Designing a 43' flat panel performance cruising catamaran

Discussion in 'Multihulls' started by sailhawaii, Jun 7, 2019.

  1. sailhawaii
    Joined: May 2016
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    Location: Indian Harbour Beach, FL

    sailhawaii Junior Member

    I'm working on a 43' CNC cut flat panel catamaran design. I just finished a 1:20 scale RC version of it.
    My current thinking it to open source or more correctly creative commons the plans.


    If I can get it refined to the level I like I plan to build a full size version. I shared a early drawing here a couple of years ago and nobody seemed to care for it. It's inspired by the Schioning Arrow series and the Grainger Raku series. Both of which I think are awesome boats.

    This is the build video showing the final RC version sailing:


    It's just a hobby for me, so if anyone wants to help contribute to the design of the project I would be happy to share it.
     
  2. oldmulti
    Joined: May 2019
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    Location: australia

    oldmulti Senior Member

    Hi. The model looks good and I like the concept of a flat panel construction method. I have seen 5 flat panel cats being made from 35 to 48 feet. They all eventually worked well but the panel layout and fitting really depended on a good basic design. Some flat panels get very stiff and difficult to twist into shape if to much glass is applied prior to placement. Also like all chine boats getting the chine or step lines to be visually acceptable can require a lot of fairing after the panels are taped together. The Harryproa site has an interesting way of producing cheap mold for EG hull bottoms that then may be able to be joined to a flat panel rest of the boat. PS over on the Multihull Structure Thoughts thread i will in the next few days do a post about cross beam structures for 40 odd feet cruiser racer cats.
     
  3. sailhawaii
    Joined: May 2016
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    Location: Indian Harbour Beach, FL

    sailhawaii Junior Member

    Thanks. The first models I build had some curves that were difficult to make with panel flex, but I changed the design so it's not a problem anymore (the problem areas seems to be the front of the bridge deck and the bow esp the inside) . I have seen the fairing problem you are talking about already on my models. The more accurate I get the panels including my notching system helps a little to improve that, but it's still an issue. I'm actually thinking about routing the core before any fiberglass is on it. Then I can route small tracks similar to drywall seams for an extra layer of glass tape at the seams. I may even attempt to route the foam at an angle to make a perfect fit. I have seen many full size kit airplanes that they are able to CNC the parts so that you don't have to even drill holes everything just lines up and you rivet it together. I'll see what my continued experimenting turns up to work.

    I've looked at the Harryproa site before I'll take a look again and keep an eye on the other thread.
     
  4. oldmulti
    Joined: May 2019
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    Location: australia

    oldmulti Senior Member

    Hi, look at the Multihull Structure Thoughts thread page 3 and 4 for some cross beam ideas that may help your design process.
     
    sailhawaii likes this.
  5. magwas
    Joined: Oct 2009
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    Location: Hungary

    magwas Senior Member

    What is your approach to size the aka to be structurally sound? I think that any plan should be backed by calculations or scantling rules. I guess I know how to size the amas based on a scantling rulebook, but the only ways I know for sizing the aka is either as classical beams (which is hard because the geometry), or finite element analysis (which I am too dumb to do).
     
  6. sailhawaii
    Joined: May 2016
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    Location: Indian Harbour Beach, FL

    sailhawaii Junior Member

    As I'm not a engineer, so my approach is as follows:
    1. Look at existing designs and make it similar (ok for model building, but not a good idea for full-size)
    2. Use the CAD program to do the finite element analysis (I may need to upgrade to do that)
    3. Pay a real engineer to check my work and specify mods or changes needed (I would never build full size without this)

    I plan to do all three, but only #3 as I get closer to building the full size boat.

    I'm not that far yet. I'm working to get my CP, and basic hydrostatics close based on estimated scantling rules. Also working on my composite building skills (vacuum bagging and resign infusion) on a small scale by building models. My first model is way too strong and way to heavy. Already made the panels for the second model, as soon as I get back from my business trip I hope to cut and assemble it.
     
  7. oldmulti
    Joined: May 2019
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    Location: australia

    oldmulti Senior Member

    Hi. I will in a week or so I will give you a quick and dirty way to estimate cruising catamaran main and rear crossbeams on Multihull Structure Thoughts. This is NOT a professional engineered approach but is based on reverse engineering my database of a hundred plus multihull structures.
     
  8. sailhawaii
    Joined: May 2016
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    Location: Indian Harbour Beach, FL

    sailhawaii Junior Member

    I've been following that thread religiously, studying everything you post as it really helps for stage #1, which I hope lands me close when/if I get to stage #3 of a professional engineer.
     
  9. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Looks great!
    I watched your video.
    WestSystem sells epoxy pumps for measuring.
     

  10. sailhawaii
    Joined: May 2016
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    Location: Indian Harbour Beach, FL

    sailhawaii Junior Member

    Thanks and thanks for watching the video.

    The west system pumps would work better than what I'm doing now, but the automated epoxy mixing system I'm building will measure any amount you want and mix it (with a timer), so the next batch of epoxy will be mixed and ready right when I finish the first batch. That's the theory, we'll see how it really works once I have all the components working, but so far test on the pumps and mixing turntable seem good.
     
    BlueBell likes this.
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