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Anatal 2:1 block


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#1 Editor

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Posted 02 May 2007 - 03:18 AM

Big Pimpin'

Block Head
You can now replace that gigantic web block at your headboard for your 2:1 halyard system with a block hardly bigger than your standard halyard shackle. Antal Hardware has created a 2:1 halyard block that is CNC cut out of a solid piece of 17-4ph Stainless steel. The result is a tiny block with extremely high working loads. The version used by the Farr 40 class is only about 2 inches long with a 26 mm sheave, has a 3000lb working load, and weighs 3 oz. Less weight aloft. It's a good thing. get in touch with Euro Marine Trading for more info.

Have any of you anarchists used these?

05/02/07

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#2 Pete M

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Posted 02 May 2007 - 03:38 AM

what ever happened to 8 to 1 D/d for shieve sizing for composite line? Is it because it is not moving after it is up , or are the halyards just that strong?

#3 thalattaII

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Posted 02 May 2007 - 06:00 AM

These blocks are damn good. Use one on the boat i sail on, and it is much better then what we used before. They held all through ft lauderdale to key west and back, montego bay and back, miami race week, and up to charleston, damn good, and much easier then anything else, plus it puts a lot less weight a loft for the strength, durability, and ease which it provides.

#4 Rolls Ross

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Posted 02 May 2007 - 10:25 AM

These blocks are damn good. Use one on the boat i sail on, and it is much better then what we used before. They held all through ft lauderdale to key west and back, montego bay and back, miami race week, and up to charleston, damn good, and much easier then anything else, plus it puts a lot less weight a loft for the strength, durability, and ease which it provides.


Do they have a captive pin?

Who is the distributor in Oz?

#5 drew@usa650.com

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Posted 02 May 2007 - 01:00 PM

Do they have a captive pin?

Who is the distributor in Oz?


Yeah, they have a captive pin, and your distributor is G.I.N.E.I.CO
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#6 ISpyToo

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Posted 03 May 2007 - 09:38 AM

cool, what are the working loads?

#7 Presuming Ed

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Posted 03 May 2007 - 09:45 AM

cool, what are the working loads?


Google is your friend. http://www.antal.it/...zelli/Start.htm

#8 Mid

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Posted 03 May 2007 - 10:13 AM

cool, what are the working loads?


forget google this time and read the Ed's OP ................................

has a 3000lb working load



#9 drew@usa650.com

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Posted 03 May 2007 - 01:05 PM

forget google this time and read the Ed's OP ................................


Actually, Google is your friend in this case. If you read the Ed's OP closely.. .it says the version used by the Farr 40 class has a WL of 3000lbs. There's two other sizes as well... three total. (see antal's website!)
HO20 - WL 1300kg for 8-10mm line
HO30 - WL 2200kg for 10-12mm line
HO40- WL 3500kg for 12-14mm line

#10 sockeye

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Posted 04 May 2007 - 05:22 AM

So, I've been hoisting my main the old fationed way and reducing the weight of my halyards over the years with better and better lines. Sell me another few ounces and double the length of my halyard. I was on a 34' sportboat that had two to one halyard and I just did not get it. Splain it to me.

#11 Christian

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Posted 04 May 2007 - 06:51 AM

So, I've been hoisting my main the old fationed way and reducing the weight of my halyards over the years with better and better lines. Sell me another few ounces and double the length of my halyard. I was on a 34' sportboat that had two to one halyard and I just did not get it. Splain it to me.


With big roaches - what you will find is that as a gust comes on - if you have just a little give in the main halyard your nicely flattened and de-powered main will get powered up as the hally stretches - the exact opposite of what you need. Hence for a veeeery low stretch halyard. 2:1 helps a fair bit.

#12 KEGER

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Posted 04 May 2007 - 11:05 AM

cool, what are the working loads?


Here's complete information on the block

http://www.apsltd.co...000/e275720.asp

KEG

#13 sockeye

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Posted 05 May 2007 - 10:50 PM

With big roaches - what you will find is that as a gust comes on - if you have just a little give in the main halyard your nicely flattened and de-powered main will get powered up as the hally stretches - the exact opposite of what you need. Hence for a veeeery low stretch halyard. 2:1 helps a fair bit.

I must not be able to picture this right. If we start with the main lowered, The halyard is pinned to the crane, then it comes down to the head board and the Anatal. Then the haly goes back up to the sheave at the top of the mast, then back down the inside of the mast to the winch or whatever.
If this is right, when you hoist the main all the way to the top., does it become two blocked at the sheave or is it still down a few inches.

On the boat I was on, as on mine, the main was hoisted as far as it would go. In my head, subjected to 51 years of substatial abuse, that instantly eliminates the 50% loading that was gained by the aditional purchase(read that both way$).

#14 cicindela_tiger

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Posted 08 May 2007 - 03:29 AM

=====
On the boat I was on, as on mine, the main was hoisted as far as it would go. In my head, subjected to 51 years of substatial abuse, that instantly eliminates the 50% loading that was gained by the aditional purchase(read that both way$).
=====

There's a cool thing called mechanical advantage - putting the mainsail halyard on a 2:1 purchase results in:

1/4 reduction in spar compresson due to halyard load (1/2 reduction if you use a masthead halyard lock)
1/2 load into the longest part of the halyard (the part going from masthead to deck).
1/2 load into a very short section of the halyard (the part going from mainsail headblock to top of spar.

And minimal additional weight in the spar. You can reduce the halyard size even more and perhaps pay for the weight of the block by reducing the weight of the halyard.

- beetle

#15 sockeye

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Posted 08 May 2007 - 06:43 AM

=====
On the boat I was on, as on mine, the main was hoisted as far as it would go. In my head, subjected to 51 years of substatial abuse, that instantly eliminates the 50% loading that was gained by the aditional purchase(read that both way$).
=====

There's a cool thing called mechanical advantage - putting the mainsail halyard on a 2:1 purchase results in:

1/4 reduction in spar compresson due to halyard load (1/2 reduction if you use a masthead halyard lock)

So lets take your claim to its logical conclusion. If you used a 10:1 purchase, The spar compression is reduced to what? 20%. I put this Q to one of the leading structural engineers in Seattle, I set up the question by comparing the mast to a crane derrick, If you lift 10,000lbs with a 60:1 cascading purchase you can lift the weight with a Iron age rope and 10hp engine, but does the derick still see the entire weight of the load or is it magicly reduced to 167lbs wherby I could support it with a 2x4. I'm not sure about the concequences of extreme spar compression. I think that strength is covered by engineering for 40knot gusts. I'm sure there is some flaw in my ointment,but you conveniently avoided the question in your flip answer: What happens when you two block the shitteree at the top? I personally would be looking at that extra 45 feet of 2.00 line sittng in a heap at my feet.

#16 Christian

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Posted 08 May 2007 - 07:08 AM

So lets take your claim to its logical conclusion. If you used a 10:1 purchase, The spar compression is reduced to what? 20%. I put this Q to one of the leading structural engineers in Seattle, I set up the question by comparing the mast to a crane derrick, If you lift 10,000lbs with a 60:1 cascading purchase you can lift the weight with a Iron age rope and 10hp engine, but does the derick still see the entire weight of the load or is it magicly reduced to 167lbs wherby I could support it with a 2x4. I'm not sure about the concequences of extreme spar compression. I think that strength is covered by engineering for 40knot gusts. I'm sure there is some flaw in my ointment,but you conveniently avoided the question in your flip answer: What happens when you two block the shitteree at the top? I personally would be looking at that extra 45 feet of 2.00 line sittng in a heap at my feet.


You will never get under 50% and that would require an infinite purchase (or a halyard lock) as you still have the compression load from the main but reduce the halyard load. Look at it this way:

Halyard tension 1000 lbs this gives a compression load of 2000 lbs (1000 from the halyard and 1000 from the main) - this is twice the load. Now reduce the halyard load by 50% by using a 2:1 halyard and you now have a compression load of 1500 lbs (500 from halyard and 1000 from main) and voila - a 25 % reduction.

In your crane example the compression load would be 20,000 lbs if you use a 1:1 (i.e. no purchase) - at 60:1 it would be 10167 lbs - close to half.

For that you don't need the leading structural engineer - it's really quite simple

#17 cicindela_tiger

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Posted 08 May 2007 - 02:58 PM

I'm sure there is some flaw in my ointment,but you conveniently avoided the question in your flip answer: What happens when you two block the shitteree at the top? I personally would be looking at that extra 45 feet of 2.00 line sittng in a heap at my feet.


Sorry, I wasn't trying to be flip in my answer.

Approach the problem this way: the spar supports the entire weight of the mainsail, there's no way around that. The adjustable loading is in how much tension is on the length of the halyard that runs from the masthead to the deck (the fall line). On a 1:1 halyard the fall line has the same load as the mainsail and the mast sees 2x the mainsail load at the maststep as compression.

On a 2:1 halyard the fall line carries 50% of the mainsail load and the mast sees 1.5x the mainsail load (1x from the sail, .5x from the fall line). The other 50% of the mainsail load is captured in the 2:1 block and tackle at the masthead and does not apply compression down the length of the spar. There is compression between the dead end of the halyard (presumably to a U-bolt at the masthead) and the mast sheave, and this compression is captured at the top of the mast and does not contribute to compression running the length of the spar to the mast step.

Even if you two-block the headboard block, there will still be a turn of halyard from the U-bolt fixing at the masthead, down to the bottom edge of the headboard block sheave, and back up to the mast sheave.

Theoretically, if you could apply sufficient tension that the mainsail halyard went bar-tight and the headboad block was now riding fore-aft along the bit of halyard running between the U-bolt and the mast sheave, at that point you have lost the mechanical advantage of the headboard block and the fall line again sees 100% of the mainsail load (or more, depending on how much tension you had to apply to the fall line to get the halyard to go bar-tight). If the mainsail is cut so tall that the luff really does go 100% of the way to the masthead, then there is no clearance for 2:1 halyard block will not fit and is of no value.

Does that make sense? It is somewhat counter-intuitive, I find it easiest to draw out on paper.

As you point out, hopefully the mast designers made the spar strong enough to handle the compression load applied by the halyards and sails. On a practical matter, I replaced the 1:1 mainsail halyard setup on my boat with a 2:1 to make it easier for me to hoist and reef/unreef the sail - 450 square foot main on a 60' spar. Reducing load in the halyard leading to the Antal clutch meant I could use a smaller clutch and still stay well below the clutch's breaking load.

For the race boats (Volvo 70s, for example) using masthead halyard locks means the spar designer could reduce spar compression load by 50% (and therefore make the spars much lighter or thinner), which is huge when you figure the load includes loads from the code zeros, giant mains, and the equally loads jibs. For just about everybody else, including me, that is not sailing a custom super-lightweight mast, the practical benefit of a 2:1 mainsail halyard is to make it easier to raise and adjust the mainsail under load.

- beetle

#18 Rented Mule

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Posted 08 May 2007 - 04:58 PM

How does this change if the halyard cleats on the mast? I'm assuming the advantages would be less load on the cleat and easier sail raising. Does a 2:1 have an effect on mast compression in this case?

#19 cicindela_tiger

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Posted 08 May 2007 - 06:32 PM

How does this change if the halyard cleats on the mast? I'm assuming the advantages would be less load on the cleat and easier sail raising.

Right.

Does a 2:1 have an effect on mast compression in this case?

Yes. The compression due to sail loading, which the spar must support between the cleat and the masthead sheave, has been reduced by 25%. The compression due to sail loading has been reduced by 50% between the mast step and the cleat. If you move that cleat to the masthead (e.g., a halyard lock), you have reduced sail loading compression by 50% in the entire spar.

- beetle

#20 boatschit

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Posted 08 May 2007 - 09:47 PM

... I've tried calling Euro Marine a few times, send emails and they have not returned my calls.

If Euro Marine is lurking here, it would be nice to get a call back from you...

#21 Asymptote

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Posted 08 May 2007 - 10:07 PM

So we just pass our 2-part halyard through a fat shackle at the top. Same contact area as a spliced halyard, even less weight, just one moving part, cheaper, goes up and down just fine...what's wrong with that?

#22 cicindela_tiger

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Posted 08 May 2007 - 11:34 PM

So we just pass our 2-part halyard through a fat shackle at the top. Same contact area as a spliced halyard, even less weight, just one moving part, cheaper, goes up and down just fine...what's wrong with that?


Simple is always better, and bombproof is best.

There's a fair bit of information available on the web regarding compression failure of hi modulus line (the US military in particular has been working on replacing wire rope with high modulus line), and it appears that HM line, while enormously strong in tension, is quite weak in compression or crushing loads. When a line is bent around a sheave, the outer threads are in tension, the inner threads are in compression, and it appears the inner threads are the ones that break.

The tension/compression profile across the line diameter gets worse as the sheave diameter gets smaller. Pulling a 1/4" diameter halyard around a 1/4" pin diameter puts a lot more tension/compression stress on the line than pulling around a 1" sheave (the Antal mini-halyard block), and that's still not as good as the 50mm diameter sheave on a hi-load Harken block. Larger diameter is always better for the line.

Actively pulling a line 180 degrees around a fixed pin or rotating diameter sheave is significantly different from a fixed eye splice to a pin. There is no bend/straighten event with the eye splice, whereas pulling a rope around the pin/sheave causes each fiber to bend and straighten, which in turn applies continually changing tension/compression forces to the fibers.

And tying knots in HM appears to apply large crushing loads to the fibers, which they don't like either. I've seen comments that a knot can reduce the line's load handling by 70%.

However, if it works for you on your boat then the loads must be less than the line can handle, and you've got a simpler, cheaper solution than an expensive fancy block with moving parts.

- beetle

#23 sockeye

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Posted 09 May 2007 - 04:53 AM

thank you Beetle for the illumination. Your desription is quite adequate for visualisation. I have some further problems with perceived neccessity of this solution(the block). It seems that the small sizes of the block is aimed at boats like mine and the 34' sport boat. neither of these boats ever reef. the main can be raised to the top by hand without aid of winch or purchase. the hoist is 40' of 3/8" bolt rope.

So I don't need it for sail handling. What are the real main sail loads that I am trying to reduce. Quantum made mains for several years that had no tack at all. So there was only leech tension left to contribute to mast compression and at least some of the main sheet load is taken by the mast track. My best guess is from a Cal 40 that I recently trimmed main on that used a rough/fine purchase. I could trim almost every thing in 22knots with the rough purchase(5:1) and I can only guess that with no great place to stand the best I could pull was 200lbs. that might be high be cause when I went to the fine 4:1 it seem like about 20 or 30lbs. So is it correct to assume 30x20=600lbs of sheet tension in gusty 20knot wind. If I use 5/16 inch Amsteel (10500lbs- .46% stretch at 10% of break strength) I get about 1 1/3 inches of stretch. Is this right. most of the boats I've sailed on had nowhere near this strong/stiff a halyard and I never noticed this kind of stretch in very windy conditions. I would think that baring a halyard lock I would easily opt for the stiffness of cable even at the expense of the weight.

If I am wrong and the halyard really never stretches that much, the Asymptotes notion gains merit because the load of hauling the main is not much, and if the haly never stretches then there is no movement at load and the bend becomes much like an eye spice around a pin. Hardware is cool stuff but we still need to stay in the real world not some AC rigger$ dream.

#24 Christian

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Posted 09 May 2007 - 05:30 AM

thank you Beetle for the illumination. Your desription is quite adequate for visualisation. I have some further problems with perceived neccessity of this solution(the block). It seems that the small sizes of the block is aimed at boats like mine and the 34' sport boat. neither of these boats ever reef. the main can be raised to the top by hand without aid of winch or purchase. the hoist is 40' of 3/8" bolt rope.

So I don't need it for sail handling. What are the real main sail loads that I am trying to reduce. Quantum made mains for several years that had no tack at all. So there was only leech tension left to contribute to mast compression and at least some of the main sheet load is taken by the mast track. My best guess is from a Cal 40 that I recently trimmed main on that used a rough/fine purchase. I could trim almost every thing in 22knots with the rough purchase(5:1) and I can only guess that with no great place to stand the best I could pull was 200lbs. that might be high be cause when I went to the fine 4:1 it seem like about 20 or 30lbs. So is it correct to assume 30x20=600lbs of sheet tension in gusty 20knot wind. If I use 5/16 inch Amsteel (10500lbs- .46% stretch at 10% of break strength) I get about 1 1/3 inches of stretch. Is this right. most of the boats I've sailed on had nowhere near this strong/stiff a halyard and I never noticed this kind of stretch in very windy conditions. I would think that baring a halyard lock I would easily opt for the stiffness of cable even at the expense of the weight.

If I am wrong and the halyard really never stretches that much, the Asymptotes notion gains merit because the load of hauling the main is not much, and if the haly never stretches then there is no movement at load and the bend becomes much like an eye spice around a pin. Hardware is cool stuff but we still need to stay in the real world not some AC rigger$ dream.


Okay - stretch - now we are actually in the topic where 2:1 halyards gain even more advantage. Since you reduce the halyard tension by 50% you get only half the stretch - on top of that - due to the 2:1 purchase the main "sees" only half of that and you have effectively reduced your stetch by 75% with the same halyard material/dimension.

On my boat it makes a huge difference. I have a very large roach (think about something in the 65% of the triangle region). and the boat is what most people would call wastly overcanvassed - we are fully powered up in about 7 knots of breeze. Obviously this means that the boat is a handful in a blow. Used to have a 1:1 spectra halyard and what would happen when sailing in a good breeze (main flatttened as much as possible - including a fair amount of cunningham) and a gust came along was that the little amount of stretch that was in the halyard resulted in the roach not automatically falling off to leward and spilling air but actually the entire sail getting powered up (as the halyard stretching works the same as easing the cunningham) - not really what you want in that situation. With a Vactran 2:1 halyard the rig/main has become much more automatic in it's gust response as the head will fall off to leward and spilling now. Huge improvement! I don't use a block with a sheave for the halysrd shackle - just use a Ronstan alu headboard shackle, which I polished in the halyard "hole" to reduce chafe and friction.

One note of advice if using Vectran for this - add a 2-3 foot piece of Spectra at the masthead end of the halyard as it hs MUCH better chafe and UV resistance than Vectran. And since the halyard is already three times the mast height - add a 1/3 and make the halyard reversible - very economic way of doubling your lifespan of the halyard

#25 cicindela_tiger

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Posted 09 May 2007 - 07:04 AM

[quote name='sockeye' date='May 8 2007, 09:53 PM' post='1172409']
If I use 5/16 inch Amsteel (10500lbs- .46% stretch at 10% of break strength) I get about 1 1/3 inches of stretch. Is this right.
/quote]
Hi Sockeye -

I'm not arguing in favor of expensive rigging that can break - I am strongly in favor of simple, bullet-proof stuff. If you never reef the mainsail then you are realistically never moving the halyard under load - therefore there should not be a need for a large diameter sheave - a simple pin is good enough and does act like a splice.

Then the stretch game starts - there is no reason to go overboard on rigging size if it is not necessary - thicker line is stronger, stretches less, and costs more. And you want to minimize stretch in the halyard if possible.

Below are the numbers I came up with from Samson (maker of Amsteel Blue), for a Cal 40 with a P of 40 feet, assuming a halyard cleat on the spar at the gooseneck - if the halyard leads elsewhere then add the additional halyard length to calculate stretch. Your human effort values are just about right - 40 lbs of push/pull by a human arm is about right. I came up with 2.2 inches stretch, rather than 1.3 (about double the stretch from your numbers). If you have a really strong fish scale, hook it up between the mainsheet and the boom; with a 200lb fish scale you can hook up a 4:1 tackle so the scale only records 1/4 the load, the idea being to not destroy the scale, and see what the mainsheet loads really are.

Cal 40 P=40 feet, all loads to be less than 10% break load

1:1 halyard, 5/16" amsteel (10% strech @ 1,370 pounds)
leach load = 600 pounds
halyard load = leach load = 600 pounds
% of line breaking strength = (600/13700)x100 = 4
halyard stretch over 40' = 0.46x40x12/100= 2.2 inches
weight of halyard 40'x2.7/100 = 1.08 pounds
% of halyard stretch consumed: (600/1,370)x100 = 44

1:1 halyard, 3/8" amsteel (10% stretch at 1960 pounds)
leach load = 600 pounds
max halyard load = leach load = 600 pounds
% of line breaking strength = (600/19600)x100 = 3
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x3.6/100 = 1.44 pounds
% of halyard stretch consumed: (600/1960)x100 = 30

2:1 halyard, 1/4" amsteel (10% stretch @ 860 pounds)
leach load = 600 pounds
halyard load = 1/2 leach load = 300 pounds
% of line breaking strength = (300/8600)x100 = 3.5
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x1.6/100 = 0.64 pounds
% of halyard stretch consumed: (300/860)x100 = 35

2:1 halyard, 3/16" amsteel (10% stretch = 540 pounds)
leach load = 600 pounds
halyard load = 1/2 leach load = 300 pounds
% of line breaking strength = (300/5400)x100 = 5.6
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x1/100 = 0.4 pounds
% of halyard stretch consumed: (300/540)x100 = 55


This suggests that you could happily go with a 2:1 halyard using 1/4" amsteel and have 20% less stretch - ((44-35)/44)x100 = 20% - than you have with 5/16" on a 1:1, and you are still well within the 10% stretch limit and load factors for the halyard. The weight savings is 11 ounces at the middle of the mast (need to work out if there is any advantage given the additional weight of a block or a smooth shackle at the masthead). The 2:1 halyard will have the knock-on effect of a) making the sail easier to hoist, and B ) reducing compression in the spar.

The 3/16" amsteel on a 2:1 is easily strong enough, but the stretch is increasing at that point. It would be an interesting experiment to see if it is noticeable - at some point the mainsail fabric becomes important and perhaps the sail stretches more than the halyard; if so, a fancy halyard is not going to help leach control as the sail cloth stretch becomes the dominant factor.

To match a 2:1 1/4" amsteel halyard, it would take 1:1 3/8" amsteel - and that 3/8" line is more expensive and heavier than 1/4".

At least that's my take on it.

- beetle

#26 drew@usa650.com

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Posted 09 May 2007 - 01:55 PM

Hi Guys,

EMT can be contacted at sales@euromarinetrading.com if you have a question or comment. You can also reach us at 401-849-0060. We are here from 8:30-5:30 EST M-F. If it's busy or unanswered it is because it's Spring and we are very busy! Please leave us a message and we will get right back to you!

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Drew

#27 Pascal

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Posted 09 May 2007 - 02:24 PM

Quantum made mains for several years that had no tack at all. So there was only leech tension left to contribute to mast compression and at least some of the main sheet load is taken by the mast track.

We still order ours like that every year on the Laser 28. No tack. We do use a fair bit of cunningham though as soon as the breeze comes up, and our cunningham purchase is much more than 2:1 so we sill end up compression loading the mast quite a bit.

Very interesting discussion here (way out of my league), keep it up! :ph34r:

#28 sockeye

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Posted 09 May 2007 - 03:36 PM

Beetle, It looks like you might be using the Amsteel blue numbers, not that it makes much differenc if the results are dramatic enough. I used the Amsteel number because that is what I have for genoa halyard. I too came up with 2.2 inches of stretch at 10%, but I did a further linear assumption that if the leech load was 6% of break load I should multiply the 2.2 by .6. If this is right(i never found numbers for 5% of break) the your numbers get even better. Any how that is how Igot the 1.32"
It wuld be intersting to see a curve on the stretch from zero to 40%. Then we could select lines that started flat if we are mostly concerned with stretch at the low end and lines that flatten towards the middle if they are to be highly loaded. bla bla bla.

I first noticed the no tack mains when racing in good wind these boats just let the tack ride up the mast. Using the cunningham harkens back to sliding goosenecks. I guess sliders don't work so well with rigid vangs.

At what size rig does mast compression begin to be an engineering problem. once again I like to get a handle on things by going to extremes. On a Ross 930 (30') the mast is about the size of my forearm at the deck. just a little larger than a thistle mast. and has almost as much standing rigging. The shrouds are set up in the thousands of pounds and when you pull on the runner in 30+ knots which is where this boat is supposed to be great(once again, in six years we never reefed her) the compression load must be fantastic percentagewise to the mast section compared to my 6mR's massive stick. Does mast compression affect mast performance as in expected flex at the head etc.

I guess I should invent a sheave to fit in the cutout of my head board to assure max hoist, maintain the purchase and halyard lead angles. With every body going to flat heads I could market a carbo sheave headbord w/ batten sockets and become a bazillionaire.

#29 Christian

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Posted 10 May 2007 - 04:42 AM

Hi Sockeye -

I'm not arguing in favor of expensive rigging that can break - I am strongly in favor of simple, bullet-proof stuff. If you never reef the mainsail then you are realistically never moving the halyard under load - therefore there should not be a need for a large diameter sheave - a simple pin is good enough and does act like a splice.

Then the stretch game starts - there is no reason to go overboard on rigging size if it is not necessary - thicker line is stronger, stretches less, and costs more. And you want to minimize stretch in the halyard if possible.

Below are the numbers I came up with from Samson (maker of Amsteel Blue), for a Cal 40 with a P of 40 feet, assuming a halyard cleat on the spar at the gooseneck - if the halyard leads elsewhere then add the additional halyard length to calculate stretch. Your human effort values are just about right - 40 lbs of push/pull by a human arm is about right. I came up with 2.2 inches stretch, rather than 1.3 (about double the stretch from your numbers). If you have a really strong fish scale, hook it up between the mainsheet and the boom; with a 200lb fish scale you can hook up a 4:1 tackle so the scale only records 1/4 the load, the idea being to not destroy the scale, and see what the mainsheet loads really are.

Cal 40 P=40 feet, all loads to be less than 10% break load

1:1 halyard, 5/16" amsteel (10% strech @ 1,370 pounds)
leach load = 600 pounds
halyard load = leach load = 600 pounds
% of line breaking strength = (600/13700)x100 = 4
halyard stretch over 40' = 0.46x40x12/100= 2.2 inches
weight of halyard 40'x2.7/100 = 1.08 pounds
% of halyard stretch consumed: (600/1,370)x100 = 44

1:1 halyard, 3/8" amsteel (10% stretch at 1960 pounds)
leach load = 600 pounds
max halyard load = leach load = 600 pounds
% of line breaking strength = (600/19600)x100 = 3
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x3.6/100 = 1.44 pounds
% of halyard stretch consumed: (600/1960)x100 = 30

2:1 halyard, 1/4" amsteel (10% stretch @ 860 pounds)
leach load = 600 pounds
halyard load = 1/2 leach load = 300 pounds
% of line breaking strength = (300/8600)x100 = 3.5
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x1.6/100 = 0.64 pounds
% of halyard stretch consumed: (300/860)x100 = 35

2:1 halyard, 3/16" amsteel (10% stretch = 540 pounds)
leach load = 600 pounds
halyard load = 1/2 leach load = 300 pounds
% of line breaking strength = (300/5400)x100 = 5.6
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x1/100 = 0.4 pounds
% of halyard stretch consumed: (300/540)x100 = 55


This suggests that you could happily go with a 2:1 halyard using 1/4" amsteel and have 20% less stretch - ((44-35)/44)x100 = 20% - than you have with 5/16" on a 1:1, and you are still well within the 10% stretch limit and load factors for the halyard. The weight savings is 11 ounces at the middle of the mast (need to work out if there is any advantage given the additional weight of a block or a smooth shackle at the masthead). The 2:1 halyard will have the knock-on effect of a) making the sail easier to hoist, and B ) reducing compression in the spar.

The 3/16" amsteel on a 2:1 is easily strong enough, but the stretch is increasing at that point. It would be an interesting experiment to see if it is noticeable - at some point the mainsail fabric becomes important and perhaps the sail stretches more than the halyard; if so, a fancy halyard is not going to help leach control as the sail cloth stretch becomes the dominant factor.

To match a 2:1 1/4" amsteel halyard, it would take 1:1 3/8" amsteel - and that 3/8" line is more expensive and heavier than 1/4".

At least that's my take on it.

- beetle



One thing you forgot in your calculations is that due to the 2:1 halyard the main will only move 1/2 of your halyard stretch so you can cut the numbers for your 2:1 calculations in half - an even stronger argument for using a 2:1 halyard

#30 barefoot children

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Posted 23 July 2007 - 04:43 PM

Big Pimpin'

Block Head
You can now replace that gigantic web block at your headboard for your 2:1 halyard system with a block hardly bigger than your standard halyard shackle. Antal Hardware has created a 2:1 halyard block that is CNC cut out of a solid piece of 17-4ph Stainless steel. The result is a tiny block with extremely high working loads. The version used by the Farr 40 class is only about 2 inches long with a 26 mm sheave, has a 3000lb working load, and weighs 3 oz. Less weight aloft. It's a good thing. get in touch with Euro Marine Trading for more info.

Have any of you anarchists used these?

05/02/07


Wow are these things slick, but I'd need to refinance my house to buy one. Scrounged thru my junk box and put this together. Oh yea, I had to drill the center hole larger on the sheave.

Attached File  DSC02334.JPG   55.75K   26 downloads

#31 spencerogden

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Posted 23 July 2007 - 09:16 PM

Good solution, just beware of the spinning sheave unscrewing the pin...

#32 Marshy

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Posted 04 November 2008 - 10:19 PM

Tried that on the Trimaran, Not ideal as the shackle spun sideways and halyard jumped the sheave!!

#33 Rail Meat

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Posted 04 November 2008 - 10:28 PM

Tried that on the Trimaran, Not ideal as the shackle spun sideways and halyard jumped the sheave!!


Hmmm.. Using it on the Class 40 and have not had any issues like that. The only problem I had was that the post is not captive, so it is possible to lose it. Otherwise, it has been a great solution

#34 extrad

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Posted 04 November 2008 - 11:33 PM

1:1 halyard, 5/16" amsteel (10% strech @ 1,370 pounds)
leach load = 600 pounds
halyard load = leach load = 600 pounds
% of line breaking strength = (600/13700)x100 = 4
halyard stretch over 40' = 0.46x40x12/100= 2.2 inches
weight of halyard 40'x2.7/100 = 1.08 pounds
% of halyard stretch consumed: (600/1,370)x100 = 44

1:1 halyard, 3/8" amsteel (10% stretch at 1960 pounds)
leach load = 600 pounds
max halyard load = leach load = 600 pounds
% of line breaking strength = (600/19600)x100 = 3
halyard stretch over 40' = 0.46x40x 12/100= 2.2 inches
weight of halyard 40'x3.6/100 = 1.44 pounds
% of halyard stretch consumed: (600/1960)x100 = 30


Beetle

there's something wrong with your numbers in the comparison of 5/16 to 3/8 at 1:1.

Subject to the same load the 3/8" should stretch less than the 5/16" due to it's greater crosssectional area. Don't have time to do the math right now.




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