Converting 10t gaffer to single mast junk

  • 21 Aug 2023 21:11
    Reply # 13243748 on 13127979

    Well done Jim, is the mast as stiff as you hoped it would be? And could you give weight 

    length and diameter please?

    regards Rudolf

  • 21 Aug 2023 19:06
    Reply # 13243676 on 13127979

    An update on the mast building. Last week I finished laminating. The mast has biaxial glass then 2.5 mm of uni directional carbon, a layer of biaxial, another 2.5 mm of carbon and finished with a final biaxial using epoxy throughout.

    It took about seven weeks of evening's and weekends and was a bit of a sticky slog! I am now doing a bit of fairing with micro balloons and will paint with 2 part polyurethane. The aim is to get it finished and hand trollyed to the local marina by middle of September. Then when Atlas comes out of the water I will fit the floors, extend the mast step and beef up the deck structure.

    So far things are going according to plan but it is a  lot of work and a bit slower than I initially thought. I am looking forward to the next stages and then thinking about the sail. Still considering a flat sail but will continue to do research. I live near Chichester on the South coast of England if there are any junkies who want to come by.

    Cheers, Jim

  • 04 Jun 2023 16:56
    Reply # 13210310 on 13127979

    Hi Rudolf, the finished wall thickness will be 18mm at its thinnest part. I have 10 X 14.7m lengths with beveled and tapered sides glued up. 8 of these have been glued into pairs. I am getting closer to doing a dry assembly with Spanish windlesses and will have to get some help in handling everything!

    1 file
  • 03 Jun 2023 21:40
    Reply # 13210181 on 13127979

    Hi Jim,

    Exiting times I suppose..

    When you have glued the strips to full length you may start to wonder how good an idea this is in the first place. What wall thickness will the wooden tube have?

    Last one I did was about 6mm wall for the wooden tube. I couldn’t get much thinner   as the machine didn’t allow it; the wood starts to wobble in the thicknesser as it is bending between the fore and aft rollers.

    Once you have glued the strips together into the half-mast shape things will start to

    look like a workable solution.

    Good luck,


  • 31 May 2023 20:13
    Reply # 13208775 on 13180342
    Anonymous wrote:

    Thanks Rudolf, that is very helpful.

    Hi, I thought some members might be interested in my progress so far. I converted approx 15  5m by 150 by 27 rough sawn clear Douglas fir into 30 5m by 22 tapered boards with bevelled edges. 

    A high sided poly tunnel type shelter was built onto my shed in the garden and 10 spar trestles set up level and straight. The boards are being scarphed (8:1) together and then made into pairs with biscuit joints.

    The plan is to glue up these pairs in such away as to be able to separate into 2 halves, glass the insides and put conduit for cables and a radar reflector in before gluing together.

    After fairing, layers of 600g biaxial glass cloth and unidirectional carbon will be laid in epoxy.

    So far it is going according to plan and am hoping for a successful glue up.

  • 25 Apr 2023 20:06
    Reply # 13180342 on 13127979

    Thanks Rudolf, that is very helpful.

  • 24 Apr 2023 21:22
    Reply # 13179056 on 13127979

    As a rule of thumb I used a layer of biaxial glass at least every 2 mm of carbon thickness.  Also the first as well as the last layer should be biaxial glass.

  • 23 Apr 2023 20:23
    Reply # 13177786 on 13127979

    Thanks for the heads up. I was going to build up the unidirectional carbon first and basically do many layers until it is used up then finish with some layers of 45/45 glass. Do you think this is the best use of the materials or would it be better to alternate them. Or would it be better to use 45/45 carbon and just finish with a layer of glass for protection. 

  • 22 Apr 2023 20:30
    Reply # 13177153 on 13127979

    Hi Jim,

    The use of glass and carbon in one laminate only makes sense if they are applied for different load directions. If you use glass in the same load path as carbon the glass will only start to work when the carbon fails as glass is more elastic.

    In my masts I use glass only for the +/_ 45 degree layers that are meant to keep the carbon from buckling. For the zero degree layers, straight up and down the mast, only carbon.


  • 22 Apr 2023 08:01
    Reply # 13176718 on 13168399
    Anonymous wrote:

    Hi Jim,

    Years ago I built a couple of carbon masts professionally. I hired an engineer to specify carbon and glass layers to reach a desired stiffness/strength for each separate mast.  Eventually this left me with enough data to interpolate subsequent masts. Obviously this is not a one size fits all thing.

    The woodcore masts I built in two halves which is easier to lay up the carbon. The halves are glued together and  the join taped heavily.

    A good way to approach carbon wall thickness is to use the wall thickness of a suitable aluminum tube mast. A carbon mast would be both stiffer and stronger than an aluminum mast of same wall thickness. Of course one can vary wall thickness of a carbon mast along its length to resist the loads at corresponding locations which would be the most efficient use of materials.  



    Hi Rudolph, thatnks for that informative reply, particularly about the aluminium and carbon wall thickness.

    Over the last few weeks I've been talking to the various carbon manufacturers. I've been able to buy from a clearance bin 11 rolls of 50m long, 330g, unidirectional, 6 in wide carbon tape for well under half price.

    I think this will work well with my idea of laying long cloths full length on top of each other with an overlap and as you say building up more in areas that need it. Could also go round and round twice in different directions. With so much laminating the correct use of peal ply will be important.

    When I've used up the tape I will carry on with glass untill I get to the weight I want.

    Cheers, Jim

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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