Ultra thin sheet metal as moisture barrier in plastic composite.

Discussion in 'Boatbuilding' started by SeaSpark, Jun 27, 2006.

  1. SeaSpark
    Joined: Mar 2006
    Posts: 593
    Likes: 17, Points: 0, Legacy Rep: 96
    Location: Holland

    SeaSpark -

    There have been a couple of active threads lately which evolved in a discussion about the durability of plastic composite materials.

    One of the key factors in detoration seems to be moisture ingress into the laminate. No plastic material is completely "waterproof" or "dampproof" this is also why in packaging materials for food a very thin aluminium layer is applied.

    Would it not be possible to apply a very thin sheet of aluminium to the outside of a plastic composite hull? Either in mold or afterwards via vacuum bagging? It could also be strips like in cold moulded wood building. If a transparent epoxy coating is applied as a last layer you would end up with a shiny aluminium hull (no to my taste but people seem to like it) Aluminium sheets can be anodised in any color (or crome if you want). Anodising also makes any other coating unnecessary. Scratches can be fixed by "gluing" a ultra thin sheet over the affected (filled) area.

    Comments welcome.
     
    Last edited: Jun 27, 2006
  2. DanishBagger
    Joined: Feb 2006
    Posts: 1,540
    Likes: 46, Points: 0, Legacy Rep: 523
    Location: Denmark

    DanishBagger Never Again

    That seems like a nifty idea.

    Just a couple of questions from an amateur:

    If the hull is mainly CF, wouldn't it be a bad idea to use aluminium as the barrier-sheet, isn't that just introducing another, just as vital, parameter to the composite orgy?

    Also, how about those mylar bags for wine, is that also covered in aluminium or is that something else (because if it is different, maybe that could be used)?
     
  3. SeaSpark
    Joined: Mar 2006
    Posts: 593
    Likes: 17, Points: 0, Legacy Rep: 96
    Location: Holland

    SeaSpark -

    Orgy & wine bags

    Epoxy is said to adhese well to most metals, as a very thin outer layer it does not play a role in structural strength. Don't see many problems.

    The bags i have seen had an aluminium film, as with most food products this is mostly to keep oxigen from reacting with the product.
     
  4. SeaSpark
    Joined: Mar 2006
    Posts: 593
    Likes: 17, Points: 0, Legacy Rep: 96
    Location: Holland

    SeaSpark -

    Titanium

    How about titanium film as last (first?) layer, titanium has good antifouling properties and unlike copper does not corrode. It is a very scratch resistant metal with a beautiful shine. It's expencive but in thin film material costs are not high, don't know how difficult it is to produce titanium film though.

    From wikipedia about titanium epoxy composite A6 airplane wings i understand epoxy and titanium mix well:

     
  5. DanishBagger
    Joined: Feb 2006
    Posts: 1,540
    Likes: 46, Points: 0, Legacy Rep: 523
    Location: Denmark

    DanishBagger Never Again

    I meant problems as in "corrosion". CF+Alu?


    Oh, so it _is_ alu-foil on there. I was thinking that since it is oxygen proof, it's propably also waterproof. But if that is indeed alu, then one should be able to somehow spray it on, or is it indeed a "sheet".

    Heh, I just had an image in my head of someone using those ktichen aluminium rolls, covering an entire boat in it, painting it over with epoxy. :p
     

  6. DanishBagger
    Joined: Feb 2006
    Posts: 1,540
    Likes: 46, Points: 0, Legacy Rep: 523
    Location: Denmark

    DanishBagger Never Again


    Ah, titanium - I love titanium, I wish I could buy tonnes of it (litterally).

    Anyways, I did a search for titanium film, and it turns out that you need argon, vacuum, and several other gasses (and the danger of explosions), however, I tried searching for titanium foil, which aren't measured in microns, but you can get at thicknesses around 0.001", and sheets which begins at around 0.01".

    However, although titanium has all these great properties, and if you make it like one would do cold-moulding, _and_ covered it with epoxy, you would end up with an epoxy outer layer, and if so, I don't see the purpose, except for puncture resistance and moisture barrier.

    I wonder if you could put it on in strips while vacuumbagging, and therefore get the titanium to be the outermost layer. At 0.001" it should be easily enough formed, methinks.

    http://www.espi-metals.com/metals/cattitanium.htm


    EDIT: I haven't tried (yet), but from the litterature, it seems that epoxy has a hard time adhering to aluminium. Apparently you have to rough up the surface quite a bit and then give it an acid bath of some sorts, and then - instantly _ cover it with epoxy before it has a chance to oxidise. I wonder if titanium would have the same problem?
     
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.