converting a 20' dawncraft to a small replica pirate ship

Discussion in 'Boat Design' started by andyh, May 24, 2012.

  1. andyh
    Joined: May 2012
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    Location: isle of man

    andyh Junior Member

    Hi im was thinking about buying a 20' dawncraft boat and converting it in to a small replica pirate ship however im by know means a boating expert and i was wondering whether i would encounter problems with stablity. please see attach Cad Plans :)
     

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  2. J Feenstra
    Joined: Jan 2012
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    J Feenstra Junior Member

    First things first, where is the Parrot?

    secondly, Perhaps you could ad an centre board or a keel to compensate for the aft castle youre planning to build. Not sure if it will help, but that would be a start....
     
  3. andyh
    Joined: May 2012
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    andyh Junior Member

    well i couldnt decide if i wanted a blue and yellow or a red blue and yellow parrot :)
    so i think he will come at a later date and i had thought about that but like you said would know if it would help either.
     
  4. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    Pretty sure the parrot you want is a Norwegian Blue.....great pet

    And yes you will have stability problems.........
     
  5. andyh
    Joined: May 2012
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    andyh Junior Member

    well is there a way of using a ballast, keel or something to correct the stability or is it a complete no go?
     
  6. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    Added weight of topsides + added weight of ballast + added windage = unseaworthy...

    Could you use canvas, dark screening and bimini style tubing to create the pirate look? The weight penalty would minimal and when the wind pipes up you could take the canvas down and regain control of the boat.
     
  7. Petros
    Joined: Oct 2007
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    Petros Senior Member

    I like your plan, it will work out okay I think if you keep these issues in mind:

    strip as much of the old weight out as possible (that is without affecting the strength of the old hull), and keep what you add as light as possible. You will have to add ballast in the bottom of the boat, or better yet, add a cheap concrete keel (about 8" x 8" full length should do it, use rebar in to keep it together). Add a large "barn door" rudder, it will add to the pirate ship look anyway, and you will need it.

    Try to keep the windage of the above deck additions as little as possible, use open railings, etc. Keep deck houses, etc. low.

    As noted, it likely would not be good for open seas or rough conditions, but for floating around on lakes and other calm inland waters, it should work fine. Should work good as a parade float as well.

    Have lots of fun, post pictures of your build and when you are done. I like it.
     
  8. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I agree with Petros, go for it, but don't ask too much of her as she's still just a little 20' runabout hull. Installing "garnish" will not make her anything more then what she is.

    It appears you're looking to put in a lot more accommodations than are practical on a 20' pirate ship. You'll be lucky to have enough room for seating for 6, porta-pottie, maybe some camp cooking facilities. That's about it and it'll be crowded with all that structure around you.

    Instead of building up, consider keeping things low and lean. The fore and aft castles can be stylish and not double the height of the boat (which has to pass under bridges when trailering). In short, I see a boat that has a lot of "hamper" which just decreases stability, all for an aesthetic consideration. Keep the decks and the stylized additions low in the boat or launch day could be embarrassing.
     
  9. andyh
    Joined: May 2012
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    andyh Junior Member

    Thanks guys your words of advice have probably saved me a lot of time and embarrassment and have given me a lot of good ideas for restricting the weight.

    However Par i really should of but some dimensions on the Pdf so I have done that now but im not planning on towering it up much more that it would originally be. And by doing these modifications im turning a four berth in to a two berth and reinstating the rest of the facilities in different locations. All in all making the boat more spacious and the whole custom top would be made from light weight timber and marine ply and as for the sails they are purely for aesthetic purposes and would not be functional as im looking at fitting either a 25-50hp outboard or similar sized inboard engine. Also as for bridges I live right next to the local harbour and I not intention of taking the boat back out of the water once its in as it’s a small island and could sail around it.

    So Par could you please take another look at the reattached drawing and see what you think and whether it would be worth attempting this project as im not a boating expert in fact far from it lol so if it’s worth taking advise from any one a yacht design is probably my best bet.

    Cheers Andy
     

    Attached Files:

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

    The dimensions and drawings frankly aren't representative enough of the donor hull, to take especially seriously Andy. I'm not intending to insult you, but other then some out of proportion, concept sketches, they're not especially helpful.

    What I see it a multi decked structure, that place crew well above the CG, coupled with additional structures also well above the CG. I can easily see this new structure doubling the weight of the hull (plywood isn't light).

    Look, generally the way we approach this is with an arrangements layout, of where the basic stuff might live, then a weight study, to see if these locations need to be altered, to get the boat to balance and float where we want it to. Without this, you haven't the foggiest idea if it will even be able to support this additional structure, on the displaced volume you have to work with (the donor hull).

    This sort of thing has been done many times, but you've drawn up accommodations to a 26 - 30' boat and are attempting to place them in a 20' hull, by building up and out.

    The first thing you need to do is get an accurate representation of the donor hull, so you can calculate the important stuff, like immersed volume, PPI, MT1, CG, CB, etc. With these in hand you can establish your limits, so you can design a structure around them. Simply put, if your PPI is say 600 pounds and you add a ton of new structure and crew and supplies (pretty easy to do), the hull will sink down about 3 1/3", which could be acceptable, depending on other factors. If you don't have the parameters and limits figured out, it's just a crap shoot and it can capsize, not float, drown people, etc.
     
  11. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    all I can say is they sure want a bundle for hulks on your side of the pond.

    Over here in California they paid $100-$500 to haul wrecks like that away to landfill.
     
  12. Petros
    Joined: Oct 2007
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    Petros Senior Member

    does a wood boat in that condition have any value?

    Keep the height of the new cabin to the same as the old one you will likely be fine, just be careful if your crew takes to hanging from the mast or yard arm. Puts too much weight too high.
     

  13. HakimKlunker
    Joined: Aug 2009
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    HakimKlunker Andreas der Juengere

    My opinion: Forget it. The original is a motorboat. Once you add sort of rigging - even if it is fake, and together with high windage, you may have something that looks fancy as long as it is moored.
    Once you cast off the mooring lines, you will be in danger, and all other TRAFFIC PARTICIPANTS as well.
    As a joke, even on the dry only, it's maybe fun, but a waste of time and money in case you think that you have an operational vessel in the end.
     
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