Designing For Dux Rope Rigging—A Paradigm Shift—Part 2
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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