Plug Building

Discussion in 'Boat Design' started by Trick Powerboats, Nov 18, 2012.

  1. Trick Powerboats
    Joined: Apr 2008
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    Trick Powerboats Junior Member

    We're build this 26' center console. Jig frames are complete. We need to install the keel and chines and then its decision time for skinning it. So here's my question? What do you gurus recommend for skinning this thing, keeping in mind there are NO flat surfaces and where on the boat?

    Jeff
     

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  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Cold molding with plywood is the cheapest and also gives you a very stable material.
     
  3. Trick Powerboats
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    Trick Powerboats Junior Member

    Do you recommend laying glass over the plywood? Thanks for your input!

    Jeff
     
  4. messabout
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    messabout Senior Member

    If this is to be a plug, then the molding surface needs to be dead smooth. You can use glass if you like but good quality paint will work equally well. Paint is likely to be somewhat easier to fair perfectly.

    The boat appears to have concavity in the bottom sections. Is that so or is it merely an photo illusion? Concave sections are kind of sexy looking, as in the old time "gentlemens runabouts" , Chris Craft, Century, Riva and such. Concavity may present some structural disadvantages if the boat is to be of FRP.
     
  5. gonzo
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    gonzo Senior Member

    Fiberglass cloth will create more problems for fairing. You can saturate the wood with resin and then spray fairing compound. Polyester works fine since the plug won't be out in the weather.
     
  6. Trick Powerboats
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    Trick Powerboats Junior Member

    Right on! Thanks guys!
    Jeff
     
  7. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Duratec....save time and money...spend it on the right product from the start and it ends up cheaper in the long run.
     
  8. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    Are any of the surfaces developable though ?
     
  9. tunnels

    tunnels Previous Member

    what ??

    Concavity may present some structural disadvantages if the boat is to be of FRP. Can you say why?? What would be the disadvantages i am interested why ??? :confused:
     
  10. tunnels

    tunnels Previous Member

    This is a throw away plug ?? its one hell of a lot of work just to throw away later .
    If you made a proper hull you could recover some of you exspenses
    Building plugs from wood it moves as you will find out .
    You can seal the other side of the wood . If your screwing any of the planking bury the screws and dont us any auto bog to fill with Its hard the wood is soft and when the wood moves the bog dosent so even if you glass it will still show in time for sure !!,specially if you have high and low humidity conditions during you building !!.
    The 36 foot boats we made Korea we 100%tented over and under the plugs (deck and hull ) and maintained a constant temprature and humidity level till the moulds were made and removed off the plugs . if you use a dehumidifyer remember to cover the concrete floor, Loads of moisture come out of concrete walls and floors etc etc all your timber and what ever is being used in the plugs construction needs to be conditioned as well in the same place !! :p:)
     
  11. sushkin
    Joined: Aug 2010
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    sushkin Junior Member

    As a variant you can skin your mold like this - http://www.boatdesign.net/gallery/showphoto.php/photo/20467/ppuser/38824 . It's laminated with two layers of fiberglass for additional strength, so you can walk on it and it doesn't bend when you sand it out. As fasteninigs we used air powered stapler. It took us two weeks and 4 people to skin the mold, sand it out and spray.
     
  12. tunnels

    tunnels Previous Member

    My choice would be to double diagonal plank the whole boat and use staples to hold the glued skins to the frames and to then selves angle the stapels so the get a better hold , and make sure the staples below the surface just a little screed a coat of epoxy filler over the whole thing and long board . Use multiple coats of Hi build with q celles added an fine sand always ling boarding . when it 99.9% finished and fair duratech with a generous couple of coats then 600, 800 ,1200 wet and dry sand and then polish with a electric buff through a couple of grades of cutting compounds to get that deep luster then start waxing .
    Sounds easy and it will be if each step is done properly . Curves and shape will hold the hull ridged and as for saying you have structuall problems because its concaved what a load of rubbish . the shapes in every panel are great and will make the hull really ridged . Just make sure you use a decent glass layup solid in the bottom from the chine down and 6mm 0r 9 mm sheet corecell in the top sides from just above the chines up to just under the gunnels !
    Having what kind of power units ?? Inboard sterndrive ?? or single or twin outboards on the transom or mounted on a short bracket ??
    A big black 350 Verado on the back !!! yeah man !!!
    You going to do wood grained decks ??
    Man id love to be on that project !!:D:p
    Need lots a pictures of everything as you going along !!
     
  13. Trick Powerboats
    Joined: Apr 2008
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    Trick Powerboats Junior Member

    Thanks for everyones input on this! We've decided to diagonal plank it with MDF. There are a few areas where we'll try full sheets or at least as big as possible.
    Yes, this is a throw away plug. Didn't see much reason to build a wood version when we can build one from composites...
    We'll be using Duratec as well...
    I'll post some more pics after the first layer of planking is finished...
    Jeff
     
  14. tunnels

    tunnels Previous Member

    If you diagonal planking what we did was groove the back of the wide planks About 2/3 the deepth of the plank and about 10mm apart !! It holds its longtudinal strength 100% but allows the plank to be able to get a slight curve cross wise !! . Some planks we managed to get on were 250mm wide and was a piece of cake , we were using 15 mm thick ply wood so was quite solid !! also used a internal /external rolled edge where they butted together . Had two routers one with internal, one with external bits bead and flute they calls on 15mm thick used a 20mm dia bit so the fitted together much easyer on a rolled over part of the hull . That way as you rolled over differant parts of the hull and planks changed shape once cut to the right shape then do the edge with rounds and able to completely glue the edge from end to end and they interlock . once set up was a breeze and when the glue hardened could walk on it and never moved . We used epoxy glue !! if you use anything with any kind of moisture then you get problems with bucklng and exspansion then shrinkage later when it starts to dry again etc etc !!:D;):p
     

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  15. messabout
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    messabout Senior Member

    The skin loading of a boat is mostly from the outside in. If the sections are concave, then the skin is loaded in tension mode whereas if the sections are convex the skin is more nearly in compression mode. That is not to say that you can not or should not build with concave sections. You may need extra skin thicknesses or extra framing however. Cost and weight could then become a factor.
     
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