Here are some general guidelines for tuning your mast’s standing rigging. Please see our blog on how to properly adjust a turnbuckle before you begin. As always we recommend seeking the advice of a professional rigger for more specific tips and tricks regarding tuning your boat’s rigging.
Your boat must be in the water. Begin by just slacking off all of the side shrouds as evenly as possible, so that all stays can be adjusted by hand. Once loose, try and adjust all turnbuckles so that they are pretty much equally open (or closed) from port to starboard respectfully. Also go ahead and line up the cotter pin holes (if present) in the studs so that they are in a pin-able position. Now is also the time to balance out the threads, between the upper and lower studs of the turnbuckle, IF they are not even. Do this by unpinning the turnbuckle from the chainplate – BE CAREFUL HERE – to ensure the mast is secure before unpinning any one stay. Lastly, loosen all halyards or anything that may pull the mast to port, starboard, forward or aft.
1. Check by sighting up the backside of the mast to see how straight your spar is side to side. You can take a masthead halyard from side to side to ensure that the masthead is on center. Do this by placing a wrap of tape 3′ up from the upper chainplate pin hole on each upper shroud. Cleat the halyard and pull it to the tape mark on one side, mark the halyard where it intersects the tape on the shroud. Now do this to the other side, the mark on the halyard should also intersect the tape similarly. Please note: when the mast is equipped with port and starboard sheaves, instead of just one center-line sheave, it will appear slightly off to one side. Just keep this in mind……
2. Using the upper shrouds as controls, center the masthead as much as possible using hand tension only. Some masts are just crooked. If yours is(are) crooked, it will reveal itself when you loosen all of the stays and halyards initially and sight up the mast. Although you should use hand tension only, you can use a wrench to hold the standing portion (the stay portion) of the turnbuckle. If for some reason the shroud is totally slack and you still can’t turn the turnbuckle by hand then the turnbuckle may need to be serviced, inspected, and maybe replaced.
3. Tune the mast from the top shroud on-down, making sure the mast is in column. Remember: as you tension one shroud by adjusting the turnbuckle, to loosen the opposing shroud the same amount.
4. Once the mast is fairly straight from side to side, tighten the shrouds all evenly using tools for tensioning. Typically, for proper tension, the shrouds should be tightened using these guidelines; uppers are the tightest, and then fwd. lowers, then the aft lowers and intermediates should be hand tight plus just a turn or two. ~With an in-mast furler it is recommended to tension the aft lower a bit more to promote a straighter spar (fore and aft) for better furling.
5. Now you can tension the aft most backstay (s). If the backstay has an adjuster it should be set at a base setting (500-1000 lbs). If the backstay simply has a turnbuckle then it should be tightened well. After this has been done, in either situation (adjustable or static backstay), one should site up the mast from a-beam and notice that the masthead has a ‘slight’ aft bias. If there is no aft bias, too much, or the mast is inverted (leaning forward), then the forward most forestay (s) will most likely need to be adjusted to correct this. If a furler is present then seek the council of a professional rigger or refer to your furler’s manual for instructions on how to access the turnbuckle if there is one present.
6. Finally, sight up the mast one last time and make any necessary adjustments.
7. MAKE SURE ALL TURNBUCKLES AND PINS HAVE COTTER PINS AND ARE TAPED NEATLY TO PREVENT CHAFE!
Read HERE for how to use a LOOS & Co. Tension Gauge!
Here is a little vid from our friend Scott at Selden Masts (click the link then hints and advice for more info) on rig tune…..
Is your mast fractionally rigged, only has a single set of lowers or is just plain different? Be sure to leave any questions or comments below.