Keel Design on my 57' Buehler design

Discussion in 'Motorsailers' started by IONA, Mar 31, 2009.

  1. IONA
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    IONA Junior Member

    IONA IONA is online now

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    Keel design at prop
    She's a 57' George Beuhler designed cruiser and I am nearing the end of building the keel. My engine is a DD4-71 and I have a 2" shaft to a 28-20 3-bladed RH prop. The keel is 11" thick. My question is what is the best way of carving that big thick keel in the area around the cutless bearing housing so as to maximize flow over the prop and minimize the kick of the prop as well. I assume I will want to carve what, viewed from the stern, would look like an "S" shape, with the shaft coming out in the middle of the "S" but my question is, which way will the prop kick the boat? And which way should the "S" face? Should it look like a standard "S" viewing her from the stern, or a reversed "S", and why? If this is not a clear question please view my little attached drawing.


    View my progress at this album page:
    http://picasaweb.google.com/GreyFox1931/GregSBoatyard#
     

    Attached Files:

  2. PAR
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    PAR Yacht Designer/Builder

    Duplicate post. Check the wooden boat section for a reply.
     
  3. peter radclyffe
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    peter radclyffe Senior Member

    Its usual to combine the two, like most things in life the back face of the sternpost should have minimal drag, the lowest part of a prop gives more thrust than the higher part, as it is in denser water, what a terrific project, its very impressive
     
  4. GAZZABO
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    GAZZABO Junior Member

    Greg- Well have you got yourself a project! I would chamfer both sides top and bottom of the deadwood to minimise the drag and smooth the prop (le3ss deadwater to go thru) good luck and keep posting your fotos
     
  5. dskira

    dskira Previous Member

    Nice job. You are almost there
    Cheers
    Daniel
    [​IMG]
     
  6. GAZZABO
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    GAZZABO Junior Member

    Looks good. I will be doing the same next year when I start my liveaboard Troller see FOOTHOLD photo now posted .
     
  7. IONA
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    IONA Junior Member

    The stern timber went on last week. (The last of the 2x12 laminations. Hooray!) The next thing I did was level her off. (Only needed to lower the stern by about 1.5 inches to reach level.) Now I am laying out the lines for the frames and floors so I can start drilling the holes for the thru bolts. I am thinking of using .75" rod in 1.25" holes. After I drill the holes I will soak a rag with ethylene glycol and saturate all the holes with that. After it dries I will weld the rod bottoms onto the steel plate that will run along the bottom rather than thread them and bolt them, then coat the inside of the plate with roofing tar. Then I will push the plate up to the keel from underneath, bring the rods up with it, and then pour a slow-kick epoxy down the holes to permanently secure the rods. After I make the floors up I will thread the rods as needed on the top. Should be waterproof and solid as a rock. Also I don't want any trouble between the wood and the steel, and I like this way of attaching the steel plate without screws. I just don’t like the idea of wood screws into the keel on the bottom. Once all those buggers are made I can set up my framing table and begin the process of building frames. That will be the time when I start working on the engine bed and the shaft. I figure it’s another four years minimum. But I finally figured out that building this boat is an end in and of itself.
     
  8. PAR
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    PAR Yacht Designer/Builder

    In other words, if you take damage, you can't easily remove the metal shoe? That about as counter productive as it gets, especially for a Buehler build.

    Lets face it, this boat's going to be big enough to bash stuff real good. That keel shoe is going to dent, get deformed and other wise smashed around pretty good. If you marry it to your keel like that, you have hell to pay when it comes time to address the shoe.

    The keel shoe should always be considered sacrificial in nature. It should be bedded and fairly lightly attached, unless you plan frequent hard landings.
     
  9. IONA
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    IONA Junior Member

    PAR
    The reason I read this site is because I don't know everything. Here is a great example of that. Why didn't I think of that? Maybe because I haven't ever done this before. You are right. I am wrong. Back to my drawing board. I was looking for a way to keep from having to bed the ends of the rods in epoxy the way George describes it. More thinking will now take place in my think box.

    Thanks PAR for excellent mentoring.
    - Greg Nelson
     
  10. Hägar

    Hägar Previous Member

    Thats what I love here, you may be wrong but you do not end up wrong!

    Hägar
     
  11. GAZZABO
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    GAZZABO Junior Member

    Iona-- Why are you building the right way up? Im going to do it the traditional Kiwi way and byuild upside down and then then clean off the keel to 200 wide and then laminate the outer keel and deadwood on. All my frames are bulkheads which are shaped to include all bunk seats and backs, bench divisions etc , so when we turn over (1 hour $100) all I have to do is all the accommodation longitudinals in.Fitting bulkheads after sheathing is really time consuming, My way I get all the bevels correct when lining off and installing the stringers.
     
  12. dskira

    dskira Previous Member

    You are right in a certain conditions. I built a lot of boat as you describe, but after a while, I went back to right side up. I find easier to control the shape, mostly the sheer, I find rewarding to put the keel first, and built from the keel up, I find the accommdation not so difficult after all. It is true that I put a ceiling.
    But this is my opinion, and I respect yours who also make sense.
    Cheers
    Daniel
     
  13. PAR
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    PAR Yacht Designer/Builder

    I prefer to mold hulls upside down, but there comes point when you have to roll the beast over. This isn't much of an issue on small craft, but massively built 57'ers should be considered a candidate to build upright.

    Back to the keel shoe. Instead of tar, have the shoe coated with spray on truck bed liner. Make sure you drill the fasteners holes over size, because the truck bed liner will fill them. Then bed your shoe in the goo of choice, which I'd recommend being 3M 101 as opposed to tar. 3M 101 is much more flexible, will stick very well to both the polyurethane in the truck bed liner and the keel and it will not attack anything like petroleum based tar products can, plus it can be removed without damage. Besides, you don't want an oil slick floating around your boat all the time, which tar will produce. Tar is effective, but only if this is the only thing you have available. There are much better materials, that don't harm the environment as much as tar.
     
  14. IONA
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    IONA Junior Member

    PAR! Thanks again. I have been trying to figure out thew best way to do this ever since i got near finishing the keel.
    What fasteners do you reccomend? Galv. long wood screws?
     

  15. PAR
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    PAR Yacht Designer/Builder

    Galvanized will work, though bronze be my first choice. Make sure you get hot dipped, not the "electro-galvanized" they're trying to sell currently. Real hot dipped will last a while, the electro-crap will not. Shop around for fasteners as it's getting hard to find good ones. Seeing as George's designs rely so heavily on fasteners, you'd be best advised to get the best you can afford.

    On your boat, epoxy will be used as a glue only. Don't coat the parts, you're just tossing money and time in the bilge.
     
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