How can I set stay tension without a meter ?

[tasdevil]

I've just about finished the refit of my Oday 22 , put the mast up this morning.
Can anyone suggest a relatively simple method of setting correct stay tension without the use of an expensive meter ?

 

[Timo42]

Use a cheap gauge, a Loos gauge for small boat rigging goes for about $65.
Tim

 

[RichH]

Easy with an accurate steel measuring tape. This method will work for ALL sizes of wire and regardless of the wire diameter. The 'target' tension % for most sloops is 15%. The following is a fairly precise method that only needs a 'steel tape ruler' some plastic tape and your brain.

Unload the tension (slack off) then measure and accurately place 2 marks on each shroud at precisely 79.0" (2.0m) apart.
5% tension = .04" (1mm) stretch .... (per 79")
10% tension = .08 (2mm) stretch .... (per 79")
15% tension = .12" (3mm) stretch = approx. 1/8" ..... (per 79")
Cant be any simpler and you dont need a rigging gage only a steel tape measure.

15% is the 'benchmark' tension for most rigging on sloops.
Measure/Mark all the shrouds, etc. when 'unloaded' (~0% tension)
Bring up the tension in 5% increments (ie. all shrouds AT 5% tension), then ALL at 10% tension, then ALL at 15% .... so that the final 'stretch' results in the 79.0" distance ... stretched to 79.12" = approx. 79-1/8" for 15% tension.
Works on ALL stainless steel 'wire' rigging and no matter what the diameter.

Once you have 15%, take the boat out in ~15kts. and while beating (heeled), put your eyeball next to the mast slug track and 'look up'. Then make final corrections so that the mast is 'dead straight' while sailing in ~15kts. of wind when on a beat.


Other.
The above does not include 'prebending' a mast. Masts with backstays and with a single set of spreaders should have 3/4" forward bow somewhere near the 'middle' of the mast; if multiple spreaders then 1/2" forward bow per spreader set - 1" forward bow if mast has 2 sets of spreaders, etc.
Method: once rig is at 15% tension, loosen aft lower shrouds (usually attach to the mast AT the spreaders) and tighten forward lowers until you 'guestimate' the 3/4" forward 'bow', then retighten aft lowers, etc. until you get the ~3/4" 'forward bow' in the mast. Prebending will radically increase the stiffness of the mast and will prevent 'mast pumping' ... plus will tend to 'flatten' the mainsail a wee bit (your sailmaker already cut the sail for this expected prebend, so if you dont prebend the mast to match the sail you will have a bit more maximum draft than the design - not a big deal if you are only 'cruising'.). Prebending compensates for the amount of bend that is imparted to the mast from the sail when the wind is at approx. 15-18kts --- and the force from the wind-loaded sail on the mast tends to put a 'reverse bow' into the mast (which 'powers-up' the sail). If pre-bending is confusing ... simply ignore this.

Hope this helps.

 

[Gail R]

The skipper of our boat never uses a meter or guage. He does it strictly by look and feel. Of course, we've had the same boat for more than 12 years so it has become second nature.

 

[Stu Jackson]

Without a gauge and without measuring tools:

1. Set it up at the dock so it's straight

2. Go sailing, if leeward shrouds are loose, tighten them halfway, tack, tighten the other side to even them out.

3. Check back at dock or when in a position to check step one again. Repeat 1 & 2 & 3 until you're finished.

I think this is what Gail suggested her skipper does.

It works.

 

[Ross]

Without a gauge and without measuring tools:

1. Set it up at the dock so it's straight

2. Go sailing, if leeward shrouds are loose, tighten them halfway, tack, tighten the other side to even them out.

3. Check back at dock or when in a position to check step one again. Repeat 1 & 2 & 3 until you're finished.

I think this is what Gail suggested her skipper does.

It works.

Just to add one step here : Learn what the shrouds "feel" like when they are properly tight.

 

[tasdevil]

Thanks for the advice; I'm doing the " trial by sailing " method just to get started, then I'll dock her and use the steel tape - just 3mm eh ? OK.. many thanx........Robin.

 

[RichH]

A sailmaker cuts the shape of the leading edge of a sail 'expecting' that the shroud is at ~15% tension. If youre not close to ~15% (forestay) tension the 'shape' that the foresail take will be 'off' .... less than 15% the position/location of maximum draft will be too far aft = excess heeling and the boat will begin to 'skid off to leeward'; greater than 15% and the draft will be too far forward = the sail will 'luff' too easily (unstable) and have reduced speed/power.

 

[RichH]

Just to add one step here : Learn what the shrouds "feel" like when they are properly tight.

OK, explain to a novice what a properly tuned shroud 'feels like'. How do you explain the relationship of the way a sail 'sets & shapes' according to how a shroud 'feels'. Inquiring minds would like to know. <grin>

 

[Ross]

OK, explain to a novice what a properly tuned shroud 'feels like'. How do you explain the relationship of the way a sail 'sets & shapes' according to how a shroud 'feels'. Inquiring minds would like to know. <grin>

In the same manner that you teach them what a sharp knife edge feels like. Unless your student is brain dead it should be able to decern the difference between a taut shroud and a slack one.

 

[Stu Jackson]

Here's how again...

In the same manner that you teach them what a sharp knife edge feels like. Unless your student is brain dead it should be able to decern the difference between a taut shroud and a slack one.

To back up my earlier post, please read para 4.1.2 starting on PDF page 19 here: http://www.c34.org/manuals/1988/1988-C34-Owners.pdf

While I've been (accused of and have been sometimes) guilty of makin' stuff up, this ain't one of 'em.

It's also how I learned how to do it and I haven't even thought about asking Santa for a Loos gauge in 32 years. Since he didn't get me one 33 years ago, I didn't bother goin' there again...

 

[RichH]

In the same manner that you teach them what a sharp knife edge feels like. Unless your student is brain dead it should be able to decern the difference between a taut shroud and a slack one.

OK I see your point of view. You let them cut a finger on a sharp knife and hope that they remember what it feels like .... but still offer NO reason of 'why' the knife should be sharp or dull, only thats 'the way you do it, so it has to be right'.

Is there a limit to 'taut' so that you dont have to explain what happens when a mast butt goes through a bilge/floor into the ocean because the 'taut' feeling is actually too tight, or when 'taut' pulls a chainplate loose from its knee? Im sure one of the brain dead would realize taut that damages the boat or too loose that allow the rig to go overboard ... but Im not sure from your description what your implication of 'just right' would be.

 

[Don12364]

DIY Shroud Tension Measurement

Basic physics.
* Find distance between clevis pin on lower shroud at deck level.
(Easily done by pulling tape measure end up mast with main halyard).
* Put a tape marker on shroud a suitable distance above this (in my case 78.6").
* Place a rod, stick, batten or piece of 1" sq wood against the mast and out horizontally to the tape marker.
* Mark the stick with a pencil where it touches the shroud.
* Make a second mark 1" inboard towards the mast.
* Get a spring balance or fishing scale and pull the shroud tape marker inboard until it comes to the inner mark.
* Do the arithmetic or use my spreadsheet attached herewith.

I have been doing this for years and this method does not suffer the accuracy loss of the Loos gauge where it tries to put a double bend into the wire and if the rigging is stiff or made of solid rod then an error is introduced.

Do the forestay likewise if there is no luff spar.

Have fun

At the end of the day you probably won't get better than 10% accuracy anyway.

Shucks this system will only allow pictures or text uploads and my Excel file is neither.
Will have to ask Phil how to do this and re-post later.
Update:- Phil has put the spreadsheet on
http://forums.sbo.sailboatowners.com/downloads.php?do=file&id=34
Have fun.

 

[Ross]

OK I see your point of view. You let them cut a finger on a sharp knife and hope that they remember what it feels like .... but still offer NO reason of 'why' the knife should be sharp or dull, only thats 'the way you do it, so it has to be right'.

Is there a limit to 'taut' so that you dont have to explain what happens when a mast butt goes through a bilge/floor into the ocean because the 'taut' feeling is actually too tight, or when 'taut' pulls a chainplate loose from its knee? Im sure one of the brain dead would realize taut that damages the boat or too loose that allow the rig to go overboard ... but Im not sure from your description what your implication of 'just right' would be.

I presume then that whenever you walk around your deck and check your standing rigging you use a quantitative measuring devise and don't rely on a simple pull on each part as you make your rounds. OTOH I bet you could tell by feel if someone loosened a turnbuckle just one full turn on your upper shroud. When you sharpen your knife how do you check the edge? I check by feel and I don't lacerate my fingers. When I have it quite sharp then I move onto the finer stones and check the edge against the hair on my arm. I could use a magnifier and then a microscope and have done so for some purposes.

 

[jibes138]

Tuning the rig

Why not try one of these musical instrument tuners to tune a rig based on the tone of the wire when plucked? I have never done this but I think it might work. A guitar, or mandolin string for example is tightened until it produces the right frequency of vibration. If you tune your rig then baseline the frequency it gives off you should be able to tune it to this frequency and get it almost exactly the same every time. Not sure if the tuners will work at a low frequency but it is worth a shot. I have a tuner and will try it. Not for a couple weeks though.

 

[tommays]

The guage cost is LOW and while you can feel it i am unsure once you get to 8% or10 % how you feel it at 15 % and not 18 %

You can also put a tape measure on uppers and lowers and measure OR just use the guage which they also make for ROD


I know i know you dont use torque wrenchs or micrometers becasue you can tell

 

[RichH]

I presume then that whenever you walk around your deck and check your standing rigging you use a quantitative measuring devise and don't rely on a simple pull on each part as you make your rounds. OTOH I bet you could tell by feel if someone loosened a turnbuckle just one full turn on your upper shroud. When you sharpen your knife how do you check the edge? I check by feel and I don't lacerate my fingers. When I have it quite sharp then I move onto the finer stones and check the edge against the hair on my arm. I could use a magnifier and then a microscope and have done so for some purposes.

No not at all.
I tune my rig according to the boats SAILING characteristics for the day, watching especially the forestay curve ('luff hollow') when under sail load and to arrive at the best pointing angle. One of my boats has on-the-fly-rig-tuning ('all' the wires and not just the backstay), I adjust solely to the boats reaction to the SAILS vs. wind ... and the 'tune' may be different every time I go out in accord to different wind and seastate conditions - if the mast is not in 'perfect column', I dont care, especially if I find that that day's 'tune' gives me the best performance possible. I dont follow rigid rules that dont apply to sail optimization ... and I used to 'win/place' most races when I was an active racer probably because of this optimization; now I arrive at far cruising destinations much faster than those who follow non-applicable 'rules' and 'feelings' and 'tune' their rig maybe once a year, ... maybe but usually not at all.
The mast/rigging system is only to support the sails correctly, not to follow some esoteric non-contributory 'rules' that dont apply to sail performance - that have over the years shown the rig tension (on most boats) at a quantifiable ~15% gage tension to be equivalent to the best sail shape and to match what the sail design/cut requires to be at optimum. That 15% basic rig tension is what a good sailmaker is 'expecting' for proper sail cut (curves) when designing a sail. Examine Donalex' post more carefully, he implies a certain 'elasticity' vs. tension (vs. perpendicular deflection) ... and that is correctly corelated to sail shape and sail performance and corelates to 'numbers'. Too loose rigging and sails will be 'powered-up', too tight and sail becomes unstable and with poor performance; sails are not designed to set up by qualitative 'feelings' as there are quantitative 'numbers' (from instruments or other corelation) to be followed. One should correlate rig tension to its ultimate purpose - correct sail shape and sail performance - not 'feelings'.

I sharpen my knives when the performance of the cut seems to be 'off'. I then hold the knife to the whetstone at an ~15-18 degree angle ... experience (of those who sharpen knives daily) shows that to be the best angle for best sharpness and longevity of the edge. I dont feel the edge after sharpening, honing and 'stropping' as I know it will be more than sharp enough to shave with although I do sometimes test vs. a thin sheet of paper ... and that correlates to the edge's 'performance'.

best regards