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Thread: Help me fix my cracked side.

  1. #1
    Join Date
    Apr 2009
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    Morgan Hill Ca
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    Default Help me fix my cracked side.

    I learned a lesson the other day. (Take my time)!
    I got in a hurry and began bending the side of my koa build. Its a concert and the jig is heated with light bulbs. Im on number 12 bending that way and it has always worked for me till now. I didnt soak the side in water long enough and while bending it cracked.
    It cracked on the bottom bend. So I glued it back up with titebond glue. Clamped it between two straight boards. After it dried ya cant even see the crack. So I then wet the side again and put it back in the mold. While bending the bottom it cracked again!!

    I have glued it again and again you cant tell. Im going to try to soak and bend it again unless someone can give me a secret on bending it when I get to the weak glued part. Or maybe something better to glue it with?

    Just frustrated.

    Thanks

    Dano
    zenking12@yahoo.com
    Kala Maple & Spruce tenor
    1927 Gibson soprano
    Martin 000-RSGT
    Martin OOOX1AE
    fender American strat
    Gibson Les Paul

  2. #2
    Join Date
    Mar 2008
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    Cottage Grove Oregon
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    728

    Default

    Is it possible to glue it after you finish bending it?

  3. #3
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    Default

    Tattwo, I cant do that because when it cracks it looses the round curve. Its like it snaps in half but not completly in two parts. When I try bending that part is the weakest.
    zenking12@yahoo.com
    Kala Maple & Spruce tenor
    1927 Gibson soprano
    Martin 000-RSGT
    Martin OOOX1AE
    fender American strat
    Gibson Les Paul

  4. #4
    Join Date
    May 2008
    Location
    Columbus, OH
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    788

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    How about sanding it much thinner, then bending it and a back-up piece of something cheaper & laminating them together? (I'm assuming that you've only got the one piece of nice koa (?).)

  5. #5
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    Default

    Dave I have thought of that. Do you think it will work?
    Yes I only have the two halves of koa. Id like to make it work so they stay book matched if possible.
    What if I put thin laminate on both bottom and top of the koa side and tried bending it. Would the two pieces prevent the middle piece from breaking? If it would then I could just take the laminate pieces out after.
    zenking12@yahoo.com
    Kala Maple & Spruce tenor
    1927 Gibson soprano
    Martin 000-RSGT
    Martin OOOX1AE
    fender American strat
    Gibson Les Paul

  6. #6
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    Default

    The thing about bending with light bulbs as a heat source is that your wood doesn't get hot until it actually makes contact with the bending for. With blankets, you are heating the wood even before you start the bend. I go as far as using two heat blankets, one on each side of the wood, but that is a little extreme as I am often bending some very difficult wood.
    I bend between two slats of spring steel with good success. I use just enough water to create a little steam when the side is heated. From my experience with curly koa, soaking to wood in water for any length of time only makes the wood weaker. I also try to use a lot of pressure when bending. Look at the Taylor videos. They uses tons of pressure and no water.
    If I were you I would rebend it as best I could, crack and all, then clamp the sides into the mold, spray it down with water and let it sit until it dries. Then flood the crack with CA. You'll probably still see the crack though and will also probably have a kink there. No matter how many times you've bent sides, this stuff occasionally happens, sometimes for no apparent reason.
    I sometimes use Super Soft II for difficult bends. I don't know if it really helps or simply that I pay better attention when I use it.
    Last edited by Moore Bettah Ukuleles; 05-11-2011 at 07:28 AM.
    Chuck Moore
    Moore Bettah Ukuleles
    http://www.moorebettahukes.com

  7. #7
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    Hey Dan, as one who has cracked his share of sides, I feel your pain, and I admire your intention to learn from the experience. That said, I think there are a number of things you need to learn. Number one, the properties of Titebond glue, you have been chasing your tail. We use Titebond because it releases with heat and moisture, so we can repair the instrument later. You can not put a repaired glue joint in a side bender and expect the glue to hold, as you have seen. Number two, soaking koa before bending is a bad idea. Chuck Moore, who has some experience with this, says soaking curly koa before bending it is a good way to wind up with a pile of potato chips. He places his sides in a wet canvas sleeve and then uses the side bender. I bend by hand and use a spray bottle to dampen the side right before bending. The only way I know of to effectively glue this back together, is to bend the side first and then glue it. In this case, you probably need to finish the bend by hand. Unfortunately, you attempted the repair with Titebond. Once a Titebond glue joint fails, you need to clean out all of the old glue before regluing, and that is probably impossible in this case. Here is how I would attempt to repair this. First, finish the bend by hand, it does not need to be perfect, just close. Put the side in a mold and use CA glue in the crack. Once this has dried, reinforce the inside of the cracked area with a thin piece of veneer glued over the crack with the veneer grain 90 degrees from the side grain. You can add a piece of veneer on the other side for symetry. Hope this helps.
    Brad

  8. #8
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    Those are good tips Brad. I'll sometimes bend an area on the hot pipe if I need more control. I found a tip that works great for me when doing so. I'll take a small square of rag (a face towel or a sock works great) and soak it in water and place it on top of the hot pipe and bend on top of the wet rag. It releases at lot of steam and heat. Watch your hands though, it really gets HOT! Keep spraying the rag down with water as it dries out. The usual fire disclaimers apply......
    Chuck Moore
    Moore Bettah Ukuleles
    http://www.moorebettahukes.com

  9. #9
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    Apr 2009
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    Well, I tried messing with it again and it keeps breaking. Wish I would have taken my time in the first place. Next time I will take the suggestions given to me by you guys the more experienced builders.
    I will let ya know what I end up doing.
    Dano
    zenking12@yahoo.com
    Kala Maple & Spruce tenor
    1927 Gibson soprano
    Martin 000-RSGT
    Martin OOOX1AE
    fender American strat
    Gibson Les Paul

  10. #10
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    Jul 2009
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    UK
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    Default

    Just a thought (never tried this but it might work):

    Glue a slice of something thin (veneer perhaps?) on either side of the piece, extending 3 or 4 inches beyond the break, using your Titebond (or hide glue for preference if you have any). Grain should run along the side, not across. Then bend over a hot pipe. The Titebond will probably release at the bend but should stay attached at either end of the veneer. This might be enough reinforcement to allow your side to be bent, or at least to get the bend started. If it works, you could complete the bend in your bending jig.

    Then remove the veneers (perhaps putting the side in your bender to heat the full length?). Repair the crack (probably reinforcing on the inside) and clean up glue residue.

    Would this be too thick to bend? 0.6mm veneer either side would increase the thickness by 1.2mm so it would be hard work. But I can't see this doing any harm.

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