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PostPosted: Fri Apr 13, 2007 2:22 am 
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Joined: Thu Feb 22, 2007 11:28 pm
Posts: 47
Location: Australia
Looks like I'm the only one with questions here!

After the doing the nationals in a bit of breeze I I've got a much better idea of how I want my boat setup with control lines and such. I'll still keep it simple, but I definitely need jib in/out easily accesible and some carriage control.

While I'm at it laminating some brackets for cleats I'm considering adding adjustable shrouds as well. I won't be playing with them just yet, but it would be good to incorporate future needs now before I paint the deck.

What kind of purchase do you run on the shrouds? I've seen some pictures of what looks like 12:1. With that kind of purchase I guess you can't tighten the windward shroud under load. But is it enough to get rig tension ashore? I'm thinking of making the forestay fixed, both to save weight fwd, save money (can use the purchase on one shroud). A fixed forestay makes it easier to set up a proper jib cunningham as well.


Kristoffer Aus 6


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PostPosted: Fri Apr 13, 2007 8:47 am 
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Not completely sure as I’m at work and not looking at the boat... however 245 is, I believe, 24:1 and Id say this was the minimum that you require if you want to adjust it on the water. However I’ve never sailed any other Canoe so cant be sure but mine works fine with a tug.

Not cheap though when you have two sides to do and it really do need dot use good quality blocks!

Ian
245
Stately Lord Sturgis


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 Post subject:
PostPosted: Fri Apr 13, 2007 8:47 am 
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Joined: Mon Jul 31, 2006 6:35 pm
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Not completely sure as I’m at work and not looking at the boat... however 245 is, I believe, 24:1 and Id say this was the minimum that you require if you want to adjust it on the water. However I’ve never sailed any other Canoe so cant be sure but mine works fine with a tug.

Not cheap though when you have two sides to do and it really do need dot use good quality blocks!

Ian
245
Stately Lord Sturgis


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 Post subject:
PostPosted: Fri Apr 13, 2007 12:42 pm 
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Joined: Fri Aug 01, 2003 2:26 pm
Posts: 164
The real merit of having the shrouds on tackles is the ability to cast off the lee shroud on the run.
So actually being able to "adjust them under load" isn't the issue.
You just have to be able to get back to where you started.
Currently I have an 18:1 cascade. 3:1 at the chain plate, 6:1 on the deck. Greymatter has 12:1. Neither of these is "fingertip" controls but require a wrap of the hand and a pretty mighty heave to get the rig all the way on.
You want quite a bit of travel in the shroud, in the order of 150-200mm to get the full benefit of getting the main way out without distorting the battens.
SHC

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PostPosted: Sun Apr 15, 2007 8:42 am 
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Joined: Wed Sep 07, 2005 9:54 pm
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Location: Australia
Kris,
Have a look at the NS14 fleet at Teralba, They use tracks along the gunwales, fixed length stays and simply run the cars forward when the boom needs to go out square. They have only a 2:1 purchase to pull the cars back again. Seems simpler than high ratio tackles.
Phil S

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PostPosted: Sun Apr 15, 2007 11:23 am 
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Location: Australia
Just like what Tim (http://www.twyachtdesign.com) put on my boat, simple and works well

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PostPosted: Mon Apr 16, 2007 2:11 am 
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Joined: Thu Feb 22, 2007 11:28 pm
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Location: Australia
I like the tracks for this application. Moving forward is exactly what you want to achieve, and the track achieves this with less slacking of the shroud than the tackle.

My plan was not to mess with the chainplates though. They look scary, just a saddle bolted down (hopefully with something below!). They seem to be holding up fine, just need to be careful not to add to much inboard load from the tackle. If I do 3:1 at the shrouds the resultant load on the chainplate will just increase marginally. The Harken wire blocks are the neatest blocks around for this kind of load, but they don't come in the double I need for the 3:1. Anyone knows of any other small blocks up to the job?


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PostPosted: Mon Apr 16, 2007 1:41 pm 
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I use two singles.
This has the advantage that the individual sheaves lie properly to their loads and don't have to compromise with each other.
If this means adding a strap to the boat, it shouldn't be a big deal.
Getting the foundation right for tracks is pretty hard and the whole mess does move the shrouds 1nboard quite a bit.
SHC

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 Post subject: Re: Adjustable shroud setup
PostPosted: Fri Dec 09, 2011 10:47 pm 
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Location: Pittwater, Sydney Australia
Bit of a re-hash of an old post but I have some more questions. If you're just using the adjustable shrouds to let the leeward one off down wind, how do you make sure that both are the same length going upwind again? If you don't get them the same you will end up with the rig canted out to one side and strange things happening to the sideways bend. I guess marks on the ropes would help a bit but if it's only a couple of mm's out it will still have a huge effect.

Geoff

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 Post subject: Re: Adjustable shroud setup
PostPosted: Fri Dec 09, 2011 11:55 pm 
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Joined: Fri Jul 18, 2003 11:12 pm
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Location: United Kingdom
Marks on rope seems to work pretty well. I have my marks after 6:1 of the purchase system, as I find its easier to have different settings according to mast rake marked in that part of the boat. Even if there is 3mm difference it translates to 0.5mm for the shroud length. To reduce discrepancy between shrouds, ideal to have them after all the purchases e.g. by the cleat, so on a 18:1 system, being out by even a 10mm, will have a much less effect on the length of the shrouds. In fact, not sure it makes a great difference if the mast is canted one way or the other - boat's heel will make more difference.

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 Post subject: Re: Adjustable shroud setup
PostPosted: Sat Dec 10, 2011 1:17 am 
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Yeah, I know what you're saying about heeling. I was thinking more about having the mast going through a gate which doesn't move laterally then having it lay off to one side, putting a sideways bend in. Marks further into the purchase system would be better for sure.

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 Post subject: Re: Adjustable shroud setup
PostPosted: Mon Dec 12, 2011 11:52 am 
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Joined: Fri Dec 22, 2006 10:32 pm
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Location: United Kingdom
I've been playing around with some of the new tie on blocks and a dyneema shroud adjustment on my new IC. The worry I have is what is the loading in these blocks? There is very nice Ronstan 20mm block which ties on to the shrouds which has a working load of 250kg and breaking load of 500kg and is the same as the Harken wire blocks spec but weighs only 9grams. I took the boat out in 30 knots with good 35knot gusts the other week and they held up with no sign of damage but it would be nice to calculate for certain what is needed here.

What works and what breaks is my question?

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 Post subject: Re: Adjustable shroud setup
PostPosted: Tue Dec 13, 2011 7:44 pm 
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Joined: Tue Oct 10, 2006 10:45 pm
Posts: 110
Location: USA
Steve,
By my calculations your mast should have fallen over the side.

With my 90kgs on the end of the seat I figure there's about 550kgs on the weather shroud. Coming off a wave that may, what, double? Couldn't be too much more or my mast would have fallen over too.

I have a Harken #313 wire block on the shroud. That has a 700kg swl.


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 Post subject: Re: Adjustable shroud setup
PostPosted: Wed Dec 14, 2011 9:44 am 
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Joined: Fri Dec 22, 2006 10:32 pm
Posts: 522
Location: United Kingdom
Thanks for that Chris - that does make sense. I had a shackle on the shroud holding one of the blocks on and the pin had bent slightly which worried me :oops: Wouldn't the the pulley on the shroud base actually take twice the load as it turns the rope through 180 degees? This would mean even the block you have specified might be a bit on the edge. Perhaps a solid non rotating element is needed here instead. What about the cascade, do they need to be the same spec?

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 Post subject: Re: Adjustable shroud setup
PostPosted: Wed Dec 14, 2011 5:17 pm 
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Joined: Tue Oct 10, 2006 10:45 pm
Posts: 110
Location: USA
The load on that primary block is the same as the load on the shroud. The load on the cascade is some fraction of that depending how many blocks from the shroud it is. For instance, I have a single block with a becket on the shroud and two single blocks on the chainplate. Those blocks share the shroud load - not quite equally but I'm not sure how the load is distributed, I'm guessing something like 65%-35% - and so can be lighter than the primary block. That gives me a 3:1 purchase at the shroud. The 6:1 cascade attached to that 3:1 purchase can be relatively light, I think I'm using Ronstan 20 blocks there, because that purchase only needs to handle one third of the shroud load.

Maybe someone else will come along and explain this more clearly!


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