The Offshore Voyaging Reference Site

Rig Tuning, Part 1—Preparation

Although just about every facet of sailing has been written about in great depth by many writers, rig tuning seems to be an exception. (There are some articles around on the internet, but most are way too simplistic, and many contain fundamental errors.)

So I’m going to give it a go…

Why DIY?

But first, why learn to tune our own rigs?

Simple, most boatyard crews who step masts have little or no idea how to properly tune a rig. I know that’s harsh but trust me, I have watched masts being stepped in a bunch of different boatyards, including some high-end expensive ones, and it’s sadly true.

Also, a well-tuned rig is not just for racing boats, as many cruisers seem to think (judging from what I see out there). Why? Because poor rig tuning has a surprisingly negative affect on speed and can even, in a variety of ways, actually cause a dismasting and/or stress-cracks in the mast.


And that brings me to a caution: If we are going to take on tuning our own rigs, we need to pay attention and take our time, as this is no place to screw up.

Also, we could really hurt ourselves in the tuning process if we daydream and, for example, unscrew a turnbuckle too far, thereby bringing the whole thing down on our heads. If that sounded like a disclaimer…it was.

And, finally, learning to tune a rig properly and safely, while within the capabilities of most reasonably handy sailors, is not simple. That’s why this series is five chapters long.

Even so, since there are so many variables in rigs and boats, you will have to apply these instructions to your own boat with a large helping of thought—I can’t possibly cover every detail for every boat.

You Can Opt Out

By the way, no shame if you decide rig tuning is not for you.

But Still Worth Reading

But even if you decide to let a pro tune your boat—look to a rigger or sailmaker, not a boatyard—reading this series is worth your time, because doing so will give you the knowledge to at least determine whether the person that you are paying hard-earned cash to actually knows what they are doing.

I Do It My Way

Oh yeah, one more thing before we move on to the good stuff: It’s important to realize that there are ways to tune that are different from mine…used by the misguided. 

Seriously, the key point is that tuning is a methodical process that builds on a full understanding of the forces on, and geometry of, the whole rig viewed holistically. (Wow, who wrote that convoluted sentence? Sounded like something out of a privacy policy.)

What follows is the way that I have evolved over some 40 years. But I’m sure there are other systems that work and some might even be better than mine…naw, couldn’t be.

Whatever, the key point is that we each need to find the system that works for us and then stick with it from start to finish, not mix and match from one or more systems, at least without really thinking about it.

What We Will Cover

I’m going to assume a standard two-spreader keel-stepped mast, first off, because that’s the most common offshore voyaging boat rig and second, because that’s what I know best. 

If you have three spreaders this should work fine, although it will take you longer than two spreaders…a lot longer. John’s first law of rig tuning: Complexity of tuning goes up by the square of the number of spreaders.

If you have a single-spreader rig, just ignore all the stuff about intermediate shrouds.

And if you have a deck-stepped mast, ignore the stuff about mast chocking at the partners.

I will also cover tuning a cutter rig, and that will help anyone with an internal head stay, cutter or not.

What We Won’t Cover

But if your boat relies on radically swept-back spreaders to stay standing, or is a really funky B&R rig, sorry, although this series will give you some pointers that will help, you are on your own simply because I have never tuned one of those types. In fact, back in the day when I was a sailmaker and rigger, these rigs did not even exist! Or at least were not in common use on cruising boats.

Also, in the interests of brevity, although I do know how to tune them, I’m not going to cover fractional rigs.

Wow, that was a lot of ifs, ands, buts, and maybes…on with the show.

Stand Up Straight

The first thing we need to do is get the mast stood up so it’s not leaning off to one side. Don’t laugh, I know that sounds obvious, but most people don’t even try, and of those who do, most do it wrong.

Why wrong? Because they start from the assumption that the boat is perfectly symmetrical and, in so doing, start down the long and winding road to tuning failure and frustration. 

Here’s the reality. In all likelihood:

  • The mast step is not perfectly centred in the boat,
  • and, even if it is, the partners (hole through the deck) is almost certainly not.
  • Anyone who believes that the shroud chainplates are perfectly symmetrically installed in relation to each other and the mast step is probably still writing to the North Pole just before Christmas.
This is why the common advice you see, to use the main halyard or a tape measure to measure down to each cap shroud chain plate (or the toe rail) to centre the mast, is wrong.

Well, then, what should we do?

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More Articles From Online Book: Sail Handling and Rigging Made Easy:

  1. Six Reasons To Leave The Cockpit Often
  2. Don’t Forget About The Sails
  3. Your Mainsail Is Your Friend
  4. Hoisting the Mainsail Made Easy—Simplicity in Action
  5. Reefs: How Many and How Deep
  6. Reefing Made Easy
  7. Reefing From The Cockpit 2.0—Thinking Things Through
  8. Reefing Questions and Answers
  9. A Dangerous Myth about Reefing
  10. Mainsail Handling Made Easy with Lazyjacks
  11. Topping Lift Tips and a Hack
  12. 12 Reasons The Cutter Is A Great Offshore Voyaging Rig
  13. Cutter Rig—Should You Buy or Convert?
  14. Cutter Rig—Optimizing and/or Converting
  15. Cruising Rigs—Sloop, Cutter, or Solent?
  16. Sailboat Deck Layouts
  17. The Case For Roller-Furling Headsails
  18. UV Protection For Roller Furling Sails
  19. In-Mast, In-Boom, or Slab Reefing—Convenience and Reliability
  20. In-Mast, In-Boom, or Slab Reefing —Performance, Cost and Safety
  21. The Case For Hank On Headsails
  22. Making Life Easier—Roller Reefing/Furling
  23. Making Life Easier—Storm Jib
  24. Gennaker Furlers Come Of Age
  25. Swept-Back Spreaders—We Just Don’t Get It!
  26. Q&A: Staysail Stay: Roller Furling And Fixed Vs Hanks And Removable
  27. Rigid Vangs
  28. Rigging a Proper Preventer, Part 1
  29. Rigging a Proper Preventer—Part 2
  30. Amidships “Preventers”—A Bad Idea That Can Kill
  31. Keeping The Boom Under Control—Boom Brakes
  32. Downwind Sailing, Tips and Tricks
  33. Downwind Sailing—Poling Out The Jib
  34. Setting and Striking a Spinnaker Made Easy and Safe
  35. Ten Tips To Fix Weather Helm
  36. Running Rigging Recommendations—Part 1
  37. Running Rigging Recommendations—Part 2
  38. Two Dangerous Rigging Mistakes
  39. Rig Tuning, Part 1—Preparation
  40. Rig Tuning, Part 2—Understanding Rake and Bend
  41. Rig Tuning, Part 3—6 Steps to a Great Tune
  42. Rig Tuning, Part 4—Mast Blocking, Stay Tension, and Spreaders
  43. Rig Tuning, Part 5—Sailing Tune
  44. 12 Great Rigging Hacks
  45. 9 Tips To Make Unstepping a Sailboat Mast Easier
  46. Cruising Sailboat Spar Inspection
  47. Cruising Sailboat Standing Rigging Inspection
  48. Cruising Sailboat Running Rigging Inspection
  49. Cruising Sailboat Rig Wiring and Lighting Inspection
  50. Cruising Sailboat Roller Furler and Track Inspection
  51. Download Cruising Sailboat Rig Checklist
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Marc Dacey

I look forward to the rest of this, John. Thanks for collating your collected tuning wisdom.


Before all, how do you unscrew the turnbuckles totally blocked since 7 years? (lack of grease in the beginning)?


I would suggest using a decent flex and investing in new turnbuckles 😉

Terry Thatcher

Sorry to be my typical dumb self, but can you include a diagram of what you mean by an “arc in the fore and aft plane”?

Dick Stevenson

Hi John,
A really nice procedure for getting the mast straight. I was wondering whether it could be done on the hard? I suspect if your answer is “no” it is because the hull shape changes too much from when the boat is in the water. Or I missed something else.
Also: by mast butt, I assume you mean a piece of equipment attached to the base of the mast: equipment I have never seen/used (that is if it can be removed and taken to a machine shop). I also assume the fixed base of the mast resting on the step should have this same arc you refer to. Can you say any more about the nature of this arc? For example: does the arc drop 1 mm from mid mast base to the aft end? More? Less? Any reference materials?
Thanks, Dick Stevenson, s/v Alchemy

Eric Klem

Hi Dick,

For what it is worth, here is what I have done for tuning on the hard. With our previous boat, I did this a few times based on having counted turns on the cap shrouds when undoing them and writing it down. I figured that there wasn’t much to change just based on an assembly and disassembly and as best I could figure out, the mast was always well aligned. Note that the first time had been done in the water and then I only adjusted symmetrically from there. FYI, our tune seems to be pretty similar on the hard and in the water and I would expect the same from most of the heavier built cruising boats.

This spring, for the first time I ran into the problem of new standing rigging and initial tuning on the hard. I first thought about measuring the angle of the boat (I have access to highly accurate digital protractors) and then figuring out the plumb bob offset. However, given that I really wanted it to be right as I was also going to be pouring spartite, I figured that I had better get the boat level. I was surprised by how easy it was to do with simply adjusting jackstands. I went about 1 turn at a time and ran them tighter than normal to ensure support. One thing to note is that I own our jackstands and keep the threads in good shape, boatyard jackstands may require cleaning and greasing to do this as otherwise you won’t be able to generate the force. Your V42 is probably at the upper limit of size for where this technique would work. Obviously, you do need to be careful not to loosen the stands too much which could be disastrous. For a smaller boat, it is probably easier than messing with a hydraulic trailer or travel-lift which aren’t that good at super fine tuning.

I am interested to see how my method stays similar or differs from John as he gets more into it.


Dick Stevenson

Hi Eric,
Thanks for your thoughts. They align with mine. I have once or twice wanted to adjust the athwartships balance of the boat and have nudged Alchemy to a more upright position in just the way you describe. It was really quite easily accomplished, but a job best done in small increments, and with patience, on a calm day.
As to establishing a pre-set for one’s rigging, I have been doing that for years. I started by counting turns, then counted threads, but have evolved to putting a micrometer between the faces of the 2 fixed receptacles for the threaded stud. This has proved easy, repeatable and very exact.
Rod rigging helps, for sure, but I find I can return each shroud to my recorded micrometer measurements and almost not have to do much from there.
It should be noted, that, although I like to sail and like to sail well, I am not a racer, which is where, I believe, one really learns one’s chops in this area. So, I will be interested in John’s coming installments to see where improvements might be had.
My best, Dick Stevenson, s/v Alchemy

Marc Dacey

Dick, we have a similar interest in getting the boat to as close to its full sailing potential as we can, and achieving proper rig tensioning and setup is key to this. We started as racers, and learned this directly because most boat that don’t successfully race strike us as under-tensioned or improperly tensioned (overcranked differentially, for the most part).

Proper rig tension is also key to getting proper balance in the sails, which affects weather or lee helm and thus affects total miles per day on passage. Even a “barge”, such as our steel, full-keeled cutter, can, with some refining, produce far better results in terms of speed and even pointing ability than a quick glance at her modest rig would suggest. The micrometer idea is a good one, although I still need to buy the bigger model of Loos gauge suitable for 5/16th inch stays and shrouds. Of course, your micrometer is basically the same idea in a different plane.

Dick Stevenson

Hi John,
Your admonitions about boat support on the hard are well taken as is your observation that many boats are poorly supported.
Many years ago, when we started our wandering and encountering serial boatyards, I remember changing my headset from “the yard guys are in charge now” to one where “the boat is my responsibility wherever it is”.
With that in mind, I, very politely, work out the support stands with the yard foreman: if I can, I do it ahead of time. More often than not, I express my being a “nervous” owner and ask for another set of side supports (often also bow support) and I always offer to pay some extra for their use (I have never been asked to do so). Usually this means I have an extra pair of stands over the boats around me.
Speaking of boats around me, I also insist not to be near any boat stored with headsails still furled. It never fails to amaze me that some owners do this and that some yards allow this.
My best, Dick Stevenson, s/v Alchemy

Eric Klem

Hi Dick and John,

Unfortunately your points about boat support are all too true. I actually got our marina to add a clause to their contract forbidding sails from being on deck.



What a breath of fresh air. Yes I know about Selden’s tuning method – I’ve a ‘crude deck stepped cruiser’, not a ‘refined keel stepped racer’ (did you get the alliteration in that?). Though your ‘verticilaty’ advice is very, very important and I utterly agree, I want to hear about rig tensions and how – as an amateur – to assess/measure appropriate stress in the riging. Part 2? Please don’t keep us too long.

Jim Evans

Been there, done that: although I could have used this information! But now, I can enjoy my coffee while admiring the free-standing mast on my Freedom… (While waiting for all the comments on why it’s not an appropriate offshore rig, with which I will agree anyway).

Brent Cameron

You might want to add Cap Stays to your definition. Also Seldon makes a good 90 odd page free PDF that describes much of this and is what I’ve always done. I’d be interested in where you think they are wrong. You already seem to be more fussy about getting the boat perfectly level. Nice job though so far!


This question is not related to tuning. I have a keel step mast that has a very small holes at the bottom to bring all the wirings. Is it ok to make a 2″ by 2″ cutout to help feeding the wires and then have a aluminum plate cover that would be bolted every 1/2 inch? Charles


what about using iPhone level app? I have one and seems very accurate….BTW great idea with the leveling boat first and THEN installing good inclinometer….why I didn’t think about that ?….Thank you for writing this instructions.

Marek Nowicki

Not many (if any) flat surfaces on my it to use 3 ft level…..will try to balance thing….good idea. Thanks John!

Richard Stevenson

Hi John, Just an FYI as I know you track anomalies: the site just stopped filling in the “Name” and “Email” requests when commenting as the site has done regularly in the past. Also, I have received the just-posted-by-me Email in my personal mailbox, another change. Dick

Colin Post

Hi John.
I understand that you don’t have the space or time to cover all types of rigs. However, being the owner of a fractional rig, where would you suggest researching how to correctly tune one of these?

Rick Gleason

Last winter was the first time we left the mast stepped. The yard advised to leave the rigging with no changes.

Dick from Alchemy uses a micrometer on his rod rigging for repeatability, which leads me to the question: How many of you are loosening your rigs slightly in the winter? and why?

Dick Stevenson

Hi Rick,
I was waiting to respond, thinking someone might actually “know” the answer.
I am often in new and untested yards and, over the years, I have seen far more damage to spars going in and out of boats than has ever happened at sea. That, and yards where the masts are often stored in the boat frequently have marginal conditions for storage: places where cars and plows come close around corners for ex. This last winter I would have had to hire an outside crane, not used to mast work, to get the mast out, so it stayed in. So, I am wary of my mast being plucked and have often opted to leave it in. That said, I think mast out is the wisest choice if it can be done by experienced hands.
What I do: I do not slack the rigging. I take up on the turnbuckle on the backstay (usually only firm when the hydraulic backstay is loosened) so it is tight-ish. I then take 5-6 pumps on the hydraulic backstay so the seals do not get worked with changing atmospheric pressure (done regularly during the season as well) and, amazingly, it is still compressed after a full winter’s neglect. I also set the running backstays, again tight-ish.
Also, all sails are off and all running rigging is removed and only messenger lines are left to catch the wind.
My thinking is that I do not want any chance of the kind of looseness that could lead to shock loading. However, I hate the occasional whole-boat vibration that gets going when the wind is up.
My best, Dick Stevenson, s/v Alchemy

Marc Dacey

This was my routine with my keel-stepped sloop here in Toronto. I too never quite got used to the vibrations in the cradle (and I never removed the halyards as I was regularly visiting to charge the batteries in situ and do boat chores when weather allowed). Our current boat allows the mast to pivot back over the pilothouse, and I would store the mast that way with a wooden gallows to keep it off the solar arch and allow access. That avoids a lot of wiring rearrangement and a quick start the next season. Unfortunately, at my YC, we must dismast to a rack and a few light fixture replacements have been sacrificed as a result.

Dick Stevenson

Hi Marc,
I actually pulled all my running rigging out even when I was living aboard for a winter and could check every day. Even halyards that are internally led produce a fair amount of wind resistance. I also like to get them out for inspection and to give them a good soaking, actually a series of good soakings, and sometimes turn them end for end. Left in all winter, they usually became quite dirty.
My best, Dick Stevenson, s/v Alchemy

Marc Dacey

Dick, that’s something I’ve contemplated but never actually done, although I have washed docklines and sheets clean in buckets and in heavy-duty washing machines (secured in stout mesh bags) before. Perhaps I should try it. Thank you for the tip.

Eric Klem

Hi Rick,

I don’t have a perfect answer either but I am inclined to agree with everyone that leaving the rig tensioned is appropriate. I think that the main goal is to keep the rig from moving around as this could lead to high enough loads for fatigue and also it could contribute to movement of the whole boat which could lead to falling over. The best way to keep it from moving around is to keep everything tight including running backstays and other temporary rig supports.

From a loads standpoint, there should be no damage to any of the components from keeping stress in them. For fatigue, sitting with a constant amount of stress even if high has no fatigue as fatigue is due to the cycling of that stress. There is a small amount of cycling due to wind loading but this should all be below the fatigue limit for the wire and negligible for the aluminum mast. Some materials do creep and this includes fiberglass but I highly doubt that anyone has ever had an issue due to this except maybe on a super light build. Afterall, boats that are not hauled for the winter don’t have any issues.

The one material that can be very different is if the hull is wood. Lightly built older wooden boats sometimes look distorted around their shroud chainplates. Strangely, a great way to minimize hogging in these is to keep the forestay and backstay tight.

Like Dick, the mast vibrating is never my favorite although I doubt that it actually is a big deal in normal conditions. I have long wondered whether before a really high wind event (eyewall hit of a hurricane), it would make sense to go aloft and wrap a large diameter line in a spiral down the mast. The theory would be to limit vortex shedding just like you see on many smokestacks. This is way outside my area of expertise and I have never tried it but the enormous number of rigs lost in Irma suggest that it could be useful.

I also have to agree with Dick’s concern over damage to the rig from pulling it. The more that I think about it, the less I am inclined to pull it unless in a really windy spot or going inside a building.


Sam Shafer

Do you have pictures of the mast step and butt?

Chuck Batson

I do not have a mast heel fitting. The bare extruded aluminum rests right on the step. It looks like the step was designed for doing exactly that–accepting the bare butt of the spar. The step does not look at all like it could accept a heel fitting. If I wanted to switch to a heel fitting, it appears replacing the step would be a rather significant undertaking, not itself without risk.

Has anyone here replaced their mast step? And might be able to confirm or deny the complexity I imagine in doing so properly?

Chuck Batson

Hello John, thank you for your reply. I also saw that there are discussions in the comments of later chapters relating to bare extrusions on the step.

In a separate question, I have the mast supported by the cap shrouds with minimal compression. However, the mast is bowing *aft*. To make sure I wasn’t crazy, I raised a thin line from the genoa halyard and pulled it taut. Sure enough, there’s about an inch or so bowing which peaks below the spreaders (single set). I’m pretty sure it’s not headstay tension as I slacked that off a bit and I can see the furler sagging. The only things I can think of are the weight of the furler or perhaps the mast spent too much time on racks without support in the middle. Now what? Do I proceed on faith that prebend / forward lowers will work this out?

Vesa Ikonen

If you are having trouble getting the Plumb Bob to settle down, place a bucket of water on the cabin top, and sink the wrench so it does not touch the bottom. This probably requires tuning with the boom removed, but I find it easier to do it that way anyways.
Also, having two people (of similar weight) turning the turnbuckles while you sight the mast keeps the boat level and speeds things up.

Richard Cordovano

What is a “wow”? It sounds like it is a bend athwartship instead of fore and aft?