Folding up keel.

Discussion in 'Boat Design' started by BertKu, Jul 26, 2016.

  1. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    I am busy making this different type of keel.
    Here are my problems.
    1) Should I place a permanent keel on my boat, I have to modify my trailer, which I don’t like to do.
    2) If my experimental folding in keel is a success, I am then also able to sail in less deep water.
    3) With a gadget it will be retractable before loading on the trailer.

    This is what I am building for my boat. It is an experiment. I don’t think it is ever done in the world. I think the drawings are self explainable. However if you consider I should make a change or improvement. I am gladly open for comment
    Bert
     

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    Last edited: Jul 26, 2016
  2. upchurchmr
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    upchurchmr Senior Member

    What kind of a boat?
    A rectangular keel will have very poor drag.
    How does it come up?

    That is not much lead.
     
  3. rwatson
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    rwatson Senior Member

    "Should I place a permanent keel on my boat,"

    I dont know. If it hasnt got one, why put it on ??
     
  4. daiquiri
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    daiquiri Engineering and Design

    How do you actuate the keel extension? Looks like manual work, before launching the boat?
     
  5. BertKu
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    BertKu Senior Member

    The boat is a 16 feet cabin boat with 2 extension at the transom to hold the solar panels and frame work.
    Photo's attached. Bert
     

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  6. BertKu
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    BertKu Senior Member

    Hi Daiquiri, I was hoping that you would comment. I have great respect for your engineering abilities. As you can see from the photo's the transom extension is permanent. It adds 180 liter of buoyance. I needed it, due to the weight for my batteries, which is 100kg.
    The extensions for the keel is done by 35 kg force spring blades. You can see the stipple line in the drawing. The weight of the boat will compress it to 3 into 1. (and I planning to build a gadget to raise and lower the extensions from the steering wheel, see photo)
    Guys, see it my way. I am not interested in speed and doing 20 knots. If I do 1 knot more than the current and wind, I am happy. Thus my speed is only approx. 5 knots. It is the wrong hull, we all know that. But it has a seaworthy certificate. Which I, after the modifications are totally finished, have to renew. However to place a small jib and a mast on the boat, I need a small keel, otherwise the boat will start drifting. Also because I place a mast and jib (No mainsail) on the boat, my CG is changing and I need to bring it lower down. Thus with this metal folding keel, with a possibility to add some lead to the keel, I should accomplish that. The only thing I am worried about is, should I hit a rock, what damage would have been done, not to enable me to lift the keel up. Maybe your engineering thoughts are welcome.
    Bert
     

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    Last edited: Jul 31, 2016
  7. BertKu
    Joined: May 2009
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    BertKu Senior Member

    Hi RWATSON, nice to see you are still around. I need a keel otherwise the boat will start drifting. Bert
     
  8. BertKu
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    BertKu Senior Member

    It is just a possibility for me, to add some lead. In principle I don't need the lead, just the keel not to drift with a small jib only.
    Bert
     
  9. portacruise
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    portacruise Senior Member

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

    I'd agree, bilge keels would be a better solution. They can be arrange to not increase draft or at least not very much, will offer effective lateral area and will have no moving parts.

    [​IMG]
    [​IMG]
    [​IMG]

    This are good examples of twin bilge keels that aren't any deeper than the belly of the boat, but dramatically increase lateral area, while still retaining the shoal nature of the boat.

    Do you have a photo of the boat's bottom, so we can see where they might be best placed? If not, how about a make, model and year, so we can pull it up and have a look?
     
  11. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    BertKu, I agree with PAR and Portacruise. You are designing a mechanism which will sooner or later become a victim of corrosion and marine growth, if the boat is intended to stay in water for some periods of time. Besides that, telescopic systems are problematic when it comes to mechanical stability and resistance (both in operation and in case of collision with ground), and to watertightness.
    Technically it can be done, but it is IMO not a sound (nor cheap) solution. I would go for a fixed short ballasted keel, either a bilge type or a full-length one.
    Cheers
     
  12. BertKu
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    BertKu Senior Member

    Thank you Daiquiri, The cost is very little, I could make it for USA$ 46.00 I use stainless steel off cuts. But you are right my worry concerning a hit is the real problem. Porta, has also given me a nice solution
    http://www.submarineboat.com/images/sailboat/Hinged_Keel_2.JPG So did PAR. Well let see what I am going to do. First I complete my front jib and mast and then worry about drifting and keels. Thanks all of you. Bert
     
  13. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Bert, instead of the telescopic approach that -as daiquiri wrote- is asking for trouble, you could make a hinged keel. Two swivel points, firmly attached to the hull with large backing plates to distribute the forces in case the keel hits something.
    On the trailer, the keel lies flat; after launching gravity pulls it down and you lock it with two large pins from inside the boat. The locking pins slide in guiding tubes that reach above the waterline so your cabin stays dry.
     
  14. PAR
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    PAR Yacht Designer/Builder

    I've seen folding bilge keels that did this too CDK.
     

  15. BertKu
    Joined: May 2009
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    Location: South Africa Little Brak River

    BertKu Senior Member

    Hi PAR, here 3 photo's of the bottom. Maybe another crazy idea from me, but I have placed 2 tyres not in line, but narrower. If I hit a pothole and that has happened a number of times here around, at least I don't pick up a blown tyre. What do you think what I should do for what kind of keel. Bert
     

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