Sea Trials

Discussion in 'Boat Design' started by Deering, Oct 12, 2018.

  1. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    Hi All,

    A few years back I posted some discussions regarding my musings about converting a 40 foot long aluminum power catamaran I owned from a planing hull to a displacement hull. This was a personal pleasure craft used in Southeast Alaska. The goal was to make it more fuel efficient and more mechanically robust/reliable. It was suggested more than once, on this board and elsewhere, to abandon such foolish thoughts and just buy a boat built for that purpose. Wise counsel that I ignored. The boat I had was functionally ideal for my usage up here and I just liked it. Buying a new boat was beyond my means and there were no existing used boats on the market that met my intended usage needs.

    Well I went and did it. I developed the design, hauled the boat and made the conversion next to my house. I hired skilled trades where necessary but did a lot of the work myself. The starting boat was a MaxWeld catamaran, a well regarded builder of aluminum powercats in the Pacific Northwest (sadly defunct after the 2008 recession). The hull was extended from a waterline of about 33’ to 51’ to allow for a smooth hull shape transition and to increase displacement performance. Final displacement was 38,000 lbs - not a light multihull by any standard, but a rugged one that could handle the remote exploration and quasi-commercial fishing I use it for along with being a comfortable pleasure cruising boat.

    I wanted to report back I did initial sea trials last week. I could not be happier with the performance. It aligned with my calculated design values almost perfectly, a bit better actually. Top speed of over 18 knots with a reasonable cruise speed of 12-13 knots.

    Not a perfect boat by any means. Repurposing a hull in such a dramatic fashion results in a lot of trade-offs and compromises. A perfect hull would undoubtedly be better optimized for this purpose, but in the real world you work with what you’ve got.

    Not to turn this posting into a novel, but I wanted to thank the many contributors to this forum that generously provided advice and feedback. I wouldn’t have gone down this path without you. And I especially want to give a shoutout to one contributor, Ad Hoc, who gave me enormously valuable insights and guidance that served me well.

    So for all you dreamers out there, you can turn your boat dreams into reality, but keep in mind that it will take three times longer and cost twice as much as any estimate you come up with.

    If I can figure out how to post pictures here I’ll put a few up.

    Cheers.
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Glad to hear it worked out well for you. Do you have an pictures that show the changes made ? Might give others contemplating similar "surgery" some ideas. Now, I wonder if we can find the original thread where you were looking for input...….
     
  3. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Spoken like a true Pro. :)
    The harsh reality of real design, not armchair stuff......everything is a compromise. Jolly well done for persevering and persisting.

    Ooooohhh..yes please!!!!!!!!! :):):):)

    Glad to have been or service and extremely happy for you that it all turned out well. Happy motoring....
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

  5. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    Here are a few pics of the build process.
    3D23CB6B-C2BB-4AA4-BEBC-AEF5DD8C72CB.jpeg
     

    Attached Files:

  6. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    More pics
     

    Attached Files:

  7. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    And sea trials. Note that the framework contraption on the back is just for the temporary winter tent, which fast approaches up here.
     

    Attached Files:

  8. JosephT
    Joined: Jun 2009
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    Location: Roaring Forties

    JosephT Senior Member

    Now that is one serious hull extension. Good job. It will make a great multi-purpose work/fun boat.
     
  9. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    wow

    Impressive....looks great in the water at speed :cool:
     
  10. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Whilst this appears to be a success story, and congratulations on what you have accomplished, deering, in the original thread someone advised you to just sell and put the proceeds toward an existing boat that would suit you, how far astray was that opinion, do you think ?
     
  11. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    Thanks. Those bow extensions that you gave me a rough sketch of, performed better than I had hoped for.

    These trials were only for a day under ideal conditions so there obviously needs to be more exhaustive testing, but that will have to wait until the spring. No doubt more flaws will reveal themselves. Just knowing that the boat is meeting the basic goals of the project is an immense relief after 3 years of working this.
     
  12. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    I don’t think it was astray in the slightest.

    What I did was a foolhardy risk that managed to work out, at least so far. If this project had been an abject failure after putting so much energy and money into it, that would have been a disaster. But beyond the risk, there’s the opportunity cost. I burned three years of my life, at least weekends and evenings, on this project. That was three years of not doing other stuff that I might have enjoyed. If I had sold this boat I could have bought an existing boat that satisfied 80% of my objectives. It wouldn’t have been my ‘perfect’ boat, but 80% ain’t bad. And I would have those three years back. If someone told me that they were planning to do what I just did, I’d give them the exact same recommendation. Whoever gave me that advice was a wise person.

    On the other hand...the process of getting to this point has been an extraordinary experience. Teaching myself the fundamentals of naval architecture (damn, what a challenging field!), planning the project, managing the project and learning new skills has been deeply fulfilling.

    I would conservatively estimate that I had to make 10,000 decisions on this project; every single nut and bolt and weld and tiny piece and big piece...required me to think about it and make decisions about why I needed it, where it needed to be, what material it needed to be of, how it would be prepared and connected... and how all of that fit into the whole. It’s one thing to dream up grand projects, but it’s mastering the mundane details that leads to reality. I failed to fully appreciate that at the outset, but I sure do now. I was fortunate to have had craftsmen who helped educate me on that.

    In short, knowing what I know now, I don’t think that I would do it again. But despite that, the results have been pretty gratifying so far. Ask me the same question next year...

    I’ve been telling my wife that my next boat will be a lot easier after this one. She then tells me I can explain all that to my next wife... I think she’s sending me some sort of a message in there.
     
    fallguy and BlueBell like this.
  13. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    I appreciate your candour, as should others who are thinking about making big changes to an existing boat. It needs a lot of rigorous thinking, and gathering of advice and opinions of people who ought to know. Plus a realistic budget assessment. I just hope there aren't any hidden vices that emerge, but usually they show up straight away. What you will have, is something to be proud of having done meticulously.
     
  14. Deering
    Joined: Feb 2005
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    Location: Juneau, Alaska

    Deering Senior Member

    Absolutely. In retrospect, I probably spent as much time in researching, analyzing, and designing the project as I did on the actual construction. Running calculations multiple times with different variables, then taking a different approach to see if it led to the same result. Building and testing half-scale models. Constantly tracking weight and trim. Reading, reading, reading. Many spreadsheets...

    I found Dave Gerr’s books to be invaluable.
     

  15. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    It sounds as though you really have gone "back to school" in executing this project, I would say if it is meeting your speed and fuel burn expectations, you have done very well, I guess all you need is some rough water to test that side of it, but with it now being a bigger boat, might turn out a pleasant surprise, I hope so anyway.,
     
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