New Mainsheet System Required

[Porthandbuoy]

Here's a schematic of the mainsheet system on Sheolin.

The mainsheet is 16mm braid on braid. The port & starboard single blocks are Tufnol, as is the double block with becket. The central block, which is attached to the traveller, is by Selden. None of the blocks have swivels and all are too narrow for 16mm rope. Friction is horrendous and the time to take in a reef seems to be when the wind manages to blow the boom out! Thanks to the lack of swivels and the tight fit of the mainsheet, the Tufnol block cheeks are badly worn. Time to change everything.

The question is, to what? Would the arrangement in the schematic be efficient with correctly sized line and blocks, or is there a better arrangement?

Mainsail area is ~24 m^2 (258 ft^2) and the mainsheet is attached to the end of the boom.

 

[sarabande]

I would be tempted to ignore the block on the traveller, and go for separate multi-partblock/tackle to port and starboard, both fixed to the base of the boom.

Use either the P or S as needed when on the wind, and both if you want to flatten the main or gybe control.



If you are a long steady tack, you can unclutter the cockpit by using the snap shackle. Multipart purchases mean you could bring the sheet down to 12mm.

 

[Porthandbuoy]

@sarabande . I quite like the look of that. What's the mechanical advantage? 4:1?
Wouldn't fiddle blocks be a bit less inclined to induce twist though?
I wouldn't go for cam cleats as the blocks are way back over the aft cabin as there are hefty cleats either side of the hatch for cleating off.
Going down to 12mm has a lot of appeal on cost grounds.

 

[Chiara’s slave]

16mm? My mainsheet is only 10mm on a 35m fully battened main. Purchase wise, we have a 2 speed arrangement, high gear is 6:1 which I can just about sheet home on a beat in 10kn. I agree with @sarabande, but might go further. 12mm will be plenty, and 4:1 likewise, given that arrangeme nt.

 

[sarabande]

MA depends on the config of the blocks you choose. In the sketch it is 4:1 rove to advantage.

To me, twist happens when using 3 strand line; braid on braid usually is 'clean'.

12mm seems to fit in my paws more easily than 10mm, though strong enough with a decent make.

 

[roaringgirl]

We have a 30m^2 main with the sheet attched at the end of the boom. We use 2 lewmar triple blocks with swivels, one on the boom-end, one on the traveller. The one on the traveller has a cam cleat. The line is 12mm.

The mainsheet can be controlled like a dinghy!

 

[KompetentKrew]

Size of boat? Tiller or wheel steered?

My boat has a german mainsheet system - certainly since I bought it, and probably since it was built - and I wouldn't have anything else. But it may not suit you or your boat.

 

[Kukri]

Kukri has 47.5 sq metres / 510 sq ft in the mainsail and a 14mm mainsheet. 12mm would work perfectly well, but I find it harder on my hands. 4:1 purchase (Lewmar Ocean fiddle blocks and traveller block) to Harken 42 winch.

I have noticed that a good many vastly experienced long distance short handed people use Sarabande’s system in the picture, in his post (the second post in this thread) usually with fiddle blocks.

Having said that, I have a handy billy with a jam cleat and two snap shackles always available in the cockpit - it is there to lock the boom when doing anything with the mainsail and at anchor. Traveller locked off to port, handy billy clipped on to starboard in this snap.

 

[Chiara’s slave]

That is my experience too. For such a task, the KISS principle rules.

 

[Porthandbuoy]

Size of boat? Tiller or wheel steered?

33’ centre cockpit ketch. Wheel steering.
Definitely not hi-tech.

Going back to ~24 m2 mainsail. What sort of mainsheet loads are we talking about? There is a significant difference in the swl of plain bearing blocks vs ball, or roller bearing blocks, of the same size.

 

[Kukri]

33’ centre cockpit ketch. Wheel steering.
Definitely not hi-tech.

Going back to ~24 m2 mainsail. What sort of mainsheet loads are we talking about? There is a significant difference in the swl of plain bearing blocks vs ball, or roller bearing blocks, of the same size.

To be honest I doubt if the loads on a mainsheet are high, with one important exception which is the shock loading that may occur in some circumstances at the end of an accidental gybe.

Conversely an easy running mainsheet is very nice to have. I’d go for roller bearings.

 

[Chiara’s slave]

You can have high load roller/ball bearing blocks, they just cost more. Ronstan might have what you need, find the part numbers and google for the best price. If that’s still too dear, then plain bearings it is. The lower friction does make a surprising difference to the force required to sheet in under load, you’ll thank yourself for going the extra if you can.

 

[flaming]

Nothing really wrong with the layout of the current system. Just the mainsheet is far too thick, and the blocks have too much friction.

Easy enough to fix if you're prepared to throw some money at it. More challenging to make a significant upgrade on a budget, but reducing the size of the rope would give you the biggest gains.

 

[Refueler]

We have a 30m^2 main with the sheet attched at the end of the boom. We use 2 lewmar triple blocks with swivels, one on the boom-end, one on the traveller. The one on the traveller has a cam cleat. The line is 12mm.

The mainsheet can be controlled like a dinghy!

TBH ... that would be my solution as well - in fact I might even reduce that to a 3 sheave block + 2 sheave block ..... but without the cam-cleat as OP being a centre cockpit boat - he needs to be able to cleat / uncleat easily.

The original setup - 16mm sheet is definitely overkill ... 12mm better. The side blocks IMHO really add nothing but complication.
IF the side blocks could actually control 'traveller block' position - then OK ... but unlikely.

 

[Porthandbuoy]

I went off the idea of two sheets; just too much rope in the cockpit.
I've ordered 30m or 12mm rope for the mainsheet and will simply replace the 16mm until I see how easy things run and how fair the leads are. I've also replaced two old, worn,Tufnol singles with Barton PBB60 blocks I had in my bosun's bag.
Whatever I do has to be better than dragging a 16mm sheet over five 14mm sheaves!

 

[roaringgirl]

TBH ... that would be my solution as well - in fact I might even reduce that to a 3 sheave block + 2 sheave block ..... but without the cam-cleat as OP being a centre cockpit boat - he needs to be able to cleat / uncleat easily.

The original setup - 16mm sheet is definitely overkill ... 12mm better. The side blocks IMHO really add nothing but complication.
IF the side blocks could actually control 'traveller block' position - then OK ... but unlikely.

Not sure what being a centrepp cockpit boat has to do with the cam-cleat, we are CC also.

Our traveller has a 4:1 system and is adjustable by hand under load.

 

[Refueler]

Not sure what being a centrepp cockpit boat has to do with the cam-cleat, we are CC also.

Our traveller has a 4:1 system and is adjustable by hand under load.

If sheet system is well astern of cockpit - then having a cam-cleat on the sheet block could prove awkward. If you look at the original schematic - it notes that sheet is cleated off remote from the blocks.

 

[Porthandbuoy]

Not sure what being a centrepp cockpit boat has to do with the cam-cleat, we are CC also.

Our traveller has a 4:1 system and is adjustable by hand under load.

Mainsheet traveller and blocks are behind the sliding hatch to the aft cabin. Fitting a block with a cam-cleat may create a problem I don’t have.

 

[Refueler]

Mainsheet traveller and blocks are behind the sliding hatch to the aft cabin. Fitting a block with a cam-cleat may create a problem I don’t have.

As I suspected .... cheers