Questions on Macassar Ebony

[Ron Daves]

I've started to build a Concert Uke. I thinned all the lumber (with a radial arm saw/Wagner Safety planer) to 3/32” as specified in the plans I’m using. I then started to bend the Macassar Ebony sides using bending jig and a heating blanket. I don’t remember where I got the blanket, so can’t provide specifics other than it is 4” X 36” and takes about 12-minutes to heat up to 310-degrees. I used a sandwich of .010” sheet metal/side wood/sheet metal/blanket on top. I spritzed the wood before making the sandwich.
Possibly, the wood was too thick and I rushed the bending process. Bottom line, I cracked both sides beyond repair. I had enough lumber to make two more sides, but have questions.
I’m now thinning these sides to .085” using a smoothing plane (Radial saw not available).
Questions:
1.) Dimensioning one of the sides to .085 with a Dunlap smoothing plane took about 2-hours. I've done a lot of sharpening, so get my plane iron pretty darned sharp. Anyway, I had to sharpen the plane 3-times during the process. Should it take this long?
2.) In my inexperience, have I chosen to bend a difficult wood?
3.) Is .085” thin enough?
4.) How long should I let the heat blanket warm up and at what temperature should I start bending? I started at about 265-degrees on the sides that I broke.
5.) The upper bout bend is pretty tight. Any tips?
6.) I’m including a picture of my bending jig. My vision is to bend the lower bout first, then the upper using gloved hands and to secure the sides loosely with a cam clamp, then to screw down the waste clamp and finish tightening everything.

Side Bending Jig.JPG (13.1 KiB) Viewed 9869 times

[Michael Lewis]

Ron, put the blanket under the wood (on the inside). I found a fairly easy method of bending with a blanket but it is a little fiddly. I make a "sandwich' of the metal, blanket, wood (spritzed), and outer metal. I use a layer of toilet paper to wrap the wood, spritz the wood and wrap it in a piece of aluminum foil, and leave the ends open like a flattened tube. I use small spring clamps to hold the whole thing together while it heats, and watch for steam escaping at the ends. When you see the steam (actually it's condensation) the wood should be about ready to bend. I generally give it a minute or so of making steam and then begin the bend. Waist first and gently bring the ends down to the form and clamp them there. When the wood runs out of water the steam stops, and it is about time to turn off the blanket or you risk scorching the wood.

The TP helps hold moisture for the bending process and to prevent the wood and metal from contacting each other, as sometimes the metal will discolor the wood. I'm not sure you would have any way of knowing with ebony but lighter woods can get bluish gray spots and streaks.

This method assures even heat to every part of the wood and pretty well eliminates scorching. Like anything else, practice makes perfect.

[Clay Schaeffer]

For a concert uke I would be inclined to make ebony sides a little thinner (.070) and possibly use side reinforcements.Some of the old rosewood parlor guitars I've worked on have sides this thin and have held up fine.

[Ron Daves]

Thanks Michael I'll follow your suggestions.

Thanks also, Clay. Yesterday, I went to the Resort's shop and hooked up a radial arm saw/Wagner Safety planer and thinned the sides to .085, but can easily go after them with a smoothing plane to get them to .070. I'm a little reluctant to thin any more with the Wagner, as the Radial saw's height adjustment isn't as accurate as it needs to be.
Haven't done any bending on this second go, yet. Been avoiding the experience. Tomorrow, I'll bite the bullet and proceed.

[Ron Daves]

Another question: In the guitars I've built (two of them), I used a natural wood filler. I'm thinking that I need something darker for the Macassar Ebony. Suggestions?

[Ron Daves]

Ron, put the blanket under the wood (on the inside). I found a fairly easy method of bending with a blanket but it is a little fiddly. I make a "sandwich' of the metal, blanket, wood (spritzed), and outer metal. I use a layer of toilet paper to wrap the wood, spritz the wood and wrap it in a piece of aluminum foil, and leave the ends open like a flattened tube. I use small spring clamps to hold the whole thing together while it heats, and watch for steam escaping at the ends. When you see the steam (actually it's condensation) the wood should be about ready to bend. I generally give it a minute or so of making steam and then begin the bend. Waist first and gently bring the ends down to the form and clamp them there. When the wood runs out of water the steam stops, and it is about time to turn off the blanket or you risk scorching the wood.

The TP helps hold moisture for the bending process and to prevent the wood and metal from contacting each other, as sometimes the metal will discolor the wood. I'm not sure you would have any way of knowing with ebony but lighter woods can get bluish gray spots and streaks.

This method assures even heat to every part of the wood and pretty well eliminates scorching. Like anything else, practice makes perfect.

Followed above instructions on some test strips of aromatic cedar thinned to .070. Broke first test. On second test, waited for blanket to reach 300-degrees before proceeding. Broke it, also. Perhaps aromatic cedar is the wrong stuff to do testing on. Will try something else. Feeling a little dumb. Appreciate input

[Ron Daves]

I suppose there are questions as to why I tried to bend aromatic cedar. Well, it was a piece of wood that I found up in the rafters of my shed. It was the right size and, without thinking, I proceeded to thin and attempt to bend it. I little common sense would have told me that aromatic cedar is a softwood loaded with oils and what not and it won't bend well. Having realized that, I grabbed a couple narrow strips of left-over Macassar Ebony and thinned them and proceeded to bend/attempt to bend them. Broke the first bend, success on the second. The trick, it seems, is knowing when to start the bending process. I watched a couple YouTube posts of guys bending guitar sides and they don't spend a lot of time at it. A little more experimentation and I should be able to bend my precious Mac Eb sides successfully. Thanks guys for the help.

[Michael Lewis]

Ron, you may be trying to bend too early. I have found that wood will relax when it gets hot enough but before that it will break if forced. Part of the beauty of using a bending iron is that you feel the wood relax when you have gentle pressure on it, but when using metal leaves on both sides of the wood you have no feeling involved, only a general recipe to follow. Either method will take some learning to get on top of the process, and it can be quite frustrating at times.

[Ron Daves]

Thanks, Michael
Rather than try to bend my Mac Eb, I found a hunk of Myrtle theat I resawed and thinned down. I followed a recipe that I used on a scrap of Mac Eb: Start stopwatch, turn on the blanket, Assemble the sandwich and get the bender all set up, put thermometer in place, then wait about 10 minutes. By then, the blanket was at 280-degrees. Started bending the waist ever so slowly while watching temp. At aqbout 12-minutes, waist bend was 75% done. Then pulled sprung cawls down over the lower bout, then upper. Didn't hear any cracks. Some guys bake the sandwich for about 20 minutes, but I just turned off the blanket and will wait 'til later this evening and take the side out. I'll post a report after that.

[Ron Daves]

Success!

[Ron Daves]

Well, success was had on the test strip of Mac Eb, but there were cracks on the upper bout of both pieces of the real sides. I'm working with with CA glue and clamps to try and save it. I started the bending at 300-degrees and am thinking I should have waited longer, perhaps 360-degrees. There is also a lot of spring-back.