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Old 05-28-2009, 03:21 AM   #1
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Apologies if this has been discussed before, but a search did not pull up anything....

Is anyone aware of a formula or other guidance to determine what halyard breaking strength is required ? My main is old & stretchy, and was wondering if you could calculate the recommended breaking strength by using the displacement, P and E lengths.... is that too simple ?

Boat is a Tartan 3000 that we do beer cans in, and primarily weekend/weeklong cruises. Displaces ~3800 with a P (luff) of 34' 3" and an E (foot) of 11 ' 6".

Any brand recommendations are appreciated. The front-runners in my research are 3/8" Samson XLS Xtra (4600 pounds) and New England Ropes Sta-Set X (5500 pounds).

Thanks in advance !
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Old 05-28-2009, 06:23 AM   #2
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Hello Irie,

Check the Load : Extension ratio on this D2/classic line -- Check if the 7/16th halyard will fit your sheeve.

Here is the 2 page .pdf with details D2.pdf

I guess the other factors besides luff & foot lengths, that must come into play are wind strength/point of sail, main sheeting angle and loading, vang (kicker) tension and the others like righting moment relative to keel weight etcc....

Richard
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Old 05-28-2009, 02:52 PM   #3
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Thank you for the quick reply Richard. Agree with your assertion of additional inputs when establishing breaking strength requirements. At this stage, my only feedback was from an electronics guru who stated that a 10+ yr old 1/2 inch halyard can be replaced by a 3/8 or 7/16 due to the newer technologies.

Surprised my initial google searches did not reveal any Marlow dealers in the US. The hunt continues....

Thanks again
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Old 05-28-2009, 10:41 PM   #4
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Irie

Found this Bookmark in my data bank Website

Hope they can assist.

Richard
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Old 01-17-2010, 08:30 PM   #5
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Quote:
Originally Posted by Irie View Post
Apologies if this has been discussed before, but a search did not pull up anything....

Is anyone aware of a formula or other guidance to determine what halyard breaking strength is required ? My main is old & stretchy, and was wondering if you could calculate the recommended breaking strength by using the displacement, P and E lengths.... is that too simple ?

Boat is a Tartan 3000 that we do beer cans in, and primarily weekend/weeklong cruises. Displaces ~3800 with a P (luff) of 34' 3" and an E (foot) of 11 ' 6".

Any brand recommendations are appreciated. The front-runners in my research are 3/8" Samson XLS Xtra (4600 pounds) and New England Ropes Sta-Set X (5500 pounds).

Thanks in advance !
Check out the http://www.westmarine.com/webapp/wcs/store...ging-Fibers.htm. The chart is quite revealing that breaking strength is not the issue, but how much stretch you are willing to endure as the loads increase with the increase in wind. Having a stretchy sail in addition to a halyard that allows the head to move down moves your draft aft (baggy) and increases your heeling moment just as you want to move the draft forward and flatten the sails to keep her on her feet and moving well to weather.

Wire is the best (least stretch) followed by the V-12, T-900, dynema, etc. as shown on the chart.

We use, due to 94' mast, wire for our genoa, right on to the winch drum for the least possible stretch, and vectran for the main, spin, and control lines. The new materials allow generally a size or two smaller than what you are using now, and performance, particularly to weather, will be dramatically better.

Our J27 with nearly the same specs as your tartan, we use 1/4 main and 3/16" jib and spin vectran halyards, which are stripped for weight aloft, and only have the outer layer on for the winch and jammers. We have even gone to a 1/8" dynema backstay, which is stronger than the wire it replaced, and saved 12 pounds aloft, a huge reduction!

Take the high tech halyards off if you strip the cover, leaving 1/8" placeholders up when you are not actively using the boat. If not, the high tech line is 80% of its initial strength after 2 years continuous use, and does not degrade appreciably after that as the cover takes the UV.

best of luck, and enjoy the better performance!
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Old 01-18-2010, 07:36 AM   #6
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Harken has your boat in its compuspec load calculator - you can get a loading print out at http://www.harkencompuspec.com/cgi-bin/cs303.exe

It says your end boom load will be 1448lbs, and generally the halyard load is about the same.

The question for you is how much stretch are you willing to have at that load? That's a cost vs performance trade-off (less stretch = higher performance but higher cost).

Generally a dacron double braid will stretch about 2.4% at 15% of breaking strength. 2.4% stretch on 35' = 10" stretch. 1448lbs = 15% of a 9653 breaking strength line = 1/2" Dia. White Sta-Set Braid, 8,500lb. SAmson XLS is also generally in this same ball park.

Generally a spectra cored double braid will stretch about 1.0% at 30% of breaking strength. 1% stretch on 35' = 4". 1448lbs = 30% of a 4826 breaking strength line = 6mm Endura Braid, 4400lb. Breaking Strength (but 6mm is pretty hard on the hands, so you would probably want 8mm to be easier to handle).

Stay-set X is a special NER parallel core construction with 1.6% at 15% of breaking strength. 1.6% stretch = 7" stretch on a 1/2" stay-set X.
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Old 01-18-2010, 09:18 AM   #7
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Wonder if Dynex Dux could replace wire halyard

http://www.strongrope.com/dynex.htm
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Old 01-18-2010, 11:02 AM   #8
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Quote:
Originally Posted by MMNETSEA View Post
Wonder if Dynex Dux could replace wire
It's all just a matter of sizing:

7mm dux about equal to 1/4 1x19 wire in stretch (.00134in/in/1000lbs)

9mm dux about equal to 5/16 wire (.00084in/in/1000lbs)

11mm dux about equal to 3/8" wire (.00055in/in/1000lbs)

(according in independent testing by G. Ashmore. Thanks Glenn)

Halyards would probably be 7x19 wire which would stretch a bit more than 1x19 but I can't find any data on it. But I am sure it is enough that you could take the dux down one size from the above - which would make it pretty much equal to the wire size.
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