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black locust flatbow build

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M2A:
Correct Zugul heat treating could reverse the corrections you made. I usually try and make string adjustments when I heat treat. If you have it clamped you should be ok. Nothing worse than watching the wood move back to how it started :)

I have never thought of trapping as an angle but as distance. But I guess I do a 45 degree angle because I trap each side 1/8" taske the corners down the same. I took a few pics on a stave thats roughed out so Ill try and explain best I can.  First I mark out the back of the stave with line 1/8" from the corner.
IMG_5132 by Mike Allridge, on Flickr
I put a few measured marks but draw the line with my fingers as the gauge. 1/8" each side has worked fine for me but could go a bit more I suppose.   
IMG_5133 by Mike Allridge, on Flickr
Then I do the same down each side measuring from the back of the stave.
IMG_5134 by Mike Allridge, on Flickr
Finished thickness of your bow may only be about 5/16"(8mm) or less at the sides so I would not recommend going any deeper than 1/8" here.
Then remove the wood at he corners to the lines. No need to trap out to the tips, tapper the trapping out when you have about 3/4" width in limb.
Hope I explained that correct. Just some food for thought. I'd tiller it out to at least 20" before considering trapping. Thats just how I do it.
Mike     

Zugul:
M2A you'v been chrystal clear! Unfortunatly I normally got chrysals before getting to 20" draw so trapping won't help me in that regard. I guess it happened for a cuple of reasons: I did not put a lot of effort in getting a good thickness taper from the get go, the bows were shorter and less wide, the wood was pretty low quality and overall I rushed a bit too much.
Now, I have a few doubts about heat treating. For me the most convinient way to do it would be with a heatgun, but from what I've seen and heard using a fire pit should give better results because the wood gets toasted more deeply. How slow should I go to get a similar depth with a heatgun? I've tried to heat treat my last bow, but the colour change reached maybe 1 mm (0.04"), a bit too shallow to make a significant difference. Also, if I heat treat too soon, the harder layer of wood will get scraped away during tillering, so I guess it should be done in the final part of the process, maybe at 22-24" for a 28" final draw lenght, correct?
one more thing,at this point should I keep the belly perfectly flat or should I take off the corners first to get a more lenticular cross section (middle of the belly 1/16" to 3/32" higher then the sides) and flatten it out when I get closer to the final draw lenght?


--- Quote from: George Tsoukalas on October 15, 2022, 07:03:18 pm ---I was talking about the belly in relation to the back. What the back does the belly does also to make the thickness constant. Jawge

--- End quote ---

So the difference in strain the portion of the belly a few mm deeper is not going to be relevant if the thickness of the wood in that point respects the thickness taper, right?
sorry if these seem pretty obvious observations but if I don't understand perfectly how the things should be done and why they have to be done like that, I'm going to screw up again and again  (lol)

Thank you for your patience!

superdav95:
Zugul. 

As for heat treatment I would clamp the bow to a form to a slight reflex and slow bake over coals using a pit method.  You can achieve  very similar results using a heat gun too.  I’ve done this myself a number of times in the winter months when my fire pit was covered in snow.  I build a stand for my heat gun that positions the gun over top of the belly of the bow about 3-4”.  I usually start at the fade of one side and just move the gun along every 4-5 mins on high setting.  It may vary in time depending on your gun and heat output.  I think mines a dewalt make it it helps.  This gets you a deep heat treatment and jay move it along 2” or so.  Try a build your gun support to trap most of the heat to the belly and avoid the heat getting around to the back.  I go about 4 mins or so check it for depth then move it couple inches and this gives me a cook that goes little over half way thru the limb.  I do prefer to use the hot coals method as I can do 4 bows at once and don’t have to move the gun every 4-5 mins.  I’ve also done this repeated 2 times on bows with good results if I felt it didn’t go as deep as I liked.  I also applied pine pitch while still hot on one of my bow once as demonstrated by Marc St. Louis.  He has a good video showing this.  I found that  It seals and locks in the hydrophobic nature of heat treated white wood. Just food for thought.    Here’s a pic of my gun support I used if it helps. 

Aksel:
Wood source?

I have never worked with black locust but I hear it frets easy. Is this stave from the same source as those other bows you "screwed up"? Sometimes you simply hit a bad tree and make staves from it and then they all cause the same problem..

design.

You make this longer and wider which is good.

Tillering method.

If you made a few attempts previously and they all fret in similar ways you need to change something in what you are doing.
If there are knots or minor bumps on the back I usually leave the belly flat and let the back compensate with extra thickness. That works with elm at least.
When I am working a stave I really don´t want to mess up, I go very slow. In between rasping and checking the tiller, I sand it or scrape every part of the limbs smooth and make it look like a nice bow at all times. It might sound stupid but it helps me to stay focused and go slow. After floor tillering to a VERY nice bend at what seems like a good draw weight (compare flexing the limbs against the floor with other bows) and sand it I pull it to brace height 20-30 times on a long string and check the reflection in a window. When that is perfect I let it sit braced for a while to see if it takes any set at all. If I go this slow and careful to brace height I usually won´t have much more work to do to get it to full draw. This is really key in my experience, to get it to perfect brace height with no set. Good luck!

M2A:
Lot of good info from Superdave and Askel. So Ill try and not repeat all they said ... Its not practical for me to heat treat with a fire pit so I have used a heat gun for eavery bl bow I have posted here. I mark the limb off in 6" lenghts. Then work each 6" section for about 5 min to get the color I want, heavier(better) locust maybe a bit longer, lighter wood a bit shorter time. This is about half the time I would do for white woods such as hickory or elm. The color Superdave has is about my goal. My new heat gun has digital settings, so I set it at 850 deg F.  Its discussed in older topics but I believe the heat treatment workes deeper than the color change, just my thoughts on that. But you could do that at 24" inches on the tiller. Because you already have tip overlays glued on I'd stay away from the tips about 8" or so to not degrade the glue joint. Just my thoughts if you decided to heat treat.

I think the problem most encounter fretting with bl is because they use dimensions too short or too narrow or both. I think at 68.5"x2" is good for what your after, to be successful. I also try and keep the belly flat as I go when its on the tiller tree. Make yourself a tillering gizmo, helped me alot to find the stiff spots. Although it will not work well around that 1 area your questioning.

Take your time. Sounds like you have learned from your past experiences and are going to make this one work. and best of luck.
Mike

 
     
               

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