New Furler rig tension - SailNet Community
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post #1 of 16 Old 05-05-2011 Thread Starter
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New Furler rig tension

I just got a CDI flexible furler over the winter for my S2 7.3. I sailed the boat today for the first time and noticed that the forestay with the sail furled (full and partially) was flopping all over the place and looked very loose. The sailmaker that put my furler together told me that they set the forestay length and I need not worry about it. They said to adjust tension with the backstay, I thought I had. After the sail I tightened up the backstay quite a bit more and it seems to have tightened up the forestay as well but I wont know for sure until the next time I sail.
I read through the sticky thread about adjusting rig tension but it seems far to technical for what I need. I don't have a tension gauge and am not looking to race. I just want to know that I am adjusted to safely sail without the risk of something coming apart for right now. What should I look for as far as feel goes to know if my standing rigging is set properly? Is there a guideline for how much play there should be in the backstay?

Thanks and sorry for being so long winded....
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post #2 of 16 Old 05-06-2011
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The new CDI should have a turnbuckle inside the drum. Presumably, the installer set the turnbuckle to achieve the same length as your original headstay, but really, only they would know that for sure.
It's obviously a lot easier to adjust the backstay turnbuckle than take the drum of the furler apart to access the headstay turnbuckle, but since new wire will stretch, you will probably have to at some point.
If your backstay turnbuckle is currently turned down more than it used to be,(you can sometimes tell by the discoloration on the threads), then the headstay is longer because it was not set right or it has already stretched. So you should go ahead and tighten up the forestay.
The best way to go about this is to loosen the backstay and hold the mast forward with the old jib halyard and then pull the clevis pin at the bottom of the headstay. Then you can work on the foredeck so as to lessen the possibility of dropping one of those pesky little screws or nuts overboard as you disassemble the drum.
Tighten the turnbuckle up enough so that your backstay turnbuckle will be a little more open than it was before you had the furler installed. That is if you were happy with the way it was tuned before. That way, as the wire stretches, you will only have to adjust the backstay.
The way I determine tension on the headstay is by feeling the backstay. You want it almost as tight as the upper shrouds, but not quite.

If you didn't have a furling system previously, it will seem a little floppy because of the extra weight of the sail and the extrusion but you shouldn't have a whole lot of deflection when sailing in light to moderate conditions.

Hope that helps.
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post #3 of 16 Old 05-06-2011
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Jet, adjusting the Headstay inside the CDI is very easy. Just release the pin that holds the drum down, and slide the drum up until you can see the turnbuckle, adjust as needed, then realease the drum drown, and reinsert the pin.
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post #4 of 16 Old 05-06-2011 Thread Starter
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They told me that they did set the length to what the headstay was before. The old forestay did not need replacing so I don't think it will stretch much. Maybe the flopping was normal with the furler, the boat sailed ok. My main concern is that I tightened the backstay too much and could cause damage.
As far as adjusting the forestay turnbuckle, can I raise the drum up over the foil? Can I do it with the sail up or do I need to take it down? I'm thinking the sail has to come off but it should slid up over the foil.
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post #5 of 16 Old 05-06-2011
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the forestay length is set to adjust the mast fore or aft rake which will effect the way the boat sails to weather. you can adjust it to get more or less weather helm and depends on the wind pressure you are sailing in. the back stay is set to adjust out the curve in the forestay as the wind pressure increases. on a cruising boat they set the tension mostly for a strong blow so you do not get to much curve in the forstay. on most 30 foot boats the curve should be about 3" of deflection at the middle of the forestay in 15KTS of wind

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post #6 of 16 Old 05-06-2011
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Overboard is dead on ... the 3" sag at 15kts will equate to the shape already cut into the luff of the typical 'cruising' sail. ..... 15+% tension on the backstay.

if you want more 'precision' here's how to do it (no tension gage needed):
http://i1086.photobucket.com/albums/...LuffHollow.gif
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post #7 of 16 Old 05-06-2011 Thread Starter
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This is all great information, thanks. I understand what you guys are saying about luff hollow and forestay sag. What I'm a little unsure of though is how to go about setting the backstay so I keep the desired forestay sag for the luff hollow.
After reading Rich's page I'm certain now that the backstay was was too loose when I sailed yesterday, the boat wouldn't point and heal was excessive for the wind and the amount of sail I had up. I have since tightened the backstay but how do I know if it is now too tight (my concern) or still too loose. It is very hard for me to judge sag in the forestay just by looking at it with the sail furled. Too loose seems like no big deal especially after yesterday, I can just tighten it more. Too tight is my concern, is it possibly to tighten it so much that it could break under a wind load?
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post #8 of 16 Old 05-06-2011
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Simple way is to assume ~3" of luff hollow into the sail. Then when on a hard beat and with 'normal' jib sheet tension, go forward to the bow, and with your eyeball looking perpendicular from the boats centerline at the luff hollow shape, make your backstay adjustments so that you only have ~3" or so of forestay sag (while looking at the sail from the centerline @ ~90 deg.). Once you get this 'close' then go back to the cockpit and memorize the shape of the foil and luff as viewed from that perspective.
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post #9 of 16 Old 05-06-2011
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jetdrvr,
One of the nice things about the CDI is that it does not use your jib halyard. If yours is still up, you can attach it to the stemhead fitting and pull it up tight to give you a visual refernce to the straight line mast heat to stem head. Then you can go out sailing and adjust the back stay until you achieve the recommended sag. Have someone go along with you to man the helm while you take your time to make the adjustments.
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post #10 of 16 Old 05-07-2011
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A Loos gauge is about $120.
Not a lot for peace of mind!
sam :-)

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