Estimating mainsheet load?

[prv]

better to ensure you have good position in cockpit relative to tackle so to put your weight into

Certainly true that you can put a lot more effort into a well-positioned line - I know all about that from sailing square-riggers. Sadly the ergonomics of this boat will never be ideal for that - the bloody wheel is in the way . No worse than a lot of lines in cruising yachts.

Pete

 

[Tomahawk]

From the boats I have sailed as main sheet trimer.... it has always been a simple trade off........
Length of rope pulled against the purchase on the leach....

4:1 easy and fast but unable to get it pulled in hard
40:1 too much rope to handle in a gybe... but able to really pull the main in tight...

Look at what the racing boys do on a boat the same size as yours. Remember they will set it up for maximum efficiency so whatever they use will work.... If you copy the setup but give yourself a bit more purchase (say 6:1 instead of 5:1) you will get a good ballance..

Enjoy

 

[prv]

Look at what the racing boys do on a boat the same size as yours.

Trouble is I don't know what the racers do on a boat like mine. And I want to get the new blocks ordered so I can secure the boom properly, so I can't really go out and watch

EDIT: Originally posted here saying I was going to get a two-speed 6:1. But now I've changed my mind again . I have two substantial D rings at each end of the mainsheet track, part of the original winched system. That would work quite nicely with a double-ended tackle on the traveller, with ends coming from the boom down to the rings, one incorporating a tweaker and one running via a fairlead and jammer on the deck. A tweaker would work there where it wouldn't as part of one big tackle.

Pete

 

[prv]

If I do go with the above plan, I'll end up with something like an inverted W, with the outer legs fixed at about the width of the cockpit, and the middle leg on the traveller. I want to retain the use of the track to properly shape the sail - will that work with the legs to either side?

Pete

 

[knuterikt]

Why make it so diffcult?

The orginal setup is 1:2 + winch with power ratio 1:8 and/or 1:16

So the power gain in this configuration is 1:16 and/or 1:32
Should give an indication on what the builders assumed.

Sailarea 28m2 if you can measure (or estimate) the boom lenght you can calculate the luff length, this is not an exact science anyhow)
The sail is close to triangular.
(E) Foot length of main in meters
(P) Luff length of the main in meters
(SA) 28m2

Use this formula P=28*2/E

Use this http://www.harken.com/content.aspx?id=9094
Try with different wind speeds 10/15/20 knots (try to guess when you will put in a reef)

Resources
Harken
http://www.harken.com/content.aspx?id=3902
http://www.harken.com/content.aspx?id=3901

Lewmar catalog page 162 onwards
http://www.lewmar.com/cms/assets/1/Catalogues/Lewmar-English-lr.pdf

 

[Rossynant]

Sadly the ergonomics of this boat will never be ideal for that - the bloody wheel is in the way .
Pete

This is egronomics I spoke about - loaded this pic for another thread, might find better - mainsheet in front of the wheel. Not enough space to sit before the wheel too. https://picasaweb.google.com/lh/photo/dytOY8ABU4Zcg6NCS1XY4NMTjNZETYmyPJy0liipFm0?feat=directlink

Sheet for both sides (as it was called here) which you think of worked instead of track - giving the possibility to shape sail properly, tensioned down to lee board. Might be not so well as with track - but why complicate it with track? Unless the track is not in the way, anyway.

Knuckerit - many things sound nicely on paper. Studying all such myself now, to get ideas. But as hauling on the sheet goes - on above boat I preferred to take genoa sheet by hand (put on winch but no handle in and "winching") cause was faster to shed wind from a sail, luffing, and just give it a haul. Ended never using the winch handle; even in stormy winds; the technique employed had another asset - astonishing the girls

So to show the sheet tackle - and prove anybody could operate it
https://picasaweb.google.com/lh/photo/a3_gBdd6pREscZQmb8sQmdMTjNZETYmyPJy0liipFm0?feat=directlink

 

[grumpy_o_g]

The orginal setup is 1:2 + winch with power ratio 1:8 and/or 1:16

So the power gain in this configuration is 1:16 and/or 1:32
Should give an indication on what the builders assumed.

Sailarea 28m2 if you can measure (or estimate) the boom lenght you can calculate the luff length, this is not an exact science anyhow)
The sail is close to triangular.
(E) Foot length of main in meters
(P) Luff length of the main in meters
(SA) 28m2

Use this formula P=28*2/E

Use this http://www.harken.com/content.aspx?id=9094
Try with different wind speeds 10/15/20 knots (try to guess when you will put in a reef)

Resources
Harken
http://www.harken.com/content.aspx?id=3902
http://www.harken.com/content.aspx?id=3901

Lewmar catalog page 162 onwards
http://www.lewmar.com/cms/assets/1/Catalogues/Lewmar-English-lr.pdf

I was struggling as to why this was so complicated. As long as you know the winches power ratio then the only difference would be the resistance due to friction in the blocks instead of the winch. I'd have though a ball race block would have pretty low resistance. Assuming an 8 to ratio plus the block you have 16:1 so a 16:1 pulley arrangement would require the same pull on the rope as was required on the winch. The sail area hasn't changed so you simply need to replace the gearing mechanism on the winch with one using blocks.

 

[knuterikt]

This is egronomics I spoke about - loaded this pic for another thread, might find better - mainsheet in front of the wheel. Not enough space to sit before the wheel too. https://picasaweb.google.com/lh/photo/dytOY8ABU4Zcg6NCS1XY4NMTjNZETYmyPJy0liipFm0?feat=directlink

Sheet for both sides (as it was called here) which you think of worked instead of track - giving the possibility to shape sail properly, tensioned down to lee board. Might be not so well as with track - but why complicate it with track? Unless the track is not in the way, anyway.

Knukerit - many things sound nicely on paper. Studying all such myself now, to get ideas. But as hauling on the sheet goes - on above boat I preferred to take genoa sheet by hand (put on winch but no handle in and "winching") cause was faster to shed wind from a sail, luffing, and just give it a haul. Ended never using the winch handle; even in stormy winds; the technique employed had another asset - astonishing the girls

So to show the sheet tackle - and prove anybody could operate it
https://picasaweb.google.com/lh/photo/a3_gBdd6pREscZQmb8sQmdMTjNZETYmyPJy0liipFm0?feat=directlink

Nice boat you have - probably a little bit different from the OP's..

I posted those links to give some more ideas, the OP did not post any pictures of his boat to help us see..

I know that theory and practice is not necessarily the same

I'm happy with main sheet going on the winch on my boat - but did not ask the OP why he moved his (before having found a new alternative working solution).

I can easily adjust both main and head sail from behind the wheel, works fine when sailing alone.

 

[prv]

The orginal setup is 1:2 + winch with power ratio 1:8 and/or 1:16

So the power gain in this configuration is 1:16 and/or 1:32
Should give an indication on what the builders assumed.

Well, ish. The 16 is the smallest self-tailer in the Lewmar range, which I suspect is a rather more significant fact.

Sailarea 28m2 if you can measure (or estimate) the boom lenght you can calculate the luff length

...or I could measure the height from the deck to the gooseneck and subtract from the height of the mast.

Pete

 

[prv]

Sheet for both sides (as it was called here) which you think of worked instead of track - giving the possibility to shape sail properly, tensioned down to lee board. Might be not so well as with track - but why complicate it with track? Unless the track is not in the way, anyway.

I don't quite understand what you're saying here. The track runs across the boat aft of the cockpit. It's already there, and it's not in the way. I would expect to use the track to haul the traveller to windward of the centreline, so that I can bring the boom further inboard when a fixed mainsheet would be hauling mostly downwards instead of inwards. But with the inverted W setup I would always have one line pulling to leeward, and I wanted to know whether this will negate the effect of moving the traveller.

Pete

 

[prv]

I was struggling as to why this was so complicated. As long as you know the winches power ratio then the only difference would be the resistance due to friction in the blocks instead of the winch. I'd have though a ball race block would have pretty low resistance. Assuming an 8 to ratio plus the block you have 16:1 so a 16:1 pulley arrangement would require the same pull on the rope as was required on the winch. The sail area hasn't changed so you simply need to replace the gearing mechanism on the winch with one using blocks.

That's certainly true in theory, but I'm not convinced it would hold in practice. Firstly, the winch is the smallest in the range - so was all its power necessary in the first place, or was it the self-tailing feature that determined the choice? Secondly, the ergonomics of hauling on a line and winding a winch handle are rather different; if you had to take a firm grip and really pull on the end of a winch handle, I think most of us would say the winch was overloaded. But it's normal, and easier, when hauling on the end of a tackle. So I'd rather start from a comparison of all-rope mainsheets that work on other boats, than simply computing mechanical advantage.

Pete

 

[Rossynant]

Nice boat you have - probably a little bit different from the OP's..

Not mine - belongs to university club Just coming back to sailing, while injured, I also put some thoughts into ease of handling must say, while shopping for a boat. Agreed, counting loads is first thing to do, getting general idea. In OP's situation sheet loads may not be got smaller, sheet at boom end, so purchase better be adequate. For sheet winch - I find it inconvenient to work the winch by handle, just my preference - takes time and cannot be done from any other place so I would do without if could be avoided. Good arrangement for convenient handling of all that is around can also be organized in many ways, but for this I understand OP has to try boat first.

My boat now is small ketch, main below 20 sqm (about 18 but can't remember at the moment), typical 4 part purchase to it coming to mizzenmast and hauled down. Seems handy but will try her properly this year - anyway I like this "down" bit. To think now that such small sails I've handled without any purchase when young...
Including boomless main on gaff ketches used for sail teaching, which was overlapping and sheeted to both sides like genoa, constant work in tacking. Even this boat was perfectly possible to singlehand, despite having 5 or even 7 sheets to operate at tack (mizzen had to be adjusted to tack against decent wind...) - but no winches there were to add complexity, luckily

PS to above- this is perhaps obvious, but: there is quite a loss of efficiency in a tackle, mostly depending on sheave sizing. Can't now remember, there was a guidance to standard sheave diameter for line size, with block a bit undersized it was noticeably harder to pull. Best I recall was blocks standard for 14 mm rope, fitted with 12 mm line. Line can get swollen or hairy so probably this was a reason for some more friction sometimes. Jaws or clamps on the tackle block itself may be inconvenient sometime, this depends on placement and personal preference. Anyway some cleat close-by and handy to hold the line against makes it easy to jerk a line hard, or to pull down on fall of the tackle while holding end jammed.

 

[knuterikt]

Well, ish. The 16 is the smallest self-tailer in the Lewmar range, which I suspect is a rather more significant fact.



...or I could measure the height from the deck to the gooseneck and subtract from the height of the mast.

Pete

If you can't get to the boat for measurements, you have some options.
-If you have the mast height you can estimate the luff length and calculate the boom length.
-If your boat is not a one off, maybe someone on this forum know the measurements
-The sailmaker who maid the sail might have the measurements

The inverted W you describe will balance it self in a way.. If you have more advantage in the middle the traveller position will influence most..
But wouldn't a setup like this block the passage for and aft?

 

[Rossynant]

I would expect to use the track to haul the traveller to windward of the centreline, so that I can bring the boom further inboard when a fixed mainsheet would be hauling mostly downwards instead of inwards. But with the inverted W setup I would always have one line pulling to leeward, and I wanted to know whether this will negate the effect of moving the traveller. Pete

To this - I may not be so clear in English, sorry. Understood You want to divide the tackle, so to have two ends going to the sides - this allows hauling on the sheet from both sides, whichever handy. Something like this: https://picasaweb.google.com/lh/photo/9OvXJKTvPLrPMdARlVWcV9MTjNZETYmyPJy0liipFm0?feat=directlink
Effectively boom will be hauled down by a triangle of lines. Such arrangements were in use and it worked (at least on one I've seen) in such a way that boom was hauled down not toward central attachment point but a bit more to leeward side - something similar to moving the traveller to leeward. This triangle of lines was distorted to the side boom was on. This was main reason for it, as main has less twist when hauled down to leeward side instead to the center.
So yes, if you want traveller to windward side (to pull boom 'the wrong way') this arrangement might partially negate the effect. But it's easy to try and see, once you'll have blocks and line it can be tied in any way to experiment.

 

[prv]

If you can't get to the boat for measurements, you have some options.

Going down to the boat tonight, so I might as well measure. But it's not that big a deal - the reason we want these measurements is to put them in a load calculator that even its authors say is not particularly accurate; Salty John already gave us a rule of thumb figure back in post number 4.

The inverted W you describe will balance it self in a way.. If you have more advantage in the middle the traveller position will influence most..

That's what I'm hoping, but interested if anyone has any experience.

But wouldn't a setup like this block the passage for and aft?

Well, perhaps, if I developed a sudden urge to throw myself off the transom in a hurry...

Pete

 

[prv]

To this - I may not be so clear in English, sorry. Understood You want to divide the tackle, so to have two ends going to the sides - this allows hauling on the sheet from both sides, whichever handy. Something like this: https://picasaweb.google.com/lh/photo/9OvXJKTvPLrPMdARlVWcV9MTjNZETYmyPJy0liipFm0?feat=directlink

Similar to that, except that the lower central block is on a track and can be moved to either side. And the stern's wider, so that movement would have more effect

This was main reason for it, as main has less twist when hauled down to leeward side instead to the center.

I think this might be a gaff vs bermudan thing. On a gaff rig, yes you want plenty of downward tension, to help stop the gaff sagging off to leeward. So moving the traveller underneath the boom will let you do this, without oversheeting the main. In a bermudan boat, though, I am given to understand that in lighter winds you want to move the boom inboard *without* pulling down too hard on the end. I have a lot to learn about bermudan sail-shape (I never bothered too much on chartered boats, and the skipper was generally the expert on other people's yachts), but I can see that pulling hard on a centrally-mounted mainsheet will do more to tension the leech, making it flat and "closed", than it will to pull the boom inboard. So instead you put a little less tension in the sheet, and move the base of it up to windward to adjust the angle of the boom.

it's easy to try and see, once you'll have blocks and line it can be tied in any way to experiment.

Trouble is, the blocks I need to buy will be different for a single tackle vs an inverted W.

Pete

 

[knuterikt]

Well, perhaps, if I developed a sudden urge to throw myself off the transom in a hurry...

Pete

Sorry this little detail slipped - I didn't remember that your track was aft of the cockpit.

 

[Ex-SolentBoy]

My track is aft of the cockpit. 50 square metre main. 2:1 no problem.

 

[prv]

My track is aft of the cockpit. 50 square metre main. 2:1 no problem.[/IMG]

Sure, but you use a winch with it.

Lovely boat though

Pete

 

[Ex-SolentBoy]

Sure, but you use a winch with it.

Only to bring it in.