Carbon Fibre Masts

Discussion in 'Boat Design' started by Wynand N, Feb 4, 2005.

  1. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    Hi Everyone :)

    Carbon fibre mast and spars are probably the best available.

    My question; on a cruising boat, is the added expence of the carbon fibre mast worth it over an excellent alu one? They are pretty damn expensive.
     
  2. brian eiland
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    brian eiland Senior Member

    CARBON MASTS: Weighing up the difference.

    APPLIED ENGINEERING SERVICES LTD
    PO BOX 8445 AUCKLAND NEW ZEALAND
    TEL 64 9 8462006 FAX 64 9 8461432
    CIS 100354,2164 BBS 64 9 8492831


    CARBON MASTS: Weighing up the difference.

    Carbon fibre masts have entered mainstream yachting this decade in a similar fashion to kevlar sails during the last decade; and it is not over yet. There is both interest and confusion as to how much weight is saved and the implications to conventional yachts. Below is a small case study with some figures on a yacht currently in production to outline the sorts of savings possible and how this fits in with the rest of the rig. While the savings will vary from yacht to yacht, this at least gives some hard figures to those who are either interested or confused.

    Worldwide we believe that the majority of masts for non-production yachts longer than 100 feet are built in carbon. As mast builders get more organised with this new material it is relatively easy to see carbon used as widely as aluminium at Grand Prix level by the end of this decade. Somewhat tongue in cheek, it could even be argued that it is easier for a home builder to laminate a carbon mast section than it is to set up a home based aluminium extrusion plant. I am told that one of our top NZ Europe sailors uses a mast that he built at home (in carbon). Some of us now build fibreglass boats, is there any real difference? Some of our 'name' boat builders are actually now building carbon masts.

    The reason carbon masts are so popular is of course the saving in weight aloft (it isn't the price). This saving is especially popular with large yachts which generally speaking have relatively shallow draft and therefore relatively low righting moments. Carbon rigs permit these yachts to reduce draft and reduce ballast, possibly even saving money. On racing yachts they are equally popular, reducing weight aloft thus increasing stability and therefore they are able to operate with a larger sail plan without increasing displacement or draft. Conversely, on small yachts under 40 feet where draft is ample and racing is not at the highest level carbon is still too expensive for the moment.

    Our company Applied Engineering is currently designing parts of the rig for an Alan Warwick designed 60' for Matrix Masts. The owner and designer of the yacht have kindly given permission to publish these figures. The yacht will be used for international short-handed cruising and it is currently under construction. Both the hull and mast will be built in aluminium.

    The alloy mast section chosen is 340mm x 205mm and the rig has a masthead sail plan with three slightly aft swept spreaders. The mast section weighs 377kg bare aluminium. However, in carbon this weight could be reduced to 204kg; which is a good saving. The section weights below are 421kg and 248kg which reflects estimates for the addition of conduits, fairing, paint, bonding glue, local doublers, boxes etc etc.

    In terms of the total rig plan however, the saving gets diluted by the weight of the other items. As a result it is often better to use the cheapest carbon fibre available and to put the rest of the money into titanium tip cups, soft kevlar runners and maybe pultruded kevlar diagonals. The savings shown here are for the most common grade of so called 'Low Modulus' carbon.

    Below are some weights for comparison:

    Warwick 60 with Alloy Mast

    SUMMARY Warwick 18m

    Weight Height Weight Height
    kg m lb ft
    RODS 19% 147.0 9.809 324 32.18
    ROD FITTINGS 9% 71.6 8.444 158 27.70
    SPREADERS 4% 30.5 11.497 67 37.72
    SPREADER ROOTS 4% 27.8 13.673 61 44.86
    HALYARDS 2% 17.4 5.755 38 18.88
    SECTION 55% 420.7 11.091 927 36.39
    FITTINGS 5% 37.1 11.702 82 38.39
    WIRES 1% 10.5 11.239 23 36.87

    TOTAL RIG 100% 762.6 10.616 1681 34.83


    Warwick 60 with Carbon Mast

    SUMMARY Warwick 18m Weight Height Weight Height
    kg m lb ft
    RODS 26% 147.0 9.809 324 32.18
    ROD FITTINGS 13% 71.6 8.444 158 27.70
    SPREADERS 3% 15.7 11.544 35 37.87
    SPREADER ROOTS 4% 24.3 13.667 54 44.84
    HALYARDS 3% 17.4 5.755 38 18.88
    SECTION 43% 248.2 11.578 547 37.99
    FITTINGS 6% 37.1 11.702 82 38.39
    WIRES 2% 10.5 11.239 23 36.87

    TOTAL RIG 100% 571.7 10.644 1260 34.92

    The mainsail alone for a yacht this size might weigh 80kg. So the total weight aloft including mainsail, genoa, furler, battens, boom and spinnaker pole is substantially higher than shown above. The total weight could exceed 1150kg. On this basis the saving of 191kg is only 17% of the entire rig.

    It should be noted that these weights include savings from carbon spreaders, along with the carbon mast. Heights are approximate distances above DWL. It is easier to save weight in the boom and pole, but since these are close to the deck the saving is not of such great interest. This yacht will have a furling boom (another great new innovation which we have no room to discuss here).

    Hopefully these figures show that a substantial weight saving is possible with a carbon tube, but also we hope to put this saving in context with the rest of the rig. The important point to consider here is that neither the weight saving nor the cost of carbon fibre is extreme when you consider it as a percentage change in the whole rig, that is mast, sails, rigging, boom, pole, vang, furlers. No other part of the rig can have this much weight removed so easily. To underline that carbon is not an extreme option, it should be pointed out that super-yacht designers, builders and owners are usually very conservative and this is where most carbon is used. To the best of our knowledge, since the beginning of this decade only one of the super yachts built at Alloy Yachts and Sensation Yachts have had an alloy rig, all the rest have been carbon (five).

    In round terms the total cost of a rig such as this is approximately $280,000. This figure includes mast, boom, pole, hydraulic boom vang, spreaders, standing rigging, running rigging, mainsail, genoa, reacher (all dacron), 2 hydraulic headsail furlers. Of this price the alloy extrusion represents 377kg at (on average) $37 per kg. Thus the switch to carbon saves $13949. There would also be a saving related to the tapering of the alloy tube which has been ignored here. The additional cost of the carbon is likely to be204kg x $130 per kg. The carbon will need to be laminated and moulds built which can on average be assumed to total 1.5x the material cost. Thus the equivalent price for a carbon rig is $332351. The price increase is therefore close to 19% on the whole rig. This seems reasonable given the saving over the entire rig. Obviously, these figures vary from yacht to yacht, but we believe that they are reasonable for a yacht of this size. As builders start to make a range of moulds and a number of masts are built from each mould the prices will inevitably reduce due to competition and prices will also vary according to the manufacturing method. AES Ltd does not build masts and these prices are educated estimates which will vary from builder to builder. Recent increases in the value of the NZ dollar are likely to reduce carbon prices more sharply than alloy prices but this remains to be seen.

    Precisely what this means in terms of ballast varies considerably depending on the design of the yacht. We presume (potentially) that the carbon rig option for the 60' could eliminate 1000kg of its ballast or alternatively the draft could be reduced. The monetary saving in ballast is not included in the comparison above. Alternatively, the sail plan dimensions might be increased to improve performance by making use of the increase in stability. However, it is for these reasons connected with righting moment, ballast and draft that carbon is usually chosen. On super yachts the saving can account for several tonnes of ballast.

    There have been several carbon failures. The most unfortunate of these has probably been a well known European 125' ketch with two huge in-mast furling rigs. The yacht was built by a prestigious boat yard and the shock waves from this failure are still being felt. If a yacht is dismasted, it is generally reported more widely if it is carbon. This is not a conspiracy; just basic human nature and a fascination for the new or different. From time to time masts will fail for a variety of reasons just as people will find ways to crash cars or break crockery. From a safety perspective, whether the rigs are made from carbon or aluminium is of little consideration provided they are designed, built, maintained and sailed appropriately. However inevitably accidents will from time to time occur.

    It is possible to see that rod rigging becomes conspicuously heavy in the carbon rig weight calculations and the next leap forward will probably be the widespread acceptance of kevlar or maybe some other forms ofnon-metallic standing rigging. Given that the ketch La Poste raced the last Whitbread with Riggarna pultruded kevlar for all its transverse rigging (vertical and diagonal stays) this acceptance can not be too far away. Overseas, EPI style soft kevlar has already become widespread for runners and checkstays, and it is excellent for such 'running' applications. Combined with Titanium and 17-4ph fittings the rigging package weight can be reduced substantially. Aluminium masts have only been with us for about 30 years and it seems likely there will be even more changes in the future.

    So, carbon masts have arrived and we predict more developments to change the face of masts and rigging within our lifetimes.

    by C. Mitchell. Copyright AES Ltd. December 12 1994.
     
  3. sharpii2
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    sharpii2 Senior Member

    Hi Brian.

    Thanks for the article. I remember when I first heard of Carbon masts. It was during one of the BOC races during the late eighties or early nineties. The boat I remember was called Lady Peppernal and she was rigged as an unstayed cat ketch. Her main claim to fame, as I recall, was when she was rolled over, she came back up with both her carbon masts intact but her keel broken.

    From that point on, I was sold. It seems to me that the greater advantage of using carbon masts would be found in unstayed rigs. Here, the vast majoity of the weight is in the mast itself.

    I have been working on a design concept for years that would have an experimental rig that I invented. The rig, by its nature, calls for an unstayed mast. If I were ever to be lucky enough to afford to build this design, I would make the mast out of carbon. And the boom and the yard as well.

    Hopefully, by then, the secrets of doing it properly will be less proprietary and more public.

    Bob.
     
  4. PAR
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    PAR Yacht Designer/Builder

    Carbon sticks and rod rigging have no business on the typical cruising yacht. Cruising by it's nature will not feel the advantages of weight savings near as much as much high ballast to displacement designs used in racing machines. Rod rigging is generally the same equation, the cruising designs don't need to shave the last 1/10 of a knot out of the boat so equipped, nor could they not live with a few extra degrees of pointing ability. The cost alone should keep it well entrenched in the racing and luxury fleets for many years. Don't even think about trying to install a screw on masthead fly in this stuff. Not very user friendly materials and most cruisers require the craft to be rather user friendly.

    Large yachts do show a need, in reduced draft, windage, weight aloft, etc. but frankly those yachts are well beyond the means of the typical cruiser. In my humble opinion, any yacht not capable of traveling under an intercoastal bridge isn't a cruiser. Nor is one that draws so much water you need an offshore powerboat for use as a dinghy, just to make lunch at the local fish shack. These yachts are more about opulence, then the joy of handling a fine craft with your wife and/or family, bouncing down the seaboard for a summer cruise.
     
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  5. gggGuest
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    gggGuest ...

    In my mind I can hear your father/grandfather talking about how using anything as electrochemically active and corrosion prone as aluminium on a boat is such a bad idea...
     
  6. D'ARTOIS
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    D'ARTOIS Senior Member

    Correcto, in his grandfathers's time marine grade alu did not exist.
     
  7. PAR
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    PAR Yacht Designer/Builder

    What is a cruiser? How do most cruisers get designed? Equipped?

    A cruiser has a belly, a bunch of boat to drag around all the stuff you'll need for a cruise or to lazy to leave a shore. Spare alternators, fuel pumps, every filter on the boat, rigging, paint, winch handles, carb rebuild kit, back-up burners for the stove and all sorts of things that a racer wouldn't dream of weighting their yacht down with. The hull form will have it's beam drawn out toward the ends more, possibility shallower draft to get into cute little coves, the rig overly hefty, the sail inventory is much smaller, the engine bigger, hard dodger, or soft, rail nets, and underwear hanging form the boom vang to dry. How much is a carbon spar going to help this craft?

    It's bottom will get a cleaning once a year, not buffed before each race. It's sails will set on heavier gear and not near as well used as a racer. What advantage will be seen from using solid rod standing rig on this type of vessel?

    When you poke your keel into an unknown anchorage in a far away land with a need for repairs on this rig who in Belize is going to address your difficulty?

    A cruiser is a hearty yacht, capable of much more then any dedicated racer. It will have a low SA/D for working trades, a higher D/L for comfort at sea and can not take advantage of this very expensive outfitting. It makes little economic sense, for a boat that has trouble tacking trough 90 degrees, because of three year old sails, fouled bottom and a host of other issues typical of a cruiser to warrant the purchase of a carbon rig with rod draped over it. The advantages of using it is wasted in the inefficiency of the design, use and condition of the boat.

    Brien, in my grandfather's time the school teacher arrived at class on horse back . . .
     
  8. MikeJohns
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    MikeJohns Senior Member

    I agree with PAR's sentiments

    Having seen several unpredictable failures that the numbers said were fine, I would not recommend CF.

    One of CF tubes main problems is poor torsional strength.They also appear to have poor fatigue failure characteristics.

    Aluminium is repairable cheap available and an excellent mast material.

    As for weight saving only the mast lighter by around 40% with minimum section. However by the time you add the masthead fittings, stay and shroud fittings, spreaders halyards, doublers and tracks the total rig weight tends to go down by only 20%, with the sails aloft this % drops further.

    Carbon fibre properties vary considerably manufacturer to manufacturer, the homogeneity of the finished product is poor, predicted strength is often not achieved. If you build heavy to allow for the problems you are back to the weight of an alloy masted rig.

    Remember reducing the weight aloft leads to higher roll accelerations, higher dynamic loads, and a decrease in dynamic stability. Static stability is increased with a lighter rig but unless you are producing a racing machine the benefits are dubious and the designer can add a bit more ballast to compensate. The increased roll inertia from a heavier mast can make the difference between misery and absolute hell in rough weather. It's the mast that contributes most to the roll inertia.
     
  9. D'ARTOIS
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    D'ARTOIS Senior Member

    Fact is, you are right, and so is Paul. I have swallowed a lot of salt water, grey and green over the last 15 years, when I had to come home from the lost continent, forced by civil war and I was pennyless.
    So I had to take rides on everything that could float, from AC to charterboat in order to get back to my senses. For a family I sailed a very modern French production yacht, beamy, short keeled, down wind a complete nightmare- a carbon mast might have done her lots of good.
    One season I was bosun on an AC of 14 meters, a mighty ship that could even surf downwind - that we practised quite often coming back from the German Bight where we met those huge seas. Fantastic sailing. Well that ship had just an alu mast but the whole concept was very well balanced.
    She ended her life in the Minquiers on the Brittany coast, on the rocks.
    So I do not anymore believe in such things as latest designs of things.
    It is actual a bizarre story that the only materials that are advanced over the years is only to find in the FRP industry - Polymers. In metals almost no bloody nothing except for a few military alloys, those of Boron etc.

    The guy who knows best is Eric Sponberg. But if the factory produced just a bad lot, wha da ya know, as they say.
     
  10. Eric Sponberg
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    Eric Sponberg Senior Member

    Mike Johns said: "Having seen several unpredictable failures that the numbers said were fine, I would not recommend CF.

    One of CF tubes main problems is poor torsional strength.They also appear to have poor fatigue failure characteristics."

    Also, "Carbon fibre properties vary considerably manufacturer to manufacturer, the homogeneity of the finished product is poor, predicted strength is often not achieved."

    Unpredictable failures are common no matter what type of material. Certainly, on the learning curve with aluminum, there were unpredictable failures. And aluminum masts continue to fail every day, as do many things made of many materials, so it is poor logic indeed to condemn carbon fiber for this. Yes, you have to do your engineering properly, and without knowing the fine details related to the engineering, and to the manufacturing, whose to say what causes were in any given instance.

    Torsional strength and fatigue limits. If a CF tube has poor torsional strength and stiffness, it is because the engineers did not put it into the laminate. You cannot make a reliable CF mast without off-axis fibers (0/90 and +/-45). Properly designed and built, CF masts should have sufficient torsional strength and stiffness, and this is one of the beauties of composite parts--you can tailor the strength to your desired characteristics. In general, I always design my CF masts to have at minimum 60% unidirectional material, 40% off-axis, up to a maximum of 80% uni and 20% off-axis, depending on the nature of the design. As for fatigue, CF laminates are many times more fatigue resistant than aluminum. At 10^7 cycles, well-made CF laminates can retain 60% of their ulitmate strength while aluminum retains only 20% or less of its ultimate strength.

    Carbon properties do vary between manufacturers, and that is why regular testing of laminates is important. Poor quality laminates are not an option. The builders that I deal with take great care in the quality of their laminates and non-homogeniety is not a problem. Predicted strength can be achieved if your engineering is done properly and the builder backs up his laminates with tests.

    As you are probably aware, I am a great fan of carbon fiber rigs, and the article that Brian posted is certainly a good summary of cost and weight that is much appreciated. I think that sums it up nicely. Carbon fiber is a reliable material when well-engineered and fabricated, and so well suited to masts on cruising sailboats.

    Eric
     
  11. asathor
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    asathor Senior Member

    For cruising it seems the unstayed rig makes a lot more sense that the stayed rigs with all their failure points. I also do bot beleave that a good ships carpenter an a far away island would be unable to repair a CF mast. Sure it will weigh a little more, the epoxy color won't watch and it may have wood plug or something, but so what.

    The important question seems to be: how much weight do you gain when you go to an unstayed mast?
     
  12. Eric Sponberg
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    Eric Sponberg Senior Member

    In my past experience, I have found that the trade-off of weight and cost of a free-standing cat-ketch rig vs. a conventional sloop rig seems to be at about 40' Loa. That is, above this length of boat, a carbon fiber free-standing rig (no rotation) is cheaper and weighs less than stayed aluminum sloop rig. Below this length of boat, the stayed aluminum sloop rig is lighter and cheaper.

    On Wobegone Daze, the Freedom 38 on which we built a new carbon fiber wingmast free-standing rig, the main wingmast (forward, taller mast) weighed about 280 lbs. The after mast was about 30-40 lbs lighter as I recall, but I would have to check. These are both lighter than the weights of the original fixed free-standing masts supplied by the original builder (TPI) which were about 310 lbs. each. Therefore, in this case, we ended up with both a weight and performance advantage over the original design.

    Eric
     
  13. brian eiland
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    brian eiland Senior Member

    Cruising Sailboat Needs

    This response in relation to 'cruising sailboats' is one of those honest self evaluations, as is this one by Bob Leask, "A LIVEABOARD CRUISER FOR THE REAL WORLD" in the forum posting on 'motorsailers'. I won't bother to repeat some of his observations here, as this is a discussion of carbon fiber mast. However for those cruising oriented you might pay a visit to this other subject thread at http://www.boatdesign.net/forums/showthread.php?t=4499&page=1&pp=15
     
  14. D'ARTOIS
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    D'ARTOIS Senior Member

    Brian we are in a position where all the parties comment's are justified, although if I have full confidence in a certain supplier I would opt for carbonfiber if pricewise acceptable. The problem is that we are too **********traditional.
    I have an idea, slowly ripening to use for my next boat a mast of carbon - titanium. That means a titanium inlay of max 1 mm thickness of a specific Ti alloy and that in combination with an outside reinforcement of Carbon. I have a racing bike made that way that weighs only 6 kgs. Carbon bonds extremely well to that titanium alloy I have in mind; and the big advantage is that the titanium and carbon do not interact. No galvanic emission between both materials. The result will be an immense stiff mast, the compressive strength of that alloy is 4 times that of sst 316 LL - it is just theory now, I have to construct a mast section to check the weight. That is actually the only question that puzzles me.
     

  15. Raggi_Thor
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    Raggi_Thor Nav.arch/Designer/Builder

    For smaller boats with fractional rigs the carbon spar can be more flexible in the top, so you can carry more sail in "gusty" conditions. I think this is the most important issue for me. See also what Steve Thompson writes; http://www.tboat.com/sport-boat.html

    Here are my numbers for a smaller boat:
    Carbon spar: 1400Euro
    Alu spar: 800Euro
    Standing and running rigging, boom etc: 900Euro

    Total for Carbon is 2300,- and for Alu 1700,-.
    This is a small difference compared to the whole boat, in my opinion.
     
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