I'm not sure where to ask this question, but I'll start here and see how it goes. I'm not racing, just cruising and daysailing, but I like to get reasonable performance from my Cal 28 (the newer one from 1986). One aspect of this is 90 - 95 degree tacks and 45 (maybe 40) degrees to the true wind with reasonable boat speed and leeway. An important part of acheiving this is rig tension. However, over tensioning a rig is a sure way to do real damage to an older hull and deck. So, here's the question: Since Cal is long gone, where can I get a recommendation for starting points for the standing rigging tensions? I have a Loos tension guage, but I'm at a loss where to start. I've seen recommendations for as much as 15 - 20% of the breaking strength of the wire. I'm pretty sure that's way too much for this hull. I've seen recommendations as low as the lee shrouds going noticably slack when on the wind. I'm sure that's too low for good windward performance. I also want to get the headstay/backstay tension high enough for reasonable genny shape without springing the hull. If I need to ask this somewhere else, please point me in the right direction. I'm planning on re-rigging over the winter (the standing rigging is original), and I'd really like to have a good starting point for next year. I'm going to store her with the mast down, so I have to start from somewhere next year anyway.
Rig tension
- Thread starter Smitty
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I suspect you are looking to 'tune' your rig not 'tension' it. If you're looking for windward performance, the very first thing to set up is mast rake. Increasing the length of the headstay will increase mast rake, increase pointing and weather helm. Put in as much rake as your helm can withstand. Then go ahead and finish tuning the rest of the rig.
Tuning
Smitty, I don't believe in giving out professional advice, if one is not a rigger for instance. That said, what alan said, sounds like to me at least, is for RACING. True enough for that, but a Cal is more of a cruiser, and raking a mast can cause trouble, like sheering off the bow terminal, and stressing the hull. go online, find "The Rigger's Apprentice". This book will give you all the information you need to tune, without a tesioning device. I do not have the room nor am I a rigger, I am a surveyor, and hope this helps you out in the long run. Terry 415-722-7695
Smitty, I don't believe in giving out professional advice, if one is not a rigger for instance. That said, what alan said, sounds like to me at least, is for RACING. True enough for that, but a Cal is more of a cruiser, and raking a mast can cause trouble, like sheering off the bow terminal, and stressing the hull. go online, find "The Rigger's Apprentice". This book will give you all the information you need to tune, without a tesioning device. I do not have the room nor am I a rigger, I am a surveyor, and hope this helps you out in the long run. Terry 415-722-7695
Tuning info
Hi Smitty - Terry's recommendation for Brion Toss' rigging book is a good one. I have it and use it regularly - besides having good instruction for tuning your rig it also has great information on all kinds of knots, materials, methods etc. I think the Loos gauge is a great tool for ensuring even ditribution of loads. I agree that 15-20% of breaking strength seems high; I don't recall the recommendation but it should be more like 10-15% (if I recall there are different ranges for uppers and lowers). If I find specifics I'll let you know. Best, Trevor
Hi Smitty - Terry's recommendation for Brion Toss' rigging book is a good one. I have it and use it regularly - besides having good instruction for tuning your rig it also has great information on all kinds of knots, materials, methods etc. I think the Loos gauge is a great tool for ensuring even ditribution of loads. I agree that 15-20% of breaking strength seems high; I don't recall the recommendation but it should be more like 10-15% (if I recall there are different ranges for uppers and lowers). If I find specifics I'll let you know. Best, Trevor
Terry, putting mast rake into a rig has nothing to do with sheering off anything...nor stressing the hull. Tuning a rig CORRECTLY has nothing to do with RACING or not. Either the rig is correct or it isn't, sails are trimmed correctly or they aren't, regardless of racing. Mast rake simply defines how far forward or aft the masthead sits with respect to the foot. The AMOUNT of tension put on the shrouds after the rake is set will determine the stress levels.
Rig Tune
I'm a rigger. Basic dockside mast tune is not rocket science. Seldon has a very nice tuning guide. I've added a link. You don't need anything fancy. 1x19 wire stretches 1mm in 2000mm for each 5% of rated strength. If you measure a hand tight shroud 2000mm up from the top of the swag, the marks will be 2003mm apart when the wire has 15% tension. 15% is a good staring point. From there, sail the boat. Leeward shrouds should never go slack. Wind them up a turn at a time until they are at least taught when the boat has 20 degrees heel. The tension in the weather shrouds is from the sails heeling the boat. If 30 degrees heel creates 25% tension in the wire it doesn't matter what the dockside tension was (unless it was more than 25%). If heeling your boat 30 degrees doesn't break the rig, adding that much tension to the rig at the dock won't hurt anything. Loose rigs cause more failures than tight rigs.
I'm a rigger. Basic dockside mast tune is not rocket science. Seldon has a very nice tuning guide. I've added a link. You don't need anything fancy. 1x19 wire stretches 1mm in 2000mm for each 5% of rated strength. If you measure a hand tight shroud 2000mm up from the top of the swag, the marks will be 2003mm apart when the wire has 15% tension. 15% is a good staring point. From there, sail the boat. Leeward shrouds should never go slack. Wind them up a turn at a time until they are at least taught when the boat has 20 degrees heel. The tension in the weather shrouds is from the sails heeling the boat. If 30 degrees heel creates 25% tension in the wire it doesn't matter what the dockside tension was (unless it was more than 25%). If heeling your boat 30 degrees doesn't break the rig, adding that much tension to the rig at the dock won't hurt anything. Loose rigs cause more failures than tight rigs.
Follow up
Hi Smitty - I found some notes that indicate a good baseline range for tensions as a percentage of rated breaking strength: lowers: 10-12% (3/8" on my boat) intermediate: 12-15% (5/16" on my boat) uppers: 15-20% (3/8" on my boat) As Moody alluded to, it's important to sail the boat and experiment - don't just rely on numbers from a gauge. That being said, I find the Loos gauge useful to approach symmetry port to starboard as close as possible. Try to get the mast in column and then play with rake if you have a flexible enough mast and don't have inmast furling to worry about. Have fun! Trevor
Hi Smitty - I found some notes that indicate a good baseline range for tensions as a percentage of rated breaking strength: lowers: 10-12% (3/8" on my boat) intermediate: 12-15% (5/16" on my boat) uppers: 15-20% (3/8" on my boat) As Moody alluded to, it's important to sail the boat and experiment - don't just rely on numbers from a gauge. That being said, I find the Loos gauge useful to approach symmetry port to starboard as close as possible. Try to get the mast in column and then play with rake if you have a flexible enough mast and don't have inmast furling to worry about. Have fun! Trevor
Check your shroud/stay sizes
Trevors baseline numbers apply to the original size stays and shrouds. On my boat, the PO had replaced the #5 shrouds with #6. Using the percentages for #6 rigging would definately overstress my chainplates.
Trevors baseline numbers apply to the original size stays and shrouds. On my boat, the PO had replaced the #5 shrouds with #6. Using the percentages for #6 rigging would definately overstress my chainplates.
Thanks all
Great, informative responses. First thing I'm gonna do is order Brion's book and read it. But, I've got a new question: Does anyone know where I can find out what the Cal supplied standing rigging sizes should be?? I'd like to make sure that no one has changed the sizes on my boat and use the original sizes to figure all this out. Thanks again for all the information. -Smitty
Great, informative responses. First thing I'm gonna do is order Brion's book and read it. But, I've got a new question: Does anyone know where I can find out what the Cal supplied standing rigging sizes should be?? I'd like to make sure that no one has changed the sizes on my boat and use the original sizes to figure all this out. Thanks again for all the information. -Smitty
Wire sizes
Capt Jim, no worries. #5 is 5/32, #6 is 6/32 (3/16) In 316 1/19 wire: 5/32 - 2800# x 15% = 420# 3/16 - 3960# x 15% = 594# If you use a gauge to tension the 3/16 to 420# you have about 10% tension. 3/16 tensioned to 15% is about equal to 20% tension in the 5/32 wire. Over the years we've moved from 302 alloy to 316 alloy. The 302 is stronger, the 316 has more corrosion resistance (stays shiny longer). 5/32 302 alloy wire is rated 3300#, about 15% stronger than 316 alloy. It is not uncommon to go up one size when replacing 302 with 316. If 302 alloy 5/32 wire needed 20% tension (660#), 316 alloy 5/32 at 660# would be over 23% of rated strength. 3/16 at 660# would only have 17% tension. How to tell if you have 316 or 302 wire on your boat? Use a magnet. 302 wire is slightly magnetic, 316 is not. If your magnet "sticks" to the wire it's 302.
Capt Jim, no worries. #5 is 5/32, #6 is 6/32 (3/16) In 316 1/19 wire: 5/32 - 2800# x 15% = 420# 3/16 - 3960# x 15% = 594# If you use a gauge to tension the 3/16 to 420# you have about 10% tension. 3/16 tensioned to 15% is about equal to 20% tension in the 5/32 wire. Over the years we've moved from 302 alloy to 316 alloy. The 302 is stronger, the 316 has more corrosion resistance (stays shiny longer). 5/32 302 alloy wire is rated 3300#, about 15% stronger than 316 alloy. It is not uncommon to go up one size when replacing 302 with 316. If 302 alloy 5/32 wire needed 20% tension (660#), 316 alloy 5/32 at 660# would be over 23% of rated strength. 3/16 at 660# would only have 17% tension. How to tell if you have 316 or 302 wire on your boat? Use a magnet. 302 wire is slightly magnetic, 316 is not. If your magnet "sticks" to the wire it's 302.
north sails
Someone posted this question on the North Sails website and they provided an easy-to-follow, clear answer...i looked at Moody's link to Selden, but I still think North spelled it better than Selden or I could have put it.
Someone posted this question on the North Sails website and they provided an easy-to-follow, clear answer...i looked at Moody's link to Selden, but I still think North spelled it better than Selden or I could have put it.
and then i saw this...
while looking for that first link. The link is actually for a Cal 20, but click on "Tuning Guides" at the top and you get a menu for other boats
while looking for that first link. The link is actually for a Cal 20, but click on "Tuning Guides" at the top and you get a menu for other boats
Re: North Sails response .. 
Hey Peter, great link! North's response was pretty good, but they got the order wrong and forgot to ask a question. They rightly pointed out that loose shrouds can cause weather helm, they should have recommended getting the lateral tune right *then* adjusting rake. When the customer says the rake is too much when measured with the hanging weight, the first thing to check is contents of aft berths and lockers ... make sure the boat is on her lines before you go measuring the rake with a plumb bob. A CS 36 probably has a 40' luff measurement. Most boats are happy with 1-3 degrees of rake. On a 40 foot luff 1 degree of rake is about 8.5 inches. 3 degrees is 25 inches. At 16-18 that the owners states, he's right in there at about 2 degrees of rake.
Hey Peter, great link! North's response was pretty good, but they got the order wrong and forgot to ask a question. They rightly pointed out that loose shrouds can cause weather helm, they should have recommended getting the lateral tune right *then* adjusting rake. When the customer says the rake is too much when measured with the hanging weight, the first thing to check is contents of aft berths and lockers ... make sure the boat is on her lines before you go measuring the rake with a plumb bob. A CS 36 probably has a 40' luff measurement. Most boats are happy with 1-3 degrees of rake. On a 40 foot luff 1 degree of rake is about 8.5 inches. 3 degrees is 25 inches. At 16-18 that the owners states, he's right in there at about 2 degrees of rake.
Selden en anglais?
I checked Moody's link, and got a document in French. Looks like a great document, but my francais is not bon enough. Do you have an English language Selden document link? Dick
I checked Moody's link, and got a document in French. Looks like a great document, but my francais is not bon enough. Do you have an English language Selden document link? Dick
Oops!
Sorry, Try this one. ... or go to: http://www.seldenmast.com/ and go to Manuals, scroll down the page to General Information. The file you want is "Hints and advice on rigging and tuning of your Seldén mast" -Randy
Sorry, Try this one. ... or go to: http://www.seldenmast.com/ and go to Manuals, scroll down the page to General Information. The file you want is "Hints and advice on rigging and tuning of your Seldén mast" -Randy
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