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Post by Charlie-Bravo on Jan 16, 2023 19:04:15 GMT
Thinking of improving the main sheet arrangement, it is standard 3:1 with two attachments to the sparcraft boom to spread the load. I am thinking of developing a 6:1 system keeping the two boom attachments to keep the load spread.
It would seem that two triple blocks, one on the traveler one on the boom, one with a swivel would easily accomplish the 6:1 I am thinking might do, the question is what diameter of pulley should be in the blocks, ( sheet size 10 mm ) and what would be the recommended strain rating for the blocks ? also is 6:1 enough for easy handling, being a more or less a mid boom arrangement, which is really a winch job in any breeze.
I have had double line sheeting on previous boat which worked well , but lots of rope to stash so thinking to keep to one line. Looking for ease as the arthritic hands will like it.
All thoughts welcome.
CB
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Post by Don Reaves on Jan 16, 2023 20:42:59 GMT
I suspect that the weak link in the mainsheet system on my SO35 is the connection to the traveler. I've been concerned, now that it's about 19 years old, that it might be near its end of life. So attaching a 6-to-1 tackle to it wouldn't be my first choice. If you do beef up the system, take a look at it to make sure you don't put too much strain on it.
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Post by zaphod on Jan 16, 2023 21:55:47 GMT
Are you looking for enough purchase so you can pull it on by hand, without a winch? If so I don't think 6:1 would be enough.
If you are just looking to reduce the load on the winch then that is a different story. I would be inclined to try to maintain the 2 attachment points on the boom. You could easily increase it to 5:1 with the current setup. You could also add a 3rd tang on the boom.
I don't think it is a good idea to go with a single point and 2 triple blocks. For one thing, parallel purchases like that have a habit of getting twisted and fouled downwind, which isn't a big deal if the mainsheet is in the cockpit where it is easily cleared. On the cabintop it could be a pain in the butt, particularly if you have a dodger between you and the mainsheet. That is the nice thing about the multiple attachment points; the falls of the sheet are not parallel so will not tangle easily.
Being mid boom the loads are very high but you can probably get away with 57mm blocks. Harken has the Element line of high load blocks that are very strong but not too expensive. I have Element 60mm blocks for my spinnaker sheets. They are not ball or roller bearing blocks so they won't be as smooth as other more expensive blocks.
The Harken website has some good block sizing charts to help you choose.
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Post by Charlie-Bravo on Jan 17, 2023 11:15:46 GMT
Thanks for the comments.
When I got the boat I found the traveler car was very worn, but a newer car was in the spares box, the end caps on these cars also become fragile, and if allowed to crash into their track ends the balls escape. Not sure adding increased purchase ratio actually increases the load on the car, just changes the amount of rope to pull to get boom movement.
If 6:1 isn’t going to be easy enough to pull by hand I might abandon the idea, as the winch works at the moment, and so I might just be adding to the amount of rope swinging around , and still winching.
Thanks again for the thoughts.
CB
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Post by Don Reaves on Jan 17, 2023 14:28:50 GMT
If you want to find out whether 6:1 would give you adequate control without using the winch, you might jury rig a temporary 2:1 tackle in the tail of the main sheet. If you have some spare hardware that could be used to do this, it would answer your question without any additional cost.
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Post by Charlie-Bravo on Jan 17, 2023 15:53:26 GMT
I will have a rummage in the spares dept and have a go.
CB
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Post by MartyB on Jan 17, 2023 23:31:30 GMT
I'm assuming you have a cabin top set up here.
On my boat with a cockpit set up. I have a 4-1 with two single sheaves about 1-1.5' apart. A typical Fiddle, Becket, camcleat on traveler.
The 4-1 works well enough. I also have a micro 4-1 for fine tuning. This is really handy in heavy winds. My feeling on my boat, is a 6-1 would work better than the 4-1 if that is ALL one wants to monkey with.
BUT as you note, there will be "double?!?!!" the mainsheet line in the cockpit. You may still need access to a winch in winds above 20'ish knots, vs say 10 knots now.
My 02, something more to think about. I don't personally see an overall issue with a 6-1. A 4-1 might be a better option for issues you mention.
Marty
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Post by Charlie-Bravo on Jan 18, 2023 12:06:28 GMT
Yes it is a coachroof traveler but no cam cleat, sheet goes forward to the mast and returns to cockpit via deck sheave to a clutch, then to winch, it’s quite tidy but the deck sheave and mast base pulley no doubt adds to friction losses despite keeping them clean.
I will be jury rigging 4:1 and 6:1 just out of bits and bobs and spare string as Don suggested, then seeing if I fancy the extra string in the cockpit and how much easier it seems, before spending out on new hardware. The fiddle blocks look tidy, but the smaller pulley on even a 70mm fiddle seems 40mm or less, so I was looking at straight double and triple blocks, no doubt experiments will point me in the best direction.
Thanks for your thoughts CB
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Post by MartyB on Jan 19, 2023 4:07:09 GMT
Something to think about also. Spending the extra money for sheaves with ball bearings if you have not done so already. This helps reduce friction a bunch too. Then for one of them, get the style with a reverse braking system. THe Harken blocks I have do this. Seems to help a bit. Being as my main is only 195 sq ft, vs yours being another 25-50% larger. Also, my mainsheet being end boom vs mid boom. Things are not a hard to move.
I do find playing with things is fun, and you figure out what works for you! vs me or others.
Marty
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