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Old 11-10-2017, 03:53   #1
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2:1 purchase for genoa sheet

I am contemplating to change my genoa sheet setup as I have the feeling that the forces on the traveler car and winch are too high, it's a pain in the bottom to winch the sheet when close hauled and the wind starts blowing a bit, even when still far from having to reef. The boat a custom 44 foot cat, the genoa has 40m2.

Now the sheet is attached with a bowline at the clew and led straight to the traveler car from where it goes to a standing block and then to the winch. I was thinking of adding a strong eye at the bottom of the track, attach the sheet to that eye and lead it through a block at the clew back to the car, creating a 2:1 purchase.

I've never seen that setup on a big cat (had it on my 17 foot Wharram though). Is that an normal setup on this type of boat? What disadvantages am I to expect besides the banging of the blocks when the genoa start flapping? Does anyone have that setup on a similar boat?

Or should I just invest into a new, good quality sheet instead? The current sheet is IMO oversized at 16mm as the blocks are for 14mm max and the winch has a 75mm drum. Also, the sheet is a cheap Chinese no name brand, probably rather questionable quality.

Thanks everyone, this is my first post after lurking for a few years, please be gentle
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Old 11-10-2017, 04:06   #2
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Re: 2:1 purchase for genoa sheet

I have never seen such a setup, it sounds like a bad idea to me. AFAIK big boats come with bigger genoa winches & sheets. My 42 sqm genoa comes with 14mm polyester sheets, all good.
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Old 11-10-2017, 04:20   #3
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Re: 2:1 purchase for genoa sheet

Your Jeffcat is very similar in size to my Belize and I have a 44m genoa. I've never felt the need to do that.

I'd say your winch at 75mm drum diameter is undersized.
As an example Harken recommend their 53 for a 40m genoa. The 53 has a drum diameter of 112mm.

The 53 is also is rated for a maximum sheet of 14mm. So I'd agree that your sheet at 16mm is probably oversized for the rest of your system.
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Old 11-10-2017, 22:26   #4
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Re: 2:1 purchase for genoa sheet

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I have never seen such a setup, it sounds like a bad idea to me. AFAIK big boats come with bigger genoa winches & sheets. My 42 sqm genoa comes with 14mm polyester sheets, all good.
Thanks for the input! Would you mind to elaborate why you think it's a bad idea? I can see that the blocks at the clew would introduce additional complexity and might be dangerous to the crew if the genoa is flapping (on the other hand the clew is a big stainless steel ring and already pretty heavy, not sure if two blocks would make much of a difference). Tacking might get a bit more difficult because of the added block and line length. My problem is I've "inherited" this setup and a 100mm+ winch is out of my budget currently. I can live with the current setup if I need to, the 2:1 purchase would just be an affordable improvement if it works as intended.
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Old 11-10-2017, 22:43   #5
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Re: 2:1 purchase for genoa sheet

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Originally Posted by StuM View Post
Your Jeffcat is very similar in size to my Belize and I have a 44m genoa. I've never felt the need to do that.

I'd say your winch at 75mm drum diameter is undersized.
As an example Harken recommend their 53 for a 40m genoa. The 53 has a drum diameter of 112mm.

The 53 is also is rated for a maximum sheet of 14mm. So I'd agree that your sheet at 16mm is probably oversized for the rest of your system.
Yes, I agree that my winch is most likely too small, it's a setup that I inherited. As stated in a previous post, a bigger winch is currently out of my budget, the pain is also not strong enough to justify 2000++$ My Jeffcat is a strong and nice boat but it's a custom build and some of the solutions are not optimal, maybe the builder has also tried to safe money.

So it would be very unusual having a 2:1 purchase in the genoa sheet on a cat of this size? On small cats that's pretty standard, isn't it?
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Old 11-10-2017, 23:11   #6
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Re: 2:1 purchase for genoa sheet

The blocks hanging off the clew may need to be quite substantial for the load and may make quite a dent in anything they hit. You can of course go to a smaller diameter sheet - say 10mm as the load is split. Downside is twice as much sheet to pull in on each tack, and in light air reaching/running all that weight on the clew may cause the sail to collapse earlier than normal.
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Old 11-10-2017, 23:41   #7
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Re: 2:1 purchase for genoa sheet

It does sound like bigger winches would be the best solution. You don't need 16mm rope. 12mm double braid would be adequate. I have a similar size headsail and12mm was fine. I have now recycled my 12mm spectra halyard into the headsail sheets, and it's excellent.
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Old 12-10-2017, 06:28   #8
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Re: 2:1 purchase for genoa sheet

sounds to me like a non-overlapping jib with but one sheet and a traveller. Going 2:1 on this set up is a fine solution.
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Old 12-10-2017, 09:36   #9
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Re: 2:1 purchase for genoa sheet

You don't want a block at the clew. It's going to flail around every time you tack and one day you'll have to clear something and it will beat your head in!!
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Old 12-10-2017, 09:44   #10
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Re: 2:1 purchase for genoa sheet

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You don't want a block at the clew. It's going to flail around every time you tack and one day you'll have to clear something and it will beat your head in!!
Agree... flogging clew block would be extremely dangerous to crew and (if overlapping) equipment.

Also, securing one end of the sheet to a fixed eye is going to effectively change your genoa sheet lead angles. Possibly so much that your existing track won't be long enough to get the necessary sheet angle at various points of sail.

I wouldn't even consider doing it.
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Old 12-10-2017, 10:32   #11
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Re: 2:1 purchase for genoa sheet

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You don't want a block at the clew. It's going to flail around every time you tack and one day you'll have to clear something and it will beat your head in!!
Yep, I think I still have the scar. Once when I was very young and a little more foolish I tried this. I dont recommend it.
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Old 12-10-2017, 10:39   #12
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Re: 2:1 purchase for genoa sheet

BTW Kudi, welcome aboard!
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Old 12-10-2017, 10:58   #13
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Re: 2:1 purchase for genoa sheet

By what criterion, precisely, do you judge your sheet loads to be "too high"?

Some of the strain taken by the sheet is vectored into the hull at each turning block, and the residual is taken radially by the winch. If your fittings haven't ripped out of the hull, then the sheet forces are clearly not "too high". She's like Custer's 'orse - she can take it :-)!

Another question entirely is whether YOU (and/or crew) are up to cranking the winch. If not, then you need bigger winches. That's why the big boys use "coffee grinders". Alternatively, luff 'er for a moment, harden up the sheet and fall off again. Mark you sheets with a whipping at the points where they enter the winch when correctly trimmed for being hard on the wind, then harden to there as you come through the eye of the wind, before the sail fills on the new tack. Just a question of timing, really. Provided, of course, you don't make the crew's life difficult with too many turning blocks and other bits and pieces that introduce unnecessary friction :-)

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Old 12-10-2017, 13:13   #14
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Re: 2:1 purchase for genoa sheet

So far as the clew block flogging around and being "dangerous," what about the newer self-tacking-jib systems (e.g., on the Catalina 425) that use exactly that set up?
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Old 12-10-2017, 13:24   #15
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Re: 2:1 purchase for genoa sheet

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So far as the clew block flogging around and being "dangerous," what about the newer self-tacking-jib systems (e.g., on the Catalina 425) that use exactly that set up?
Thats a small jib, not a genoa. the single block is small, and when tacking the sheet load doesnt change as the clew is chased across the deck by a traveller car.
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