David Thatcher's New Boat

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  • 28 Oct 2018 18:58
    Reply # 6876942 on 6876721
    Arne wrote:

    One must not always choose a JR...



    Ah, true, Arne.  Life can be cruel.  And we'll still welcome David at all our junkets!!
  • 28 Oct 2018 15:01
    Reply # 6876721 on 6876461
    Anonymous member (Administrator)

    I think David Thatcher’s reasoning behind rigging with an ‘ordinary’ rig makes sense here.

    The mast can be reached from the cockpit or hatch, so hoisting, furling or reefing can be done quickly, and in perfect safety. If the jib is on a roll, there will be no need for going on the fore-deck when under way.

    The shrouds will not let one square the mainsail fully out, but that has little consequences here:

    ·         The sheet forces are so low that one can easily sheet in the mainsail before gybing.

    ·         On a cat like this, one will probably move faster downwind by broad-reaching, so there will be less need for squaring out the main.

    One must not always choose a JR...

    Arne


  • 28 Oct 2018 12:49
    Reply # 6876603 on 6876461

    David

    Is it possible to fit a biplane rig ala Oryx?

    Best of luck with your new build.

    Peter

  • 28 Oct 2018 08:12
    Reply # 6876500 on 6876461
    Anonymous member (Administrator)

    David, are you saying that a free standing mast stepped on the bridge deck is out of the question?

    Or are you saying it would be acceptable but only in the position of the shown gunter rig mast or 1.3m ahead of it?

    If the latter, then I believe there is a solution to the junk rig problem, possibly more than one.

    Last modified: 28 Oct 2018 08:14 | Anonymous member (Administrator)
  • 28 Oct 2018 06:23
    Reply # 6876484 on 6876461

    Oh, forgot to say.....

    A removable compression post wouldn't be too hard to design, you could take it out when on anchor and gain full accommodation.

    An easy way to make it in my opinion would be a pipe with a 12 mm nut welded to the one end, into that goes a bolt. The bolt acts as the pipes extension, by screwing it in or out. A couple turns on the bolt would make it easy to get the compression post out, or put it back in place before sailing away..... 

    To make things easier, welding some sort of a handle onto a nut, then screwing that nut to the middle of the bolt and tightening another lock nut to it will make things even simpler as no tools will be needed to got the post in or out of it's place. You could just turn it by hand using the handle nut. Welding directly onto the bolt itself will weaken it, but welding onto a nut is no problem.

    Nice looking cat by the way.

    Rael.

    Last modified: 28 Oct 2018 06:53 | Anonymous member
  • 28 Oct 2018 05:45
    Reply # 6876464 on 6876461

    David, I aint no guru.....

    But still, a stayed junk rig will work, you could step it on top of the bridge deck as long as there is a compression post under it, the compression post will be mounted over a strong beam that would lay over the full width of the bridge deck floor.

    That will allow you to place the mast and sail anywhere you want, if the shrouds where Dyneema, the sail could lay against them on a run without too many issues....

    A stayed mast could be lite weight too.

    What do you think??? Or did I miss something???

    Rael. 

     

    Last modified: 28 Oct 2018 05:48 | Anonymous member
  • 28 Oct 2018 05:23
    Message # 6876461
    Deleted user

    After three months of spare time work I finally have something worth photographing and posting with both hull frames now complete. This is my new Eco 6 Catamaran. As can be seen by the photo it is now recognisable as a sort of boat-like object, although not much to keep the water out yet! This is going to be a very light weight, and hopefully performance orientated bridge-deck sailing catamaran. There will be enough accommodation for coastal cruising, and a reasonable sized cockpit. This is a Bernd Kohler Eco 6 design.

    When I began building I had high hopes of fitting a junk rig. I have enjoyed the junk rig of 'Footprints', and I like the idea of a performance sailing catamaran with a junk rig. However try as I might I have not been able to come up with a workable junk rig sail plan which satisfies all the various considerations on this design. I have also put up a pic of the gunter rig sail plan which shows the CE and CLR, both of which are well aft on this design. The bow on my boat differs from that in the pic, I have an inverse bow which has a 10 degree aftward rake.There is enough bury in the bridge deck area for a free standing mast, but the mast really needs to go in the position of the gunter rig sail plan, or 1.3 meters further forward. Anything in between will interfere with the bridge deck accommodation. There is also the need to keep weight out of the forward part of the boat because the hulls are very slender in the forward sections and therefore not able to carry a lot of weight forward.

    So if any of our junk rig gurus is able to come up with a workable junk rig option I will happily build it. It has to be light weight and about 20 square meters in area. Otherwise it will be either the gunter rig, or the very square top bermudan mainsail and small jib, which isn't quite a pointy sail!

    And I will keep on working in whatever spare time I get. Fairing the frame next weekend, and then putting on the plywood.


    2 files
    Last modified: 28 Oct 2018 06:33 | Deleted user
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