Epoxy over wood glue for a fillet?

Discussion in 'Beginners & Educational Programs' started by MichaelRapp, Jan 20, 2020.

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  1. Jan 20, 2020 #1

    MichaelRapp

    MichaelRapp

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    Oopsie. I was intending to try using five-minute epoxy for fillets instead of wood glue on my current rocket, but I wasn't thinking and before I knew it, I had run beads of wood glue down each fin.

    Now, this is just a single application of wood glue, so it should shrink significantly as it dries. (I didn't catch what I had done until the glue was too tacky to wipe off.) Is there any issue with applying the epoxy over these wood glue fillets? I can't imagine there would be, but I've only used epoxy for couplers and motor mounts thus far.

    (I've got two other rockets, one with wood glue for the fillets and the other with Fix-It Epoxy. My plan is to do this one with five-minute epoxy so I can compare all three after painting and see which method I like best.)
     
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  2. Jan 20, 2020 #2

    rharshberger

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    Let the wood glue cure fully, up to about a week if need be, then epoxy over the top is okay. Wood glue cures by the water drying out of the glue, if it gets sealed in too soon by the epoxy the wood glue will never or very slowly cure.
     
  3. Jan 20, 2020 #3

    David Schwantz

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    Rich is right about the water. But before using the epoxy be sure to prep your surface by sanding the wood glue fillet. This will give the epoxy a much better surface to adhere to.
     
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  4. Jan 20, 2020 #4

    Nytrunner

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    And there's always Titebond Quick & Thick that doesn't sag as much if you want to stick with the same type of glue that's already on it!
     
  5. Jan 20, 2020 #5

    MichaelRapp

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    Thanks for the advice about letting the wood glue sit for several days. That makes perfect sense, but I never would have clued into that. It probably also stands to reasons that one should have several days between gluing the fins on and applying the epoxy as well.
     
  6. Jan 20, 2020 #6

    MichaelRapp

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    I know many people have had great results with this, but I tried it once and my results were poor.

    However, several things may have gone wrong. I had to order a bottle off of Amazon, and while the code on the bottle did not indicate it was old, that stuff was REALLY thick, almost like really thick caulk or putty, and was very difficult to push out of the bottle. (I wonder if the bottle had been stored improperly in a warehouse?)

    A few months ago I remember trying to revisit it and watched a few furniture videos in which that glue is used. It seems much less viscous in the videos than I remembered it, so there may have been something wrong with my bottle. I've also since learned that using a wet finger -- water or alcohol -- can really help smooth it out.

    Or maybe in my inexperience I simply put too much on, as I am apt to do. :D

    None of my local stores carry it, and it's $13 for a 16 oz bottle on Amazon.
     
  7. Jan 20, 2020 #7

    AfterBurners

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    If you ever want a bottle let me know. I can pick up for you and ship it out. $13 dollars? wow!!
     
  8. Jan 20, 2020 #8

    MichaelRapp

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    ... and don't forget the five pack for $130. :)

    Screen Shot 2020-01-20 at 2.51.23 PM.png
     
  9. Jan 21, 2020 #9

    AfterBurners

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    You know what I can't even find this stuff at the hardware stores in my area. WTH? Did they discontinue it this product? I thought it was readily available?? Sorry Michael I thought I could just get it at my local hardware store. Guess I was wrong. So many great products that seem to get discontinued only to be replaced by lesser quality products
     
  10. Jan 21, 2020 #10

    solid_fuel

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    never mind.
     
  11. Jan 22, 2020 #11

    Nytrunner

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    Goes by Quick and Thick. Try Lowes
     
  12. Jan 22, 2020 #12

    neil_w

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    What rocket? If it's LPR, why epoxy fillets? Adds a lot of weight to the tail.

    As far as using Quick and Thick for fillets, this might be helpful: https://www.rocketryforum.com/threads/doing-fillets-with-titebond-quick-and-thick.148632/
     
  13. Jan 22, 2020 #13

    DAllen

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    I am currently working on my L3 and plan on laying epoxy over the wood glue myself - at least thats the current plan. Which epoxy you use is a personal preference item since it seems there are a lot on the market that would probably work well. I like RocketPoxy myself. The thick Titebond stuff is great as well but is subject to a little bit of shrinkage I have found. Not a big deal but something to be aware of and it does seem to stick a little better to where it is applied rather than the regular Titebond. RocketPoxy on the other hand (as with most epoxies) does not shrink at all and seems to be better at holding a good fillet shape than the wood glues. Not that one is better than the other in this case - just what would you prefer to work with...

    Rich and Dave in this thread are definitely spot on with their advice.
     
  14. Jan 22, 2020 #14

    Greg Furtman

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    WEST System 105 with waterver speed hardener you chose. The additive 406 Colloidal Silica thickes it up & is very strong. If you need less weight use the 410 Microlight. About 30 years ago I built myself a 15' redwood strip solo canoe. After glassing the outside with fiberglass & 105 I started on the interior. In order to achive a sharp/fine entry line on the bow I didn't have a wood stem. Instead I stood the canoe on its nose, mixed up a large batch of 105, after mixing I stirred in a bunch of 410 untill it got to the viscosity I wanted and then poured into the bow. It is still holding strong. :)
     
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  15. Jan 22, 2020 #15

    David Schwantz

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    Hey Greg, my son and I built this one with West 105 also. He was 4 yo when we started it, he is now 30. I think the West holds up very well to use. I gather from what you said, you must have had a mold or form for the bow. After your pouring and setup, was it then removed? As you can see I brought the cedar strips to a point and used them with 4 layers of cloth over it. I also left the interior with the weave for a finish, gives it a bit of grip when all is wet. You can see some scratches, but none have gone through the resin and cloth.
     

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  16. Jan 22, 2020 #16

    MichaelRapp

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    Thanks all....it does indeed look like Quick and Thick is a separate product from Molding & Trim/No Run No Drip glue. But as you pointed out, I can get Quick and Thick from Lowes for $4! :)
     
  17. Jan 22, 2020 #17

    MichaelRapp

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    Oh as far are why for a LPR? Practice mainly and just to see how to compares to wood glue and Fix-It epoxy.
     
  18. Jan 22, 2020 #18

    neil_w

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    Although they are both for sale there is no apparent difference between them in use. Quick and Thick is most readily available for purchase.
     
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  19. Jan 22, 2020 #19

    Greg Furtman

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    David, nice looking canoe! My bow & stern aren't as curved as yours so I have more of a straight area there. After & glasses the outside & the epoxy had set up I then basically stood my canoe on it's nose, mixed up 105 with some slow hardener, mixed microballoons into it untill I got a thick but still pourable mixture. Then I poured it into the bow & let it set up. I then put a layer of fiberglass & epoxy over it and maybe 2" beyond it to bond both sides together. Did the same process for the stern. Since WEST microballoons are tan it blends into the wood well. And it has held up very well. :)
     
  20. Jan 22, 2020 #20

    David Schwantz

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    Greg, thanks. Love to see yours if you have any pics. Please feel free to PM me so as not to steal the thread away, Dave.
     
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