Ripping Douglas Fir 2"x6"

Discussion in 'Materials' started by mariobrothers88, Oct 29, 2020.

  1. fallguy
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    fallguy Senior Member

    Some of that Dixie lumber is great looking stuff. Just buy vertical or rift sawn and avoid the flat grain cuts.

    you can use the bulkheads you built, but remove the knot pieces

    Rumars has also explained the best way to lay wood. However, I believe you are following the designer's build plans. I have watched a few of the Woods ply builds and I recall a few builders laying planks a bit differently, but I believe your method is plenty strong because you are using epoxy. The ply sheathing will not be able to destroy the epoxy bonded wood. You are basically widening the sheathing surface is all.

    Just so you know, there are 3 main varieties of Doug Fir and it is possible you are using a super fast growing one where growing seasons are really long; perhaps Mexican doug fir. The doug fir from NE usa is really good lumber.

    Buy that Dixie stuff vertical or 45 degree grains. It is gorgeous and high quality lumber that I see. One of the pieces in the stack is flat cut. Avoid those unless you want them for something for looks inside the cabin.

    Also, a 1x4 is actually 3.5" wide and will only yield 2 boards at 1.5" wide with two kerfs and about 1/4" waste.

    A 1x6 is 5.5" wide and will only yield 3 boards with 3 kerfs and about 1/2" plus waste

    A 1x8 is 7.5" wide and will yield 4 boards with 4 kerfs and about 1" waste. A thin kerf rip blade of 1/16" would be 1/4" kerf loss and 6" of lumber which would leave a 1.25" rip. And you could cheat a bit and get an extra rip by going a bit narrow. 7/5 is 1.4". If you don't like the cheating idea; stick with 1x4s
     
    Last edited: Nov 23, 2020
  2. mariobrothers88
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    mariobrothers88 Senior Member

    Thanks fallguy I really appreciate your help!

    What's the best way to remove the knotty piece that has been epoxied into place? The only thing I can think of is to use a router to take our that piece would there be a more efficient way to do it? Thanks again everyone for all the wonderful advice!

     
  3. fallguy
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    fallguy Senior Member

    You can use the table saw. Just flip the bulkhead over and run the part over the saw on the knot every inch or so and chisel it out.

    If you get the knot removed; you can half lap a new piece in like Rumars suggested as a repair. Just lower the saw to halfway and rabbet the piece about 3/4" a little deeper than 3/8" for thickened resin.

    You don't put knots in boats.
     
  4. Blueknarr
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    Blueknarr Senior Member

    The router will be safer than balancing that larg of a piece on the table saw and not knowing where the blade is
    Or skill saw slice and chisel.
    Router can also be set to the half lap depth.
     
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  5. Rumars
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    Rumars Senior Member

    If the designer said it's OK then they are really just cleats, in wich case I would just avoid knots and use up the lumber you have. Keep the nice stuff for the actual stringers (the pieces running the lenght of the boat).
    Tijuana is not exactly wood country, you are probably buying US imported wood. For better quality search for a big lumberyard, ask a carpenter shop where they get the wood.
     
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  6. fallguy
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    fallguy Senior Member

    Yes. They are cleats to widen the glue contact area for the ply.
     
  7. mariobrothers88
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    mariobrothers88 Senior Member

    Thank you so much everyone for all the great advice! Can I just remove the small areas where the knots are or should I remove the entire timber piece that has the knot? I think it will be ok just to remove the knot specific area and glue in a knot free piece of timber in that specific area (and save myself some work), but please correct me if I'm wrong! :)

    Here is what the man himself Richard Woods had to say:

    "The least loaded timbers are the bulkhead framing and interior structure, like locker front framing etc. Then deck stringers, then hull stringers. And the most loaded timbers are the crossbeams.

    So you will be OK keeping the framing on the bulkheads. But you will need better wood for the crossbeams. ie under the mast and back of the cockpit.

    Lots of woods are called fir. I would expect Douglas fir to be darker than yours. Lots of woods are called pine or spruce. Thats why the latin name is important as then you know which is which. But in general they are all similar but you should try for as few knots as possible and tell your supplier you will reject those that have too many knots. I try to get wood with knots less than 1/2in diameter."
     
  8. Will Gilmore
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    Will Gilmore Senior Member

    That is true. There are a variety of pines, for example, sold under the name 'Southern Yellow Pine'. A typical yard that sells framing lumber can have a mix of Pine, Fir and Spruce, all sold as the same thing. Any of those woods can make decent boat building material. The SYPs tend to be heavier and stronger. They make good framing wood and are a very common wood used in pressure treated lumber. Care has to be used to select straight grain that goes through the whole length of the piece. Besides being stronger, stability is an issue that is improved with straighter grain.

    fallguy's point about grain density and the cut is also important. In the cabinet world, quarter-sawn is what you are most likely to find. It has less waste than riff-sawn.
    cutting patern.jpg
    Wood expands and contracts the most tangentially, next is radially and the least is longitudinally. This means that flat-sawn lumber tends to cup in the opposite direction of the rings while quarter-sawn lumber simply shrinks or expand with the moisture content.

    My suggestion, as a cabinet maker, not as a boat builder, is replace the knotty pieces. You will be happier with the results.

    -Will (Dragonfly)
     
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  9. BlueBell
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    BlueBell "Whatever..."

    I'm going to counter Will's suggestion because you've epoxied these pieces in place.
    Remove the entire piece but if it's already glued in, then I would only remove the knots.
    But scarf the new joints if possible.

    You are getting a pretty good education here!
     
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  10. mariobrothers88
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    mariobrothers88 Senior Member

    Thanks again to everyone for all the fantastic input!

    Per the advice of several members of this forum I am replacing the knotty sections of the Douglas Fir. When I removed the timbers, I found that the epoxy didn't really adhere well to the okoumi plywood. There were sections where the epoxy was well keyed into the marine plywood, but lots of sections where the epoxy didn't seem to have attached to the plywood at all and I could easily scrap it off (see photo and video). I mixed the epoxy with milled fiber. The pieces seem solidly attached to the plywood overall so maybe I am just being paranoid. One thing that I didn't do was that I didn't sand the okoumi plywood prior to putting the epoxy glue and timber frame- was this an error on my part? Should I have sanded the plywood first? If so, do I need to redo all the bulkheads that was glued to the timber without sanding?

    Video here:

    Thanks again to everyone for all the contributions it's greatly appreciated!!
     

    Attached Files:

  11. fallguy
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    fallguy Senior Member

    You are experiencing dry joint.

    unfortunately, I can see you did not precoat the wood and when you don't the wood sucks the epoxy into it's pores and creates a weak glue bond

    The right way to do it is to wet the wood with just epoxy and then wait for about an hour and then apply the glues. It takes some serious discipline and is easy to do wrong and skip.

    Milled fiber is the wrong filler, too.

    Milled fiber adds weight and body. Body is okay, but unneeded. In this case, the body retains the dimension while the unwetted plywood sucks the resins which amplified your joint failure.

    The best additive for gluing, in my opinion is fumed silica, or aerosil, or cabosil. The by volume amount is about 2:1, jelly to peanut butter consistency.

    Also, when gluing; wetting both sides is better than one, but if you prewet both sides as required; you can get away with a single side glue application. But, you must cover the entire glue surface. Not just here and there.

    And for typical bonding, I like a 1/16" v trowel. I trowel both sides and minor pressure equal to or less than 9" of mercury.
     
    Last edited: Nov 26, 2020
  12. fallguy
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    fallguy Senior Member

    Redo them all. They will probably break off fairly easily with screwdrivers and a chisel. Any minor damage to the plywood is repairable.

    You must not be too conservative in the use of epoxy, or you will experience issues.

    feel free to continue to contact me privately
     
    Last edited: Nov 26, 2020
  13. mariobrothers88
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    mariobrothers88 Senior Member

    Hi fallguy thanks so much for your advice I really appreciate it! I will suck it up and redo them all. When I asked Richard woods if I could use milled fiber he said that it would be fine to use, so I ordered a large amount of milled fiber. This is what Raka claims regarding milled fiber on the website:

    "Milled fiber A dense very high strength powdered fiberglass filler.. For high tensile strength putties and gap filling. Makes a very high strength rough mixture for extra strong bonds. "

    If I precoat the wood with epoxy, am I ok to use milled fiber?
     
  14. mariobrothers88
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    mariobrothers88 Senior Member

    Also do I have to wet both the okoumi plywood and douglas fir timbers prior to glueing? Or just the plywood?

    Thanks again for all your help!
     

  15. fallguy
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    fallguy Senior Member

    Wet all wood prior to bonding.

    Milled fiber has limited use in your build.

    I used milled fiber in a few locations in my build where I wanted strong fillers. The bottom of a transom in a power vessel for squaring back. Transistion areas where I went from core to solid glass.

    It is extremely heavy and I never use it 100%. I only use it 50/50 with fumed silica.
     
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