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Rig tension

8K views 54 replies 13 participants last post by  justin forkix 
#1 ·
I've read some of the older posts on this as well as the Selden and other guides online and am still a bit unsure about my rig tension.

I recently hired a rigging company to do a static tune at the dock. They did a great job and provided lots of information on a subject I know nothing about. We have a double spreader Isomat NG-60 masthead rig with 1/4in shrouds and 5/16 stays. Compared to previous settings, I was surprised how much prebend got dialed in with the forward lowers and how loose the cap shrouds were.

However, when beating into 15ish knot winds, I noticed the mast falling way off to leeward. I've since significantly tightened the cap shrouds. Using a Loos PT-2 , we're now at 16% (1300lbs) on the cap shrouds and forward lowers, 9% (800lbs) on intermediates and 7% (600) on the aft lowers. This seems about right to me but the top 1/3rd of the mast still falls off slightly to leeward on a beat (none of the leeward shrouds have any jiggle)

So what should I do from here? Logically I should probably tighten the cap shrouds a few more turns, but I'm already past the "15% rule" on a 35y old boat....I've read some references to loosening the intermediates...and some sources indicate a slight bend to leeward is ok...Thoughts?

Also, our backstay is a Navtec Hydraulic unit in psi. Boat broker told me to never go past 1000, the riggers mentioned 2000. How does one convert psi on the Navtec to pounds of tension?
(For CSOA members, I apologize for the double post, just trying to get some opinions from a wider audience).

cheers,
Novic
 
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#2 ·
Ease the intermediates and lowers. Out of column in 15 knots is not good because it gives a warning about what might happen at 30 knots....4 times the force. It may not take much loosening...start with half a turn on each one.

But you dont say how much bend you see. Compare the distance to the mast width or the mainsail track width. I am just a sailor...not a rigger...I wouldnt want any bend at 15 knots on what sounds like a conventional aluminum rig.

The Navtec manual has the conversion. Depends greatly on the model. But you might use a Loos gage too.

Boat broker advice? Heh.
 
#3 · (Edited)
When you said the rig was falling off to leeward in 15kn was the top falling off, the middle, or the entire thing? If just the top then tighten the caps, if just the middle then the middle set, if the entire rig, then both.

But that's just the tune for 15kn. In 20kn you need to do it again, and if sailing in 5kn you need to loosen them.

The thing about rig tension is that it isn't static, it is a moving target that depends on sea state and wind strength. Of course most cruisers set it for some neutral and don't stress over it very much. Racers will typically have a book of prefered tensions for different conditions and adjust daily.
 
#4 ·
Aloof and stumble, thanks for the input.
Only top third of mast (above 2nd spreaders) is still falling off slightly. From what I recall, it's less than half a mast width.
I'll try loosening the intermediates/lowers slightly next time we're out.
As for wind speeds, I'm still a beginner and just looking to have everything set at a safe and reasonable state for our normal wind speeds.
I'm usually sailing with my wife and toddler with a "rule" for max 25deg of heel: so anything much more than 20 knots and we're heading for an anchorage.
 
#5 · (Edited)
"I'm usually sailing with my wife and toddler with a "rule" for max 25deg of heel: so anything much more than 20 knots and we're heading for an anchorage."

Don't understand this. This week out cruising with the bride. She hasn't been out for close to 1/2 of a year just the two of us and therefore a nervous nelly. Funny weather. Fog and wind in teens so upwind over 20. Risk of t storms later this week.
So you just change your style as her lovelyness gets her feet wet again and relearns the boat.
Just the genny downwind with no pole. Go 160 s then 160p. Slow but stress free.
Reef main right off. we keep it less than 20*. Use the Solent not the genny upwind. So you lose a knot. Big deal.
In short ease her into it. Over reef every thing . No wing and wing. No poles, no kites.
For sure going out if it's constantly 20s-30s is no fun and foolish as you run the risk of making non sailors of your loved ones. But if you're already out and worse is not on its way you're going to see >20 apparent fairly commonly. It's not scary if you're reefed down snug and will give them confidence.
All week- upwind reefed. Downwind no main. By next week we'll be back to our usual pattern as her willies go away but still conservative.
 
#6 ·
If the top is falling off just a touch then just tighten the uppers by half a turn. The guys at the dock did a pretty good job, now you just have to dial it in a touch. Add a half a turn, take a half off... Add a quarter turn...

Once you are happy with the tuning in a given wind condition take a set of digital calipers (harbor freight $10) and measure the distance between the turnbuckle studs on every shroud and log it.

Continue this is different wind strengths (say in increments of 5kn) starting at 5 and going up to 25. Once these are logged (caliper distance) you will always be able to get back to them immediatly without needing to go thru the process of on the water testing.

At a minimum I recommend once a quarter setting the tune for the prevailing conditions that season. But obviously you can do it more often. It only takes a few seconds to set the boat up for the day.
 
#7 ·
Outbound,
I appreciate your input and I don't want to drift much from my original question.
I do however want to say this: Different strokes for different folks.

I love sailing. I'm not much good at it and am still learning lots but our boat feels great doing 7+knots upwind with a pile of water coming over the side. My family doesn't enjoy this at all. If my wife had her way, we'd own a houseboat. Our boat works for us despite this because we all get a bit of what we enjoy. I get to sail once in a while and my family gets to go to the beach, have BBQ's, swim and go exploring in the dinghy. When the wind/waves pick up I do my best to keep the boat flat and well behaved, but with our original 1980's #2 genny, partial furling doesn't work so well. Yep, new sails are on the budget list but so are a bunch of other things. We just added a second reef to our main which should help a bit in the meantime. Downwind is certainly much nicer in a blow but since we're sailing to get from point A to point B I don't usually get much say about point of sail. Given all of this, it's just easier and nicer for everyone if we plan around anticipated weather and either motor through protected routes or stay put at anchor. Being attentive to my family also means I have cooperative and engaged crew when I do need help handling the boat. And once in a while when the weather lines up, we get some pretty sweet sailing. Last summer, we did a 120+ mile overnight shot up the bay doing 5-6 knots with the wind over the beam. Everyone slept peacefully down below while I puttered around in the cockpit watching the stars go by.

I know this doesn't make any sense to most and I have no delusions of being a "real sailor". However, the boat is primarily a means for us to all get away and spend some quality time as a family. The fact that we have the means to do this and that our RV happens to float and have a pole I can hang some canvas on, is privilege enough for me. To each their own.

Now...back to shroud tension.

Novic
 
#25 ·
Outbound,
I appreciate your input and I don't want to drift much from my original question.
I do however want to say this: Different strokes for different folks.

I love sailing. I'm not much good at it and am still learning lots but our boat feels great doing 7+knots upwind with a pile of water coming over the side. My family doesn't enjoy this at all. If my wife had her way, we'd own a houseboat. Our boat works for us despite this because we all get a bit of what we enjoy. I get to sail once in a while and my family gets to go to the beach, have BBQ's, swim and go exploring in the dinghy. When the wind/waves pick up I do my best to keep the boat flat and well behaved, but with our original 1980's #2 genny, partial furling doesn't work so well. Yep, new sails are on the budget list but so are a bunch of other things. We just added a second reef to our main which should help a bit in the meantime. Downwind is certainly much nicer in a blow but since we're sailing to get from point A to point B I don't usually get much say about point of sail. Given all of this, it's just easier and nicer for everyone if we plan around anticipated weather and either motor through protected routes or stay put at anchor. Being attentive to my family also means I have cooperative and engaged crew when I do need help handling the boat. And once in a while when the weather lines up, we get some pretty sweet sailing. Last summer, we did a 120+ mile overnight shot up the bay doing 5-6 knots with the wind over the beam. Everyone slept peacefully down below while I puttered around in the cockpit watching the stars go by.

I know this doesn't make any sense to most and I have no delusions of being a "real sailor". However, the boat is primarily a means for us to all get away and spend some quality time as a family. The fact that we have the means to do this and that our RV happens to float and have a pole I can hang some canvas on, is privilege enough for me. To each their own.

Now...back to shroud tension.

Novic
Makes perfect sense to me. I've been sailing since I was 12. Now I'm teaching my wife who is new to it. It's important that every time we go out she has a good time. That means for us, nothing that feels dangerous. For her it's not so much about the heel angle as about my level of tension and keeping me in the cockpit. She gets nervous when I go to the mast to reef, for example, so I do that at the dock before we leave. We go slower but happier. Happier is better for cruisers.

Ahem this isn't the first wife I've taught to sail. You're doing the right thing. For a long time my former wife was uncomfortable with more than 15 deg heel (Tanzer 22). So I sailed flat. Eventually, she got more comfortable and I remember one day sailing at 20 deg, two reefs, storm jib, only boat out there having a great time.

Keep doing what you're doing. She'll learn to love it.
 
#8 ·
Stumble,
Thanks for the tips. The caliper is a great idea and something we already have on board.
Do you use cotter pins, split rings or seizing wire for your turnbuckles?
the original cotter pins + tape were a pain so I'm now trying split rings. Is there an easier way to do this and allow frequent adjustment?

cheers,
Novic
 
#9 · (Edited)
I'd recommend using the Loos and tightening everything to 15%. I can see no benefit to having the lowers looser than the caps and particularly having the fore & aft lowers at different tensions.

One thing - how old is your Loos? They can get "soft" with age
 
#10 ·
I'd recommend using the Loos and tightening everything to 15%. I can see no benefit to having the lowers looser than the caps and particularly have the fore & aft lowers at different tensions.
This is contrary to the art of rig tuning. Setting everything to 15% of value ignores the reality of the rig loads under sail.

On a well tuned rig it is common for the cap shrouds, at the dock, to be set tight, the intermediates a little looser, the lower forwards maybe about the same as the intermediates, and the lower aft just barely tight. This is what I learned from noted designer Bill Lapworth long ago. The forward lowers induce the bend...get it going the right way. The aft keep it from bending too far when some monkey gets over-enamored with pumping up the Navtec.

The reality is the rig tensions, actually the lengths, are set as needed to obtain the results desired. Not at an arbitrary 15%.

The top third falling off half a mast width in a moderate breeze is too much, in my opinion. It is a safety thing. The mast should not go "out of column" in a surprise puff. It could come tumbling down.

In a very basic sense, easing the intermediate shroud is the same as tightening the cap shroud as far at bend is concerned. Depends what max cap shroud tension is needed to keep the leeward shrouds from flopping around in heavy air. I wouldn't normally go any higher than necessary to stop the flopping in a heavy breeze.

Remember that the 15% load, or whatever it ends up being to get the job done does not add to the load under sail.

As for the cotter pins, I cam all the way across the Pacific with my turnbuckle bodies lashed together with some small line. No pins or ringdings. I was fiddling with the tension under sail for 8000 miles. Unlashing and re-lashing is far easier that fiddling with pins. They never moved anyway - never pulled on the lashings.

The measuring idea (above is good). But it is only good for a short time as the wire stretches. The Loos is better for returning to a set value after some sailing time has passed. However I just use my eyeballs now because I have spent so many hours looking at the rig.
 
#11 ·
Rig tuning was an art in the days of wood spars. With alloy & carbon spars it is a science requiring measuring tools to get it tuned accurately.

You can build a whole boat by eye and rules of thumb - Brent does it - but most people use measuring devices to get accuracy.

Rigs are no different.

If I sailed all the way across the Pacific having to fiddle with my standing rigging I think I'd think to myself "this ain't working right".
 
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#12 ·
Top racers, the one's I hang out with, tune by eye, while sailing, constantly, all the way across an ocean if necessary. Not by Loos gauge. They put the bend where they want it. They take it out where they don't. How would a Loos gauge, sitting at the dock, even indicate a improperly bending rig? I assure you their rigs are "working right", as is mine.

The Loos gauge is handy when the right tune is found. Some strict One-Design race boats may be so consistent boat-to-boat that Loos numbers can be used unchanged from boat-to-boat. But a slight change to the main cut and that becomes useless. Very unlikely for boats on this board, however.

Some boats have heavy "utility pole" masts: Perhaps rig tune doesn't matter. I would guess Brent's boats might be such.

Rig tune is not a science as it is all very well understood by those who know. It is indeed an art: a technology. The technology clearly says, in many documents, if the head falls to lee and the caps are tight enough, ease the several lowers. Simple.
 
#13 · (Edited)
Sorry N my bad. All I was trying to say is you can match your sailing to who is on the boat and what you want out of the sail. You have a fine boat with lots of options. You have a great attitude toward sailing. Just have fun.
Still as a dumb witted cruiser probably would take 1/2 a turn on the caps. If no effect as Aloof says ( his is a great post) ease intermediates then lowers a smig. If then mast stays in column and doesn't pump. Good to go.
 
#14 ·

I love sailing. I'm not much good at it and am still learning lots but our boat feels great doing 7+knots upwind with a pile of water coming over the side. My family doesn't enjoy this at all. If my wife had her way, we'd own a houseboat.


Novic.... You... are on an ego trip my boy. suggestion.. no! .. I'm telling you! Back off of proving how great you are and sail sensibly, or you will become a solo sailor like so many doing what you are trying to do/prove/ show off. "Man vs the sea" only ever has; one winner.

Old boat = don't over tension the rig. get is just right and loose enough that the stays don't "strum" like a guitar. you don't say what boat you have so we are just guessing on the rig.
 
#18 ·
Thanks all for your thoughts.

Denise: trust me, I get where you're coming from. Our boat is a CS36t (Canadian Sailcraft 36 "traditional") built in 1981 in Brampton, Ontario. CS 36 sailboat specifications and details on sailboatdata.com
Outbound: no need to be sorry. Just trying to explain our particular circumstances and why we're out there doing what we're doing.

I'm going to start off by giving another half turn on the caps to see where I end up. After that I'll start loosening the intermediates/lowers a touch to see if that helps. It'd sure be nice to have the knowledge to tune by sight/feel but I have no idea what "tight" or "sloppy" feels like, hence the Loos. The gauge is brand new so I'm assuming it's accurate. The numbers I'm reading are 38,32 and 28 which I think convert to the breaking strength numbers I came up with. It's interesting to see everyone's different opinions on this. Our mast probably qualifies as a "telephone pole" so I'm sure there's some leeway (pun intended) in the final settings. I won't be back up at the boat for a bit but we have a 3 week trip to the North Channel planned in mid August. I'll let you all know how the rig does.

cheers,
Novic
 
#20 · (Edited)
The SIMPLICITY of rig tuning.

The chief reason for specific tensions of rigging is simple: to prevent catastrophic buckling failure of the mast when the mast is at maximum (compressional) load along its 'long' axis. Buckling failure is a quite complex failure of easy/rapid onset failure mode. To prevent buckling failure the mast has to be held 'straight' by the wire and with NO adverse bending (a 'little' adverse bending is generally OK).
The rigging system adds SIGNIFICANT stiffness to the mast, and in so doing prevents adverse bending; thus, prevents 'buckling failure'.
Since the usual mast is relatively light weight, thin sectioned and relatively small in cross section, without the rigging to keep it 'unbent' when under load, it is highly subject to buckling. Without the rigging, you'd need a mast of the cross section and thickness of that approaching the diameter of a marble column of a greek temple. All the rigging has to do is be so tensioned so that on ALL angles of boat heel and various wind loadings to the sail, the mast remains relatively straight (side to side). If the mast top moves back and forth a bit from side to side as the boat heels over - not a problem, as long as the mast remains relatively straight. 'Small' side to side deflections are meaningless, even with respect to sail shape and boat 'performance. The small deflections are the result of the (expected) 'elasticity' of the rigging wire. Your 'fine tuning' will get these 'small deflections' removed.

Generally sailboats are quite similar in shape ... the beam of the boat vs. the general height of the boats mast height are pretty much the same (ratios); and thus, the spreader lengths have the same length ratios to mast height. So, with this in mind the spar manufacturers who build their products - including product strengths and relative stiffnesses with these ratios in mind - have it 'all worked out' so that a general 12-15% wire tension will keep the mast straight .... for the prevention and lessening of the potential of buckling failure. Since there are small dimensional differences between the various boat 'models' and types, its up to the owner/sailor to fine tune these tensions .... so that the mast stays relatively straight (side to side) under all wind and heel angle conditions, up to about 45° of heel angle.
With respect to the aerodynamics of sailing, its not going to make ANY difference in boat speed or boat performance if the mast top and mainsail is 1° (about 1 foot or so for a ~60 ft. mast) further to port or starboard.
Rx: Tighten the rig (side stays) to about 12-15%, go sailing and well heeled over, check to see if the mast remains somewhat 'straight'; if not, then readjust so that the mast 'is' straight .... the reason for this is to prevent BUCKLING FAILURE of the mast.

A tweak: Pre-bending the mast - forcing a small bowing in the fore/aft plane and with the convex bowing towards the bow. This stiffens the mast vs. the potential of buckling failure and also prevents harmonic oscillations. Depending on 'normal' stiffness of the typical mast, a single spreader rig should be 'pre-bowed' by ~3/4"; multi-spreader rigs should be pre-bowed by ~1/2" PER each spreader set.
Your sailmaker has already added this 'shaped curve' to the luff of your mainsail in expectation of this proper 'pre-bend' or pre-bowing. If you don't have this pre-bend, your mainsail will 'set' in a slightly powered-up shape - boat will heel more, won't be as 'fast', boat will tend to be 'cranky' and a bit 'unforgiving' at the helm.
(FWIW - the above is for 'typical' cruiser/racer boats. Many planing hulled 'sport boats' with 'bendy-rigs' can carry up to several FEET of pre-bow.
Rx: set the correct amount of 'pre-bow' / 'pre-bend' in your mast if you don't want a cranky boat ..... pre-bow primarily 'stiffens' the mast which aids in the prevention of buckling failure. Your sailmaker, with 99% probability, cut your mainsail expecting this mast 'pre-bow' to be present.

Fore/aft ... headstay/backstay tensions.
A sail attached to a wire or 'foil' over a wire, when the sail is wind-loaded will predictably sag into a (catenary) curve. Your sailmaker has already compensated for this sag by cutting a matching (catenary) curve into the leading edge of your jib/genoa. (For a sail to be used principally in 'different' wind ranges, you will have to specify that wind range .... or what you're going to get is for 12-15kts.) The typical shape cut into that jib/genoa luff is for sailing in 12-15 knots of wind and the sail is hanked, etc. onto 'wire' that is tensioned to 12-15% tension. If the wind is less, there will be less sag ... so loosen the backstay. If the wind is higher than 15kts, then tighten the backstay.
Rx: get used to or memorize what that jib/genoa luff SAG looks like when beating in 12-15kts. At wind speeds other than 12-15kts, change the backstay tension so that the luff curve (sag) looks like the shape you automatically get at 15 knots. Just get used to maneuvering your eyeball so that you visualize the side of the (straight) mast and then make a visual comparison of expected curve in that headstay/jib luff - you'll want the SAME amount of luff leading edge curve in ALL wind and sea state conditions. (note: winching-in on the jib sheets, like a gorilla, is a good way destroy that proper leading edge jib/genoa luff shape)
There are more 'precise' ways to set the 'fore/aft' rig tension to arrive at the CORRECT luff sag shape ------ look in the archives, or will be discussed in detail again - later.

Hope this highlights the 'core reasons' and simplicity of getting proper rig tensions:
A. prevention of buckling failure; and,
B. gaining proper SHAPE of the headsail.
All the rest is for gonads to the wall racing, etc. and where you need 0,05% faster boat speed and a 0,5° higher pointing angle.
;-)

For a 'discussion' of buckling failure of 'long' thin sectioned shapes: http://www.assakkaf.com/courses/enes220/lectures/lecture26.pdf

FWIW- I keep my loos gage mounted to my backstay when sailing ... I want to SEE what the rig is doing; and, I don't want that loos gage to go 'over' 30% even when Im over on my beam ends. Going over 30% rig tension when sailing is a quick way to prematurely destroy the rigging, chainplates, and all the connections. FATIGUE is greatly enhanced and accelerated when such rigging components are at above 30% tension.
 
#22 ·
Look I don't do this often,though it has been pointed out to me that sometimes my posts can be a little curt. But everything RichH just posted is wrong. i am not going to try and unpack everything there because it would take too long, but please ignore that advice. The first paragraph is acceptable enough, but everything past that is just fundamentally wrong.

Tuning a rig is a dynamic thing that should change with the conditions. If it's blowing 5 or 15 the rig behaves differently, and there are real and noticeable differences in speed, heel, and pointing from a mistuned rig. A rig tuned for 15 in 5 will lack power and drive as the overly tight mast chokes the sails, and the lack of a luff curve in the jib prevents it from generating any power.

A rig tuned for 5 in 15 will be too powerful, and fall off the leeward. This adds heel, robs speed, and pointing all while generating funky helm control. Normally it causes excess weather healm, but can add lee helm if the rig is very loose.

Like almost everything else there is a compromise in tuning a rig between ease of use and boat performance. If you set it for the prevailing winds in your area then you are going to get reasonable all round performance. But if you want the boat to sing you have to set it every day for the conditions of that day. Because something as simple as adding one more person to the rail of the boat will change how the rig behaves.

The ideal is 1) the appropriate amount of prebend, 2) the right amount of rake, 3) the right headstay tensions, 4) the mast in column, 5) controlled pumping (normally done with runners or a baby sta) 6) with the shrouds as loose as possible.

How much prebend? Depends on the boat, the cut of the sail, and the mast. One cut of J-35 sails requires 16" another set 3". The 16" set however requires far higher backsta tension while beating so it's normally only sold to racers.

How much rake? Depends on the boat and sails. Normally between 1 and 15 degrees. Start at 5 and shift it around to eliminate healm preassure. A little weather helm is a good thing on a cruising boat, but may be dialed out or minimized for racing.

How much headstay tensions? Depends on the cut of the head sail. Some need more curve than others in the same conditions. This is purely a sailmakers question. The tighter it is the lower the drag but the lower the power available. It also narrows the groove so the sail design should take into account the skill of the driver.

And there are real downsides to overly tight shrouds. Like ripping the entire deck off the boat (rare), or deforming the hull (quite common). Which is why you want the shrouds to me as loose as possible in the current conditions.


As for why shrouds tend to come in at between 15-20% their MBL... That's because of the 5:1 safety factor that most designers use for standing rigging. When you design a rig and get an expected max load of X, designers then tend to use a wire with a strength of 5X. That is NOT supposed to be the normal tuning number.
 
#24 ·
Look I don't do this often,though it has been pointed out to me that sometimes my posts can be a little curt. But everything RichH just posted is wrong. i am not going to try and unpack everything there because it would take too long, but please ignore that advice. The first paragraph is acceptable enough, but everything past that is just fundamentally wrong.

Tuning a rig is a dynamic thing that should change with the conditions. If it's blowing 5 or 15 the rig behaves differently, and there are real and noticeable differences in speed, heel, and pointing from a mistuned rig. A rig tuned for 15 in 5 will lack power and drive as the overly tight mast chokes the sails, and the lack of a luff curve in the jib prevents it from generating any power.

A rig tuned for 5 in 15 will be too powerful, and fall off the leeward. This adds heel, robs speed, and pointing all while generating funky helm control. Normally it causes excess weather healm, but can add lee helm if the rig is very loose.

Like almost everything else there is a compromise in tuning a rig between ease of use and boat performance. If you set it for the prevailing winds in your area then you are going to get reasonable all round performance. But if you want the boat to sing you have to set it every day for the conditions of that day. Because something as simple as adding one more person to the rail of the boat will change how the rig behaves.

The ideal is 1) the appropriate amount of prebend, 2) the right amount of rake, 3) the right headstay tensions, 4) the mast in column, 5) controlled pumping (normally done with runners or a baby sta) 6) with the shrouds as loose as possible.

How much prebend? Depends on the boat, the cut of the sail, and the mast. One cut of J-35 sails requires 16" another set 3". The 16" set however requires far higher backsta tension while beating so it's normally only sold to racers.

How much rake? Depends on the boat and sails. Normally between 1 and 15 degrees. Start at 5 and shift it around to eliminate healm preassure. A little weather helm is a good thing on a cruising boat, but may be dialed out or minimized for racing.

How much headstay tensions? Depends on the cut of the head sail. Some need more curve than others in the same conditions. This is purely a sailmakers question. The tighter it is the lower the drag but the lower the power available. It also narrows the groove so the sail design should take into account the skill of the driver.

And there are real downsides to overly tight shrouds. Like ripping the entire deck off the boat (rare), or deforming the hull (quite common). Which is why you want the shrouds to me as loose as possible in the current conditions.

As for why shrouds tend to come in at between 15-20% their MBL... That's because of the 5:1 safety factor that most designers use for standing rigging. When you design a rig and get an expected max load of X, designers then tend to use a wire with a strength of 5X. That is NOT supposed to be the normal tuning number.
Touché; but what you just posted is entirely WRONG for every boat other than J35 and other boats MODIFIED and optimized for specific racing venues!!!!

Most coastal boats are designed at an overall 200% (2X) safety factor, 'blue water' boats @ 300+% (3+X) SF, 'inshore' boat @150% (1.5X) SF .... not 500% (5X) unless specifically designed for 'other'.
Do your calculations! Back-calculate even just the data in the Seldén, etc. manual and see what you get - FS=3 as a maximum - simple!!!!!
The simple FS=3 equates to a maximum stress level of 1/3UTS .... coincidently the exact same threshold as the common and quite very important 'endurance limit' (fatigue) for the common 300 stainless components used is virtually ALL 'common' rigging.
What I gave is for plain vanilla boats, used by non-racers. Adding to the discussion with RACING 'outliers' is really quite distractive and confusing to those who sail 'plain vanillas' and who only want to adjust their rig to COMMON plain vanilla accepted standards and to safely sail in normal conditions without 'busting' a rig. Sorry, but your 'additions' are inappropriate for THIS discussion - IMO.
<grin>
Ill patiently await your 'retraction'. :)
 
#26 ·
Both Selden and CS have written relevant manuals on tuning the OP's mast, I suggest using these manuals as your references:
http://www.seldenmast.com/files/1456145028/595-540-E.pdf
http://www.csyachtswest.org/uploads/1/9/0/2/19025235/cs36_manual.pdf

FWIW neither of the vendor manuals mention anything about Loos gauges, nor does the rigging section of my current Pearson manual. You do see serious one-design racers using those gauges to adjust their rigs, but I dont think they have any value for racer/cruiser rigs whether just cruising or racing or doing both. I have one in my tool box that hasn't been touched since I sold my R19 some twenty-five years ago.
 
#29 ·
the Selden manual does show the use of a tension gauge, though not Loos but it does measure tension.
For me the loos is a very fast way to adjust the rig for different tunes from light to heavy conditions. On my rig it is very easy to tighten the upper shrouds to much trying to get enough forestay tension when adjusting the luff curve. so for me the loos is a good way to make sure I don't over tighten any wire.
 
#27 ·
Rich,

I don't know of a boat in the world that uses a 2:1 safety factor on standing rigging. Heck I don't know of anywhere that's 2:1 would be appropriate on anything, let alone a mission critical system like the rig.

And racers are far more likely to use a LOWER safety factor than cruisers. Not the other way around. Racers are more fault tolerant, and generally are willing to shave weight at the risk of damage than cruisers are.

Tuning the rig on a J-35', or an Irwin 54' is exactly the same process, with exactly the same goals in mind. The only difference is how much a racer is willing to fiddle with it on a daily basis. For most cruisers setting it for 20kn and made do with the downsides is a perfectly reasonable compromise. It's what we did, it's what I do now on the cruising boat (ok I tune it every season change, but I am crazy).

Choosing to have a poorly tuned rig is one thing, I knowingly accept the compromises for less fiddling. I am think this is a perfectly reasonable choice. But good choices require good information, which is what I was providing.
 
#30 · (Edited)
[/U]
Rich,

I don't know of a boat in the world that uses a 2:1 safety factor on standing rigging. Heck I don't know of anywhere that's 2:1 would be appropriate on anything, let alone a mission critical system like the rig.

And racers are far more likely to use a LOWER safety factor than cruisers. Not the other way around. Racers are more fault tolerant, and generally are willing to shave weight at the risk of damage than cruisers are.

Tuning the rig on a J-35', or an Irwin 54' is exactly the same process, with exactly the same goals in mind. The only difference is how much a racer is willing to fiddle with it on a daily basis. For most cruisers setting it for 20kn and made do with the downsides is a perfectly reasonable compromise. It's what we did, it's what I do now on the cruising boat (ok I tune it every season change, but I am crazy).

Choosing to have a poorly tuned rig is one thing, I knowingly accept the compromises for less fiddling. I am think this is a perfectly reasonable choice. But good choices require good information, which is what I was providing.
FS=1.5 for lightly loaded static applications and w/ little risk/history of failure; FS=2 is the 'classic' for 'normal' usage in almost ALL 'normal' and 'predictable' stress strain applications in the entire world, including common pressure vessels;
FS=3 is for 'severe' service: ie. cranes, gantries, and other things that can fall down and hurt, etc a lot of people. Cantilevered structures (masts) are included in this FS=3, sometimes at FS=4.
FS=4 and above is for hazardous/lethal service .... a LOT of people WILL be hurt/harmed/killed.
Standard civil engineering (stress/strain) 'rules of thumb'. If there are failures at those levels of FS, then either total re-engineering or 'bump up' the FS levels. Safety Factors are applied to (hopefully) take care of unexpected/unforseen stresses, during intended operation and usage.
Edit/Add - interestingly these safety factors arose from actuarial data (of what worked and and what failed) from the insurance underwriters.

As far as generalized tuning/tensioning .... the 12-15% remains a core 'starting guide' --- been this way since they started making (common) aluminum spars. The differences, requiring fine tuning by the sailor, are from the varying and different 'intercept angles' that the rigging makes with the spars (all typically in the range of 10-12°), boat model/geometry dependent. For precision and so that stress anomalies are not encountered, the careful evaluation of 'free body' diagrams (by engineers and riggers) so that the desired applied stress TO the spar is controlled, so that the 'horizontal components (x direction, when the mast is straight up) is EQUAL for all attachment points AND that the (compression) stresses induced along the long (y) axis of the spar doesn't become so large that buckling failure is when not if; simply put - at least hold the mast in near perfect column during its usage. The 'balance' is ALL components are working at 'equal' stress values, especially at the attachments - all the 'balanced' applied stress keeps the spar straight and not induce bending.

Ain't any deeper 'fundamentals' than that .... and no matter the safety factors involved, the material strengths etc., nor the material choices.
To wit, the thin sectioned mast must remain 'straight' (side to side) so that buckling failure is avoided; and, that the stresses applied to the whole 'system' do not exceed plastic deformation and remain 'under' the fatigue endurance limit. The 'user' corrects for tension needed because those attachment/intercept rigging 'angles' to the mast may be different than the standard 10-12°. Simple.

This is NOT, nor should be, a discussion of 'pushed' nor optimized designs used for racing --- a totally different world and with a totally different accepted amount and degree of structural failures. Think of the AC boat "Young America" breaking in HALF and sinking during a roll tack, etc., ..... probably all started with a rig failure, probably 'too tight' rigging and 'reduced safety factors' to save weight.

Repeat - the function of mast/rig tuning is
1. Keep that mast 'straight' at 'normal' angles of heel, at normal wind strengths - NO buckling failure,
2. provide a consistent 'platform' by which one can 'shape' a headsail.

FWIW - I make the 'wild-guess' that you're arriving at FS=5 is probably from the replacement of stainless steel components with Ti (average) alloy components. SS @ YS=~30ksi, Ti @YS=~60-70+++ ksi. and because you 'can' use thinner cross section TiA materials to do the exact same job. Just an unimportant guess.

regards ;-)
 
#31 · (Edited)
This is getting pretty silly. OP and most of us are cruisers. Many of us tune our rigs once or twice a year. Do a detailed inspection once or twice a year and just before a significant passage or if we suspect something is going on. Maybe resulting in another tuning.

If we lose a degree or two pointing no biggie. We are not going to do a detailed re-tune underway in a blow. We are not going to retune for light air. Maybe use different vang, traveler and backstay but that's going to be the extent of changes. We'll "tune" the sails as frequently as we can and needed but not the rig. We are not going to lose precious family or cruising time rig tuning incessantly.

We are very concerned about losing a rig. We are very concerned about hurting our boats.
N was detailed in describing his sailing program and a delightful program it is.
Can we redirect this thread to his concerns. If digressions are to occur can they relate to average cruisers with Al masts and ss 1x19 wire who might see nasty weather on occasion. Discussion relating to bendy fractionals, squarehead or other racing rigs is of interest but perhaps better placed on another thread.

This thread interests me. I'm insecure about this subject. You guys have a lot of knowledge. Please teach us stuff we can use.
Thanks gents.
 
#35 ·
I read and saved the Selden tuning rig and will print portions of it for my on-board manual. On thing I found particularly interesting is the fact that the backstay being at a different angle than the headstay that tension on the head is higher than the back because of these different angles created by the mast being forward. Since there is a sail pulling on the head and most have furlers then we cant measure the forces they have to be calculated and factored in. I think that's why the 15% is used because its more like 20% on the head and 30% (static) is the limit we want to use. I am particularly interested in this because I want to add a backstay adjuster. Without digressing into the Racing world (where I spend 3/4 of my time) many (some) cruisers use a backstay adjuster and I think this is important to note.

The keep it simple cruising rig will align the column and set the backstay to whatever compromise you choose for your Boat and conditions
I can see where I sail having a summer setting and a spring/fall setting where the winds are higher and heavier maybe being an option.
One down side to my rig is the backstay chainplate is so low down the transom you can't get to the turnbuckle without standing in the dingy and after balancing out the turnbuckle I can't get more than about 13% on the backstay which while perfect for one particular wind speed easily gets too loose when the wind builds.
 
#37 · (Edited)
Since there is a sail pulling on the head and most have furlers then we cant measure the forces they have to be calculated and factored in. I think that's why the 15% is used because its more like 20% on the head and 30% (static) is the limit we want to use. I am particularly interested in this because I want to add a backstay adjuster. Without digressing into the Racing world (where I spend 3/4 of my time) many (some) cruisers use a backstay adjuster and I think this is important to note.
Just for 'ships and giggles', with no clients on the phone this AM, I did a simplified 'statics' forestay/backstay load calculation for your CS30. So if this 'is' your boat, and my 'rithmetic' is correct - enjoy.
FWIW - I included the 30% value, which is the load% at where ductile failure (permanent stretch) and rapid fatigue of the components 'can' begin to rapidly occur -- so when sailing in the high wind ranges, just tie your loos gage to the backstay and if you're 'bouncing' close to 25% backstay tension ... do 'something' to reduce the stress:





** recommended NOT to exceed
 
#36 ·
When I overhauled my rig, it has triple spreaders and quite bendy, I pulled the masthead over by winching as hard as I could on a spinnaker halyard extended out to a distant mooring. The stern was tied to another. Worked great. No need to go sailing. Heal over, sight the mast track. Ease off. Adjust both sides the same. Repeat a couple of times. Quiet tropical lagoon. No fiddling with the Loos gauge.
 
#39 · (Edited)
Good point/observation.
They 'can' be, but are not usually so; since, they 'react' in direct-opposition 'against' one another and at approximately 'close' / approximately similar intercept angles.

So, if different diameters, same material, ..... make your (math 'ratio') corrections based on the AWG (wire diameter) gage thats built into the side of your Loos gage OR the published Ultimate Tensile Strength of the wire in pounds/kilograms(f), etc., etc.
 
#40 ·
Head stays are sized larger then the backstay because the wire and fitting take the most abuse of any wire on the boat. they take a side load from the headsail. They can be nicked and scratched from a furler or hanks. spinnaker poles can put a large side load on the stay also. they take more shock load because they are curve during sail and if a wave causes the rig to jolt the stay will be snapped from curve to straight and back to curved in a split second.
 
#42 · (Edited)
I strongly disagree.
When one 'up-sizes' a headstay or forestay, the catenary curve 'sag' becomes more pronounced hence the headsail has to be re-cut it luff 'shape' to match the increased 'fullness' of the sag of the wire; the wire now operating at less tension to provide the SAME horizontal force component at the top of the mast .... in opposition to a normally tensioned backstay. When you 'upsize', you most certainly do not up-size the %tension!!! The inbuilt 'factor of safety' takes care of all the impact and other unforeseen loading possibilities.
Further, (Norway type) piston hanks are most always 'softer' silicon-bronze, or an engineering plastic such as acetal or delrin for smaller sails and not much with which to nick or abrade stainless wire, etc.. So too are roller furler bearings, etc. that 'mate' with the wire.

So, (in this CS30 example) to have the same reaction forces acting at the top of the mast using 3/16" wire instead of 1/4"(?) wire one would have to load up that 3/16" wire to approx. 21% strain, to equate to a 15% forestay tension ... leaving not much 'wiggle room' as that 3/16" backstay wire would be 'maxed out' with only 9% additional available stress until you exceed the 'fatigue endurance limit' - ~30% UTS for '300 series stainless'. But this too, is NOT the answer !!!!

The probable reason one sees smaller diameter wire on 'some' backstays - Mast location!
For different sized backstay vs. forestay wires ... the 'classic' sloop design has some advantages with the typical mast located at ~30% of LOA. You then 'double' the intercept angle that the backstay wire makes with the mast in comparison to the forestay wire angle, and that mast position 'allows' smaller wire simply because the trigonometric SINE of the angle that the backstay makes with the mast is much larger; hence there is more Force (in the horizontal plane) provided by 'larger' intercept angle to mast by the backstay - a functional advantage due to the 'trigonometry' of the mast being 'well forward'. With a 'doubled angle' a smaller wire can certainly provide the 'needed' horizontal FORCE component in reaction to the horizontal Force component from the forestay .... but that mast has to be well forward of the middle of that boat, like at about ~30% LOA. The 'fractional' rig would be the ideal configuration for use of a smaller backstay dia. than its forestay dia.

Aint so for albrazzi's CS30 which has its mast at ~42% LOA, backstay @ 20° and forestay @ 17° (to the mast) and that's why I strongly suspected that albrazzi's backstay and forestay wires are the exact same size. If his mast would have been at 30% LOA, backstay at 24°, forestay at 14° ... indeed he'd only need half the wire size/area (load capacity) of his backstay to carry the same load that the mast has at -42% LOA ;-)

Hell, if one could arrange so that the backstay would be totally parallel to the horizon, one could use base guitar or piano strings as you only need a few hundred pounds of horizontal force to hold the mast in place (the CS30 only needs about 350lb. of horizontal force component from its backstay, but its 1/4" wire is good for ~7500lb. !!! Did Someone want to discuss 'jack lines'? )

Hope this helps ;-)
 
#46 ·
Hi RichH: I realize this post is well over a year old so not sure if this will get a response but here's hoping. I also have a CS30, but I'm new to the boat and sailing. I sailed last season after buying the boat from a very diligent and knowledgable sailor so I didn't change the rigging tensions much (when I stepped the mast I used the tape markings he had put on the turnbuckles to set the tension.)

Would you mind 'unpacking' this analysis a bit more and explaining how it can be applied? (also i'm no engineer and it's been a while since I did any algebra or calculus ...) I can confirm that my forestay and backstay are the same diameter.
 
#48 ·
Hi RichH: I realize this post is well over a year old so not sure if this will get a response but here's hoping. I also have a CS30, but I'm new to the boat and sailing. I sailed last season after buying the boat from a very diligent and knowledgable sailor so I didn't change the rigging tensions much (when I stepped the mast I used the tape markings he had put on the turnbuckles to set the tension.)

Would you mind 'unpacking' this analysis a bit more and explaining how it can be applied? (also i'm no engineer and it's been a while since I did any algebra or calculus ...) I can confirm that my forestay and backstay are the same diameter.
Justin welcome to the Forum. Lots of very knowledgeable people here, and I lean on them regularly. Hope you are enjoying your Boat. Im curious how long have you had her? I'm 3 years in and still looking for the right combination in certain conditions.
 
#47 · (Edited)
keep in mind that all the math and tension stuff is fine but what you are looking to do with the turnbuckles is to put the mast in the center the boat with the mast bent or not bent, which ever makes the boat sail the best under the conditions that you are sailing in. forestay sets the mast rake, backstay sets the fore sail luff curve. the upper shrouds set the mast in the center and in column, lower shrouds can do several things depending on the type of rig. Rig tensions or measurements of the rig are only good to pre set the rig so you can go sailing and adjust the rig to the boat and sails while under a sailing load.
the sails are held in position by the mast, you want the sails set to the best shape and position to drive the boat forward. so you use the turnbuckles to to adjust the mast position and shape the sails. the tension on the wires is a result of these adjustments when the rig is in a static state ( not sailing ). the tension measurements are useful as a reference for pre setting up a rig after mast removal or wire replacement.
 
#49 ·
Thanks for this ... it leads me to another question which is possibly very petty but for me an issue. How to deal with the turnbuckles? Mine are secured from unwanted turning by key-ring-like metal parts that don't really seem to fit properly. It's almost impossible to remove them without a pair of pliers and totally destroying them. Once I'm out on the water I don't really feel much like fighting with them tbh. Do some rigs have an easier system for adjustment while sailing?
 
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