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Diamond Wire Tension
http://www.hobie.com/forums/viewtopic.php?f=13&t=4652		 Page 1 of 2
Author:  ncmbm [ Tue Aug 22, 2006 7:18 pm ]
Post subject:  Diamond Wire Tension
I'm seeking advice on diamond tension. Have used the measurement system in the performance manual in the past but the new sail needs more I think. Had the wires set at a tension that allowed the wires to almost touch the mast at 18". The luff of the main was backwinding going to weather. I run a Tiger main. My downhaul was released when I first noticed this but the condition persisted even with downhaul tension hard. I assume the mast was bending too much causing the luff to be too full. I broke both turnbuckles and have new wires on now. I used a Loos gauge and set them at 28 or 390lbs. Do you think thats enough? I think the Tiger tension is around 600lbs but they are prebending the mast. I don't think the spreader system of the 18 is designed for that much tension. I was told the I-20 runs 800lbs in the wire, so I don't know how much is too much?
Author:  mmiller [ Wed Aug 23, 2006 9:27 am ]
Post subject:  Tensions
You are treading in unknown waters here. The Tiger mains / mast require a lot of diamond tension for the mast prebend. Years ago I recall the Aussie guys using prebend in the standard 18 mast though, so I suppose the rig was handling it. Just not sure how much you can prebend the 18 mast section.
Author:  ncmbm [ Wed Aug 23, 2006 2:42 pm ]
Post subject: 
Matt, is it a correct assumption that the backwinding luff is due to mast bend? I will have it out this weekend for more testing and guess I will know then. My wires were looser than I would have liked on the first test. I will post findings next week.
Author:  John Eaton [ Thu Aug 24, 2006 6:22 am ]
Post subject: 
Is not the wires almost touching the mast at 12" the highest setting? (If you're at 18" now, I think you can squeak on a little more)

How much actual difference is there between the 18 and Tiger luff curve? Did you roll them out in the yard to compare?

How does changing the rotation affect the "backwinding"?

Are you needing to depower that much? How about 12 or 16:1 downhaul?
Author:  mmiller [ Thu Aug 24, 2006 11:54 am ]
Post subject:  Backwind
Backwinding is an issue with the main sail shape and the slot between it and the jib. You can try adjusting the jib sheeting too. Perhaps the jib will need to be sheeted differently. The car position may have to be moved.
Author:  Agilefalcon [ Sun Nov 05, 2006 2:40 pm ]
Post subject:  What tension using the Loos PT-1 Tensiometer
Hi all:
What should I set the diamond wire tension to using the Loos PT-1 tensiometer? (www.loosnaples.com).

I bought the gauge from Murrays and have found it to be excellent for at least making sure the tension in both wires is identical; however, I don't know what that should be.

I set it at about 100 pounds in each wire. Should it be more or less?

thanks for the help.

Chris.
Author:  ncmbm [ Mon Nov 06, 2006 7:27 am ]
Post subject: 
Chris, I'm running 400lbs on my wires. I also use a loos guage. If you are on a standard 18 use Phil Bermans guide and get the loos reading from his recommendations or post on Catsailor for response.
Author:  Dan DeLave [ Mon Nov 06, 2006 10:39 am ]
Post subject: 
The Tiger mast as a common set up will be spreader rake 1 3/4 inches and mast prebent at 1 3/4 inches. Mast prebend means with the mast on its side, so the bend is not effected, draw a string tight from the top to the bottom at the track, take a measurement in the middle from the track to the string.

To get it this tight we are running about 800lbs on the diamond wire. That is somewhere near 47 on the older, non wheel, loos guage. It does not register on the newer guage. There are some that are over 1000 on the diamond wire tension. I do not know what your mast is capable of. You could try to run the spreaders raked back further to be able to bend the mast 1 3/4 inches without that much wire tension. This may be the safer way to go.

Later,
Dan
Author:  JACK FLASH [ Thu Nov 16, 2006 8:19 am ]
Post subject:  Diamond Wire Tensions
I run a large main similar to the Tiger STX and my wire tensions are set to 25 on the new style LOOS gauge. I use to run them loser but my silver medalist Tornado sailor sail maker Charlie Ogletree bumped them up quite a bit, I have to say it sails better his way. I just hope the rig doesn't break.
Author:  ncmbm [ Thu Nov 16, 2006 1:03 pm ]
Post subject: 
I wouldn't worry about the aluminum section. I'm concerned about the sideload from the squaretop breaking the comptip. Or the spin breaking the tip. An SX came with the diamond compression kit as I remember, if not then get one. Is your main cut to optimize the tip? Or are you using a solid mast?
Author:  JACK FLASH [ Thu Nov 16, 2006 1:50 pm ]
Post subject:  Mast
No we have a comptip mast. The SX did not come out until after Hobie lost that fatefull lawsuit (don't get me started on that one). I have considered going to a solid mast but cost is a limiting factor. Hopefully it won't break, but if it does we are insured and might just sink the boat.
Author:  Dlennard [ Fri Nov 17, 2006 8:07 am ]
Post subject: 
You have to fit the mast to the sail. Turn the boat over on its side and hook the main on top and then hook up downhaul and boom and main sheets. Just like you would use it to sail just do not put in the sail track. Use normal downhaul and sheet tenision and mast rotation. Set your mast to fit the curve of the sail as best you can. This will be the setting that you want to use all the time.
Author:  John Eaton [ Fri Nov 17, 2006 8:36 am ]
Post subject: 
Dlennard wrote:
Set your mast to fit the curve of the sail as best you can. This will be the setting that you want to use all the time.


Coming from the 16 to the 18 briefly in '05 and the 20 this season and not knowing diddly about mast setup, and sailing with an old fuller cut main, and seeing guys cranking on or off diamond tension when the wind changes??? And thinking why?:shock: There are plenty of other variables.

David, Thank you very much!!! This makes all the sense in the world to me, I thought I was not seeing some "magic" somewhere.

There's more than one way to skin a cat and some methods waste the meat. :wink:
Author:  ncmbm [ Fri Nov 17, 2006 9:14 am ]
Post subject: 
Thanks David, thats so simple. Is there any way other than downhaul to effect the shape of the comptip? Have found it best to limit rotation and keep the tip flexing on the wider axis. How do you determine sheet angles for jib and spin, any tricks?
Author:  JACK FLASH [ Fri Nov 17, 2006 9:37 am ]
Post subject:  Sheeting Angles
Our sailmaker and Olympic Tornado sailor says the general location for the fair leads is 7-8 degrees off of the forstay. As for the angle of the line to the fair lead you are generally looking to bisect the angle, how ever some sail are cut with a different angle in mind. The Tiger jib for example is designed to be pulled downward more than aft. The stock SX jib is designed to be pulled more aft then down. As for the spinaker my thought is the further back on the boat the better. We run our turning block about a foot behind the aft edge of the dagger board well. We do this for two reasons. If it the sheets runn to the back corner it might interfere with the tiller, and the spin sheets may get in the way when going out on the wire. When going downwind my crew and I are against the rear crossbar with one of us usually on the wire and the lines don't seem to get in the way where they are.
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