Need Help With Wood Working

Discussion in 'Boatbuilding' started by CatBuilder, May 28, 2011.

  1. CatBuilder

    CatBuilder Previous Member

    I figured I'd save some money, add a tiny bit of weight and speed the building process along by making my bulkheads from 12mm Okoume. It's an option in the plan.

    I blew up the AutoCAD files to 1:1 and printed life size templates to cut from a flat sheet of ply, epoxy and cove into place.

    Dead simple, right?

    WRONG!! :mad:

    I lost two hulls before from working with wood. Did I mention how much I f*%(! hate the stuff? Again, I'm having problems with it even on a simple task like trace, cut and cove.

    Here is the problem:

    I put two coats of epoxy on a pair of bulkheads yesterday morning. The shop was 68F (20C). I used fast hardener and did one coat. As my shop warmed up, I saw bubbles forming everywhere in the first layer of epoxy. Obviously wood out gassing. The wood had a moisture content of 10%.

    I popped those bubbles and smoothed a couple times, but they kept reforming. When the epoxy went off, I ended up with popped bubbles (craters) with a pinhole in them. I figured the second coat would fill those in, but the same thing happened. Bubbles, then pinholes.

    At $100 a piece for the bulkheads, I installed them anyway, but when I did it was about 94F (34.4C) in my shop, so I figured the outgassing was pretty much done. I coved them in well, so the only exposed holes are now on the faces, which I will add another coat of epoxy to when the boat is complete and upright and when it is very hot out.

    Question:

    I am getting started this morning and it is again 68F (20C) in the shop, but since we appear to be entering rainy season, it is also 94% humidity. This is the first day it has been humid like this since last year. We are forecast to get rain every afternoon and the ground still has puddles everywhere from yesterday's rain. It's like this all summer.

    I do have a large air conditioner I bought to combat heat and moisture. However, it is 68F (20C), so if I use this air conditioner to fight the moisture in the building, I will drop the temperature down to about 60F (15.5C) and chill the uninstalled and unepoxied plywood bulkheads down.

    As the shop warms up (the air conditioner is for spot cooling and does not cool the entire building), the plywood will then be cold and will attract the moisture from the atmosphere as condensation.

    I am trying to coat the plywood in the morning so I can then install it as a bulkhead with a cove joint while the epoxy is still in secondary bonding stage - no sanding.

    What do I do?!? :confused:

    How do I ensure that my plywood is not going to outgass as I'm coating it with epoxy?

    Using the air conditioner, how can I control the humidity properly so that I can work?

    Is it better to have cold plywood that is in a dry environment, or hot plywood that's in a wet environment?

    Thanks to anyone who can suggest what to do. Wood was the death of my last project. I don't want it to ruin the wonderful plastic boat I've built. :(
     
  2. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    I would epoxy the wood while it is at its hottest so it won't out-gas or gather moisture. You might even want to artificially warm it with a hair dryer before applying the coating. This way it will stay warmer than the ambient air and avoid condensation. You will be uncomfortable but you will avoid bubbles.

    Stay hydrated. If you start to feel confused, take some juice and put a cool, damp rag on your neck and forehead. This should help keep you on track.
     
  3. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Oh, and make sure you are more careful than I was this morning!
     

    Attached Files:

  4. CatBuilder

    CatBuilder Previous Member

    What are we looking at there, for an injury? I see a butterfly band aid. Open gash?

    Anyway, I did just what you said. I cut out the bulkheads in the AM, epoxied them up just after lunch and installed them as the afternoon went on.

    No outgassing.

    Thanks for the tip.
     
  5. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Yep. Open gash from hole saw. Drill jumped and got me, but not as bad as the last time that happened though. It could have been a lot worse.
    My next suggestion was to heat the wood under the open sun before coating to drive out the moisture but it sounds like you got it whipped. :)
     
  6. hoytedow
    Joined: Sep 2009
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    hoytedow Wood Butcher

    Being ambidextrous, I have another hole-saw scar on my right hand. :p
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Hoyt has is right, you're applying goo when the wood is in a warming cycle. It has to be the other way around or you'll out gas. The easiest way to solve this problem is to warm the wood and/or the goo, then apply as one or both are cooling. It'll out gas in reverse and actually suck in the goo, rather then try to spit it off. You'll often see me up late at night this time of year for this very reason, working as things cool down.
     
  8. CatBuilder

    CatBuilder Previous Member

    Gotcha. Thanks.

    Another question on the plywood:

    I have it stored in a shipping container standing upright, leaning against the wall. It's 12mm Okoume. Will it be fine like that for a year, or do I have to lay it down and stack it carefully?
     
  9. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    If they start bending (which is likely), place some 2x4's behind them, three should be enough.

    Edit: You could also place the flat against the wall and attatch the stack to it can't fall over. Stacking horisontal works, but place something cheap on top, as you are likely to drop things and generally make a mess. IƤve seen my share of ply sheets with foot prints on them. :)

    Lurvio
     
  10. Bruce Woods
    Joined: Sep 2007
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    Location: perth

    Bruce Woods Senior Member


    Are you then glassing in the bulkhead or just relying on the cove joint?
     
  11. CatBuilder

    CatBuilder Previous Member

    Cove is all that is necessary for non structural bulkheads.
     
  12. Bruce Woods
    Joined: Sep 2007
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    Location: perth

    Bruce Woods Senior Member

    12 mm okume plywood for non structural bulkheads????
     

  13. CatBuilder

    CatBuilder Previous Member

    Only beams need tape. Call Kurt Hughes with additional questions. I don't have time for this. I'm building a 14 meter catamaran.
     
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