I have a C-22 and have a question about the tension of the forestay. I set the boat up with 28 for the uppers and 24 for the lower shrouds ( Loos guage) I have an adjustable backstay, and I would like to know what is the recommended tension is for the forestay, with the backstay "off". Buy off I mean when there is no added tension applyed to the backstay. Thanks in advance. Dale SummerWind
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5%
With the backstay full "off" there should be 5% tension in the forestay. Set rake with about 30% forestay tension, and mark the backstay adjuster at about 40% forestay tension. For 3/16" wire this should be: 5% = 198# 30% = 1188# 40% = 1584# I have no ideas what the Loos numbers are for those tensions. Before someone chimes in ... Yes, I know those numbers are conservative. The numbers are for 316 Alloy 3/16" 1x19 SSAC. If the stay is 302/304 Alloy the numbers would be higher. Yes, some racers allow the mast to go way forward when sailing downwind. I'm not giving that sort of advice on-line.
With the backstay full "off" there should be 5% tension in the forestay. Set rake with about 30% forestay tension, and mark the backstay adjuster at about 40% forestay tension. For 3/16" wire this should be: 5% = 198# 30% = 1188# 40% = 1584# I have no ideas what the Loos numbers are for those tensions. Before someone chimes in ... Yes, I know those numbers are conservative. The numbers are for 316 Alloy 3/16" 1x19 SSAC. If the stay is 302/304 Alloy the numbers would be higher. Yes, some racers allow the mast to go way forward when sailing downwind. I'm not giving that sort of advice on-line.
Forestay tension/mast rake
I believe thats it is a matter of getting the proper mast rake, than the actual tension of the forestay. The tension on the forestay is going to vary with the tension that is placed on the adjustable backstay, which also changes the tension upon the shrouds. To start; the shrouds are slightly loosened, next, achieve the mast rake, (8" for fixed keels, or 6-7" for swing keels),by placing a weight on the main halyard and let hang about 12" below the boom, measure from the aft face of the mast to where the halyard crosses the boom, adjust the forestay until you get your measurement. Next; tighten backstay until slack is gone and it is snug, but not tight. Next; tighten upper shrouds until 28 on the loos gage "A", and 24 on the lower shrouds. Next; check the straightness of the mast, tweek if needed. Next; go sailing,( upwind and moderate wind conditions), and check the straightness of the mast again and tweek if needed. The late Great sailor,Dick king said to put maximum and minimum marks on the backstay adjuster line as reference points so you would kinda know where to set your backstay for different conditions. Do this by measureing the tension of the forstay(by using your backstay adjuster to create the different tensions and after all the tweeking is done). His guide ;was for tight tension on the forestay - 30:35 For loose tension on the forestay - 5:10 These are using the Loos tension guide "A".Remember Strong winds=tight, light winds=loose, except running then go loose
I believe thats it is a matter of getting the proper mast rake, than the actual tension of the forestay. The tension on the forestay is going to vary with the tension that is placed on the adjustable backstay, which also changes the tension upon the shrouds. To start; the shrouds are slightly loosened, next, achieve the mast rake, (8" for fixed keels, or 6-7" for swing keels),by placing a weight on the main halyard and let hang about 12" below the boom, measure from the aft face of the mast to where the halyard crosses the boom, adjust the forestay until you get your measurement. Next; tighten backstay until slack is gone and it is snug, but not tight. Next; tighten upper shrouds until 28 on the loos gage "A", and 24 on the lower shrouds. Next; check the straightness of the mast, tweek if needed. Next; go sailing,( upwind and moderate wind conditions), and check the straightness of the mast again and tweek if needed. The late Great sailor,Dick king said to put maximum and minimum marks on the backstay adjuster line as reference points so you would kinda know where to set your backstay for different conditions. Do this by measureing the tension of the forstay(by using your backstay adjuster to create the different tensions and after all the tweeking is done). His guide ;was for tight tension on the forestay - 30:35 For loose tension on the forestay - 5:10 These are using the Loos tension guide "A".Remember Strong winds=tight, light winds=loose, except running then go loose
The question was tension
not rake. Forestay length controls rake. Forestay tension controls headsail shape. The rake will change with the forestay tension. On most boats, setting the rake with your average upwind tension on the forestay gives good results. If there is a class tuning guide that says something different, go with the class tuning guide. If the rake measurement is given with no mention of the tension when the measurement was made, the number is suspect ... assume average tension. A 40 foot stay will stretch about 1 inch at 20% tension and 2 inches at 40% tension. The range between 5% tension and 40% tension on a 40 foot stay is 1.75", far too large for a meaningful rake measurement. Setting the rake at 30% tension will be within 0.50" on a 40 foot stay.
not rake. Forestay length controls rake. Forestay tension controls headsail shape. The rake will change with the forestay tension. On most boats, setting the rake with your average upwind tension on the forestay gives good results. If there is a class tuning guide that says something different, go with the class tuning guide. If the rake measurement is given with no mention of the tension when the measurement was made, the number is suspect ... assume average tension. A 40 foot stay will stretch about 1 inch at 20% tension and 2 inches at 40% tension. The range between 5% tension and 40% tension on a 40 foot stay is 1.75", far too large for a meaningful rake measurement. Setting the rake at 30% tension will be within 0.50" on a 40 foot stay.
Questions for Moody and Jay
Moody I have 1/8" standing rigging on the boat. Can you give me any numbers for that size wire? I purchased it from Catalina Direct, and it said it was 316. When you said set the backstay adjuster at 40% forestay tension what exactly do you mean? Do you mean do not adjust the backstay to exceed 40% of the forestay breaking strength? Hope these are not sutpid questions, but I would like to get this right. Thanks Moody. Jay Did Dick King mean that with the backstay adjuster "off" the forstay tension would be 5-10 on the Loos guage, and the max would read 30-35 on the Loos guage when the adjuster was at its max. Thanks to you as well Jay. It was nice of both of you to answer. Dale
Moody I have 1/8" standing rigging on the boat. Can you give me any numbers for that size wire? I purchased it from Catalina Direct, and it said it was 316. When you said set the backstay adjuster at 40% forestay tension what exactly do you mean? Do you mean do not adjust the backstay to exceed 40% of the forestay breaking strength? Hope these are not sutpid questions, but I would like to get this right. Thanks Moody. Jay Did Dick King mean that with the backstay adjuster "off" the forstay tension would be 5-10 on the Loos guage, and the max would read 30-35 on the Loos guage when the adjuster was at its max. Thanks to you as well Jay. It was nice of both of you to answer. Dale
You got it!
For 1/8" 316 Alloy the tensions are: 89# @5% 356# @20% 712# @40% The tension in the backstay will be lower than the tension in the forestay, due the wider angle that the backstay meets the mast. You have the concept right. Whatever backstay tension gives 40% forestay tension is a safe Maximum setting. Upper shrouds tend to be in the 15-20% range on most boats (trust the class tuning guide). Upwind forestay tension *in general* is about 5% higher than upper shroud tension for an "all around" setting. That would be 20-25% on the forestay. Set the rake at "all around" tension. When the backstay is all the way off, it is safe to have only 5% tension in the forestay (your Minimum setting). If you leave the boat rigged, set the backstay at your 20-25% setting to keep the rig stable while you are away. No sense leaving at the max setting and loose rigs can create shock loadings when the boat moves around in a passing wake or during high winds. As you get to know the boat and the sails, you will find the sweet spot for your boat sailing in your local conditions. Keep notes every time you change anything on the rig. It is always nice to be able to return to a known setting. If you are racing against other C-22's, two boat testing is the best way to dial the boats in. Keep one boat unchanged (mark and note the settings) then tune the other boat until it is faster. Swap sails and crew around to verify it was the tuning that made the difference. Tune the baseline boat to the new settings and return the test boat to the baseline settings. If the tuning made a difference, the settings should make the other boat faster also. If you spend one day a month doing two boat testing, both boats should be faster as time goes on ... then *you* can write the tuning guide for the C-22 in your local conditions and become "the guy to talk to".
For 1/8" 316 Alloy the tensions are: 89# @5% 356# @20% 712# @40% The tension in the backstay will be lower than the tension in the forestay, due the wider angle that the backstay meets the mast. You have the concept right. Whatever backstay tension gives 40% forestay tension is a safe Maximum setting. Upper shrouds tend to be in the 15-20% range on most boats (trust the class tuning guide). Upwind forestay tension *in general* is about 5% higher than upper shroud tension for an "all around" setting. That would be 20-25% on the forestay. Set the rake at "all around" tension. When the backstay is all the way off, it is safe to have only 5% tension in the forestay (your Minimum setting). If you leave the boat rigged, set the backstay at your 20-25% setting to keep the rig stable while you are away. No sense leaving at the max setting and loose rigs can create shock loadings when the boat moves around in a passing wake or during high winds. As you get to know the boat and the sails, you will find the sweet spot for your boat sailing in your local conditions. Keep notes every time you change anything on the rig. It is always nice to be able to return to a known setting. If you are racing against other C-22's, two boat testing is the best way to dial the boats in. Keep one boat unchanged (mark and note the settings) then tune the other boat until it is faster. Swap sails and crew around to verify it was the tuning that made the difference. Tune the baseline boat to the new settings and return the test boat to the baseline settings. If the tuning made a difference, the settings should make the other boat faster also. If you spend one day a month doing two boat testing, both boats should be faster as time goes on ... then *you* can write the tuning guide for the C-22 in your local conditions and become "the guy to talk to".
Thanks
Moody, Thank you for the great answer. I will set the boat up as you have outlined. It is always nice to hear from some one who knows their business. Thanks again Dale
Moody, Thank you for the great answer. I will set the boat up as you have outlined. It is always nice to hear from some one who knows their business. Thanks again Dale
Loos tension guide
Dale, as far as Dick Kings tension on the forestay, I'm not sure. Moody's thoughts should be a good starting point though. Dale, here are some numbers from the loos tension gauge comparison chart; Pounds of tension.../...percent of breaking strength Based on 1/8" cable Model (A) ModelPT-1 15 120...........5.7% 14 20 160...........7.6% 16 22 180...........8.6% 18 24 200...........9.5% 19 26 220..........10.5% 20 28 240..........11.4% 21 30 260..........12.4% 22 32 300..........14.3% 24 34 340..........16.2% 26 36 390..........18.6% 28 38 450..........21.4% 30 39 500..........23.8% 32 40 550..........26.2% 42 700..........33.3% 44 950..........45.3%
Dale, as far as Dick Kings tension on the forestay, I'm not sure. Moody's thoughts should be a good starting point though. Dale, here are some numbers from the loos tension gauge comparison chart; Pounds of tension.../...percent of breaking strength Based on 1/8" cable Model (A) ModelPT-1 15 120...........5.7% 14 20 160...........7.6% 16 22 180...........8.6% 18 24 200...........9.5% 19 26 220..........10.5% 20 28 240..........11.4% 21 30 260..........12.4% 22 32 300..........14.3% 24 34 340..........16.2% 26 36 390..........18.6% 28 38 450..........21.4% 30 39 500..........23.8% 32 40 550..........26.2% 42 700..........33.3% 44 950..........45.3%
Breaking strenght ??
Jay, Thanks. I have one further question. The Loos guage that I have is the model that you quote. The numbers that Moody has, puts the breaking strenght at about 1800 lbs. for 1/8" cable. The guide that comes with the guage puts it at 2100 lbs. That is a fair amount of differance. Can either of you put some light on this for me. I know that I am really on the right track with all of your help, but this seems like I need to know at what point to start from. Thanks again to both you and Moody. Dale
Jay, Thanks. I have one further question. The Loos guage that I have is the model that you quote. The numbers that Moody has, puts the breaking strenght at about 1800 lbs. for 1/8" cable. The guide that comes with the guage puts it at 2100 lbs. That is a fair amount of differance. Can either of you put some light on this for me. I know that I am really on the right track with all of your help, but this seems like I need to know at what point to start from. Thanks again to both you and Moody. Dale
different alloys?
Dale, Maybe it is based on a different alloy 302/304, as mentiomed in Moody's post. Have you been to the North sails web site? Try clicking on thier" One Design section", and click on the rigging for your boat. They do more of a visual on the forestay tension, than an actual measurement. I did talk to an rigging expert at North, Chad, and he said that you can do a visual, or you can measure the "sag" of the forestay by running another line down along the forestay, pulling it tight, and then measure the "sag" in the forestay from that line. North Sails say about 6" of "sag" in the forestay for light air, 3"-4" of "sag" for moderate air, and very tight and straight on the forestay in heavy air. I guess you could measure the tensions with your Loos gauge once the desired "sags" are met. Chad, at North Sails could not give me any numbers at all on the forestay tensions. I also can't, because I have never measured the forestay tension on my boat due to a foil/roller furler thats on my forestay. I go by imagenary line down the foil, to sight in my "sag". Due to the roller furler, my tension on the forestay is a little "harder on" most of the time, then I go by the "feel" of how she sails. I do take tension readings on all of the shrouds though. Dale, don't go to nuts over the numbers, sail and feel my friend! Jay
Dale, Maybe it is based on a different alloy 302/304, as mentiomed in Moody's post. Have you been to the North sails web site? Try clicking on thier" One Design section", and click on the rigging for your boat. They do more of a visual on the forestay tension, than an actual measurement. I did talk to an rigging expert at North, Chad, and he said that you can do a visual, or you can measure the "sag" of the forestay by running another line down along the forestay, pulling it tight, and then measure the "sag" in the forestay from that line. North Sails say about 6" of "sag" in the forestay for light air, 3"-4" of "sag" for moderate air, and very tight and straight on the forestay in heavy air. I guess you could measure the tensions with your Loos gauge once the desired "sags" are met. Chad, at North Sails could not give me any numbers at all on the forestay tensions. I also can't, because I have never measured the forestay tension on my boat due to a foil/roller furler thats on my forestay. I go by imagenary line down the foil, to sight in my "sag". Due to the roller furler, my tension on the forestay is a little "harder on" most of the time, then I go by the "feel" of how she sails. I do take tension readings on all of the shrouds though. Dale, don't go to nuts over the numbers, sail and feel my friend! Jay
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