Junk Rigged Trimaran

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  • 09 Oct 2020 17:37
    Reply # 9294270 on 9294098
    Anonymous wrote:


    bi plane trimaran!  Have you been smoking herbal cigarettes?  Can’t think why such weird  concepts should be aired on the website!!

    ....but seriously, it might work, but not many trimarans would suit it.  What the effect of the large separation would have on the balance is intriguing 


        I don't use mind altering substances of any kind... used to use alcohol in moderation but I don't even do that anymore   ;-)    I just like to toy with outside the box ideas...  Speculation is harmless I think.    What good are ideas and "weird" concepts if they are not aired / shared?

         I keep forgetting that the JRA is a den of conventional thinkers ;-)

    Seriously, the Tristar series is probably better suited for this kind of thing than most trimarans.   If you take a look at the structure.   It is fully decked all the way to the gunnels.  The interior wing deck contains berths and extends all the way out also with a substantial structural bulkhead at both the head and foot of the wing berths.  Note that you can see the forward bulkhead in the photo below, the aft one is the aft end of the cabin.  The bury potential in the amas is greater than most trimarans due to this full wing,  the logical mast location would be just forward of this bulkhead, and a bit of "creative engineering" could result in a very strong mast step and partner relative to the mast height and loading.

         The advantages of the biplane are fairly obvious in this case where a large mast trunk would block access forward.... Not to mention having the entire deck clear during trade wind sailing wing and wong.  The Tristar has a beautiful full unobstructed deck except for the mast.

          Arne's comments about handling sails "way out there" is no different than on a biplane catamaran.... with the full deck and width, nor is "catching things" a valid observation IMHO.  With a biplane rig you can fly just a single sail over the deck depending on the tack if that is a concern. It really differs from a biplane cat ONLY in the fact that you get a little more heel.  

         Later note:   The fact that there are two masts, one in each ama, counteracts any concerns about putting the mast weight out on the ama... the opposite mast balances it out so that it is carried on the main hull effectively.  I see few obstacles in this particular case at least... other than thinking mired deeply in convention.

          I have to confess that every time I see a tristar and think about a junk rig on it, my thoughts go in that direction.  I'm not known for doing conventional things or thinking conventional thoughts.... I have a bit of a "mad scientist" reputation.... deserved.... and my home and shop are full of different and innovative solutions.  


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    Last modified: 29 Oct 2020 15:42 | Anonymous member
  • 09 Oct 2020 15:59
    Reply # 9294106 on 9243770

    I am afraid that the Covid crisis has become an issue and this purchase is not going ahead.  
    There is a somewhat bigger more expensive trimaran in Jersey, a Speed 944 that looks like another bargain, though travel to Jersey and back may not be possible for some time.  
    Thanks to all for advice and encouragement so far.

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  • 09 Oct 2020 15:53
    Reply # 9294098 on 9243770


    bi plane trimaran!  Have you been smoking herbal cigarettes?  Can’t think why such weird  concepts should be aired on the website!!

    ....but seriously, it might work, but not many trimarans would suit it.  What the effect of the large separation would have on the balance is intriguing 

  • 09 Oct 2020 10:28
    Reply # 9293724 on 9243770
    Anonymous member (Administrator)

    a biplane rig in a trimaran does not sound like a good idea to me.

    • ·         A trimaran has plenty of sail-carrying stability, so can carry a single sail of decent size without problems. Why bother with two masts then?
    • ·         The amas are most probably not stressed for the torsion moment from masts put in them.
    • ·         The masts out there would be more likely to ‘catch stuff’ when coming alongside other boats, etc. It would also be awkward to work on the sail way out there.
    • ·         Two rigs add cost and complexity when building and handling, most probably without any gain in performance over a one-stick rig.

    I would only choose a 2-masted rig for these reasons:

    • ·         If the vessel is so big that a single sail becomes difficult to handle.
    • ·         If the vessel is very long, slim and lightweight, with moderate stability, something like a sharpie.


  • 08 Oct 2020 17:02
    Reply # 9291898 on 9243770

    The narrow accommodations on a trimaran would likely result in the mast being in a bad place as you would naturally want it next to a major bulkhead for lateral support.   That bulkhead would be the one between the saloon and the heads compartment putting it right in the middle of a doorway forward.   I looked at this on the Searunner 31 a few years ago, and determined that the mast (at Arne's suggestion) should be offset to one side enough to provide access.  

    The Tristar 24 has only about 30M of sail area... I wonder how a biplane rig would work out on a trimaran like this.  Masts could be kept fairly light weight due to small sail area, lower air draft, perhaps even using readily available carbon fiber masts for the upper sections.  The downward pressure on the amas when heeling would probably be less than  with a single taller mast, making ama displacement a non issue in that respect.  Imagine having that big beautiful deck completely or mostly clear of sails and rigging much of the time.

        I've never seen or heard of a biplane trimaran.... Conventional thinking would be that since nobody's done it, it's a bad idea, but in my experience that is not necessarily the case.  


  • 19 Sep 2020 09:46
    Reply # 9248015 on 9243770

    Thanks for all your encouragement. And David for loans etc. 

    Will post agsin as things develop.

  • 18 Sep 2020 07:37
    Reply # 9245070 on 9243770
    Mark wrote:

    To keep more cash for the conversion, if anyone could help out with accommodation close to Emsworth (if I need an early train)  or another close by train station, that would be appreciated.  I also will have to get a pilot book and back up paper charts, which I am unlike to use again, but photo copies would suffice if anyone could help out.

    You can have my old copy of the Lundy and Irish Sea Pilot, by David Taylor, (1994), borrow such of the Martin Lawrence pilots for Scottish waters as you need; and borrow such paper charts as I have (but with iSailor chart app on an iPad for reliable navigation, I can't remember when I last looked at them).
  • 18 Sep 2020 07:24
    Reply # 9245061 on 9243770

    Good to hear, Mark.

    Can I suggest Ravenglass as a staging post up the Irish Sea, for workshop if needed, crew changeovers possible with a train station and free accommodation available, and if you really want to make a wing sail, the chance to pick up the moulds for the luff formers and forward battens ends, plus kevlar for making them, and the chance to study the rig at close quarters and see how it goes together - I'll be leaving the sail on this winter, with a cover on. The wing sail would be a good choice for a trimaran, I think.

  • 18 Sep 2020 07:18
    Reply # 9245052 on 9243770

    What a fantastic project Mark.

    At 1st glance it looks like the new JR stick may be right in the crapper. :-)

    Yellow is either a popular livery for these boats or this might be the one you bought.

    Tristar 24 on Yachtsnet

    As others have said this is going to be a great project to follow.

    I wish you fun and good fortune.

    3 files
  • 18 Sep 2020 06:45
    Reply # 9245033 on 9243770

    That is a nice looking little trimaran, and very up to date appearance with the plumb stems. It would also seem to have a very useable accommodation for such a small trimaran, based on a quick view of the Horstman trimarans website. The flush deck set up should make it easier to install a freestanding mast. The displacement of the design will allow for the extra weight of the junk rig. I also will follow with interest.

    Last modified: 18 Sep 2020 06:52 | Anonymous member
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