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Old 13-02-2016, 05:51   #46
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Re: Broken jib sheet questions

Quote:
Originally Posted by estarzinger View Post
^^

I would go with dyneema definitely. For two reasons - one is you have those expensive sails, a shame to "crippled" them with a stretchy sheet. And at least my experience was the total cost of ownership was not much different because the dyneema lasted much longer (because no stretch means no chafe).
It's also not necessarily any more expensive to buy in the first instance, actually it can be cheaper if like for like is chosen on a strength basis. I have just priced up some for Dockhead. Using the bluefaible website, where they have a big choice of large sizes. The polyester Hercules 20mm with a breaking strength of 7000kg costs 9.52 EUR/m inc tax and the dyneema Regatta 2000 in 12mm with a 7200kg breaking strength costs 8.38 EUR/m inc tax.

Didn't you feel any extra shock transmitted by the dyneema sheets?

How did you manage going to (I presume you did) much thinner rope? - it won't be as easy on the hands when pulling in the sheets whilst tacking.
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Old 13-02-2016, 05:54   #47
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Re: Broken jib sheet questions

50mm of stretch is huge with sails like that. And the sail will be "panting" which will disrupt the airflow. Yea a racer would think it terrible.

Yes, shock loads will increase. everything in the system needs to be strong. You may well break something else just after you switch if you have a weak point. When we switched outer main sheet we blew up our vang on the first jibe.

I have always found 12mm to be comfortable enough . . . But I guess I have small hands.
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Old 13-02-2016, 06:47   #48
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Re: Broken jib sheet questions

Quote:
Originally Posted by poiu View Post
It's also not necessarily any more expensive to buy in the first instance, actually it can be cheaper if like for like is chosen on a strength basis. I have just priced up some for Dockhead. Using the bluefaible website, where they have a big choice of large sizes. The polyester Hercules 20mm with a breaking strength of 7000kg costs 9.52 EUR/m inc tax and the dyneema Regatta 2000 in 12mm with a 7200kg breaking strength costs 8.38 EUR/m inc tax.

Didn't you feel any extra shock transmitted by the dyneema sheets?

How did you manage going to (I presume you did) much thinner rope? - it won't be as easy on the hands when pulling in the sheets whilst tacking.
I would surely not go all the way down to 12mm from 20mm .

I'm deciding between 14mm and 16mm myself.

The Liros Racer 16mm has 12 600 break strength and max 1.5% stretch at break. The 14mm is 9 500.

My 18mm Marlowebraid had 10 000 break strength and 4% stretch at breaking.

Your yankee jib must be 150% of the size of mine, or more, if it's proportionate to displacement (I'm 20 long tons light ship).



I wonder what Evan thinks about stripping the cover of the ends of the sheets? This would reduce windage and improve the diameter ratio of the car sheaves. But more vulnerable to chafe or snags? UV?
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Old 13-02-2016, 07:07   #49
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Re: Broken jib sheet questions

Further to economics:

14mm Liros Racer (or Regatta 2000 -- what's the difference?) is about 12 euros (thanks for the link Poiu).

So each 21 m sheet will cost me 252 euros. You're right -- that's not all that bad. I have been paying 2.60 pounds for 18mm Marlowebraid (I have a good connection for that), which is about 3.35 euros. A 21m sheet is about 70 euros. Obviously a big difference, but chump change compared to the cost of the sails.

I might be able to do better on the price through my "rope pusher".
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Old 13-02-2016, 08:32   #50
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Re: Broken jib sheet questions

Quote:
Originally Posted by Dockhead View Post
Further to economics:

14mm Liros Racer (or Regatta 2000 -- what's the difference?) is about 12 euros (thanks for the link Poiu).



I might be able to do better on the price through my "rope pusher".
I think the main difference is that the Racer has a different cover advertised as suitable for winches. Maybe the better choice.

Quote:
Originally Posted by 44'cruisingcat View Post
I would have thought your sheet loads would be higher than that. When mine broke I estimate there was about 2000kg on it. Still far less than the breaking strain for new rope, but that's the point - it wasn't new.

I would have thought, with a far bigger headsail there would be much bigger loads on your boat.
Quote:
Originally Posted by Dockhead View Post
I'm deciding between 14mm and 16mm myself.

Your yankee jib must be 150% of the size of mine, or more, if it's proportionate to displacement (I'm 20 long tons light ship).
As to sizing. Sail area increases a little bit less than displacement proportionately. I have a 1250 sq ft yankee with a max true wind speed of 18kt before I reef. That gives 24.3kt apparent. Harken's calculator gives me a jib load of 1,450kg. Increase that to cover the jib car de-rating of 30%, build in a 3X safety factor and another 35% derating for UV losses on covered dyneema and I have a target minimum new sheet load of 9,550kg.

Dockhead - can you get prices from your 'pusher' for me when you get your quote re-done. 2 x 31m in 14mm. It may help us both.
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Old 13-02-2016, 08:56   #51
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Re: Broken jib sheet questions

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. . . Dockhead - can you get prices from your 'pusher' for me when you get your quote re-done. 2 x 31m in 14mm. It may help us both.[/FONT]
With pleasure. I'll get an alternative quote for 16mm for you as well.
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Old 13-02-2016, 09:03   #52
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Re: Broken jib sheet questions

A follow up question for Evan and the other experts:

How would you attach a Dyneema sheet to the clew?

I'm thinking soft spliced eye at the end of the sheet, and a soft shackle.

9mm D12 single braid has breaking strength of 7 tons, so the strength of a shackle made from this should be 14 tons minus the losses inherent in the knots and turns.

Does that sound ok?

And would you make the shackle yourself, or buy one? I have learned to make these myself (inspired by Seaworthy Lass, who gifted me a couple of hers), but I'm not sure if I would trust them in such a critical place.

I guess the eyes could be led through the clew cringle and then belayed with some kind of toggle. Is there a best practice for this? Surely the racers have huge experience with this.
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Old 13-02-2016, 09:59   #53
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Re: Broken jib sheet questions

I would definitely put an eye in the end of the sheet. Then it is a question of whether you change the sail or sheet "frequently". If not, and I think most cruisers do not, then I would go with a lashing between the eye and sail - lower profile possible. But if you do change sheets or sails with some frequency then the soft shackle is the better answer. There are various hardware solutions, but the textile solutions are the best answer. Some racing boats use "soft" shackles but with aluminum toggles rather than the stopper knot . . . Because those are stronger and easier to work with gloves. But I much prefer the all textile solutions, and the new "stronger" design eliminates the strength difference.
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Old 13-02-2016, 10:15   #54
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Re: Broken jib sheet questions

Quote:
Originally Posted by estarzinger View Post
I would definitely put an eye in the end of the sheet. Then it is a question of whether you change the sail or sheet "frequently". If not, and I think most cruisers do not, then I would go with a lashing between the eye and sail - lower profile possible. But if you do change sheets or sails with some frequency then the soft shackle is the better answer. There are various hardware solutions, but the textile solutions are the best answer. Some racing boats use "soft" shackles but with aluminum toggles rather than the stopper knot . . . Because those are stronger and easier to work with gloves. But I much prefer the all textile solutions, and the new "stronger" design eliminates the strength difference.
I don't know about Poiu, but I do change my headsail from time to time. When I had new sails made last year I had both a 120% yankee jib and a 90% blade jib made up out of the same carbon laminate cloth which Poiu uses. The blade is a Godsend for upwind work in stronger weather.

So I guess soft shackles it is. Just poke the end of the shackle through the cringle eye, and attach it to the eye in the sheet? Nothing else to it?
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Old 13-02-2016, 11:38   #55
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Re: Broken jib sheet questions

Here's the Wichard soft shackle:

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More strength with lighter line, by looping it through twice, and no knot. Very clever and nice. But we don't want any metal around the clew anywhere.

Maybe the normal kind of soft shackle without metal (preferable at the clew not to have any metal) could be made a bit longer and looped through twice, for the same effect.


Edit: Or made like Evans', here: http://www.bethandevans.com/pdf/improvedsoftshackle.pdf

That looks good. The four strands, he says, will give strength equal to almost 2.5x of the strength of a single strand. So 8mm SK75 (my usual single strand for splicing) should do it. Good. That's beautiful, Evans, thanks.
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Old 13-02-2016, 12:09   #56
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Re: Broken jib sheet questions

Once the sail is loaded and trimmed.... the stretch has occurred, adjust trim accordingly. The good news about conventional line is in sudden gusts etc, the additional stretch is a bit more forgiving on hardware etc. Just a thought.
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Old 13-02-2016, 12:34   #57
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Re: Broken jib sheet questions

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Originally Posted by Cheechako View Post
Once the sail is loaded and trimmed.... the stretch has occurred, adjust trim accordingly. The good news about conventional line is in sudden gusts etc, the additional stretch is a bit more forgiving on hardware etc. Just a thought.
Conventional sheets are definitely more forgiving on the hardware. But the stretch allows the sail to billow out under load (dynamically -- I think it's called "panting"). With Dacron sails it's maybe not so noticeable because the sails themselves are stretchy, but with laminate sails apparently it makes a difference.

I reckon Poiu must have the same genoa cars I do -- the jumbo Size 3 Lewmar ones, right Poiu? Safe working load of 5 tons, so I guess the sheet would break before you budged the hardware.
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Old 13-02-2016, 16:56   #58
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Re: Broken jib sheet questions

Soft shackle for clew . . . . SL's last effect was a very elegant design. I would modify it just a bit by burying the tails longer (to make it stronger) and making the whole soft shackle longer to allow your "double wrap" thru the clew (and it also gives you more room for the longer bury). I think that's the most elegant and appropriate solution for your "occasional" sail change.

But really any of the soft shackle designs will work. They are really astonishingly strong.
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Old 14-02-2016, 08:12   #59
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Re: Broken jib sheet questions

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I reckon Poiu must have the same genoa cars I do -- the jumbo Size 3 Lewmar ones, right Poiu? Safe working load of 5 tons, so I guess the sheet would break before you budged the hardware.
Yes, I think I have that one, but of the previous generation design.

If the rope has a breaking load say at 10 tons and the car has a SWL of 5 tons and the breaking load with a safety factor of two only is 10 tons then it's going to be an interesting game of chicken.
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Old 14-02-2016, 08:21   #60
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Broken jib sheet questions

I know some do not like polyester rope for sheets but this stuff is really tough and lasts "forever" in the sun. It is easy on the hands too. But not very "high tech" thus its low price.

shop.mariner-sails.com/Intrepid-8-Strand-Plait-INTREPID-38.htm
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