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  1. #1
    Join Date
    Mar 2005
    Location
    Bendigo
    Posts
    24

    Cool Wanting to seal premium quality ply

    One of my hobbies is the building and sailing of rc sailboats made from basic 3mm premium 3 ply.(Bunnings have it )

    The American designer recommends the use of penetrating epoxy to suitably prepare the 3 ply for these boats.
    While such products may be available in Australia it appears only to be in packs too large to warrant for projects such as this.
    All it has to do is initially seal the timber ply so moisture does not get in to cause delamination.

    My models to date have been fine by brushing on a 1:4 solution of Bondcrete/water since the timber is then treated with oil base 4:1 sealer, prime, etc. then at least 2 coats of enamel. But would like to get away from water altogether in the treatment.
    I have in mind to try some concrete sealer that I had to combat “bloom” as it appears to have similar content to other timber sealers I read about.
    I will welcome any suggestions or advice.

    Here’s a few photos of my boats so you can see what I’m into to.
    m1.jpg
    IMG_6724.jpg

    mal3 - Copy.jpg



    Also a video which portrays the schooner going against the latest kit boats.
    https://youtu.be/LJoDT9rmfOo


    If anyone is interested to find out a bit more about these boats, please ask or simply visit the designers website.
    BOATS


    I will appreciate all comments and suggestions.

    Mal (Bendigo)
    Attached Images Attached Images

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  3. #2
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
    Posts
    2,810

    Default

    For a basic watertight sealer, I would suggest aircraft dope. This used to be fairly available in model shops in small containers (250ml upwards).
    It was originally used with fabric covered aircraft to prime wooden structural members, glue the fabric panels on to the structure (stretch water damped fabric fairly tightly over the frame, and brush dope over the fabric where it is in contact with structural members, the solvent in the dope softens the prime coat on the timber and evaporates bonding the two materials) and finally tightening and toughening the fabric all over by brushing a couple of coats over the fabric to shrink it.
    It migrated in to modelling as a basic fuel proof coat for timber frames, and to install and tighten tissue paper or lightweight silk covering materials using the same techniques.
    There are two types of dope, depending on solvent and core ingredient, one type is classed as shrinking, the other as non shrinking. From memory the shrinking variety is cellulose dope which is basically a thin solution of celluloid dissolved in thinners, balsa cement is a thicker pasty solution of the same ingredients. I cannot recall the exact ingredients of the non shrinking type, but suspect a solution of nitrate film in thinners.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  4. #3
    Join Date
    Jan 2014
    Location
    Sydney Upper North Shore
    Posts
    4,464

    Default

    I used a very thin 2 part epoxy, that was normally used with fibreglass, to seal and strengthen my balsa gliders. It was called Zpoxy. You could apply a very thin layer with a thin plastic “card”.
    This was used over a tissue and dope layer on the balsa as Malb suggested.

  5. #4
    Join Date
    Mar 2005
    Location
    Bendigo
    Posts
    24

    Default

    Both replies are very interesting, the airplane dope more so as I already have a can of it. I will do some scrap tests with it today.

    Hobby King sell a product called Finishing Epoxy which is a very thin brush on. It takes a day to fully cure but does the job. It is very useful to apply fibreglass cloth. cleans up with metho.

    While I can't recall where I read about this but somewhere there were suggestions to make a sealer using meat tray foam trays dissolved in a thinner, probably acetate. But I think the dope will be more successful.

  6. #5
    Join Date
    May 2003
    Location
    Central Coast, NSW
    Posts
    3,330

    Default

    Hi Mal,
    I can’t help with the sealer - I’ve only ever used epoxy - but I’d be curious to know what you use for rigging line, bowsers (bowsies) and for fixing the rigging to the hull. Also the boom to mast joint, and fixing the luff to the mast.

    I’ve made a few pond yachts myself, tiller or Braine gear steered, and am always looking for good ways to build the rigging.

    Cheers
    Arron
    Apologies for unnoticed autocomplete errors.

  7. #6
    Join Date
    Apr 2002
    Location
    Brisbane
    Posts
    5,773

    Default

    The marine epoxies ( west, boat coat ect) do a great deal more than seal the timber.
    The very effectively penetrate into the top layer of the material and bond the fibres together, substantially increasing the strength.

    But yes, pak quantity is an issue if you only do small projects.

    If you are building model boats, they will not be immersed long term, so the whole think is less critical.

    A couple of things come to mind.

    Shelac can be thinned pretty much as much as you like and will penetrate very well, it is also an excelent buffer coat, nearly anything will go over it.
    Zinzer, make a specialist primer bassed on shelac that is designed to hold out other finishes when over painting .... it can be had in litres in some stores.

    Another thing I keep comming back to is thinners bassed undercoats, in particular Wattyl, Superetch.

    It is a single pack epoxy ( yeh hard concept for some people to grasp) thinners bassed etching primer.

    It is my go to primer for almost any purpose.
    Because it is relatively thin, it penetrates into timber very well AND it is a reactive resin ... that means when it is off it is off and won't redsolve in solvent.

    It is not a high build product , but you can choke timber grain out with it very effectively with several coats.

    Not sure if the thiners bassed version comes in small containers , I buy in 4 liter and 20 litre.

    There is a turps bassed version under the Killrust brand, that comes in litres and 500mL ...... not as thin and does not penetrate as well or dray as fast ...... but it might be worth a look.

    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

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