Mainsheet blocks.

Allan

Allan

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I now have a sloop rig Westerly 33 and I want to change the mainsheet blocks. The mainsail is approx 240 sq ft. I am trying to decide which blocks to fit, at present it has a double with becket on the boom and a triple with camcleat on the track. I'm thinking of using a triple on the boom and a triple with becket and camcleat on the bottom. Hopefully this will make pulling in the main whilst leaning over the wheel a little easier. Any comments?
Allan
 
It will reduce the effort to 5/6ths of what it is at present (ignoring any increase in friction), but it will increase the length of rope you have to haul in (or let out) every time to 1.2 times the present.
 
We used to have a W33 Ketch and fitted an Easymatic mainsheet system which was excellent. This is a complete system with a double cam cleat lower block, the mainsheet is usually spliced to make a continuous line. The idea is that you pull on both lines through the cleats to get most of the sheet in then on just one (low gear in effect) to tension it. Similarly you let off both lines to let the boom out quickly or just the one to make a fine adjustment. The blocks used are very free running roller ones. We bought ours from Alladins Cave and they also supplied and spliced the mainsheet to match it.
 
Another option is to have a fine tune tackle, usually 3 or 4:1. This makes pulling the main in tight much easier, without loads more rope in the cockpit. Its usually only the last few pulls where the load really comes on the mainsheet, as the leach tension is taken off the kicker.
I think there are some diagrams on the Harken site.
Don't forget that angle of pull and friction are as significant as velocity ratio!
Also, is the kicker doing enough to relieve the mainsheet of leach tension? I know its not like a dinghy where the boom is expected to be strong enough to put all the vertical component through the kicker, but many yachts would benefit from a more powerful, easy to adjust kicker imho.
 
I made a substantial difference by replacing a 15 year old double block with a Lewmar racing block with torlon bearings - that near enough halved the apparent weight when pulling.

When I'm feeling rich again, I'll change the other part of the purchase!
 
To reduce the knitting on the floor, fit a wire strop from the boom to almost chock-a-block, centre horse. You will save that length multiplied by the number of block leads.
 
That has given me an idea, I plan to raise the lower block up to reduce the need to bend over my, large, wheel. I was planning to use a long shackle but could go higher with a strop down there.
Many thanks.
Allan
 
The only problem about putting the lower block on a strop is that it falls down when the sheet goes slack in a tack and lands on whatever is underneath. I solved this on our boat (Storm 33) with a length of bungy cord from the backstay to the block. This just supports the weight of the block but doesn't impede the action of the block, sheet or traveller.
 
Again, thanks for that. My boat has a track ahead of the wheel, in the centre of the cockpit, I should be able to put something onto the crashbars between the binnical and the main block.
Allan
 
Another problem with putting the lower block on a strop is that when the sheet is under high tension, the whole block will rotate when you try to snap it downward to release it from the jammers.
I did it on my mizzen and it doesn't work at all well, I would go so far as to say that it might be dangerous on a main.
 
I agree that if you want to raise the bottom block you need to do it on a solid mounting ie bracket extension rather than a strop. Strops are great on the pulley hanging from the boom.

Most simple yachts have a 4 purchase on the mainsheet. One racing yacht I sail on (fractional 40ft) has 6 purchase with another adjustable 4 purchase on the tail to the becket. But with 6 purchase you really need good low friction blocks especially when you want to release mainsail pressure in a hurry. In other words don't expect too much improvement with your additional purchase as much will be lost in friction. olewill
 
Fine tuners and blocks hanging on strops from the boom have caused some serious head injuries in the past. Probably more appropriate on a racing yacht where the crew dont mind the odd bang on the head. /forums/images/graemlins/grin.gif
 
Having a strop from boom to top block will reduce the overall length of the rope but you will still have to pull in just as much and there will be just as much on the floor. (The amount you have to pull in depends upon the purchase - nothing else.)
 
Various people have mentioned friction. One thing worth trying is to reduce the rope thickness. I have a 3/6 part double system and, with the original 12mm line, it needed manually overhauling. Now with 8mm it runs out freely, even on the 6:1 setting. The system has truly been transformed and is far easier to use.
 
Probably not very relevant, but...

I had the fairly standard 4:1 set-up found on Ospreys. I felt it was fine until a fortnight ago when I sailed with the full mainsail in a force 4, nudging 5...

...I don't know how butch other Osprey helms are, but I'm not that tough. Damn 10mm sheet nearly pulled my hand off, even with the vang tugged down tightly.

I suppose the favourite solution is a quality ratchet block, but for less money I fitted a pair of double, size-3 Bartons on boom and deck, so the overall advantage is 6:1, much easier...

20150828_182619_zpssaubfgwz.jpg


...of course, in very light winds, the advantage is much more like a nuisance...but my boom-blocks are connected to the boom by snap-shackles, so in moments I can reduce it to 2:1.
 
lw395 said:
Another option is to have a fine tune tackle, usually 3 or 4:1. This makes pulling the main in tight much easier, without loads more rope in the cockpit. Its usually only the last few pulls where the load really comes on the mainsheet, as the leach tension is taken off the kicker.
I think there are some diagrams on the Harken site.
Don't forget that angle of pull and friction are as significant as velocity ratio!
Also, is the kicker doing enough to relieve the mainsheet of leach tension? I know its not like a dinghy where the boom is expected to be strong enough to put all the vertical component through the kicker, but many yachts would benefit from a more powerful, easy to adjust kicker imho.
Click to expand...


+1, this is probably the way to go; you are using ball bearing blocks aren't you ? If not, problem solved at a stroke ! ( which is probably what your wallet may endure, but grit your teeth, it's only once...).
 
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