Thursday, February 9, 2017

More Plywood Issues

  Yet another gripe about the quality of the plywood I'm getting:  I flipped over one of these long ribbons of plywood I have joined I found this.

 An area of delamination a little bigger than my hand, right at where the warped plywood sort of came down and kissed the moist concrete floor.  As you see here, it is discolored and rising up in little swollen ridges.

  I became immediately concerned that the plywood was not what it claims to be and I have just spent several days inadvertently starting a boat project with interior plywood.

  Luckily, the piece was on the end where the corners will be cut away anyway, so I cut off a sample and threw it in a pot on the stove with a piece of interior plywood as a control to make sure I was being aggressive enough in my test.  

  The test piece held together, which was very reassuring.  Here you see it next to the bits of the control piece.

  The most surprising thing was how long it took the interior plywood to delaminate.  I boiled the stuff for over an hour and still I had to pull the interior stuff apart with my fingers.  This was several days ago and the interior piece from another pair of samples I put in cold water is still looking really good.  I have to pull pretty hard on it before it will come apart.  I see now why people do the boil test!

  My conclusion is that there are imperfections in the gluing process as just like every other part of plywood production and that these areas of delamination just have to be dealt with as they arise. 


  1. My own plywood trust issues are what spurred me on to laminate with two three layers. Not only do you have a better 'feel' for what is ultimately between your final sides, but you wind up with more plies and more strength.

    It is important - for me anyway - to feel good about what I'm using and what I have done. That is why testing is so important. You get some confidence from your decisions.

    My advice to you is, if you are concerned still, address that concern before continuing. It can taint the whole project for you. It is still early enough to make changes.

    My own costly mistakes get treated (in my head) as education. It's all good :-) Wishing you the best!

    1. Thanks, Alan. This bit, I will fix with some fiberglass next time I have some extra epoxy I don't know what to do with.
      You are the testing guy, for sure. I would like to get more into these tests some day.