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Thread: A blatant Plug

  1. #1
    Join Date
    Oct 2007
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    Default A blatant Plug

    Angus, as well as being a gentleman, scholar and a fine judge of horseflesh, is a prolific designer of boats, as we know.

    In my spare time I attempt, in my modest fashion, to turn some of them into reality.

    We have just started construction of the plug for a design called Bakers Dozen - for which Angus has swooped the rear deck (for me).

    I thought it might perhaps be interesting to describe and show some of the steps in producing a plug for the hull - in Balsa wood. The plug can then be used for either:
    Moulding hulls directly (fibreglass or papie mache)
    Bottle-shrinking onto the plug
    Vacuum forming hull and deck as seperate parts
    Moulding a female mould from the plug - so that hulls can be moulded in the female mould with a good outside finish.

    Your suggestions and contributions - including STOP welcomed.

    BTW this identical process works with:
    your own design of hull
    Extruded Foam polystyrene
    Flavio's Presto - only once you have carved the plug you sail it!

    No photos yet - they are still in the camera
    This is what we begin with:


    I have altered the profile view to show the Buttock lines (vertical slices) at exactly 6mm spacing, since I am cutting the parts from 6mm Balsa sheet.

    Good News (and congratulations, Angus) - I can get all the parts from three sheets of 6mm x 100 mm balsa

    andrew

  2. #2

    Default Re: A blatant Plug

    Interested to know what sort of computer proram you are using

    Cheers

    Charles

    PS I know nothingof making up vacuum moulds. Can we have a little thread on the subject?

  3. #3
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    Default Re: A blatant Plug

    I generally like Angus' designs *although both he and I know that the other might do things differently* but A, what is up with this thing's sheerline? And why is the keelson so pronounced? I am the first to go for function before form, but what is the goal for this boat?


    *laughs* That being said, I am eager to see how it turns out, I assume due to its name that this is a 13incher?
    the pessimist complains about the wind, the optimist expects it to change, the realist trims the sails.

    Footys:
    USA 39 Bearfoot
    USA 62 Stiletto
    USA 190 Eclipse
    USA 97 Orange Crush
    USA ??? Albatross (in progress!)

    Sparkman Micro Marine
    builders of Footy hulls

  4. #4
    Join Date
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    Default Re: A blatant Plug

    Looks interesting Angus... and thanks for offering up the thread Andrew. Should be erm fun getting it out of the mold, unless it's a split design maybe?

    Quote 'Your suggestions and contributions - including STOP welcomed'
    No no no Andrew definitely don't 'pull the plug', sorry couldn't resist.

    Graham
    www.scalesailing.com
    Home of the 'Foamy Footy' since 2006
    www.oddguyart.com
    My shirt brand, look good while you sail.


    Kittiwake (#1) USA (retired);Pintail USA64;Siren USA65;Harpy USA158;Pond Sprite (#1) USA310;Kittiwake K2 (#1) USA410;Pond Sprite 'Festina Lente' USA10;Dragon...'Here there be Dragon'...unregistered;Holly...unregistered;Etc.

  5. #5
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    Default Re: A blatant Plug

    Charles!

    The Software is Vacanto Prolines by Vacanti Software. I have very little but praise for it. It is easy to use, reliable and does very nearly everything I want (it won't draw diagonals, but they are very much out of fashion these days).

    If you take the view that everything to do with a Footy should cost roughly zero it's crazily expensive - from memory it's about USD 200 - but if you think of all the other things I could have been spending my money on over the three years I have been using it, it is very cheap indeed. Put in terms that will send horrors up you spine, it has so far cost me something like 4 cigarettes a day (Take Snus. Vote for Sweden! Gul och blaa!).


    Barrett!

    This design of sheerline is called (at least in the Royal Navy), a 'swan deck'. Its function on a frigate (I think Americans call them something else if they are made of metal and have gas turbines) is to preserve seakeeping ability in a head sea while lowering the main weapons deck. The latter brings weapons closer to the roll centre so that target locking is easier, lowers the centre of gravity, reduces windage, cuts overall weight, etc.

    In a Footy, the main reason for doing it is to allow Stollery/Sanderson type 'surface mount' technology and cassette electro-mechanicals without giving away any draft.

    I take it by 'deep keelson' you mean 'lots of rocker'! If you look at the sections this is nothing like as extreme as it looks - all that has happened compared with Moonshadow, etc. is that the sections have been made slightly more V-ed below the turn of the bilge. The change in prismatic coefficient is actually quite small. The intent (hope? aspiration? rank fantasy?) is that this may reduce heave (i.e. vertical bobbing-up-and down movement) in light weather to which the Moonshadow and Voortrekker types have proved to be unusually suceptible.

    Last edited by Angus - DECEASED; 12-05-2008 at 02:55 PM.
    A.

    He who dares sometimes wins.
    He who doesn't always looses

    Footys GBR 26 Little Gull
    GBR 28 Dingo
    GBR 61 Merlin
    GBR 71 Akela
    GBR 77 Sun Dog
    GBR 171 Mandeln i gröten

  6. #6

    Default Re: A blatant Plug

    Buttocks and section views show considerable tumble home. The ends are full, pehaps to help dampen pitch and minimize submarine. Will probably have a fairly high Cp. I like it. Sure enough has to be a split female mold or it ain't comeing out. Will look forward to additional info and pix.

  7. #7
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    Default Re: A blatant Plug

    Given the very light scantlings of Footys it is quite posible to 'pop' it off a male mould and add the transom and/or bow block later
    A.

    He who dares sometimes wins.
    He who doesn't always looses

    Footys GBR 26 Little Gull
    GBR 28 Dingo
    GBR 61 Merlin
    GBR 71 Akela
    GBR 77 Sun Dog
    GBR 171 Mandeln i gröten

  8. #8
    Join Date
    Feb 2006
    Location
    old lyme, CT. U.S.A.
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    Default Re: A blatant Plug

    Interesting on the "Swan deck" Angus, it will definitely give you some more interior volume to play with. My comment on the "pronounced keelson" was actually more in reference to the "Vee-bottom" you mention; either way, you've managed to answer my question. *laughs*

    I like many others, will be interested to see the boat's progress!
    the pessimist complains about the wind, the optimist expects it to change, the realist trims the sails.

    Footys:
    USA 39 Bearfoot
    USA 62 Stiletto
    USA 190 Eclipse
    USA 97 Orange Crush
    USA ??? Albatross (in progress!)

    Sparkman Micro Marine
    builders of Footy hulls

  9. #9
    Join Date
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    Location
    Leicester, UK
    Posts
    424

    Default Re: A blatant Plug

    By any Angus standards this is hardly any tumblehome at all! I have no worries about removing either an epoxy-glass moulding or a vac-moulding from the plug

    It says here

    SOOOOO,

    We have a side view, as in the last picture with 6 buttock lines (each side of the hull) so we will be laminating 12 pieces of 6mm Balsa to give a block which will, of course be 72mm wide before sanding, etc.

    (probably worth saying - there is a free demo version of Prolines. It lacks bells and whistles - you can't save or print, but I can receive one of the Master's designs, adjust anything I see fit. (actually I only record the overall dimensions and adjust the buttock spacing to suit the wood I have))

    To get full size patterns what I do is:
    • Using the last picture I "print screen" to put the picture onto the clipboard, then set up a word document with A3 paper in landscape format and
    • Paste the side view into the document
    • Then I crop (picture menu) to the bow and stern lines (and remove most of the junk at the top and bottom of the picture.
    • Using picture menu again I adjust the overall length of the picture (and hence the hull to the Prolines overall length (13 inches - welll done that person)
    • Now I have a full size side view with all the buttock lines the correct size and relationship.
    • I mark three holes down the length of the boat - you will see why later
    • I then copy the drawing 3 or 4 times on a sheet, and print several

    Then its time to cut out enough paper patterns (its a VERY good idea to label them 1 to 6 since they are similar looking


    Stick them to the balsa sheet (or MDF or Extruded polystyrene) - I use spraymount and cut them out
    A bandsaw would be ideal, but for balsa a sharp knife and sanding block are sufficient

    YES - I have used pictures from another plug to illustrate the process - I have not taken enough photos of all the stages for Bakers Boz.

    So now we have 12 labelled buttocks for the plug - each with 3 holes in them for registration.
    At this point I coat the inside of each piece of balsa with a fairly dark acrylic paint

    You will see why later

    In the picture I have already peeled the paper patterns off the parts, and there are 3 barbeque skewers ready to act as dowels to assemble the buttocks in the correct location.
    This is particularly important for this design, as the dropped rear deak gives an non-level deck line (in fact I aim to make the plug with a level deck line, and cut away the mouldings later - which is why the buttocks don't show the dipped deck)

    andrew

  10. #10
    Join Date
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    Default Re: A blatant Plug

    Nice work and a nice tutorial Andrew. Using buttock lines when you have them certainly makes for cutting many fewer parts than using the cross sectional lines drawing.
    www.scalesailing.com
    Home of the 'Foamy Footy' since 2006
    www.oddguyart.com
    My shirt brand, look good while you sail.


    Kittiwake (#1) USA (retired);Pintail USA64;Siren USA65;Harpy USA158;Pond Sprite (#1) USA310;Kittiwake K2 (#1) USA410;Pond Sprite 'Festina Lente' USA10;Dragon...'Here there be Dragon'...unregistered;Holly...unregistered;Etc.

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