How to Tune a Sailboat Mast

How to adjust a turnbuckle. Tuning the mastHere 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.

How to tune a sailboat mast

Image courtesy of Berthon Marina, UK. Click image to link to their site.

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.

Image courtesy of UK Sailmakers. Click image to link to their site.

Image courtesy of UK Sailmakers. Click image to link to their site.

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.

About The Rigging Company, LLP

We provide complete and professional rigging products and services!
This entry was posted in Classic Yachts, Cruisers, Modern Yachts, Racers, Rigging, Tech Tips and tagged , , , , , , , , , , , , , , , , , , , . Bookmark the permalink.

19 Responses to How to Tune a Sailboat Mast

  1. Jerry McGraw says:

    I have had a problem with securing the spreaders to the shrouds, resulting in the spreaders dropping. I am using stainless wire to seize them but still having a problem. Any tips on how to do this properly?

    • The Rigging Company, LLP says:

      Hey Jerry,

      Seizing the wire onto spreaders with hinged spreaders is a bit of a trick of the trade that requires some practice. We use the X’s and O’s method. The end result should be something that looks like this…https://theriggingcompany.files.wordpress.com/2011/11/2012-06-07_14-26-09_899.jpg?w=900. A trick to make the wire bite into the spreader end a bit more is to wedge a small piece of leather between the spreader and the wire before seizing. Also parceling and serving the wire where it intersects the spreader will help create more bite too. Lastly, and I don’t like this method but you can install a bull dog cable clamp beneath the spreader, nuts facing in, to keep it from dropping when slack.

      I hope that helps a little. Thanks for commenting.

      ~T.R.C.

  2. Bernard says:

    I am struggling to get enough rake into my mast. 33 foot Charger 33 keel stepped. Have loosened forestay and moved mast foot forward by about 10 mm. Should the chocks in the collar be adjusted? Runners and 2 spreaders, and check spreader. Spreaders do not have much aft angle. Move mast step more forward? Outers are tight with inners looser. Thoughts?

    • The Rigging Company, LLP says:

      Hey Bernard,

      Yeah, it sounds like chocks are the last thing. Maybe remove the chocks with the rigging slack and see if you can get the mast to sit where you like it with just hand tension. Then chock it where it wants to sit. It sounds like you are on the right track everywhere else, perhaps add a toggle into the headstay and shorten the backstay is next. Good luck and I hope that helps somewhat.

      ~T.R.C.

  3. Steve says:

    Hi, We have a Lagoon Catamaran with fractional rig, upper and lower shrouds, fore stay and upper and lower diamonds. No back stay. The mast has a degree of pre-bend. I do not plan to drop the mast.

    I may have to do some work on the port side upper diamond. Is it as easy as just undoing the turnbuckle? Or do I need to loosen the starboard one at the same time. If it needs replacement should I also replace the starboard one even if in good condition?

    As a further question, what happens if a diamond breaks, does it result in mast failure?

    • The Rigging Company, LLP says:

      Hey Steve,

      You would need to loosen the other counterpart to that stay for sure. It is just good practice, will keep the mast straight, and also make your life easier for removal install. Now, do you replace both? I don’t know. How old is the standing rigging? Why are you replacing the one? If it is not all due for replacement and you are just replacing due to damage, just do the one, but loosen both sides to do this.

      Hope that helps and thanks for the visit.

      ~T.R.C.

  4. Eric Hassam says:

    Hello! I recently purchased a keel-stepped 1982 Goman Express 30 which came with an Alado Furler. I have been sailing it since May of this year. My question is this: Despite relocating mast wedges at the cabin roof to bias the lower mast aft about 2″, I still have a pronounced backward bend (10 degrees or so) just above the highest spreader. When sailing on jib alone, most wave action causes the mast to pump right at the bend point. I have a split backstay that is as un-tensioned as possible and the forestay only has another inch of adjustment left. There is no baby stay.

    How can I get the bend out of the mast? How concerned should I be that the mast might break at that point?

    Thanks in advance for your reply!

    Eric Hassam – Delta Flyer

    • The Rigging Company, LLP says:

      Hi Eric,

      Thanks for taking the time to comment on our site. It sounds like you are on the right track. So one other adjustment that you have is the mast step position. This greatly affects mast bend on keel stepped masts. For a stronger bend and less rake, move the mast butt aft. For more rake and less bend (probably what you need to try), move the mast step forward a bit. If neither of these help, you may be off to have your headstay shortened and this means it is too long. This is likely not the case, but it is a possibility.

      Keep in mind….A mast should have a slight aft rake bias along with a small amount of mast bend. This is quite normal. You can send us a picture if you’d like a second opinion on if it is over-bent. Having said all of that, even if you remove all of the mast bend, the mast may still pump. This is a design flaw in many spar designs that lots of end users have experienced. This can be remedied by redesigning the stay lay out. Is there a place for a staysail stay and/ or runner backstays? If so add them. Is there a place for a baby stay? If not, that may be a consideration.

      Thanks again and I hope that helps.

      ~T.R.C.

  5. bill chesley says:

    Hi, I have a 48 foot yawl with a 7/8 fractional rig, is the tuning procedure the same as a masthead rig? I seem to have trouble getting aft rake and proper headstay tension. Also, is there a particular tension number the upper shrouds should have? many thanks in advance

    • The Rigging Company, LLP says:

      Hi Bill, thanks for taking the time. 7/8 is very close and I would treat it like a masthead rig, especially if the none of the spreaders are aft swept. Tesnsion the headstay using the backstay(s). This should pull the top of the mast aft. If there are any other forward stays, i.e. stay sail stay, forward lowers, or anything else that could be holding the mast forward, go ahead and loosen those completely. You then may need to tighten the Tri-attic (the stay that connects the top of the mizzen and top of the main) if present. OR if the mizzen needs more rake too, then lossen all forward stays and pull it back using the available aft stays for this as well.

      Hope this helps and please email us and send some pictures if you need more help.

      ~T.R.C.

  6. John Wade says:

    I have a 1972 Morgan 27, which has both forward and after lower shrouds. I wish to remove the forward lowers so I can trim a 110% jib inside the stays. I see a lot of boats without forward lowers and think this will work OK, but wonder if I should increase the size of the aft lowers and beef up the chain plates. Any suggestions?

    • The Rigging Company, LLP says:

      Hi John,

      Unless there are other owners of the same boat that have experience in this I would NOT remove them. Boats without forward lowers are usually using aft swept spreaders. This type of rig has a different dynamic altogether. They are also usually fractionally rigged. I think the result would be sever mast pumping if not worse along with other potential issues. You can still utilize inboard sheeting via some different jib lead arrangements. I think this would be time/ money better spent. Look at Catalina 27's....
      

      Hope that helps.

      ~T.R.C.

  7. Gene Livelace says:

    I have rod rigging on my Beneteau 32s5

    Any other guidance on tuning them vs wire rigging

    • The Rigging Company, LLP says:

      Hi and thanks for commenting.

      Just follow the guidelines in the write up. The over all goal is that the mast needs to be straight and in-column when looking at it from side to side.

      Fore and aft, the mast should show a very slight lean aft. Depending on whether or not the spreaders are in-line or aft swept; you should also see some slight bend if there is any aft sweep to the spreaders just from the tension of the uppers.

      A Rod stay tends to run a bit tighter than wire, so keep that in mind.

      For racing, ideally once the static tune at the dock (the part we just talked about) is done, go out and sail tune. Do this by going hard on the wind and checking to see if the leeward shrouds are just starting to dance, this is ideal. If they are swaying about they are too loose for the current conditions. If the leeward shrouds are tight, they may be a touch to tight. Tension and loosen as needed; count what you did and to what shroud, then tack and do the same to the other side.

      ALWAYS secure the turnbuckles when you are finished adjusting them.

      Hope that helps.

      ~T.R.C.

  8. Pingback: Tuning a Sailboat Mast | ChesapeakeLiving.com

  9. Pingback: Rig Tuned | middlebaysailing

  10. Anonymous says:

    Wow, I would hate to be charged by her for three trips up the rig and forget the screw driver the rubber plugs that are sacraficial and replaced everytime removed just to clean the stainless 1×19 rigging.

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