Bending Wood Ain't Easy!

Jerryc41

Jerryc41

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I must have spent an hour yesterday trying to bend one side for a uke. I got about halfway done, and I clamped it into a mold. I used one of those pricey electric bending irons, but that didn't make it easy. I kept the mahogany (from Stew-Mac) moist during the process. I have other things going on in my life, so I'll wait a few days before getting back to it.

Is there a desired temperature for the bending iron?

My hat's off to you guys who do this so well on a regular basis. When (if) I ever finish this uke, I think I'll sell the bending iron.
 
Jerry, don't get disheartened. Mahogany can be very difficult to bend, especially for a first time effort. Practice makes perfect, so try on the offcuts or scraps first, and next time try rosewood or walnut which are much easier. Some people say Cherry is easy, but I didn't find it easy at all. Watch all the Youtube videos you can, showing the process, if you haven't already. Another thing which Pete Howlett taught me was to bend the wood dry, and only spritz it with water if you're likely to scorch the wood, such as on the waist where you might spend a bit more time.
Best of luck, Mike.
 
mikeyb2 said:
Jerry, don't get disheartened. Mahogany can be very difficult to bend, especially for a first time effort. Practice makes perfect, so try on the offcuts or scraps first, and next time try rosewood or walnut which are much easier. Some people say Cherry is easy, but I didn't find it easy at all. Watch all the Youtube videos you can, showing the process, if you haven't already. Another thing which Pete Howlett taught me was to bend the wood dry, and only spritz it with water if you're likely to scorch the wood, such as on the waist where you might spend a bit more time.
Best of luck, Mike.
Click to expand...

Thanks. Yes, I watched all the YouTube videos, and it looks so easy. :D
 
Jerry, I'm beginning to think it's often not a predictable process. I've been communicating with a luthier recently as he was bending the sides on a build for me. His comment was "sometimes the magic doesn't happen and it breaks in half!"

So many variables involved.

Hopefully, things will go better when you get back to it.

Bluesy.
 
My first effort at instrument building was a mountain dulcimer in the early seventies. I knew nothing about bending wood. I built it out of a mahogany hollow core door and to bend the sides, I took my dad's radial arm saw and made kerfs about a 0.5 cm apart. The top was made from some 5 mm plywood that I bought in a hobby shop. It wasn't quite symmetrical, but if I squint when I look at it. . .
It's an instrument that I let kids play with. With the diatonic scale, they seem to learn tunes very quickly.
homemadedulcimer.jpg

I later (1978) started a guitar using the Irving Sloan book for instruction. I used Indian rosewood and put the sides in the bathtub with hot water to soak. I bent them on a piece of 3" copper pipe with a propane torch inside it. It worked much better than the kerfs. Unfortunately, I took the guitar out of the case to work on it and found that the rosewood had split from the lack of humidity. I put it back in the case and never worked on it again. I still have a partially finished guitar with "Jim Yates - 1978" written in the sound hole.
 
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Jim Yates said:
My first effort at instrument building was a mountain dulcimer in the early seventies. I knew nothing about bending wood. I built it out of a mahogany hollow core door and to bend the sides, I took my dad's radial arm saw and made kerfs about a 0.5 cm apart. The top was made from some 5 mm plywood that I bought in a hobby shop. It wasn't quite symmetrical, but if I squint when I look at it. . .
It's an instrument that I let kids play with. With the diatonic scale, they seem to learn tunes very quickly.
View attachment 134966

I later (1978) started a guitar using the Irving Sloan book for instruction. I used Indian rosewood and put the sides in the bathtub with hot water to soak. I bent them on a piece of 3" copper pipe with a propane torch inside it. It worked much better than the kerfs. Unfortunately, I took the guitar out of the case to work on it and found that the rosewood had split from the lack of humidity. I put it back in the case and never worked on it again. I still have a partially finished guitar with "Jim Yates - 1978" written in the sound hole.
Click to expand...

I bet wood for a uke based on a tennis racket, but that has fairly gently curves. I used a propane torch and a pipe for that. I'm hoping I don't break the wood.
 
How thick are your sides? Most bending irons for guitars don't have the ideal form for bending uke sides I find, better with a violin/viola model or one designed for a multitude of instruments. There is a knack to bending which is difficult to learn just from videos, you have to do lots of practice on scrap wood. Then you get a feel for the rocking motion to heat up the wood without scorching it and judging when to apply more pressure as you feel the wood 'let go'. Stick with it, but practice on lots of scrap wood. I would bend 5-10 sets of practice sets before doing the real thing for the first time.
 
I've hand bent over 1600 sides and yes, it is not easy AT FIRST, and I started out with curly koa! I use a guitar bending iron and do not 'rock' the sides on the iron but 'feed and bend' very slowly. Mahogany will take a slightly higher temperature than koa before scorching and rosewood even higher - you must work just below this point which is why you need an Ibex style iron with thermal control. Don't use ribs thicker than 1.8mm or 0.070". Use a 20 thou piece of shim stock to support the wood that is opposite to the heat and you will be fine.
 
Pete Howlett said:
I've hand bent over 1600 sides and yes, it is not easy AT FIRST, and I started out with curly koa! I use a guitar bending iron and do not 'rock' the sides on the iron but 'feed and bend' very slowly. Mahogany will take a slightly higher temperature than koa before scorching and rosewood even higher - you must work just below this point which is why you need an Ibex style iron with thermal control. Don't use ribs thicker than 1.8mm or 0.070". Use a 20 thou piece of shim stock to support the wood that is opposite to the heat and you will be fine.
Click to expand...

According to Stew-Mac, the wood is 3/32" (2.38mm).

Thanks.
 
Pete Howlett said:
I've hand bent over 1600 sides and yes, it is not easy AT FIRST, and I started out with curly koa! I use a guitar bending iron and do not 'rock' the sides on the iron but 'feed and bend' very slowly. Mahogany will take a slightly higher temperature than koa before scorching and rosewood even higher - you must work just below this point which is why you need an Ibex style iron with thermal control. Don't use ribs thicker than 1.8mm or 0.070". Use a 20 thou piece of shim stock to support the wood that is opposite to the heat and you will be fine.
Click to expand...

According to Stew-Mac, the wood is 3/32" (2.38mm). If I had lots of scrap wood, I would practice lots. I'm not going to buy it just for practice. I'll just go slowly and hope for the best. A lot of my success is the result of hoping. :D
 
The thickness makes a massive difference to the ease of bending. Take Pete's advice and get the sides down to 1.8mm and certainly no more than 2.0mm.
 
That is WAY too thick for uke sides. You should be bending at 1.8mm at most for a tenor size instrument. Often I go down to 1.6 - 1.7mm thick. It will make a world of difference on how successful / easy timber is to bend.
 
Allen said:
That is WAY too thick for uke sides. You should be bending at 1.8mm at most for a tenor size instrument. Often I go down to 1.6 - 1.7mm thick. It will make a world of difference on how successful / easy timber is to bend.
Click to expand...
Yes 1.6 mm = approx 1/16" in mahogany, just right for sopranos .. :)
 
Pegasus Guitars said:
Follow Pete's advice and thin the wood. Your wood is way to thick. --Bob
Click to expand...

Thanks! Now I have an excuse to buy a $600 tool! :D

I got one side bent, and I have it clamped into the mold. I'll sand the other side thinner, trying to keep it uniform. Having sides with different thicknesses should be interesting. : )
 
For the hobby builder with a rise and fall table drill press you can make an accurate sander for 5 bucks - take over Ken....

BTW an idea used by South American builders and used by me for my first 400 instruments.
 
+1 to everything most people have said so far; 3/32" is way way too thick for ukuleles, I think I usually went to around 60 thou (1.5mm). Temperature wise I set my bending iron to 165 degrees Celsius, you know its ready when you splash water on it and the water forms little balls that skate around on the surface for a few seconds.
 
You know it's ready when you canaan bend the would with moderate success. Temperatures are really very arbitrary.
 
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