Hybrid mast making

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  • 03 Nov 2021 08:08
    Reply # 12095389 on 12090300
    Anonymous wrote:

    As I recall, the foremast was had a diameter about an inch more at the partners, due to the minimal bury.  They both seemed more than adequate and were seriously challenged on occasion.

     The plans for the 31.8 show the forward mast as being 1/4" bigger diameter at the partners than the main mast. Not a right lot, and, in terms of hybrid mast design, pretty much insignificant when you end up having to choose a standard diameter aluminium tube to suit.

    The issue I have at the moment is that I can't find a company in Germany that will sell a suitable dimensioned (or 2) aluminium (6082 T6 or similar) tube to a private person. Any suggestions would be appreciated :-)

  • 01 Nov 2021 20:26
    Reply # 12090300 on 3500760

    As I recall, the foremast was had a diameter about an inch more at the partners, due to the minimal bury.  They both seemed more than adequate and were seriously challenged on occasion.

  • 01 Nov 2021 08:44
    Reply # 12088450 on 3500760

    Interesting picture Annie. Thanks!

    Returning to my original question, I note that PJR states, "Given the same LAP and sail area, D for a foremast should be about 1.13 times that of a mainmast or mizzen". (p.129)

    This makes total sense as, when I calculate the mast diameters using the graph (fig.8.15) on p130 of PJR, I get mast diameters that are exactly as per the plans. This certainly seems to be what Jay Benford has used.

    Interestingly, the 2 masts come out as being basically the same diameter at the partners because the LAP varies. When the 1.13 multiplication factor is added to the shorter foremast, it gives the same dia as the mainmast at the partners.

  • 31 Oct 2021 21:19
    Reply # 12087374 on 3500760

    Here you go, Arne.  This shows Badger dried out (in the Falkland Islands) in, I think, 1994.  This was the rudder that we fitted in 1983 and the skeg was added a year or so later.  This photo was taken when we were installing the diesel engine we had acquired, fitting it between tides!  You can see the new cutout in the skegs.  This rudder worked very well - it was completely protected buy the skeg, and allowed Badger to sail herself close-hauled with no-one at the helm - assuming the sea wasn't too rough. 

    You can also see the trim tab for self-steering gear that we had recently made.  There is a vast amount of kelp around the Falkland Is and every time we went sailing, it would snag the servo gear and the 'breakaway' coupling would break away.  You don't really want to do a lot of hand-steering when making passages in that part of the world!  This trim tab gear, with the vertical-axis vane, was the easiest to set up and in my opinion, it worked better than any of the others. 

    1 file
    Last modified: 31 Oct 2021 21:25 | Anonymous member
  • 29 Oct 2021 18:21
    Reply # 12082355 on 11973905
    Benford dories often have inferior rudders.  We had to completely redesign and rebuild Badger's and the one that he shows in the drawings of Badger, as distinct from the 34 ft dory, is not the one we fitted.

    Dories are notorious for having low initial stability  I should not want to put a lofty mst on one.  Follow the rudder and rig on Jim Creighton's dory of similar size, and you won't go too far wrong, in my opinion.

    As for dimensions: when we designed the schooner rig for Badger, we just followed the formulae.  I don't think H/McL say you have to desing different sized masts depending on how many there are, but I could be wrong. 


    Thanks for your comments Annie. Yes, I've followed the discussions on rudders for Benford dories and have modelled mine following the recommendations as I understand them. To give Jay Benford his credit, the 31.8ft dory that I'm building was (I believe) the latest version he designed, and the rudder on the plans is very much in keeping with the rudder design thoughts I've read elsewhere. I have added end plates and an airfoil cross section, and hope it'll turn out to function - only time will tell!

    You are quite right that H/McL don't say that mast size is different for more masts. They do, however, base their mast diameters on sail area against mast height, which is not what others here do. I note that Pete seems to base his mast diameters on H/McL derivatives and therefore don't doubt that their suggestions work.

    I have to say that I'm very impressed with the tabernacle design you've used on FanShi. That, coupled with the hybrid mast construction concept, is what started this whole line of inquiry for me. I'm still exploring ideas... :-)

  • 27 Oct 2021 09:12
    Reply # 12001683 on 3500760
    Anonymous member (Administrator)

    I think Annie is very right here. Unless one has given the vessel a very efficient rudder (and/or retractable cb/leeboards), one cannot expect that the boat will obey the rudder if the foremast or foresail fails.

    Many sailing ships were wrecked along our coasts because of partial rig failure which rendered them uncontrollable.

    Therefore, IMHO, there is no such thing as a too good rudder.

    Cheers, Arne

    PS:
    Annie, could you sketch up the final rudder of Jester  -  no, I mean Badger   -  silly me, on a piece of paper, photograph it, and then show it to us, please?



    Last modified: 30 Oct 2021 22:07 | Anonymous member (Administrator)
  • 26 Oct 2021 21:37
    Reply # 11974097 on 3500760
    I might add that thinking a second mast means you can carry on as normal if you lose one of them, is a complete misconception.  You may well be able to sail downwind, depending on the boat, but on any other point of sailing you would have little control, as Aubrey Hinchcliffe discovered in Upik,  any years ago when he lost his foremast.
  • 26 Oct 2021 21:32
    Reply # 11973905 on 11439453
    Arne wrote:

    I only see two-three reasons for using a ketch or schooner rig on a moderate size boat:

    • ·         If the boat has an inferior rudder, when two sails let one steer the boat with the sails.
    • ·         If the boat has low stability for its length (e.g. sharpies) so the 2-stick rig can bring the centre of SA (plus CG) down a little.
    • ·  


    Benford dories often have inferior rudders.  We had to completely redesign and rebuild Badger's and the one that he shows in the drawings of Badger, as distinct from the 34 ft dory, is not the one we fitted.

    Dories are notorious for having low initial stability  I should not want to put a lofty mst on one.  Follow the rudder and rig on Jim Creighton's dory of similar size, and you won't go too far wrong, in my opinion.

    As for dimensions: when we designed the schooner rig for Badger, we just followed the formulae.  I don't think H/McL say you have to desing different sized masts depending on how many there are, but I could be wrong. 

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