My 5.7 will kept with the mast stepped all summer. How tight should the shrouds/forestay be? The manual only references "allowing the mast to rotate freely". How much slacl/flopping around of the lee shroud is too much? If I do them up tighter, should they be slacked off after a days sail, or is it OK to leave them like that til October?
Question two, diamond wires. The manual says to be able to press them against the mast, between 12" & 20" up, & if you don't want to adjust them each day, just leave them in the "medium" position. When putting this theory into practice it became apparent that 12" is a variable target. It depends on how hard you press. I thought they were too loose, & did up the turnbuckles a couple of full turns. I could still press them against the mast at 12", but I had to put my arm into it, so I loosened them off a bit. I don't have one of those fancy tension gauges, what do experienced people do? Push just using a thumb, to the point where your thumb is starting to get a good bend, or to the point where you have to get your arm behind the thumb? Does anyone have any cross references that equate to "X" amount of tension. Could I place a block of wood on a scale, then press the wood against the wire, & with the scale reading "X" pounds, that would equate to "X" amount of wire tension?
I am not experienced enough to really appreciate the gains of very fine tuning, but would like to establish a baseline of what light/medium/strong tension feels like. I don't want to put unnecessary strain on the rig, or worse have it come down because things were set to loose.
The manual states that diamond wires are the most critical tuning adjustment, so I would like some knowledge here, as it seems to be a valuable depowering option.
Thanks.
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How tight should diamond wires & shrouds be?
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Posted: Jun 23, 2010 - 02:07 PM
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Posted: Oct 05, 2021 - 09:58 PM
I have the same question.
I understand the rake and how to measure it, but how tense should the diamond wires be.
I can move the spreaders up and down a little with my hand. Is this OK? or should the tension be tight to the point of not being able to move the spreaders up and down by hand? -
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Posted: Oct 06, 2021 - 06:12 AM
You should not be able to move them. Think about the forces- if the wires move so that the spreaders are not perpendicular, you have no support for the mast. If they move up or down any appreciable amount, you risk them being “pushed” out of place. If that happens they no longer make a truss, & you risk mast failure. The instructions in the Nacra manual about a few wraps of wire are garbage. Use a roll of tape, & “figure 8” around each end so that it protects the jib, & locks the Diamond wires in place.
Tension has no bearing on whether you can move the spreaders. Proper figure 8 taping will lock them in place, even with totally slack wires.
As to my question of a decade ago...as a beginner, don’t overthink it. Tighten them equally, as instructed, by standing in front of the mast & not driving the wires through your thumbs. The manual states, (and is correct), in that D wire tuning is important, but for a beginner, just make them “medium” & go sailing.
I bought a Loos gauge shortly after that post & use it each spring when we raise the masts. I can’t recall what setting we use, it’s written down on the flap of the box the gauge came in, & we set it to that each spring.
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Posted: Oct 06, 2021 - 12:25 PM
You really dont have to be a very experienced sailor to be able to tell the difference of a turn on a diamondwire turnbuckle. Sometimes just a half a turn can "wake up" a boat.
But you do need the right tools so you can make more informed adjustments and re-create good results. Here is what I use:
https://www.amazon.com/Lo…Gauge-Inch/dp/B007CNC06U
I dont guage the diamonds every time I sail but I do have light, med and heavy air tensions that I have developed over several years of trial and error. The higher performance your boat is the more important correct diamond tension becomes. -
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Posted: Oct 06, 2021 - 02:44 PM
So using this tool, what are your light, med and heavy air readings? Asking to understand the tension range.
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G-Cat 5.7
Sarasota
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Posted: Oct 06, 2021 - 03:01 PM
This is always the magical answer among racers. I recall racing the Tornadoes in the 90s, we adjusted the diamonds constantly. This really comes down to what shape do you want in the sail... I raced my 5.8 with the "soft rig" concept and the Tornado with the hard rig. The diamond tension and spreader sweep will really depend on how the sail is cut. With the boomless rig, your mast rotation is somewhat at the mercy of the main. I think the best thing to do is set the boat up on the beach. Raise the main and angle the boat where you would be hard on the wind. Sheet the main in and lay on the trampoline looking up the main about 25% aft of the mast. I have done testing sessions where we would run a camera looking up at this point and then evaluating the shape on a computer. Obviously, adjusting the diamond tension with each picture. This will take a while, but you will have a ton of data to evaluate and see what is best for your type of sailing.
Be careful in duplicating tension numbers because the shape will vary from the spreader sweep, the sail condition and (surprisingly) the mast. Not all masts bend and react the same. A buddy and I both had 5.8s and we would mix/swap gear for big events. (Mainly taking spare parts) We realized the mains and jibs were cut differently, the masts bent differently, and we had 3 sets of dagger boards; each had a different cord width. I think you can get close with duplicating tension numbers, but for top end racing, you will need to develop your own numbers. Also, a big factor will be your crew weight (and boat weight). I think the power of your downhaul will also have a huge factor.
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Scott
Prindle Fleet 2
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Posted: Oct 06, 2021 - 05:41 PM
Great points. I am fortunate to have access to 3 other boats exactly like mine and my diamond tension settings just dont work on my friends boats. However they are close enough for a starting point. -
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Posted: Oct 06, 2021 - 06:09 PM
The simple answer is about 7% of breaking strength for light air, 9% for med air and 13% for heavy air.
I have seen it suggested (Ron Whites book maybe?) to start diamond tension at around 10% of breaking strength and adjust up or down accordingly.
On my rig one full diamond wire turnbuckle turn is equal to about 2% of breaking strength measured on the loos gauge. So for light air I loosen the turnbuckle a full turn on each side and for heavy air I tighten both turnbuckles 2 turns from Med setting. I keep it in Med setting most of the time.
Hope this helps...
Edited by bradinjax on Oct 07, 2021 - 11:09 AM. -
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Posted: Oct 06, 2021 - 11:02 PM
Do you have any pictures of this? -
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Posted: Oct 07, 2021 - 06:58 AM
It does very much! Thanks for this.
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G-Cat 5.7
Sarasota
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Posted: Oct 07, 2021 - 10:00 AM
For the record because apparently no one on here that owns a loos gauge has ever used it on a soft diamond rig:
If you can touch your diamonds to the mast 6”, 12”, 36”…. It doesn’t matter, they are all “0” on the gauge. You have no tension.
The reason the “touching the wires to the mast” scale is used is because you are measuring slack… it doesn’t really matter how hard you press. Just be consistent so you have a reference for yourself. You can always just make a piece of bungee that’s tied around the mast that you slip up on the diamonds when you want to measure too.
I’d just go get a few books about beach cats to get some basic knowledge of sail shape and tuning. If you don’t ever adjust your mast rotation or downhaul then changing your diamonds alone is only half the story of creating the ideal sail shape for the conditions. -
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Posted: Oct 07, 2021 - 11:01 AM
I have never seen a "soft diamond" rig but after a quick google search I get the idea. Still not sure about the advantages of loose diamond wires but thats another discussion...
Loos gauge is useless with this type of diamond wire rigging. But I am a big believer in measurable and repeatable results so maybe a kitchen spring scale you push against a diamond wire until it touches the mast so you can make an accurate measurement? The actual numbers are not important as long as you do it the same way each time. You are really just establishing a baseline then loosening or tightening turnbuckles as required for conditions.
Edited by bradinjax on Oct 07, 2021 - 11:02 AM. -
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Posted: Oct 13, 2021 - 03:45 PM
If you go for a tension gauge, make sure you are buying the correct one for the wire size you have. Typically diamond wires are 5/32". The PT-2 Loos gauge is for 3/16" - 1/4". You will need to use the Model A gauge. Luckily/unluckily I have 4 or 5 different gauges from being in the industry. The 18-2 diamonds are at 300# and the Tornado is at 800#. I do not adjust either one for the racing around here. Remember, the diamond tension and spreader sweep are dependent on what sail you have, crew weight, and your style of sailing. I would suggest to get a starting point and record it. Go sailing. Make notes and adjustments on what you want the boat to do. Build your own data set.
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Scott
Prindle Fleet 2
TCDYC
Prindle 18-2 Mod "FrankenKitty"
Tornado Classic "Fast Furniture"
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