Small trimaran with Tornado centerhull

Discussion in 'Multihulls' started by revintage, Dec 25, 2021.

  1. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    Hi trip....
    Good idea! Just what I suggested myself a few posts above: "Checked out Kurt Hughes site and got the idea to add a "sea-sole" as on the 16" daysailer".
    But as the center hull is low, it has to be built above the gunwale, with the deck between the beams cut open. Might be added after the initial build, if she sails good enough.
     
  2. trip the light fandango
    Joined: Apr 2018
    Posts: 490
    Likes: 98, Points: 28
    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    I was thinking centre hull displacement , less wetted surface and more planing surface- lower speed before lift off to make an allowance for the potential weight issue, but it does add more weight and adds more work..ha. Another interesting project revintage.
     
    revintage likes this.
  3. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    Have plenty of time to absorb ideas from you all. At the moment it is my foiler build, that gets the attention.
     
    Last edited: Dec 30, 2021
  4. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    Found this on Pinterest. Looks like a Nacra 6.0 with unknown centerhull with a Laser on top;).

    6laser.png
     
  5. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    Checked out the aluminium tube storage and this is what I had for making beams. The waterstays will be connected at the ends of the 110mm main beam and 4" rear beam tubes.
    tritopsea.png
     
    Last edited: Dec 31, 2021
    oldmulti likes this.
  6. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    I have two possible solutions for the main beam waterstays, either standard with separate waterstays for anchored in each side of the hull or the dolphin striker version I designed for my foiler. I like the thought of a prebent beam like on a catamaran with less force on the main hull.

    dolphin.png

    The rear beam will use another solution that I also designed for the foiler.

    newrearwaterstaynew.png
     
  7. Corley
    Joined: Oct 2009
    Posts: 3,777
    Likes: 194, Points: 63, Legacy Rep: 826
    Location: Melbourne, Australia

    Corley epoxy coated

    My inclination would be to anchor a low friction ring against the hull with glass or carbon unis and fan the unidirectional out across an internal bulkhead. I'm not sure on dyneema susceptibility to off axis loads I'm guessing it's not high and pulling it around a hard corner like that will subject it to chafe. I'd use some sort of purpose made block for adjusting the waterstays I know colligo make some bobstay adjusters that may do the trick.

    The other option is simply fit beams that are strong enough in cantilever mode, they wouldn't need to be that strong on a small boat some people use broken carbon masts for a source material. I know you don't want to buy anything for this build but wound carbon tubes are pretty affordable these days and many integrate fibres along the 0 axis making them strong where you need them. Waterstays are a bit of a problem when you don't have much freeboard as if they contact even small wavetops they slow you down a lot.
     
  8. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    Hi Corley,
    I guess you are referring to the rear beam. Checked the forces and the upwards force is ca 25% of the force from the waterstay. As you point out the hard corner, where the upward force might be a problem. My idea was to add a flared stainless tube with an acceptable radius, so we can probably rule out the chafe problem. My guesstimate is that the waterstay tension for the rear beam is less than 300kg, so I am not worried.

    What interests me more is the difference between the two main beam alternatives, where I am not sure if the dolphin striker version actually works for trimarans? I have not tried to do the math here, where the windward shroud tension(due to healing moment) and the upward thrust from the leeward ama are the two components working against the waterstays. Sorry if I am a little unclear here, as English is not my native language.
    upload_2022-1-1_1-24-4.jpeg
     
  9. Corley
    Joined: Oct 2009
    Posts: 3,777
    Likes: 194, Points: 63, Legacy Rep: 826
    Location: Melbourne, Australia

    Corley epoxy coated

    I wouldn't worry about a dolphin striker on a trimaran better to put a compression bulkhead under the mast which is the main purpose of a dolphin striker to resist mast compression loads not for beam strength.
     
  10. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    Yep, but it´s not compression loads I worry about. It is the waterstay forces on the crappy hull and the addition of fittings and bulkhead that I want to avoid. With the dolphin striker there are close to none on the hull and there is very little work to build it. It would be interesting with a technical discussion to find out, if my "outside the box" solution is weaker or has any major culprits.
    Will anyway find out this summer, as I will try it on my trimaran foiler.
    dolpinstrikertri8.png
    The 2nd image shows the tubing before laminating all joints with carbon fiber.
    IMG_9386.JPG
    Will add a G10/cf bulkhead for the forestay like on the foiler, though.
    forestaybh.png skott.png
     
    Last edited: Jan 1, 2022
  11. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    When I widened my Nacra 5.5 from 2.6m to 3m we added sleeves to the original rear beam, made from 100x5mm 6082-T6. As the main beam was rotten, I made a new and stronger one from 100x2mm instead of the original 4"x1.6mm. Had to sleeve that one too, as it was a little to short.
    Got the idea to use both beams as they are, adding 90x2mm and 90x3mm tubing for the remaining 800mm/side, to make them 4500mm.
    This way I only have to remove the striker band(if adding a bulkhead, the striker rod also goes) and buy 2 pcs 1200mm 90x3mm for the main beam. 90x2mm for the rear beam is in stock.
    Did some simple load cases of the beams and the tri should anyway be strong enough, in the small lake it will be sailed.
    A full resolution sketch can be found here: http://soderquist.se/trirearbeamlong.png
    trirearbeamlong.png
    IMG_0404.JPG
     
    Last edited: Jan 2, 2022
    oldmulti likes this.
  12. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    It´s a fortnight since I got the idea about a trimaran for the flat water lake at my summer house. After having studied the beam design of Buccaneer 24 I did some back engineering and learned a lot.
    I have had quite a handfull ideas, but now landed in a solution, where I keep as much as possible from the widened 5.5/F18 and keep the alterations and loads of the Tornado hull to a minimum. The 5.5 will be easy to reassemble if I want to. The cockpit, where the Tornado hull deck will be cut open and the centerboard box removed, will not be built, until the boat is sailing OK.
    The beams are unchanged and only lengthened with four 90mm tubes and added synthetic water stays.
    The shrouds are attached to the original 5.5 chain plates. Forestays are doubled and attached to the 5.5 bow chain plates at each hull inside like on an A-class cat.

    A third "forestay" is then attached to the slightly altered and centered Tornado bow chain plate, to be used only for hoisting the 5.35 sqm self tacking Tornado jib.

    Probably this is an odd solution, please point out the mistakes you find. Plenty of time to correct them, as the build will not begin until autumn.

    tritopacat.png

    longbeams.png
     
    Last edited: Jan 10, 2022
    oldmulti likes this.
  13. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    After having seen the badly abused Panthercraft Tornado hull yesterday, I doubt it would take any external loads at all. It would not be to hard to patch the sandwich hull up, if using it as a center float only. On the positive side, it´s free and the lower parts of the hull are in acceptable shape.
    With a quite a few meters of Dyneema, a cobweb could be shaped to probably solve this, as the Tornado jib´s tack is will be quite a bit above the hull decks. Without spinnaker it would be even easier to solve. Used a random image from internet of a Nacra 5.5 cat to show the idea.
    IMG_9566.JPG IMG_9580.JPG IMG_9574.JPG IMG_9579.JPG 5.5nospitri.png 5.5spitri.png tritopacatwofore.png
     
    Last edited: Jan 12, 2022
  14. revintage
    Joined: Nov 2016
    Posts: 328
    Likes: 62, Points: 28, Legacy Rep: 10
    Location: Sweden

    revintage Senior Member

    I am doubtful about the choice of cross beams.
    A few years ago I made 3.2m beams for a widened Nacra 5.8 beachcat project, but they are still resting in my workshop. The main beam is made from 100x2mm 6060-T6, has internal 96x3mm reinforcements and a 40x3mm stainless striker band. The rear beam is from 100x3mm round tube with a Harken traveler track on top. Each end of the beams will be lengthened 600mm with 90x2mm tubes t0 reach 4400 mm total beam length.
    Have done a few SIMPLE load cases, but I am not sure how to interpret them, as the force distribution between front and rear crossbeam is unknown. I have compared my main beam by reverse engineering the beams of the Buccaneer24 and it should cope with the loads from the below 400kg boat weight including crew.
    As it is flat water lake sailing in moderate winds well under 20 knots, I will anyway try this without further calculations.

    beam.jpg

    beamload.png
     

  15. trip the light fandango
    Joined: Apr 2018
    Posts: 490
    Likes: 98, Points: 28
    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    The track for the traveller should add some strength on the rear beam. Old multi has detailed some succesfull older multi's that use aluminium tube wrapped in fibreglass as frame, kevlar may be the best option, sockets with knees for floats and shoulders[ha] for main could distribute load, that only leaves the centre point between main and floats,.. .
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.