Senior design project help

Discussion in 'Boat Design' started by Chikokishi, Sep 10, 2012.

  1. Chikokishi
    Joined: Mar 2010
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    Chikokishi Junior Member

    Im a mechanical engineer attempting to design a 3 season sailboat for overnight camping. My team wants to design a full keel for the boat because we intend on putting her in shallow water. I cant for the life of me find *any* information on how to design a full keel. I need to know what factors determine height, length, shape. Etc. Of course i can look at a boat and scale it down to mines size and assume itll work. But thats not so good for a design presentation. Any idea where i can learn about this?

  2. Red Dwarf
    Joined: Jun 2012
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    Red Dwarf Senior Member

    No offense but you should already be able to find information on your own. One thing I tell new engineer hires is they don't have to know everything but they sure as hell better know what to look for and where to find the answer.

    Try a thing called books, I know that is so 1970 but it works.
  3. messabout
    Joined: Jan 2006
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    messabout Senior Member

    Be a little more specific about the intended use, type of water where the boat will be used, size of the boat, expected displacement, number of passengers, etc.

    Depending on application, you may not need a ballasted keel at all. A centerboard or leeboards may be all that is needed.

    Other forum members are sure to join me by urging.... you to save yourself a lot of grief by buying a set of stock plans that have been produced by a recognized professional designer. The loss of satisfaction for having designed your own boat will be offset many times over by gaining the satisfaction of having a proven boat that also saved a lot of money in construction materials and time.
  4. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Is this a project for a senior design course or similar?

    Is the assignemnt to design "a 3 season sailboat for overnight camping" or does the team decide what they want to design?

    What is the team's level of knowledge about boats and boat design?

    What do you have for requirements for the boat? Does the team create them or were they given to you?

    "My team wants to design a full keel for the boat because we intend on putting her in shallow water." Was a centerboard considered?
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Keels and shallow water are mutually exclusive. A ballasted centerboard, leeboards or daggerboard would be better.
  6. Chikokishi
    Joined: Mar 2010
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    Chikokishi Junior Member

    Alright alright, i guess this needs a bit more background information before the lot of you kill me with criticism.

    In reply to being able to find information on my own.. Yes, i do know what books are and how to use them. My college is a mining intensive school and is very small. The library here contains about 4 books with reference to boats, and these are of the fluid dynamics course variety. Nothing is specific. Our local library is hardly better than a second rate highschool library to start with, not to mention lost most of its collection to water damage last year. They do not have computers for book searching.

    Moving on, We do not intend to build a large, curved and shaped boat. In fact it is going to be an 8'x4' PD racer hull design. Our project is focused around simple build, local access supply, and home do-it-yourself skill. Which, in the end makes the boat a bit more complicated anyway.

    As for what the boat will carry and such... It will have a heating and cooling system which is solar powered, peddle prop, internal rudder, keel, stove, food compartment, full cabin, lighting, and enough room for 2 people. We intend to put a hydro generator under the boat that will be used along with the solar power to recharge batteries for the system. The boat will have three modes basically. Camp mode, peddle cruise mode, and sail power.

    Back to my original question, I built a boat this last summer and my girlfriend (also a mech engineer) spent plenty of time attempting to find equations or methods to the design and shape of a keel. The best we could find online (given our limited local resources) was a simple ratio calculation of how much your keel needs to oppose laterally in order to match a sail. That worked fine for our last boat, but this one needs to be better quantified. So we are looking to find articles or anything that describe how people go about deciding what shape and how deep and where to put keels. We want a full keel or a modified full keel because we have shallow water around us and having a large daggerboard is too risky. So any leads to where i might find general information as that is what we are looking for, would be awesome. (this even includes telling us about good books that you know of so that we may look for them) Im not asking you to do my research for me, but i figured as this is a forum to help boat designers... someone who is boat designing might do well to start here and not reinvent the wheel so to speak.

    Thanks again

  7. Chikokishi
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    Chikokishi Junior Member

    This boat took my girlfriend and i (we are the design team) about 3 hours to design. The sails and rudder that we used took a couple hours to work out. And the boat took us about a month to finish.

    This is about our building level. This images do not show the curves and such i put into the boat, but if you look closely at the transom you can see that the top of the boat is not flat, and it curves more than that in the middle, and its flat across the nose.

    1 person likes this.
  8. Tad
    Joined: Mar 2002
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    Tad Boat Designer


    Find a copy of Principles of Yacht Design, by Larsson and Eliasson. Extensive discussion of the factors involved in keel design.
  9. FranklinRatliff

    FranklinRatliff Previous Member

  10. longcours62
    Joined: Jul 2011
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    longcours62 Junior Member

    I have one "principle of design" by Lars Larsson & Rolf E Eliasson interresting (even if for me it 's more complicated....wrotte in English !!:mad:)
    If you want have one idea of what I feel read , for example, :
    Architecture Navale by Presle & Paulet or Architecture du voilier par Gutelle French;)
  11. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Also consider a leeboard (or leeboard if you want to be symmetric). A pivoting leeboard can kickup if it hits something, does not take up space in the cockpit unlike a centerboard, will weight substantially less than a keel, and can be designed for better performance than will be possible with a shallow keel. A trade-off study between a conventional on-center daggerboard, single off-center daggerboard, twin off-center daggerboards, centerboard, single leeboard, twin leeboards, single shallow keel and twin shallow keels would be worthwhile as part of your design report as well as good experience for you.

    Principles of Yacht Design by Larsson and Eliasson is probably the best single reference book for you. While it is oriented towards larger cruiser/racer type sailboats the basic principles still apply. It's somewhat technical but I'd expect a senior in mechanical engineering to be able to understand it, or at least be able to ask intelligent questions about the parts they don't understand.

    Fred Shell has designed several small boats with shallow keels including one with a small cabin.
    The design of those keels may be oriented towards ease of building rather than performance.

    My guess is for a very low aspect ratio keel such as Fred Shell uses the details of the planview "airfoil section" are not as significant for the hydrodynamics as the shape of the leading and trailing edges and bottom edges. But that is only my guess.
  12. philSweet
    Joined: May 2008
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    philSweet Senior Member

    In your case, a survey of boats with a similar purpose, of a similar size, is precisely what you want for a presentation. 99% of small craft are designed from tables of average proportions and a bit of opinion about how one factor, if chosen to be a bit out there, should be accommodated with the other factors. Designing an efficient full length keel based on hydrodynamic principals would cause professional designers fits.

    My suggestion is to identify a statement of requirements (SOR). These are the must haves. Then identify any restrictions, such as a box rule (max length, beam, height), draft, weight. Then figure out what the top three or four design decisions will be in light of the above and try to get them right. The keel details are not likely to be one of these.
    you will probably be well within the "more keel would be better, but this is the most we can manage" range. Sailing less than perfectly beats the heck out of wading through mud to get to the dock.

    A presentation which shows you have looked into the process used by experienced designers would be quite impressive to us (but possibly lost on the faculty of a mining school). Maybe you should model your boat after Prospector. It was (and still is?) a remarkable boat with a storied life.
  13. Chikokishi
    Joined: Mar 2010
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    Chikokishi Junior Member

    Iv looked into the book you all mentioned, a few excerpts from it looked very nice indeed. As for the outrigger idea, there is not much room for the components i intend to put into the boat on that guy, otherwise it would be an good suggestion. Ill look into finding these ratio tables that was mentioned. Are they something along the lines of a boat with such and such dimensions' keel should be about such and such big?

    Thanks for the useful comments!

  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Why do you think you need a keel? The PDR has nearly enough lateral area to prevent leeway just with it's immersed flanks. The dagger or leeboards and the rudder provide the rest. Simply put, it's pretty easy to figure the area of the underwater portion of the dagger, so a fixed appendage would have a similar amount for similar performance. Selecting foil shapes can be easy enough to figure out, considering the known performance envelope. Of course a fixed appendage will limit shallow water ability, which is the whole point behind the retractable appendages employed on the PDR and other small, shoal draft craft.

  15. Chikokishi
    Joined: Mar 2010
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    Chikokishi Junior Member

    The boat that i showed above has a centre daggerboard. It works fairly well id say. The reason we want to go with a keel is because we want everything to remain attached to the boat. We want to do a keel more for we think its pretty reasons than because we think its the best option available. Im not a huge fan of leeboards or the like because iv build two boats that had them and even though they worked perfectly fine, i did not like the sight of them on the side of the boat.

    On a side note, we are also considering putting fins on the sides of the boat like this one:

    That way we could design a nice looking profile (although i know this is pointless as its underwater, this boat spends most of its time out of the water) and also when we take her out of water shell be balanced on the fins. Im just a little worried about putting the weight of the boat on fins like that.

    Even though i dont like leeboards i am slightly inclined to use one so that if we want to camp on shore or the like then we can just drag it aground and do such. plenty things to think about
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