In the previous chapter, Andy explained what Dux is and suggested a bunch of cool ways we can use it on our boats, even if we don't go the whole hog with it. In this chapter he takes a deep dive into when and how to re-rig with Dux.
Designing For Dux Rope Rigging—A Paradigm Shift—Part 2
Reading Time: 7 minutes
I think you covered all the bases, Andy. I feel better informed now. Thank you.
Hi Andy.
I come frome multihull racing, so i have sailed much with various rope rigging types and love it. Still, you teach me things i didn’t really know. Thanks! Related to the 20 years in use, i think John thinks it should be 20 years in use on a significant number of relevant cruising boats.
The traditional rigs that used rope and the modern racers are both quite different boat types, but i think they still are relevant in some ways. The traditional boats were made to be simple, onboard serviceable and reliable. Those are core values for cruisers too.
Racers want the same, plus they want performance, which is also nice on a cruiser. The interesting topic with racers, i think, is the punishment in the shape of expoure to rough treatment and extreme loads they give their equipment. Way more than any cruiser. The extreme racers are the ultimate test platforms. If it survives there, it survives any other boat.
The most important reason the craziest of the racers now use mostly rope rigging and lashings is that its so much stronger and more reliable in real life experience. Much of the reliability comes from the fact that racers inspect the systems nonstop and can clearly see if something might fail soon and then quickly fix it without tools and obtaining tha same strength and function as new. This emphasizes someting you said here, about who should thing about a rope rig. It needs to be checked and cared for.
Bottom line for me still is that rope rigging is very good for a lot of cruisers. I definitely prefer it to any other alternative.
Is there any concern that for an offshore boat, the reduction of weight aloft also reduces dynamic capsize resistance? The additional strength should help keep the mast on and maybe the rigging’s moment of inertia is inconsequential compared to the mast, but has this effect been estimated?
Hi Damon,
I have some thoughts that speak to that here: https://www.morganscloud.com/2008/08/01/sailboat-stability-contradiction/
Hi Damon.
I recommend reading the article John links to, but i can’t resist to comment.
Stability in boats has mainly two reasons. Form stability, like we stand more stable if we move our feet further apart, and low weigth centre, like a pendulum. Inertia, on the other han, is NOT stability, just resistance to change.
A monohull is hoisting a weight up the mast while exposed to waves from abeam: As the weigth gets higher, the centre of gravity goes higher too, reducing stability, of course, but the higher inertia makes the boat slower at reacting to the wave, which is often nice but when it has gotten into motion, it’s also slower at stopping the motion, which is mostly not nice. This means it will roll slower, but move through a greater angle. (Lower frequency and higher amplitude.) This is increased by the reduced stability from a higher centre of weight, that will resist the pendulum motion less.
Conclusion:
No surprises, a boat with a heavier rig will roll slower but more, so it will be more unpleasant to be aboard. It will also sail noticeably slower. Partly because it will lift its bow higher and slam deeper at each meeting wave, and partly because it has less stability and thus less ability to hold its sails. It is NEVER a good idea to make the rig heavier than it must be.
So, am i saying that there are a lot of people out there making false claims? Well, let me think… Hm. Yes, that’s what i do say! 🙂 There’s much complete bullshit out there on this topic, even from “serious” people. I can’t prove by words I’m better. You’ll have to use your own logic to decide what you think is true….
Hi S.A.
While I agree that a lighter rig is generally better, I’m not sure I would agree that there’s no limit to that improvement. For example, when we changed to a carbon rig on our own boat, many things got better, but on the other hand, she is defiantly noticeably less comfortable with a faster jerkier motion when motoring with no sail up and the waves on the beam. This is not enough to be a problem, but it does indicate that there are tradeoffs. More Here: https://www.morganscloud.com/2009/02/01/carbon-fibre-mast-costs-and-benefits/
Hi guys. Thanks for responding. I’m a mechanical engineer and understand the forces. But like John’s link says, the physics is complicated and it’s simplistic to talk about specific forces or conclusions. I’m not suggesting to make the rig heavier. I’m asking if there is any risk in making it lighter than the type that has hundreds of thousands of successful ocean miles (and where experience suggests removing the rig drastically reduces capsize resistance). My guess is that the difference in weight we are talking about doesn’t really matter to either the static or dynamic stability, but I wanted to know if anyone had run the numbers. These answers say: “nah, we don’t need to [we already know the answer despite the complicated physics].” Some of John’s link is about moving weight from several feet above the center of gravity to a foot above it and that is unquestionably good. My question was about weight much further away, and even if the effect is overstated, I would think it is worth understanding to best balance different components of stability.
Hi Damon,
The maths on this are way beyond my pay grade, but what I think I can say with confidence is that the weight difference with Dux is not enough to cause a problem and is in fact a benefit. My thinking is that most, probably all, cruising boats are designed with rig weights that are limited on the light side by cost and available materials. Or to put it another way, cruising masts are already way heavier than the minimum dictated by dynamic stability, and therefore a change to Dux will be all positive as far as weight goes.
Another empirical indicator is that many cruising boats have changed to carbon rigs, which saves way more weight than Dux would (600 lb in our case) without any spate of dynamic stability problems.
Hi Damon.
I didnt try to be a wise ass. Sorry if it seemed that way. Since my mother tongue isn’t English i probably mess up some, and even worse, being Norwegian means i have no manners. We just came out of the cave. 🙂
I won’t try to crunch numbers. I probably could figure it out about right, strughling for some hours and consulting Professor C A Marchajs books, 🙂 but I’m more into actual experience.
More than long distance cruising, I come from decades of racing, including some of the most extreme stuff on the planet, which has given me some very clear demonstrations of what a reduction in weight aloft does to the boat. On very light boats, small changes are easier to notice, but it works the same way.
The report after the 1979 Fastnet Race really needed to have some “good answers”, for political reasons, and was made by among others, even at that time out dated designers, engineers, etc. It has a seemingly good wiew on much of the topics but quite fragmented on others. The claim that more weight aloft gives a more seaworthy sailboat is correct in such a irrelevant way it must be deemed outrageously flawed thinking.
I’ve raced many boats where the rig has been changed during or between seasons. Monohulls and multihulls. Always lighter rig, if course. Most of them we sailed in rough weather. The difference was always a joy. The boat behaves much better. It handles better, is more comfortable, faster, the works. Disadvantages? None.
As John mentioned in the linked article, a boat with more stability and that handles as goid as possible, is better able to avoid a situation where more inertia would be beneficial. That is, lying with the waves beam on, when most boats, including those with heavy rigs, would be flipped anyway.
One comment on this regarding rig strength in a capsize – yes, the Dux would be much stronger, but that doesn’t mean the rig will stay up. The bolts at the mast tangs or chainplates will be considerably weaker than the Dux, so that’s where the failure would occur potentially. Recall my comment on rigging=a chain – only as strong as the weakest link. Yves Gelinas, the single-handed sailor who invented the Cape Horn windvane, learned this the hard way – in a capsize west of the Horn, he lost his rig when the chainplate bolts sheared – the only part of he rig he hadn’t substantially beefed up.
What sort of upgrades are required for a mast? For example I have T sockets in my mast for the T swages to fit into. Would the T socket have to be changed or are there fittings for the Dux that would be compatible?
Alastair
Dux fittings can be made to work with t-fittings. The most elegant & robust solution is ‘cheeky tangs,’ which use a mast through-bolt and then the Dux is spliced around a sort of cheek block, but t-fittings are adaptable.
Well done Andy. I removed 44 lbs. of weight from the standing rigging on my Contour 34 cruising trimaran by making the change to Colligo Dux for the upper and lower back stays. (Rotating 53ft. mast) At John Franta’s advice (in 2010), I did leave the diamond stays in 1×19 wire. At 6 years of service, the current owner based in Anguilla says there is a slight bit of fuzz to the Dux rigging. I do understand that tension gauges are now made for the use on diamond shrouds.
My current 40′ cruising cat will be changed over to Dux with t-sockets and continuous spreader tips, the first part of next year.
To answer Alastair, Yes T-sockets can be custom made by John @ Colligo if your size in not in his normal stock.
To not think that I would be spreading any spam. Do a Google search for Colligomarine (dot) com for John’s website. There are other retailers and riggers of Dux, but John will give you an honest answer to your questions.
Regards,
Clint
Thanks Clint for the information.
Hi Andy,
Thanks for these 2 pieces on synthetic rigging. I find it very interesting but it is also something which I don’t want to be too early of an adopter on. Colligo’s website still claims 750 rigs which is quite a small number in the grand scheme of things but that number may be a bit out of date. To me, the biggest advantage would be the loss of weight aloft but there are definitely other advantages as well. In truth, the real way to improve the performance of our boat would be to get a carbon mast but we are not willing to pay for one.
Have you seen any information on the effect of the extra windage of the larger diameter lines? This is obviously boat specific but it would be interesting to know if it is enough to make a performance difference or even enough of one to measure.
I plan to replace our lifelines with synthetic next winter and then will need to make a decision on what to do with the standing rigging the following winter. I think that it will take a while longer to build up the data to convince me that it will last for 10 years of UV exposure which is really my personal minimum. I have also been somewhat disappointed in the cost, I had originally heard that it would be cheaper than wire but when I priced out the fittings, that was not what I found. Even the lifeline prices were more expensive than I was expecting but I really don’t like either of my other options (coated and uncoated wire) for various reasons.
Eric
Hi Eric, windage is a non-issue for me. If you sail with any sort of canvas, that is going to offer way way more windage than a few extra mm on the shrouds will. Probably not even measurable, and in any case, only affects you negatively going dead upwind!
I can’t offer specific numbers either, but have spent some time pondering the issue. My best source for this type of questions is “Aero- Hydrodynamics of Sailing” by Prof. C A Marchaj. An old book now, but still quite a nerd bible. He does go into detail on almost everything thinkable, including drag on wires.
That drag is apparently a bigger issue than most sailors realize. The biggest problem seems to be having to many , though. Stays, shrouds halyards, etc exposed to undisturbed flow. The thickness matters too, but apparently less, if not taken to extremes. Changing from 6 to 9 mm is adding 50% to the projected area, and a round profile has close to max possible drag. The drag increase should be close to the square of the area increase.
This does matter for windward ability, mainly in how high the boat can point, as the efficiency of the rig drops, but still will probably only be a clearly noticeable issue for serious racers. For cruisers, i assume it will only matter when forced to fight upwind in a gale. In those cases, the sail area is tiny, while the rig is just as big as normal. The lift to drag ratio becomes very poor, making it hard to make progress to windward. Thinner shrouds etc won’t make a world of difference, but sometime those few degrees was what was needed to get away.
Hi Eric,
I did some back of the envelope calculations for the dimensions described for Arcturus assuming a mast height of 50′ and a single spreader rig. The difference in windage is 0.6 versus 0.91 square feet for wire versus Dux. So not much difference. I can’t imagine that the increase in drag is significant relative to the drag of appendages in water but see the comment from S. A. Varjord below.
Thanks Andy, S A and Barry for the thoughts. It would be good to someday understand the real effects of windage. Obviously, people often add huge amounts of windage to their boats in terms of cockpit enclosures and similar things but it would be good to eventually have a rough idea of the contribution of standing rigging for those people who try to focus on sailing performance. I have been in the situation where a boat really can’t make progress to weather due to not being able to carry enough sail compared to all of the losses like the area of the hull and it is a scary and weird situation to be in.
Our boat has a pretty tall rig for its size which I generally like but it means that it is not as good when the wind is really up. I have noticed that when there are no waves, starting at about 25 knots steady, our pointing ability starts dropping off dramatically as the wind increases and by the time we have hit 40 knots, we have lost probably 15 degrees of pointing ability. Based simply on how much the boat heels when motoring at the same angle in the same wind, it becomes clear that you can’t fly a ton of sail then. Given that going to weather in this much wind is rarely a good idea as there are usually big waves, it isn’t generally a big problem but you would hate to find that out.
Eric
We have a motorsailer in which I prefer to sail rather than motor. The mast and cutter rig sail area is, at best, modest, but one benefit is that we can carry more sail at higher wind speeds for longer periods without feeling overwhelmed or overcanvassed. To be honest, we’ve yet to test that in in offshore wave heights, however. My experience of pointing ability lessening as the wind is up is also the same as yours.
Hi Andy,
Wonderful articles. Thanks for helping all of us to be up to speed on new rigging possibilities.
I am curious what the insurance company’s have to say to owners who have gone in this direction. Any feedback as yet?
My best, Dick Stevenson, s/v Alchemy
Hey Andy,
Another good read, we too have a picture of my Michelle holding a 47′ boats entire rigging, sans the head stays which are cable for furlers, in her arms. Very cool considering we had to load the old wire onto a pallet to put it in the truck!
https://www.instagram.com/p/BJddb2ijCyj/
Maybe we will see you guys in the Caribbean this coming season. We’re finishing the last of our refit.
Regards,
Ronnie
For those of you concerned with the aerodynamic drag of different rig factors, such as size of rigging numbers of spreaders etc. There is a lot of real world knowledge and theoretical research put into the ORC – Velocity Prediction Program used in the ORC racing rules. You will find the formulas on page 55 in the link below (they are way beyond my pay grade, so no guarantees given).
http://orc.org/rules/ORC%20VPP%20Documentation%202016.pdf
This is of course intended for racing yachts, but as laws of physics are the same, there should be useful information there. If the post is to far away from the long distance cruising core of the site, I apologies in advance.
Good article Andy,
Being a old paragliding pilot I like the solution to use line/rope instead of wire.
But how is the sound in the rigg at anchor in strong wind?
Heard rumers of a high pitching sound.
On a racing machine this is no problem but on a crusing boat could be a problem.
Regards,
Peter
Hi Peter,
That’s a valid point. Some years ago we changed our running backstays from wire to high modulus rope. Generally it was a great change: lighter and easier to handle. The downside is that they hum horribly when tight and the wind is light. We can ameliorate this a bit with shock cords strung between said runners and the cap-shrouds, but it can still drive us crazy. A whole rig humming in the same way would be truly horrible.
Hi Peter,
We also have a split Dynema backstay and have experienced resonance similar to “a not too distant chain saw” in anything over 20 knots apparent, which for us up-wind is about 13 knots true. The stays terminate on brackets that bolt to the aft hull forming part of two large lazarettes that act as giant base speakers! For us, it got even worse as the wind strengthened / we wound on the backstay with the backstay ram. However we have solved this at anchor or under-way completely, by using the backstay legs as bracing for our new Bimini and using small turning blocks, which I commented on here: https://www.morganscloud.com/2016/10/15/a-sailors-cockpit-enclosure-part-2/
Based on this experience I would support John’s comments and wouldn’t consider replacing the rest of our rigging until the industry introduces a new synthetic rope, no thicker than wire and with a smooth, noiseless, abrasion resistant outer cover. Next year perhaps?
Rob
I have not experienced Dynex Dux rigging making overly loud noises when it is windy. I hear the wind howling through the rigging when it is windy, but not a high pitched sound. I don’t think it has been any noisier than wire rigging, and certainly less noisy than the wind generator. I wound electrical tape over the Dux to shield it from UV–I suppose it is possible the smooth surface of the tape makes a difference in wind noise.
My experience with Dynex Dux started in 2009 when I used it to rerig my Damien II staysail schooner, Issuma. That was early, and I have the scars to prove it :). At the time, I had never unstepped the masts, and didn’t understand just how heavily built they were (so how minor a weight change aloft resulted from changing from wire to Dux).
I’ve since gone back to wire (less expensive, well understood) for the most part. Now only the checkstays (covered in hose where the sails rub against them) are Dux. On a boat with a lighter mast(s), and spreaders with ends better able to handle larger diameter shrouds, I might be more interested in Dux than I am on my current boat.
Hi All,
Just so you are aware, Andy went to sea today in the Caribbean 1500 and so won’t be up in the comments for a couple of weeks.
Would you consider Dynice Dux for a shoreline tie up? Can you reliably tie it off to a deck cleat?
It floats and is a lot easier to handle than fat polypropylene but a lot more expensive.
Put some chafe guard on as required of course.
David
Hi David,
No, I would not use Dux for shorefasts. Overkill to my way of thinking. We use ordinary commercial spectra. More here: https://www.morganscloud.com/2010/06/27/shorefast-systems/
This article and part one were quite informative.
One question I have wondered about is the UV resistance of the rope used for lashing the ends (terminators). From the picture, I think you’re using Amsteel for that. Is there a recommended replacement interval for the lashing line due to UV exposure?
Has anyone considered lightning strikes and dux? Seems to me the heat could easily melt the lines and you probably wouldn’t get the protection of a Faraday cage.
Hi Gino,
Good point, classic example of an unknown-unknown, at least until you pointed it out; now it’s a known-unknown.
Judging by the very low melting point (~130 C / 266 F), this might be an issue, although the heat from a lightning strike would probably not attack the fibre directly as it is not conductive at all. I would suppose the mast terminals might be affected if the mast heats up due to a strike.
Wikipedia has this to say:
“The weak bonding between olefin molecules allows local thermal excitations to disrupt the crystalline order of a given chain piece-by-piece, giving it much poorer heat resistance than other high-strength fibers. Its melting point is around 130 to 136 °C (266 to 277 °F), and, according to DSM, it is not advisable to use UHMWPE fibres at temperatures exceeding 80 to 100 °C (176 to 212 °F) for long periods of time. It becomes brittle at temperatures below −150 °C (−240 °F).”
Ultra-high-molecular-weight polyethylene – Wikipedia