Official Luthiers Forum!

I have a question about bending my curly koa bindings in a bender. I have a special bender I made just for the cutaway section of my sides and bindings. Here's a photo:

I have successfully bent the non-cutaway side bindings. But when I did the cutaway side bindings, I ended up with some scorching (even though I had wrapped the bindings in the dampened kraft paper/foil, just as I did my sides) and a small partial crack in the lower part of the horn. The crack, I'm pretty sure, might have been due to my cranking the left-hand part of the bender a little too soon or too quickly. (Or could the moisture have had anything to do with it?)

What I'm wondering is, should I bend the bindings dry instead? If so, how should I wrap it? And, does it need less heat/shorter cooking time than the sides did?

Any tips would be greatly appreciated!!! (By the way, I just tried bending a piece of scrap koa binding by hand on my electric bender, but still can't bend the sharp cutaway horn without it cracking at the tip.)

_________________
Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Hi Kathy. I wanted to bump this thread for you so we can get you some answers here.

My second guitar was a cut-away and I used highly flamed Koa and bent it on a pipe. It was VERY frustrating and I probably broke 4 bindings until I got one right. I remember having a tendency to try using more water and that just seemed to make the fibers delaminate from each other and the wood would fold into a damp mess..... So I think that minimal water is important but I don't have a good answer for you and hopefully someone else will.

I just bent 5 sets of highly flamed koa binding and not a problem. I do wet it a little more than some others. I don't use a thermometer for temp stuff, but set it on about 7 minutes znd let it cool. I have broken koa and imbua binding on occasion in the past and it was from letting the waist or the horn up first instead of the bouts. But normal for us is upper bout, loosen lower bout, raise the waist and then take off both bouts. I was finding doing waist first caused lot of pressure on the upper bout tighter bends.

I have yet to build my cutaway mold, so, suffice to say, one of the issues that keeps coming in my thought process is bending around the tight curve. A 1" radius for Tenor `ukulele doesn't sound like fun in a mold, but neither is it free hand, which is what I did.

Maybe you could try prebending the cutaway section first on a pipe before final bending in the mold. Here is where I get lazy - I wasn't about to buy a pipe, and I didn't feel like building one with a torch (which I have). So, I just bought a small section of 1" galvanized threaded pipe, and a base flange - screwed the flange into the side of the bench (and left it there). I screw in the the threaded pipe for use, lay my heating blanket over it, and bend away free hand. No wrap, just a quick running water soak (spray bottle handy) and off I go.

Kathy I can second the use of SuperSoft II, wet the bindings with it, just spray them till wet, and leave them to dry for 24 hours before bending. Also use it for any high figure/curl sides or when bending ordinary wood into a tight radius. I am now in the habit of using it on the waist of evreything I bend, just as insurance against bad workmanship.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

just bent a set of curly koa bindings. not a tight back and forth bend like your cutaway, but my OM has a pretty tight waist and i didn't have any problems. all due to the super soft i think. brilliant stuff. i let it dry for a day, then gave the bindings a light misting of water, put them into parchment paper along with the purflings, and kept the heat around 300. heaviest curling was not in the tightest part of the bend so that also helped i'm sure. order the $25 spray bottle. it'll pay for itself in two guitars worth of curly bindings.
phil

love the hinged bending form

THANKS, all who responded to my plea!!! All your suggestions and tips are greatly appreciated!!!

Hesh: Thanks for your quick response! The tip about the amount of water is something I considered, too. But I get confused...sometimes I've read things that said to use minimal (or no) water with flamed wood, but then others say they use normal amounts of water....

Todd, Colin, Phil: I didn't know about SuperSoft (where does one get it?), so that will be something to consider for the future!!! What, exactly, does it do? (Does it just make the wood more pliable?)

Todd: Thanks for the tip about the crushing — unfortunately, I read your response too late!!! (I had already bent my second set of bindings, and did end up with a tiny section that had compressed —until I read your response, I had no idea why it had done that!) Duh. Makes perfect sense. I had just put the two pieces of binding in the bender, not realizing it needed that support. Well, now I know! (I managed to fix the compressed section, though, with a little travel iron and a wet towel, to steam it out.)

Stan: Thanks for your tip about water being okay....I did end up still using water. But I also used some thicker kraft paper than I had originally used. Thanks also for your tip about being careful on removing the bindings carefully! Good tip.

Aaron: That's a great idea about using a heating blanket over a pipe! I have an electric bending iron, though, so don't need that. (But if I didn't have one, your idea would be a good one to use!) I did try (several times) bending the cutaway horn by hand, but I just can't seem to do it without it cracking!!! Maybe it just takes more practice....

Phil: I can't take credit for the hinged bender...I saw it somewhere on this forum a while ago...."Mandomaniac" had a photo of one he used with a heating blanket.... So far, it's the only way I've been able to bend this sharp cutaway!!!

ANYWAY.....I ended up doing a few things differently yesterday when I bent my second set of bindings. I put the spring steel (and not the heating blanket) directly on top of the binding sandwich (moistened heavier kraft paper, foil), and the heating blanket on top of the spring steel. I didn't let it get as hot as I had the previous day. I didn't crank the clamps down as quickly or as soon as I had the previous day; I took it more slowly. It came out with no scorching and no cracks!!!! (The only thing that happened was a little section where it was compressed...see note to Todd up above.)
I'm a happy camper now.

Thanks again for all your tips!!!! It will definitely help me in the future!!

_________________
Kathy Matsushita
San Jose, CA USA
http://theamateurluthier.com
Facebook: https://www.facebook.com/kathy.matsushita

Just a little warning about SuperSoft. I have used it to bend some high curl Koa sides and to my surprise there was a huge amount of orange color stain on the kraft paper I used on the sides. After close inspection I noticed that the sides had bled almost all their color and it was almost as white as maple! I ended up having to get a new set of sides because it did not match at all with the backs nor did it look like Koa anymore. I will use Supersoft on some woods but NEVER on Koa. If you want to try it, I suggest try it first on scrap wood.

Good luck,

_________________
Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I'm happy to hear you got your bindings bent Kathy so perhaps you won't mind if I hi-jack this thread a bit.

I too am a fan of SuperSoft II and I now won't bend sides without it. My question is, why are people waiting 24 hours after wetting the wood with it to do the bending? From what I've read and from what their video shows (the one where they wrap some veneer around a pencil) it looks to me that the stuff works right away. If I remember correctly, they said the wood stays more flexible up to around 48 hours after being wetted with SuperSoft II, but I don't recall anything suggesting that it needs time to work. I did some comparison bending with and without SuperSoft and the stuff does make a difference and it does seem to work immediately. Have I missed some information some where?

Pat

_________________
There are three kinds of people:

Those that make things happen,
those that watch things happen,
and those that wondered what happened.