Why do masts keep breaking?!

December 6, 2007 Construction, Design 28 Comments

At every international event in the history of FW racing, there has been a plethora of masts buckling under the high-downhaul loads and vicious air-temperatures that high-performance racing gear is put through. Brands don’t even need to be named because there isn’t a company on the planet who hasn’t had a warranty claim for a broken mast although some have copped more of the flack than others.

Is it because of the design of the masts? The shape of the sails? The materials and procedures used to construct the masts or just the incompetency of the sailors who leave them fully downhauled in the sun that is causing the slaughter of 100’s of masts a year?? My own personal opinion is that it’s a combination of all these factors but I believe that at least 50% of the breakages could be prevented by changing the construction methods of masts and also upgrading the materials used in the production of 100% carbon racing masts.

Looking at the masts I have used, broken, repaired and kept over the past few years and from discussions with my father who has done most of the repair-work on these masts, we have come to the conclusion that the general (as a general guide, there maybe slight differences between brands) construction of the majority of 100% carbon racing masts is:

  • INTERNAL-LAYERS: uni-directional carbon wrapped circumferentially
  • MID-LAYERS: uni-directional carbon running longitudinally
  • OUTSIDE- LAYERS: uni-directional carbon wrapped circumferentially

Masts rigged in modern race sails receive high tension/compression forces on them through the application of downhaul, rather than simply being bent from the middle as in an IMCS test. The outside layers of the mast, which in the above construction have no carbon fibres running in the direction of the tension/compression forces, are susceptible to cracking, as the strands of the outside circumferential wrap can separate from the mid-layer longitudinal wrap, which causes the mast to solely rely on the mid-layers to take the full force of the tension/compression forces…. CRACK! BANG! SNAP!

In this construction there is nothing to handle torsional forces on the mast. When a mast is under load, there is tension on one side and compression on the other side; in addition to that there is torsional forces. The fibres usually aren’t constructed in the right direction to deal with the torsion!

If there was a different construction layup that used longitudinal threads on the surface, allowing the fibres to run in the same direction as the loads on the mast when it is fully downhauled inside a sail, the mast would be much stronger. This might cause the mast to be slightly stiffer, but superior in strength to the original construction. Surely there could be ways to deal with the extra stiffness or a different layup in the same concept which wasn’t as stiff?

There appears to be a general trend in windsurfing to use uni-directional carbon to build the carbon parts of our gear. Most likely because this type is cheaper, easier and more readily available. The more expensive cloths, such as 200g parallel weave (similarly used in Boeing’s 787 Dreamliner) aren’t popular in windsurfing product construction – probably because of the price increases occurred and also because when Boeing started building their planes there was a worldwide shortage of carbon (although this has somewhat subdued in the last 12 months). This product has also jumped in price by 300% most likely as a result of these new passenger plane’s coming into existence.

This construction idea might not be the perfect solution, but thinking about it is a start. I’m not naive enough to think that a simple design change will not make a considerable difference to the end consumer price of the masts and also play a role in further making manufacturing and distribution a little more difficult with an added price and the other costs/time involved with researching/designing/implementing/paying for/ a new design. Hey, I’m not a windsurfing company; just a person who hates reinforcing his BRAND-NEW masts all the time to stop them breaking.

I’m interested to hear what people in the community think. There is always going to be a two-way street with cost of manufacture (end price = $$$) versus material quality/reliability in any consumer product, but I am certainly a guy who would be happy to pay double for my masts if they had double the lifetime on the water.

Join the discussion 28 Comments

  • changer says:

    I see there has been some discussion about this on forums about before:

    Have you ever used X6/X9 masts Sean, sometimes there is small cracks circumferentially around the mast near the ferrule, often the mast breaks after these cracks appear. interested to hear what you think if you have seen this problem??

  • formula_guy says:

    So many masts broken and what to do about it? I think its the companies not giving warranty about it and not changing about the construction. In Rhodes in 2005 I watched guys break 10 masts in a day, but the teamriders have many masts to use. what about the normal guys? we can’t afford this shit. something must be done. i like your article.

  • Sean OBrien says:

    @ formula_guy – Hmmmm, I didn’t write this article in an effort to try and bag out certain brands about their mast failures… actually the opposite!

    I am well aware of masts breaking back in 2005. Wow, hundreds in total I imagine. But the companies that had the problems stepped up to the plate and brought out a new mast that was great the following season. I still have quite a few of the newer version masts from 2006 and they’re without a doubt the best masts I’ve ever used (you already know what brand I am talking about so I don’t find it necessary to say it).

    I wanted to write this article because it seems that despite there already being some great masts out in the market, occasionally some brands go backwards and start building them cheaply/poorly and have the same problems. It seems to be a relatively “no-brainer” construction error that is causing these problems.

    @ changer – I’ve seen the cracks. Mostly on RSX masts but these are really easily fixed with a single wrap of uni-directional (longitudinal – which is transverse to the direction of the cracks) and then a layer of plain-weave which gives it basically a circumferential wrap without making the mast too stiff. (ie, if you used circumferential instead of plain-weave you would have the same problem that caused the cracks)

    The problem with these masts is anything you try to stick to it is going to delaminate, so to get a good enough bond you first clean the surface with acetone and soap and then vacuum bag the carbon layers on. When finished, heat cure it around the reinforced area for extra strength in the bond.

    Easily fixed. The masts I have done this to have lasted years after the cracks even with heavy sailing.

  • Thanaish says:

    Sean, thank you very much for these posts.Lot of information and deep analysis . Is there any plan for future post about extenders , bottom and top like these from Severne ?

    Thanaish , Greece

  • Sean OBrien says:

    @ Thanaish – that’s not a bad idea!

    I was actually thinking to write an article about how to build your own extendors as they’re relatively easy to construct.

    I currently use extendors on pretty much all my sails with extension over 20cm. Wouldn’t go back to using long extensions for ANY reason.

    I’ve tried the North and NP extendors and found them both great, but seeing as the sails change luff-length from year-to-year I ended up needing a few too many of them so I’ve started making them out of broken mast pieces (hooray! finally a use for broken masts!).

    I haven’t seen/tried these Severne tip-extendors however. I’m intrigued as to how they attach to the mast – I assume its a female end that slides over the existing mast? Usually the luffpocket is very tight at the top of the sail…wonder how they fit?

    Will try and have a look at one next week when we have the Oceanic FW Championships here in Brisbane (that I’m organising) and there’ll be quite a few Severne guys competing including designer Jesper Orth.


  • Sean

    I think unidirectional carbon fiber offers the best strength to weight ratio. When this unidirectional material is prepreg, then it is as good as you get. It is not so easy to work with. From my experience, woven materials are much easier work with but they do not have as good strength to weight ratio.

    There is another consideration which is "tack and drape" There are the ways to describe how easy a material is to work with. Woven carbon fiber has much better tach and drape than unidirectional carbon fiber. I think Boeing is going for consistency over optimum strength to weight, They will probably autoclave the parts and get a better strength to weight, but not as good as unidirectional will yield. Look at the Stealth planes… not a gram of woven materials there… of the carbon fiber helicopters… no woven material there except maybe at the ends of the blades or other joints in the craft.

    For the most part, I have always considered woven carbon fiber is more for looks but not so good for strength to weight properties. With a heavy clear coat it looks like jewelry… really beautiful material

    Moat sail name brands compete with each other on mast weight. They are always making things lighter and lighter. Most mast are built with weight and PRICE in mind. Really, a name brand will choke on even $1.00 USD more in price. They are super price sensitive! The bigger the name brand the more they are price sensitive. So, when you combine trying to get the weight down and the price down, you have the resulting compromise.
    If you added lets say 15% more material weight to a mast… maybe even 20%, the mast would be much tougher, but they would also cost even more. Really, you could off axis a lot of fibers so the stiffness would not increase.
    Your idea about putting the longitudinal fibers on the surface has been tried, but there is nothing to keep the fibers bonded to the fibers underneath, so small delamination’s begin to occur and increase.

    Then, your thoughts about torsional loads, they occur in concentration just above the boom clamp on area, and most mast manufactures add extra material in this area. But there is not so many good reasons to put the plus minus 45 degree or other off axis layers through out the mast to counteract torsional loads exclusively… though there may be good reasons to do this as more of a homogenizing factor… blending the strengths of the layers… 0 degree to 45 degree to 90 degree… that might be a good thing (I will try it in the next week on some lay ups!!)

    After increasing the amount of material comes the process. It is so important to design a lay up schedule that can be repeated reasonably easy. There in are trade secrets…
    A few other things to consider are the different modulus of Carbon fiber. Standard modulus is what most things are made from. Lets use a fictitious number of $15.000 USD per pound for Standard modulus carbon… well then, Intermediate modulus will cost about $75.00 UDS per pound. So you see, the price ratio is not so good.
    All in all, sure, mast could be made better but when the manufacturer is trapped against the price the market will bear, then there will be compromise..

    In closing, it is good to see someone really thinking this through.

    Take care


    Don McCormick

  • Andreas says:

    Don is definitely the voice of experience in all of this, having been on the manufacturing side of things for both booms and masts (and all kinds of cool stuff made from carbon fiber). A few observations – all anecdotal evidence, but hey, we won’t really get the data to go beyond that…

    Sean – you’re suggesting going away from purely uni-directional fiber orientation layups. The filament-wound masts (such as the Powerex 100% carbon z-speeds and its rebadged derivatives such as the Sailworks Speedstick) should go quite a ways in that direction. As a Sailworks user, it seems that their breakage rates are higher than the uni-directional layup of the Sailworks Lightstick (made in Italy, with a process very much the same as that of the other big guys).

    That said – the Speedstick was a pretty reliable mast (as far as 100% carbon goes); the Lightstick, however, has almost unbelievably low breakage rates (I see a lot of those used, and I’m apparently not just lucky with my record). Very clearly much lower than other brands who come to play with us in the Gorge (where Sailworks is dominant).

    So what makes the Lightstick durable, given that other masts, made in the same factory, for other brands, break at much higher rates? It’s not just the sails (users of other sailbrands who get tired of buying new masts all the time report increased longevity when substituting Lightsticks, so it’s not just a matter of sail design, even though our sails seem to be less hard on the masts).

    I believe that it’s a matter of the specs Bruce gave to the manufacturer. There’s a bit more carbon here; I’m sure that if you check first generation X9’s against our masts, they were lighter. They also snapped a bunch. Go figure. I’m not privy to the kind of materials choices that were spec’d into the mast (which grade of carbon, etc.), but just the extra material is certainly evident. And wouldn’t you know it – the recent NP’s are much closer in weight, as are the recent Gaastras and Maui Sails masts.

    If you read through Don’s comments, it’s pretty clear that he would probably agree – the specs given the manufacturer by the buyer (i.e., the sail brand) are probably the most important determinant of longevity.

    But in all of this – these are very high-performance composites products. We could easily get them built to aviation-grade quality requirements – but then we also couldn’t afford them. So it’s always a tradeoff between competing factors such as perfornance, reliability, and cost. Find a supplier whose idea of where that tradeoff should fall matches yours, and you’ll be reasonably happy.



  • Brad says:

    Interesting stuff from Don and Andreas. Do you guys work in the industry ??

  • Ian says:

    I note that many manufacturers increased the weight of their 100% carbon masts a couple of years ago to reduce the number of breakages. I think North were one of the first to go this route.

    An additional problem I think with high performance race sails with extreme downhaul tensions is the fact that pressure points occur due to the cams pushing on to the mast. I think under load these pressure points do not allow the mast to have an even bend, but at times differing tensions in the section between cams.
    I think this is also a major factor for mast failure.

  • Sitka says:

    Thanks, for the insight and continuing the saga of this situation. Let it be said that over the last 5 years my experience has been that I have never broken a Fiberspar or Powerex 520 or 550 when I’ve combined a 75% bottom with a 100% top. I think this is a good approach and should be utilized by mast manufacture. The added weight to the bottom is much less noticeable than a full 75%.
    Unfortunately the ability of sailmakers to rebrand and thus generate a litlle more revenue for themselves has removed responsibility from mast makers to do the best for the end user and moved the failue recovery to yet another level of redirection that often expires before the $1000 spent is considered not worth persuing. If I was a Neil Pryde guy no big deal I’d have come to terms with THEIR system, But I will not buy a Neil Pryde mast or a Mauisails mast or a Gaastra mast or a North Sails mast or a Severne mast or a Tushingham mast or an Ezzy mast or ….
    you get the point.

    All these masts may be perfect for that year sail of that sail cutter. But they will not be the same mast in a year or two. And you can forget about timely warranty in evey case 8 months hence once a regional shipping container is used up. Neil Pryde excepted with their huge volume but their record speaks for themselves. According to that model everybody should keep a few spare 550’s, current year unopened for race day, yeah, that makes sense.

  • Brad says:

    There’s some interesting discussion surrounding NP’s warranty policy on X9 masts going on at the Starboard Forum.

    Here’s the link:


  • Jason says:

    Hi Sean, Phenomenal thing you’ve started here! Keep it up!

    Quick question about the collar that wraps the top of the bottom piece of the mast. My new North Platinum 460 has started to split at the bottom edge of the collar after only 6 sessions. Unlike the severne Alloy collars, mine looks to be plastic.


  • Sean OBrien says:

    @ Jason – I haven’t seen a North mast up close and personal enough to know what to recommend…

    There’s a post on the Star-Board forum with some guys having a similar problem with the Severne masts (although their collar appears to be aluminium rather than plastic) – check it out:


    Otherwise, I’d be taking it to your dealer to see what they say. Is there even a North dealer here in Aus??

  • Jason says:

    Hi Sean, Thanks for your reply,
    I’ve just been on a three day internet mission to find out all I could about the problem. Turns out that after speaking to a number of different people. The issue of splitting or cracking collars is nothing new. I believe our Hungarian grand master knows a thing or two about it as well.

    I was told it’s not a common problem, however on the odd mast, even at times on the odd batch of masts! Problems sometimes arise. The general census of opinion is the resin or sealant used between the collar and the mast is either applied too heavily or too sparsely, “ultimately unevenly”. Needless to say that unevenness of glue or resin results in unequal stresses being sustained by the thin alloy collar as well as allowing direct contact between the alloy and carbon which can result in corrosion and weakening of the collar.
    This corrosion can not possibly be what happened with my mast as it was only used 6 times. As Ola H said on the star-board forum, it was more a case of simple geometry in my case.

    I would be interested if some of the guys who have first hand experience in the designing and manufacture of masts could share their knowledge with us on this issue.

    My Singapore based North supplier heard my case and got onto North head office in a flash. Had confirmation of a replacement mast in less than a day! Lucky me huh? oh BTW, Windsurf and snow in Sydney do stock most North kit. The high end race stuff is not imported to OZ as stock, but can be specially ordered i’m told.

    Thanks for the wicked site,
    am learning so much here
    @ CARBONSUGAR keep it up.
    Loads of the Greek crew are reading your stuff too!

  • steven says:

    any idea why the manufacturers haven’t come up with a pre-curved mast , instead of a straight one.
    such a banana mast wouldn’t need any downhauling to stay in the wanted curve, you can also shape it in a stiffer drop shape and building in lateral flex with minimal torsion .

    what do you think?

  • John_O says:


    Below is an extract from the Formula Windsurfing Class Rules which prohibits pre-bent masts:

    “F.1 MAST
    (a) The spar at any cross section normal to the mast axis shall be circular and of uniform thickness.
    (b) Pre-bent masts are prohibited.
    (c) The bending curve of the mast shall be equal in all directions”

    The design of modern FW sails with the wide luff sleeve and cambers requires high downhaul tension for a number of reasons including:
    – improving the stability of the front section of the sail to resist backwinding and also to lock the draft in position making the large sail friendly to use in high winds;
    – tensions the sail fabric along the leech;
    – opens the upper leech section which helps to reduce the vortex or induced drag near the head of the sail;
    – keeps the luff sleeve smooth when the mast flexes

    Just my 2 cents

  • Sean OBrien says:

    @ John_O – all good points, but you left out…

    …”how the heck would I fit this pre-bent mast into my car” ??


  • Land says:

    Sean congrats for your article.
    I would like to share my personal experience and feelings about this matter.
    I run windsurf races for almost 30 years now, the same time I also compete in road bicycle and triathlon events and what impresses me the most through all this years is the complete opposite direction that carbon took in those different sports.
    While in windsurf we are experiencing breaks, cracks above it all “lack of confidence” in our carbon stuffs ( not forgetting the booms breaks too !!!) the carbon bicycle market had grown significantly throughout this years. Carbon bikes is light, reliable and thanks to mass production is becoming sheaper and sheaper every year.
    In my opinion, the problem lays in the eyes of the windsurf executives. While bike market have professionilized generating millions in sales, sponsorship and media worldwide, windsurf, in general, but specially FW is still an amateur sport.

  • Sean OBrien says:

    @ Land – I agree. I also cycle, and recently bought a Trek Madone full carbon bike (figured if its good enough for Lance Armstrong, its probably good enough for me!).

    The workmanship that goes into a carbon bike frame (even the work that goes into carbon drink bottle holders) is quite astonishing.

    But I guess you can have that level of quality when you expect to sell 500,000 units of drink holders instead of maybe 1000-2000 masts. Bike “parts” are cheap, but framesets are still not (retail around US$4500 for my bike), so I guess all products still have to pay for the R&D that goes into their products and their teamrider’s salaries.

    I still get a lot of emails from sailors here in Australia, asking what brand of sails they should try this year and whether or not the masts will break. What can you tell them? Every brand is in the same situation (almost)… I have trouble selling second hand sails because I don’t want to sell the masts with them; you need to have so many spare masts to do the tour these days :(

  • soffio63 says:

    Hi Sean,

    Even if I know you don’t use North windsurfing sails, I contact you about a Warp issue for a simple advice.

    I’ve purchased a second hand 2006 North 9.0 slalom WARP and I have rigged it with a compatible 520 / IMCS 32 mast.

    I’ve noticed this sails is very physical and from recent races I came out really exhausted !

    I regularly use North formula and free-race sails with their recommended masts and I valued NS sails for their soft feeling but I feel this sail (9.0) is really hard to drive & control when wind rises.

    I wonder if this depends on using a compatible (maybe stiffer) mast than original 520 North (anyway, always IMCS 32).

    What do you think if instead of using recommended 520 / IMCS 32 mast I will use a softer 490 mast (or a mix of 520 bottom and 490 top) ??

    Thank you in advance for any help.


  • JW says:

    Not Sean here but anyway:

    Why not use the recommended mast firts? Is is not all in the IMCS allone. North need more topfelx masts and it may be that you have a similar imcs mast but one with less topflex or with a stiffer bottom…. Overall it is the same imcs as reccomended but the curvature is probably not the same as in the recommended mast, my guess.
    So my idea would be first to try the recommended mast before doiing something that is out of the box.

    Good luck and let us know here what you find out.

  • PH says:

    Hi Sean

    How do you build an extender from pieces of broken mast?

    Having a few lying around in my shed I would love to put them to a good use.

    Congrats on this excellent website!!


  • .g.e.o. says:

    Hi all,
    just found this now, it’s very interesting. I have something to share.
    I use Maui Sails and have been rigging on the same SRS100 460/25 from 2006 during the last 3 seasons; it’s a very light mast, about 1.6 kg. This season I decided to get another identical one as a backup; so I got a new one, much heavier (1.9 kg). The manufacture told me they did so to make it sturdier. I rigged it an half dozen times, then one day BANG it crashed while I was going out at the beginning of a session, luckily just about 1/4 hour swim from shore.

    I looked at the broken mast and asked to the manufacturer how the layup was made and how was reinforced. They told me the layup is, inside to outside: spiral tape; longitudinal fibers; 90° fibers reinforcement; spiral tape. So it seems to me that the added reinforcements, those that brought the weight up from 1.6 to 1.9, have been put on the outside of the 0° fibers.

    Now. If one reasons about how stresses go in a mast (concentrated on the backward side of the mast where there are combined effects of flex + downhaul compression) it’s easy to understand that the mast will easier break on the side looking towards the sail body; and that it will break because of compression; and that 0° fibers will tend to go back to their ‘un-stressed’ shape , which is ‘un-bent’: straight. Think about the geometry of the system, this will cause fibers to implode towards the inside of the mast.
    This seems to be confirmed by what one sees looking at a broken mast: you usually see broken 0° fibers bent towards the inside of the mast. Look at the pics at the top of this page. I see exactly what I’ve found on my mast: little if any reinforcement inside, broken 0° fibers bent towards the inside, thick 90° reinforcement outside… right where it is 100% useless, as it should rather be INSIDE of the 0° fibers to prevent them from bending inside and implode destroying the mast!
    Now I am sure that use of better quality materials, carbon cloth in first, is the really good if expensive solution; but personally I’d feel much safer by knowing that 90° reinforcements are layed up inside of the 0° fibers in my mast. Maybe I am wrong?

  • […] you’ve been sailing FW for a few seasons then no doubt you’ve broken a mast at some point or know someone who has. Ever wondered what you could do with the broken pieces? With […]

  • TG says:

    I can agree with Andreas that the Sailworks Lightstick is stronger than other masts. I’ve been using a 550 for years, on another companies sails, and it’s been rock solid, meanwhile I’ve broken many other masts. It definitely is thicker and stronger, IMO. Unfortunately, the shape isn’t the best for the sails I’m using, but since I’m not racing anymore who cares.

  • Glen Gardner says:

    I have a Powerex Z-axis Wave 430 40% carbon. It has a criss cross pattern on the outside.

    One of the outside panels of carbon fibers (4″) is peeling away about 1/3 from the top of the bottom section.

    Can you tell me what type of glue to use to fix this, or is it even necessary?

    Thanks, Glen

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