Catastrophic failure first time trying to bend sides.

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Ukemakinmecrazy

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Any tips? Bought a heating blanket, sandwiched it between two pieces of aluminum roofing flashing soaked the wood for a bit in water, wrapped it in water soaked paper, then wrapped it in aluminum foil and placed it in the aluminum flashing sandwich. put it over my mold and clipped it at one end with the sandwich standing up vertically. waited till it started to wilt and slowly tried to bend the sides down. all went well until I reached the waist. Then I had a hard time getting it to give at all (it was planed to 2mm and sanded a good bit after that. kept letting it get good and hot and then applied some pressure (not a lot) and heard a crack. The board broke in two. Took it out of the sandwich and it was scorched on both sides.

Man this is a lot harder than it looks.
 
Here is how I do it. Get a piece of thin stainless steel about the same thickness as the flashing you used. Forget about all the paper and other stuff. Soak the wood in a tub or tray of water for about 15 minutes. While the wood is soaking, set the stainless on the bending form then lay the heating blanket on top of that. When the wood is ready lay it on top of the blanket, attach the middle or waste bending block on top of the wood without bending it. Plug the blanket in, as it gets hot slowly bend the wood into the waste almost all the way in to the form. Bend the top bout section of the wood into place and secure it once it is done. Do the same for the lower bout section and secure. Once all the steam has escaped from the wood, unplug the blanket and let the whole thing cool down. Once cool, remove the wood and place into your building form. Do the other side the same way.

Different woods, especially curly or figured woods could use a stainless piece on both sides of the wood. I've been bending with this method for 20 years and have rarely broke a piece of wood, but sometimes wood just breaks, forget about it and move on. The more wood you bend, the easier it gets and one day its just another part of the process. Good luck.
 
Ukemakinmecrazy said:
Took it out of the sandwich and it was scorched on both sides.
Click to expand...

I think this might be a clue.

By the time you scorched both sides, I reckon the wood was dried out, brittle through, and set into its existing shape.

Based on my limited experience, too much heat is not a good thing.
 
It happens to all of us from time to time. Take heed of the good advice offered by others in this thread, keep trying, and you'll get to a way of doing it that works for you. Also, at the outset it helps to use wood that tends to bend without a lot of drama, like cherry or myrtle.
 
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Your problems I can see from here

1 Aluminum Flashing is too flimsy. You want blued spring steel I have used stainless but it isn't as good as blued sring steel

2 If you scorched you probably dried out your packet

3 Bring the waaist down first but leave it up about 1/4 " to 3/8" then do the lower bout then the upper then bring down the waist the final 3]8"

4 You didn't say the wood but most wood does not benefit from soaking. Just a spritz on each side is usually plenty

5 When you get up to temperature don't dally. I't much more destrutive to the process to dry out completely than move too quickly once you are up to temp.

6 What is your wood thicknessed to and what is the species? If you have difficult expensive wood using supersoft and pre steaming can work wonders.
 
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Ukemakinmecrazy said:
Any tips? The board broke in two. Took it out of the sandwich and it was scorched on both sides.

Man this is a lot harder than it looks.
Click to expand...
I did the same thing, then used a hot-air gun into a pipe and the next pair bent perfectly. I'll have my SM bending iron in a couple of days.

Flame me if you want, but bending sides on a bending iron seems to take out the mystery; for me. Firstly, the moisture can be monitored directly, because it can be seen. All the activities of bending are right in front of the operator, and not hidden in a package of fabrics, foils, slats, plywood, and cauls.

Starting with a hot iron:
Monitoring moisture content is easy, (bubbles and steam) and starts by spritzing both sides lightly (maybe more depending on the action/reaction of the particular wood). The water will bubble on the outside surface as it's held against the iron. With patience, wait a few seconds for the wood to relax. If the water is no longer bubbling, spritz again, and resume contact with the iron. Don't let it dry out for more than a moment; let the wood relax and turn plastic. It will.

Maybe I'm wrong, but I had a better experience with the bending iron than with my fancy Fox bender and temperature monitoring black boxes. Although I still use thermocouples and digital displays to track temperatures; not sure they're totally necessary if tactile experience is gained. I still use the timer to shut things off at 30 minutes or so, in case I forget.
 
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Dan Gleibitz said:
I think this might be a clue.

By the time you scorched both sides, I reckon the wood was dried out, brittle through, and set into its existing shape.

Based on my limited experience, too much heat is not a good thing.
Click to expand...

This happened to me the first few times i used a heat blanket. I was used to light bulbs which take ages to heat up. THe blankets just baked the wood in 2 mins on high and everything cracked.
 
Beau Hannam Ukuleles said:
This happened to me the first few times i used a heat blanket. I was used to light bulbs which take ages to heat up. THe blankets just baked the wood in 2 mins on high and everything cracked.
Click to expand...
Thanks, Beau. Seeing your work and knowing you are a voice of experience, helps those of us who are plodding through by the school of hard knocks. Not glad you fried and broke wood in the side bender, but to hear that old timers had this happen too, may just keep us from giving up at the loss of a few supplies; struggle thoughest we may.
 
DOOOH, it was Cherry. I think I need to control the heat better.

saltytri said:
It happens to all of us from time to time. Take heed of the good advice offered by others in this thread, keep trying, and you'll get to a way of doing it that works for you. Also, at the outset it helps to use wood that tends to bend without a lot of drama, like cherry or myrtle.
Click to expand...
 
Why all the blankets? I bent my sides around a hot pipe as shown by Rob O'brien, worked great. I get that you want a more automated jig when building for a living, but for us hobbyists?
 
There are plenty of takes on bending. On my website pegasusguitars.com I have a tutorial on my bending procedure. It is in the "More" dropdown list at the top of the page. Titled "How I bend guitar and ukulele sides". I've bent a lot of sides with my set-up and have not found any species that are particularly difficult. There is no "one way" to do it, but this works for me. Control of the temp and a fast, efficient process is very important.
 
Those blue steel shims are too springy, they will spring straight and crack a fragile set of figured koa before you could say heat bender! I have no sympathy with hose who look for sheericans in tort cuts to luthiery. Doing a 'basic' apprenticeship in hand skills is what I learned (apart from a whole host of other stuff~) on my research travels this Fall. Although I admire much the 'can do' confidence of many of the Americans I met, an old fashioned European craft apprenticeship as followed by my more than capable assistant is nothing to be sneered at. Emulating the careful step by step approach, even in an amateur context will minimise the disappointments and failures aired here.
 
Pete Howlett said:
Those blue steel shims are too springy, they will spring straight and crack a fragile set of figured koa before you could say heat bender! I have no sympathy with hose who look for sheericans in tort cuts to luthiery. Doing a 'basic' apprenticeship in hand skills is what I learned (apart from a whole host of other stuff~) on my research travels this Fall. Although I admire much the 'can do' confidence of many of the Americans I met, an old fashioned European craft apprenticeship as followed by my more than capable assistant is nothing to be sneered at. Emulating the careful step by step approach, even in an amateur context will minimise the disappointments and failures aired here.
Click to expand...

For those who wish to quit their day jobs that is good advice, it's is a hobby for me. But I would still like to do it well.
 
Ukemakinmecrazy said:
For those who wish to quit their day jobs that is good advice, it's is a hobby for me. But I would still like to do it well.
Click to expand...

Gotcha on that this is not a day job for many of us. Sticking with your original plan and dialing in the major variables will eventually get your recipe for bending sides. You know what those variables are already, so this can be weeded out by your own R&D. Dialing in the major variables of heat, moisture, and timing will take a little experimentation. Ballparks are all we can offer, since we have different equipment.

If we pitched all of our thermometers into a circle, they'd probably measure 15 degrees F or more differences. Our heating blankets and controllers also give variance. The timing and feeling plasticity in the wood are also going to vary amongst us to some degree.

Most of all, don't be discouraged and keep your confidence level turned up high.
 
I am a big fan of Pete Howlett, and I think his methods are sound, but I am also a big fan of spring steel. I think its really all in the application, I am the first to admit it can be unruly unless properly controlled, but its properties are useful to me. It provides better support at the waist bend for me, since it provides some resistance on the back of the bend. I find it easier if there is support under the waist. I also monitor the temperature and use a router speed control to keep it from getting too hot. Koa bends fine around 240F, so once I get there on the temperature probe, I start bending and try to get it done fast. I don't usually let the temperature get above 300F.
 
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