Weird limb torque...help!

[MtDent]

Ive been tillering my first bow, a 68" ttt red oak board, and ive been getting a weird bend in the limbs. They bend smoothly/evenly except when you sight down the limbs. When you look down them on true tillering stick, both of them, one side bends more than the other, like so:
 


My dad, being an engineer, taught me simple beam theory and told me to start taking wood off the lower side, the left in this picture. but I wanted to see what you guys think. I've been working on it for days and just cannot get either limb to stop bending like that. (And no I'm not just holding the camera crooked ) also, it gets worse as I bend it farther and farther.

[burchett.donald]

   From what I can see that is a very acceptable amount of bend or torque in the limbs. You can use a caliper and check the thickness of the limbs on both sides. I've seen worse in store bought fiber glass long bows. More pics may help also, maybe a belly shot from tip to tip with tiller stick.

[MtDent]

I'll go get some more pictures now

[Prarie Bowyer]

Where is the torque? 

I keep a piece of swirly grained maple that I bend and look at the torque and limb twist.  It's easier to "feel" where to remove in order to fix the problem.  So find a section that bends like my twisted bow and look at what is going on there and how I'd fix that spot then do that on the actual bow.  It's made a big difference.

Some is ok.

[MtDent]

Well the picture doesn't really do it justice. Plus I don't have it bent very far on the stick.





Yes the tiller isn't very good.. still working on it but I'm trying to get it to stop bend like that before I go any further. It isn't even at brace yet. Plus my stick isn't very straight and it throws me off sometimes...lol.

This is the swirl in what will probably be the top limb



The string does track down the center, I just took the picture at an angle.






Sorry my pictures aren't that great. It's kinda hard to hold my not-very-straight stick, take a picture and take care of my little cousin with a bloody nose at the same time

[MtDent]

PS ignore the very messy "Workshop"... lol I have to use my breezeway because there's no room in my garage or shed for this kind of thing.

[MtDent]

PPS, it just blew up. So never mind

[Cameroo]

Lemme guess - she blew by that "swirl" on the top limb?  That's some serious runout, and that board was probably destined to blow regardless of how you tillered it.

But for future reference, your dad is right.  The limb will always twist toward the weaker side (which in your photo would be the high (or right) side, therefore you'd remove wood from the low (left) side to get it to come back around.

But that looked like a pretty minor twist.

[MtDent]

Lol that's exactly where it blew. I knew it would go. I wanted practice on the bad wood though instead of going straight to the expensive stuff. It had bad grain all around so it was destined to crack. Maybe I'll turn the surviving limb into an atlatl!

[xin]

The first picture I saw the runoff and knew it was a goner.  As I  scrolled down , the prediction was fulfilled.

[Tom Leemans]

You guys beat me to it. I was gonna say that swirl looked real bad!

[burchett.donald]

  Looking at the pic the twist started at the severe grain run off. Sorry it blew on ya but that one was destined to do so. I don't think your tiller had anything to do with the limb twist. You will find that almost every stave or board bow will have some twist, some more some less.

[bubby]

Lol that's exactly where it blew. I knew it would go. I wanted practice on the bad wood though instead of going straight to the expensive stuff. It had bad grain all around so it was destined to crack. Maybe I'll turn the surviving limb into an atlatl!

that is poor reasoning, never buy wood that you know will fail, give yourself the best chance to succeed, allways, Bub

[Prarie Bowyer]

Mee too.  I saw that run out and thought.... don't even waste your time!

[mikekeswick]

If you can't find better boards next time back it with thick rawhide. As already said that board had zero chance un-backed. Also when you are still using the long string the outer limbs should look stiff or else when you brace it they will be weak.