Best method to takeoff model half hull?

Discussion in 'Boatbuilding' started by bntii, May 3, 2011.

  1. bntii
    Joined: Jun 2006
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    bntii Senior Member

    I have been lent a antique half hull model which is for my old Rhodes.
    I was given it so I could produce a similar half hull model and I am looking for the best approach to create a mold from this existing model.
    The model appears to be a glass layup though seems to have some pure resin on the surface and filling the details. The model has been dropped in the past and has some repaired cracks and chips. Its old.

    I have the full range of glass, epoxy, fillers, paints, vac setup etc for layups. I have experience- I am in the marine trades.

    What I am looking for is the best approach to mold the model with the least chance of damage.

    Currently I am thinking of going the mold release, spray primer & layup shell for a female mold.
    To build the new model, I would vac down a layup into the mold and presto- new half hull.

    Is there a better approach?
    Possibly using some sort of latex mold, or other casting material?

    There are some fine details I would like to transfer to the mold such as the outline of the rudder and a embossed cove stripe.
    The half hull is ~ 30" long and is of the classic Rhodes hull form. I will get a photo posted of the model.

    Thoughts?

    Thanks all
     
  2. cthippo
    Joined: Sep 2010
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    cthippo Senior Member

    How big is it?

    Can you make a casting box and do it in RTV?
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There are lots of ways to pull a mold from a half model. Everything from vacuum formed plastic to plain 'ol plaster of Paris. Latex, polyester or epoxy resin, even Play-Doh or modeling clay can get the job done.
     
  4. BATAAN
    Joined: Apr 2010
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    BATAAN Senior Member

    A common thing in the movie industry is to use a silicone casting material backed up with a plaster mother mold. Smooth-On Inc is a supplier that has everything needed for casting props. Basically you apply release, cover the thing with one of the flexible moldmaking materials, then build a rigid support with plaster that supports it. The mold slips in and out of the plaster so you can work it off of the original object. A half model should be dead easy.
    Check out the Prop Forum for ideas and leads. These are a bunch of obsessive amateur nerds that share their ideas. http://www.therpf.com/
     
  5. bntii
    Joined: Jun 2006
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    bntii Senior Member

    Great- thanks all for the replies.

    I am cautious with this as it has high sentimental value to its owner, is quite old and already damaged. I am just a bit reluctant to use direct GRP molding techniques as a result.

    That sounds like it might be the ticket BATAAN, thanks.
     

  6. BATAAN
    Joined: Apr 2010
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    BATAAN Senior Member

    These silicone products and techniques preserve incredible detail without damaging the original, given proper care in their use. http://www.smooth-on.com/ The catalog is a fountain of ideas and knowledge.
     
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