Foam, glass, epoxy, resources to learn how to use?

Discussion in 'Materials' started by skyl4rk, Jan 17, 2023.

  1. skyl4rk
    Joined: Aug 2006
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    Location: Lake Michigan

    skyl4rk Junior Member

    I would like to learn how to use foam, glass and epoxy to build boats. In the past I have used plywood, glass and epoxy but am interested in the lighter weight and buoyancy of foam. Are there any resources on how to get started with foam from the very basics? I need to make a hatch, and could use that project as something to start with. The kinds of questions I have are total beginner questions: Which foam to use? How thick? Best practices to cover it with glass? How to lay it up on a mold? How to beef up attachment points? When and where is foam a better material than plywood? Looking for a good starting point to learn how to use foam.
     
  2. comfisherman
    Joined: Apr 2009
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    Location: Alaska

    comfisherman Senior Member

    I'm away from my library but ther was a book that is getting a little dated but goes over the ins and outs of foam building.

    I did the diy method and bought several types and did some small projects to get a feel for the stuff. It doesn't take long to figure out what you like and don't. I've standardized around h80 weight form in various thicknesses and coosa for stringers, beams and the like. Learned real quick I hate the expanded plastic honeycomb, that coosa will take a camber but man will you earn it.

    My supplier was really good with engineering questions, not sure if it's common to give that much help but they have been great. Giving solid guidance on reccoemdations and resources for the various foams I've used.
     
  3. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    The best way to start building in foam is to build to a specified laminate schedule and not try to create your own.

    So, learn to build first and not worry about designing anything which is altogether different.

    For a hatch, you need to define the shape and operating parameters. So, say square 24x24 with the ability to walk on...

    For something like that, we can probably help you create a layup based on experience. For more critical things like transoms or hulls; where loss of life is possible; those are designed based on strength criteria and should be left to more qualified persons.

    Foam is super easy to build with; let us know the details of the hatch.
     
    bajansailor likes this.
  4. skyl4rk
    Joined: Aug 2006
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    Location: Lake Michigan

    skyl4rk Junior Member

    The hatch is 24" x 48".

    At the moment it is too cold to work with epoxy. I am mainly interested in learning about working with foam. Are there some search terms I could use to find info?
     
  5. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Walk on or not?

    A big hatch like that..Is it flat?

    Just you tubes..

    foam or corecell or divinycel & boat
     
  6. skyl4rk
    Joined: Aug 2006
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    Location: Lake Michigan

    skyl4rk Junior Member

    Thanks
    I want to build the hatch cover in two parts so one slides over the other and both slide partway off the hatch opening, so one or both parts will have a supporting member as a crossbeam across the hatch opening. It is a flat hatch with a coaming and a flange, about 2" above the deck.
     
  7. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    You'll need a simple drawing before we can help you well. Might be easier in acrylic and u get light?
     

  8. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    A piece of acrylic that covers a 24" span and which will withstand walking over will be quite thick.Its good to see a poster with the willingness to learn a process and the good sense to begin with a small item.That way even a total disaster is not much more than a minor cost in the learning process.Is there a particular reason to specify epoxy for the laminate?On a global basis,the vast majority of boats are built with polyester and it serves the purpose extremely well for most use.

    Polyester is more dependable for staying attached to a pigmented gelcoat and you will find a huge range of shades available.It also works with mat,which epoxy may not,depending on the binder,and mat itself is more amenable to wrapping round curves than a woven or biaxial material.The important thing with foam cores is not to be guided into buying any kind of foam that isn't closed cell as open cells can absorb and then transmit moisture.the brands mentioned above are good and I would add Airex to them.to get maximum benefit from any of them it is essential that they are bonded to the material above and below their position in the laminate-just laying a slab of foam in a mould and leaving a small sandbag or similar on top of it isn't a guarantee of success and doesn't work on a near vertical surface in any case.Normal good practice is to balance the laminate on either side of the core.For stressed areas a section of the foam is removed and a more solid material is used to replace it.I believe you Americans have something called G10,which seems equivalent to one of the glass based Tufnols,and this is a brilliant material for inserts even though it is really hard on tools.
     
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