Primitive Archer
Main Discussion Area => Bows => Topic started by: helmet on December 06, 2015, 05:03:08 pm
-
I have this yew at about 3" brace and am pulling to 50lbs at about 14 inches. The goal would be to get it 50lbs at 26". The lower limb is twisting to the right side and the string is off of center of the handle. How do I bring it back to center while tillering? Where do I remove wood? All help is appreciated.
-
here are some photos.
-
Check the limb thickness on either side of both limbs. Sounds like one side is thicker than the other.
-
Try forcing the string across in the nock to one side, that may give enough to get it pulling true.
I usually leave the tips a bit wide until it's drawing about 20" or so to provide some adjustment for such issues.
Narrowing at the grip and putting in some sideways bend may be necessary. Bending whilst steam is still being applied locally works well:- This video shows what I mea:-
https://www.youtube.com/watch?v=aCuXa95ffYI (https://www.youtube.com/watch?v=aCuXa95ffYI)
Thinning one edge to get it bend on the twist may be the solution, but it's difficult to work out/describe which edge. There's a good thread somewhere with a detailed experiment showing which way wood twists as one edge is weakened.
Del
-
http://www.primitivearcher.com/smf/index.php/topic,27206.msg364231.html#msg364231
-
keep the limb thickness edges same,, as suggested, get it out to about 20 and see how it looks then,,
-
Thank you folks, I 'll give it a try.
-
Anybody else worried that the bow is already under weight? Ron
-
Anybody else worried that the bow is already under weight? Ron
He has plenty of weight still to play with.
-
So, follow and read this link posted above by DC. I have the hardest time keeping this straight in my head, and since most of my bows are highly crowned from small staves, OR almost flat, because they are laminated, I rarely run into it, so I kind of forget. But, this is an important principle to understand.
To start, though, look down the limbs and check for places the crown wanders to one side or the other. Those are your likely trouble spots.
I would also probably fix the limb symmetry toward the tips. In the posted pic, there is reflex on one and deflex on the other, and That kind of stuff gives me fits.
-
Yes that link DC posted was exactly what I needed and it worked. I got the string tracking a lot better. It suprised me how little wood I had to scrape off to change that.
I am not sure what to do about the reflex and the deflex right now, I just don't have much experience steaming or heating bows and moving them the way I want. Earlier this year I staightened a W.Oak bow and a Cascara bow over coals. The W.Oak moved easily, the Cascara took a lot of work and hardly moved. The Oak was fine and its a good little bow. I wish I had left the Cascara alone, it shot fine, but after heating I had damaged the back and when I strung it, well I heard the tick.
I guess I am telling myself to "just blurr my eyes and look through the wiggles"! I may ask for some help folks.
-
If you use a heat gun instead of a fire then bending can be more controlled and precise. Basically you are just getting the wood very warm and forcing it where you want it, hopefully within its breaking limits. You can heat areas of the bow over a fire and then quickly move to a clamp and form and bend it around something or you can put the bow on the form first then heat it with the gun and apply clamps.
The nice thing about the latter heat-gun thing is you can accomplish more than one or two adjustments and maybe some tempering at the same time.
Get a French curve template from a sewing center, the long parabola type, and trace and cut out that shape on a hunk of thick wood. I dished out a groove down the center of mine for high crowned staves. Clamp or fasten the form to your table. The clamps will have to open enough to clamp stave to form and over the edge of the table or you'll have make holes in the form for the clamps.
Move your stave to whatever part of the form curve you need to accomplish your bend. That curve is a good shape for reflexing, tempering, and curving tips with the entire limb at the same time. You can either slowly heat and clamp from one end to the other or slowly heat the whole thing and begin applying clamps, just depends on what you are doing.
-
I used a heat gun and got the deflex out of the upper limb tip, it went smooth and did not take long at all. The limbs have an overall more symetrical side profile. Do I need to wait a day before bracing, tillering ect.?