New forum member (equivalents in foam to 9mm marine ply?)

Discussion in 'Boatbuilding' started by Initial_G, Aug 30, 2014.

  1. Initial_G
    Joined: Aug 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Initial_G Junior Member

    (and his hopefully soon to be build)

    Hi people

    Greetings from Belgium, Europe

    @ present, havent started any build yet
    I did buy 2 sets of plans
    - K-Designs KD860 Cat
    - Scarab Avalon 9 Tri

    I first bought the KD860 plans, but then came accross the Scarab Tri, and decided to build that one (or try to @ least :D)

    Plans call for a plywood 9mm construction
    But I came accross PVC Foam info, and figured, lets go with that
    Then HDPE (High Density PET) came to my attention...
    Choices choices...
    Waiting for info on both materials to check what would be best (price/quality) to work with.


    So first question (did look on the forum about this but couldnt really find a deff answer):
    What are the equivalents in foam to 9mm marine ply?

    Thanks

    G
     
  2. gonzo
    Joined: Aug 2002
    Posts: 13,469
    Likes: 342, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    They are not really equivalent in any strict sense. These different materials have to be incorporated in the structural design which produce very different results. The plans will have specifications, stick to them. Otherwise, you will need to re-engineer the design.
     
  3. TANSL
    Joined: Sep 2011
    Posts: 5,651
    Likes: 170, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    As rightly said Gonzo, they are not strictly equivalent. In fact, they are not equivalent at all. What you have to look for is a material having mechanical properties that allow it to support, with a certain thickness, efforts supported by the 9 mm thick marine ply.
     
  4. Initial_G
    Joined: Aug 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Initial_G Junior Member

    Thanks guys

    I figured I could go 12mm PVC foam instead of 9mm plywood as Ray's new Scarab 32 can be made in both 9mm ply or 12mm foam
    + I have read a blog someone made that also exchanged 9mm ply for 12mm PVC Foam on a scarab 22

    grtz

    G
     
  5. upchurchmr
    Joined: Feb 2011
    Posts: 2,847
    Likes: 89, Points: 48, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    So do you have the laminating schedule for the glass on the 12mmPVC foam?
     
  6. TANSL
    Joined: Sep 2011
    Posts: 5,651
    Likes: 170, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Initial_G, in your first post you said: "What are the equivalents in foam to 9mm marine ply."
    From my point of view there is not equivalence. Now substitute marine ply with a laminated sandwich consisting of GRP and a foam core, yes it is possible.
     
  7. Initial_G
    Joined: Aug 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Initial_G Junior Member

    Hi Tansl

    Sorry, english isnt my native tongue
    I been reading the forum and it seems PVC Foam has a lot of advantages vs wood ply.
    Thats why I wondered if PVC Foam was a better choice to build my tri.
     
  8. Initial_G
    Joined: Aug 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Initial_G Junior Member

    Hi Upchurch.

    Again sorry for my lack of knowledge in English, but what do u mean?
    Already checked with suppliers
    Seems Epoxy Resin is highly compatible (read perfect) to work with PVC Foam
    So was thinking glass laminating on PVC wouldnt be an issue
     
  9. TANSL
    Joined: Sep 2011
    Posts: 5,651
    Likes: 170, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Nor am fluent in English.
    Note that if you change the hull material, you must also change some constructive solutions: union system among floors and frames to shell plates, shape and properties of the longitudinal reinforcements, etc ... So change the material is not to change a certain thickness to another, but change many things.
     
  10. gonzo
    Joined: Aug 2002
    Posts: 13,469
    Likes: 342, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The construction techniques need to be changed as well. For example, plywood core hulls can have a hard bulkhead attached with no problem. Foam core hulls usually need a more flexible bond, like a layer of foam in between. You can't just substitute materials and build it the same way.
     
  11. Initial_G
    Joined: Aug 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Initial_G Junior Member

    Thanks for all the replies
    Guess it'll be plywood
     
  12. rwatson
    Joined: Aug 2007
    Posts: 5,829
    Likes: 271, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    If you are new to boatbuilding, you will be pleased with your decision,

    Do a search on safety with Epoxy to ensure your ultimate comfort
     
  13. Initial_G
    Joined: Aug 2014
    Posts: 10
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Initial_G Junior Member

    Next question about plywood

    Seems theres 2 woods used: Okoume and meranti

    I read that Okoume rotts faster then meranti.
    Meranti also seems harder but heavier then okoume

    On a 9m boat it seems the overal weight increase would be only around 10%, although the difference in weight between the 2 woodtypes is about 20%

    So would Meranti plywood be a good alternative to okoume?
     
  14. rwatson
    Joined: Aug 2007
    Posts: 5,829
    Likes: 271, Points: 83, Legacy Rep: 1749
    Location: Tasmania,Australia

    rwatson Senior Member

    Go lighter ( possibly cheaper )

    You're going to epoxy it, if water gets in, they will both rot, if it doesn't, they wont.

    Its the structural thing that makes marine ply better.

    Dont paint anywhere inside the boat that you dont have to - that way you can see any problems like water coming in from outside.
     

  15. TANSL
    Joined: Sep 2011
    Posts: 5,651
    Likes: 170, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    Initial_G, it is possible that by placing plates in a lighter material, and certainly less strong, you have to put more reinforcements, and stronger. It is therefore difficult to judge whether the okumen will result in a lighter vessel or not and, especially, would be impossible to know the difference.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.