Crosslinked PVC vs Balsa Core for Foils

Discussion in 'Materials' started by CatBuilder, Jun 1, 2010.

  1. apex1

    apex1 Guest

    Thanks Kyle.

    It seems you become a high value member and a serious resource of highly demanded information for the building members here!

    I whish we would have not only one of your class from the manufacturers / suppliers side present here!

    Stay with us.

    Regards
    Richard
     
  2. CatBuilder

    CatBuilder Previous Member

    Ok, I'll look into the paulonia and ask Kyle about it when I do my epoxy order in a couple weeks.

    Now for the deck coring - balsa, corecell or maybe nida core?

    Are they all pretty much the same? They'll all delaminate if they get wet, right?

    I know I saw a large number of production cats with "foam" cores delaminating a few years back. I haven't seen balsa delaminate unless it was wet. Also, I have no clue about nida core, but it was suggested to me on another forum.
     
  3. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Balsa: OK for a deck, from a technical point of view, but remember what I said before. Do protect it well, and make a note in your logbook, including instructions, for a next owner.

    Core-Cell: Use T foam. For a deck stiffness is more important then impact, unless you expect a lot of 1 lbs shackles falling from ships... :)

    Nida: I would not use it, the shear modulus is a bit low, which makes for less stiff decks. (I have used it).
     
  4. apex1

    apex1 Guest

    Seems to be hard to grasp (and it is a hell of a mess that you open a new thread for every detail)

    PAULOWNIA TOMENTOSA
    is the name of the core

    GOT IT?

    Regards
    Richard
     
  5. CatBuilder

    CatBuilder Previous Member

    Richard, I trust your opinion. I thought you meant Paulowina for the foils only. I didn't realize you meant for the decks. Where has this material been used before in such an application?

    Any examples out there? I don't want to be the first to try anything.

    Thank you for the tip on the Nida Core sheer modulus, Herman. That was a good save. I was leaning toward the nida core in some ways. At least I can cross it off my list.
     
  6. apex1

    apex1 Guest

    Nida is not worth talking, to start with.

    Kiri is not known in the entire industry. I am the first one to produce a Kiri sandwich (decked by ironwood) on a larger scale. But where is the risk? When you have a material with superior properties for a given application, and the only worry could be a weaker shear strength or a worse rot resistance, but in both cases Kiri outperformes them all.

    Share your doubts with Kyle, and be fair, your experience too (once gained), and build your deck in Kiri. Supported, as mentioned! Either by a thin layer of ply or by GRP. Probably both, as we do it.

    Regards
    Richard
     
  7. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Perhaps you could even use Kiri wood as a sandwich material... :)
     
  8. CatBuilder

    CatBuilder Previous Member

    I may be going with AL600/10 balsa because it saves me a step of pre-coating the core.

    I ran the idea of Paulowina past the designer and his reply was:

    "its in my Post-Apocalyptic Boatbuilding.

    harder to find than I first thought."
     
  9. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Is this designer serious?

    Bread bags as a substitute for gloves, venturi vacuum pumps (costing a fortune on compressed air), using the shop vac as vacuum pump (untill it smokes out, usually in 10 minutes or so. Also the pressure difference is small (Festool claims 280 mbar, where you wised for 500 or more) and getting the mixing ratio right by dribbling epoxy and hardener into properly sized circles on a piece of paper. (keep paper ready with different circles for different temperatures, or even better, recalculate for volumetric mixing ratio, and cut the end of a syringe.)

    For the rest it might be a good article.
     
  10. apex1

    apex1 Guest

    The Kiri is not used in the same way as Balsa. The latter stands "upright" between the decking layers, the Kiri would be a plank (not endgrain as the Balsa) installed the same way as in strip planking or deck laying. There is no additional pre- coating.
    But several times the strength and noticeable lower the cost.

    Regards
    Richard

    Herman,

    have you been asleep? :D I am talking about Kiri as a sandwich core now since one year or longer.
     
  11. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    zzz zzz zzz :p
     
  12. CatBuilder

    CatBuilder Previous Member

    I think he was trying to say it is still possible to build a boat, even after an economic implosion and there are many ways to save money aside from skimping on a hull.

    His vacuum method is not a typical one. You vacuum bag a core between two sheets of ply which don't require a table, peel ply or any other "stuff." I think maybe since this is a very simple job, the idea is that you can risk losing a panel if your ShopVac dies.

    Those are my guesses, anyway.

    Maybe I will rethink the Paulowina some more. It's a very difficult choice. I did research on Paulowina online and saw that it absorbs water readily, like balsa does. I can understand that we are laying a flat sheet down and it won't soak up all the resin. That is great news. Maybe I'll get a price on the Paulowina and see what this looks like.

    The coring is only for the deck and deckhouse. The hulls are not cored, they are plywood and epoxy.

    Should I be using a scale to mix out epoxy by weight?
     
  13. apex1

    apex1 Guest

    Common is to use pumps to get the right mixture by volume. That is the fastest method, and speed is a issue.

    To the coring method:
    I was referring to a sandwich of ply, Kiri ply, where the Kiri would be layed in planks like a usual wooden deck. All encapsulated by EP of course.

    Epoxy does not penetrate wood very deep, even not endgrain Balsa.
    You must not fear to have a higher resin consumption than with any other wood.
    But again, stay in contact with Kyle, and share your experience.

    Regards
    Richard
     
  14. Herman
    Joined: Oct 2004
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    Herman Senior Member

    It is definately possible to save on stuff, but when using vacuum, not on a vacuum pump (small pumps are available from as low as 150 euro). Compressed air costs a fortune on power bills, so venturi pumps might look cheap, but they are not.
    Saving on gloves by substituting with bread bags is a laugh.

    Saving on making good deals with suppliers is very good possible. For instance we always have a special deal for DIY builders, giving them a fixed discount on ALL materials they buy, during the project. Also many suppliers have 2nd grade or overstock materials that they are happy to sell. We are no different either. Plenty of stuff that can leave for a bargain.

    And always keep an eye on Ebay and other 2nd hand sources. also let everyone know what you are looking for. Materials can fall into your hands from unexpected sources.

    On Kiri as a boatbuilding material: Balsa and any other wood soaks up water very happily. That would not stop me from using it.
     

  15. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    catmando

    Catbuilder, if yout interested in the use of Kiri, a member here & other forums has used it in a 50' power cat as a strip core, he's called catmando = he has done some panel testing etc on the material.
    Also here in Australia the choice of material for dagger board "blanks/core" has often been western red cedar sheathed with triax glass0/45/45 or db45/45 plus a uni fibre laminated into a rebate either side under the glass skin & also as such to the trailing edge, these boards have been very reliable & used on Lock Crowther designs as specified by him.

    regards from Jeff.
     
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