Let’s look at 2 terms here:
Brace height: It is the measurement between center of the riser and the string.
Tiller: is the different between the measurement of string from upper limb and measurement of string from lower limb.
So, tiller = (upper limb to string distance) – (lower limb to string distance)
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Where is bow tiller measured on the bow
For one-piece bow, you measure that distance where the limbs begin to curve.
For a three piece takedown bow, it is actually very easy. It’s from where the limb connects to the riser.
Read: Archery Glossary 101
What kind of bow tillers are there?
Neutral tiller: When the difference between the top limb and bottom limb is zero, that is, there is no difference between top limb and bottom limb distance from the string.
Positive tiller: When the difference between the top limb and bottom limb is positive, that is, top limb is far from the string compared to the bottom limb. Most modern recurve bows are with a positive tiller.
Negative tiller: When the difference between top limb and bottom limb is negative, that is, top limb is closer from string compared to the bottom limb.
Note: on an average there is 0.25-0.5 inch positive tiller used on most modern bows.
Mechanism of the bow
You might be wondering why even have a gap or a difference between the limbs?
Aren’t bows supposed to be symmetrical?
This is because of the design of the bow.
You hold the bow (riser) at the exact center. That’s where the ‘rest’ of the riser is built. Then you place the arrow above it.
Now if you pull back the string at the exact center then there is no need for a tiller. But if you are using split finger technique (most common in competitive and contemporary archery), then you are pulling the string from a bit higher point compared to the center.
Think of it this way. If you are pulling the string from a higher point than center, then top limb is closer to you than bottom limb. Thus, it snaps back faster than the lower limb.
So, essentially when you pull back the arrow, you are putting uneven force on the limbs.
On an ‘neutral tiller’ bow if that is done then top limb snaps back faster than lower, and thus some energy does not transfer to arrow correctly.
What happens when you pull back string from an uneven position?
- Vibration: It causes unneeded vibration in the bow. When the limbs don’t snap back simultaneously, the remaining energy in the limbs do not cancel each other out properly, and thus causes excessive vibration in the bow.
- Imbalance: You will feel the bow is not balanced correctly. Bows only feel ‘right’ when they are symmetrical and thus provide even resistance. But with uneven draw the bow might be pulled upwards or downwards when you reach full draw. This is because you might be having too much tension in one limb compared to the other.
- Flight angle of the arrow getting affected: Because the timing of the limbs is different, it will push the arrow up or down, thus affecting your accuracy.
Why bow tiller is used?
To compensate this, tiller is used. A slight difference between the limbs helps them to snap back in a more synchronized way.
It brings balance back to the bow and resolves all the problems mentioned above.
Second use of the tiller has is to slightly change draw weight of the bow.
Tiller bolt basically change the angle of your limbs slightly so that the limbs either move towards or away from the string. This makes the limbs heavier or lighter in draw weight.
Tiller bolts can’t drastically change the draw weight. But they can adjust the draw weight in the range of 5-10% upwards or downwards.
Tip: In case you want to change your draw weight more than 5-10% permissible by tiller, you may need to change the limbs of your bow (in case you are using a takedown bow).
Should tiller be used in every kind of archery and with every kind of bow?
In general, only a very slight positive tiller is required to tune a bow correctly.
For most archers this won’t be very noticeable. Even if an average archer avoids obsessing on tiller, he or she won’t find any major issue with their archery.
For intermediate and advanced archers however, who participate in tournaments, tiller becomes increasingly important.
That being said, there are cases where you don’t need a tiller.
- If you are using 3-fingers-below the arrow to pull the string, you can avoid using a positive tiller. Meaning, neutral tiller will work fine for you. Reason being, you are pulling the string at the center, or very close to center to have any uneven force distribution on the limbs.
- If you string walk, then definitely don’t get a positive tiller. You can even consider using a negative tiller in this case. (See ‘related questions’ section below the article to know more about string walk).
Is bow tiller the only way to get rid of this issue?
What if your bow doesn’t have a tiller to adjust? You will still face he issues mentioned above, but you can mitigate them by some other ways as well.
Stabilizer weights: Stabilizer weights can be used to compensate for the imbalance and vibrations. They can effectively mitigate any imbalance in your bow, as well as between the limbs.
Changing the nocking point: Where you pick your nocking point can also help you get rid of the issue of uneven draw, or of flight of the arrow getting affected. You can adjust your nocking point to compensate for any upward or downward release of your arrows due to improper tiller or imbalanced limbs.
Dampeners: You can also use dampeners for limbs to get rid of any excess vibrations in your bow and limbs.
Adjusting the bow tiller
If you are shooting a modern bow with adjustable tiller bolts, always remember to maintain your tiller.
There are two rules to it:
Rule #1: Follow symmetry when adjusting the tiller of upper limb and lower limb.
If you are adjusting the draw weight by using tiller, make sure to give equal turn to both top and bottom limb tillers. For example, a full turn on the top limb shall be followed by a full turn on bottom limb.
Rule #2: Tighten the screws routinely so that they are not loose.
Loose tiller bolts can change your tiller. That affects the consistency of the bow and will result is erratic shooting experience.
What is a string walk?
String walk is an advanced archery technique where an archer pulls the string using 3-fingers-below, however, they pull it from even lower position on string to compensate for the distance to the target.
String walk is commonly used by hunters. From where you pull the string changes the trajectory of the arrow.
For example, if your bow and stance is tuned to shoot accurately at 50 feet, but your target is at say 100 feet, you can string walk and use the same stance to shoot accurately at 100 feet as well.
This is generally done by pre-measuring how much you need to move your fingers down the arrow to compensate for a particular distance.
Archers using this technique measure and mark their string, or use the stitches of their glove/finger tab to measure it in real-time. But they have an accurate picture of how much they need to string walk for various distances.
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