Author Topic: First try at heat bending...Yikes!  (Read 364 times)

Offline takefive

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First try at heat bending...Yikes!
« on: July 12, 2013, 02:14:00 PM »
I was working on bow number 7, learning as I go, and sure still have a lot to learn.  It was my first try at a stave (red elm from the big auction site) and my first time using a heat gun to try to flip the tips.  I had the back down to one ring and it was floor tillered.  The tips were 1/2" wide and a bit less than 3/8" thick.  I heated the belly until it turned brown, started bending very slowly and sure enough got a deep crack along the width    :confused:   Just wondering where I went wrong?  I made a drying box and had the bow in it after I roughed it out cuz the MC was 20%.  After drying, it was 8-9%.  The box isn't very wide or deep, only about 6" and my meat thermometer showed 140 degrees with just 2 75 watt bulbs.  Too much heat?  I also noticed that the belly grain had whitish flecks in it when I was scraping it.  Really hoping to avoid wrecking the next one and am leaning more towards steaming the tips.   Any advice is appreciated.
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Offline PEARL DRUMS

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Re: First try at heat bending...Yikes!
« Reply #1 on: July 12, 2013, 02:46:00 PM »
Too thin is my bet. Try bending it at 5/8" square, then if a small crack shows up you can work below it. The color alone doesn't dictate deep heat. You can get a heat gun to darken wood in seconds, but it wont bend without breaking. Steaming works great for statics, butr flipped tips can be done easily with dry heat. Just gotta tweak your method a bit. Grab some scraps and practice a few.

Offline takefive

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Re: First try at heat bending...Yikes!
« Reply #2 on: July 12, 2013, 05:21:00 PM »
Yeah, practice would have been the way to go.  That was in the back of my mind until I got home with my brand new heat gun and being way short on patience...Well, now I have lots of red elm to practice on   :knothead:    Thanks Pearl Drums.
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Offline Bowjunkie

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Re: First try at heat bending...Yikes!
« Reply #3 on: July 12, 2013, 05:43:00 PM »
Like Pearl said, you should not have changed the color of the wood at all. You can get it plenty hot enough to bend with the heat gun, without scorching, by moving the gun in a slow sweeping motion, about the same speed you would slop paint on with a brush, never stopping, from about 4" away. Heat all sides. Heat it until it's too hot to touch/hold, perhaps an additional minute more, then make the bend before it begins to cool. If it begins chaanging color, move faster, move the gun farther away, or both.

Keep in mind, you don't only want to get the outer surface hot, you want it hot all the way through, and wood is a poor conductor, so don't only concern yourself with the surface temperature. As you warm the wood, imagine the heat slowly, slowwwwwly soaking into the stave from all sides. You don't want to scorch the outside before the center is hot enough too. So, of course thinner parts take less time, thicker areas like the handle take longer.

With the size of material you are working with, it should have been hot enough to bend in 7-10 minutes... depending on how long of an area you are heating.

Your dimensions should not have mattered. The moisture content was fine. I would not use steam. I try to follow the popular advice of "dry heat for dry wood, wet heat for wet wood".

I think you probably heated it too close, too slow, too long... or all of the above.

Why don't you try the other limb, for practice if nothing else?

How about the end you tried to bend, is it ruined?

Offline takefive

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Re: First try at heat bending...Yikes!
« Reply #4 on: July 12, 2013, 06:06:00 PM »
Thanks for the tips, Bowjunkie.  I must have bent it before it was heated deep enough in the wood and had the heat gun too close to begin with because it was under 5 minutes before it turned brown and I started bending it.  I did CA glue the crack and clamped it overnight, but it snapped off when I put pressure on it the next day.  I will practice on the other limb and cut some sections out of the limbs to practice on some more.  Saving the handle for my next board bow :-)
It's hard to make a wooden bow which isn't beautiful, even if it's ugly.
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Offline vanillabear?

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Re: First try at heat bending...Yikes!
« Reply #5 on: July 12, 2013, 06:17:00 PM »

Offline takefive

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Re: First try at heat bending...Yikes!
« Reply #6 on: July 12, 2013, 10:48:00 PM »
Thanks VB, I will try the pressure strip on the next one.  Yeah, I thoroughly destroyed this one.  When I tested the bond it cracked  about 8 inches and was hanging on by a thread. Disappointed as I was, I guess it was better to have it break then instead of holding until I drew it back on down the line.  Just going to write it off as a lesson learned.
It's hard to make a wooden bow which isn't beautiful, even if it's ugly.
-Tim Baker

Online Pat B

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Re: First try at heat bending...Yikes!
« Reply #7 on: July 12, 2013, 11:45:00 PM »
When I bent recurves in an elm stave I greased it up with olive oil clamped the stave in the form and slowly heated it until gravity began to pull the stave down. I then clamped the stave along the recurve form.
Make the most of all that comes and the least of all that goes!
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