Plug Building

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

  1. tunnels

    tunnels Previous Member

    We rolled on 2 coats Norpol green tooling gel and backed it up with black


    Theres a part of your problem right there !! just need answers to the rest of the questions please . :)
     
  2. Tad
    Joined: Mar 2002
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    Location: Flattop Islands

    Tad Boat Designer

    And you are completely wrong.

    Panel "curvature factor (Fk)" has been in all modern scantling rules, ABS, Lloyd's, ISO, for at least 20 years.
     
  3. midnitmike
    Joined: Apr 2012
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    Location: Haines and Juneau

    midnitmike Senior Member

    You never want to let facts get in the way of a opinion.

    MM
     
  4. tunnels

    tunnels Previous Member

    then why dont designers use more shapes to make boats stronger without adding lits more weight !! :confused:!!
     
  5. JRD
    Joined: May 2010
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    Location: New Zealand

    JRD Senior Member

    RW

    I think your question was about the dam? The dam is convex to put the membrane into compression as you say. Concrete has many times the strength in compression than it has in tension, even traking account of prestressing and steel reinforcing.

    Relevance to boats? quite a lot really, except the concrete bit

    Principles of Yacht Design has a section on scantlings and the curvature factor is explained in a straight forward way

    PS - not qualified in dams or boats
     
  6. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    As to your plug stick ups, perhaps you should try some mold sealer before application of the wax. As i understand it, in order to prevent a stick up, you need to prevent mechanical bite and also chemical linking with the substrate. Wax and PVA together, defeats both of these mechanisms. Mold sealer does the same job as the PVA, provides a chemical barrier and reduces porosity.

    GP resin for example, even though it looks like it would provide an impervious seal, is in fact porous. Im not sure on the products you surfaced your plug with... I use TR wax and it works ok... because i laminate mostly with epoxy resins, which has very strong adhesion properties compared to PE or VE, if i want to assure a good release i have no choice but to use PVA aswell, otherwise i always have trouble releasing... I have also noticed problems when brushing or rolling on the first coat after the PVA is on. The rolling and brushing action ruins the barrier film of PVA, it breaks it up so to speak. So you really need to spray the gel or In mold coating onto the PVAt, although i have done it successfully by brushing onto it- just have to be extremely gentle and i wouldnt risk brushing on a large mold, only little pieces.

    So in short, if you want to avoid PVA, you have to be really careful with what your doing or your new hull plug will get stuck also. I would seal it with mold sealer, use the best wax that you know releases well with your resin, and i would wait 2 weeks after youve made the plug to let all the volatiles evaporate and cure completely. I dont think its worth the risk personally, practice doing the PVA application so that it doesnt leave a bad surface, you should be able to get it quite nice by varying your technique and dilution - i actually get reasonable results by simply wiping it on with a wet sponge, diluted about 50% with water - again only for small molds, and i agree with tunnels in that you only need the smallest film on there, so thin you cant even see the blue tinge on a white surface, and you get a nice finish on your molded parts...
     
  7. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    Funny thing...... if I buy blue PVA from FGI/Nuplex I spray it & get a "marathon event" of runs... wipes on fine with a damp sponge, If I buy green PVA from Fiberglass Australasia It sprays fine, might be different stuff but thats what happens for me. Jeff.
     
  8. Trick Powerboats
    Joined: Apr 2008
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    Location: Al Raha Beach

    Trick Powerboats Junior Member

    First parts

    The first production parts popped out like new pennies, 6 coats of Mirror Glaze #8.
     

    Attached Files:

    1 person likes this.
  9. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    I would use AIREX , fair the unit , make your female mold and KEEP /finish out the plug.

    The Airex boat will be stronger and lighter than the later single skin cookies and a real good performing sales tool.

    Stronger , quieter , lighter , instead of in the scrap pile. Advertise GREEN!

    A bit more costly tho, Airex isn't cheap, and fairing is a week of UGH!
     

  10. tunnels

    tunnels Previous Member

    congratulations !!!

    What products you used and the methods you used and how you used everything must all be compatable and i am so glad for you .
    Some one else could do the same job and change just one thing and have a complete disaster . there are so many variables with glassing and products . trouble shooting problems is really just a process of elimination!
    You just keep working through the list till you find the one that fixes the problem . :D
     
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