MainSheet Conversion

Moderator: GreenLake

MainSheet Conversion

Postby DryLake » Thu Jul 20, 2017 6:52 pm

Hey Guys,

I'm still pretty green to sailing, but I am happy to say I have my first 1973 Daysailer II. One thing I did notice is the older style mainsheet attached to the stern (triangle Pattern). I am not familiar with its operation and am concerned it may interfere with the tansom attachment of a small outboard. I would like to convert it to a CB attachment to somewhere midboom. Is there any advice on how this can be done, and where I could find the proper mainsheet.


Thanks Again,

DryLake
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Re: MainSheet Conversion

Postby GreenLake » Fri Jul 21, 2017 4:06 am

You will find fans of different sheeting arrangements here on the forum.

I never saw the need to move away from end-boom sheeting. I did make a change in how it was set up.

Originally, the mainsheet went from the CB to mid-boom, then back to the end-boom, then down to a block on the starboard side of the transom, then along the transom to a block on the port side, and back to the end-boom where it was tied off.

In this setup, the mainsheet forms a triangle above the transom.

I changed it to using a dedicated rope to provide the triangle (traveler). To the apex a block is tied. The mainsheet now goes from the CB to mid-boom, then back to the end-boom, then down to that block, back up to the end boom where it is tied off.

This setup allows me to set the size of the triangle (it does not get larger just because I let out the mainsheet).

I do need to take a bit of care when gybing. During a jibe, I will pull tight the mainsheet (somewhat) as the boom passes from side to side. That keeps the sheet and triangle traveler tight so that they do note get entangled in the stern cleats, around the corners of the stern, or the trolling motor I use.

Works fine for me and I've seen no reason to change anything.

If you are new, making a modification because you do not understand something sounds like a recipe for ending up with an expensive change that may have consequences you don't understand.

In this case, both alternatives are probably equally fine and a matter of taste. Still, it's a good idea to get some practice with the boat as rigged, if only to have a good baseline of experience against which to measure improvements.

The one change I made recently was to add a 12:1 vang (built from a 6:1 purchase combined with a 2:1 cascade). If you are not just new to the DS but generally not an experienced sailor, then you might want to read up on "vang sheeting" (including older posts on this forum). That way of using a vang is not depencdent on how you sheet your mainsheet.

As I mentioned, other people like centerboard sheeting arrangements. I remember reading various discussions, all of which should still be on the forum. (Some may be "misfiled" in the DaySailer I Only or DaySailer 2 Only part of the forum which predate the creation of this "Rigging" subforum.
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Re: MainSheet Conversion

Postby DryLake » Fri Jul 21, 2017 2:28 pm

GreenLake,

Thank you for responding. I think I will take your advice, you are right that it makes no sense to add more money when it is not needed.

Can you provide a picture for your setup with the dedicated line, I am having trouble seeing this visually.

What is your advice for keeping the mainsheet out of the way of a small tiller on the tansom, could I add a small outboard mount to keep it out of the way?

Thanks Again,

Drylake
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Re: MainSheet Conversion

Postby GreenLake » Tue Jul 25, 2017 4:10 pm

I'm using a trolling motor. It tilts flat when not in use. As long as I maintain some tension on the main sheet during gybes, the sheet does not tangle in it. For a regular outboard, a motor mount may help position things so that the traveler (triangle) is not trying to go where the motor is when it's out of the water (not used).

This picture shows the apex of the traveler when going upwind

1318

The height of the traveler, and therefore the smallest distance between the two blocks in this picture is given by the length of the line making up the traveler. My photo was taken while I was experimenting with the best setup. I've since replaced the traveler with a somewhat thinner line.

I based it off of this setup on another boat (shown with the boom in a position as if on a reach):

99.

The difference is that I didn't bother with the setup for fine tuning adjustment (in the middle of the transom). Instead, I have a simple knot there that goes around a hook under the coaming (under, so I wouldn't have to mount anything visible).

2377

Shows how the trolling motor fits under the traveler when not in use. Where the traveler has the two "tails" there's a knot that's hooked around a hook behind the coaming. This centers the traveler. As we are going downwind in this shot, it should have been released (unhooked), so the block could go out from the center position more to starboard.

Hope this helps.
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Re: MainSheet Conversion

Postby K.C. Walker » Wed Jul 26, 2017 9:00 am

I switched my set up from mid boom to the triangle end boom set up, as Green Lake described. There is more control of the leech tension and therefore the twist of the sail when using the end boom set up. However, I found that I often had the sheet getting tangled up in the motor, especially when jibing. I moved the attachment point for the block on my boom 18" forward and that solved the problem of main sheet tangle on the motor.
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Re: MainSheet Conversion

Postby GreenLake » Wed Jul 26, 2017 10:44 am

Interesting solution!

What works best will obviously depend a bit on the motor.
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Re: MainSheet Conversion

Postby K.C. Walker » Wed Jul 26, 2017 11:01 am

What works best will obviously depend a bit on the motor.

Yes, no doubt. My previous '70s Johnson seemed to have plenty of places to catch the sheets.
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Re: MainSheet Conversion

Postby GreenLake » Wed Jul 26, 2017 1:14 pm

I sail without motor most of the time, but nevertheless there are places on the boat where the sheet can catch (stern cleats, but also the corners of the transom). Not letting the sheet go slack during a gybe appears to be the best prevention. Tacks are usually not an issue.
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Re: MainSheet Conversion

Postby DryLake » Thu Jul 27, 2017 12:22 pm

Thank you for the pictures. That really clears up your explanation. I can already see that this setup reduce the amount of line that travels with the boom.

I get my part-time motor tomorrow, I will mount it and take a picture of it on the tansome.

Sorry for the late reply the forum was having a registry issue.
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Re: MainSheet Conversion

Postby GreenLake » Thu Jul 27, 2017 6:39 pm

There was a short downtime on the forum because of the way its internet address was configured. This has been straightened out with the various providers by one of the volunteers at the DSA. Remember, if you like the forum, support it by joining the DSA (at http://daysailer.org).
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Re: MainSheet Conversion

Postby fatjackdurham » Fri Jul 28, 2017 8:38 am

Can you tell me more about the traveler? I have seen a few diagrams on the Internet and want to confirm more about it.

1) I understand the purpose of the travel is to modify the angle of pull on the boom based on the wind speed during a tack, is this correct? For light winds, having the traveler to leeward pulls down more on the boom similar to a boom vang to keep the sail tight and straighter, but in heavier winds you should move the traveler to windward to allow the boom to rise a little and create more of a twist in the main sail. Is this correct, or am I misunderstanding the purpose.

2) Is the traveller supposed to be able to slight freely back and forth normally so that you don't have to adjust it during tacking, unless you have intentionally pulled it to windward? Or, are you supposed to cleat it and adjusted each time you tack?
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Re: MainSheet Conversion

Postby K.C. Walker » Fri Jul 28, 2017 9:01 am

For the most part, the current thinking amongst the top racing sailors in the class is to use a bridal or split tail main sheet rather than a traveler. Travelers have been tried extensively, both mid boom and end boom, and have not been found to be faster and are more complicated. When the racing crowd says faster they mean more control over sail power. I would guess that 100% of the top sailors also incorporate using a powerful boomvang to control twist.
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Re: MainSheet Conversion

Postby GreenLake » Fri Jul 28, 2017 6:15 pm

My reason for preferring end-boom sheeting is that it gives you 25% more purchase with the same number of blocks compared to mid-boom (and three of the blocks are at 90 degrees, so they are not loaded as heavily, and they can be larger diameter, both of which I suspect translates as slightly lower losses due to friction).

Because the end of the boom travels twice as far as the center, for each degree of deflection of the boom, with end-boom sheeting I pull out 5 units of length of mainsheet. With the usual two fiddle blocks for a 4:1 center boom arrangement, you would pull out 4 units of length of mainsheet. Because work is force times distance, to do the same work, you have to pull 25% harder to make up for the shorter distance.

And, if the losses due to friction are a bit smaller, I also do not have to pull as hard to overcome these losses.

As I don't race comparable boats, this aspect is more important to me than getting a fraction of a knot in speed.

I am familiar with split tail mainsheets from another boat I own. That system uses only 3 blocks, for ~3:1 purchase, but the boat is smaller, so less force is required to hold the main. A split tail, for those not familiar with it, is a form of end-boom sheeting where instead of going to a traveler, the main sheet is split into two strands, each of which goes to one corner of the transom. As you are pulling in on the sheet, the point where the sheet is split moves up the boom and the remaining ends form a flatter and flatter triangle as the end of the boom comes in. As the boom goes out, the part where the sheet is split will exit the end of the boom.

At what point that happens can usually be adjusted by taking in or letting out some of the end of the tails on the transom.
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Re: MainSheet Conversion

Postby K.C. Walker » Sat Jul 29, 2017 3:36 pm

+1 for what Greenlake says about the advantages. Though I used the example of racing and the best sailors in the class… And speed. I should have added more to the part about sail control which is important to all of us. Being able to effectively de-power our sails when the wind speed exceeds the "design speed" (approximately equal to 12 kn) of our boat/sails, we not only enjoy more speed but also safety and control.
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Re: MainSheet Conversion

Postby GreenLake » Sat Jul 29, 2017 6:02 pm

Adding to K.C.'s remarks. I've been sailing with a 12:1 boom vang for a while now. I had hesitated on the installation for a while now, because I have an unusual configuration where mast meets deck and I wasn't sure how to best attach a vang, but that issue appears solved. The main advantage of a higher purchase on a vang is the ease with which you can adjust it while under load.

The actual force that the vang will apply on the boom is given by the force the wind exerts on the sail. If you had a 4:1 stock vang and had pulled it tight in moderate winds and then a gust hit, you would get the same force on the boom as if you pulled tight a 12:1 or 20:1. The only difference with the latter is that you could still pull them tighter (or adjust in a controlled way) at the higher wind speeds.

I haven't had any conditions where I could really test the limits of my 12:1 setup; so far it seems to be pretty easy to adjust (and I'm not running any of the vang line through additional blocks, so I don't have losses to friction). As I wrote above, I started with a pair of triple sheave blocks for 6:1 and added a single cascade to get to 12:1. I could always add a second cascade, but so far it doesn't seem necessary.
2328
(what the picture doesn't show is the single block attached to the bail at the mast end; the orange line runs around it, forming the cascade).

My crew wasn't happy with having the line from the vang dangle where it is shown, so I'm going to reposition the blocks a bit. I may have the line exit in the middle. I don't think I want it near the mast end because the blocks I have do not allow me to angle the cleat properly. I have since seen block/cleat combination where the cleats can be fixed in a number of different positions (angles) to fit the direction in which the line exits.
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