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Thread: Triscarf

  1. #1
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    Default Triscarf

    Very rough sketch of a minimalist Triscarf.

    The idea is for a folding and easy transport of a craft for exploring small rivers easily. Some of the design features:
    Floats 2.8m sealed for buoyancy, provide lateral resistance. Simple ply construction weight approximately 6-8kg. May change to asymmetric shape.
    LOA 4m.
    Front float with canard rudder, provides lateral stability and steering.
    Sail roller furling on unstayed mast. Mast supported with low mast struts.
    Alternative propulsion row with fixed seat.

    Still lots to think about but hopefully I have managed to communicate the basic concept. How exactly the helm sits comfortably and the 'platform' structure and construction to be resolved.


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  2. #2
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    Default Re: Triscarf

    Canards are notoriously directionally unstable. They only work on aircraft because the are designed to work in only one direction, and are adjusted to vary a positive element of lift. Reduce the lift to let the nose drop, increase the lift to climb.
    Put the rudder at the back like any sensible boat builder.
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
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    Default Re: Triscarf

    Hi Tink, I do enjoy your ideas. Have you seen Newman Darby's mini trimarans?:

    http://www.ayrs.org/catalyst/Catalyst_N19_Jan_2005.pdf

    He seems to have been after some of the same qualities that you are chasing.

    I think you are onto something by distributing small floats to achieve the feeling of a larger boat.

  4. #4
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    Default Re: Triscarf

    Very interesting!! I like it. Have you thought about the possibility laminating a hoop that joins the two hulls together at their sterns and sticks up high enough to mount the main sheet purchase to avoid the complication of a boom? It could possibly have a traveler along the entire length of the hoop. The hoop could be removable for transport on vehicle. Feel free to use that idea and good luck with your design.

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    Default Re: Triscarf

    don't stop now, you're on a roll



    sw
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  6. #6
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    Default Re: Triscarf

    Quote Originally Posted by Peerie Maa View Post
    Canards are notoriously directionally unstable. They only work on aircraft because the are designed to work in only one direction, and are adjusted to vary a positive element of lift. Reduce the lift to let the nose drop, increase the lift to climb.
    Put the rudder at the back like any sensible boat builder.
    Thanks for the advice, probably not departing too far from conventional wisdom would be a good idea.

  7. #7
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    Default Re: Triscarf

    Quote Originally Posted by Clarkey View Post
    Hi Tink, I do enjoy your ideas. Have you seen Newman Darby's mini trimarans?:

    http://www.ayrs.org/catalyst/Catalyst_N19_Jan_2005.pdf

    He seems to have been after some of the same qualities that you are chasing.

    I think you are onto something by distributing small floats to achieve the feeling of a larger boat.
    Big thanks for the link, very interesting yes totally what I am trying to achieve. A sailboat is going to need buoyancy tanks so why not build the tanks and eliminate most of the other bits of the boat.

  8. #8
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    Default Re: Triscarf

    Quote Originally Posted by swoody126 View Post
    don't stop now, you're on a roll



    sw
    I actually started building one about thirty years again. An old proa had reached the end of it's life so I cut the Vaka in half as the floats, the Ama received a similar fate to be the front float. Then a lovely cold moulded International Canoe took my fancy and I had to move out of my workshop and had to stop the project.

  9. #9
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    Default Re: Triscarf

    Quote Originally Posted by kenjamin View Post
    Very interesting!! I like it. Have you thought about the possibility laminating a hoop that joins the two hulls together at their sterns and sticks up high enough to mount the main sheet purchase to avoid the complication of a boom? It could possibly have a traveler along the entire length of the hoop. The hoop could be removable for transport on vehicle. Feel free to use that idea and good luck with your design.
    Thanks, I did think by using the beam I could use track / traveller like a catamaran and eliminate the boom and make the roller reefing work better

  10. #10
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    Default

    Lateral float moved aft, push pull rudder added to this. Still lots thinking to do




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    Default Re: Triscarf

    That is beginning to look really interesting - is there a specific reason that you are restricting beam? It looks a little narrow?

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    Quote Originally Posted by Clarkey View Post
    That is beginning to look really interesting - is there a specific reason that you are restricting beam? It looks a little narrow?

    The first thought is that it should be cartopable and minimal assembly required. At the moment the width is 1465mm. My car width is 1700mm with standard roof bars at 1200mm but longer ones 1500mm.

    Thinking that the longer length of the craft will help getting it on the rack with the middle float telescoping for transport.

    My primary design requirement is to get it from storage to the water as quickly and easily as possible.




    I am just exploring ideas at the moment, just see where in leads, probably a few blind alleys on this journey.



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  13. #13
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    Default

    Have to stop for the night but this as a trampoline version.



    Thinking of creating a bench seat from the trampoline like a Hansa 303 wide, needs and additional beam which I haven't yet drawn




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  14. #14
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    Default Re: Triscarf

    Why not just put rudders on each hull... a la Hobie? As soon as you heel, you will have steering issues with it on the centreline. Less components to build, less to set up at launch.

    You must have a trampoline to shift ballast.

    I dont know know what the smallest hobie is.. 15'? They are demountable.

    Even if you are set on building one, I'd look at proven designs, and more importantly, their proportions and go from there as a starting point.

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    Default Re: Triscarf

    Might be worth looking at the Blokart seating arrangement - they can be mounted to cat hulls to form the 'Katalyst':



    Interestingly they arrived at the cat configuration after trying this:


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    Default Re: Triscarf

    Quote Originally Posted by lupussonic View Post
    Why not just put rudders on each hull... a la Hobie? As soon as you heel, you will have steering issues with it on the centreline. Less components to build, less to set up at launch.

    You must have a trampoline to shift ballast.

    I dont know know what the smallest hobie is.. 15'? They are demountable.

    Even if you are set on building one, I'd look at proven designs, and more importantly, their proportions and go from there as a starting point.
    Thanks for your reply, I value all input as I am just thinking in public and fully appreciate I am perhaps going down some blind alley - I love the process.

    My primary design requirement is simplicity of storage, transportation, assembly and launching. Speed is very secondary, in line with a 12 foot displacement dinghy will be fine. I am considering trampolines but prefer central seating, ultimate righting moment is of little importance for short tacking up a narrow river.

    Small component parts are important, working on sub 3meters (12 foot), nearer 2meters length parts is my target, the extra length and float adds lateral stability without adding too much volume / weight.

  17. #17
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    Default Re: Triscarf

    Quote Originally Posted by Clarkey View Post
    Might be worth looking at the Blokart seating arrangement - they can be mounted to cat hulls to form the 'Katalyst':



    Interestingly they arrived at the cat configuration after trying this:

    Thanks for the input, I do like the central seat. For my requirements I have to say the B&W photo is much more appealing because of the small part size. In all design the devil and ultimately success is in the detail but also not moving too far from the current norm. The mast support is along the lines I was thinking.

  18. #18
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    Default

    Thought I'd post the latest thoughts.
    Have reduced the length of the floats to 1800mm (5.9ft). The seating platform is skid shape and provide some buoyancy, though not if swamped. The crew can move from side to side on the seating platform. The platform would have multiple locations fore and aft to get the trim correct. I have gone for a balanced lug because it gets the centre of effort where it is needed and has short spars. Construction would allow the addition of a skeg or even a long keel to get the balance right.

    Not a craft for most but I feel it does meet my particular requirements. I am still at a very rough stage and letting time percolate the design.










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  19. #19
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    Default

    1.8mm (6ft) wide.





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  20. #20
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    Default

    1600mm - 5' 4" on top of a very rough estimate of a Honda Jazz








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  21. #21
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    Default

    Lots mor thinking.
    Added an adjustable mast step and decided by changing the height of the lateral float I would have enough adjustments to create monocoque hulls and decking. I have created a CAD model of sufficient detail to confidently say the main hull would be sub 25kg and nearer to 20kg.




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  22. #22
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    More development:
    Crew moved aft
    Benches added
    Construction details refined
    Stability calculations confirm lateral stability
    Cartoping method reviewed



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  23. #23
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    Default Re: Triscarf

    Interesting design. Thanks for posting. Do you need that hydrodynamically dirty float at the back or can you just terminate the tube like Buckminster Fuller's needles rowing cat and rely on the tubes volume for buoyancy? Or perhaps all that wetted surface would be worse than the float trying to exceed hull speed? Please ignore this post if you wish.
    Last edited by Al G; 08-19-2017 at 02:51 AM.

  24. #24
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    Default Re: Triscarf

    Quote Originally Posted by Al G View Post
    Interesting design. Thanks for posting. Do you need that hydrodynamically dirty float at the back or can you just terminate the tube like Buckminster Fuller's needles rowing cat and rely on the tubes volume for buoyancy? Or perhaps all that wetted surface would be worse than the float trying to exceed hull speed? Please ignore this post if you wish.
    Or somewhere between the two approaches with the tube terminating simply with a buoyant (foam?) rudder?

  25. #25
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    Default Re: Triscarf

    Thanks for the feedback Al G and Clarkey

    to be honest the float has been given very little thought, based on the configuration it needs to provide 30kgm of moment to stop the craft nose diving (tube and float) and support the rudder - anything else up for grabs. The reason fo the hydrodynamicly dirt float is so that it is small enough to fit into the car. I will give it a bit more attention and figure out a direction

  26. #26
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    Default Re: Triscarf

    Moving the crew further aft is the obvious way to provide the anti-pitchpole moment - but if you are stuck on the long pole out the back then a winged rudder can achieve the same effect.

    http://www.onemetre.net/Build/WingRudr/WingRudr.htm - on small R/C boats but used on International moths for ages.
    Someday, I'm going to settle down and be a grumpy old man.

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    Default Re: Triscarf

    Back in '56, the old man built a tri at 16ft and to control pitch (it sat on a foil/wing) he used twin canted rudders. The 'tiller' could control direction by moving together, or, pitch by toeing the rudders in or out. (Similar to some aircraft, like the V-35 Beach Bonanza) Needless to say, it was extremely difficult to control and pitchpoles were frequent. It also had a hard wingsail. The two brave crew (father and a very tolerent friend) perched on the curved box plank that spanned the hulls. As a young sprog, I was not allowed anywhere near it, pity.

    I feel that the subject boat needs to be a bit longer in the floats (car does not restict that) It would not restrict set up time and lead to a much smoother motion. Even small waves would be uncomfortable with sub two metre floats, not to mention the rear float with rudder risking being out of the water, as it has no real mass.
    Going back to the B&W photo, stability also raises it's head, as it has the classic triangular problem of three wheeled cars that had the single one at the front. The distance from the centre of gravity is very close to the line connecting the front and rear wheels, leading to upsets at relatively low speeds. Worse, in a boat, as the best point of sailing would be beam reach, or with the wind aft of the beam. That could be why we don't see any of these today....

    Fun thread.

    A2

  28. #28
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    Default Re: Triscarf

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    Moving the crew further aft is the obvious way to provide the anti-pitchpole moment - but if you are stuck on the long pole out the back then a winged rudder can achieve the same effect.

    http://www.onemetre.net/Build/WingRudr/WingRudr.htm - on small R/C boats but used on International moths for ages.
    Thanks, a winged rudder was on my radar but not sure how it would cope at the low speed I envisage or with the log and weedy river I plan to sail on. Busy day sailing but if I can keep awake I will do some CAD tonight and post my current thoughts.

  29. #29
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    Default Re: Triscarf

    Quote Originally Posted by Andrew2 View Post
    Back in '56, the old man built a tri at 16ft and to control pitch (it sat on a foil/wing) he used twin canted rudders. The 'tiller' could control direction by moving together, or, pitch by toeing the rudders in or out. (Similar to some aircraft, like the V-35 Beach Bonanza) Needless to say, it was extremely difficult to control and pitchpoles were frequent. It also had a hard wingsail. The two brave crew (father and a very tolerent friend) perched on the curved box plank that spanned the hulls. As a young sprog, I was not allowed anywhere near it, pity.

    I feel that the subject boat needs to be a bit longer in the floats (car does not restict that) It would not restrict set up time and lead to a much smoother motion. Even small waves would be uncomfortable with sub two metre floats, not to mention the rear float with rudder risking being out of the water, as it has no real mass.
    Going back to the B&W photo, stability also raises it's head, as it has the classic triangular problem of three wheeled cars that had the single one at the front. The distance from the centre of gravity is very close to the line connecting the front and rear wheels, leading to upsets at relatively low speeds. Worse, in a boat, as the best point of sailing would be beam reach, or with the wind aft of the beam. That could be why we don't see any of these today....

    Fun thread.

    A2
    Some very valid points, I am taking the idea to limit to see where it leads, in reality it would need to be reined it a bit along the lines of your post.

  30. #30
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    Still free thinking and I am sure not to everyone's palate.

    The rear float and connecting tube would supply a moment between zero and thirty kilogram meters. Rather than making it heavy it would be water ballasted.

    The majority of the weight of the tube, float and buoyancy would be supported by a submerged SWATH type hull. The crew could then sit back a little to load up the thin displacement body and planing shoe.

    The next stage is to raise the submerged body and merge it into the displacement body which I feel would work better



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  31. #31
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    Default Re: Triscarf

    Being as their has been a lot of development in inflatable SUP's of late why not a couple of inflatable pontoons, car boot (trunk) rather than car top

  32. #32
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    Default Re: Triscarf

    I love seeing the thought process, but im left with the thought of whats wrong with something like an Optimist dinghy.....even a nesting one? Its starting to look more and more complicated than a craft you can just pull off the roof and go sailing.

  33. #33
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    Default Re: Triscarf

    I will admit to being utterly baffled by this but I've found the bits.....

    https://www.maidenheadsc.org.uk/main...ed-on-tri.html
    Someday, I'm going to settle down and be a grumpy old man.

  34. #34
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    Default Re: Triscarf

    Quote Originally Posted by artif View Post
    Being as their has been a lot of development in inflatable SUP's of late why not a couple of inflatable pontoons, car boot (trunk) rather than car top
    I have a couple of friends with inflatable SUPs and high end inflatable canoes, they are very impressive. I find it fun to explore other avenues

  35. #35
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    Default Re: Triscarf

    I have looked and played about with designs a bit bigger than an Optimist and I can only agree that there are many simpler ways to get what I want. Just seeing where this journey takes me.

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