John, I don't think too many riggers will be put out of business or even resent the fact that there is good info available.Disclaimers don't mean squat anymore (who's smart enough to understand them?), you'll probably be in the middle of a class action suit soon from all the unemployed riggers that your information put out of business.
Thanks Alex, timely info., I should be stepping the mast within a month and I'll have this printed out and with me when I do.
I posted the following awhile ago. While not nearly as in depth or comprehensive as Alex's perhaps it has it's place.
The first part speaks to inspections while the rest addresses tuning.
"While not intending to dismiss anyone's advice, I am going to try to simplify this whole process.
Cracked swages are really not too difficult to find. Clean the surface of the fitting with a scotch-brite (it helps if you spit on it before scrubbing), then take your magnifying glass and look very carefully over the whole thing. Don't neglect to inspect the clevis and cotter pins/rings.
I've even seen a fairly young marine eye with absolutely no swage cracks split above the clevis pin.
If you have swage cracks they will be visible, if not obvious.
If your rigging is more than ten years old and it has been in central Florida for all that time then you are likely to find a crack or two.
If you find a small crack in your starboard upper and you have reason to believe the rigging is all of the same vintage then you will probably find some more upon closer inspection.
If you only have one week off from work, (and it's next week), and you have been planning this trip to Honeymoon Island for months and you have sense enough to reef early, stay at anchor or motor if you think you are stressing the rig, then you can almost assuredly enjoy a nice vacation and then rerig when convienent. Certainly before you decide to do the thursday night beer can race at the yacht club.
I've seen, and continue to see neglected and poorly designed rigging stand up to amazing abuse.
That said, you never want to push it. If you have time to rerig before your trip, then do it. If you can't, then take it easy, be smart and have a nice trip.
Most rigging, made by a professional will be consistant. Meaning that your starboard upper shroud will be almost exactly the same length as the port upper. (+or- 1/8" to 1/4"). So, if your mast is standing, then adjust your upper shroud turnbuckes exactly the same by opening them to the same point while your mast is being held by the lowers,headstay and backstay (you may even want to open the turnbuckles up completely and make sure the stud and t-bolt, ie top and bottom are started evenly).
Then while tightening, count the turns and take up the exact same count on each side until hand tight. Now ease off the lowers one at a time and set them all hand tight.
Next ease and set to hand tight the backstay and headstay, (if ajustable or accessable depending on furling systems). Now stop and sight up the main sail track like a gunbarrel. You will be able to see any curve (side to side) or bow (Fore and Aft) right away.
If the mast is curving to starboard and bowing forward, then start to adjust it out by tightening the starboard forward lower and backstay. It's all pretty logical if you just remember that you want to keep the top of the mast in the middle of the boat. So move the middle of the mast.
I realize that one must assume that the last rigger made the rigging correctly.
That the builder put the hole or the mast step in the middle of the deck and the chainplates are the same length and in the same positions, but what the hell, you have to make some assumptions in life.
It's really pretty easy to see if a rig has been piece-mealed and as for the rest a tape measure will answer most questions if you are really worried.
Anyway, back to the tuning.
Now that you have the mast in column, It's time to go for tentioning. If you have a gauge the use it. Set the shouds at the same tension, somewhere around the middle of the scale.
The most important part is to do the same thing on each side. If you turn the starboard upper three full turns then turn the port upper the same. Port aft lower two turns, Stb aft lower two turns etc.
If you don't have a gauge then just feel them. Don't try to make them sound like a guitar string but just get them tight. Tighten the uppers more than the intermediates and the intermediates more than the lowers. This assumes that the uppers are of an equal or larger diameter that the intermediates and the intermediates are of an equal or larger diameter than the lowers.
I have never seen a mast bowed forward on purpose. Lots of masts bow aft, some even are designed that way. Unless you have a in-mast main furler you probably won't have to worry about a little aft bow.
As far a rake (how much the mast leans aft from vertical), that can also usually be determined by the adjustment of the turnbuckles, Furlers and backstay adjusters.
If you have turnbuckles on both the HS and BS then go for about 50% adjustment on both. Adjust that later depending on weather-helm or lee helm.
After you have successfully tightened all the shrouds and stays to a reasonable degree, the mast is in column side to side and you have the desired amount of bow then go sailing. In a moderate breeze, sailing a close reach your mast should still be in column and there should be no shrouds swinging in the breeze. Meaning that even the looward shrouds should still be under some, if smaller load. If not then adjust the loose shouds, counting the turns, come about and do the same thing on the other side.
Again, the same turns on each side. Keep it in column.
If your headstay deflects too much and you can't sail too well to winward then tighten up the headtstay or backstay depending on weather/lee helm (you might want to ask a knowledgeable friend or racer to go sailing with you for this)
After returning to the dock, eyeball up the mast again. If necessary, make whatever minor adjustments to make sure the mast is in column then install all the cotter rings/pins.
I have not made it a practice to go sailing on the boats that I tune. Don't have the time. Most riggers don't. As a sailor, it's a skill that one needs to aquire.
Good luck and happy sailing"