Deep cook on white wood bows

[superdav95]

Hey gents.   I’ve been experimenting with the level of cook on my white wood.  I’ve been varying the way I set up my bake and coal bed.  I have been playing around with times and distance from the surface of the coal bed.  I’ve found that with the deeper cook that penetrates most of the way through the thickness of the bending portion of the limb (the working limb) the more performance and retained reflex.  This is not an absolute and there are some considerations to account for.  If it’s a self bow then I’ve only been going to about halfway through maybe a little more.  I’ve been careful to avoid charring the back as it will have explosive results and not in a good way.  I’ve done a few that have survived a very deep cook but it’s on the edge of failure.  The better self bows have had a medium cook and were better for longevity and still shot well retaining some reflex.   As for backed white wood, I think going deeper on the cook has some benefits.  The last bake session I did for some experiment bows had two of them get a little deeper on the cook.  I decided to back one of these.  This little bow was a sliver of wood at only 1.3” wide and needed some side laminate wood to build up the handle.  I had some paduak red wood and thought it would look good.  I think that for longevity the backed bows are a great candidate for a deep cook. Just some observations that I’ve had.  I’ve had some guys wonder if their cook was deep enough.  Consider the deeper cook if backing and medium if it’s a self.  Keith Shannon and Thad beckum go into some detail on this if you do a google search.   Here’s some pics of my latest backed bow with a deep cook.  It shoots very well. It’s around 50lbs.  68”ttt asymmetrical.    I’ve still got some finishing to do on it but it’s mostly tillered and good to go.  It holds 4” immediately after unstringing and climbs to 4.5-4.75” after about an hour or less.  It’s mass is 530grams It has good early string tension and smooth draw.  Still more tests on this one but it looks promising.   Here’s some pics showing the side profile of the cook through the limbs of 4 recent bows done showing the depth of cook.  From darkest to lightest.  They all shoot good but some a little better.  Be interested to hear from others on this and your findings.  Cheers.

[superdav95]

A few more…

[superdav95]

Here’s some better pics of the side by side comparisons. 

[superdav95]

One more

[bassman211]

 Some say that heat is heat whether with a heat gun ,or by fire hardening. Some will never try the process. Maybe because they are happy with heat gun results. Others swear by the process. Some have tried belly heat treat over an open fire by holding the bow in hand. The big advantage of fire hardening a bow to my way of thinking is that you can get a good shooting bow from green to finished sapling in a short period of time. No real stave work.  Cut a green sapling ,and go to work.  You show some nice examples of how fire hardening works to different degrees.. It may convince some others to give it a try. Good post.

[simk]

Very cool Dave - thanks for that! and a nice row of nice bows  you rock!
I myself do experiment with heattreating my laminates more and more.
cheers

[superdav95]

Some say that heat is heat whether with a heat gun ,or by fire hardening. Some will never try the process. Maybe because they are happy with heat gun results. Others swear by the process. Some have tried belly heat treat over an open fire by holding the bow in hand. The big advantage of fire hardening a bow to my way of thinking is that you can get a good shooting bow from green to finished sapling in a short period of time. No real stave work.  Cut a green sapling ,and go to work.  You show some nice examples of how fire hardening works to different degrees.. It may convince some others to give it a try. Good post.

Thanks Bassman.  Yes I’m preferable to the hot coal bed cooking 2-3 hours method and keeping close eye on it to be certain not to scorch too quickly.  To eachs own.  I’ve tried many different way with both heat gun and coal bed.  I find the better results with coal bed personally.  I’ve seen improvements with heat gun over raw wood for sure.  My next experiment with heat treatment is to design a long induction electric coil type heater that can be used in the winter months.  I’d like to see a more precise cook on my test bows.  I’m sure others here have thought of the same. 

Dave

[superdav95]

Very cool Dave - thanks for that! and a nice row of nice bows  you rock!
I myself do experiment with heattreating my laminates more and more.
cheers

Thanks Simon.  Yes I could imagine you do as I sense you like to experiment. 

[Muskyman]

I’ve cooked a few bows that were less than seasoned over charcoal and I learned a little about it   
Cooked one way to much, had it to close to the coals. My impatience got the best of me on that one. Another I didn’t cook it enough and got quite a bit of string follow. I’ve made a decent pit to cook in after my failures. Looking forward to trying it again and always watching when I see your posts about it. I have seen Chad and Keith’s videos online also one that Clay Hayes did with them.
As always thanks for sharing.

[Jim Davis]

I can't remember the numbers and I can't find the info--yet--but something like 70?, 90? percent of the tension and compression stresses are withing 10? percent of the surfaces. The middle (neutral) layer has no tension or compression stress at all, only shear.

So what ever heat does to the middle wood has no effect on performance.

Heat certainly is useful in stiffening or bending a limb. But deep heat, not so much.

[willie]

what kind of wood is the belly and the backing in the pic in reply3? 

you are backing with a lam of untempered wood after heatreating the belly/core?

[superdav95]

what kind of wood is the belly and the backing in the pic in reply3? 

you are backing with a lam of untempered wood after heatreating the belly/core?

Willie.   They are all shagbark hickory.  The pic in reply number three just shows a close up of the dark roasted bow from above.  It’s backed with bamboo strip that has also been heat treated on the belly of the strip prior to glue up.  The heat treatment of the hickory is all done prior to glue up.  Most of the reflex is baked in and not glued in.  I think this has something to do with why I get to retain as much reflex as I do. 

[superdav95]

I can't remember the numbers and I can't find the info--yet--but something like 70?, 90? percent of the tension and compression stresses are withing 10? percent of the surfaces. The middle (neutral) layer has no tension or compression stress at all, only shear.

So what ever heat does to the middle wood has no effect on performance.

Heat certainly is useful in stiffening or bending a limb. But deep heat, not so much.

Interesting Jim.  I’d be very interested in this info if you can find it.  I suspect you are correct regardless on this but would be nice info to have while I’m continuing to experiment for max performance.  On a related note my moisture content varies between these bows and the deeper cooked ones typically have less moisture.  Not by a huge margin but some.  I also find that they absorb less moisture overall if left out in the shop in comparison with other bows that are not as deep a cook.  There still may be something to this deep cook stuff yet and some benefits.  I’ll keep one playing with it and report my findings anyway.  It gives me something to do. 

[Bob Barnes]

Dave, there's some information on page 106 of Bowyer's Bible 1.

[willie]

heat tempered wood has been proven to have less moisture uptake than plain dried, so that might be a plus when using hickory.
If the tempered wood were only on the the belly side and a third of the limb thickness, then that would be be sufficient for lam bow as far as having enough heattreated wood to take the compression stress. I mention that as there might be an easier way to heattreat thinner lams to an even consistency.