Rolled Carbon Mast

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  • 15 Jun 2021 16:59
    Reply # 10642756 on 10636778
    Deleted user
    Anonymous wrote:

    Glass fibres wet out more easily than do carbon, so itis no doubt easier to saturate the weave that is 'sewn' to link the slats on the inside of the tube. Major structural contribution of the carbon is in the lengthwise/longitudinal direction and the small amountt of added bulk that comes with some glass, is well worth it's practical value over a minor weight penalty.

    I think glass is pretty much always a component of a carbon fiber mast.  Carbon fiber is incredibly strong in tension and compression for it's weight, but need to be "contained", presumably in a cheaper material.  These pultruded sections are unidirectional.  I would presume that glass fabric or non-woven bidirectional glass would be laid on a bias to flesh the mast out. and provide some torsional strength as well as hold it's more or less round shape.  The mast is not being built in a madrel, so vacuum bagging is not an alternative.  Ultimately it would make more sense to build any additional structure inside rather than outside, as the tension / compression members need to be at the extremities, but that's not realistic. 

    The attraction of the pultruded material they are using is that it is rollable and in long strips.   It's not the ideal material.... It's easy to work with obviously.

        My idea of how to build a carbon fiber mast is to string a cable between two "dead men"..... Heavy stationary structures.   Pieces of XPS foam would be  strung on the cable, and glued together, and enough tension applied to hold the works straight.  The foam core which is sacrificial, would then be shaped and smoothed, and any inner plies of material applied to it and vacuum bagged forming the permanent core.  Carbon fiber in the form of unidirectional material such as roving would be applied  with some tension, and held by epoxy compatible spray adhesive.   You would apply the full length stuff, and then shorter and shorter material staggering things so there was  no abrupt changes.   This would then be saturated with resin and vacuum bagged.  Once cured a protective outer glass layer on the bias would be applied and also vacuum bagged.  At the end of the process, solvent would dissolve the XPS foam out and of course the cable would be removed leaving you with a full length tapered mast.

       It would be a time consuming and expensive process, but nothing compared to the cost of buying a factory made mast.    I'm not enthusiastic about the telescoping mast being built with straight sections. It's main virtue is that the construction is simple.   I'm not sure how one would extend and retract it.... looks complex to me.   


    Last modified: 15 Jun 2021 17:01 | Deleted user
  • 14 Jun 2021 20:52
    Reply # 10636778 on 10539767
    Deleted user

    Glass fibres wet out more easily than do carbon, so itis no doubt easier to saturate the weave that is 'sewn' to link the slats on the inside of the tube. Major structural contribution of the carbon is in the lengthwise/longitudinal direction and the small amountt of added bulk that comes with some glass, is well worth it's practical value over a minor weight penalty.

    Last modified: 14 Jun 2021 20:56 | Deleted user
  • 14 Jun 2021 18:23
    Reply # 10635855 on 10539767

    Why didnt they ask Rudolf?

  • 14 Jun 2021 16:16
    Reply # 10635089 on 10539767


    I may be wrong, so anyone please correct me.

    Robs technique uses grp for the first layer as it bends more readily.  Carbon has a great advantage in tension, not so much in compression.  I guess it is formed to a cylinder before fully cured.  

    Pulltruded products have a very high fibre to resin ratio.

    I believe Rob has developed an excellent technique.  Hope he gives us the finished weight and dimensions when complete.

    As for his telescopic mast….hmm. Only see problems with that.

  • 14 Jun 2021 04:30
    Reply # 10631055 on 10628537
    Anonymous wrote:

    laminated to a presumably fiberglass backing....

    Fiberglass backing? doesn't that kind of negate the reason for using carbon in the first place? It would seem at that point an aluminum pole of the same strength might be cheaper and lighter. While it seems very large diameter, it would depend on the height overall. If the diameter is greater than an equivalent aluminum pole, then windage would suffer as well.

    Also, I would point out that normally CF poles seem to be wound 45degrees from the mast. in the carbon fiber section shows this, just carbon fiber and resin no extra weight. I would like to see one of these strip poles stressed to failure...

    So bigger, heavier and maybe weaker... from the armchair, so I can afford to be wrong.

  • 14 Jun 2021 01:58
    Reply # 10630704 on 10539767
    Deleted user

    Just guessing that the cf hoop rolled extrusions are similar to a glass product called Cflex that was sold to create GRP planking on boat hulls when put over a male form and wet-out with polyester resin. No doubt an epoxy resin is recommended for the carbon product and a form of sorts (either male or female) would be helpful to set up the tube before a wet-out that sets the shape. Further laminate build on the outside should be possible, which is not as good as additional laminates on both sides, as was possible with cflex hulls. Smells as though this something on offer from Rob Denney - a development of his early system where carbon tow was laid onto a flat mold, creating the slats that were assembled and bonded to create a tapered mast. I think it would be advantageous to have curved slats that produced smaller radius tubes, which would allow wing form batten parts to slide up and down the mast during reefing. 

  • 14 Jun 2021 00:47
    Reply # 10630620 on 10539767

    If I'm going to all the trouble of a Carbon mast for a junk rig, I'd want a fully tapered one. In theory one could make one with at technique but it would probably be fiddly.

  • 13 Jun 2021 15:38
    Reply # 10628537 on 10539767
    Deleted user

    The original post met with a "resounding silence"  ;-)    I've posted two photos here that might interest anybody who is even slightly interested in this topic.  The top image is of the parallel strips of pultruded carbon.... illustrated in the previous post, laminated to a presumably fiberglass backing.... details are scarce, such as the exact nature of the backing and the resin used.... Note that there are about 24 strips..(est).. I didn't count every the amount of bend at each "joint" is small... perhaps 12 deg.  The second photo shows the mast rolled up into an icositetragon.  Presumably the works is wrapped in more fiber to help it retain it's shape, and I would assume that there are pieces inside to help it hold it's approximately round shape temporarily.   This is actually the bottom section of a 3 section telescoping mast....I'm hoping they will let slip some more photos to flesh out the construction process.... This mast is obviously quite large... I'd estimate about 300mm from some of the context which didn't include in the screen shots


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  • 23 May 2021 16:58
    Message # 10539767
    Deleted user

          I was just looking at a photo of the "home" construction of carbon fiber mast.    These are free standing masts for a Ballestron rig, so they are pretty substantial.   The mast is being constructed in 3 sections... top, middle, and bottom.   The photos were of only the first stages of construction... or more accurately the second stage, as it appears to be constructed from parallel strips of pultruded carbon which comes in rolls.   The strips appear to be perhaps 70mm wide, and quite thin, and have been bonded to a backing... presumably a light fiberglass so that they can be rolled up into a tube... presumably around some sort of temporary internal bulkheads.  Fastened with ratchet straps, and the joint presumably taped and bonded.  Additional layers of fiberglass are added, and infused, and it appears from what little is visible that perhaps a foam sandwich layer is added internally.  Not much detail is provided needless to say, because the actual process is a closely guarded secret available to plans buyers only.   I'd love to know more.

        An interesting technique..... Needless to say the mast is large diameter.  Most few if any of us will ever attempt to build a carbon fiber mast, but it's interesting to see how one designer approaches it.


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