Can I build 50' free-standing masts out of composite?

Discussion in 'Fiberglass and Composite Boat Building' started by Seafarer24, Aug 15, 2011.

  1. Seafarer24
    Joined: May 2005
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    Seafarer24 Sunset Chaser

    I'm looking at a Freedom 40 with no rig or sails. New carbon masts are ~$20k each and I'd need two. Can I build these myself out of composite? I would like to make it a "junk" rigged boat so I can easily build the sails myself.
     
  2. Landlubber
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    Landlubber Senior Member

    ...of course you can, have a gander at some of the winding methods of tubular construction, but there is no need for foam inside of course
     
  3. Eric Sponberg
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    Eric Sponberg Senior Member

    Seafarer,

    If you are really good at composite lamination and have a good shop and all the equipment, you might be able to build a mast or two. In my opinion, you will spend more than $20K per mast to do it. In fact, $20K seems a little light to me and for a Freedom 40, I would expect a more realistic price of $38-40K per mast from a professional mast builder who at least has all the proper equipment. And that is just for the masts--there are also the booms (if not a junk rig--$5K-$10K each) and the sails ($5K to $10K each) to furnish.

    For some additional insight, see my article on the state of the art of free-standing masts on my website: http://sponbergyachtdesign.com/StateoftheArt.htm. Go about halfway down where I talk about construction methods and techniques.

    I hope that helps.

    Eric
     
  4. rxcomposite
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    rxcomposite Senior Member

    While I may sound patronizing, Eric is one of the leading experts on free standing mast design. If you are into design mode, read also his article in PB magazine No 72 August/Sept 2001 "Factors of Safety". If you are feeling hands on, ask for a reprint of "Advanced Composites in a Simple Shop" PB 39 Feb/Mar 1996. Something about a free standing mast.
     
  5. BATAAN
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    BATAAN Senior Member

    Junk rig with its heavy yard and several battens puts a constant rapping and tapping on the surface of the mast and may cause delamination. Chinese lug is quite heavy for the sail area and halyard loads can get very high and halyard crane/block is prime point for failure. Luff parrals cut into mast unless greased. Recommend spruce solid or bird's mouth construction hollow wooden mast instead. Unstayed is for boats without great initial stability or excessively large sails, in other words easily driven not-too-wide hulls.
    Stiff boats need shrouds, especially with junk rig due to high inertia loads when pitching hard. This can build up a harmonic and break the mast off at the partners. Happened to me once in an 18' boat with junk rig, not the one pictured.
     

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  6. Seafarer24
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    Seafarer24 Sunset Chaser

    I don't need the worlds lightest, most advanced masts- just masts that won't snap off. I don't need carbon-fiber. I was thinking more along the lines of wood and fiberglass. Hopefully, a combination of strip-planking and double-diagonal layups laminated over a removable jig, or at least partially removable. Hell, aluminum would do it if I could find light poles or flag poles the right size. I've been aboard the original Freedom 40 (formerly Santa Margarita, currently Modesty) and its aluminum masts were holding up just fine.

    I'm not dead set on the junk rig, but I do prefer it.
     
  7. Eric Sponberg
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    Eric Sponberg Senior Member

    I recommend that you buy a copy of the book "Practical Junk Rig" by Hasler and McLeod. It covers all aspects of design for the sailplan, sails, and rigging, as well as building hollow tapered wood masts. The authors admit to not being engineers, but they simply report on design and building guidelines that have worked for them.

    Eric
     
  8. Bruce Woods
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    Bruce Woods Senior Member

    Yes, you don't need the most expensive highest tech solution. In Australia Lexan (Australia 2 fame) designed an unstayed schooner called the Revolution 38, from memory. I'm pretty sure the masts were low tech glass built in two pieces split fore and aft and riveted on the join. Sure it wasn't the most expensive solution, but it worked. It is a far better solution than going with the junk. People seem a little precious these days when specifying high tech solutions rather than appropriate tech. Geeze its a cruiser.I'm sure you could build spars from strip plank, glass and epoxy pretty cheaply. Price sails from Taskers in Thailand for example before you decide to make them yourself. I don't want to start aflame war but the world of rigs has moved on a lot since Junk rigs were in vogue. Regards
     
  9. Steve W
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    Steve W Senior Member

    Chris Whites original 54ft Juniper trimaran had very simple unstayed masts built out of wood,they proved to be a bit too bendy for the immense stability of a 30ft beam tri but never failed,would no doubt be fine on a more tender boat such as a mono. There was a story on the boat many years ago in wooden boat mag that showed the construction. For anything but a race boat carbon spars seem like a giant waste of money to me and some of the free standing masts are not as light as you would expect from all the hype.Many years ago i wanted to build a Baelstron rig and looked into a raw tapered carbon tube from a Freedom in the low 30ft range,i dont remember now but i do remember it was about $15000 and about 400lbs which seemed overly heavy to me. I also looked at buying a 40ft cat that had flipped on lake Huron some years back (killing both crew) the boat had a 60ft carbon wing mast which had used a Francespar aluminum wingmast section as a mold, the carbon mast was heavier than the aluminum one, i considered buying the boat without the mast but it it was too badly damaged to be worth fixing.
    Steve.
     
  10. Eric Sponberg
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    Eric Sponberg Senior Member

    Steve,

    Your stories are interesting, but I think they illuminate one thing fairly well, which I have seen time and again in my mast designing experience: It is very easy to build masts wrong, and those examples reveal that the builders didn't really know what they were doing. A carbon mast for a 30'+ boat should not weigh 400 lbs, and I wonder at what time frame that example was. The early Freedoms were built by TPI, and they did not ever build masts for other boats. Freedom was sold eventually in the mid-1980s, and the masts were subcontracted to other builders--Freedom itself did not have the knowledge or expertise to build their own masts, and likely would have 1) given a cursory quote with incomplete information, or 2) would have put you in touch with their mast builder at the time, who would have given you a more complete quote based on better design information. Note also that the best known balustron rigs of that era were built by CarboSpars in England, known for being way overweight, and they were licensed to ForeSpar in the US, who similarly built them very heavy, in my opinion, way too heavy.

    As for the carbon wingmast built over a Francespar aluminum wingmast, again, if the builders knew what they were doing, the carbon mast would have been lighter. Typically, a carbon tube mast of equal section size and wall thickness will be about 60% of the weight of its aluminum counterpart, and stronger to boot, with about the same stiffness. If, as a builder, you cannot achieve something close to that weight savings, then you really don't know what you are doing.

    Mast are highly loaded engineered structures. To get the most out of an expensive material like carbon fiber, you can't just lather up a tube and expect it to work. Every piece of fabric that goes into the mast is precisely engineered to its place, based on its width, ply thickness, length, and weight. All the pieces of fabric together make up the whole mast section which is sized to the strength and rigging arrangement of the boat at hand, and tapered appropriately for the optimum bend for a free-standing mast, or for column rigidity for a stayed mast. Every section of the mast, every foot along its length, is engineered to these parameters and the lay-up schedule drawn accordingly. The laminating process is important as well, whether wet lay-up or prepreg, so the timing of the fabrics going down and the type of cure and post-cure have to be specified and directions followed diligently.

    I admire the desire of many people to contemplate building their own carbon fiber masts, but they are not easy structures to build. Failure of a mast can be lethal in many ways, and so it is not place to skimp, and it is also no place to make the structure too heavy since it often affects the stability of the boat, particularly monohulls.

    As for wood masts, these are easier to build, since most boat builders are familiar with working with wood and it is available everywhere at reasonable prices. Wood masts will be heavy, particularly free-standing ones like on a junk rig. Even stayed wood masts tend to be heavier than their aluminum counterparts, and that is why aluminum is such an attractive material for stayed masts, and has been so since the 1950s and 60s.

    The types of masts described in "Practical Junk Rig" can of course be adapted to other styles of rig rather than a junk rig. The masts are sized to the boat and the sailplan, which are immaterial of the types of sails themselves. There is no reason why sail tracks and single-ply sails cannot be used on such masts. The design options are numerable.

    Eric
     
  11. BATAAN
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    BATAAN Senior Member

    Junk rig is best when used to get largest sail possible with a very small crew, and avoid light sails. Not in vogue, just does its job well on the proper boat, but certainly will not work on all. There is nothing like being able to put in 4 reefs in a minute and a half, downwind, in the dark, alone. Hasler/Mcleod is a good place to start, but much of their detailing misses some subtleties the Chinese did not, so study closely the originals too if you want to understand and use the rig.
     

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  12. CatBuilder

    CatBuilder Previous Member

    Fantastic thread!

    Is there such a thing as an "off the shelf" carbon mast design for say... the stayed mast on my Kurt Hughes catamaran? As in, if there is an aluminum standard tapered that is in his designs, is there a carbon laminate that would be simple to match?

    Also, how beyond the skills of an average builder would a carbon mast be if you infused it?

    You could have all the time in the world to lay up the the fabric in the proper orientation and thicknesses, bag the thing and suck the resin through.

    Prepregs really wouldn't be necessary, would they?

    The thread has definitely piqued my curiosity, though I know the answer will probably be forget it! :)
     
  13. BATAAN
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    BATAAN Senior Member

    The constant desire for light, fast, lighter, faster has given us fantastic performance under sail for those craft that accentuate that particular design attribute; stability enhanced at ever greater cost by cutting down undesirable weights while tremendously increasing strengths, .
    This push, which is totally dependent on high industrial corporate technology (made your own carbon fiber lately?) and petroleum dependence, has given us fabulous thrill rides, spectacular ocean racing and real engineering progress as our spin-offs from the space and aviation giants, subsidized by government research defense money, that started this stuff.
    Unfortunately this comes at great cost, both to those who want to participate in the carbon mast advantages, and our rapidly-consumed (think tar sands) environment we use to pay for it.
    I fear we have lost the day when a poor guy who has nothing but guts could go out in the woods with an axe and build a very good sailboat that would convert him into a rich person with a job fishing or carrying cargo.
    When he left, the trees grew back, and some years later another guy could do the same thing, forever, so long as there weren't too many guys....
    Instead the demands of the technology work hard in the other direction.
    Here's a carbon-fiber sparred boat that keeps it simple and, while very expensive per pound, gives tremendous all-around performance with great simplicity.
    The other photos show a high-performance sail boat that has very low costs per pound, yet follows the same engineering maxims with different materials and technology which does little damage to wallet or environment, and is hard at work feeding people and making its owner a living, while sailing very fast.
     

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  14. Eric Sponberg
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    Eric Sponberg Senior Member

    Standard carbon fiber masts??--in a word, no.

    Infused mast? If you know the skills, it MIGHT work. And I stress the word "might" because carbon fiber has one bad disadvantage when you come to infusion--wet carbon looks exactly like dry carbon, particularly through an infusion film. With glass, you can see the edge of the resin as it moves through the laminate--the glass goes translucent to transparent and you can easily gauge the amount of resin and infusion time. Not so with carbon--you cannot see the edge of the resin as it advances. Tracer threads of glass within the laminate would help, but such fabrics are not readily available or easy to mix within the laminate. I believe some people are working on this problem, but personally, I have not seen results yet.

    I have had customers use pre-pregs, which have the same advantage as infusion--you can take a lot of time to lay up the laminate. However, with pre-pregs, you have to periodically "debulk" the laminate with vacuum pressure as you go along (probably should too with infusion). Mast laminates can get pretty thick--by that I mean 1/2" (13 mm) or so, and if you don't debulk a few times during the lay-up, the internal fibers can kink and wrinkle, thereby killing all the strength in the laminate. I think the thickest carbon fiber mast laminates I have seen are about 1-1/2" thick (38mm). You also need a curing oven that is WELL controlled with thermocouples within the laminate at critical intervals, and these reading out into a computerized temperature controller. It can be done--my mast design for Copernicus, a Spencer 42 sloop, was built by the owner himself (with a lot of outside help) on the stage of a theater in Vancouver, BC. The whole think, enbuild, was lifted into the rafters at night during performances, and lowered to the stage during the day to be worked on. That was 14 years ago now, and the boat is still sailing well, bound soon for Costa Rica.

    Eric
     

  15. BATAAN
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    BATAAN Senior Member

    Eric, a specific question. When designing a mast for carbon, stayed or not, what sort of safety factor do you use in the final layup/section/taper decisions based on calculated stability, sail area, possible delamination or other imperfection, and the many other factors involved?
    Since COPERNICUS has been quite successful, I'm sure you've refined your thinking and techniques since, and since this is cutting-edge (for us amateur designers), it would seem a good thing to pass on.
    Not being a professional designer, but a very old rigger, I know that any pile of "sticks and strings" has various overload scenarios combined with degradation factors as a guide in the final design.
    These are all new and different with engineered carbon, the various needs of its use, and what breaks and when, so I personally find it really fascinating with every new cool and impossible thing that couldn't be done last year and quickly becomes the norm. Thanks for helping us understand how it works.
     
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