How do I build a mast out of Carbon Fiber or glass

Discussion in 'Boatbuilding' started by Lowcarb, Jun 22, 2003.

  1. guest

    guest Guest

    re: carbon mast

    check out the web site for the Cherub dinghy class in the UK ... (don't have the URL handy).

    They've been building their own carbon gear for several years and there's a how-to there on building a Cherub mast in carbon. Not exactly the same size, I admit... but might be worthwhile reading for you.

    Cheers,
    Tony
     
  2. gggGuest

    gggGuest Guest

    Cherub Mast building URL

    http://www.sailingsource.com/cherub/masts.htm
     
  3. Fateh shareef
    Joined: Apr 2004
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    Fateh shareef New Member

    What are the detailed cost involved in building a fiber boat (open) of 18 ft ?
    Tools ,Materials,Manpower
     
  4. guest

    guest Guest

  5. Guest

    Guest Guest

  6. jack kern

    jack kern Guest

    need to pick your brain a bit about the carbon fiber.
    i would like to reinforce the upper 1/4 of a 35 ft carbon mast to make it stiffer. i am told 300 gm carbon tape would work and will start with three layers of maybe 4 inch i think. can you give me your thoughts on ordering this and where.

    thanks, jack
     
  7. SouthernWing
    Joined: May 2004
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    SouthernWing Junior Member

    Carbon Fibre Wing Mast

    Hi Kelley Ann

    I have also been searching for some information on building a carbon fibre mast. Thankyou for the URL. I was wondering if you have had any success yet and if so would you be willing to let me know what you have found. I will do likewise. Good hunting.\

    Phill Wise
     
  8. JR-Shine
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    JR-Shine SHINE

  9. JR-Shine
    Joined: May 2004
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    Location: Vero Beach, FL

    JR-Shine SHINE

  10. SouthernWing
    Joined: May 2004
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    SouthernWing Junior Member

    Carbon Fibre Mast

    Thanks Joel, I will have a look at it.


    Cheers Phill
     
  11. Karsten
    Joined: Jun 2004
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    Karsten Senior Member

    Hi Guys!
    I don't want to discourage you too much but designing AND building a carbon mast is not easy.

    1. There are many different carbon fibres with VERY different material properities around! There are high strength (HS) fibres which have "little" stiffness and high modulus (HM) fibres that are more expansive, very stiff but have "little" strength and then there is anything in between.

    2. Carbon even has different material properties in different fibre directions. It has very little strength perpendicular to the fibre! This is important at fittings.

    3. You can gretly influence the strength and stiffness of the mast simply by changing the orientation of the fibres! A mast with a wall thickness of 5mm might be fine if most fibres run in the up-down direction and fall to pieces if the fibres are wound around the mandrel perpendicular to the up- down direction. In that case you can almost cast the mast from resin only and leave the fibres out!

    4. You have to use vacuum if you want to hand lay-up. Carbon doesn't get seethrough like glass. So you can't see air boubles under the cloth.

    5. The risk investing a lot of money and time to design and built you own mast is enormous. Get at least a professional to design it and come up with a lay- up plan and materials list. At least you are reasonably sure that if your manufacturing process is up to scratch that the mast will be fine.

    6. Ever tried to pull out a mandrel without a hydraulic press?

    7. A good start is an existing aluminium mast that you know works. Find out what the mechanical properties of that mast are and then get a professional to design a carbon mast with the same mechanical properties (except for the weight obviously).

    Wait a few years. Some companies are experimenting with "pulltruded" carbon masts. The manufacturing process is very similar to extruding aluminium but only with carbon fibres. It's a very cheap manufacturing process. The only problem is that you can't taper the profile. It's used for fibreglass ladders and all sorts of constant sections.

    Cheers,
    Karsten
     
  12. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    Why carbon fibre on a non-racing yacht?? Composite masts are fraught with problems even when proffessionally produced, as an engineer I wince at the thought of them. You would be far better advised to use aluminium masts on this boat.
     
  13. Eric Sponberg
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    Eric Sponberg Senior Member

    Gentlemen,

    Karsten has some good points, masts are not easy to build, and you do have to pay very close attention to laminate details. One additional detail is that you have to be careful of thickness-to-diameter ratio, t/D. If this is not big enough, usually around 0.03 will do, then you risk the chance of the mast collapsing due to column buckling. That is, if the wall thickness is too thin for the diameter, the mast can buckle before it achieves its design strength. The reason for this phenomenon is because of the orthotropic nature of the laminate. There is more fiber running longitudinally than in off-axis directions, and this gives the laminate different strengths and stiffnesses in different directions. Therefore, too thin a laminate for the diameter and the mast is more prone to buckling collapse.

    Contrary to Mike John's comment, there are good reasons to put a carbon fiber rig on a cruising yacht, simply for stability. A mast tube built of carbon weighs about 60% of the same mast built in aluminum. This reduces weight up top, which increases stability, which is always important, no matter what type of boat. Also, there are a number of fine builders available who have been building carbon fiber masts for many years now. The technology is established, although it is not simple. Most carbon fiber rigs survive just fine.

    Eric
     
  14. MikeJohns
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    MikeJohns Senior Member

    Only the mast tube is 40% lighter, 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 only by 20%, with the sails aloft this % drops further.

    Carbon fibre is still very much in its infancy in this field, 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.

    The problem chasing stability with light rigs is the reduction in roll inertia. As eric knows but others may not be aware the roll inertia is proportional to the square of the distance from the roll axis. Therefore the rig has a huge effect on this imprortant seaworthiness factor.

    Reducing the weight aloft leads to higher roll accelerations and higher dynamic loads, and a decrease in dynamic stability.

    A yacht unable to carry a conventional rig due to stability requirements is chasing light displacement and speed as her main design criterion. I know there are various schools of thought on this issue, but my experience (and Marchaj's research ) says that comfort (read heavy and stable and safe) wins hands down in the cruising stakes.

    The light displacement cruising/racing yacht is good fun for coastal cruising and if so designed may will benefit from a lighter carbon mast, but to retrofit a carbon mast on any reasonable design will be trendy, detrimental and expensive.

    LOWCARBS heavy displacement double ender needing carbon fibre masts.................?
     

  15. sorenfdk
    Joined: Feb 2002
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    sorenfdk Yacht Designer

    To my mind, stability is THE single most important seaworthiness factor, so if you can gain some here and loose a little roll inertia, I think it's worth it.

    And remember: The lighter rig will also reduce pitching - another important factor.
     
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