Multi hull junk

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  • 10 Mar 2016 14:04
    Reply # 3872932 on 3781386

    Keith,

    hope you go for it, too few Junk multi's out there.

    Definitely a Cat - I would only look at a Tri if looking for something smaller.  Even my wee 23' Hirondelle  (now sold) had standing head room (for small people) in the hulls, plus 5 berths and decent size heads -  You get a lot for your money! 

     What are you looking for accommodation wise?  I have looked at one or two 25-30' Cats for JR conversion.   The older heavily built bridge-deck Cats should be able to take a single mast not too much engineering, especially if a more balance rig  - i.e. Split rig.  If you keep your eyes on what is for sale there are many bargains (not as many as monos) I reckon £20-£30k will give you a very good Cat, converted, if you are prepared to do a bit of work

    Pete Hill Oryx and earlier China Moon, as are Bertrands Pha /Grand Pha are excellent examples of ocean-going Junk Cats.  All new and owner built, which is a lot more work and dedication.

    Best of luck.


    Last modified: 10 Mar 2016 14:09 | Anonymous member
  • 07 Mar 2016 20:12
    Reply # 3866744 on 3781386
    Anonymous

    Issue 33 - Nymph was the tri.

    Chris

    Last modified: 07 Mar 2016 20:20 | Anonymous
  • 07 Mar 2016 20:06
    Reply # 3866742 on 3781386
    I have no experience with trimarans, myself, but Bunny Smith's experiments on his tri seemed pretty successful.  he wrote about them in the magazine, but I'm afraid I don't have time to go through the index and find it at present.  However, you can find the index and download the magazines here.
  • 07 Mar 2016 07:07
    Reply # 3865187 on 3781386
    Deleted user

    I have made several comments re this topic previously. As an experienced multihull sailor, (about 12 ocean crossings on a Searunner 37 trimaran), I just don't think a junk rig will work that well on a trimaran. One of the reasons for this is the motion of trimaran, which if you are going to get any performance at all will tend to be quite jerky and lively in it's motion. This is not a problem and one gets used to it after a while. But having sailed a junk rig now for 8 years I have noticed that in any conditions where the motion of the boat is jerky the sail looses power very quickly and seems to need more stable sea/boat conditions to develop drive. Also re your comment about heeling - trimarans can heel up to as much as 15 degrees so it will not be a non heeling experience. My yacht Footprints heels to just a bit more than 15 degrees so the experience is similar. I actually enjoy heeling in a yacht, (provided it is not extreme), which is one of the reasons I prefer a trimaran over a catamaran.

    I think a catamaran is the ideal multihull platform for a junk rig, and that of a sail to each hull.

    Last modified: 07 Mar 2016 07:09 | Deleted user
  • 06 Mar 2016 20:10
    Reply # 3864458 on 3781386

    Hello all,

    I am glad to see that I am not alone in my interest in a Junk-rigged multihull. I spent some time looking into this last year, and ran into some significant roadblocks.

    My original thinking was to marry the junk rig (for its cruiser friendliness) to a multihull of about 11m, (for its comfort) to create a nice, low-stress offshore cruising platform. I quickly found out that this was not an endorsed combination. For trimarans, the structural changes to accommodate an aluminum flagpole forward of the designed mast position were daunting. A designer of a popular model I spoke with did not want to entertain the idea at all. Similarly, for a catamaran, the bi-plane arrangement also encountered staunch resistance from its designer as well. That project looked to be more straightforward, but inevitably it involves a mast/flagpole puncturing the location of a bunk or the head in the current plans.

    The additional frustrating thing I ran into was, inevitably, people assumed the JR idea was a cost-savings maneuver, and recommended I pick up a used Bermuda set up, and stick with that. Of course, by the time one added up all the necessary replacement bits and pieces and extra sails needed make to make a Bermuda rig safe offshore, it was never actually cheap.

    So I am at a bit of an impasse. I think trimarans are a better design until you get above 12.5m length, because only at that point can you naturally accommodate standing headroom in the catamaran hulls without incurring too much windage. Plus a trimaran main hull (especially with solid decks and thus outboard bunks) works better as a unified space. Many of the good points about monohull interior design still apply, so you can take advantage of all that has been developed for them.

    I am aware of the substantial cost differential between a good used monohull and trimaran; there are some great deals out there on solid older multihulls. But, personally, I hate leaning over when the wind kicks up. It just seems like one of those things we should engineer out of the sailing experience, to increase comfort. We already look to warm clothes to help us deal with cold weather, and cockpit enclosures to shield us from annoying wind blowing square in our faces, so for comfort (and safety) let's do something about all that leaning too. So it is a multihull for me. With a JR, if I can swing it.

    Last modified: 06 Mar 2016 20:13 | Anonymous member
  • 04 Feb 2016 20:28
    Reply # 3801276 on 3781386
    Deleted user

    When rigging a multihull (Cat or Tri) it is important to keep weight away from the ends.

    In particular, steering will be compamised if you ar bow heavy. As they a light weight (in comparison to a Mono with its keel) Multis can be a problem to tack, being stopped by head seas and not carrying way like a heavy mono. Wharrams are of the classic type (V shaped hull, effectivly long keel) are well known to have this tacking problem which is more due to the long keel form than anything. If you want to go this route, pick a Cat or Tri design with a retractable dagger-board or centeplate which will help. One final point. The all up weght of JR mast and battened sail is greater in proportion when fitted to a multi (loading any multihull is an art!!!) then when on a full bodied mono which is much less effected by gear you put aboard. 

  • 04 Feb 2016 18:53
    Reply # 3801108 on 3781386
    Deleted user

    Ed, you will need to think about how you are going to support the unstayed mast in the center of the boat. This is the beauty of a mast in each hull, there is sufficient bury for the free standing masts to be well supported, but on a small cat such as you are thinking of building stepping the masts through the hulls could have a negative impact on use of the interior space. For a free standing mast in the center of the boat you will need a substantial supporting structure built above the main beam. Because of the wider beam of a catamaran it might be possible to stay the mast but that could compromise the use of the junk sail.

    Lots of fun stuff to think about!


  • 04 Feb 2016 18:30
    Reply # 3801079 on 3781386
    Deleted user

    Thanks David

    I would prefer not to have two masts mainly because of the additional cost and work for a single handed sailor. If I correctly understand what you wrote I would need a “low aspect” rig for a central mounted mast. 

    Here is the WHARRAM TANE Design Data... Could you recommend a Low Aspect “stock” cambered JR sail based on this information only?

    TANE Design Data

    WL lg 7.18m 23‘ 7“

    Lg OA 8.61m 28‘ 3“

    Beam OA 3.18m 12‘ 6“

    Beam ea Hull 1.14m 3‘ 9“

    Draft .50m 1‘ 8“

    Wt. empty 1 ton

    Load capacity 1 ton

    Rig Bermudan Cutter

    Work Sail Area 28.8sq 310sq ft

    Max Sail Area 35.7m sq 384sq ft

    Construction Material GRP

    I’m sure you can tell I am not very familiar with JR rigs, so I guess the un-stayed mast dimensions will be based on the sail size?

    My goal is to have a comfortable cruising boat that sails pretty flat, easy sail handling and can be single handed. Not particular interested in speed!

    Hope I haven’t ask for too much.

    Ed


  • 03 Feb 2016 01:31
    Reply # 3797046 on 3781386

    I find "excessive turbulence" rather meaningless. Junk-rigged cruising multihulls sail under the same kind of aerodynamic conditions as do monohulls. True, a slim, light racing multi will have its apparent wind always well ahead, and this will not play to the strength of junk rig, which is at its best with freed sheets.

    It's easy with a cat. Just design two equal junk rigs, of whatever type takes your fancy, and pop one in each hull. I think I remember that James Wharram has taken the view that rigs for his boats should be low, as they are in general rather narrower than some others. If that's the case, low aspect fanned sails would be one option.

  • 02 Feb 2016 23:37
    Reply # 3796877 on 3781386
    Deleted user

    Thanks Mark... Have been looking for information on multihull junk rigs for more that two years. That was one of the reasons I joined JRA.

    None of the DYI multihull designers I know of, design Junk Rigs for their designs. James Wharram did at one time but no longer does so, and he states in his Design Catalog;

    “Junk Rigs (discontinued). Over the years we have designed Junk Rigs for the Hina, Tane, Tangaroa Mk. I, Narai, Oro and Tehini. They were found unsuitable, especially on the slimmer designs, due to excessive turbulence caused by higher (than mono-hull) multihull speeds.”

    I find the part about “excessive turbulence” a bit confusing. If some of you out there in Junk Rig land could enlighten me on what he means, I would appreciate it . I love his Classic Designs, and have lease plans for the Maui, Hina, Tane and Tangaroa purchased back in the 1970‘s... but never had the opportunity to construct any one of them. I now have that opportunity and hope to finally get one built, and I surely want to have a Junk Rig on it!

    Ed


    Last modified: 02 Feb 2016 23:38 | Deleted user
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