*Soft* spectra chainplates/deck fittings??

Im building an RG65 in balsa with a simple stayed rig and would like some feedback on this:

Use a loop or spectra, epoxied into holes in the deck, and tied into the hull by wetting out with resin and/or laying light glass over the tails where they come through the deck and lie against the hullsides as chainplates. My thinking being that it is very strong, and means I dont have to make or source any parts. Soft shackles are widely used both replacing shackles, hanks through to deck fittings on big boats.

What about taking the concept further and using spectra for shrouds, and replacing turnbuckles with lashings?

Im a newbie to RC but can anyone tell me why wire is still so widely used for shouds generally over a textile such as spectra/dyneema. (if its a rule thing call me an idots for not checking that - I dont think this first boat will be raced).


I think is a valid idea all together for an RG65 since is a small boat. No Rules call for that.
The question is : How much will be strong the “balsa hull” to support the pull forces ?
If a glassed shadow is bonded at that level, it will adds strength, but still the question remain.
With a composite hull the problem would not appear as for the balsa, since in that area glass layers are added and chain plate bonded too at the extreme of the horizontal beam.
Now make a balsa sample and test it applying a pull force in some similar manner as on the model.
Shrouds can be done with 25kg Dyneema .
S/S fishing cables are easy to find, do not present tensile strength, do not offer much resistance to air flux, and thus generally adopted as a standard hardware. Some sailor are actually using single rod instead of multi brains cable, why ? probably fashion style !

I use single rod (fishing wire for big fish) for most of my riggings for shrouds, backstay and jibstay combined with spectra line for the adjustments but I also use the spectra for the sheets and also shrouds and everything else like on my MM. I find the monorod easier to work and terminate without the need for a sleeve. Plus I find it easier on the fingers. just a Personal view and preference.

As for the use of turnbuckles I still use them because I can adjust the tension on the shrouds depending on wind and replicate the tension each time. no doubt spectra loops would be strong enough for RC boat but this is my reason to use turnbuckles.

hope it helps.

I think that that is a very good idea.

Three thoughts:

  1. Spectra is very difficult to get adhesive to adhere to. You may actually do better with CA than epoxy. Experiment.

  2. Spectra (and Kevlar) are not very good in knots or side shear. The shroud attachment may need to be sleeved. Sleeving is pretty easy. Just thread the Spectra through the center of a short piece of Dacron line. Kite people do it all the time. They sell kits for it. http://www.intothewind.com/shop/Stunt_Kites/Stunt_Kite_Line/Sleeving_Kit

  3. Spectra tends to creep over time. This means that if you leave tension on the line it will actually permanently stretch. Kevlar would be much better for this as it does not creep. Remember, your knots and attachments for both Kevlar and Spectra need to be sleeved.

Spectra is slippery, it is a plastic after all, but one way to help it hold a knot or hold in epoxy, is to apply a flame to the end of it. It will melt the fibers into a mushroom shape that will not slip through a knot or epoxy.

I have never had a knot come untied, that I didn’t untie myself, so I don’t really worry about it. I tie bowlines in my Victoria shrouds and sheets, and my IOM sheet lines. I can pull out a jewelers loupe and exacto knife and untie them too.

Thanks for the replies guys, and for raising the issue or glues bonding with fibres. Im going to my local shipchandlery now to see if they still stock very light kelvar string…I dont think the even make it these days but we do know aramids bond well with epoxy, but are very bad knotted or in any situation where there is a kink. These are only models however so we have to keep the scale in perspective.

This arvo i will to a sample of spectra line, inravelled and “flattened” wetted out with straight epoxy. Honestly whatever to bonding issues i probably wont be able to break it by hand but it will indicate if there are any major issues with thebond or whatever.

Barbera (Mikey at most times) worked for riggers as a kid and has no problems splicing but thinks spectra (not kevlar) is almost as stong in a bowline under normal use. Any comments here appreciated.

I have a couple of suggestions to add.

Borrowing techniques we use on race yachts the best solutions for composite & rigging interfaces come from a system called a Dogbone.

You make a soft loop from the spectra, I usually use a double loop so the knot is only half loaded.
One end of the loop gets passed through a hole and a pin or Dogbone is passed through the loop protruding. When you try and pull the loop out of the hole, the Dogbone is pulled and locked in place by the loop.
I typically use a 3mm diameter 10mm long carbon rod slice to make the Dogbone.
It’s a very sound and very, very proven method of securing a line into composite. All the race boats are using this method for securing the runners in the transom and making soft pad eyes for genoa sheeting positions, but there seems no limit to the solutions…
The other method I have used frequently for small lines and securing loops for rope bags and would make sound chainplates is as follows:
Find or make some thin carbon or glass plate. No need for more than a couple of layers. Pre sand both faces as its much easier to do now… Degrease and clean the plate with acetone or alcohol and from now on handle the plate with gloves on.
Cut or punch out two discs. The diameter really is dependant on the application 15mm should be plenty for a chainplate.
Cut a length of the spectra, fold it in half and protect the top section of the loop with masking or electricians tape.
Then fan out the tails. A small wire brush works a treat here. It strips the braids down to what looks like super fine hairs.
Apply epoxy to the one face of each of the discs and wet out the tail of the loop. The tail is placed onto one face and fan out the hairs in a nice radial manner. Then place the second disc on top so the tail is now sandwiched in a button. Clamp very lightly as you do not want to squeeze too much resin out and wait for it to cure.
Clean up any excess after curing and you will have a carbon button that you can pre-test for security then place where you like.

I hope the explanation is clear enough!

Cheers, Jim

Hi Jim,

The system you have described would work well if one needed to retrofit chain plates. Namely drill hole through inwale set up draw string to loop/carbon button - glue button and pull draw string tight.

I’ve just put together 3 Marbleheads, planning on stayless rigs, if they need stays, you’ve given me a possible solution.

Thank you


No problem Baz… Good luck with the testing.


Thanks for al the very useful replies.

I did a test using the core out of 4mm spectra cord. I unravelled and frayed the ends heavily, laying the tails out and scraping them flat. I wet them out with normal epoxy on a bit of scrap play, the tails were spread out to proxide maximum surface area for bonding.

Result, no bonding problems. I was unable to pull them out will all my weight. Will be more than strong enough for any normal usage. Testing them by pulling back against the direction the firbres laid I did however manage to peel it off slightly. This indicates that the resin was not saoking into the fibras fully and I am not getting a proper bonded resin ribre matrix.

Dont read to heavily into this, there was still an excellent bond and the nature of the fibres layout having a very big surface boding area indicates that it will be enourmously strong in destruction testing.

Id be interested to see how kevlar, into which the resin doesnt penetrate, would compare.

In concluson i plan to use this for my shroud chainplates, and possibly the for and backstay if I can workout a way to splay and bond the tail in the hull as I am sure it would be much stringer then a mechanically fastened metal chainplate.