Folding up keel.

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

  1. daiquiri
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    daiquiri Engineering and Design

  2. BertKu
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    BertKu Senior Member

    Well, that is certainly a pleasant surprise. It saves me from making a keel. I will just only make the mast and sail working. I am still slightly concerned about the CG which will be moved up. Only when I have finished and sail a little, I will be able to judge whether it is a real issue or not a problem at all. Thanks Petros, Par and Daiquiri for your comments and help. (and saving lots of time)
    Bert
     
  3. PAR
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    PAR Yacht Designer/Builder

    Chine runners are somewhat effective and only on certain hull types, of which this isn't one of. Chine runners aren't as effective as traditional appendages, including bilge keels.
     
  4. BertKu
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    BertKu Senior Member

    Thanks PAR, I trust your judgement. Back to the drawing board.
    Bert
     
  5. daiquiri
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    daiquiri Engineering and Design

    Just to make it clear:
    I am not suggesting you to go for chine runners, also because I don't see how could you on a round-bilge hull. My previous comment was a generic consideration about how they work, and once you understand how they work, you realize that they are not applicable to your hull.

    My concrete suggestion for your boat remains the previously discussed one - bilge keels. Simple, cheap and effective.
    If you are worried about potential damage to them in case of hitting the bottom, it is possible to design a hard-rubber replaceable protection along the exposed edge of bilge keels.

    Cheers
     
  6. PAR
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    PAR Yacht Designer/Builder

    Agreed about chine runners and also about bilges keels. The most likely impact locations will be the leading edge which can be fairly short and of course the bottom. Both can be hardened up with several techniques. I don't like rubber, but HPDE or a half oval are pretty common approaches. The rope in a groove trick, also works very well and is employed on centerboard and rudder leading edges, for the same reason.
     
  7. daiquiri
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    daiquiri Engineering and Design

    Rubber might not be well-seen in small boat design, but in the commercial shipbuilding and offshore business it is widely used as a very effective and easily disposable protection for sensible structures.
    Considering the size and mass of that boat, a 40-50 mm thick Shore 80D rubber bar would IMO spread any impact point load over a much bigger keel length, effectively minimizing a possibility of any significant damage to the keel or hull.
     
  8. BertKu
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    BertKu Senior Member

    My sincere apology to you PAR, CDK, Portcruise, Daiquiri, I know that your solution of a bilge keel would be the better solution. However, I have to stick in what I can make, mount myself and take off afterwards and fill the screw holes up with fibreglass . Daiquiri, in your first reply, wherein you stated, “ Technically it can be done, but it is IMO not a sound (nor cheap) solution”. I have been able to solve all the negative reasons. You gave me the confidence that, although not the best solution, it could be done. I think I have solved all the arguments which made it not a proposition. I am busy making now my latest design and as soon I am finished, I will post it on the net. If it is a disaster, I will openly admit it. If it is a success, I will slap myself on my shoulder. Thanks guys for all the trouble . Bert
     
  9. BertKu
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    BertKu Senior Member

    Well, after somebody told me that the keel must be at least partly under the mast, I had to go back to the drawing board.
    Please bear with me, one of the biggest problem I had in making my boat is that there is no helper who can assist me, I have to make all errors on my own and try to find solutions for it. While crawling inside in the cabin, there is nobody holding a spanner on the outside, while I could tighten the bolts and nuts on the inside. I have to be very innovative. Nobody to hold a large part, while drilling on my 30 year old table drill or warn out table saw. But I am very pleased with the result.
    Photo 1 shows you the roll up sail rod I made with the mast. The cabin tubing bracket to support the mast from both side edges of the boat. Etc. I still have to anodize some aluminium parts, but struggle to find the correct current to do a decent job. Special, in how to do the 4+ meter mast. I was considering a 5 meter gutter and place the mast therein, but my power supply current is limited.
    However, I have a question on which I cannot find a solution on.
    My gut feeling tells me that I maybe should design stringers to support the mast better, instead of the steel wires straight to the side of the hull and not via a stringer. The length of the mast is 4.6 meter above the cabin roof. The 2 x 3 mm SS steel wire I will have to mount more to the transom. Due to the fact that I have the folding up solar panels at the back and cannot have a wire from mast to the transom.
    From the drawing and photo’s one can see the idea I have for the keel.
    I have between the centre rollers, for guiding the keelson on the trailer, 50 cm to the next wooden guide to hold the boat on the trailer. The idea I have, is to make a keel which fits nicely between that guide and the centre of the boat and trailer.
    The top round tubing is for stability, while the bottom large round tubing, I could fill this with lead to improve and lower my CG as soon I have replaced my 84 kg Lead acid batteries for more Lithium batteries. In the front of the folding up keel, I will have a coil spring. Should I be so unfortunate to hit something, it will slow down the impact. The keel itself is from 3 mm stainless steel.
    Well should I use stringers? How far from the top 2/3? Bert
     

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  10. CDK
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    CDK retired engineer

    I am familiar with the situation where you need someone to help you but there's nobody around. Superglue is my companion to keep nuts or bolt in place while I tighten them from the other side.

    As for anodizing long items like a mast, the biggest problem is how to seal it. You need to boil the piece for at least 15 minutes.....
     
  11. BertKu
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    BertKu Senior Member

    Thanks for the tip. I used a massive heavy piece of steel and a spanner with a earth magnet between the spanner and the steel. Those magnets are magnificent.

    What do you mean with boil the piece for 15 minutes? I am following an article in Practical Boat Owners from March 2012 page 66. Do you mean the current has to be so high that it real has to boil? Bert
     
  12. CDK
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    CDK retired engineer

    Anodizing with DC current in an acid bath is the easy part. You can even wrap wet bandages and aluminum foil around the tube. When the current drops, there is a porous oxide layer on the surface of the tube. That should be sealed in hot water for about 15 minutes to obtain a durable, weatherproof surface. At least that's the way we did it 30 years ago.
     
  13. BertKu
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    BertKu Senior Member

    Thank you CDK, that is valuable information. That article did not mentioning anything like that and what is 30 years ago applicable will also be today. Thanks. Now, I hope somebody who can advice me on the stringers. Bert
     
  14. BertKu
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    BertKu Senior Member

    CDK, any idea what current I need for the 4+ meter mast? I have 12 Volt and are making a bridge which can handle 100 Ampere maximum. I have a 68.000 uF capacitor. Bert
     

  15. CDK
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    CDK retired engineer

    The usual current for slow anodizing is 150 mA/dm2. That doesn't sound much, but a mast has quite a surface, especially when you want to anodize the inside also.
    We made instrument panels from bare aluminum, silk screened text and striping with some kind of wax, then anodized the panels in oxalic acid, removed the wax, brushed a dye over the surface and put the panels in almost boiling water for 15 minutes.
    Quite a tedious job, later we used light sensitive, adhesive aluminum sheets from 3M. Not as durable, but the process was much faster.
     
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