Mainsail sheeting arrangements

[Hartley18]

Originally Posted by Jeff_H

Traditionally, before the popularity of roller reefing booms of the 1960's, the mainsheet attrached to the boom 10% to 25% forward of the end of the boom. It was typically attached with multiple bails with the forward most bail, or the heaviest loaded bail, directly over the traveller, or horse. End boom sheeting is the most efficient way of sheeting a sail in terms of requiring the least am out of line, force and boom size. It is generally a bad idea to have the mainsheet at the midpoint of the boom since this has the highest loadings on the boom and requires the most rope or else on a bigger boat a winch. That said it is often done on boats with cabin top mounted travellers and on small racing dinghies.

The reason that I say that mid-boom sheeting requires the most line has to do with the way that designers approach designing sail handling hardware. We start out by determining how much load that we think the sail handler can reasonably pull (say 30 lbs) and then we back into the amount of purchase required. So if we look at a boat with end boom sheeting that needed a 3:1 mainsheet, if we moved the mainsheet to a position 25% from the end of the mainsheet we would need to go to a 4:1 mainsheet. And if we went to the mid-point we would need a 6:1 mainsheet. Except that there are much higher frictional losses when we increase the mechanical advantage and typically the mechanical advantage is further increases so in the example above the 25% position might be increased to a 5:1 and the mid-boom position to a 8:1 (or put on a winch with a stopper). In other words not only are you dealing with a lot more line but also a lot greater frictional losses.

Jeff

Jeff, apologies for the delayed response - work has kept me away from Sailnet for almost a week now.

Frictional losses were not something I'd considered. Thanks for the info - very helpful!!

Plan B: To get the ideal layout, it seems my only other option would be to move the traveller to the bridge-deck (50% of boom) with the tail running along the underside of the boom, through a block at the current sheeting position (about 75% of boom) and down to a rachet-block on the cockpit floor beneath the current traveller position.

I don't know for sure, but this probably wouldn't work as well as what I've got now.. Thoughts??

[sailaway21]

Increased effort due to friction can be calculated at roughly 10% per sheave. This might be high for high performance yachting blocks but can serve as a good rule of thumb.

[sailingdog]

Besides, always better to overestimate losses due to friction than underestimate them.

[sailingfool]

Originally Posted by Hartley18

...To get the ideal layout, it seems my only other option would be to move the traveller to the bridge-deck (50% of boom) with the tail running along the underside of the boom, through a block at the current sheeting position (about 75% of boom) and down to a rachet-block on the cockpit floor beneath the current traveller position.

I don't know for sure, but this probably wouldn't work as well as what I've got now.. Thoughts??

Cameron,

It still unclear why you want to change the existing mid0-cockpit location...while it may not be "ideal", why isn't it just fine?

What you propose sounds like a lot of work for little benefit. I personally would much prefer the existing arrangement to Plan B. Before proceeding with Plan B, try to devise a solution to ensure that the mainsheet won't decapitate a guest when you gybe the main...that tail will have a lot of slack in itwhen it crosses the cockpit, as may the line along the boom.

I'd buy that new rachet block with an adjustable cam cleat and declare victory.

[Hartley18]

Originally Posted by sailingfool

Cameron,

It still unclear why you want to change the existing mid0-cockpit location...while it may not be "ideal", why isn't it just fine?

What you propose sounds like a lot of work for little benefit. I personally would much prefer the existing arrangement to Plan B. Before proceeding with Plan B, try to devise a solution to ensure that the mainsheet won't decapitate a guest when you gybe the main...that tail will have a lot of slack in itwhen it crosses the cockpit, as may the line along the boom.

I'd buy that new rachet block with an adjustable cam cleat and declare victory.

SF, agreed it is a lot of work.. The main reason for wanting to change the layout was to get rid of this *#%&! bar running across the middle of the cockpit that (a) makes moving around in an already cramped cockpit rather difficult unless you're a skilled acrobat and (b) has the First Mate complaining about lost seating room!!

It's funny you say "ensure that the mainsheet won't decapitate a guest when you gybe the main" - that's kind of what happens now.. except it happens to me instead.

I'm going with your last sentence. Thanks for your input. Much appreciated!

[sailingfool]

Originally Posted by Hartley18

...

It's funny you say "ensure that the mainsheet won't decapitate a guest when you gybe the main" - that's kind of what happens now.. except it happens to me instead. ...

FWIW on the Rhodes19 with a mid-cockpit traveler, I control the mainsheet starting a gybem, by grabbing the middle of all turns in one hand, then gybing the main by yanking the sheet across the cockpit. The pull takes all slack out of the sheet as it crosses the boat. This manouver wouldn't work for the tail if that came back into the aft part of the cockpit...

[Hartley18]

Originally Posted by sailingfool

FWIW on the Rhodes19 with a mid-cockpit traveler, I control the mainsheet starting a gybe, by grabbing the middle of all turns in one hand, then gybing the main by yanking the sheet across the cockpit. The pull takes all slack out of the sheet as it crosses the boat.

Yes, that's what I do currently (accidental gybes can get a bit hairy though!)

Originally Posted by sailingfool

This manouver wouldn't work for the tail if that came back into the aft part of the cockpit...

You are quite right. Shifting the traveller forward with a tail aft does mean controlling the mainsheet would be more difficult during a gybe. I never thought of that.

[Sasha_V]

Dear Mr Hartley...

You have a very small sailboat, Mid-boom sheeting from the bridge deck will be absolutely FINE for you. Your boat will never battle with Cape Horn or compete in a tacking duel with Wild Oats XI. You are making problems that are not really there, and then worrying about them. Ask me nicely and I shall fabricate a load spreading boom saddle that spreads the pull force of the mainsheet across a decent area of boom. You do nto "really" need this, but it will aid the peace of mind and it is a practical solution. You can then enjoy sailing with unbarked shins and speedy sail trim responses.

Take a look at the one for Jester;

http://members.armourarchive.org/sasha/PB250050.JPG


Sasha

[Hartley18]

Originally Posted by Sasha_V

Dear Mr Hartley...

You have a very small sailboat, Mid-boom sheeting from the bridge deck will be absolutely FINE for you. Your boat will never battle with Cape Horn or compete in a tacking duel with Wild Oats XI. You are making problems that are not really there, and then worrying about them. Ask me nicely and I shall fabricate a load spreading boom saddle that spreads the pull force of the mainsheet across a decent area of boom. You do nto "really" need this, but it will aid the peace of mind and it is a practical solution. You can then enjoy sailing with unbarked shins and speedy sail trim responses.

Take a look at the one for Jester;

http://members.armourarchive.org/sasha/PB250050.JPG

Sasha

Sasha, you have a point (and that's a fine piece of metalwork you've got there - you've got the tools to do that sort of thing?? ) but the issue is that our mainsail is now loose-footed.

Moving to a 50%-of-boom sheeting position would put incredible amounts of bending force on a boom already riddled with rivet holes and fastenings. Given the kind of weather we seen to find ourselves in, after saving up for a new fiddle-block, will not have enough $$$ left for a new boom - when it snaps..

I'll have another look at this if/when we get enough cash for a new boom... or we break this one.