Could you install double sets of stays and shrouds?

[GrahamHO]

Originally Posted by Jman

Agree with everything you say, except compression. A loaded running back straightens the mast, increasing compression. You could say it it greatly reduces mast bend. They are there on your fractional rig specifically to put more tension on the head stay.


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No my runners are not primarily to tension my forestay. That is the purpose of runners that attach near the middle of the transom on a rig with inline spreaders. I've several times been a passenger on different Americas Cup monohulls during training and stood very close to that type in action.

My much smaller yacht has swept back spreaders and runners attached to the stern quarter. My qualified engineer mast supplier suggested that they reduce mast compression.

You can see this yourself if you imagine a theoretical runner that went back horizontally to infinity. It would directly oppose the load without compressing the mast as much as a shroud on the usual 10* minimum angle to the mast. Check out a parrellogram of forces.

[GrahamHO]

Originally Posted by Blue Stocking

Saw a large cutter with dual fore'n'aft headstays, 3" apart. Bell-cranked at stem, with 1 turnbuckled, self-equalising tensioner.

Yes that's a good method but the two wires in tension are possibly stronger than the pivot arrangement which is trying to bend the bell crank and sheer the pivot pin. There is still a weak link in the chain. Good for sliding up and down different hanked on sails or going wing and wing.

[Don C L]

Originally Posted by GILow

Yes, this describes our rig. And the bit that slightly bothers me is that with all this reinforcing the ONLY bit that is not duplicated in any fashion is the rear stay. And when we run under MPS I am quite concerned with strain the rear stay must be under.


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I too have seen heavy boats rigged with dual forestays and backstays, but not dual shrouds. Better to just go up in size on the shrouds and beef up all attending fittings. It was my understanding that the major advantage to dual forestays, or headstays, was not so much for strength but to allow for a heavy jib to be hanked on and available at all times, or to rig two headsails wing and wing for easy downwind sailing, with sheets possibly run to tiller for self-steering.

[GrahamHO]

Originally Posted by Don C L

I too have seen heavy boats rigged with dual forestays and backstays, but not dual shrouds. Better to just go up in size on the shrouds and beef up all attending fittings. It was my understanding that the major advantage to dual forestays, or headstays, was not so much for strength but to allow for a heavy jib to be hanked on and available at all times, or to rig two headsails wing and wing for easy downwind sailing, with sheets possibly run to tiller for self-steering.

Exactly. However better as heavier shrouds might be they still need to be attached to the mast and chainplates. That will require larger clevis pins which require larger holes which will weaken the fittings and or the mast.

If all that is engineered from the start it might be OK but then someone will want to upsize that version not believing the designer who originally made all the calculations.

Two keels, two rudders (I know it's done), two engines thicker hull. Where do you stop?

[Jman]

Originally Posted by GrahamHO

No my runners are not primarily to tension my forestay. That is the purpose of runners that attach near the middle of the transom on a rig with inline spreaders. I've several times been a passenger on different Americas Cup monohulls during training and stood very close to that type in action.



My much smaller yacht has swept back spreaders and runners attached to the stern quarter. My qualified engineer mast supplier suggested that they reduce mast compression.



You can see this yourself if you imagine a theoretical runner that went back horizontally to infinity. It would directly oppose the load without compressing the mast as much as a shroud on the usual 10* minimum angle to the mast. Check out a parrellogram of forces.

Of course, but I assume your boat is not infinitely long, or for that matter wide. By putting them on the quarter your are changing the angle by what? 2 degrees, 5 degrees? (if you have a cat don't bother reading on). So why are they there at all? Just as backup?

I have actually long distance ocean raced on boats with with running backs in several configurations, not stood on a boat being raced by others. So let's start:
1. You have a multi spreader rig with, not fractional, no swept spreaders. Running backs are normally about half way up (or multiple runners for even distribution), mostly run to the quarter. As wind picks up you start with the back stay, jib is still too full and main is way too flat. You put runner on, increase main draft, and reduce jib draft. All the runner does is increase compression by keeping the mast straighter.
2. You have a fractional rig, no swept spreaders. As you apply back stay to reduce jib draft, you very quickly wash the main the main out, so you must put the runners on (depending on the boat they are more important to keeping the mast up than then primary back stay). If you kept going with the back stay, trying to flatten the jib, you would have incredibly mast bend. The running backs are at the hounds to help you control forestay tension. The more tension you put on them, the more you compress the mast. Not unusual in older maxi boat to have the head stay tension gauge at 15,000lbs or more, probably even more on the AC boats you reference.
3. You have a cutter rig, mast head, runners are at the height of the inner forestay. If you reduce sail to the staysail only, back stay is going to actually reduce staysail stay tension, so you have to have runners, again to tension the the staysail stay, and reduce mast loads, but not compression.
4. You have a barely fractional rig (say 7/8th), with swept spreaders. These runners are not so much for mast bend as they are to stop the mast from pumping in waves, normally off the wind, in seas, changing the main trim on each pump. The swept spreaders are acting as running back already. But, every time the mast would have pumped in this scenario, the compression goes up by stopping it.
5. You have your boat. You have not said what the fraction is, and given your first reef puts it at the same height as your hounds, I am thinking 3/4. When engaged, your swept spreaders are already acting as runners, reducing mast bend. Your back stay as you say is just controlling the tip of the mast. So why the runners? We are back to head stay tension, which inversely increases mast compression. Unless you do in fact have an infinitely long and wide boat. They do reduce mast compression vs. having to crank the the back stay to accomplish the same thing.
5. Final scenario, no running backs available, high performance older racing keel boat. Still need to control the mast bend vs. head stay sag. That is why you can adjust the the partners on those boats (or the mast butt position, or both), using the deck as a very low running back stay, and in some cases moving the lower shrouds back a few inches.

In the real world of cruising very few people care about jib draft, and when the wind picks up they just get rid of it, because heel angle is unacceptable to enjoyment. So having the running backs is indeed a good back up, and back to the original discussion you essentially have 2 back stays engaged, which is certainly more robust than one.




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[GrahamHO]

Originally Posted by Jman

Of course, but I assume your boat is not infinitely long, or for that matter wide. By putting them on the quarter your are changing the angle by what? 2 degrees, 5 degrees? (if you have a cat don't bother reading on). So why are they there at all? Just as backup?

I have actually long distance ocean raced on boats with with running backs in several configurations, not stood on a boat being raced by others. So let's start:
1. You have a multi spreader rig with, not fractional, no swept spreaders. Running backs are normally about half way up (or multiple runners for even distribution), mostly run to the quarter. As wind picks up you start with the back stay, jib is still too full and main is way too flat. You put runner on, increase main draft, and reduce jib draft. All the runner does is increase compression by keeping the mast straighter.
2. You have a fractional rig, no swept spreaders. As you apply back stay to reduce jib draft, you very quickly wash the main the main out, so you must put the runners on (depending on the boat they are more important to keeping the mast up than then primary back stay). If you kept going with the back stay, trying to flatten the jib, you would have incredibly mast bend. The running backs are at the hounds to help you control forestay tension. The more tension you put on them, the more you compress the mast. Not unusual in older maxi boat to have the head stay tension gauge at 15,000lbs or more, probably even more on the AC boats you reference.
3. You have a cutter rig, mast head, runners are at the height of the inner forestay. If you reduce sail to the staysail only, back stay is going to actually reduce staysail stay tension, so you have to have runners, again to tension the the staysail stay, and reduce mast loads, but not compression.
4. You have a barely fractional rig (say 7/8th), with swept spreaders. These runners are not so much for mast bend as they are to stop the mast from pumping in waves, normally off the wind, in seas, changing the main trim on each pump. The swept spreaders are acting as running back already. But, every time the mast would have pumped in this scenario, the compression goes up by stopping it.
5. You have your boat. You have not said what the fraction is, and given your first reef puts it at the same height as your hounds, I am thinking 3/4. When engaged, your swept spreaders are already acting as runners, reducing mast bend. Your back stay as you say is just controlling the tip of the mast. So why the runners? We are back to head stay tension, which inversely increases mast compression. Unless you do in fact have an infinitely long and wide boat. They do reduce mast compression vs. having to crank the the back stay to accomplish the same thing.
5. Final scenario, no running backs available, high performance older racing keel boat. Still need to control the mast bend vs. head stay sag. That is why you can adjust the the partners on those boats (or the mast butt position, or both), using the deck as a very low running back stay, and in some cases moving the lower shrouds back a few inches.

In the real world of cruising very few people care about jib draft, and when the wind picks up they just get rid of it, because heel angle is unacceptable to enjoyment. So having the running backs is indeed a good back up, and back to the original discussion you essentially have 2 back stays engaged, which is certainly more robust than one.




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Thanks for that lesson. I'm not sure exactly what you're point is. I've also done a bit of racing though I'm sure not nearly as much as you.

I'm well aware how my double swept back spreader rig works, and it works very well but thanks again for your explanation.

I was giving the example of how theoretically increasing the angle of a stay until it's horizontal reduces compression. If you imagine taking things to the extreme you can better understand. That is called reducto absurdum which I'm sure you can understand means reducing to an absurdity.

My running backstays are only used on a reach with or without an asymmetrical in fresher winds on a long sail. Then I naturally use only the windward one. Also I use 2 with 2 reefs in, both can be on as they clear the sail and boom and don't need to be changed with tacks. It has to be a fairly strong wind for that to happen and it creates a very snug rig.

As the topic was doubling the rigging, I suggest that having a runner system to suit a particular rig can be an option to consider.

It makes little difference what fraction my rig is. In fact it is referred to as 3/4 but its not exactly. So your guess was more or less correct.

A couple of years ago I replaced the chainplates and for a month while I was doing that work the rig was supported only by the runners forming a triangle to the corners of the wide transom, and the forestay. The yacht in its berth of course.

If the runners were the type in line with the forestay I would not have been able to do that. That's not the reason for them but it shows that they add support.

Oh and by the way I have a high aspect bulb keel much smaller but not dissimilar in shape to the afore mentioned AC yachts, though it's certainly not the 20 tons their bulbs are. I changed the keel to a bulb design about 8 years ago. A bulb keel certainly increases the load on the rig which was the reason I upgraded the chainplates. Perhaps all that disqualifies me from being called a cruiser but at 76 I'm happy to cruise and to control the draft in my jib.

[valhalla360]

This discussion reminds me why home built boats often sell for far less.

Rather than building it as the designer intended, they often decide to double up on things when the designer already calculated what is needed.

[Terra Nova]

Doubling up on every rigging component is no guaranty that your rig won't come down. But it will guaranty that your boat will sail more poorly.

[GrahamHO]

Originally Posted by valhalla360

This discussion reminds me why home built boats often sell for far less.

Rather than building it as the designer intended, they often decide to double up on things when the designer already calculated what is needed.

My original designer approved and recommended fitting runners. My replacement keel was designed for me by another very experienced designer, as bulb keels had developed since my yacht was built. It has been very successful.

I have read interviews with designers who say that after they have done all the calculations people change things like mast height or thickness of hulls. 50% thicker hull makes the hull 50% heavier. A taller mast decreases the shroud angle etc etc. With a good design all things work together.

[er9]

Originally Posted by UNCIVILIZED

What you're inquiring about has actually been done, many times, on a whole bunch of different boat designs. Usually by folks new to sailing, & who wan't "bulletproof" rigs. It's not as tough as many here make it sound, & 150yrs ago, it was kind of common practice.

Also I've seen a few commercial designs where what you're proposing was done, or real close to it. And because of the extra windage, when a breeze as stiff as all of 25kts would kick up, he'd heel over 10-15 degrees in his slip.
In case you're curious, it was a Hans Christian design.

The weak points of any rig, generally speaking, are the end points of the wire; where it enters into the terminal fittings, & the various end fittings connecting things together. Such is the case even with Rod.
That's where say, 98%+ of all failures occur.

One rig design which will intrigue you, as it's kind of along the lines of what you're thinking, is the B&R rig (Bergstrom & Ridder). There's not exactly an encyclopedia of info about them out there, but the design's both unique, & has a lot going for it.
- Enough so that Hunter, de-tuned it a bit, & put it on several lines of their boats.

In theory, it has; more performance for less weight aloft, & redundancy in rigging wires... plus a bit more tuneability in one's rig.
Look up the vessels; Route 66, Tuesday's Child (or maybe Thursday's), the Hunter HC 50, & you'll also run across the name Warren Luhrs in conjunction with many of these. Also, there's info on such in the Dashew's book, below.

Do yourself a favor, & pick up copies of:
Brion Toss's The Rigger's Apprentice
The Dashew's Cruising Encyclopedia vol. II <-- Get a used copy on Amazon/Ebay/Half.com for 1/2 price.
If you study them well, you'll know more about rigs, rigging, & structures than 99% of the sailors afloat. Including bits on rig design, safety factors, pro's & con's of rig types, & various materials, weight aloft, failure modes inspecting things... et all.
Not to mention sailing in general, & cruising.

They're a bit out of date when it comes to say, synthetic rigging, soft shackles, & the like. But such info is easy to pick up online. Have a look over at www.forums.sailinganarchy.com & www.L-36.com there's LOTS of practical knowledge at the latter. And doing some perusing @ www.bethandevans.com wouldn't hurt either, given their depth of knowledge, & all of the sailing that they've done.

Also, Evans has done a LOT of work with some of the top riggers, & line manufacturers, to come up with KISS methods for using the modern high tech lines for all kinds of mundane uses, formerly reserved for pricey metal fittings & such alone.


PS: When it comes to doubling up on shrouds, it's not Too uncommon, to see 2 cap shrouds per side, & double lowers (fore & aft leading). As these are the 2 places, generally speaking, which get the highest side loadings on the rig. And which the rig will, without question, fail, if they do.
Look at boats designed for expeditioning, especially at the extreme ends of the spectrum, latitude wise.

Wow! thank you for the wealth of information. lots to absorb there. thats all going to keep me busy for a while.

[er9]

Originally Posted by Jman

If you are so concerned the the designer failed at the load potential, then:
1. Don't buy that boat.
2. Way increase the size the size of the stays, you don't even need to double it is diameter to get twice the strength, now you have eliminated stay failure.

And where is the weak point? as many have said, drill more holes in the mast, not if the mast or spreaders were the weak point all along, or would become so with additional holes. Chain plate failure may even be more common than stay failure, was that the weak point?

If two sets are of stays are better than one, then why not 4? Or 8? Well if we were all sailing around with guitar string rigging maybe it would could get a good band going?


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i think you over assumed my intent. this has nothing to do with any particular boat or hardware.

lets be realistic. just about everything made today and in the past is about making money. sailboats are no different. the designers and builders are not intent on making the most durable sailing vessel ever to float on the ocean. they get their calculators out, reference a few formulas and design a capable and relatively safe product.

now there are men like me who want the most capable, most durable, safest (sailboat in this case), so my life is not wasted in the middle of the indian ocean because i was willing to settle for some other mans idea of whats good enough.

ok so i'm being overly dramatic to make a point, which is...what are the possibilities? what can i do better?

i know there are no guarantees. you could try and make the safest, most durable airplane ever to exist and a bird in the engine could end it all. but no harm in trying...except probably to my wallet.

anyways so far i really appreciate the replies. some really good information and experiences. its that discussion that defines the possibilities. much thanks...

[er9]

Originally Posted by Snowpetrel

Look at the crash test boat series on YouTube. Check out the dismasting video


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ha thanks. i love those video's. havn't seen that one yet.