Hybrid mast making

  • 21 Oct 2015 15:23
    Reply # 3593312 on 3500760

    David,

    I am admiring, as usual, your fine work.  I have a quick question and please forgive me if you have already addressed it.

    Why a hybrid mast? Why not a flag pole or light pole of sufficient height? 

    Dennis

  • 20 Oct 2015 22:33
    Reply # 3592199 on 3500760

    The topmast is now sheathed and assembled into the tube, using Simson's Marine Glue - the local equivalent to Sikaflex. This morning, I got the first coat of paint on: International Perfection, platinum colour. Not only is it the same colour as the anodised tube, it's the same colour as my hair, if I get it on me (more than likely!). 

    I'll be using U-bolts through the truck to attach the halyard and lifts. I'v e found this method very reliable on my mainmast.

  • 16 Oct 2015 17:00
    Reply # 3586126 on 3500760

    Thanks for your help David,

    No reason for aversion to epoxy, I just have a lot of polyester as I make small rowing boats.  Longevity would outweigh convenience so  using epoxy is fine.

    Cheers Mark

  • 15 Oct 2015 20:40
    Reply # 3584579 on 3500760

    Mark,

    Is there a reason for not using epoxy? Polyester resin would be a poor choice for sheathing the topmast. The cloth need not be too heavy.

    The thickness of the staves should be 22mm, for a 100mm finished diameter, so you can get them out of 1in nominal boards. To find the width of the staves, draw a hexagon that is 100mm across flats, for the bottom end, and another, 50mm across flats, for the upper end.

  • 15 Oct 2015 18:54
    Reply # 3581951 on 3500760

    Thanks David,

    I think I should be able to get Douglas Fir the easiest.  I need to make a top mast of 3.4m to fit a 100mm ali tube.  What would be the raw size of the fir before the staves are cut?  I was also thinking of covering the finished mast in 300g woven roving and polyester resin.


    All the best,

    Mark

  • 14 Oct 2015 20:17
    Reply # 3577733 on 3500760

    I used yellow cedar, but Annie has bought some douglas fir for her mast, a more usual spar-making timber.

    In my case, for fitting to a 6 m x 152mm tube, the staves are 4.2m long, 88mm wide at the bottom, 53 wide at the top, with a convex curve to give 79mm width at mid height. The bury in the tube is 400mm.

    Cascamite, or preferably Resorcinol, could be used as an alternative to epoxy, but the joints would have to be more closely fitted. I would suggest cutting the 30 degree angle with a hand-held circular saw, then passing the staves over a surface planer set to 30 degrees, as a way to get them fair and true.

  • 14 Oct 2015 17:29
    Reply # 3577546 on 3500760

    Hello David,

    What type of softwood did you use for the staves?  And what is the sectional size?  Could the staves be glued together with 'Cascamite'?

    All the best,

    Mark

  • 10 Oct 2015 22:45
    Reply # 3571276 on 3500760

    More pics of the process of making the topmast are in my photo album.

  • 21 Sep 2015 20:51
    Reply # 3537227 on 3500760

    The curve was drawn along a batten, clamped to the stave,a nd then cut with a handheld circular saw, as I said earlier. The control is sufficient to follow the line, with some hand planing afterwards. When I've finished rounding off, I'll cut the shoulder to engage with the alloy tube. This section will be left uncoated, as I'll use Sikaflex to fix it in place, which needs to draw moisture from the wood to cure.

    I still believe the hybrid mast to be the most pragmatic way of obtaining a good unstayed mast. It's a major undertaking to make a full-length wooden mast of this size, which would be larger in diameter at the partners, and heavier. I could glue up the topmast on my own, but a full-length mast requires a trustworthy team of helpers to spread glue and assemble within the epoxy's working time. Making the staves requires much more shop space and a bench length equal to the mast length. It's difficult to find sizes of tube that will sleeve together neatly, and there's always a step to fair in somehow.

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