Can anyone give me some pointers/opinons on designing a 8m motorboat?

Discussion in 'Boat Design' started by newkid1, Dec 7, 2009.

  1. newkid1
    Joined: Dec 2009
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    Location: UK

    newkid1 New Member

    Hi -
    I've just been sketching out a possible boat design for a project over the winter, and as this will be my first boat (other than something closely resembling a cupboard I built when I was 8), if anyone has any pointers or any advice that would help - I would really apreciate it!

    I've also had a bit of bother trying to figure out the hull-shape, if anyone knows of a general formula/guide that would be helpful, please leave a message!


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  2. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Hi newkid, welcome aboard the forum :)

    Some comments on what you've posted:
    A boat this size is going to take more than a winter to build. Working full time on the boat, one skilled builder might get something like it put together in six months, but as an amateur part-time build I would figure on a couple of years, and quite a few rounds of BOAT (Break Out Another Thousand).

    From the sketch you posted, it's apparent that you're trying and you have some ideas, but don't quite understand how a planing hull works. (The most obvious giveaways: your chine curves upward as it approaches the transom, and your deadrise is close to constant all the way to the stem.)

    That's OK. We all have to start somewhere. I'd suggest you find at least one good yacht design textbook (Larsson/Eliasson "Principles of Yacht Design" is a good start), read the chapters on lines drawing and high-speed hulls, then go hang out around the local boatyard. Look at the underbodies of various boats, and see if you can match characteristics described in the book to features you see on the hulls. Chat with the boat owners, if they're around. You'll quickly learn how to identify shapes that work well, and shapes that are uncomfortable or inefficient. Keep as many books as you can find handy, each author has different expertise and different perspectives.

    Also take a look at boats as they are coming in to dock. You'll notice that curvy foredecks make for bad footing and injured line handlers. If you have a Coast Guard, police or fire boat nearby, take a good look at it- how the decks are shaped, where you can stand, where you can hold on.

    Perhaps most importantly, you need to sit down with your family / friends / etc. and make a list of what you want to do with this boat. Are you planning long trips? Weekend cruises? Inshore passages, or quiet river cruising? How fast do you really need to go? How much can you spend to build it? How much per year to feed and maintain it?

    All the best,
  3. newkid1
    Joined: Dec 2009
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    Location: UK

    newkid1 New Member

    Hi Matt - cheers so much for the reply! I'll be heading out tomorow afternoon to see if I can find the Principles of Yacht Design book, so hopefully I'll be stuck into that for a couple of weeks....
    I did also find it difficult to nail-down how long an entire build would take, but if a few winters is much more realistic - the girlfreind may take a little more convincing!
    If I could also ask - is there anywhere where I could just buy a pre-formed or a standard hull?
    cheers again,
  4. hwsiii
    Joined: Nov 2008
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    Location: Pascagoula, MS

    hwsiii Junior Member

    Newkid1, if you will look at Bateau I am sure you can find something that will fit your desire for a home built boat. Jacques, has many proven designs and you will have a tremendous amount of people on the forum willing to help you with the problems you will have as you progress on your building.
    He advises using epoxy with BS1088 plywood and biaxial material for the construction supplies for a true composite boat, and that is what is required if you want the boat to last.
    The key for most first time boat builders is lack of knowledge in materials and construction details, and you will not find a more knowledgeable group of people so willing to help each other any where else in my opinion. And you can't imagine how much difference that will make as you progress in the build and how it will save you from making major mistakes and help you be able to actually finish your boat.
    His designs are to be built with the composite stitch and glue method, which makes for a very reliable monocoque structure that will last for manyyy years if you build it right and maintain it .

    There is NO boat building forum on the internet that can compete with the number of people, knowledge, experience and willingness of its members to help each other through the building process of a boat. And I will guarantee you there is NOTHING MORE Important than that for the first time builder.

    Here is a link to their site:

  5. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Yes, yes, yes! These days, there are a lot of used boats in need of refitting, or partially built boat projects abandoned due to lack of cash/interest. They're not advertised in the glossy magazines, but you see them lying in the back corners of boatyards, a faded "For Sale" sign on the bow. If you can find something of the right size and type for your needs, and it's structurally sound, refitting a used boat is probably a cheaper, quicker, but just as satisfying option as building new (and the resale value will often be better).

    It's still a good idea to read up on design and systems, so that you know what you're looking for- I'll add Nigel Calder's "Boatowners Mechanical & Electrical Manual" to your must-read list- but if what you want has been done before, you can often be out on the water sooner and for less money with some judicious used-hull hunting.

  6. Bal 66
    Joined: Feb 2010
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    Location: Australia

    Bal 66 Junior Member

    Hi newkid. I was where you are now 2yrs ago and i am still going. My boat is steel frame and hull and is from an existing set of plans I purchased. These were non lofted plans, so i had to loft my table of offsets onto a base board then i cut and bent each frame, mounted them on a stiff back. 2 years on and i have finished the hull plating and have just flipped it right way up. Another way is to buy plans that come complete with all the templates you need. You lay these on your material, trace and cut. I guess first thing to decide is how much of a DIY role you want to play. I will say this tho, It gives you great satisfaction when you build it yourself. Good luck.
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