[Rhodes22-list] shroud tension jokes

Toad the Wet Sprocket rhodes22-list@rhodes22.org
Wed, 21 Aug 2002 15:09:39 -0400


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<P>Thanks Roger,</P>
<P>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; I did say I was joking didn't I?&nbsp; :-)<BR><BR></P></DIV>
<DIV></DIV><BR><BR><BR>Please respond to sprocket80@hotmail.com 
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<DIV></DIV>From: "Roger Pihlaja" <CEN09402@CENTURYTEL.NET>
<DIV></DIV>Reply-To: rhodes22-list@rhodes22.org 
<DIV></DIV>To: <RHODES22-LIST@RHODES22.ORG>
<DIV></DIV>Subject: Re: [Rhodes22-list] shroud tension jokes 
<DIV></DIV>Date: Wed, 21 Aug 2002 11:07:16 -0400 
<DIV></DIV>
<DIV></DIV>Dear Toad, 
<DIV></DIV>
<DIV></DIV>First of all, I'm an engineer &amp; I've owned my Rhodes 22 since the spring of 1987. Stan @ GBI will never be this specific with rig tuning specs. It's just not his nature. Early on, I purchased a Loo's tension gage, started doing experiments, making measurements, &amp; racing my boat. The specs I gave you are the lowest static tension settings that yield the desired dynamic behavior in the sailing rig. By the way, totalling up the lbs of tension in the standing rigging doesn't tell you very much. Each stay is loaded individually. The ultimate tensile strength of those 5/32" OD, 1 X 19, 316 stainless steel wires is on the order of 2800 lbs. At 600 lbs max tension on the loaded windward upper sidestay, my suggested rig tension settings leave a safety factor of more than 4X. 
<DIV></DIV>
<DIV></DIV>The only part of the standing wire rigging I've upgraded was my forestay wire to 3/16" OD, which has an ultimate tensile strength of about 4000 lbs. I did this wire size upgrade when I replaced my OEM standard roller furler to a Harken Unit 0. 3/16" OD wire in the forestay is probably overkill. But, 3/16" OD was the largest standard size available for the Harken Unit 0. I had to replace the forestay anyway as part of the installation, there was no good reason not to upgrade, &amp; it seemed like cheap insurance. 
<DIV></DIV>
<DIV></DIV>The breaking strength of the wires &amp; the swaged terminals are the limiting factors. The chainplates can hold much more than the rest of the rig. You could confidently lift the entire boat suspended from the upper side chainplates. They don't need to be upgraded. 
<DIV></DIV>
<DIV></DIV>The mast compression post is only loaded to a small fraction of its buckling strength. Don't worry about it. 
<DIV></DIV>
<DIV></DIV>Look on page 970 of the WEST Marine 2002 Master catalog for a Loo's tension gage. You would need to order a Loo's model 91A or PT1. 
<DIV></DIV>
<DIV></DIV>As I said in my post, I was trying to use the image of the ends of the hull bending upward like a "22 foot long banana" under rig stress as a "greatly exagerated" illustration of the effects involved. The real hull deflection is subtle, certainly not observable without precision measurement instruments. 
<DIV></DIV>
<DIV></DIV>Since I suggested adjusting the length of the forestay in 1/2" increments to adjust your weather helm/lee helm balance, if you measure the forestay length to 1/4 of that increment, or 1/8" accuracy, that will be sufficient resolution. You are quite correct, I had too many significant figures in my forestay length spec. It should have read 333-5/8". 
<DIV></DIV>
<DIV></DIV>Criticize me if you wish, but did anyone else give you anything but qualitative descriptions of rig tuning? Why don't you try my rig tuning procedure &amp; see what you think? 
<DIV></DIV>
<DIV></DIV>Roger Pihlaja 
<DIV></DIV>S/V Dynamic Equilibrium 
<DIV></DIV>----- Original Message ----- 
<DIV></DIV>From: Toad the Wet Sprocket 
<DIV></DIV>To: rhodes22-list@rhodes22.org 
<DIV></DIV>Sent: Tuesday, August 20, 2002 3:30 PM 
<DIV></DIV>Subject: Re: [Rhodes22-list] shroud tension jokes 
<DIV></DIV>
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<DIV></DIV>Roger, 
<DIV></DIV>
<DIV></DIV>So you have a total of 1800lbs of tension on all of your shrouds, not to mention the fore/backstay tension? Where did you come up with all of these figures? Are these the specs from Stan and the guys at GB? This all seems like quite a strain on the chain plates and alot of compression down through the mast into the hull. 
<DIV></DIV>
<DIV></DIV>Did you replace your rigging with larger cables or beef up the chain plate mountings? 
<DIV></DIV>
<DIV></DIV>Where can one buy the guage you have and a tape measure that measures to three decimal places? Is my boat supposed to bend up at the ends like a 22 foot banana too? 
<DIV></DIV>
<DIV></DIV>Sorry, I couldn't resist. I was in a goofy mood today. Honestly, where did you get these specs? 
<DIV></DIV>
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<DIV></DIV>Please respond to sprocket80@hotmail.com 
<DIV></DIV>
<DIV></DIV>From: "Roger Pihlaja" 
<DIV></DIV>Reply-To: rhodes22-list@rhodes22.org 
<DIV></DIV>To: 
<DIV></DIV>Subject: Re: [Rhodes22-list] shroud tension 
<DIV></DIV>Date: Tue, 20 Aug 2002 07:56:38 -0400 
<DIV></DIV>Jack, 
<DIV></DIV>Here's a copy of the rig tuning procedure I use: 
<DIV></DIV>The 1st thing you want to do is measure the length of the forestay on center 
<DIV></DIV>from pin-to-pin. On my 1976, standard mainsail, Rhodes 22, this measurement 
<DIV></DIV>is 333.625 inches. Write this number down because it is very important. 
<DIV></DIV>If your forestay length is more than a couple of inches different than this, 
<DIV></DIV>you might want to reset it 333.625 inches as a reasonable starting point. 
<DIV></DIV>Now step the mast. Take the excess slack out of the forestay &amp; backstays 
<DIV></DIV>with the backstay adjuster. You don't want things real tight at this point. 
<DIV></DIV>All upper &amp; lower sidestays should be slack. Go to the base of the mast, 
<DIV></DIV>pull a halyard taut along the mast &amp; sight up the mast from the rear &amp; from 
<DIV></DIV>the side. Any deviation from a straight mast will show up as a gap between 
<DIV></DIV>the mast &amp; the halyard. There should be no observable bend or bowing in the 
<DIV></DIV>mast. If there is, the mast may have been dropped &amp; bent at some point or 
<DIV></DIV>may have some other problem. You should call Stan at GBI &amp; he will be able 
<DIV></DIV>to help you work out your problem. 
<DIV></DIV>I like to use a Loo's tension gage. The model 91 is the appropriate range 
<DIV></DIV>for the Rhodes 22. Remember to always measure the tension at the same 
<DIV></DIV>relative position on each shroud every time. On Dynamic Equilibrium, I 
<DIV></DIV>have marked these measurement points with little spots of paint on the 
<DIV></DIV>wire right at my eye level. 
<DIV></DIV>The upper sidestays are adjusted next. Raise a tape measure up the mast on 
<DIV></DIV>a halyard. Measure to the same point on each side of the boat. I like to 
<DIV></DIV>use the edge of the toerail right next to the sidestay. Tighten the 
<DIV></DIV>turnbuckles a little at a time on each side to adjust the upper sidestays 
<DIV></DIV>until both sides are the same length +/- 1/4" &amp; tensioned to approximately 
<DIV></DIV>300 lbs +/- 5%. This procedure assures the top of the mast is centered in 
<DIV></DIV>the boat &amp; the upper sidestays are tensioned equally port &amp; starboard. 
<DIV></DIV>What you do next depends upon whether your boat has the IMF mainsail or a 
<DIV></DIV>conventional mainsail. 
<DIV></DIV>On an IMF mainsail boat, I would adjust the 4 lower sidestays so they were 
<DIV></DIV>all approximately the same tension. I would start with approximately 200 
<DIV></DIV>lbs +/- 5% on all 4 lowers. This is not a lot of shroud tension. Check for 
<DIV></DIV>mast straightness with the halyard again. You want the mast to be straight 
<DIV></DIV>in order for the IMF furling mechanism inside of it to be able to turn 
<DIV></DIV>without binding &amp;/or excessive wear on the bearings. Minor bending or 
<DIV></DIV>bowing can be taken out with the lower sidestays. However, I would call 
<DIV></DIV>Stan at GBI if I couldn't get the mast to straighten out with a difference 
<DIV></DIV>of about +/- 15% on lower sidestay tension. 
<DIV></DIV>My Rhodes 22 has a conventional mainsail. I have a very roachy fully 
<DIV></DIV>battened mainsail which has been cut to respond to mast bend. I have my 
<DIV></DIV>backstay adjuster set-up to adjust quickly from the cockpit with calibration 
<DIV></DIV>marks on the line. 
<DIV></DIV>Tighten the turnbuckles equally &amp; a little a time on each side to keep 
<DIV></DIV>things reasonably centered. I adjust the forward lower sidestays to 400 lbs 
<DIV></DIV>+/- 5% of tension, and the aft lower sidestays to 200 lbs +/- 5% of tension. 
<DIV></DIV>Then, check for mast straightness with the halyard. Believe it or not, the 
<DIV></DIV>standard mast on the Rhodes 22 is such a stiff telephone pole that, at 200 
<DIV></DIV>lbs differential tension on the lowers, there will be a barely detectable 
<DIV></DIV>fore/aft bend in the mast with no sails set &amp; the backstay adjuster slack. 
<DIV></DIV>At 400 lbs of tension on the lower forward sidestays, when the backstay 
<DIV></DIV>adjuster is tensioned, primarily only the upper half of the mast is pulled 
<DIV></DIV>towards the stern. The forestay is tightened &amp; the mast is bent at the same 
<DIV></DIV>time. Both actions are exactly what you want to obtain proper sail shape in 
<DIV></DIV>a high wind situation. 
<DIV></DIV>Now go out sailing. On a close hauled course, put up enough sail to heel 
<DIV></DIV>the boat over about 15-20 deg. Make certain the rudder blade &amp; centerboard 
<DIV></DIV>are all the way down. On my Rhodes 22, the above tension settings cause the 
<DIV></DIV>mast to remain straight &amp; more or less centered in the boat. The primary 
<DIV></DIV>thing to check is the upper sidestays. On my Rhodes 22 with the above 
<DIV></DIV>unloaded tension settings, at 15-20 deg of heel, the windward upper sidestay 
<DIV></DIV>should have about 450 lbs tension &amp; the leeward upper sidestay should have 
<DIV></DIV>about 150 lbs of tension. I have my upper sidestays set-up such that the 
<DIV></DIV>leeward upper sidestay tension drops to 0 lbs at about 30 degrees of heel. 
<DIV></DIV>At this point, the windward upper sidestay will be under about 600 lbs 
<DIV></DIV>tension. Note, normally the stays are set-up to give proper shroud tension 
<DIV></DIV>&amp; the correct amount of weather helm with full sail set. This tends to 
<DIV></DIV>limit the weather window in which you can do this sort of tuning. 
<DIV></DIV>When all sails are properly trimmed &amp; the boat is "in the groove", there 
<DIV></DIV>should only a slight amount of weather helm. If there is a huge weather 
<DIV></DIV>helm, or neutral, or lee helm; then, you need to adjust the rake angle of 
<DIV></DIV>the mast. If you have neutral or lee helm; then increase the forestay 
<DIV></DIV>length. To get rid of excessive weather helm, shorten the forestay. The 
<DIV></DIV>balance of the boat is very sensitive to this mast rake angle, so change it 
<DIV></DIV>in increments of about 1/2" at a time. Note, a slight amount of weather 
<DIV></DIV>helm 
<DIV></DIV>is desirable because it provides feedback to the helmsman, thus allowing 
<DIV></DIV>him to steer a better course. Excessive weather helm tends to tire the 
<DIV></DIV>helmsman out. 
<DIV></DIV>Once I'm happy, I lock the adjustment in place by taping the lock nuts on 
<DIV></DIV>the turnbuckles. I find I only need to do this adjustment once. The 
<DIV></DIV>Rhodes 22 is such a strongly built little boat that nothing ever seems to 
<DIV></DIV>stretch or bend. I do check the side-to-side upper sidestay length at the 
<DIV></DIV>beginning of every season; but, it's never changed in the 13+ seasons I've 
<DIV></DIV>been measuring it. Trailering set-up only involves adjusting the lower 
<DIV></DIV>sidestays since the rest are not disturbed. 
<DIV></DIV>As far as rig tension settings on the trailer vs. off the trailer, I've 
<DIV></DIV>found the 
<DIV></DIV>only rig tension adjustment that significantly changes is the backstay 
<DIV></DIV>tension. 
<DIV></DIV>You can set the tension on the rest of the standing rigging according to the 
<DIV></DIV>above procedure on the trailer. It will be very close to optimum when you 
<DIV></DIV>get the boat in the water, certainly good enough to do the on-the-water 
<DIV></DIV>fine tuning described above. 
<DIV></DIV>FYI, I slack off on the backstay tension when Dynamic Equilibrium is not 
<DIV></DIV>being sailed. As I mentioned above, the backstay adjuster has sufficient 
<DIV></DIV>power to affect the shape of the hull. Greatly exaggerated, imagine the 
<DIV></DIV>ends 
<DIV></DIV>of the hull being pulled upward like a 22 foot long banana when the backstay 
<DIV></DIV>adjuster is tight! There is no sense leaving the hull &amp; rig under that kind 
<DIV></DIV>of 
<DIV></DIV>stress when the boat is not being sailed. 
<DIV></DIV>Jack, I hope this description of rig tuning helps you. Good luck! 
<DIV></DIV>Roger Pihlaja 
<DIV></DIV>S/V Dynamic Equilibrium 
<DIV></DIV>----- Original Message ----- 
<DIV></DIV>From: "Jack Goldberg" 
<DIV></DIV>To: 
<DIV></DIV>Sent: Monday, August 19, 2002 7:47 PM 
<DIV></DIV>Subject: [Rhodes22-list] shroud tension 
<DIV></DIV>&gt; This list has been helpful in the past, so I'll come to the trough of 
<DIV></DIV>&gt; knowledge to feed again. 
<DIV></DIV>&gt; I noted with interest the thread about the mast plate bolts coming loose 
<DIV></DIV>and 
<DIV></DIV>&gt; the response with regard to the tension of the shrouds. My 84' has a 
<DIV></DIV>&gt; standard main. When I bought the boat this spring, the shrouds were very 
<DIV></DIV>&gt; loose (obout 3 inches of play from side to side at about 3 feet from the 
<DIV></DIV>&gt; deck. The guy I bought the boat from said that was OK, but now I'm 
<DIV></DIV>worried. 
<DIV></DIV>&gt; Is there a spec' on how tight (or loose) the shrouds should be under no 
<DIV></DIV>&gt; load? 
<DIV></DIV>&gt; 
<DIV></DIV>&gt; Jack Goldberg, 
<DIV></DIV>&gt; 
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