Tricks To Fixing Limb Twist (Tillering Course ep 10)

Today, we're talking limb twists. This is a video in a series of videos I've made on bow making, or more specifically, tillering. There's a playlist in the description or in the end screen if you want all the videos. Thanks for watching. I hope this helps. Enjoy. I couldn't be more excited to talk about limb twist because it's something that, it's like an annoying thing when making a bow. It can happen, but it doesn't have to because it's completely preventable by taking a couple steps proactively, and that's the key. If you're reactive to limb twist, you can generally get the limb twist out, but very often, you're gonna finish with a draw weight that you don't desire. So, the first step to proactively taking out limb twist is to make sure your knot grooves are equal on both sides. So, as you file in on the left and on the right, your knot grooves, if one knot groove is deeper than the other, then that could cause limb twist. Now, that is the easiest type of limb twist to correct, but that is something to keep in mind for sure. On top of that, if and when you're using a tillering string, the quick-release knot you use to tie in one of the knot grooves could not be centered, and this can make limb twist appear to be happening when it's actually not, so this is quite important to make sure that your tillering string is running directly down the center of the bow. When I file in my knot grooves, I like to have a bow string or a tillering string at hand, and that allows me to measure to make sure it's deep enough, and what I like to do is just make it flush on both sides of the limb where the string goes into the grooves, and if that's flush, then limb twist won't happen. There's one other way to prevent limb twist. Let's go over to the bench, and I'll show you. I'm working on an Ipe bow right now, and I'm at the point where I just started pulling it on the tillering tree, but I haven't yet got a string on it. At this time, I like to check for limb twist, so before it could even happen to me, I like to check and even out the thicknesses of both sides of the limb to make sure that we don't run into future problems. It's better to proactively work on it now than later. With that, you need a measuring tool. I find that the more precise of a tool you can get, the better results you're gonna have, so calipers are for sure my number one choice, but with a careful eye and a tape measure, you'll be totally fine, or a little ruler. You just wanna go as precise as possible because you'll run into less problems when you can get really precise. So let's jump down here, and let me show you how I check for future limb twist and how I prevent it now before it even becomes a problem. Okay, so I've got my bow limb right here. Now, this is the belly side of the bow where I'm shaving wood off, so it would bend in this direction when we're gonna go to shoot it. So I like to take my calipers, and I'll start about three inches from the handle, and I'll take a measurement. I'll go to the other side of the limb, and we'll take a measurement. The right side of the limb is thinner than the left side, so I'll take a Sharpie, and I'll mark the thicker side just with a little line. From that mark, I'll move down just about two more inches, and we'll check again, four, five. So that's quite a bit different. This side is still thicker. Now, I'll move down again. We're gonna continue to move down every two inches all the way down the full limb, three, six. So that's the same. We're gonna skip that area right there. We're good there, three, two. So here at the end, a couple marks. Something to keep in mind if you're using calipers is on the left and the right side, you want the calipers to cover the bow the same distance. So on these calipers, I've got these little, you can see the little grooves right there. That's where I hold it, is right on those grooves over the edge of the bow. That allows both to be consistent, because if I were to put one side in 1⁄2 inch and the other side in 1⁄4 inch, it's not gonna be measuring the same, because it could be a little rounded on that corner. So you want it to not just be the very, very edge if you've already rounded the corners, but maybe go in about 1⁄2 inch on the calipers. If there's no mark on your calipers already, just make a little mark with a Sharpie or something. That way it can be consistent from the left to the right while measuring. So with this specific limb, we have a good portion of it that's off, but there is a section in the middle that is even side to side. Sometimes one side of the limb will be thicker and then it'll switch halfway through. But on this specific bow, we've basically got the first 12 inches that is too thick. So I'm gonna go ahead and mark that side. And then we've got a gap of about eight inches. And then again, we've got the last five or six inches that is too thick. So right now I'm going to take down the wood on the areas that are too thick to even out both sides. Lots of times it's not a lot of wood, but this, doing this now is so important. It just prevents so many more problems in the future, as well as it doesn't overstress any part of the bow, which is the ultimate goal when we're tailoring is to never overstress any one area of the bow, but make the limb distribute the stress evenly. Then you will have an awesome shooting bow. I got two more real quick pro tips when dealing with limb twist. The first one is when you use the tillering string, on one side you've got the loop, so you're running nice and true down the bow. On the other side, you've got your knot. And check this out. It may not be running down the bow straight, which could cause the limb to twist because it's pulling much more on this side. And the way to fix that is just to push that knot over to the center and you can true it up so it's running right down the middle of the bow and that'll help you avoid limb twist. The second pro tip is that if you're using a tillering gizmo on the bow, make sure you rub it on the left side and the right side. So on both sides, and that'll show you if the sides are bending differently. And that'll kind of keep you in line so that you don't have to measure each side over and over again. But running that tillering gizmo on the left and the right when it's bending down will do a lot. All right, awesome Kramer. You've showed us how to prevent limb twist in advance, but I'm already far into my bow and my limb is twisting. What do I do? You just kind of do it in reverse, honestly. And so you wanna figure out which side is thicker or which side has more material and is overpowering the other side. Then you just remove wood off the thicker or the side that's overpowering the wood. In some cases, depending on the wood grain, it may be equal thickness on both sides of the limb, but one side is overpowering. And in that case, you would want to remove wood off the overpowering side. So that's one way. Remove wood off the overpowering side. The other way to remove limb twist is to file a knot groove in deeper because they're not even, or if the thickness of the limb is equal and you're like, this just doesn't seem right, you can file one knot groove in just a little bit deeper and that may correct that limb twist. Just make your adjustments small and incremental and this will allow you to avoid making really big mistakes on correcting limb twist. Something that you shouldn't be scared of and it doesn't really happen very much except in extreme examples. So your thickness is gonna have to be way off, your knots are gonna have to be way off in order for you to visually see the limb twist. Do the checks in advance and limb twist won't affect you and your bow making. With regarding limb twist, there's one more thing that I don't run into very often but it can happen so I wanna let you know about it. And that is getting a piece of wood where the grain is kind of tornadoed through the wood. And this can cause limb twist before you even start. So you wanna look if there's some warpage in the wood and if there is, that's not the end of the world. What you can do is you can steam it or if there's above 10% moisture in the wood, you could even probably use dry heat and twist that wood back to even. But a board can be twisted. If you've ever held up a two by four at a hardwood store, you've seen the boards that are just screwed up literally. And those type of boards, if you try to tiller those straight, you can run into a lot of headaches and problem. So before I would start tillering, I would take that twisted wood and then I might put a clamp on it this way and pull it back to the other direction. And I would just heat it up and then heat it beyond straight because when you release that clamp, it's gonna come back to even and then you're good to tiller. But keep that in mind, if you're having a really tough time with limb twist, that could be your problem as you started with a not straight board or not straight enough at least. And if you don't recognize that, you could run into a lot of problems. Now, this bow right here is actually pretty straight and I try to avoid doing this as much as I can. I'll show you real quick with the vise what I would do. So ideally, you don't have to do this, but you could put this limb even inside of a PVC pipe and then introduce steam into it just by boiling water in a pot. Heat it up and then by putting a clamp on it like this, you can push down this side and that's gonna take that limb twist out. And so you could even hang some weights on this side if you needed to and twist it beyond straight and then it'll come back to straight later on. After this initial tillering course, I plan to do some more videos and more in depth. And one of those topics I wanna cover is heating and bending wood, when to use dry heat, when to use steam, when to use boiling water and the ins and outs of that. But in general, if you're not sure, make it wetter, get the steam if you can. And if you're trying to do that right now, you can look up, there's plenty of videos how to steam wood and you can do it on the cheap.