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Building a mast from aluminium and wood

  • 28 Oct 2013 13:57
    Quote
    Reply # 1422862 on 1420367
    Anonymous member
    Dieter Isenhardt wrote:Thank you David and Gary, the feed back gives me confidence to tackle the job. I like to step the lower sections and and fabricate the GRP collar in the shed and remove before launching. I will finish the masts later. 
    I'm sure I have more questions as thing progress but one step at the time.





    Already more questions. 
    A sentence from Davids Mast write up reads ..A 25mm wide longitudinal section was cut out of this 4m parallel section, and it was squeezed together and pulled into the lower end of the mast as a doubler at the partners area. 
    It sound simple in one sentence read quickly.
    I wonder how difficult this is and what can go wrong and what to look out for.
    Would I make the cut out a few mm larger than calculated or more and would I have to lubricate it and glue it in at the same time?
  • 24 Oct 2013 14:23
    Quote
    Reply # 1420367 on 1144363
    Anonymous member
    Thank you David and Gary, the feed back gives me confidence to tackle the job. I like to step the lower sections and and fabricate the GRP collar in the shed and remove before launching. I will finish the masts later. 
    I'm sure I have more questions as thing progress but one step at the time.





  • 23 Oct 2013 23:18
    Quote
    Reply # 1420013 on 1144363
    Deleted user
    The wood heel on our foremast is 3 times diameter of the tube (insertion length),  but only because the tube starts 10cm above the tenon and the bury is not so huge, about 1.2m on the foredeck. Used sikaflex and did insert fastening, 4 small galvanised screws (they shouldnt eat the alu like stainless would). I figured the holes were far enough away from the partners it would be ok, but probably wasnt necessary. 

    The main mast didnt need a heel, I made a round step from ply. Neither mast are bolted at the step, since I used "Spartite" type urethane at the partners, without releasing agent, they are effectively glued in. I could claim the downhauls hold the masts in too..
    The boat spent 5 hours pitching into steep chop on Monday and neither mast moved -FWIW.
    Last modified: 23 Oct 2013 23:24 | Deleted user
  • 23 Oct 2013 16:45
    Quote
    Reply # 1419716 on 1144363
    Anonymous member
    I think you're right, Dieter. There is only a shear load, and no bending moment, on the wooden tenon at the heel, if the tube extends right down to where the tenon starts, so one diameter of engagement in the tube is enough. But a little insurance against "strange things that happen at sea" might be a good thing, so I'd make the plug 1.5 diameters long. I wouldn't pin it in. Try to avoid holes in the tubes wherever possible. I would use Sikaflex, or similar, with no mechanical fastenings.
    Last modified: 23 Oct 2013 16:46 | Anonymous member
  • 23 Oct 2013 15:39
    Quote
    Reply # 1419652 on 1406633
    Anonymous member
    Dieter Isenhardt wrote:

    Hi,

    I had almost given up the idea of two composite masts for my Catamaran when I came across two sections in the One Steel Aluminum catalog.

    6082-T6-MF/DNV-219mm-8.2mm-5850mm-85.77kg-$752.82

    6082-T6-MF/DVN-203.2mm-3.0mm-6000mm-30.56kg-$282.23

    I can get the sections shipped up from WA for about $300.

    The masts required are 13.5m (11.8m above the partners) side by side, sail area 40-45m2 Split Junk Rig.

    My idea is to slide the 203mm section for 1m in to the 219mm section, squeeze 2.5m of 203mm section in to the 219mm section at the partners, and make a tapered 2.5m wood section for the top and a 300mm section for the foot.


    I received my mast tubes today and want to make the mast foot.
    I have a square tapered mast step. I have to make a solid wood heel to glue and pin in to the lower 219mm diameter-8.2mm WT tube. I wonder how far it has to go in to the tube?
    I couldn't find an answer in PJR. From what I could see it appears to be not much more than the diameter of the tube. Anyone knows, I would appreciate some advice. 
    Last modified: 28 Oct 2013 13:31 | Anonymous member
  • 09 Oct 2013 11:33
    Quote
    Reply # 1408410 on 1144363
    Anonymous member

    Thanks for the reply. 

     I realize that I might have to machine more than .2 mm off depending how round the sections are. This could be a lot of sanding.

    I had a look at your mast photos and sail. Good to see it all worked out well. I’m looking forward to your sail report. I won’t be sailing for a while but look forward to live on a boat again.

    I can relate to the stress and money hemorrhaging pre splash.

    Happy sailing
  • 08 Oct 2013 21:26
    Quote
    Reply # 1407973 on 1406633
    Deleted user
    Dieter Isenhardt wrote:

    Hi,

    I had almost given up the idea of two composite masts for my Catamaran when I came across two sections in the One Steel Aluminum catalog.

    6082-T6-MF/DNV-219mm-8.2mm-5850mm-85.77kg-$752.82

    6082-T6-MF/DVN-203mm-3.0mm-6000mm-30.56kg-$282.23

    I can get the sections shipped up from WA for about $300.

    The masts required are 13.5m (11.8m above the partners) side by side, sail area 40-45m2 Split Junk Rig.

    I have a pair of those 162mm-6mm Al pole/wood composites masts on our boat and looking at it swaying in the pen, I cant see any flexing or whipping at all. The masts appear completely rigid. The 219mm dia pole is 3 times the stiffness of the ones I have and only 2 metres taller, so seems like a pretty good idea for a cat. Looks like you'll need to machine off .2mm from the wall of the thinner pole to slide in.

    Anyway, appears to be a rash of junk launchings up there in SE QLD, with Gary in Tweed, another Gary in GC (with a Colvin) and yourself. I noticed activity, stress and money haemorrhage increase with splashing..  Good luck with it. :D
  • 08 Oct 2013 15:20
    Quote
    Reply # 1407664 on 1144363
    Anonymous member

    Hi Mark,

    It sure requires patience and I’m running out of it.

    I think putting a Junk Rig on a cat is a bit of an experiment since there are not many around. I have researched the subject as much as I’m able to understand and like to go with something tested on the water. I like to copy something which is working like David Tyler’s mast. I made the step and partners for a 280mm diameter 8 staved timber masts.

    I considered Pete Hill tabernacle but keel stepped is simpler and I don’t need to lower them. Carbon fiber is expensive and out of the question if produced under controlled conditions and otherwise might just be another experiment and still expensive.

    I like to make a Slieve McGalliard  Split Junk Rig like Poppy’s.   
  • 08 Oct 2013 13:45
    Quote
    Reply # 1407560 on 1144363
    Anonymous member

    Dear Dieter,

    good to see another Junk Cat in the making.  I am hoping to do a conversion soon, I would not have the time and patience required to build from scratch.

    The flexibility of GRP may be of advantage to a JR cat, having a bit of give, (considering we are not to keen on heeling over!) GRP flagpole up to 14m long are available here, not sure how strong they would be, but we be a ready starting point to add some carbon reinforcement. 

    Looking at the photos, I assume your mast is keel stepped.  Have you considered a tabernacle, as Pete Hill has done on both his JR cats?  Lots of advantages, (I assume) no leaks, easy to lower, and you can make your mast shorter.  Pete's are strong timber constructions and look a bit chunky.  My thoughts would be to us a aluminuim or grp half shell, very thick and strong, but still would follow the shape of the mast.

    What sail type are you proposing?

    Cheers Mark

    Last modified: 08 Oct 2013 13:50 | Anonymous member
  • 07 Oct 2013 13:52
    Quote
    Reply # 1406633 on 1144363
    Anonymous member

    Hi,

    I had almost given up the idea of two composite masts for my Catamaran when I came across two sections in the One Steel Aluminum catalog.

    6082-T6-MF/DNV-219mm-8.2mm-5850mm-85.77kg-$752.82

    6082-T6-MF/DVN-203.2mm-3.0mm-6000mm-30.56kg-$282.23

    I can get the sections shipped up from WA for about $300.

    The masts required are 13.5m (11.8m above the partners) side by side, sail area 40-45m2 Split Junk Rig.

    My idea is to slide the 203mm section for 1m in to the 219mm section, squeeze 2.5m of 203mm section in to the 219mm section at the partners, and make a tapered 2.5m wood section for the top and a 300mm section for the foot.

    I based my idea on APATIKI’s masts on a 46 Wharram Tiki with the same length masts and sail area in all aluminum sections. The mast are made of 150mm diameter x6mm sections with the final dimensions being 12mm up to 8.5m, 6mm to 10m, reduced 140x6mm to 12.5m and 125x6mm to 13.5m. From what I know the masts have been working for a number of years.

    I think my proposed composite masts would be comparable but I don’t know.

    I would appreciate any comments from members.

    Last modified: 28 Oct 2013 13:30 | Anonymous member
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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