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Adhesive For Inside Rail Scarf Joints?

Discussion in 'Wood and Canvas' started by MGC, Jan 21, 2019.

  1. MGC

    MGC Paddlephile

    I've made a 30 inch cherry inside rail section to splice into a boat I am currently rebuilding. I had planned to replace the entire rail but when I couldn't get the require length of cherry I decided to splice in the missing section. Worst case (if I don't like the result) I'll tear it out and go back to plan A, replacing the whole thing.

    My question is what adhesive you would use for this? Ordinarily I use Gflex for stem tip repairs and Titebond 3 for everything else..such as rail tip repairs.
    This section happens to be behind the bow seat and will be drilled to accept a thwart. I have cut 9 inch scarf joints and pre-bent the section to match the boats fits nicely and should glue in perfectly. I may poke a few dowels in strategic spots once the wood is attached.

    Should I go ahead and use the Titebond or should I use the Gflex ? Should I use something else (what)?

    I'm open to and interested in advice...this is the first time I've spliced into the middle of a rail so I'm not sure if I should treat this differently than a tip replacement.
  2. Dave Osborn

    Dave Osborn LIFE MEMBER

    Mike, I’ve never scarfed cherry inwales, but I have scarfed mahogany, oak, ash, spruce, and walnut inwales.
    I’ve always used G-Flex and had no failures.
    With cherry being fairly dense, I’d coat both sides with G-Flex and let them sit for a half an hour to allow it to soak in before clamping.
  3. Just1moredave

    Just1moredave Enthusiastic about Wooden Canoes

    Titebond 3 doesn't fill gaps and epoxy does. I don't think I could get a gap-free cut if the inwale was still on the canoe so I would choose epoxy then. But it sounds like your inwale is not installed.
  4. Dan Lindberg

    Dan Lindberg Ex Wood Hoarder

    For those who don't know (me) G-Flex is West Sys epoxy.
  5. pklonowski

    pklonowski Unrepentant Canoeist

    I use epoxies for scarf joints, not too picky about which type. G-Flex is a quite good option, but I've used hardware-store variety epoxy, and not had any issues. TB3 should work fine as well, though I've not actually used it for challenging aquatic condensations..
  6. Andre Cloutier

    Andre Cloutier Firestarter. Wicked Firestarter.

    Mike, where is the section in the overall boat? are you able to keep the sweep (wherever it is) along the rail with a short, strong piece? Ive always used epoxy and cabosil for scarphs and gunwale splices, i dont find it starves into the grain. 'course you want to carefully wipe off the sqeeze out... Just pony up for some long cherry, will ya?
  7. OP

    MGC Paddlephile

    All...good feedback and helpful. I think the joints are pretty tight on both sides of this piece but given that I can't see inside the fit, the G-Flex makes the most will fill voids and it gives plenty of working time. The suggestion to let it sit for a while before assembling is the voice of an experienced user....

    Andre, I hear you plan was to replace both rails...but I figured I'd give this a shot and see how it comes out. I was able to match up the rail pretty well...I made a template off of the opposite side rail and pre-bent this piece on a form.. Fitted, it looks like the boat will have it's lines. I may glue it in today after I shovel the roof....

    I have G-Flex on the shelf in my shop...I keep it handy..I've even used it to repair my hunting boots...wicked good stuff with a nice cure time and tough as nails when it sets up. It's not brittle like many typical epoxy products..
  8. Howie

    Howie Wooden Canoe Maniac

    For what it's worth, I've always used TB-2 or TB-3. The secret is to smear on a thin coat & let it dry for maybe 15 minutes, then refresh with new glue if needed & clamp pieces together for 24 hours. If you don't let it dry a little first then you just squeeze all the glue out when you clamp the pieces together. Also: abrade the wood at the joint (make a ton of slits using a knife) - the rougher the better. Avoid using sand paper to rough up the joint areas though - you'll end up making the pieces less flat & not fit together as well.

    BTW... people say that TB doesn't fill... Clearly it does to some extent - just drop a spot of glue on some scrap wood & see how tall it is when it dries! Yeah... I know, it does shrink when it dries, but still!

    I've never used G-Flex... Say... I've got an upcoming situation with a 'blown-out' c-sunk screw hole in an inner rail. This is a screw that secures the rail to the leading edge of a deck, so it needs to hold well. Do you think G-Flex would have enough 'fill' ability to hold the screw head? That is, could I clamp a piece of scrap wood & wax paper on one side of the hole and from the other side fill the whole area with G-Flex? I assume G-Flex can be drilled into when dry... Should I also mix in some wood dust with the epoxy? Or would I do better to drill out this 'blown-out" screw hole, plug it with a wooden dowel (using either TB or G-Flex), then drill a new c-sunk hole for the screw?

    And another question: which penetrates into wood better: epoxy?, or a water based glue (I assume since TB cleans up with water it's water based)? I'm thinking the latter... though I guess penetration doesn't necessarily equate to strength.

    I always think of these things in the winter when it's too cold outside to work on the canoes...
  9. OP

    MGC Paddlephile

    There you are...I should have called you. You just did a similar scarf in a recent restoration if I recall correctly.
    I normally use TB3 when I splice in rail tips. G-Flex on stems and in this case, an inside rail section. I removed the clamps this morning and cleaned things up a bit. It looks pretty good so I'll keep going.
    I use G-Flex in thwart holes so I presume you could use it as you described. I'd be more inclined to fill it with wood though, using G-Flex to bond it.
    It's a bit pricey but a little goes a long way. You'll be looking for things to use it on. I repaired a pair of hunting boots and a pair of kickaround shoes when I glued the scarf.
    G-Flex does very little penetrating so surface prep is important. Since it's slow setting you will have time to remove/trim any overflow with a knife.
    West Marine up by the'll need scimp on meals for a few weeks.
    Last edited: Jan 24, 2019
  10. mccloud

    mccloud Wooden Canoe Maniac

    G-Flex is much more viscous than West 105/206, so will not penetrate much. These two resins can be mixed to get a resin with intermediate properties. Both resins are hard & strong. If you are concerned about the color of the resin after it has set, mix fine sanding dust (dark) and microlite filler (light) to get the color you want. Similar to what you said above RE: Tightbond, if I were doing the job you are, I would mix the resin, then thin a small portion of it with ~20% acetone and paint that around the hole, maybe more than once depending on how quickly it gets sucked in. Let it sink in, penetrate, and partly set - maybe 20 minutes, then fill with full strength resin & dust. Tom McCloud
    MGC likes this.
  11. Howie

    Howie Wooden Canoe Maniac

    Thanks Tom & Mike... But after G-Flex sets, ie gets hard, how easily can I drill a c-sink or clearance hole into it? And are there any precautions involved in drilling?.. like use a sharp or dull drill.

    And yes Mike, I've never had a canoe where I didn't have to make at least one scarf cut repair job. Remember - I'm cheap, so I get cast-offs!
  12. mccloud

    mccloud Wooden Canoe Maniac

    I wouldn't expect any trouble with drilling unless you are using a large bit, in which case the resin might break out in large hunks. If I've filled, for example, a seat bolt hole thru the inwale where I can see a little rot and/or cracking, I put tape over the bottom of the hole, then use the method described above, i.e. thinned resin first, then fill with non-thin with dust. After it has hardened, I will go thru the resin plug with 1/16, then 1/8 drill bits, then the size I need for the bolt, and have never had to repeat the repair. I recently did exactly this on 10 inwale holes on an Old Town which had bolts recessed in the inwale, and I wanted to stabilize the wood around the old holes, plus provide a hard base for the new bolt to sit on. Worked fine. TM...
  13. Howie

    Howie Wooden Canoe Maniac

    Excellent. Thanks guys.
  14. OP

    MGC Paddlephile

    Frugal....I don't find you to be cheap....
    Last edited: Jan 25, 2019
  15. Howie

    Howie Wooden Canoe Maniac

    Tom - I was just remembering your advice above about thinning the epoxy with acetone to cut its viscosity, then 'painting' it inside the hole to ensure better penetration. That's a great tip - thanks. But why let the thin stuff dry first? Why not cram in a wad of a thicker epoxy mix into the hole after painting with the thinner stuff? Wouldn't that better ensure there were no voids? I wouldn't think drying time would be affected. Ya know, I could also press in a cup washer - the kind we use for keel screws - into the epoxy to form a permanent seat for the flat-head screw, then feed a wooden dowel through the washer that could be easily drilled out later.
  16. mccloud

    mccloud Wooden Canoe Maniac

    Opinion: The less viscous acetone will 'carry' some of the thicker epoxy with it into crevasses, pores, cracks, but some of the epoxy is always left behind on the surface. That's why I suggested two applications of the thinned epoxy if you see it vanish quickly into punky wood. The second application will, in part, wash in, carrying some epoxy with it. West 105/206 is thin enough to flow into larger cracks - but I can imagine that tiny pockets of air get trapped as it goes in. But wood is full of air pockets. Acetone is volatile and flammable enough so it evaporates quickly, and don't be smoking while you use it. I doubt putting in the thick epoxy quickly will hurt the strength of the bond, but doing that removes the option of washing epoxy further into the wood if it looks like it needs it. And by the way, I did drop brass washers into the bolt holes in the inwales, which now sit on top of a hard epoxy base in the old and very dry spruce. TM...
  17. Dan Lindberg

    Dan Lindberg Ex Wood Hoarder

    Or you could just use CPES or one of the knockoffs.
  18. Canoeal

    Canoeal Canoe/kayak builder/resto

    I always scarf with epoxy...clear from the mix first, five minutes to soak in, then thickened like peanut butter with the appropriate colored wood sanding dust...them clamp it to heck. Never had an issue...

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