Mashup Trimaran (continued)

Discussion in 'Multihulls' started by Bigfork, Feb 17, 2021.

  1. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . . .

    Spread the load, shed the water, increase reserve buoyancy, lighten the boat.
    Make them out of foam and epoxyglass the s*#t out of them.
     
  2. Bigfork
    Joined: Dec 2009
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    Location: Montana, USA

    Bigfork Junior Member

    beam mock up.jpg front beam.JPG Inkedcloseup of beam gaps_LI.jpg


    Greetings folks!
    Still tootling along here. An hour here, an hour there, and then several hour blitzes where I can :).
    The first picture is the first time I've got to see the beam ends mocked onto the port float. I like the subtle curve of the front beam...gives it a slightly modern look. I can't wait to see what it looks like sitting in the water! The float will be at a 8* cant relative to plumb, which is why the beam ends appear to point upward at said degree. Currently, the float is sitting "plumb/level" to facilitate the joinery. One can envision the hinge point and the float folding up and over, a-la W17 style.

    Once the beams are glassed, it will be time to mount the main beams to the H18 main hull. My garage won't let me do a full 14' wide assembly so it will have to happen in halves, ie main hull/beams fit to port float and then the mirror the process on the starboard side. The last step of the fit will be mounting the floats to the hinging beam end. I'll chalkline snap a layout grid on the ground (like doing log work) and use a 4' level and lasers to true, rack, and square the floats to the main hull (and then there's the thought of slight "toe-in".....how much?) I've also got to settle on a hinge design. I'd like to build my own glass hinges, 8 in total (two per joint). At any point, I could add water stays. I'd like to see it float with mock weight before I go that direction.

    More than an update, I do have one silly question for the collective brain: A picture show the closeup of the aft beam. I managed to build in a slight gap (circled in red) here and there when I sheeted the top and bottom sides. I plan on putting a 1/4" roundover on all four corners to facilitate better glassing, but should I first fill the slight gaps with thickened (West 406 or 405, colloidal silica or filliting blend)? Or should I not worry about it and just round-over and glass fab.

    Thanks for the thoughts!
    cheers.
     
  3. Bigfork
    Joined: Dec 2009
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    Location: Montana, USA

    Bigfork Junior Member

    Oh yeah... one more silly question.
    If I want to use any marine filler to fair or otherwise "smooth" transitions in sheeting (like where there is a joint between sheets but there not perfectly fair to eachother), should I do that before or after glass fabric.
    thanks.
     
  4. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . . .

    Before but at the same time so the cloth is going on over uncured filler.
     
  5. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    If you use microballoons with a little silica you will easily be able to fair the joins before glassing, as blue bell says uncured is ideal, but before fully cured is 36 hours or so, just hard enough to remove excess with a blade and light sand could be 3 or so hours, your call. Don't use acetone to clean the extra, big risk of spoiling the bond with ply in that time frame.
    Carbosil I haven't used but silica/resin is a lot harder than ply when cured.

    I've had a go at nutting out hinges too a little different to you but perhaps my ideas will be helpful.

    I think the easiest[ha] way is to do the lay ups of the hinges is with an ally tube that spans the distance between front and rear sets of hinges, to assure alignment. Mine would have 3 hinge parts 2 outside making a fork, 1 centre inside, the aluminium tube could be used as the shaft and the length inbetween cut out when everything is completed, especially main hull joins.
    You can sleeve the tube at the hinge for strength but leaving the tube in place permanently means pretty thick walls/weight

    I've left a few bits out like the what method secures the hinges when underway to stop them from flopping up and down, but that's easy compared to making and aligning hinges.

    The last connections would be each lay up to the centre hull, held in place with enough adjustment in the support frame/jig to see whether the hinges/angles want to go.
    I'm glad your doing it first, ha, I've shelved that concept for down the track, too much extra work so it can wait for a coupla years. Plus I get to see how yours works then,.
    great stuff Big Fork
     
  6. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Cedar is as light as you are going to get for a wood piece.
    What are you two talking about??????
     
  7. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . . .

    Ya, cedar's pretty light for a piece of wood, especially if you drill holes in it.
    Which "two" are you referring to?
    Have you read or followed the thread?
     
  8. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    Really ? What about Kiri/Paulownia?
    Or Balsa. So what are you talking about ?
     
  9. Bigfork
    Joined: Dec 2009
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    Location: Montana, USA

    Bigfork Junior Member

    Hey there folks,
    My mention of cedar was mostly just because that's what I have lying around...really it's just what was at hand. I realize there are lighter woods out there. My plan was to use a small 'block' of cedar oriented vertically (compressive strength) to fix the float arm to the hull. As this project is a learning experience and very fluid in its design, alas I have scuttled the idea in favor of shaving weight. Instead I am going to bond, glass, and brace the anchor point skipping the need for the permanent fixatives at these locations. I'll probably use a temporary stainless 1/4 to secure the float to the arm, then bed and glass/brace, then remove the steel.

    Got a jug of West micro-balloons to fill/fair so that's the next treatment for the beams...then glass fabric. And there's the hinges....they'll take some time... then the pre-fit and alignment... then transom plugs and other odds and ends.... then, maybe by spring, a float test! The float test will tell a lot as far as dihedral, buoyancy, and float to main hull relativity. The whole lot could go in the bin at that point if it's deemed hopelessly heavy or otherwise frigged. Towards the beginning of this I'm quite sure I was overbuilding; now I think I'm on the edge of under-building. Without proper engineering sample tests, there's no telling how strong components like beams are...other than intuition (and there's been lots of that).

    Cheers
     
  10. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Cover with 4 to 6 ounce, tape your joins avoid right angles with filler, lap your main beam /hull/ amas joins to increase load spread, don't sand through the mat.
     
    BlueBell likes this.

  11. Bigfork
    Joined: Dec 2009
    Posts: 74
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    Location: Montana, USA

    Bigfork Junior Member

    IMG_4505.JPG IMG_4551.JPG IMG_4578.JPG IMG_4619.JPG IMG_4626.JPG

    Hey forum folks!
    Well my folly is still alive. I just finished the hinges: 16 "paddles" or 8 hinge sets. Took me about 2 months of an hour here and there!! Very labor intensive but I became more efficient as the process moved along. Each paddle is 7 layers of 13oz uni with 1 layer of 10oz bi. I haven't weighed them yet, but I think they're much lighter than the equivalent in stainless.

    I ordered the plans from Mike Waters based upon use for his W17. Frankly, I've sourced alot of info from his website and through emails with him. His site is an amazing resource for the DIY ply builder! He pointed out that my Hobie 18 main hull is under displacement for what I'm trying to achieve...related to dihedral. I sort of knew this... had a hunch. Obviously I don't want to be dragging 3 hulls through the water. I'm increasing dihedral so that when my (heavy) main hull is sitting at estimated waterline, the floats will be just touching. Means I need to add about 5" to my main beam mounting surface. And I need to do it with weight in mind.
    (famous last words, but...) I hope to have a float test this fall. Fun Fun.

    cheers folks,
    bones
     
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