Obviously, force is required to move the arrow forward off the bow and it is generated from the tension of the limbs through the bowstring. Therefore, when purchasing arrows you need to know your draw weight so you can purchase the correct corresponding spine size for best performance. Limbs stiffness is determined by the amount of force, measured in pounds, required to draw the bow to a 28” draw length as outlined in the following Archery Trade Association (ATA) standard.
AMO BOW WEIGHT STANDARD
For Conventional Bows
Bow weight is the force required to draw the nocking point of the bow string a given distance from the pivot point of the bow grip (or the theoretical vertical projection of a tangency line to the pivot point parallel to the string). Draw length from pivot point shall be designated as DLPP and shall be referred to as TRUE
For the purpose of uniform bow weight designation, bow weight is the force required to draw the bow string 26 1/4” from the pivot point. This weight will be marked on bow as being taken at 28” draw (26 1/4” plus 1 3/4” = 28”) See DRAW LENGTH STANDARD.
EXAMPLE: Weight Adjustment Range: 45/55 lbs. Weight Set At: 50 lbs.; Hold 32 lbs. Draw Length Range: 29” – 30”
EXPLANATION: The pivot point is a more realistic measuring point (when compared to the variations of profile of the back of bows at the handle section) for establishing bow weight since the pivot point is a constant in all bows as well as the contact point of the bow hand from which the true draw length is generated.
The 26 1/4” DLPP is the approximate equivalent of the 28” draw used previously on the more massive wooden handle bows.
Therefore, your draw weight is a combination of your draw length (See Arrow Series – Part 2 Measurements) and the combination of your riser (23” or 25”) and your limb stiffness (15#-50#).
For example, a 25” riser with a 34# long limb produces a 70” bow with a draw weight of 34 pounds at a 28” draw length. If these same limbs were used on a 23” riser, the combination would produce a 68” bow with a draw weight of 36 pounds at a 28” draw length.
However, not everyone has 28” draw length, especially young archers whose draw length will change progressively with growth. So as a rule of thumb you can add or subtract approximately two pounds for each inch your draw length is over or under the 28” standard.
Using the previous example, if an archer has a 26” draw length and uses a 25” riser with 34# long limbs it will produce 30# of force at full draw OR uses the 23” riser with 34# long limbs it will produce 32#.
This is very important to select limbs that enable you to develop and compete however do not cause long-term physical damage. When purchasing limbs you need to determine if the limbs are too heavy, you can try this simple 7-second challenge.
- Draw the bow to the anchor
- Hold seven seconds
- Let down without lowering your hands, stay in set-up position to take a 2 sec brake,
- Repeat several times.
If you cannot do it properly then the limbs are too heavy for you. If you find this challenge extremely easy, you can look at heavier poundage limbs, if you choose.
Now you understand draw weight and used in combination with your draw length you can see the arrows that match your equipment using a manufacturers arrow selection chart. In the up coming blogs we will try to examine the arrow spine, flex and stiffness.
I think it would be more accurate to say that the force required to propel the arrow is generated by the archer’s muscles, but stored in the limbs of the bow.
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