Rig tuning

[Zen]

Do you do it yourself or have others do it?
How often?
If you do it, do you just guess or use a tension gauge?

[krissteyn]

Interesting topic - I generally de-tune my rig as I dont race (except the wind) and my cost-of-replacement is a big factor.

But steps I usually take :-
1. ensure mast is straight - measure the halyard to port/starboard - within 1" makes me happy.
2. check mast rake against main sail - I just think if it looks ok , it probably is - could check manufacturers specs I suppose...
3. If you think the shrouds are too tight, They probably are ! I have seen many an over-tightened rig that caused hull damage. Avoid the "banana" effect.
If the mast flops visibly - tighten up...
4. If on a reach the lazy shrouds are not slightly floppy - too tight.
5. You can make a very easy simple rig tension measurer with a spring balance and a tape measure. With a bit of experience - I dont bother - just "twang" it.

If you do it all yourself and check all the turnbuckles and other connections, you will know your boat better.  It is not rocket science.

special tip : I always use lanolin ($15/qt from the drugstore) on my turnbuckles and shackles - The threads never sieze. Never use wd40 without putting proper grease (or similar) in afterwards - I keep wd40 only for emergencies.

[CharlieJ]

Sounds good except your point 4. You lee shrouds should NEVER be "floppy" A little loose maybe, slightly slack, maybe, but NEVER floppy.

I agree that there is no need to over tension, but if you have enough slack that the leeward shrouds are at all sloppy, you can subject your rig to high stress loading from slamming into seas. That slackness would let the mast move enough to slam a small amount, which can overstress fittings.

So have them snug, but just tight enough to not be "sloppy"

On the mast rake- if the boat has proper helm with the headsail you normally use, then the rake is pretty much correct. Expect the helm pressure to change with a larger or smaller jib- you CAN'T perfectly balance the helm ( for weather helm) for all sails, without changing the rake.

[starcrest]

I prefer to let the rig breath.never too tight------not too loose-----I was always checking rig tension ---even in 35 kt  winds---it was never too tight.no matter how much standing rigging---that stick can and will fail if you ask it to.

[kingfish]

Hello all,
here is some tips on tuning your rig. I do have to say "thanks to gordmay on the crusiers forum for this research"  But I figure that this is worth sharing.


The goal of rig tuning is to have a mast that's straight athwartships. This will help you gain control of sail shape and achieve proper helm balance in a variety of conditions. Most importantly, the resulting mast tune will not impart any excessive strain or loads on the spars, rigging, or the structure of the boat. The basic adjustments for tuning
a rig are actually straightforward and not the mystery that some people might make them out to be.

To begin, we should define the difference between fore-and-aft tune and transverse tune. Fore-and-aft tune basically refers to rake and mast bend. Transverse or lateral tune refers to setting the mast up straight sideways and setting up the uppers to minimize
lean.

Fore-and-Aft Tune

Let's begin with rake, which is determined by headstay length. Rake affects helm by moving the center of effort of the sails relative to the center of lateral resistance. A longer headstay gives more rake which gives you more weather helm.

A starting point for arriving at the correct rake is to measure the designed rake of the sailplan. A typical 40' boat would have about 15"-18" of rake. To calculate rake, hang a plumb bob from the main halyard and measure from the aft side of the mast along the cabin top to the plumb bob. This should be done with the backstay tensioned at about 60%. The actual amount of rake you end up with may vary depending on the normal conditions you sail in and may be a compromise between what's optimum in light air vs. heavy air.

The second aspect of fore-and-aft tune is mast bend. A certain amount of mast bend is desirable. Mast bend is determined by the relationship between the positions of the masthead, deck partners, and mast step. If we've decided on the proper rake, then the masthead position is fixed and we have the deck partners and mast butt positions to adjust to induce mast bend. By either moving the mast forward in the deck collar or moving the mast butt aft in the step, we can induce some bend into the rig.

Another factor that can affect mast bend is the angle at which the butt of the mast is cut off. If the mast is resting on its forward or aft face, the resulting moment will have a major effect on bend. We normally radius the butt of the mast so that the spar will bear near the center axis of the section, thereby minimizing the bending moment regardless of the angle of the spar to the step.

Other factors that control mast bend are double lower shrouds, babystays, and inner forestays. Double lower shrouds can be tuned to increase or limit mast bend. Babystays are typically used on boats with single, in-line lowers and pull the rig forward down low in the same way as forward lowers. Inner forestays with a staysail can put a large bending moment in the spar and are usually opposed with running backstays or aft intermediates.

Spreader sweep is also a big factor in mast bend. This factor, however, is a design feature of the spar system, and not a variable as most spreaders are fixed rigidly to the spar. Aft-swept spreaders will facilitate some mast bend and in-line spreaders will restrict mast bend.

So what does all this talk of mast bend mean? Why is it important? A certain amount of bend is necessary as it makes the spar more stable and less likely to pump in a breeze. Most mainsails require a certain amount of mast bend to set properly, and, as the breeze increases, the combination of more backstay tension and more bend will flatten the main. This will keep the boat standing more upright and ease the helm.

Another consideration is headstay sag. Controlling the amount of headstay sag with an adjustable backstay will allow you to optimize the shape of the genoa through a range of wind strengths. With an adjustable backstay, particularly an hydraulic backstay, it's extremely important to establish a maximum backstay load as well as some lower reference points. A good upper limit is 30-40% of the breaking strength of the backstay wire or rod. This allows some margin of error in the system in case of shock loading.

Lateral Tune

Lateral tuning is probably the most important tuning process and is often the most confusing, particularly with multiple-spreader rigs. Keeping the mast straight athwartships over a range of wind strengths and sea conditions is essential to keeping the rig in the
boat.

In addition to keeping the spar straight or in column, we're interested in having the upper shrouds tight enough to minimize how far the mast leans over the side when sailing upwind. This will help reduce weather helm. Although the effect is small, most boats have too much weather helm in fresh air and it's important to minimize it any way we can.

The first step in lateral tuning is to center the mast in the boat. The backstay and upper shrouds should be relatively loose at this point to minimize bending the rig. Pull a steel tape up on the main halyard and measure to the chainplate or to a point on the gunwale on each side. Adjust the upper shrouds until you get the same readings port
and starboard.

At this point, check to see that the spar is firmly secured in the partners with wood wedges or preferably hard rubber wedges. They should be very tight so the mast cannot work or move at the deck. Spartite is the most efficient and effective means of securing the mast in the partners, and is required for carbon spars.

The next step is to tension the upper shrouds at the dock. Make sure the turnbuckle threads are lubricated to prevent damage from galling. A dry lubricant is preferred, such as Rig Lube or Bike Aid. The upper shrouds should be as tight as you can get them with a 10" crescent wrench. Don't use a larger wrench or an extender as you can damage the threads. Additional tensioning must be done under sail. The lowers and intermediates should be fairly loose, or just tight enough to keep the mast straight.

If the boat has discontinuous rigging, it's important that the diagonals be very loose before tensioning the verticals. They will tension as the verticals are tensioned.

Now we're ready to further tension the upper shrouds under sail. In about 15 knots of breeze, put up the main and begin by tightening the leeward upper shroud. Keep track of the number of turns. While tacking back and forth, continue to tighten the turnbuckles on each leeward side until the uppers are snug with the boat heeled at 20 degrees. Don't worry about the lowers or intermediates at this stage; the object is to fully tension the uppers.

Another method for tensioning the uppers without sailing is to heel the boat over at the dock using a halyard. The halyard must lead through a fair lead lock at the masthead and have a clear lead directly abeam. This method saves time and also allows adjustment of the lowers and intermediates—but exercise caution tuning this way. Now that we have the target tension on the upper shrouds, we're ready to straighten the mast with the lowers and intermediates. With a single-spreader rig, simply tension the lowers until the mast appears straight when sighting up the sail track or groove. This should be done under full sail in 15 knots of breeze. If the boat has double lowers, generally the forward lower will be tighter than the aft lower. The forward lower does most of the work supporting the mast laterally. The aft lower acts primarily to limit mast bend as the backstay is tightened in heavy air. At the dock, the lowers will be a good deal looser than the uppers. Under sail, the lowers on the leeward side will flop around a lot, and it's a good idea to use a shock cord lashing to take out the slack and prevent fatigue.

Multiple spreader rigs are more complex, but the tuning process is essentially the same. After the uppers are secured, start with the D1 shrouds (lowers). These should betight enough to prevent sagging to leeward at the first spreader in 18 knots of breeze.

The next shroud up in a double-spreader rig would be the D2 or the intermediate. The adjustment of the D2 is very important as it has a large effect on the transverse bend in the upper part of the spar. It should be set up fairly loose in the beginning of the tuning process and gradually tightened to eliminate sag at the second spreader.

If the D2 is too tight, the upper spreader is pulled to windward and the masthead is relatively to leeward. This situation is undesirable as the angle between the upper shroud and the spar at the upper tang is reduced. Many people view that as the tip falling off, with the solution to tighten the uppers, when the correct adjustment is to ease the D2. The final fine-tuning adjustments of the diagonal shrouds should be done at 20-30 degrees of heel, as the adjustment is relatively insensitive at low loads.


Essential Rig Tuning Manual: http://www.hallspars.com/pdfs/HallRigTuneManual.pdf
Care of Carbon, Prebend, Rig Inspection, and Rig Tuning all together in pdf format.

Rigging Inspections Checks - from Sailing Supply
http://www.sailingsupply.com/articl...ion_checks.html

How to Sail Fast - Rig Tuning - by Bob Sterne
http://c_r_y_a.tripod.com/Sterne%20How%20to.htm

RIG TUNING GUIDELINES - from Z-Spar
http://www.zsparsuk.com/rigtune.htm
http://www.usspars.com/pdfs/rigging.pdf

[krissteyn]

NEVER FLOPPY ?   I have sailed on many a boat where the lazy turnbuckles are at 45 degrees from the deck ! This on a "tuned-for-crossing-atlantic" delivery.

Perhaps floppy is a generic term with individual understanding.  One mans floppy is another s    just off snug...

Depends on the age of the boat, hull construction and wind strength/stress (90deg to hull)

good posting.... always happy to learn from others...

[Pixie Dust]

Kingfish - Great post!  Karma to ya!

[Captain Smollett]

Perhaps floppy is a generic term with individual understanding.  One mans floppy is another s    just off snug...

Just to reiterate what CJ said:

The problem with "floppy" is shock loading.  If the mast can move an appreciable distance before the wire takes the strain, the wire, and all fittings, become shock loaded.  The chance of failure is MUCH MUCH higher.  It does not have to be the wire that fails, but any fitting in the chain.

I would not think you should see noticable displacement of the turnbuckle out of 'true' for a properly adjusted lee shroud.

If you saw floppy shrouds on an ocean going vessel without a rig failure, so be it.  But, the thing is, there is a Mean Time Between Failures (MTBF) for all of the standing rigging components when properly adjusted, and shock loading the shrouds will likely cause a fitting to fail before its "time."

[krissteyn]

Cap'n Smollett      MMmmmmmmm...

I like what you say - makes sense - most of the times I saw the "floppy", the winds were steady and strong - the Cat was flexing and the bottoming the only shock.

On my Mono, I minimise the floppy - But I will take what you say and next time I am tuning, remember it -  :)

[GordMay]

The Rig Tuning Tips, posted by Kingfish, was excerpted from "Rig Maintenance & Tuning", originally posted at:
http://cruisersforum.com/showthread.php?s=&threadid=1290
There are several other good discussions, on the subject, including:
http://cruisersforum.com/showthread.php?s=&threadid=3322
and more.
Regards,
Gord

[krissteyn]

Boat next to mine has returned after 3 days attempting trans-atlantic - reason - leaks too badly and bilge pumps "died".  The skipper was not happy with the state of the boat and his english was not as good as mine so didnt get details.
The worker detailed to "stop the leaks" disclosed the fact that the chainplate holes were elongated and that a lot of moisture was coming thru the hatches. He implied without actually stating it (politically OK - keep my job) that the rig was so stressed from tightening that the chainplates had "moved" and the deck had lifted.  We have had some pretty heavy winds so I assume the boat (Passport 40) was well reefed but ....

Not the first time I have seen a converted "banana boat" - its a shame cause the boat is superficially really pretty...

So    not too floppy - but never too tight....

... and wash out the bilges during sea trials and test the bilge pumps well.
I arrived in Marina hemingway with a leaky exhaust and the last remaining bilge pump (being manual) used 30 minutes out of 60 in a "bit-of-a-blow" - boy was I "concerned"
Good news was the repair cost $30...

[Captain Smollett]

... the last remaining bilge pump (being manual) used 30 minutes out of 60 in a "bit-of-a-blow" - boy was I "concerned"

:o

[GordMay]

How to use Tension Gauges:
http://cruisersforum.com/photopost//showphoto.php?photo=1723
http://cruisersforum.com/photopost//showphoto.php?photo=1724

[Adam]

Great post Kingfish... I cut and pasted it to my "To Print" directory... I'm making a binder for my boat of things that are necessary to know, but aren't done often enough to really memorize correctly :)

Adam

[AdriftAtSea]

Tuning the rig on my boat is a bit different from most boats as the way my mast is setup is a bit different.  Instead of lower shrouds, I have two relatively massive stainless steel struts, made of 1.75" tubing.  The two struts are part of the boat's mast raising system. The rest of the rig is a fairly standard fractional bermudan rig with two spreaders.

[Fortis]

I have a masthead rig with a baby stay and straight spreaders...which is very strong, but an outright bastage to tune.

basically idea is to adjust mast bend by tightening both the baby stay and the backstay as methods for depowering the main. This can get a little adventurous sometimes!

The straight spreaders on this rig means that the balance between the top and bottom shrouds are what will decide how many peices of mast you come home with. Basically, the upper has to be a tiny bit less tense then the lower...but it is very proportional or the mast starts pumping...and that is like a countdown timer for disaster.

Fortunately Fortis has the super heavy duty cruising mast of its type (and the tall rig, to boot)...but some of the racing optimised endeavours chew through masts and it is not one of the designs strong points (then again, it is more a matter of what people have chosen to do with it in the 30+ years since it was built. Straight from the factory I do not think they were ever designed to have mast bend used as an in-race adjustement).

I am fascinated by Adrifts description of his lower shrouds. Any chance of some pictures, Mr Drifty?



Alex.

[AdriftAtSea]

Alex-



Here's a photo of the boombrake setup on my boat, and the lower shroud is the heavy tubing going up to the right in the center of the photorom the chainplates, where the boombrake line attaches to the chain plates. 

From speaking with the boat designer, the tubing shrouds originally started out as 1" tubing, but the compression loads caused the smaller tubing to buckle, so the lower shrouds were increased to the current size, which I believe is 1.75" in diameter.  The tubing is adjustable in length, as it has threaded inserts at each end. :D

Next time I'm down at the boat, later this week, I'll take some photos of the ends of the lower shrouds if you would like me to.  :D
Hope this helps. 

Dan

[CapnK]

{plink plink}  :)

Here's one thing I didn't see anyone touch on in the "slack rigging" discussion. I read about this in Brion Toss' "The Complete Riggers Apprentice"*, and it seems to make much sense, especially considering the source:

The main concern with floppy rigging is not necessarily shock loading, instead it is "work hardening" of the stainless wire. The constant (even though slight) back-and-forth movement of wire not held in some tension will lead to the metal of which the wire is made becoming brittle and breaking, usually at the point where it exits a swage.

Not saying that shock loads shouldn't be considered or aren't a factor in failure, just that they aren't as constant as the continual movement of a boat at sea, and that movement can really affect the wire, which is the weakest component of a rig (usually).

Well, that's $0.02 worth... :)



*A truly excellent book, highly recommended!