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Re: [Michalak] Re: In most cases you DON'T want to "pre coat" your wood with epoxy!

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  • john colley
    more chance of rot in fresh water than salt.   There is magic in the feel of a paddle and the movement of a canoe, a magic compounded of distance, adventure,
    Message 1 of 21 , Feb 12, 2013
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      more chance of rot in fresh water than salt.

       
      "There is magic in the feel of a paddle and the movement of a canoe, a magic compounded of distance, adventure, solitude, and peace."
      -Sigurd Olson


      ________________________________
      From: Andres Espino <ima_very_cool_cowboy@...>
      To: "Michalak@yahoogroups.com" <Michalak@yahoogroups.com>
      Sent: Monday, 11 February 2013 2:42 PM
      Subject: Re: [Michalak] Re: In most cases you DON'T want to "pre coat" your wood with epoxy!


       
      I agree and if it will be used in fresh water it is not the same issue as ocean use.

      Andrew

      ________________________________
      From: John Boy t1ro2003@...>
      To: "Michalak@yahoogroups.com" Michalak@yahoogroups.com>
      Sent: Sunday, February 10, 2013 5:05 PM
      Subject: Re: [Michalak] Re: In most cases you DON'T want to "pre coat" your wood with epoxy!


       
      I ain't gonna argue the value of epoxy, it is the gold standard.  But for semi-disposable boats, it isn't necessary to coat every inch.  My Normsboat will be a trailer sailor that'll be stored in the garage.  It'll be in the water no more than a week at a time.  The rest of the time it'll be on the trailer.  I'm gonna epoxy the bottom and inside the cockpit.  It'll last for at least 10 years.  By then, I'll have moved up to a different boat.
      John Boy
       

      I have a blog!  http://toon2sailor.blogspot.com/

      “Seaward ho! Hang the treasure! It's the glory of the sea that has turned my head.” 

      Robert Louis Stevenson, Treasure Island

      ________________________________
      From: John Trussell jtrussell2@...>
      To: Michalak@yahoogroups.com
      Sent: Sunday, February 10, 2013 3:21 PM
      Subject: RE: [Michalak] Re: In most cases you DON'T want to "pre coat" your wood with epoxy!

       
      There is a school of thought that suggests that if you don't "seal" plywood
      with epoxy (Gougeon Bros. recommend 3 coats!), the plywood will rot out in a
      season. This may be true of boats built with lumberyard plywood (which
      really isn't anywhere close to what it was 10 or 15 years ago) or boats
      which have enclosed compartments and live in hot, humid environments.
      However, there is another school of thought which suggests that open boats
      built with one of the more rot resistant marine plywoods (such as
      meranti-fairly inexpensive or sapele-very expensive) are no more likely to
      rot than boats built using "natural" wood. About 2 years ago, I built a
      glued plywood lapstrake pea pod (Doug Hylan's Beach Pea) out of meranti. The
      laps are, of course, glued with epoxy, but I did not coat with epoxy. Two
      years later, the boat is holding up well and will probably outlive me.

      I am currently building a Scamp from a kit. The kit uses okume plywood which
      is somewhat less rot resistant than meranti or sapele. Scamps have extensive
      enclosed areas including a water ballast tank, Therefore, I chose to precoat
      all the parts with epoxy (while they were flat). For Scamp, I think epoxy
      coating is worth the effort. However, the decision to seal with epoxy is
      something I will make on a case by case basis.

      Sealing plywood with epoxy has benefits but it also has costs. Epoxy is
      expensive. The rollers and brushes used to apply it and the sand paper
      necessary to smooth it are expensive. It is messy to work with and hazardous
      to sand (a box of rubber gloves and a really good dust mask are necessary).
      Some people become allergic to it. While epoxy does a good job at keeping
      water out of wood, it only works if the coating is unbroken. Drill a hole
      for a cleat or scratch through it by hitting a rock, and water will get to
      the wood and cause problems. In short, any boat builder needs to consider
      using epoxy as a coating, but they should not automatically choose to use it
      as a coating.

      But there are many ways and most of them work. Before epoxy, we used
      polyester resin to stick boats together with fiberglass tape. Before that,
      we used resorcinol or "weldwood" glues and before that, we used screws and
      nails (or trenails and lashings). The boats we built worked, lasted, and
      gave pleasure to their users. Epoxy makes a lot of things easier, but in
      many cases, it is not essential.

      JohnT

      _____

      From: Michalak@yahoogroups.com [mailto:Michalak@yahoogroups.com] On Behalf
      Of souderscott997
      Sent: Sunday, February 10, 2013 11:28 AM
      To: Michalak@yahoogroups.com
      Subject: [Michalak] Re: In most cases you DON'T want to "pre coat" your wood
      with epoxy!

      I agree with you that the paint will lay on easier and smoother on a flat
      piece as opposed to a vertical or semi vertical piece in some cases under
      some tension. The paint also will behave better finish wise on an epoxy
      coated piece.
      A bunch of people seem to be thinking it is necessary to coat the wood
      before any assembly. I just wanted to point out that the optimum strength
      and bond is always with "bare wood", and give some sound reasons why I would
      not "pre coat" in most cases.
      If I were doing a boat with a high degree of brightwork planned for say the
      decks, and possibly the sheer strake or something then I probably would pre
      coat just for the finish reasons you mentioned.
      If I am assembling a stich and tape, or stich and glue style of hull I would
      always stick to bare wood and then just be miserable with the days of insane
      sanding in crazy frustrating nooks and cranny's (you are 1000% correct about
      that)... if again I was out for a high degree of finish in the end.
      I love to strech a buck also so I would be thinking in the end it would
      essentially be a wasted coat of not so cheap in most cases epoxy since most
      designs seem to end with a hull "wet out".

      --- In Michalak@yahoogroups.com , "John
      Trussell" wrote:
      >
      > There are many ways (including not coating with epoxy at all).
      >
      >
      >
      > I like a good finish on my boats. Not a yacht finish (I use semi-gloss
      > paints and avoid varnish), but something that is fair and smooth. Epoxy on
      > plywood does not produce a smooth, fair finish unless you sand it a lot.
      > Once the boat is assembled, such sanding must be done at various heights,
      > various angles, and various nooks and crannies. There will always be some
      of
      > this, particularly if you hope to make the tape disappear (use a very wide
      > putty knife and treat it like mudding drywall). But I hate sanding and I
      > prefer to do as much as possible with the panels flat and at a convenient
      > height. Thus far (and the oldest boat around that I built using this
      > approach is 25 years old) the boats have not yet failed. This is not
      > conclusive evidence that a "mechanical bond" is as good as a 'chemical
      > bond", but is suggests that maybe a "mechanical bond" is adequate.
      >
      >
      >
      > JohnT
      >
      >
      >
      > _____
      >
      > From: Michalak@yahoogroups.com
      [mailto:Michalak@yahoogroups.com ] On
      Behalf
      > Of souderscott997
      > Sent: Sunday, February 10, 2013 2:00 AM
      > To: Michalak@yahoogroups.com
      > Subject: [Michalak] In most cases you DON'T want to "pre coat" your wood
      > with epoxy!
      >
      >
      >
      >
      >
      > Keep in mind a few things when considering "pre coating wood" with epoxy.
      > 1. The wood is a bit more cooperative for bending and twisting when it is
      > bare than when it is covered with hardened epoxy.
      > 2. If you pre coat all of your panels every single application of epoxy
      you
      > apply afterwards only has a "Mechanical Bond" with the layer that it was
      > applied over. The original "Chemical Bond" with the bare wood is far
      > superior in strength and adhesion. It pretty much becomes literally part
      of
      > the wood.
      >
      > When my Wooboto hull was assembled I pretty well followed the
      instructions.
      > I used wire ties to hold the panels together, then tacked the hull with
      > epoxy/wood flour glue with fillets between the ties, then removed the ties
      > and filleted the entire seams, while those were still a bit tacky I taped
      > and epoxyed the seams.
      > That way it is pretty well one continuous "Chemical Bond". Then all the
      rest
      > of the hull is still bare wood so each step i.e. adding the wales,
      glassing
      > the bottom...they are all Chemical Bonds.
      >
      > It is a lot easier to prep bare wood for accepting epoxy than it is to
      > properly scuff and sand an already hardened epoxy surface plus you get a
      > superior bond which is the most important thing.
      >
      >
      >
      >
      >
      > [Non-text portions of this message have been removed]
      >

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