DIY External Dyneema Chainplates? Dyneema Standing Rigging Episode 5
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- Опубліковано 4 лют 2025
- Wanting to create external chainplates made from Dyneema? Ideal for Dyneema standing rigging. Simple, strong, cheap and easy to DIY.
This is a variation of Dyneema chainplate that uses the Dyneema loops from our chainplate system in a different way. Could be a great option if you are working with an older GRP boat, switching to dyneema rigging and are concerned about your chainplates.
In previous episodes we have shown the internal Dyneema chainplates we are building, we have now worked out how you might create an external version. These will avoid waterproofing issues and will be fantastic for distributing the rigging loads down the hull.
We are changing all the standing rigging on our 1977 Rival 38 to Dyneema synthetic rigging. That includes all shrouds, stays and even the chainplates for both masts of our ketch rig.
This is the 5th episode in our Dyneema series that will cover all the design choices, the practicalities of a completely DIY re-rig and then how it works out when we go sailing.
Our goal is a rig that is:
stronger
lighter
cheaper
allows us to sail faster
lasts longer
can be DIY maintained even replaced, anywhere in the world
We are refitting a 44 year old Rival 38 for a Sustainable Sailing retirement in a few years. Two years ago, when we bought Vida she was in a very tired and damp condition with all original equipment and fittings (much of it not working). We have removed all the gas, diesel and paraffin equipment, and are installing all electric (motor, cooking etc).
Lots more detail on our blog at sustainablesai...
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Track: Liquid Sky
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Hi, interesting retro fit option. You could use a (ready made) low friction ring or SS round thimble for the dyneema to loop over as smooth surface is important for the durability of the dyneema.
The vulnerability to damage and interfering with water flow on the heeled boat are seperate considerations that I’m not fully comfortable with ,
The wider sheeting angle also could interfere with headsail sheeting angles effecting ability to sail to windward.
I agree a molded in pocket at the original hull design stage would eliminate done issues but from a boatbuilder stand point such details are always a hassle in production and interfere with the continuous structure of the hull.
Thanks for sharing your ideas.
Cheers Warren
Hi Warren,
Thanks for the detailed and thoughtful response.
Using a Low Friction Ring or Thimble for the dyneema where it attaches to the hull is great for the dyneema but one of the challenges is to avoid point loading those. So you would want to match the inside of the low friction ring to the diameter of the bolt (or maybe a sleeve around the bolt). Or make a solid infill for the thimble that the bolt goes through.
Our experience with shaping FR4 is that it should be possible to sand a pretty good surface for the dyneema.
I agree that protecting the dyneema from water flow, debris in the water etc is important. However, I believe that dyneema is being used for bobstays where this would also be an issue. I'm thinking that the "shield" used to protect the dyneema from chafe against pontoons etc might be sealed to the hull, at least on the forward side.
Working out the details of how the shield can work and still allow the dyneema to be inspected and replaced is going to be critical. I'm thinking it needs to be epoxied into place with maybe cutouts for the circles that retain the dyneema. Maybe these would also act as covers for the bolt heads (it would be nice to be able to inspect and even replace the dyneema without unbolting it from the hull).
Sheeting angles, yes. We are moving to a cutter rig so our staysail will be well inboard and our yankee won't be overlapping so probably also sheeted inboard but would need thinking about for Code 0 etc.
On a future cruising boat I wonder if a carbon fibre tube might be moulded into the toe rail or bulwark that the dyneema could attach to, I think some racing boats already do something similar.
Dave
Hi I think there are some interesting ideas here, yes you would definitely need a solid infill piece for any thimble , some ready made dyneema fittings are made from solid already. It should be quite easy to use a small screw in the center of the bolt to hold the cover on. Or have screws go into the infill piece so the mounting bolt never has to be removed in normal use.
Your hull can definalty take this sort of Point loading a thin ( or cored) performance hull would need carful consideration to incorporate into the hull.
I do worry about dirt accumulating in dyneema , I believe it will cause internal abrasion? Dirt coming off the deck could be an issue.
It just occurred to me this thimble type mounting is already used on the mast top end of dyneema fittings if I'm not mistaken.
Cheers Warren
We think Colligo make the best range of dyneema fittings, however, they are beyond our budget. One of their fittings designed to fit into a fork toggle could presumably be bolted to the hull. So far theirs are the only fittings I have seen that have the centre of a thimble filled in. However, I think it should be possible to fabricate a DIY option in a number of ways. Our first suggestion reduces the amount of metal as it seems to us that a disc of a material such as FR4 can have the edge routed out providing a very smooth and hard wearing anchor point for a dyneema eye splice, one that will never corrode and which you can epoxy to the hull if desired to reduce the reliance on the bolt..
I have mixed feelings about the dirt issue. My understanding is that lots of big racing boats such as IMOCAs, the big Cats and Tris have been using dyneema soft anchors for their rigging for a while. They will certainly spend a lot of time immersed in the sea. Wharrams have used soft lashings for beams and rudder pintles for decades.
On the other hand we would probably create soft covers that would stop debris washing into the Dyneema with the added bonus of extra chafe and UV protection.
My preference for a cored hull would be to do what is recommended for cored deck fittings ie drill out, fill with the thickened epoxy and then drill through that.
Thanks
Dave
The friction created by a bolted joint is what holds your loads, not the bolt itself being in shear so a standard chainplate does indeed have equal loading on the bolts.
we are basing our views on what Jane was taught (many years ago) in her Civil Engineering degree. These calculations are very conservative as the risks of failure are so great. When bolting two plates together with a lengthways set of bolts they calculated the load entirely on the first bolt.
Obviously the situation is more nuanced than that but better safe than sorry.
Not sure that you really get all that much load spreading here, compared to bolting a stainless chainplate (or laminated carbon chainplates).
A bolted connection isn't actually relying on shear loading of the bolts, but rather the friction between the two bolted surfaces.
A solution like this is more or less 100% shear load on the bolts, and probably more importantly, the hollow edge pressure in the holes of the laminate.
I'd do some thorough calculations and perhaps even tests before building chainplates like this.
It really isn't quite the same as bolting a metal plate onto the hull.
It would of course be a lot more work, but I don't see any reason why one couldn't fit carbon or fiberglass laminated chainplates of the style that is used on modern raceboats. It would last longer, be stronger and safer and spread the load far better.
That's probably the path I'll take on my Wasa 55 build :)
I don't think I've seen many raceboats use dyneema loops as the actual chainplate, except for some that uses a system similar to your first design for their backstays. It's usually a laminated loop around a stainless or titanium tube with a pin going through to connect to the rigging.
Many seem to use dyneema pad eyes though, for less critical or less loaded things.
We are a bit concerned that in a new build the integrated chainplates have a chemical bond to the hull whereas in a retrofit you can only get a mechanical bond to the top layer of the original grp.
Given the bend radius of dyneema we figure the outboard discs will be a pretty good size and they can be bonded as well as bolted. So they should be more than bolt sheer strength.
Mostly this is to get people thinking about possibilities. I suspect that if doing this it will end up being vastly over engineered as we size dyneema for stretch and so end up thinking through on the dyneema breaking strength which is so many more times greater than the stainless it replaces.
I'd love to explore ways to avoid the stainless bolts completely and combine the external disks with carbon fibre tubes to replace the bolts and add internal plates and grp to tie internal and external to the hull. This way you can have a close to fully integrated chainplate with no holes in the hull and nothing to rust.
Also agree about the pad eyes, except that a lightly loaded pad eye on a super yacht has a much greater load than anything on our 50 year old 38 foot cruising design 😁
@@SustainableSailing yeah, I agree, of course it's better to laminate/bond in composite chainplates when building the boat.
But, since chainplates would likely only ever be built with epoxy I'm not sure if it really matters that much, you can get some very strong bonds between a fully cured polyester hull and an epoxy laminate. Maybe even stronger than interlaminate strength of the original polyester laminate.
It's not like one can't fix broken composites after all, even with polyester on old polyester hills it works just fine as long as it's done properly. With carbon/epoxy composites you can usually repair a broken (fully cured) part with little or even ko additional weight, that is one of the many benefits of composites :)
If you laminate a composite chainplate (should probably be carbon/epoxy for longevity), it's basically glued with epoxy to the hull, over a very large area, many times bigger than any other way of mounting a chainplate. And that gluejoint will be loaded mostly in shear, so will be very strong :)
I fully agree with the goals here, I want to get away from metals as much as possible in my build as well :)
I leaning heavily towards dyneema rigging, composite chainplates (or perhaps some dyneema solution), carbon rudder stock and maybe even a glass or carbon keelfin laminated onto the yacht.
The yacht in question is a an old but never finished Wasa 55, hull/deck built in 1988, I bought it back in 2002 and the project has been stalled for 8 years or do now, but starting up again :)
Skerrycruiser style boat, 13,5m long and 2,55m wide, with the rig from a modern 35 foot racer cruiser :) The original Wasa 55s have some great speed potential and I'm aiming to improve it :) boatspeeds of 12-14 knots is common, and a few owners have done 16-17knots on many occasions :) not bad for a boat designed in 1972.
Oh and I agree, padeyes for turning blocks on big racing yachts probably see a lot more load than even the capshroud chainplates of a ~40foot cruiser :)
Sounds like a great project, giving old boats new leases of life is definitely what we believe in for sustainability 😍
As we decided to go for the internal chainplate solution for us (to keep the same shroud base) ours does involve simple composite materials with huge 600mm FR4 backing plates. We will be tying the cap shrouds down to the hull as well (still working on the details of that).
We already know that the backing plate can take the approx 4000kg load even when only supported by the edge of a box section of steel. As they are fitted under the solid hull/deck joint which held the original bronze chainplate bolt with a tiny backing plate we are pretty confident 😊