When it comes to sailboats, there are two main distinctions: deck stepped and keel stepped. This refers to how the mast is supported and directly affects the strength and reliability of the mast.
Which one is safer? Find out in the video link below!
Securing Continuous Furler Pin
The clevis pin on this continuous furler used for a Code 0 sail kept having problems. To reduce snagging, a cotter ring was used to retain the clevis pin. The cotter ring fouled on the furled Genoa and pulled itself straight! Thankfully the pin fell out after the sail was furled and lowered onto the deck. While being put into its locker, the clevis pin fell out and everything landed inside the locker disconnected, but nothing fell overboard!
To prevent this from recurring, we needed to use a different form or retaining pin. Cotter ring failed and a cotter pin would snag on too many things, so our only option left was to stitch together a retaining pin.
Using the available holes, I stitched stainless steel seizing wire through the clevis pin and back through the swivel.
On the other side, I simply sent the wire back to the primary side, until it was all ready to tie off. Once plenty of wraps had occurred, I twisted the wires together and fed them back into the swivel where they remain protected from any snags and safely tucked away.
Most importantly, the wires never tough the top of the torsion rope as the eye splice passes over the clevis pin in the swivel. The clevis pin is fully retained and no chafe occurs internationally. This retaining setup will hold everything in place while preventing any snags on sails or gear up at the masthead.
Deck Stepped vs Keel Stepped Mast
Sailboat rigs can broadly be separated into two main groups: Keel Stepped and Deck Stepped; each with it’s own particular attributes and drawbacks.
This distinction refers to the location of the mast step, or where the base of the mast is located. With Keel Stepped, the mast stands on the keel at the bottom of the hull, while Deck Stepped means that the mast stands on the top of the deck.
Deck Stepped
The most obvious difference between the two from a livability standpoint is the presence or absence of a mast inside the cabin. For the Keel Stepped mast to reach the keel, there needs to be a giant hole in the deck where the mast slips through to then pierce the cabin area and finally rest on the keel. This means that no matter how “open and airy” they make the cabin, there will always be a spar stuck right in the middle! Deck Stepped allows for the mast to stay outside and therefore the cabin can exist completely unobstructed without the presence of the spar.
Open salon on a Deck Stepped yacht
Mast in the middle of the salon on a Keel Stepped yacht
This is as far as cosmetics go concerning the mast step position, from here on everything gets technical!
On either a Deck Stepped or Keel Stepped yacht, the mast height will be the same, which means that the length of the spar inside the cabin will make up the difference. This means that a keel stepped mast will naturally have a longer total spar length and this spar will be supported at one additional point than a Deck Stepped mast.
This becomes important in mast stability, as each point of support to the spar makes the spar stiffer. Try taking an uncooked spaghetti noodle and push on it only at the ends; the noodle will bend easily. Now have someone pinch the noodle in the middle and push the same as before, it will not bend nearly as much. If the noodle is pinched in two positions, it becomes even stiffer, and so on and so on.
Each point of contact to the spar stiffens the whole structure. Each point of contact with the spar exists in the form of points where stays attach to the mast, as well as the mast step, and in the case of a keel stepped mast: the mast/deck interface.
In rigging, each span between a contact point is known as a panel, and typically, the shorter the panel, the stiffer the spar will be.
Naturally, if you have two almost identical yachts with two sets of spreaders, one being Keel Stepped and the other being Deck Stepped; the number of contact points would differ by one.
Both yachts will have contact points at the masthead, at the top spreaders, at the lower spreaders, and at the mast step, but the Keel Stepped yacht will also have a contact point at the mast/deck interface.
In other words, on a two spreader rig, there are 4 points of contact for the Deck Stepped and 5 points of contact for the Keel Stepped.
It seems simple enough, to make them identical, all you need to do is add a set of spreaders to the Deck Stepped version and you will have the same number of contact points, thus the same stiffness in the spar.
Keel Stepped
In theory, yes, but it isn’t identical in practice. See, the mast/deck interface is non mobile. There is no wiggle room between the two as mast wedges are actually driven in between the two to center the mast and hold everything incredibly still. The first spreader position, by contrast is supported by stays which are both adjustable and also dynamic (they move around as the mast moves). In other words, the number of contact points is identical but the type of contact points is not, therefore they are not the same.
You might be wondering why both styles exist. Obviously one is better than the other and therefore should be the only style produced! This is true, but just as “Beauty is in the eye of the beholder”, so is the “perfect sailboat rig”.
Stiffness and stability of the spar is the primary goal of standing rigging, but the secondary goal of standing rigging is sail trim. Yes, running rigging has the primary goal of sail trim and that is what you adjust if you want to trim your sails, but standing rigging is just as important (though not as easy to adjust). The bend of the mast and headstay tension play huge roles in sail trim. If the mast is very straight, you will have more lee helm while if the mast is bent aft, you will have more weather helm. Just the same, a slack headstay will give a more powerful luff to the headsail and more power off the wind while a tighter headstay will straighten out the luff and give better pointing ability and windward performance.
Yes, I said performance and that is where the difference resides. For a slow and steady cruising yacht, a stout spar is the bees knees. It’s stiff and strong and will hold up to any condition. This is why Keel Stepped yachts are preferred for cruising! This “Set it and Forget it” mentality is not shared by those in the racing community.
Deck Stepped yachts have mast that are more bendy and flexible. This means that the mast is also more easily adjustable which means that optimum performance can always be extracted by making small adjustments to the standing rigging. Going upwind, the backstay, runners, and check stays can be have tension added to them to tighten the stays and pull the mast aft. This will both rake the mast aft giving it weather helm as well as tension the headstay for added pointing ability. By contrast, when running off the wind, the aft stays can be slackened which will let the mast swing forward and ease the headstay, giving the yacht lee helm and filling the powerful headsail even further!
Here the bendy mast actually pumped forward and is bent forward and at very high risk of breaking
In racing, Deck Stepped is king, while in cruising, Keel Stepped is strong. Why the difference? Wouldn’t it be nice to get somewhere faster and have more time to enjoy the destination? That would be a cruisers dream, but it would also be their nightmare.
Racing differs from cruising in many aspects, but one major aspect is the availability of help. In a race, there are many people sailing along side you, as well as entire teams that are there to support you in a time of need or crisis. This means that if something breaks, it’s not the end of the world because a professional will be along shortly to repair it for you. A cruiser is all alone!
If something breaks on a cruising yacht anchored in a remote deserted island, no one is going to come to their aid. I can’t say that cruisers see storms while racers do not because almost all of the catastrophic sailing events occurred to race yachts during a race! That said, a cruiser will see storms with no outside help. If something breaks, there is no race committee to send help for them. They must fix their yacht themselves with what they have left.
Now we are going to get into Jury Rigging and why Keel Stepped is superior to Deck Stepped for cruising.
When all Hell loose and the mast comes crashing down, one of two things is going to occur. Either the mast will fall over at the deck or the mast will snap at the first spreader. Most often, the mast will buckle and snap at the first spreader as this results from a cap shroud failure. The cap shrouds are under the most stress and are usually the first stay to break during heavy weather. When they break, the top of the mast becomes unsupported and the lowers become the new “strongest point” on the mast. Since the lower panel is supported by the lower shrouds, all that will be left of your spar will be the lower panel during a cap shroud failure as the top will come crashing down.
If all the stays fail on the mast, then the mast will fall over! On a Deck Stepped mast, this means that the mast will just fall over since the mast simply stands on the deck totally reliant on the rigging. A Keel Stepped Mast, by contrast, always has one point of contact above the mast step: the mast/deck interface, and therefore the mast can still stand without the standing rigging (but not in a storm, in a storm everything is bad), but in a storm, the mast will simply break and fall over to side at the deck leaving you a massive hole in your deck where the mast used to pass through. In very extreme conditions with slack rigging on a Deck Stepped yacht, the combination of a flexing hull, and severe pounding of the spar (imagine a giant wave crashing into your sails) a Deck Stepped mast can jump off the step and fall over just the same.
Both of these cases leave you with broken rigging and a problem to resolve. If you are racing, then the race officials will send help and all you need to do is wait, but if you are cruising, you are alone and no one is going to come for you! You need to fix it yourself and sail to your next port for repairs, and that rigging is called Jury Rigging.
The most common mast breaking scenario is where the cap shrouds fail and the mast buckles at the first spreader. Now your mast is much shorter, but you still have a mast to rig your sails to and to attempt to sail back to a port (or at least close enough to land to call for help).
Now, imagine that your mast is going to snap off at the first spreader! Which remaining mast length would you wish to have?
The single spreader rig has 1/2 of its mast left in the lower panel. The double spreader rig has 1/3 of its mast left in the lower panel, while the triple spreader rig has 1/4 of its mast left in the lower panel.
This is all you have to hold your sails up in the air to sail you back to shore, naturally, you would want the taller mast which means you would want to have the spar with a single spreader.
Since the points of contact introduce stiffness to the spar, another way of looking at it is having more points of contact means you can have a less strong mast as the strength is coming from the rigging instead of the spar itself. A triple spreader rig will be installed on a very limber spar, while a single spreader rig will be installed on a very stiff spar. You can’t just take off a set of spreaders before you go cruising to prepare for a misadventure. Likewise, a Deck Stepped mast will always be more limber and therefore will need to be even thicker walled to make it stiff enough to compare to the stiffness of a Keel Stepped mast.
They all break at the first spreader during a cap shroud failure. Having a longer lower panel means that now you have a taller mast to work with.
Keel or Deck Stepped, during a cap shroud failure, this will be your end result. The difference comes in the length of the lower panel between these two. If a yacht designer wants 3 points of contact with the spar, this will mean a single spreader Keel Stepped mast or a double spreader Deck Stepped mast. This also means that in a catastrophic failure situation, you have 1/2 your mast left or 1/3 of your mast left.
Let’s take things one step further in a horrible direction and imagine that the entire rig falls down. You now have no mast and (if your yacht is bigger than 30 feet) no way of raising your mast back up as the spar is just too heavy to manage on the deck of the boat. What do you do?
If you have a Deck Stepped yacht, you now have a sealed up power boat with no holes in it. If you have a Keel Stepped yacht, then you now have a huge hole in your deck. This is why large flow manual bilge pumps are important to have as well! On a Deck Stepped yacht, your only option to Jury Rig a spar will be to try and secure something to the step, but this can be a bit tricky. There really is no easy way to hold the bottom of your spar in place and it can slip out on you. A Keel Stepped yacht, on the other hand, has that nifty hole in the deck which will help hold things in place for you. Many people Jury Rig by slipping the boom into the hole and inside the remnant of the mast. They then rig up the short spar with any sails they have left and make their way towards a port for repairs. Others have used spinnaker poles for this same purpose.
Jury Rigging is literally “fixing it enough with what you have on hand”. You can see that there is no standard for what goes where or any rules about aspect ratio or sail design. After the catastrophe, you need to piece together what you can with what you have left. This is why it is important to try and salvage your broken spar and not just cut it loose and let it sink to the bottom. Out in the ocean, there are no more supplies so you need to keep everything that you have because you might need it later!
Having a Keel Stepped mast means that you now have a hole to help hold your Jury Rigged spar in, as well as potentially a longer lower panel since you won’t need as many spreaders.
It is not a good idea to worry about what you would do should your rig fall down because you will never be able to enjoy sailing. Every puff of wind will bring with it a gale of anxiety as you anxiously await that awful sound of metal buckling! Instead, plan ahead of time (before you buy your yacht) for what may come one day. Plan for the mast to fall and figure out what you would do if your mast breaks at the deck or your mast breaks at the first spreader. Have a plan and know what you would do, and then forget about worrying because you are prepared in the rare event that your rigging fails (because you read this blog and therefore know how to properly inspect your rigging and repair problem areas before the situation turns catastrophic).
If you are interested in pure racing performance and will stay close to shore, then you don’t need to worry as much about having something that will get you home (because you are never far from home). Enjoy your Deck Stepped Racing Machine!
If you are going to be cruising far and wide, then maybe consider something that will be strong enough to not break in the first place and something with low loads. If you notice, all the boats that I was able to find pictures of with broken masts jury rigged are racing yachts. This is for two reasons: in racing, you push the yacht to its breaking point, literally. Second, they all had high aspect ratio rigs which are also high stress rigs. One component failure and the whole thing came crashing down. When they jury rigged, they produced something that is low aspect ratio because the loads and stresses are much lower and their simple jury rig was able to support it. If you start off with a low aspect ratio rig on a strong Keel Stepped mast, you will have very little to worry about while you are cruising!
There really is no perfect rig, it’s just a matter of choosing one that works for what you need. If you are racing, a Deck Stepped mast will give you more adjustability and that will give you a winning edge against your competitors. If you had a Keel Stepped mast with a single spreader, you would become very frustrated as you would lose all the time!
On the other hand, if you are cruising, constantly trimming a deck stepped mast is a lot of work! There are plenty of other things to do while you are cruising, like fish or read, or sleep. Constantly trimming the mast will become a chore, especially on a long passage in good weather. It will become unnecessary complexity that will get in the way of cruising. We have been cruising full time for three years now (check out our adventures on YouTube) and we have a heavy cutter with a Keel Stepped mast and a single spreader. Having a cutter rig does give us an extra point of contact with the spar giving it the stiffness of having a second set of spreaders without the complexity. Our mast has the Mast Head, Inner Stays, Lower Stays, Mast/Deck, and Mast Step for points of contact. Should the cap shrouds fail, the inner stays might hold the mast up at 3/4 of the original mast, if not, we will be at 1/2 mast. We enjoy our passages from one place to another and feel safe in our heavy old boat. We do have some features that seem “high performance” such as our synthetic standing rigging and backstay adjuster.
While performance yachts have Dyneema rigging like ours, we did not do it for performance, but actually for simplicity. I added the back stay adjuster because it was easy to include in the new rigging. The backstay adjuster allows us to tighten the headstay for going upwind and ease the headstay for going downwind. How often do I adjust it? About once a month, if needed.
In cruising, you are either going upwind or downwind for a long time. You are not racing around a buoy where you have an unwind leg followed by a downwind leg in the same day (and in racing, many times during that same day). When we sailed through The Bahamas, we were going upwind, so I tightened the backstay once and left it that way until we set sail to cross the Atlantic on a downwind route which took months to complete (with lovely stopovers in Bermuda and the Azores). That whole time, the backstay remained eased as we were sailing downwind. In all honesty, the backstay has remained eased from 2018 until now in 2020, because we always choose downwind destinations, or wait for the wind to shift to make our destination downwind. This is what I mean when I say that a high performance rig is not necessary if you are planning to go cruising. The pace of sailing is so much calmer that a flimsy (and very adjustable) Deck Stepped mast is not necessary.
This is What Dead Rigging Looks Like
How do you know if your standing rigging is dead? There are many tiny tells that can indicate the level of health of your rigging and most of them are microscopic!
Thankfully this one tell is very small but not microscopic! (Though it is very small)
Do you see how the scum line at the base of the stay has slipped up just above the compression fitting? The scum line formed from years and years of gunk collecting the bottom of the stay at the top of the compression fitting (or swage fitting). The reason the scum line is raised is because the stay has slipped up and brought all the debris up with it!
The fact that the stay has slipped out of the fitting indicates that the fitting is failing and the stay is dead. Sailing on this rigging will lead to catastrophic failure when the stay slips out of the fitting completely!
Aside from corrosion issues, cracks, broken wires, or abrasion, which are all rather difficult to stop, this indication is rather easy to see and tells you right off that your rigging needs replacing!
Thermal Expansion and Rigging Tension
Thermal Expansion is the phenomenon where objects become bigger as temperature changes. In general, with most objects in the world, as things heat up, they also expand. Negative Thermal Expansion is reserved for those rare occasions where materials actually contract as they heat up; Dyneema is one such material.
On a yacht, the rigging must be perfectly tuned to hold the mast in column while withstanding the forces of the wind placed upon the sails and spars. This perfect tune revolves around the lengths of both the spar and the standing rigging. If one of them were to change drastically, so would the tune!
Unfortunately, all materials used in rigging have slightly different coefficients of thermal expansion. Where thermal expansion was the phenomenon of changing size, the coefficient is the rate of such change.
The issue comes down to mixing materials for the spar and standing rigging that will be changing size at various rates.
The most common spar material at the moment: Aluminum, has a coefficient of 23.1 x 10^-6 per Kelvin (or for practical applications “per *C"). This is to say that 1 meter (39 inches) of aluminum will expand or contract 0.000023m for every degree change in Celsius. This might not sound like much, but if you think about a yacht that will endure summers and winters, the temperature change can be rather drastic.
Imagine a yacht that sails in temperatures from cold winter days of 0*C all the way up to hot summer days of 40*C. That is suddenly a 40 K change (Each degree of Celsius is equivalent to 1 Kelvin). On a mast that is 19m tall (62 feet), that means that the change in length of the mast will be:
( 23.1 x 10^-6 / K ) ( 19 m ) ( 40 K ) = 0.017556 m = 17.56 mm ( 0.69 inches )
That is a pretty drastic change in size of your mast!
The next material to think about for a spar is wood, and while Sitka Spruce is the ideal wood for a spar, it is becoming ever harder to find good clear wood for the purpose. The next best wood for a spar, and the one that is becoming ever more popular as a wooden spar is Douglas Fir with it’s coefficient of 3.5 x 10^-6 per Kelvin (when parallel to the grain). The same spar now becomes:
( 3.5 x 10^-6 / K) ( 19 m ) ( 40 K ) = 0.00266 m = 2.66 mm ( 0.10 inches )
Significantly less change in length.
The last common spar material these days is also a very modern material: Carbon Fiber (Carbon Fiber Reinforced Polymers) with a coefficient of -0.8 x 10^-6 per Kelvin. The negative is an important part in this because that means that as the carbon fiber spar heats up, it also contracts!
( -0.8 x 10^-6 / K ) ( 19 m ) ( 40 K ) = -0.000608 m = -0.608 mm ( -0.024 inches )
This material is incredibly stable and barely changes size during the whole year, with its longest being on the coldest days and the shortest on the hottest of hot days, but the difference is less than 1 mm!
A changing spar length means very little if this change is not relative to something else, something like your standing rigging!
The most common material for standing rigging is Stainless Steel with a coefficient of 16.5 x 10^-6. Grade 304 and 316 both have the same coefficient which is why you don’t have to worry about which type is being used in your rigging.
On a spar that is 19 m tall, the cap shrouds will be roughly about 20m long (the beam of the boat is the only additional length in the stay, and this is run at an angle). Lets see how much the length will change over the same temperature variation:
( 16.5 x 10^-6 / K ) ( 20 m ) ( 40 K ) = 0.01254 m = 12.54 mm ( 0.49 inches )
This means that the steel rigging will expand almost half an inch over the years temperatures.
When you combine an aluminum spar with steel rigging, the variation is about 17.5 mm while the rigging is about 12.5 mm. This means that they will expand and contract together and only at the extremes be off by a few millimeters.
On a wooden spar with steel rigging, the difference would be 2.66 mm for the spar and 12.5 mm for the rigging. This means that on the really hot days, the rigging will be about 1 cm longer than the spar if the rigging was setup on the coldest of days.
On a carbon spar with steel rigging, the difference is a bit more drastic. The spar will contract by 0.6 mm while the rigging will expand by 12.5 mm. This means that if the rigging were tuned on the coldest of days, the rigging would be 1.25 cm too long on the hottest of days. If a boat has a carbon spar, then you can assume that the owner of the yacht is interested in performance and therefore would notice the horrible state of the slack rigging!
A newer material for standing rigging is UHMWPE, or Dyneema. This plastic fiber has a coefficient of linear thermal expansion of -12 x 10^-6 per Kelvin. Just like with the Carbon Spar, Dyneema also contracts as it heats up and expands as it cools.
( -12 x 10^-6 / K ) ( 20 m ) ( 40 K ) = -0.00912 m = -9.12 mm ( -0.35 inches )
The change in rigging length is rather dramatic, very close to the change in length of stainless steel rigging, except in the opposite direction. As steel expands, Dyneema contracts and as steel contracts, Dyneema expands.
When we pair these with spars, we see a rather drastic difference emerge!
With an aluminum spar: 17.56 mm expansion of spar and 9.12 mm contraction of rigging as it heats. This means that the difference between the two will be 26.68 mm ( 1.05 inches ) of difference!
With a wooden spar: 2.66 mm of expansion of spar and 9.12 mm contraction of rigging as it heats, with a difference of 11.78 mm ( 0.46 inches ).
With a carbon spar: 0.61 mm of contraction of spar and 9.12 mm contraction of rigging as it heats, with a difference of 8.51 mm ( 0.33 inches ) but going in the same direction.
The take away message here is that the components of your standing rigging will change as temperatures fluctuate. Some materials do not change much while other materials change drastically! Knowing which material combinations you have is imperative to properly setting up your rigging and having it perform the best that it can under most conditions.
If you fail to take into account the temperature fluctuations, you risk serious damage to your yacht. Think about it, if Dyneema rigging on an aluminum spar have almost a full inch of variance between the two, if you setup your rigging on a cold day everything will become too tight during the rest of the year! As spring comes, the mast will get longer and the rigging will get shorter. By summer, your chainplates will rip through your deck or the tangs on your mast will crack!
To prevent such a catastrophe, you simply need to take this change in length into consideration and setup your rigging on a hot day. Not necessarily the hottest day, but a hot day none the less. As winter approaches, your rigging will go slack and no damage will befall your yacht. If you wish to sail in these conditions, you will need to adjust your rigging, and then adjust it back in case you don’t revisit your yacht before a warm day appears.
If you have an aluminum spar and steel rigging, the two materials change length in the same direction and almost at the same rate, this means that you probably will never notice any issues with temperature affecting your rig tune.
If you have a carbon spar, you should have Dyneema rigging for the exact same reason as an aluminum spar and steel rigging. The change will be in the same direction and roughly the same rate so that the temperature range of proper tune can be wider than it ever could be on an aluminum spar.
