Confusing and extreme limb twist

[Halfbow]

I'm trying to follow what you mean. Humor me and give 4est's post "The Mechanics of Limb Twisting Explained" a look over. That post is about the sideways bend of limbs. He weakened one side of the slat, and the whole thing bent to that side, laterally. The weak side of the bow became concave. What fix would you prescribe for these sideways bending limbs? To take wood off the strong side, right? The side he hadn't weakened yet. The side the limbs are bending away from. The convex side. This is what I did. And the effect was exactly what that post suggested it would be.

Taking wood off the side that I did made the limb move the direction I wanted. If I had taken wood off the opposite side, it would have had the opposite effect, yeah? Aka, it would have moved in the wrong direction. And yes, possibly, the tip would rotate to be more square with everything. But having the limb even farther out of line is the worse situation here, I think.

[youngbowyer33]

This is very interesting to me because I have struggled with limb twist and not been very successful in correcting it, even with advice I've read here. My conclusion is usually that the wood must have twisted grain or I did something wrong.

I don't have much to say, but in the last picture, although the limb seems to be closer to straight laterally, if you look at the bottom of the bow, the back, it looks to be twisted at a greater angle than before you removed the wood. Whenever I try looking for twist in my limbs, I hold the bow up to the light with the back facing up and change the vertical angle slowly so I can see the twist develop and it travels down the limb towards the tip.

Anyways, I agree with you that the solution seems confusing and sometimes advice sounds contradictory

[Halfbow]

Well I'm happy to find a sympathizer.  Part of the effect you're noticing on the back of the bow isn't because of limb twist, but rather wood removal. I scraped both the belly and the back of the bow. You can kind of see the corner on the back where the scraped area meets the original back.

[George Tsoukalas]

Thanks, Halfbow. Strong side is furthest from the string. Jawge

[Halfbow]

I have an update. I still haven't figured out the cure... but I think I figured out the cause! This same type of contradictory twist (where the limb leans to the opposite side that the rotation of the tip suggests it ought to) happened to me on 4 bows in a row. I was trying all kinds of things to fix it. It was starting to drive me insane. Now that I've figured it out, it seems obvious. Probably was a stupid mistake, but maybe I can save someone else from it.

It was not that one side was thicker than the other. It was caused by the way I was wrapping bike inner tubes around it during the glue up. I had been wrapping it directly around the bow, like this:




When I started wrapping around a form as well, like this:




The problem went away completely.

I don't think this is due to the support board keeping things in alignment while the glue cures, as I was always careful to do that and my bows were well aligned and supported. I think it has more to do with the wrapping process itself. While wrapping around the bow directly, the bow is getting torqued with each wrap. The more muscle power I put in to pulling on the tube to get it tight, the more the bow was getting torqued. When wrapping around a support board, the bow is not getting twisted like that, as the inner tube just gets laid over the bow like a seat belt on each wrap.

I'm still a little puzzled, as it's interesting that torquing the bow while wrapping it caused no visible twist in the unstrung bow. Yet quite a lot of twist once the bow was bending. It must have just caused it to glue up with some weird internal stresses. I'm still trying to work out the physics of that. But the support board definitely seems to have fixed the problem that was plaguing me. There's a moral in there somewhere.

[BowEd]

Halfbow.....I suspected it was your wrapping procedure giving you a limb twist,and have seen this type problem posted before.It's good you got one solution anyway.I see your using double width inner tubing also[too stiff].I split mine and use 1/2 width which is about 1.5" wide single layer strip.The inner tube can stretch a bunch then while wrapping.I've wrapped laminations many times with tube strips with no problems of twist having plenty of pressure for a bow such as yours.
To back up my observation is that I've mated laminations on horn bows using a tencik tool composed of a rope and a stick.It is wrapped very tightly but no stretch in rope.When doing this slight twisting can occur and correction in reverse is needed before glue sets.

[DC]

I cut my tube into 1" strips and wrap the same direction back and forth (2 wraps). I've never noticed any twist.

[aaron]

wow, please do a tutorial in a separate  on how to animate photos like that!

[Halfbow]

I see your using double width inner tubing also[too stiff].I split mine and use 1/2 width which is about 1.5" wide single layer strip.The inner tube can stretch a bunch then while wrapping.I've wrapped laminations many times with tube strips with no problems of twist having plenty of pressure for a bow such as yours.
To back up my observation is that I've mated laminations on horn bows using a tencik tool composed of a rope and a stick.It is wrapped very tightly but no stretch in rope.When doing this slight twisting can occur and correction in reverse is needed before glue sets.

I can definitely see how splitting the tubes in half would be better. Thanks, I will try that next time.

I cut my tube into 1" strips and wrap the same direction back and forth (2 wraps). I've never noticed any twist.

Yeah, wrapping a 2nd layer in the opposite direction has got to help too. Good thinking.

wow, please do a tutorial in a separate  on how to animate photos like that!

I used two different methods for my gifs. If you have a video you want to be able to insert as an image (like I did with turning the limb over in my hands so you can see both sides), you can just use a free gif converter online. https://ezgif.com/video-to-gif works well.

But if you want to do a stop-motion-like thing like I did to track the effects of scraping off wood, unfortunately you will need more specialized software. I used Photoshop. I'd be happy to make a tutorial for it, but I'm not sure enough people have Photoshop for it to be any use.