Split Tail Mainsheet Options

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Split Tail Mainsheet Options

Postby DigitalMechanic » Sun Oct 01, 2017 11:34 am

I previously mentioned rigging a split tail mainsheet up on the boat. Without getting into crosby vs mid-boom vs split tail vs RYO hybrids, etc... I created a couple of drawings (with parts and pricing) to see what kind of feedback I would get. I know little about this design, but from research I have found a couple of ways I could come up with to do it, each getting more and more complex/expensive. I am curious to the benefits to each, and/or point of diminishing returns, particularly on the the Daysailer. Please excuse my Photoshop skills, as these were quick sketches. Hopefully they are easy to follow.

Design 1 - Mike Gillums Split Tail (Golden Standard?)

I am assuming that the purchase here is 1:1, and Mike uses a double ratchet system. One auto-ratchet on the boom, and one manual ratchet on the swivel base that can be turned on or off depending on wind/conditions. I currently have a 3:1 (roughly 25ft of line in the purchase). Mike's design seems to cut down on line at the cost of needing more muscle in the wind, at least to sheet in, and maybe sheeting out can have a loss of precision at times (I think this is what the double ratchets solve)?
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Sun Oct 01, 2017 11:40 am

Design 2: Adding Purchase

Here I think that I have added a way to bring it back to 3:1 or there about. At any rate there is definitely more sheet added, thus more purchase added. Again, keeping the auto ratchet on the boom and manual ratchet on the base. However, would a double ratchet system be beyond the point of diminishing returns with this much purchase? Mike seems to think that double ratchet system is valuable, and I believe that it may be, but only on heavy conditions. I know that my current 3:1 w/ just an auto ratchet seems to be fine to me most of the time. However, the days when we get heavy wind, holding the sheet in hand for long periods can get tiring. I think I can see the value, but ratchets are so expensive...
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Sun Oct 01, 2017 11:47 am

Design 3: Purchase Plus Adjustable Tails

I have seen this on other boats (IE Albacore, Snipe) something called an "Augie Equalizer" used. It is hard for me to follow in pictures and understand, but what it appears to be is an adjustable tail setup. My sketch may be way off. But keeping it simple, I just added stand up blocks and cleats to the aft end of the gunwales. For racing however, I imagine that these would need to be rigged so they could be grabbed from a hiking position, thus massively complicating rigging (drilling holes in the boat to get things back to center, etc). Anyway, without getting the rigging perfected, I am curious what value an adjustable tail may provide on a boat like ours? Again... point of diminishing returns? Just curious about the value of adjustability here? Apparently the other guys think it is of value?
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Re: Split Tail Mainsheet Options

Postby GreenLake » Mon Oct 02, 2017 1:19 am

Very nice summary.

I have a modified combination of the first and last scenario on a 15ft dinghy. A single ratchet (manual) at the bottom and instead of the tails being individually adjustable they are tied together and then that knot can be pulled on for some added tension.

That's a setup that I'm unfortunately not able to evaluate for you because I have not mastered that boat to where I can truly sail it to its capabilities. (I simply prefer the DS and that means I'm not spending enough time on the other boat).

On my DS I have more purchase than your scenario 1 - if I wanted to get the same purchase but using split tails I would need to take your Design 1 and add a 2:1 cascade. While that's not practical (you don't want a floating block hanging under the boom and the range would be limited to the length of the cascade (about 5', which is not enough to let the boom come forward) it tells me that my overall purchase is better by a factor of two than your Design 1.

To me, that amount of purchase feels about right (and my sailing conditions tend to be a tad more on the moderate side, but it handles well on the occasional days where I play it by hand in 20+ gusts. Incidentally, I make do with a single ratchet block, but one that that's rated as exceeding the competition's holding power by about a factor or two in some independent test by a technical sailing magazine. I also rely exclusively on the auto setting and never had any reason to change that - it simply knows when to disengage.

I've made some changes in my traveler setup and can't tell that they seem to have brought "big" changes - I lack the like-for-like comparison with another DaySailer. Barber inhauls were another matter. Their effects were directly observable.

I'm as curious as you to hear what any other, more expert DS sailors have as comments on your Designs.
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Mon Oct 02, 2017 8:31 am

GreenLake wrote:...instead of the tails being individually adjustable they are tied together and then that knot can be pulled on for some added tension.


That seems to be what I have seen as well. I think it has to do with getting things back to the center of the boat, so they can be reached from either side? Ussually setup on a smaller dinghy where everything is inherently close. If you really want to make your brain hurt, try and follow this on a little bit bigger boat, look at how a Melges Scow is rigged. They have a traditional traveler (on a rail) across the transom, that is adjustable from either side of the boat. It is rigged in some magical way "through hull" that allows adjustment from either side of the boat.

Anyway, I understand the technical value of the adjustable traveler on a Scow (the way it is rigged). But I am curious of what technical value this adjustability of the tail provides when rigged as a split tail main. Like I said, I have little knowledge of this setup, but my intuition tells me that the split tail is all about getting the best centering of the boom, without the traditional traveler on a sliding rail. With a traveler on a rail, you could go as far as to "hook" the boom to windward in light air to get a little extra. Maybe you can do this with the split tail if it is adjustable? But then would you not be pulling the boom down to far for a "light" breeze, which defeats one of the values of the design. I think one of the main reasons the split tail is used is to get good centering of the boom in light winds, without pulling it down so far... allotting a little more power. Just thinking out loud here...
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Mon Oct 02, 2017 9:14 am

GreenLake wrote:I've made some changes in my traveler setup and can't tell that they seem to have brought "big" changes - I lack the like-for-like comparison with another DaySailer. Barber inhauls were another matter. Their effects were directly observable.


If I had to guess, I think that all of this goes hand in hand, and one compliments the other to some degree. For example when we modify cars (people seem to understand them better), and someone puts an aftermarket muffler in, they will often be disappointed when they do not get an extra 20 horsepower that the manufacturer is claiming they will get. Yes, it sounds cool, but that is about it. The reality is that you have not changed anything about the exhaust. From a simplistic view without all the technical details, you cannot change the performance of the exhaust to any significant degree without changing the entire "system of flow" out. You have to change every part that the air flows through. This means the intake, air manifold, exhaust manifolds or headers, the mid pipes, the catback, muffler(s), tailpipes, etc. Once you do all of that, now you have affectively changed the rate at which the air pump (engine) can flow. I will leave that there, as this is not a car forum, but the point is that there are a lot of modifications that are all necessary to provide the maximum performance compliment to one another.

When we are talking about barber haulers and split tail main sheets etc, specifically on the Daysailer, I believe (and correct me if I am wrong) we are talking about getting the boat to sail better closer to the wind. At least for the most part. The way I am seeing it, at least in my head... is that the barber haulers allow the foresail to sail better upwind, allowing the boat's foresail to sail potentially closer to the wind. The barber haulers allow the foresail to be sheeted in more than usual. The same should be true for end boom sheeting, particularly the split tail, which is supposed to allow the boom to get closer to centerline. Again, this in theory should allow the main sail to sheet better a little closer to the wind. The split tail allows the mainsail to be sheeted in a little more than usual. If you can sail closer to the wind, then in theory you should be able to turn through it faster, at which point means you are likely to loose less momentum on a tack. Not to mention lessening the delay from the amount of time it takes to perform the tacking maneuver. All should be reduced. In theory all of this translates to faster, which whether racer or not... is fun.

I am no pro, but I think that out of the box, the DS does not sail that close to the wind. It does seem to reach well though.
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Re: Split Tail Mainsheet Options

Postby GreenLake » Mon Oct 02, 2017 4:21 pm

With both sails you have sheeting angle and leech tension.

With the jib, the inhauls directly affect sheeting angle, while the ratio between leech and foot tension is determined by the position of the fairlead on the track.

With a traveler on a track across the cockpit, you could set the leech tension on the main using the sheet, and then adjust the sheeting angle by moving the traveler car.

With a strong vang, you can let the vang take care of the leech tension, letting the sheet control more of the sheeting angle. Particularly as you let out the main, the boom would not rise and thus keep the sail flat. However, you can't effectively pull the boom in once its close to centerline, as the sheet will point down. A split mainsheet and the various triangle configurations that simulate a traveler at the end of the boom will preserve some horizontal pull as the fixed point that the sheet is acting on is the outer block on the transom and no longer the CB trunk fitting.

Incidentally, as you add more purchase between midboom and centerboard, you are degrading the effect of the split tail. The way to think about it: the force in a rope through a purchase is constant, the pull on a block with 180 degree turn is double that force (once for each part going to that block in parallel) -- similar geometrical reasoning gives you the force on a 90 degree block (total force on the block is 140% but force component in the direction of the pull is single).

Now, at the end of the boom, where one end of the split tails takes the load, you get a single part pulling at the end of the boom at 45 degrees to the side and down. Meaning your side force is 70% of the force you expend pulling on the rope. If you add more purchase (design 2) all you do is reduce the force at which you pull. You still get 70% of that force pulling sideways at the end of the boom, but now that's been reduced by the same factor.

More parts go between mid boom and centerboard (up and down at close hauled) and you add all those forces to your leech tension instead of sheeting control.

With a boom vang, you can supply leech tension, and perhaps as a result you'll need a bit less force on the main sheet to bring it in, allowing you to go with Design 1.

As you write, all the pieces work together.

Another element of the system is the centerboard. In order for it to work, the boat has to sail with a certain degree of leeway (difference between course and heading in the absence of current). That leeway provides the CB with an angle of attack.

The DS CB is said to be a bit underdimensioned (and the factory ones have no profile whatsoever). I could imagine that this means there's a limit to how aggressively you can sheet in, compared to other boats. If you haven't already, I would definitely look into getting (or making) a properly foiled CB and rudder.

Some finer points of the trim (and rigging layout) you won't be able to tune without having a like boat for comparison. The effects are real but too small to eyeball or measure with a GPS (as the wind isn't constant, for one).

That said, I claim I noticed a definite effect from the inhauls (if only to make the jib "set" better in certain conditions). I have also noticed some improvement from a partial re-foiling of the CB (most noticeably I was able to eliminate CB hum). I wonder if a fully foiled replacement board would make a difference. Perhaps if I get bored, I'll build one. I did a pretty decent new rudder. It reduced weight at then end of the boat and feels better, but I can't tell whether it would make a difference in boat to boat comparison.

Adding a vang is too recent for me to be conclusive about it, and I'm not sure I know what I'm doing with it yet, but in some conditions I acquit myself quite well in our mixed fleet (where most of the boats have faster ratings).

So, definitely good thinking all of that through; don't know which of these changes is going to be that muffler - i.e. something that pays off once you make other changes.
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Mon Oct 02, 2017 8:41 pm

GreenLake wrote:Incidentally, as you add more purchase between midboom and centerboard, you are degrading the effect of the split tail. The way to think about it: the force in a rope through a purchase is constant, the pull on a block with 180 degree turn is double that force (once for each part going to that block in parallel) -- similar geometrical reasoning gives you the force on a 90 degree block (total force on the block is 140% but force component in the direction of the pull is single).

Now, at the end of the boom, where one end of the split tails takes the load, you get a single part pulling at the end of the boom at 45 degrees to the side and down. Meaning your side force is 70% of the force you expend pulling on the rope. If you add more purchase (design 2) all you do is reduce the force at which you pull. You still get 70% of that force pulling sideways at the end of the boom, but now that's been reduced by the same factor.




Thanks GL! This is the type of information I was looking to get from this conversation. If there is perceivably a reduction in the effectiveness of the split tail with added purchase, this may be the rationale as to why Mike has added extra holding power (double ratchets), and skipped purchase. In theory, the purchase is to smooth out sheeting action, in or out. The ratchets are for easing the pain/effort of holding the sheet in hand (un-cleated).

I follow your explanation about the purchase being between the centerboard trunk and mid boom degrading the effect of the split tail as well. It is hard to get around that as you cannot add purchase at the end of the boom when using a split tail.

I have seen how your main sheet is rigged at the end of the boom. I presume that the small amount of extra line in the wrap you created at the end of the boom is nearly negated by the friction and/or force at the beginning of the block chain (from staring point of felt force from the sail), at least close hauled. I imagine that is why you say you felt no "big" difference on the mainsheet?
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Tue Oct 03, 2017 12:33 pm

DigitalMechanic wrote:
GreenLake wrote:I follow your explanation about the purchase being between the centerboard trunk and mid boom degrading the effect of the split tail as well. It is hard to get around that as you cannot add purchase at the end of the boom when using a split tail.


Then again, maybe I am wrong... Check out this idea... https://tbsailingupgrades.com/2017/01/28/split-tail-mainsheet/
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Re: Split Tail Mainsheet Options

Postby GreenLake » Tue Oct 03, 2017 9:05 pm

The link gives a mixture of split tail and bridle (with a 2:1). Proves you can find almost anything on the web if you look long and hard enough :)

Compared to my setup (bridle with a 2:1) it would add more purchase (3:1 at the end of the boom, equivalent to total 7:1 as compared to a pure mid-boom setup. A DS would not need that much purchase and its arguably in the way in light air maneuvers.

It would have the effect of having 6 times the effective pull at the end of the boom compared to the center and of that the bridle may have slightly better angle (*) than the CB and the split tail a definitely better angle, but its contribution is only two seventh of the total force on the boom, a smaller ratio than in your Design 1.

I wouldn't worry about friction too much. My setup has 4 blocks and I don't have any issues getting the boom forward in light winds (or back forward after a gybe). And one of my blocks is from an original CB trunk fitting; small diameter sheave, no ball bearings, Tufnol. Original stuff that I intend to keep around as long as it works and doesn't get in the way.

When I say I didn't observe a big change with the mainsheet setup (other than the immediate and very positive effect of a single ratchet mounted with a 90 degree wrap) it is because I pretty much kept a similar purchase ratio and the direction of pull on the boom didn't change dramatically. Your Design 1 may in fact result in something with a mathematically significant change in distribution of horizontal and vertical pull at the end of the boom.

Why not do a scale drawing and try to get a quantitative result (not just a qualitative)?

(*) you'd need a scale drawing and look at some angles on it.
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Re: Split Tail Mainsheet Options

Postby carl10579 » Fri Oct 06, 2017 3:01 am

I like the split tail with the adjustable cleating on both sides. In lieu of a traveler it looks to be effective. I have a simple mid boom sheet on the DS and the bigger Aquarius. The reason I like the spit tail is that you not only can get the boom closer to the centerline you can go over the centerline and point even higher. For instance the last time I was out in the DS2 I was being paced by a Catalina 22. The boat was moving faster than me but didn't seem to point as well or they were bearing off a bit. Coming up on a point on the shoreline I let out some main sheet then grabbed the bunch and pulled the boom to me past the centerline (with a lot of effort) and I was able to clear the point and continue another mile before tacking where the Cat22 couldn't clear the point and had to tack. When doing this the jib went completely limp.

I find that the question arises of whether to point higher and travel slower of bear off and go faster. But having the ability to have it both ways is appealing. I don't go sailing intending to race but I end up sailing as fast as I can anyway.
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Re: Split Tail Mainsheet Options

Postby DigitalMechanic » Fri Oct 06, 2017 5:43 am

carl10579 wrote:I don't go sailing intending to race but I end up sailing as fast as I can anyway.


I though the saying went... When 2 or more sailboats are in sight of each other on the water, there is always a race, lol.

carl10579 wrote:The reason I like the spit tail is that you not only can get the boom closer to the centerline you can go over the centerline and point even higher.


This whole conversation has really been about making the boat sail better upwind. Earlier we discussed how one modification compliments another. IE, being able to bring the foresail inboard more (via barber haulers), or sheeting the main inboard more without putting to much leach tension on it (split tail). I have just begun the modding process on my boat (barber haulers are in but not been through sea trial yet), but in my head... if you make one sail help the boat sail closer to the wind, you must make the other do so as well, to keep the boat efficient. My guess is at the end of this exercise, I will not be able to get the mainsail to outperform the foresail in this regard, but should be a little better. The split tail will not be able to keep up with the barber haulers ability to effectively trim the sail when pointed closer to the wind. Just a hunch...

The split tail should be able to center the boom (vs mid boom sheeting, with which I find it very difficult to do so). I am not sure about getting it passed there to the windward side of the centerline. I am pretty sure to accomplish that one would typically use a mainsheet on a sliding traveler across some sort of thwart (or possibly the transom)?

carl10579 wrote:I like the split tail with the adjustable cleating on both sides. In lieu of a traveler it looks to be effective.


I am intersted in your opinion on this. One of my big questions is why adjustability (and of course is this a diminishing return)? Is this where you see the opportunity to hook the boom slightly past the centerline to windward? Assuming so, this would be a technique done in light wind, where the mainsail was in "parachute" mode, allowing the boom to be "over trimmed" to get the top batten back to center, no? If I have stated my case correctly, then the cost to provide this adjustability can start to come at a premium, depending on where you want the adjustments to be available from. So, how important is easy access to the adjustability from the crew location on the boat (again is this a diminishing return)? For example, what other conditions am I not thinking of in which one would make such an adjustment to the tails? If there is not, then is it necessary to bring the adjustability points back to the crew, or leave them at the transom? I believe this adjustment to the tail would only be made in light wind conditions?

To add a little confusion to everything, I have seen it where the tails are drawn back together (lets say near the sump) and pulled across the bottom of cockpit floor to the "command center" (in our case centerboard trunk), as a (re-formed) single line that is cleated off. My hunch is that easing this line raises the apex of the triangle the lines form at the end of the boom, thus theoretically allowing the height at which the boom is centered to be adjustable. Let out some tail and take in some main, and the boom should be lifted higher and remain centered.

To try and simplify the confusion, AE stands for "Augie Equalizer" (Mentioned earlier). I do not think that they would be used on a Daysailer. So, try and imagine the picture without the AE lines rigged.

Image

If you are still following me up to this point, now I am going to tell you I lied to you... lol. The 3rd diagram I drew is essentially 2x "Augie Equalizers" rigged in the transom corners of the boat. You will notice that the split tails are not drawn back together to a single adjustable point. I can see the value of having a single "raise or lower the boom and keep it centered" control (by drawing the lines back together). Again at the cost of rigging, and extra creativity it would take to do so on a Daysailer.

The additional rigging of adding the Augie equalizers (on a snipe) theoretically solves the problem you proposed of being able to over sheet the centerline. From the snipe site... http://www.snipetoday.org/articles/articles-from-the-experts/tuning/item/1463-preparing-and-sailing-a-snipe

"The Augie Equalizer or "AE" attaches to the split tail as it runs along the deck from the outboard deck traveler blocks, one AE control line attaching on either side of the traveler center line piece. In very light air to light/medium air, by pulling the windward AE line, you can center the main and get more twist in the mainsail at the top than the split mainsheet would otherwise allow."

The AEs (on a snipe) are essentially 2 lines attached to the tails before they are drawn back together, allowing one side or the other of the apex to be independently drawn outboard (at the cost of lowering the apex as well).

Admittedly, whom ever came up with all this rigging is more creative than I. Just wondering how effective any of it would be on our boats past the simple split tail rig?
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