Novice questions about dyneema

[trswem]

Hello all. I'm looking to build some soft shackles from Dyneema, and replace my aging lifelines with Dyneema as well. Could someone point me towards a good source for buying Dyneema by the spool?

Also, is there a rule of thumb for the size of the Dyneema diameter that you use when replacing running rigging? I have 5/16" sheets on my headsails. I will be replacing my light wind sheets with Dyneema, and I'm assuming I can size down pretty substantially. I am aware that I would likely need to change my cleats for smaller diameter.

Thanks!

[Pandor]

Yes, you’d be able to downsize substantially. If you wanted to know exactly how much, just match the new working strength of smaller Dyneema to the working strength of your existing line. But in practical terms, the limit on Dyneema running rigging tends to be sizing to fit existing rope clutches and self tailers, as well as just sizing to fit your hand comfortably when tailing.

[markxengineerin]

Are you sure you want dyneema for running rigging, even for light stuff? It's slippery as hell, not good in rope clutches, cleats, or hands, and doesn't have any stretch to it to absorb shock loads. Not a lot of people using it for running rigging!

For suppliers, check any local chandlery, any mail order chandlery, Sampson ropes, New England Ropes. I expect all of them will offer it by the spool.

[Breaking Waves]

Originally Posted by trswem

Could someone point me towards a good source for buying Dyneema by the spool?

would be helpful if we knew where in the world you were

[hugosalt]

Here in the USA I buy Samson Dyneema SK-78 from "SRE Outdoors"
1/4 inch 600 ft spools, well priced.
Have used for life lines, soft shackles, halyard for wire luff drifter, but not other running rigging.

[hugosalt]

Welcome to Cruisersforum!
Have thought about using small light weight Dyneema for light air sail/shts. but would
then be splicing to conventional line for winch and hand. More trouble than its worth
for me.*

[trswem]

Originally Posted by markxengineerin

Are you sure you want dyneema for running rigging, even for light stuff? It's slippery as hell, not good in rope clutches, cleats, or hands, and doesn't have any stretch to it to absorb shock loads. Not a lot of people using it for running rigging!

Good point, I definitely am not replacing all my running rigging. I'm mostly looking at my light wind sail and jib downhaul. I also like the idea of having a spool stored away for insurance!

Originally Posted by Breaking Waves

would be helpful if we knew where in the world you were

Eastern Washington. We have a small West Marine location in Spokane, but we're very light on marine suppliers.

[Breaking Waves]

Originally Posted by trswem

Eastern Washington. We have a small West Marine location in Spokane, but we're very light on marine suppliers.

I buy full spools direct from Samson, but I buy wholesale quantities and have done testing for them There are a lot of suppliers who will sell single spools like:

https://ripstopbytheroll.com/product...el-full-spools
https://www.knotandrope.com/products...dyneema-spools
https://cbknot.com/samson-amsteel-bl...-x-600-spools/

[jcapo]

Go2marine.com usually has good Dyneema prices.

[fxykty]

For bulk purchases and some specialised gear we use Greenline Fishing in Denmark https://greenlinefishinggear.com/ and they ship throughout the world. The Acera Amundsen product is excellent, albeit yellow https://greenlinefishinggear.com/pro...cera-products/.

[Russ]

https://www.colligomarine.com/produc...-lifeline-kits

They have it all plus simple instructions

Lasts forever. Russ

[thinwater]

Dyneema has strengths and weaknesses.



Strengths

• Very strong ... but that doesn't matter in smaller lines, where there is a minium size for handling.
• Stretch. Very low stretch ... but the jib sheet on a 26' boat, for example, is only a few feet long when sailing to weather. Good for replacing wire halyards, but you need to clean up the sheaves. Bad for travelers, where you need shock absorption. Good for vangs ... but the tails need to be large enough for the jammers and winches.
• Abrasion resistant ... but single braid is not as good side-to-side as polyester DB. Proven in testing and in the field. Same with UV; not really better than polyester. I cut a whisker stay with a running sheet in one bad jibe. If used to replace wire lifelines, the stanchions will need polishing and chafe guards.

Weaknesses

• Very slippery. Difficult with out covers.
• Very small. This means the tails need to be covered. Learn to splice.
• Doesn't hold knots well.

I've used a lot of Dyneema. The only places it really shines over polyester are through low friction rings. Otherwise, it's often just more trouble. As for replacing wire ... it depends. It's light and seems easier to install (easy to do wrong), but in many applications, it is less forgiving and durable.

[JPA Cate]

Fisheries Supply in Seattle.

Phone them and see if they can supply you with what you want. You can also buy covers for dyneema line, so it doesn't slip in rope clutches and on winches. Fwiw, there's a lot of dyneema used in the fishing industry these days.

Ann

[Dockhead]

Originally Posted by thinwater

Dyneema has strengths and weaknesses.

Strengths

• Very strong ... but that doesn't matter in smaller lines, where there is a minium size for handling.
• Stretch. Very low stretch ... but the jib sheet on a 26' boat, for example, is only a few feet long when sailing to weather. Good for replacing wire halyards, but you need to clean up the sheaves. Bad for travelers, where you need shock absorption. Good for vangs ... but the tails need to be large enough for the jammers and winches.
• Abrasion resistant ... but single braid is not as good side-to-side as polyester DB. Proven in testing and in the field. Same with UV; not really better than polyester. I cut a whisker stay with a running sheet in one bad jibe. If used to replace wire lifelines, the stanchions will need polishing and chafe guards.

Weaknesses

• Very slippery. Difficult with out covers.
• Very small. This means the tails need to be covered. Learn to splice.
• Doesn't hold knots well.

I've used a lot of Dyneema. The only places it really shines over polyester are through low friction rings. Otherwise, it's often just more trouble. As for replacing wire ... it depends. It's light and seems easier to install (easy to do wrong), but in many applications, it is less forgiving and durable.

Well, like-for-like in terms of strength, dyneema cordage is far lighter and far more flexible, with far less stretch. Single braid is not the only way to use this -- double braid with a nonstructural polyester cover is also available.


So I think the advantages are far greater than just being good with low friction rings.


Those advantages are less important on a smaller boat with smaller sails and lower loads; for a larger boat dyneema running rigging is just about mandatory.


My boat was originally built with some dyneema in the running rigging -- staysail sheet, outhaul, running backs. I later replaced the 16mm polyester jib sheets with 14mm racing grade dyneema -- a real transformation, much more control, no more panting, much better handling. Mainsheet from 14mm polyester to 12mm dyneema -- something like half the weight, far more flexible, better handling. I changed my furlers from 12mm polyester to 10mm dyneema. By now, I no longer have any polyester running rigging anywhere.



Dyneema double braid is much harder to splice than single braid, but somewhat easier than polyester double braid since the cover is non-structural. Another advantage of it is that you can strip the parts of the rope which are not handled -- increasing flexibility further.


The OP won't realize all of these advantages because minimum diameters for the sake of handling will limit his ability to downsize the cordage. I would still go with dyneema, if I were he. It's just better.

[becrux]

Originally Posted by JPA Cate

Fisheries Supply in Seattle.

Phone them and see if they can supply you with what you want. You can also buy covers for dyneema line, so it doesn't slip in rope clutches and on winches. Fwiw, there's a lot of dyneema used in the fishing industry these days.

Ann

https://www.fisheriessupply.com/sams...72-012-706-030

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