with frequent/continuous jerking.

[Chotu]

Originally Posted by skenn_ie

Dynema, AFAIK, was developed for climbers. It is a shock/energy absorbing line that loses it's strength relatively quickly. It is not, IMO, suitable for high loads with frequent/continuous jerking.

I’ll let somebody else field this one.

[Breaking Waves]

Originally Posted by skenn_ie

Dynema, AFAIK,

was developed for climbers.

No, first application was ballistic protection, ship and rig mooring lines & offshore trawler lines were 2nd major applications. Climbers use it in slings (for lightness and strength) but not at all in their dynamic protection climbing ropes.

It is a shock/energy absorbing line

No, it is the opposite - a high modulus fiber. At 30% of breaking strength, it's elastic elongation is just less than 1%, compared to around 12% for nylon.


that loses it's strength relatively quickly.

No, as its use as long-term deep mooring lines for oil rigs attests. It has weaknesses (like a relatively low melting point, and creep) but is relatively bend and fatigue resistant (compared to other high modulus fibers).

......

[fxykty]

Our Dyneema shrouds (one per side) are anchored to turnbuckles. Lashings should only be used with rotating masts or smaller boats (generally less than 40’) as you just can’t get higher tensions with lashings.

Super easy to adjust with turnbuckles, which we’ve done 4 full turns each side in the 1.5 years and 13K ocean miles since installing. Due to creep I expect 2-3 turns each year to maintain the same tension. When first installed, we took out 30cm of constructional stretch despite having set our top splices with a hydraulic ram.

That said, when you size heat-set Dyneema (DUX, DM20, etc) for stretch rather than strength you get no stretch, minimal creep and 5x the breaking strength of 3x19 SS wire. The gradual deterioration of the breaking strength due to UV damage does not alter the stretch/creep characteristics of the cable so you have plenty of reserve before you get to similar strength as the wire it replaced. It’s this deterioration curve that has so many variables and hence the wide range of 5-12 years for Dyneema rigging.

[Happ]

Originally Posted by Chotu

Please think of my boat and my situation rather than your boat when making your recommendation.

Current situation:

I have a mast that is getting extended at its base by 5ft. I’m leaving all the attachment points where they are open n the mast itself, so I need to lengthen the forestay and shrouds. I ONLY have a forestay and shrouds. 3 point fractional rig. I have all the old standing rigging for this mast and it’s in great shape.

The current idea is to add some length to the bottom of the existing standing rigging to make up for the increased height.

Questions:

1) What is the service life of dyneema compared with stainless steel?

2) I don’t know how to install dyneema or do all of those fancy little knots and loops that are used. This boat has about 1 million other projects that need to be done. Is it faster to do steel or dyneema given I know zero about the dyneema rigging methods? Note: I’m not an expert on steel either.

3) Is it more expensive to do steel or dyneema? Currently I have most of the steel. Everything to a point a few feet above the deck. I need to bridge the gap from where the current steel ends to where it needs to end with the extended mast. Otherwise, it’s $0 to do stainless. But those few feet of extensions and fittings might be expensive. I don’t know.

4) What is the difference in weight between stainless and dyneema on a 65ft stick on a 50ft cat?

For my boat and my situation (not if you prefer Dyneema or love it on your boat), which should I go with?

Steel is more expensive then Dyneema. With Dyneema you have the added costs of the connectors and Dyneema lasts about 1/2 the amount of time. Tuning the rig is much more difficult and less precise if you don’t what you are doing. As to wait it is significant. But compared to the weight of a cruising cat it’s nothing. Strength to weight is about 5:1.

Unless you have a very fast tri put wire on it. It will last 10 years.