Main Trimming (new) hijack avoidance...
- Thread starter rgranger
- Start date
I like your arrangement, but I'm not clear on why it's better than the "notoriously inefficient" Crosby rig - which I believe is the arrangement I was promoting above (and which virtually the entire ~8200-strong Albacore fleet uses).
In our arrangement, the control end of the sheet is led forward along the boom to a mid-boom block, then down to a ratchet block (and a seldom-used cleat) in the cockpit.
To me, having an extra multi purchase mainsheet dragging in the water on a broad reach or run seems inefficient, and I don't see much inefficiency in the single sheet with split "tails".
Please explain.
I do understand how your two sheets could replace a traveler AND obviate the need for a vang when the boom is anywhere between the gunwales. But the split bridle does the first job when used with a vang, and a vang is needed when the boom is outside the gunwales, regardless, so I see no disadvantage in using it to tighten the leech when close-hauled.
Am I missing something?
In our arrangement, the control end of the sheet is led forward along the boom to a mid-boom block, then down to a ratchet block (and a seldom-used cleat) in the cockpit.
To me, having an extra multi purchase mainsheet dragging in the water on a broad reach or run seems inefficient, and I don't see much inefficiency in the single sheet with split "tails".
Please explain.
I do understand how your two sheets could replace a traveler AND obviate the need for a vang when the boom is anywhere between the gunwales. But the split bridle does the first job when used with a vang, and a vang is needed when the boom is outside the gunwales, regardless, so I see no disadvantage in using it to tighten the leech when close-hauled.
Am I missing something?
HEINZIR
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- Jan 22, 2008
- 198
HEINZIR
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- Jan 22, 2008
- 198
It's more likely me that is missing something. Maybe my nomenclature is wrong. I had always thought the Crosby rig was a single line main sheet that started at a padeye on one corner of the stern, went up through a double block on the boom, down to a turning block on the other stern corner, back up through the other sheave on the boom and down to a cam cleat near the point of origin. This is what my boat came with as did many other non-performance oriented trailer sailors.
Your rig, as I understand it, is far superior to this. I was comparing mine to the original rig, not yours.
I first saw an arrangement like yours on a Montgomery 17 at the Havasu convention. All of the other M17s used a conventional traveller. I asked the skipper of this boat about it. He said he copied it from the Snipe class and that it gives him all the control he needs with a minimum of extraneous lines. I took what he said seriously since he is always at the top of his fleet. I considered converting Chiquita's main to this arrangement but decided that what I had was working ok for me.
Your rig, as I understand it, is far superior to this. I was comparing mine to the original rig, not yours.
I first saw an arrangement like yours on a Montgomery 17 at the Havasu convention. All of the other M17s used a conventional traveller. I asked the skipper of this boat about it. He said he copied it from the Snipe class and that it gives him all the control he needs with a minimum of extraneous lines. I took what he said seriously since he is always at the top of his fleet. I considered converting Chiquita's main to this arrangement but decided that what I had was working ok for me.
The name Crosby is new to me, but the Internet agrees with your description, and I think that's a reasonable way to adapt my dinghy rig to a bigger boat that needs more mechanical advantage to pull in a bigger boom.
Again, I don't see anything inefficient about it. As long as everything runs smoothly (high-tech lines and blocks), I'd expect it to work well and produce good sheeting angles - similar to your double mainsheet, but more simply and automatically.
Adding "my" forward (mid-boom) cockpit block (& cleat) adds a bit of purchase and forward sheeting, but doesn't really change much, AFAICS.
Again, I don't see anything inefficient about it. As long as everything runs smoothly (high-tech lines and blocks), I'd expect it to work well and produce good sheeting angles - similar to your double mainsheet, but more simply and automatically.
Adding "my" forward (mid-boom) cockpit block (& cleat) adds a bit of purchase and forward sheeting, but doesn't really change much, AFAICS.
I have owned two Mac V21 sailboats and a Mac V22-2. Both had the set up you described. It really did not work terribly well.
HEINZIR
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- Jan 22, 2008
- 198
If I understand your rig correctly there is a world of difference between your arrangement and the Crosby rig. Here are a couple of pictures of a Montgomery 17 rigged similarly to your boat as I understand it. The two legs of the bridle are spliced into a single main sheet that runs forward along the boom. The 3 single blocks near the middle of the boom are to increase the purchase to 4:1. The strap connecting the middle block to the cockpit sole is just to minimize the amount of line that has to be pulled in when coming off a run or reach.
When the main sheet is hardened up the windward leg of the bridle carries the load while the leeward leg is slack. This allows the boom to be pulled up to the centerline without pulling it down too much and taking the twist out of the sail.
The effect of tightening the main sheet on the Crosby rig, however, is just the (unwanted) opposite. Because the windward legs of the bridle are connected to the leeward legs through the double block on the boom, the forces are equalized. The leeward side does not go slack; it carries the same tension as the windward side. The result is that there is as much or more force pulling down on the boom as there is pulling it in, destroying sail shape. I'm no expert on sail trim by any measure but I do know that there are times you do want twist in the main and there are times you don't. With the Crosby rig you have no choice.
Notoriously inefficient, yes! The Crosby rig, that is, not yours.
ANY mainsheeet system with a true boom end attachment will be vastly less efficient if the lines leading from the boom end do not lead straight down. Most high performance boats will have rigs (and therefor the boom) that span the whole boat. In that second pic the boom ends well before the transom, and creates that very inefficient angle for the sheet.
I do have to say however, that that is by far the most tricked out M17 I have ever seen.
@Jackdaw, I agree that any FORE-&-AFT angle in the mainsheet will be inefficient, because the boom can't and shouldn't slide fore or aft. But Port/Starboard windward/Leeward) angles are MORE efficient than vertical sheets, since the sheet's job is to pull the boom to windward, to the centerline.
@HEINZIR, you're right, and I see it now! So the Crosby rig is apparently a failed attempt to capture the advantages of a sailing/racing dinghy's split-tailed mainsheet while adding more purchase (mechanical advantage) for bigger mainsails.
So, the question is whether there is, or can be, a SUCCESSFUL attempt! I think I've got one in my head, just offhand: Start with a "Y" spliced mainsheet. (Albacores used to use a standard double-braid Dacron rope with the core pulled out at the "Y", the inside braid going one way and the outside braid going the other way. The "Y" needs to be seized/whipped. Now we mostly splice thin high-tech tails into a thicker base, sometimes all of it non-absorbent $$$ stuff.)
Start with a block and cleat mid-boom and mid-cockpit, with an appropriate purchase. (Much less purchase will be needed than for pure mid-boom sheeting, because downward tension is neither needed nor wanted. The last few degree to the middle will be done by the windward tail.) The sheet goes aft along the boom to a swivel block at the boom end, which also has a pad eye on each side/bottom. Each tail is led straight outboard to a block on the gunwale/sheer, then back to the same-side eye on the boom end, where it ends.
With our simpler dinghy rig, the "Y" splice is positioned so it just barely enters the boom block with the boom centered and high (close-hauled, open leach). With tight vang, the tails run farther forward along the boom. (Boats with thicker tails and smaller (non-swivel) boom-end blocks can experience scary tangles between the loose tail and the tight one.) But I think that WON'T work off the wind with 2:1 tails. But my pre-coffee brain is hurting now, and I need a diagram or a model! For sure, I think it works if the split tails can go far into the boom, though things get messy if they reach the forward (mid-)boom block, or worse, the cockpit block.
And like any keelboat mainsheet that connects at boom end AND mid-boom, this will be a challenge for canvas cockpit enclosures.
Whether or not I've solved this problem with 5 minutes' thought, I can't believe that human ingenuity can't do it, without the complexity of twin mainsheets. But my 5 minutes has made me fonder of the twin-sheet solution than I was at first!
@HEINZIR, you're right, and I see it now! So the Crosby rig is apparently a failed attempt to capture the advantages of a sailing/racing dinghy's split-tailed mainsheet while adding more purchase (mechanical advantage) for bigger mainsails.
So, the question is whether there is, or can be, a SUCCESSFUL attempt! I think I've got one in my head, just offhand: Start with a "Y" spliced mainsheet. (Albacores used to use a standard double-braid Dacron rope with the core pulled out at the "Y", the inside braid going one way and the outside braid going the other way. The "Y" needs to be seized/whipped. Now we mostly splice thin high-tech tails into a thicker base, sometimes all of it non-absorbent $$$ stuff.)
Start with a block and cleat mid-boom and mid-cockpit, with an appropriate purchase. (Much less purchase will be needed than for pure mid-boom sheeting, because downward tension is neither needed nor wanted. The last few degree to the middle will be done by the windward tail.) The sheet goes aft along the boom to a swivel block at the boom end, which also has a pad eye on each side/bottom. Each tail is led straight outboard to a block on the gunwale/sheer, then back to the same-side eye on the boom end, where it ends.
With our simpler dinghy rig, the "Y" splice is positioned so it just barely enters the boom block with the boom centered and high (close-hauled, open leach). With tight vang, the tails run farther forward along the boom. (Boats with thicker tails and smaller (non-swivel) boom-end blocks can experience scary tangles between the loose tail and the tight one.) But I think that WON'T work off the wind with 2:1 tails. But my pre-coffee brain is hurting now, and I need a diagram or a model! For sure, I think it works if the split tails can go far into the boom, though things get messy if they reach the forward (mid-)boom block, or worse, the cockpit block.
And like any keelboat mainsheet that connects at boom end AND mid-boom, this will be a challenge for canvas cockpit enclosures.
Whether or not I've solved this problem with 5 minutes' thought, I can't believe that human ingenuity can't do it, without the complexity of twin mainsheets. But my 5 minutes has made me fonder of the twin-sheet solution than I was at first!
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I have some observations based on a poorly designed boat I used to sail, that had mid-boom sheeting. What I observed was, that as the wind increased, the boom will actually move to windward and raise up, following the arc of the sheet. The stronger the wind, the greater tendency the boom had to move windward and raise up. (the rig had no vang, so this characteristic was obvious) So, I think when you actually are adjusting twist with the traveler, you are adjusting how much the boom is raised for a given wind load. If the wind is light, you need a lot of sheeting angle to allow the boom to raise easily. If the wind is heavy, you need less sheeting angle. Makes sense so far? Now, the point of the boom, where the sheet is attached will determine how much wind load it takes to raise the boom. End boom sheeting takes a lot of wind load to raise the boom. Mid-boom sheeting takes very little wind load to raise the boom. This point is critical. Mid-boom sheeting takes very little wind to raise the boom. Since the boom raises easily, that gives the boom vang a greater range of adjustment. My conclusion is that mid-boom sheeting greatly reduces the need for a traveler, as it increases the useful range of the boom vang. Can you get the boom centered? No, but it will come really close.
I think this is why you see arguments questioning how necessary a main sheet traveler is. Its going to depend on the attachment point on the boom, compared to the power of the sail. Is it the best? No, but you can get close.
I think this is why you see arguments questioning how necessary a main sheet traveler is. Its going to depend on the attachment point on the boom, compared to the power of the sail. Is it the best? No, but you can get close.
Okay; I am lost. I don't understand what Weinie means by saying that the traveler has to be slacked-off and hardened-up every tack. I've never done that. Going through the wind repeatedly, you just leave both blocks where they are and keep the tacks at the same angle (current, etc., withstanding). This is the 'famous' problem of having all the tackle formerly to windward become a tangled disaster as the traveler car comes crashing down to the extent of the now-windward tackle; but that's part of the fun.
I have known many people having those dual vangs for mainsheet tackle like Heinzer has. I've sailed with a few of them. It's about the closest thing to having the control of a traveler; but it's done in a very different way. I find it no less awkward than what people say about adjustable travelers-- you have to remember to slack one before you go round or else you find the boom hung-up as you assume the new tack and then have to remedy it while the load is on. And when slacking it off before you go round, you are affecting your then-current tack. Sorry; I don't buy it.
I agree with Jackdaw and the rest who say the traveler is one of the key elements to efficient sail trim; and I wouldn't have a boat without one. At Cherubini I fought against the (rather opinionated) contractor next door who insisted the mizzen on a C44 doesn't need the traveler I spec'ed out on those boats since 1980. He's a one-design sailor who's clearly never sailed a double-headsail ketch under mizzen and inner staysail in gnarly weather, when the mizzen becomes your mainsail, etc. If it's on the boat, it ought to be used and used well. Given the traveler, it's easy enough to learn how to use it. But, no; I won't brook the argument that, not having one, wishful thinking can make your non-traveler setup as good as a traveler one.
'Two identical boats, one with traveler one without. Both sailed as optimally as possible, the traveler boat will crush the non-traveler boat upwind.' = agreed.
I have known many people having those dual vangs for mainsheet tackle like Heinzer has. I've sailed with a few of them. It's about the closest thing to having the control of a traveler; but it's done in a very different way. I find it no less awkward than what people say about adjustable travelers-- you have to remember to slack one before you go round or else you find the boom hung-up as you assume the new tack and then have to remedy it while the load is on. And when slacking it off before you go round, you are affecting your then-current tack. Sorry; I don't buy it.
I agree with Jackdaw and the rest who say the traveler is one of the key elements to efficient sail trim; and I wouldn't have a boat without one. At Cherubini I fought against the (rather opinionated) contractor next door who insisted the mizzen on a C44 doesn't need the traveler I spec'ed out on those boats since 1980. He's a one-design sailor who's clearly never sailed a double-headsail ketch under mizzen and inner staysail in gnarly weather, when the mizzen becomes your mainsail, etc. If it's on the boat, it ought to be used and used well. Given the traveler, it's easy enough to learn how to use it. But, no; I won't brook the argument that, not having one, wishful thinking can make your non-traveler setup as good as a traveler one.
'Two identical boats, one with traveler one without. Both sailed as optimally as possible, the traveler boat will crush the non-traveler boat upwind.' = agreed.
@Diana/JohnC and everybody else who proclaims the superiority of travelers, all I can offer is a competing principle: "When your theory conflicts with facts, it's not the facts that are wrong!"
My dinghy fleet (15' Albacores, in Toronto and internationally) has tested the theory over many years and many regattas, and has abandoned travelers in favor of split-bridled mainsheets and powerful vangs - because that's what wins races.
It's conceivable that the greater scale of a big keelboat creates scaling problems that smart humans can't solve, so a traveler is still the best/fastest compromise. But I still have hope that human ingenuity will be able to optimize a larger rig, too.
My dinghy fleet (15' Albacores, in Toronto and internationally) has tested the theory over many years and many regattas, and has abandoned travelers in favor of split-bridled mainsheets and powerful vangs - because that's what wins races.
It's conceivable that the greater scale of a big keelboat creates scaling problems that smart humans can't solve, so a traveler is still the best/fastest compromise. But I still have hope that human ingenuity will be able to optimize a larger rig, too.
How true.. In engineering classes; a sure sign you were dealing with a freshman... when they positioned a theory they just read about vs well-founded empirical evidence! ;^)
Yes, agreed. I don't pretend to have invented a solution. And if you insert a big block and tackle mid-boom, connected to a single split bridle, the bridles won't have much effect.A split bridle setup with a 4:1/6:1 combination mainsheet seems like a lot of work.
Well this has certainly turned into a very educational thread. I want to thank everyone for their contributions.
For my boat, it looks like something like this
will be the best new toy to add.... however when I contacted the manufacturer, the sticker price made me want to wet myself. However, it does not look hard to make one from some T-track and blocks. So... next project... well actually next on the growing list...
"The only thing that works on an old boat is the skipper"
For my boat, it looks like something like this
will be the best new toy to add.... however when I contacted the manufacturer, the sticker price made me want to wet myself. However, it does not look hard to make one from some T-track and blocks. So... next project... well actually next on the growing list...
"The only thing that works on an old boat is the skipper"
Looking at the picture, this setup could take advantage of the 4:1/6:1 solution, here's a way to do it with a block that Guido at Garhauer made for a couple of us.
https://meriachee.wordpress.com/2014/08/01/archimedes-palimpsest/
https://meriachee.wordpress.com/2014/08/01/archimedes-palimpsest/
Yeah, apparently I can't type. (Or add today either according to my expense statement)