problems bending wood

[mastin03]

Sorry for the long post....
I'm having a heck of a time bending wood lately. I've just recently tried to both straighten a stave as well as induce a bit of reflex. I think my first attempt was bound for failure from the beginning as the wood was to thick, but now I can't seem to get anything to work.

After the first failure, I started on a hickory bow that I was going to try to flip the tips on. Never done it before, so it seemed like a good challenge. Had the limbs thinned down to just a hair over 3/8" amd tried to bend the wood on a caul using dry heat...crack. I was really slow and deliberate with my heating (heat gun held 3-4" away), never letting the wood scorch, but just getting hot enough that i couldn't hold my hand on it for more than a second. After that failure, I tried steam...got a pot of water boiling, covered it with aluminum foil and let the last 14" of the limb (1/4" thick) steam for 30 mins. CRACK.

Now being frustrated, I started looking for videos using steam, I can't see what I'm doing wrong. I've since tried to bend a piece of cherry (1/4" thick) by dry heat (crack) steam (crack) and finally by boiling (crack). It seems like the wood just starts to bend, and then it fails.

One observation from all of the above mentioned failures is that when I steam or boil the wood, i've seen that the internal wood doesn't seem to be saturated after the failure...is that normal??

I looked over Ryano's video of bending osage and it seems like the osage he bent was like a wet noodle when it came out of the steam...I can't seem to replicate that.

I'm open to any tips. I know there have been a TON of threads on this, but anything you can add that may help would be great. Maybe i'm not subjecting enough of the limb to heat/steam before trying to bend?

Everything I've read seems to indicate that people using dry heat will strap a stave into a caul pointing toward the ceiling, apply oil to the stave, and start to heat. Once the heat has saturated the limb, (from what i've read) it seems like gravity takes over and the limb starts to bend. I can't seem to get to this point.

Sorry for being long winded, I just can't seem to find anything that works for me thus far...hopefully i'm doing something stupid that someonce can point out and I'll be in business...thanks in advance

[Kegan]

How sharp are your bends? An even bend, even if extreme, is less likely to break than a small sharp bend. Also, I strap my piece down and bend it, then use heat to keep it there. I avoid applying too much heat to the outside of a bend because at this point the wood is stretch, and the heat will cause it to shrink, causing it to break, which still happens some times, but not to a really serious degree.

[Pat B]

Osage bends very easily with any type of heat; dry(with oil for me), steam or boiling. Hickory on the other hand need wet heat, ie steam or boiling. Are you supporting the outside of the curve with a metal strap? This will add pressure to the wood and helps to prevent cracks. Also making the area to be bent a uniform thickness and not trying to make the bend too tight helps. I generally have my tips about 1/2" to 5/8" thick and wider that they will end up for bending and get the thickness as uniform as possible. That way, if they crack a bit I can remove that portion when it comes to final shaping. I usually add super glue to any cracks first before reducing them just for insurance.
  Are you getting your wood hot enough? And are you getting the bending done before the wood cools? It doesn't take but a minute from the heat source for the wood to get too cool after bending.
   TBBII has a very good chapter on bending wood and a good chapter on recurves. If you don't have the TBB series, it is a worthwhile investment for any bow builder.

[Mechslasher]

with bending tips, there are a couple ways to prevent cracking the belly during bending.  the first is to use a metal strap, like patb suggested, to keep splinters from  rising during the bending process.  this strap should be very tight against the belly during the bending.  i used a strip of sheet metal for years.  steam the wood for a min. of 30-45 min. per 1/2" of thickness.  you only have about 20-30 seconds or so to bend after removing from the heat before the wood looses elasticity.  another way to reduce your chances of pulling splinters is to chase the belly to a single ring.  how sharp is your bend?  a radial bend is easier on the wood than a sharp angular bend.  my statics are usually 45 or 60 degrees and i only use steam when bending tips.  i use dry heat to tweek the tips or the limbs.

[zenmonkeyman]

Where do you live?  How dry is your house?  Maybe your wood is overdry, in which case hang your wood over a humidifier or keep it in the bathroom for a few days? 

[mastin03]

thanks for the replies folks...

I live in KY, so i can't see the wood being overly dry, but who knows, that may in fact be the case.

Pat, I do have TBB1 and 4, but not 2...maybe need to pick that up and read the section on bending wood. 

I am using the pressure stip to reduce splinters, its just that i never get to the point of splinters....the wood goes BOOM before it bends

The more i think about it, and read the responses, it seems as if maybe I'm just being a bit impatient...I'll see what I can come up with in the next few days and hopefully report back with some positive, "updated" methods.

Thanks again

[Josh]

Good luck keep us updated man! 

[Pat B]

I had another thought.    If the wood wasn't handled properly when it was cut it may be infected with fungi. Whitewoods are very susceptible to fungi and only a few days on the ground can infect them. Did you cut the wood yourself? If so did you immediately split and store it in an appropriate place?    Hickory is very strong and rarely cracks(for me at least) when bending. It will splinter if bent too quickly, not hot enough or bent too sharply.  Just a thought!

[half eye]

I dont do any bending on my bow wood, but used to bend hull planks to use on dingy type small craft. They steamer I made was a piece of steel well casing 10 diameter with both ends welded shut...one end had a 2" pipe comming out of it. That was filled with water (and some salt to raise the temp a little) when the thing started to boil the steam came under pressure (not a lot but enough to fill the steaming tube that held the plank) the pipe fed into the end of a piece of stove pipe that was insulated and had cross pegs to hold the plank up off the bottom.  The planks were left in the pipe untill they sagged under their own weight then would be taken out and clamped down PDQ.  WE tied a string to the end of the plank to pull them out of the steam pipe (steam burns hurt like a ------!  Oh Ya the water boilging contraption was outdoors and wood fired...you can pipe the live steam to whereever you want to put it.
       I don't know if this helps but we steamed a lot of 1" & 1-1/4" planks and didn't loose any.....but we did leave them long enough to "sag"....you may be right about not waiting long enough....for what ever it is worth.
half eye

[mastin03]

Pat--the hickory was a board  from 3 rivers, so I assume it was handled properly...may just be that I'm trying to bend a board and it's getting testy with me

Thanks for the idea half-eye...I've been thinking about rigging up a steamer but I keep seeing people doing this with turkey fryers, disposable aluminum pans full of water, etc, etc, and it's bugging me that I can't replicate it....Me being stubborn more than anything

[radius]

might as well give it a little longer, and if you're pressed for time, put off the whole process for another day

[Pat B]

I have never tried to bend a board. All of mine were staves.

[Josh]

here's one I am working on... Red oak board 
I steamed them and then clamped them to the form with sheet metal clamped across the belly.  they are around 1/2" thick 


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[Pat B]

Nice forms, Josh.

[Josh]

thanks Pat.  I steamed them for 45 minutes after coating with two coats of shellac.  Here is my steaming apparatus.  Hope it helps you Mastin03...
  My buddy snakeman was cold and I couldn't get him to move away from the heat for the picture LOL.   




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