Hey guys, this is NUSensei. Today, I will be covering the topic of what is bow tiller? And, by extension, why is bow tiller important? Tiller is a measurement. It’s measured using the bowstring and the bow itself. Now there are a couple of different measurements. The first one is brace height. That’s the distance between the string and the throat measured like this. Tiller, is the difference between the gap from the string and the upper limb and the string and the lower limb. For a one-piece traditional bow, the measurement is taken where the limbs begin to curve. For a three-piece takedown bow, the measurement is a bit easier, it’s from where the limb connects with the riser. So, here, and here. Normally you would measure using a ruler or a bowsquare, but in a pinch a lot of archers will use an arrow instead. So they measure it from here and here. If the distances between the top limb and the bottom limb are the same, that’s called neutral tiller. However, most modern bows, such as the Olympic style recurves are meant to be shot with a positive tiller. What this means is that the gap between the bottom limb and the string, is slightly smaller than the upper limb and the string. The exact difference between top and bottom limb, varies between archers and bows. When tuning a bow, you normally start with 1/8 inch difference. Although that might shrink to around 1/4 inch, depending on your tune. Using the arrow as a reference, if we take the measurement between the top limb and the string which is where my fingers are and compare it to the bottom limb and the string you can see that there is that much of a gap. So, the bottom limb, is that much closer to the string and that’s a fairly average tiller. What this effectively means is that the bottom limb is slightly heavier than the top limb. Why is that the case? The reason why a positive tiller is needed is because of the design of the bow and this reason isn’t immediately obvious. Now the bows are symmetrical. You grip the bow in the exact centre. That’s the case for balance. However, when you nock the arrow on the string and especially when you place it on an elevated rest the arrow is above the middle of the bow. So when I draw the string back, especially using a split finger technique, as standard for modern archery, when I pull it back I’m actually imparting an uneven force on the limbs because I’m not drawing the string back in the exact centre of the bow. I’m actually drawing above it and that means that this top limb is under different tension, to this bottom limb. Think about it this way. Because I am drawing the string back above the mid-point of the bow, that means the top limb is actually slightly closer to me than the bottom limb and that means when I release the string, the top limb should snap back into position, slightly before the bottom limb. Essentially, that means the limbs aren’t synchronised to borrow a compound term, and compound bows have a similar problem. When the cams don’t turn in the correct timing, one will go back before the other and that causes some issues. The same thing applies to recurve and that’s what the tiller is for. So, considering that because we are holding the bow at mid-point, but drawing it somewhere else we have to compensate for that and making the bottom limb heavier than the top limb. It’s only a very slight difference. But that should bring the limbs into synch and that means when you release the arrow, both limbs snap back in to place with the same amount of effective tension. Not every bow needs a positive tiller. This depends on the style that you shoot. This is very important to consider when you are buying a bow, getting it set up, or even making a bow. The standard method today, is split-finger. As you saw before, the split-finger method is slightly higher than the centre of the bow where the grip is. If you shoot three under, it’s closer to the centreline of the bow and if you stringwalk, that will be even lower and lower. Depending upon how far you go down. What this means, is if you shoot three under or stringwalk, you won’t need a positive tiller. You can use a neutral tiller or even a negative tiller. Depending upon how far down you go and how much tension you place on the bottom limb. So, what are the ramifications of not having the right tiller? Well, the first and most noticeable one, is vibration. Because the limbs don’t snap back at the same, time you will find there is excessive vibration in your bow. Secondly, the balance might feel wrong. This is because you expect the bow to have an even amount of resistance. But, if your tiller is wrong and you will notice this especially if it is the wrong way round. That the bow might be pulled up or down, when you reach full draw. Because, instead of having a compensated balance because of the tiller, you might be having too much tension on one limb, so you might be pulled down. Or, you might be pulled up. As you get to full draw, the limbs come under tension and things don’t feel quite right. Thirdly, it can effect the flight of the arrow. Because the limbs now come into place at different timings, it will push the arrow up, or down, rather than keeping it level. Some of these problems can actually be well managed. Especially if you shoot modern Olympic freestyle. For example, the issue of imbalance caused by improper tiller, can be mitigated by the use of stabilisers. So, in fact when you tune your bow and you try to get a good feel for the right balance between the limbs. Then the stabilisers will affect that. The issue of the arrow flight being affected by being pushed up or down, is actually a direct comparison to the nocking point. So, if you can’t adjust your tiller, you can adjust your nocking point. You can move your nocking point up or down to compensate for the arrow coming out incorrectly. This can also introduce other problems. If you are shooting a modern recurve, with tiller bolts that can be adjusted, you have to remember to maintain your tiller. So, if you are adjusting your tiller bolts, to change your draw weight, you have to make sure you give each one equal turns. If you want to turn it up, then make sure it is one full turn, one full turn. Or half turn, half turn. If you forget to do that and you have different rotations then the tiller will change. Also keep this in mind when taking the bow down, you might notice that the tiller bolts might be loose or you haven’t screwed them on properly. That means between sessions, your tiller will change. This can be, one of those really frustrating things that can completely ruin your score. You are shooting really well one week then the following week, nothing works right and that’s actually one of the causes. So, do keep in mind tiller bolts must be tightened and if you are changing your draw weight, make sure both tiller bolts are rotated the same number of times. For a traditional bow, you can’t change the tiller. It just comes the way it is. So when you buy the bow, you have to consider what tiller you need, for the style that you shoot. Otherwise, you may have to adapt your shooting style, for the bow that you get. This is also a problem, when you are making a bow. So, if you are making a custom bow, or you are ordering a custom bow, you do have to pass the information on. Do you tend to shoot split-finger? Three under? Stringwalk and so on. So that way, the bowyer, can make the right tiller adjustments. This can be done by making one limb stronger than the other. Or even using a shorter limb on one end. In summary, if you are a split-finger shooter, then you generally should be using a positive tiller and this is when the bottom limb is slightly heavier than the top limb. This can be measured by the difference between the limb and the string. The bottom string and the bottom limb, should be slightly closer than the top limb and string. and this difference is typically 1/4 inch to 1/8 inch. If you are shooting three under, or you stringwalk the you don’t really need a positive tiller. You might be better off with a neutral tiller. Is getting tiller right, super important? Not really. Most people can get away with having a neutral tiller or a positive tiller and the bow will function fine. But if you are getting to the intermediate, to advanced competition levels. You really should pay attention to what your tiller is. As part of your tuning. This can be a cause of your groupings not being as good as what they could be. Additionally, the argument can be made, especially for modern materials and modern recurves, that the technology and the materials are advanced to a point where they are fast, efficient and consistent. So, a slight mismatch in tiller, won’t make that much of a difference. The limbs already come together so quickly, that it won’t affect the shot that much. Hopefully that answers most questions about bow tiller. It’s not a very complex concept, but it can be illogical if you don’t think about it the right way. Anyway, this is NUSensei. Thanks for watching, I’ll see you next time.