Where to start when designing my first small sailboat?

Discussion in 'Boat Design' started by trackie2, Apr 1, 2021.

  1. trackie2
    Joined: Mar 2021
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    Location: Victoria BC Canada

    trackie2 Junior Member

    Sorry! Will do
     
  2. trackie2
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    trackie2 Junior Member

    I will definitely do that. I want to race my boat in the MicroTransat one day (The Microtransat Challenge https://www.microtransat.org/tracking/index.php) so a model would also be the perfect place to test my programming and electronics as well! Thank you for your reply :)
     
  3. Will Gilmore
    Joined: Aug 2017
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    Will Gilmore Senior Member

    upload_2021-4-7_22-48-14.png
    It sounds like an interesting engineering challenge.

    When you get to the point that you are working on designs, remember that as an autonomous sailing craft, it does not need to be designed to accommodate people or have crew friendly deck space. You don't need cat walks or flat decks. You also don't need to worry about comfort in a seaway. It doesn't matter it the vessel rides the waves softly, is a bit rolly or even pounds, all though a boat that small on the ocean isn't likely to pound no matter what the bottom looks like.

    My point is, there are shapes that are inherently stable, but for a manned sailboat, those shapes may not offer either comfort or safe workable space.

    Of the possible shapes to explore for stability look at the half-round cross section. The flat side naturally wants to roll downward and remain resistant to over-turning. The center of gravity is closest to the flat side and the widest section is in the water resisting heeling forces.
    upload_2021-4-7_23-1-50.png
    Add a keel to compensate for the sail and its supporting structures and you should have a boat that self-rights under any condition.

    There are a lot of good choices for rigs, my initial thought is to keep it as simple as possible. Having only the rudder as the one and only moving part may be a little too simple, but I also think it can be done. You will either set it to close hauled and avoid DDW and tack to most destinations or you set her for a broad reach to be able to get some down wind performance, but no windward sailing. Much more limiting.

    Good luck, this will be fun to watch, so keep us updated. Thanks
     
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  4. trackie2
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    trackie2 Junior Member

    Thanks for your reply John will defiantly start with the ratios and I've got a copy of "Principles of Yacht Design" on its way now! So glad this forum exists so much great info. I added a bit more info about what I'm planning below . I have to admit I'm getting quite excited for this project :)
     
  5. Dejay
    Joined: Mar 2018
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    Dejay Senior Newbie

    Does it still make sense to build a scale model for a 2.4m boat?

    Interesting project!
     
  6. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    I have thought about this competition.

    My methodology would be quite unconventional.

    The main goal is to make sure it makes it across.

    One worry I would have is it getting tangled up in floating garbage or kelp. This worry limits the keel and rudder design considerably.

    Another worry is about designing a sail that can withstand gale winds and brutal treatment from breaking waves. This sail has to be easy to control as well. I would prefer avoiding having to reef. Reefing will require another electric motor that can easily break down when it is needed most. I have even thought up a way to avoid having a sheeting winch.

    These are just a few thoughts to consider.

    Best of luck on your project.
     
  7. trackie2
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    trackie2 Junior Member

    I added a bit more info to this thread about my goals for this project that I defiantly should have added at the beginning!

    My boat will be a max of 2.4 meters for the microtransat.org (an autonomous transatlantic sailboat race). I think I want to try a bit of #1 and #2 I have some designs for other boats that I'm interested in primarily Open transat, Sailboy, and Saildrone (pictures in that order below) I don't know anything about boatbuilding but Opentransat used carbon composites to form the hull of his boat and I'd like to one day long in the future (if I can come up with the money) do the same. I did some reading about keel types and the modified full keel of Sailbouy seems to make sense for this application for directional stability? Am I correct on that or is there another keel type that would be better suited? Saildrone is a much larger boat than the other two and I have no idea how size affects the shape of a hull, but how streamlined and torpedo-like it interests me. Do you think a hull of this shape would be suitable for my application?

    Thank you for your reply and the book recommendations I'll definitely be reading those. I'm starting to realize just how big that mountain of knowledge I'm going to need before I get started is. Sounds like I'll be taking a drafting course soon too! ;)

    boat2.jpeg 00006578_web.jpeg 00saildrone-1-jumbo.jpg
     
  8. mc_rash
    Joined: Aug 2020
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    mc_rash Junior Member

    I totally agree with your statement Will.
    And also that the decklayout doesn't need to fulfil the wishes of an owner (including a sun deck for his wife).
    @Will Gilmore wouldn't it make sense to shape the deck with such a half circle? So that in case of capsizing the boat would get in an unstable situation due to the circle shape and the shape's behaviour?
     
  9. mc_rash
    Joined: Aug 2020
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    mc_rash Junior Member

    @trackie2 I watched a video of the orange "Saildrone" a while ago and it seems to be a good and long-lasting design for autonomous sailing.
    Longlasting should be a big aspect in your design since the boat will sail autonomously for a time with no opportunity to fix it if something breaks on his voyage (in my eyes the selfrighting stability is a subpart of longlasting).

    If you want to I can help you with the design, I'm naval architecture student in the Netherlands and I would appreciate to be part of your team (if you don't want to go the way allone :D ) and you will have somebody who can receive the boat so you don't need to travel from Canada to Europe! If you are interested in team work just send me a PM!
     
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  10. trackie2
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    trackie2 Junior Member

    Thanks for your reply I'll keep that in mind. No doubt I'll have many, many more questions when I start looking into hull shapes, but a half-round cross section seems like a good place to start. I'd like to try to limit the boat to one moving part. I'd almost like to have two sails one set close-hauled and one set broad. Would I be correct to assume this would affect its directional stability? On a related note I've started reading about keel shapes and looking at similar boats granted my understanding is limited it seems that a full keel would make sense. What are your thoughts on this and what factors should I consider when I get to choosing a keel?

    Thanks again :)
     
  11. Dejay
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    Dejay Senior Newbie

    My uneducated guess is that most of all the keel shouldn't catch kelp. I guess this is why they are so slanted backwards?
    And be deep and heavy enough to provide self righting.
     
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  12. Will Gilmore
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    Will Gilmore Senior Member

    don't set two sails on two different tacks. They will always interfere with each other and could cause capsize and steering difficulty.

    If you set you rig close hauled, you will get the greatest range of movement. Dead down wind will be $#!t, but you wouldn't sail DDW. You would sail a broad reach and tack down wind. If you manage to design and build a performance boat, then you will get a better VMG by sailing a broad reach. (VMG = velocity made good and it refers to DDW progress or directly into the wind progress).

    As your boat picks up speed, the apparent wind moves forward and it can do this until, even running on a broad reach in true wind, the sail's angle of attack becomes close reaching. The VMG can beat the @$$ off a spinnaker running DDW.

    Watch the AC boats or the maxi cats or the Hugo Boss boat, they are always sailing close hauled.

    If you are remotely controlling you boat, you will be watching an ap like "Windy" and tacking towards your down wind destinations as well as your upwind destinations.
     
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  13. trackie2
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    trackie2 Junior Member

    Makes sense to me :) sounds like boats getting tangled has killed quite a few attempts looking through the previous entries
     
  14. kerosene
    Joined: Jul 2006
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    kerosene Senior Member

    I am a wanna be boat designer with quite a few books - many of which I have also read. :)
    I have been this way for very long time so not a good role model as I have not gotten that much done.

    I think nature of Boats by Gerr is a really good 1st book. It is not very technical and covers all kinds of boats but it is very easy to read, ie. well written, general introduction to the concepts that influence a boat.
    Principles of Yacht design was mentioned before - that seems to be a primary recommendation to all people who want to understand boat design. It is probably all you need for designing the hull shape for your project.

    In addition as suggested make models. Get familiar with epoxy. RC boat forums have good info on this but also read composite wood boat building "bible" Gougeon Brothers on Boatbuilding. Luckily they offer it as a free PDF too. Here:
    https://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf

    That book gives you a decent understanding of the amateur friendly composite methods and working with fiberglass over wood.
    You can either use balsa strips as the core with epoxy/fiberglass over it like I am doing HERE 15 years ago. Or think 1-2mm plywood, or foam core panels (you can use foam core as strips too). I think panels are totally fine choice the skin friction difference from having chines (angular edges running along the length of the boat) are probably not a killer here. With foam core I mean pvc cores like aircell or corecell etc.
    Foam core boat building search will give you plenty of videos in youtube. As will strip boat building (common for both one off sailboats and especially wooden kayaks).

    Good luck.

    In terms of software... you can find freeship 3.43 online by googling. I have it too. It is bit clunky but still easy to use. That being said - software is like a typewriter or word editing software to an author - a tool that makes things easier but it doesn't do the intellectual work for you. That is why books are more important.
     
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  15. sharpii2
    Joined: May 2004
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    sharpii2 Senior Member

    For my money, I would go with the full keel and attached rudder. This is far from the most efficient underbody, but it would be far less likely to snag on something. And there are a lot of things to snag on in the today's ocean. I would want a bigger rake to the forward edge of the keel for this reason.

    I wouldn't play with carbon fiber, and I would keep the hull shape simple. I'd probably go with a single chine, and build the hull out of epoxy coated plywood. I would consider a double-ended hull, as it will likely have to deal with over taking breakers.

    The real key is designing a sail rig that can take being dumped end over end without breaking.
    This can be a real challenge.

    Make the hull as long as possible (the whole 2.4 m), and make the Water Line as long as the Hull.
     
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