Senior design project help

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

  1. Chikokishi
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    Chikokishi Junior Member

    [​IMG]

    This is my first pass idea about what the profile of the boat might be like.
     
  2. hoytedow
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    hoytedow Wood Butcher

    One more idea. You could use 2 keels along the chines called bilge keels. They would only be half as deep but the same weight as one deep keel. They will support the boat level on the beach and can run in shallower water.

    Post #8 here at http://www.boatdesign.net/forums/sailboats/twin-keels-26401.html shows an example.
     
  3. Petros
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    Petros Senior Member

    I would loose every part of the keel between the rudder and the back of the main keel.

    It does nothing good for you. The rudder can be cantilevered on a rod or pipe, and it pivots in a larger pipe structurally mounted through the hull. It will make the rudder more efficient (more effective, less drag), and a single high aspect ratio keel will be also be more effective and have less drag. Make both the keel and rudder cross section foil shaped.

    But as others suggested, on a boat that small, please just put in a dagger board. It is much more effective and landing and launching will be simple, and it will make it easier to transport on roof top or trailer. Than just attache the rudder to the back of the transom. A dagger board is simple, very efficient (the fastest sailboats in the world use dagger board for a reason!), very modern, and much easier to build that what you show there.
     
  4. Chikokishi
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    Chikokishi Junior Member

    Loose the skeg type thing? That could be a good idea. The reason it is fully connected is that i inend on making the entire piece solid. and then it will go into the boat to the 6" mark and it will bexome the bottom support for the deck. As far as the daggerboard or the leeboards and such. I know that they are much simpler, i know that they would be easier to move and all such things. But i must point out that i am not necessarily going for what is the easiest. I am going for something that is solid, useful, and a bit elegant/ classic looking. and i just dont really like leeboards all that much. I want to build her like a ship, using a simple hull and novice to moderate construction. The idea of the modified keel and the lines that are drawn are not a product of ease, but one of tastes.

    I know im making the boat much more complicated as such, but i equally want to be proud of this boat for being unique as for being useful. And in my opinion a little cute boat with the bells and whistles of a large ship is much more interesting than one that looks like every other <15' boat.

    As for that matter and intend to include a full helm on this boat along with full rigging and a ship bell/ anchor/ etc. So when it comes sail time, dont be expecting a sprit sail or a lug sail. Im most likely going with a full gaff fitted with shrouds and everything.

    I understand that some of you might find this obnoxious and stop checking on this thread due to my stubbornness. But i appreciate the few of you who remain interested. I had many people tell me that i couldnt build the last boat that i have pictures earlier in this thread, with comments like "putting a helm on a boat that size is pointless, use a tiller" and "the cabin is just a waste of space, take it out" ... but i got it built anyway!


    As a side note, Do not think i am ignoring and disregarding ideas that conflict with mine. This boat is 3 months away from the start of the build, and all of your suggestions are going into the discussions about what we should do. Thanks for the help
     
  5. NoEyeDeer
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    NoEyeDeer Senior Member

    Ok, if you are basing this on a PDRacer hull may I suggest that you take a very close look at how the Australian ones are built? They are a lot lighter than the US ones, and have far less hull deflection under sailing loads, due to more efficient construction. They are still very cheap and easy to build, and are easier to manage because of the reduced weight. There's no point paying for and carrying materials you don't need.


    IF your tastes include making reasonable progress then you should take efficiency into account, at least to some degree.

    You don't need to use a leeboard to get shoal draft. You can use a daggerboard, or a swinging centreboard, in an offset case built into the sides of the cockpit. This wont lose you any space, and wont look uggers, and will mean you will actually be able to beach the thing and sail it upwind.

    Also, take a good look at the Ocean Explorer. This is a very well thought out cruising/cabin version of a PD.
     
  6. Chikokishi
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    Chikokishi Junior Member

    The ocean explorer is surely a great boat, i first saw it a while back. My boat is a bit over kill in the fact that were using it as a mechanical design project. And as the sailboat part of the sailboat is not exactly mechanical, we have to add mechanical to it. And my adviser finally accepted the project after we can made it as ridiculous as to even include a toilet and possibly a working sink. So this boat is much more complicated than a simple making of a boat with a bed that works well. It has to be converted between 4 modes, one of which uses a full open grill and food table, and another for comfortable pedal driven cruising around. one for an entire covering that is comfortable enough to move around in, and a final mode for pure sailing.

    The daggerboard and trunk ideas form problems when one considers that every inch of the interior is being used. it must be flat for the sleeping version, it must be open for the pedal version. it needs walking room for cooking, and then the keel is finally useful for the sailing design.

    Honestly i agree with the leeboard design. But i have decided to go with the keel idea because i would rather take on a harder challenge and get what i want instead of going with an easier idea to get a design im less happy with.

    The boat is intended to be trailer launched and anchored while sleeping. Remember, im going for a bigger boat style... its only small. And no one on this forum probably advises people to build a boat so that they can drive it to the beach for camping. Thats not to say that i have not seen the twin keel boats that can sit on land during low tide and such - iv seen them, iv thought about their design.

    Can someone explain what makes the australian pds better? Not too sure itll matter all too much as the *only* part of my boat thats a PDracer is the curve of the bottom. Every other part of it has to be adapted to my needs.

    Also, i have got a copy of the yacht design book that was suggested earlier on this thread. It is excellent, thanks for the refer.
     
  7. NoEyeDeer
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    NoEyeDeer Senior Member

    Look, think about this a bit more. You have dead straight, parallel side panels on this boat. This means you can easily put a board all the way out against the topisides if you like. If you really want to get techy, use two boards (one each side) with asymmetrical sections for a better lift/drag ratio. You haul the windward board up and leave the leeward one down. This will work very efficiently and will not hog any of your accommodation space.

    This is why I've been talking about offset cases for boards. You don't have to put it smack in the middle of the boat. They are usually in the middle for simplicity and convenience, but they work just as well if they aint in the middle.

    The Australian PD's are better than the average US one primarily because, as I said, they get stiffer and stronger construction with far less use of materials. This is good engineering, right? You are an engineer, yes? Your adviser will want to see good engineering.
     
  8. rwatson
    Joined: Aug 2007
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    rwatson Senior Member

    I see you to-ing and fro-ing on the leeboards, twin daggerboards approach, when you design requirements seem to favour the concept.

    Launching a fixed keel boat in shallow waters is tricky.

    A few illustrations of the concept for your interest.
     

    Attached Files:

  9. Petros
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    Petros Senior Member

    you said you are willing to go to extra work to "get what you want". A fixed keel will not perform as good as a twin dagger board configuration like the one pictured above, a fixed keel will be harder to build, weigh more, cost more, have more drag, be more difficult to land/launch and trailer. Is what you want a silly "cartoon" of a boat that has no advantages to other configurations? That is rather a poor choice, for anyone, let along an engineer. Dagger boards are now used on all of the modern fastest sailboats ever built, EVERY SINGLE RECORD BREAKING SAILBOAT USES DAGGER BOARDS. What you are proposing is obsolete by at least a century.

    If you want more systems, how about designing a modified junk rig that can be fully deployed and or stowed from the cockpit? How about remotely being able to raise and lower some foil shaped dagger boards? how about an autohelm that keeps the boat on coarse, there is even a thread on this forum with detials on home making an electronic autohelm, though personally I would go for the wind vane type for your boat.

    Those items will impress your instructor, not toilets. Those items will make operation your boat easier and more efficient.
     
  10. Chikokishi
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    Chikokishi Junior Member

    Cartoon boat is a perfect way to describe it probably. I love the shape of the modified keel.

    So what of this twin keel idea someone mentioned earlier? How would i make a twin design without it being a full keel on both side? While also making it able to be in while on land, and sturdy

    As i said, i am making a permanently attached rudder and propeller under the boat.. I dont want to run it aground. (also why i was going for the keel and trailer launch)
     
  11. Petros
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    Petros Senior Member

    than put a two fixed keels, trapezoid shaped, one along each edge of the hull, about 1 ft deep and 2 ft long, make it out of 3/4" plywood, or even solid lumber. attach to the inside of the side bulkhead of the hull so it will be real stout, round off leading edge, sharpen trailing edge, leave lower edge square. These should be located so the centroid of the keels is about even with the centroid of the sail plan. Than make a sturdy rudder on the centerline that can hold up rear of boat. It will form a tripod that will keep prop off the beach. You can even mount some wheels on the twin keels to use it to wheel it down to the water like a wheel barrel.
     
  12. Chikokishi
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    Chikokishi Junior Member

    Not a half bad idea, nor is it far from my idea of that nature. Itll go into the drawing board! yay
     
  13. brianb00
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    brianb00 Junior Member

    Ignore, comment already made.
    BB
     
  14. brianb00
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    brianb00 Junior Member

    Great looking design. How do the dagger boards clear the shroud attachment points ?

     

  15. rwatson
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    rwatson Senior Member

    Who knows - the NA worked it out.

    Its not my boat, just one of the designs I have been collecting.

    Chickokishi - one day you will figure out that a fixed keel is not what will suit this project, you need daggerboards or similar.

    For example, this design below will never launch easily or sail in shallow water.
     

    Attached Files:

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