Synthetic standing rigging on a small boat

[wyb2]

I’m in the brainstorming phase of replacing the standing rigging on my Macgregor 25 trailer sailer (older iron swing keel, not water ballast power sailer). One thing I noticed on the brief shakedown trip we’ve taken so far is that the SS rigging is kind of annoying for the whole trailering and mast raising process. Since it’s only semi-flexible, it has a little bit of a mind of its own as you try to maneuver the mast. And since you really don’t want to kink it, you are constantly trying to keep an eye on 6 wires to make sure they aren’t snagging on anything.

This got me thinking about synthetic. Most people that switch seem to do so to reduce weight and fears of crevice corrosion. I would count both those as benefits, but also largely thinking that it might be easier to handle? In my dreams, when I lower the mast I could just unclip everything, coil them up and throw them in a designated storage location inside the boat. Nothing flapping in the wind on the highway on the way home.

So what I’m interested in is if anyone has first hand experience with synthetic rigging on a trailer sailer. Good, bad, surprises? If you have experience with it on a larger boat and want to weigh in, please just keep in mind that my whole boat probably weighs less than your keel.

[goat]

Personally, I'd say do it. Just make sure you stitch the eye splices since the tension is what gives the splice it's strength, like a Chinese finger trap. I have no experience with trailer sailors but synthetic stays and soft shackles make for an easily stored staysail stay.

goat (the animal not the acronym)

[wyb2]

Originally Posted by goat

Personally, I'd say do it. Just make sure you stitch the eye splices since the tension is what gives the splice it's strength, like a Chinese finger trap. I have no experience with trailer sailors but synthetic stays and soft shackles make for an easily stored staysail stay.

goat (the animal not the acronym)

I hadn’t thought about removable staysail stays (staystay?). That’s a good datapoint, thanks.

[wyb2]

Hmm, maybe I made my ask too narrow.

Anyone DIY synthetic rigging on any smallish boat?

[thomm225]

Originally Posted by wyb2

Hmm, maybe I made my ask too narrow.

Anyone DIY synthetic rigging on any smallish boat?

Sean D'E did and has sailed his Bristol 27 across a few oceans

https://towndock.net/shippingnews/se...-and-alexandra

[kayakerChuck]

I rigged my O'Day 22 with synthetic, pretty much for the reasons you list.

Now I don't worry about kinking the rigging while raising or lowering the mast. It's also lighter, so things are easier going up & down. I leave mine attached & secure them to the mast with some bungie cords.

I would not consider going back to SS on a trailer sailer.

[wyb2]

Originally Posted by thomm225

Sean D'E did and has sailed his Bristol 27 across a few oceans

https://towndock.net/shippingnews/se...-and-alexandra

Can’t say that’s exactly the look I’m going for, but, if it works it works. Happy to hear the details.

Same guy that posts on here with what I think is the same name? Maybe he’ll chime in.

[wyb2]

Originally Posted by kayakerChuck

I rigged my O'Day 22 with synthetic, pretty much for the reasons you list.

Now I don't worry about kinking the rigging while raising or lowering the mast. It's also lighter, so things are easier going up & down. I leave mine attached & secure them to the mast with some bungie cords.

I would not consider going back to SS on a trailer sailer.

Awesome, thank you. The fancy dux stuff, or something else? Did you use any specialized fittings, or make it work with off the shelf hardware?

[Nekton73]

To your main question no I have not rigged a small boat with synthetic, but I have used it a lot for other rigging and wouldn't hesitate to do it for a trailer sailer. It would be a good choice for all the reasons you have listed so far.


Drawbacks, as I'm sure you will discover as you research, are primarily chafe or other mechanical damage, and creep (like stretch, but not the same thing). Chafe can be managed by protecting where needed and by being careful when you rig/derig and transport. A spare length of material in your locker is cheap and easy to fab a replacement for anything you might need to. Many boats, cruisers and racers, run synthetic rigging with great success and manage these issues just fine.


Creep - I won't go into a long explanation here, there are plenty of resources for you to research the issue, but it is a progressive lengthening of dyneema over time when it is under constant load. It is a characteristic that needs to be taken into account but, since you are rigging for short term use, creep shouldn't be as big a factor as it would for a boat with full time standing rigging. You should be able to get away with turnbuckles for tensioning for day or weekend sailing instead of lashing, especially if you choose a good quality product such as Dux or a (minimum) SK78 dyneema that has been heat treated or pre-stretched. I believe Marlow and a couple others now sell a DM20 grade that exhibits very low creep. Given the small diameter and short lengths you will be working with it may be easiest to pay a bit extra for the DM20 and not worry about this issue. Splicing and making eyes is a breeze. A solid sailmaker's thimble should be more than strong enough for your terminations.



Go for it, enjoy the learning process, and the ease of rigging your boat every time you want to use it.

[wyb2]

Originally Posted by Nekton73

…

Go for it, enjoy the learning process, and the ease of rigging your boat every time you want to use it.

Great, thank you.

I was aware of creep, and as you mentioned, I figured it would be less of an issue (if at all) with the boat living 90% of it’s life on the trailer with the mast down. Even rigged, I would guess the pretension in the shrouds is measured in the 10s of pounds, not hundreds. I do need to learn more on the actual product options, never heard of DM20, so thanks for that tip.

[Nekton73]

Actually your stay and shroud pre-tension values are easily determined and should be adhered to, both for best performance and for safety.


I don't know the diameter(s) of your stays and shrouds but lets use 1/8", 3/16" and 1/4" 1x19 stainless wire rope as the most likely. Commonly accepted breaking strengths of these are: 1/4" = 6900lbs, 3/16" = 4000lbs and 1/8" = 1760lbs



Standard pre-tension for sailboat rigging is between 10% and 20% of breaking strength, with 15% being a typical starting point. This achieves a solid and stable rig that won't flex or deflect from plumb (or rake) under typical sailing loads, while leaving sufficient margin for extreme circumstances. There is an excellent book called Understanding Rigs and Rigging by Richard Henderson that would make good reading if you want to understand rig design in more depth.



15% of 6900 = 1035 lbs
15% of 4000 = 600 lbs
15% of 1760 = 264 lbs


So these are your likely pre-tension values which you should aim to achieve with your stainless rigging. If I owned a trailer sailer that I was rigging frequently I would spend the $120 bucks or so for a tensiometer and use it to quickly dial in my rigging each time. It's worth it even for a seasonal sailor such as myself who only does it once per year. Good for a mid-season check too. Serious racers who like to tune their rigs for different conditions use them often as well.


But now we're talking dyneema where creep is an issue. The rule of thumb is to keep tension under 10% breaking strength to limit creep. You can't eliminate it, but you can keep it low enough to be a non-issue vs. other lifespan factors. Your rig design in stainless has already given you the pre-tension values that you want to achieve for a stable and well performing rig, so you want to size your dyneema to achieve those same pre-tension values while keeping constant load under 10%. You will find that, in general, using the next size up in Dyneema will achieve this.


Let's assume your rigging is 3/16" 1x19 stainless with a UBS of 4000# and a pre-tension of 600#


Amsteel 3/16" UBS is 5400# x .10 = 540#, a bit below your target pre-tension, and already approaching the max. for limiting creep.


This would probably be good enough for your purposes as a trailer sailer, but upsizing to 1/4" would give:



Amsteel 1/4" UBS is 8600# x .10 = 860#... now you can tension to your target 600# at an even lower %BS of the dyneema (~7%) essentially eliminating creep concerns.


A small increase in size and windage for a large increase in ultimate strength, and still much lighter and easier to handle than 3/16" stainless.


You can do the math for the other sizes. Hope this is helpful.

[Benz]

I have a 21' trailer sailor I rigged with dyneema: just regular SK78: as others have noted, creep is not an issue over brief periods of use. It's quick and easy to set up and downrig, and I have had no issues in two years of that, nor in twelve years of sythetic rigging on my bigger boat.

[wyb2]

Originally Posted by Nekton73

…

You can do the math for the other sizes. Hope this is helpful.

Thanks, that’s a good guide to the thought process on sizing.

[wyb2]

Originally Posted by Benz

I have a 21' trailer sailor I rigged with dyneema: just regular SK78: as others have noted, creep is not an issue over brief periods of use. It's quick and easy to set up and downrig, and I have had no issues in two years of that, nor in twelve years of sythetic rigging on my bigger boat.

Nice. Did you rig the smaller boat with all off the shelf hardware, or did you have to buy any specialty fittings?

[kayakerChuck]

Originally Posted by wyb2

Awesome, thank you. The fancy dux stuff, or something else? Did you use any specialized fittings, or make it work with off the shelf hardware?

I used Amsteel and spliced a low friction ring to each end of each stay. The upper LFR's replaced the tangs on my mast, with suitable spacers & such. The lower LFR got lashed with small dyneema (1/8"??) to a shackle, which attached to the chainplates. Simple, cheap, easy to adjust, and more than strong enough for my little 22'. Obviously, adjust the sizes to your loads

Occasionally I need to adjust the tension. It only takes me a few minutes.