How to Measure Draw Length on a Compound Bow?

Compound bows come in many different lengths. Some of them are DIY, some are customized with merchants, and some are designed for special people. This article is about the more common mass production products.

Current compound bow handles are generally divided into two types, long handles: 25 inches, (one-inch equals 2.54 cm); short handles: 23 inches. There are generally three types of arch arms: 45 inches long; 43 inches medium; and 41 inches short.

Different combinations basically give the shooters a choice of four lengths of 64 inches, 66 inches, 68 inches, and 70 inches. Each combination adapts to a pull distance, but it should be noted that although the arm span has a certain relationship with the pull distance, that is, the longer the arm span, the longer the pull distance.

How to measure draw length for a compound bow?


Distance Measurement

However, this relationship is not absolute, so it is recommended that each shooter measure his own distance. The calculated distance is a general idea and does not guarantee accuracy. The simple method of measurement is to make a ruler yourself, it is best to use an old arrow shaft, a very long one, and mark it on the scale. After standing upright, the arms are naturally raised to the sides of the body, level with the shoulders, palms down.

Keep the arm holding the arch, pull the arm in half from the elbow to the chest, and stop at the position of your chin. At this time, using the ruler just now, experienced enthusiasts measure the distance from the archer’s thumb to the first knuckle of the archer’s index finger. For new enthusiasts, measure the distance from the tip of the index finger of the archer to the first knuckle of the index finger of the archer. The purpose is to extend a safe length to protect yourself.

After Purchasing

After purchasing an arm, there will be a label on the arm that reads the index of the arm when it was shipped from the factory. Generally, there will be something like: Medium 68 “30Ib, 28” or Medium 66 “32Ib, 28”. Meaning, this is a medium length arm, which is 43 inches. When assembled on the long handle, the bow is 68 inches long; when assembled on the short handle, the bow is 66 inches long.

Due to the difference in bow lengths, the pull force of the same arch arm on the long arch handle is relatively small. Based on the above example, when the pull distance is also 28 inches, the pull force of the long bow is 30 pounds, and the pull force of the short bow is 32 pounds. This is because the shape of the bow arm changes drastically when pulling the short arch handle, thereby generating additional resistance or storing additional potential energy.

Due to the above reasons, you must pay attention to the length of your bow when buying a compound bow, otherwise it will be higher or lower than the pull you want.

How to Measure Draw Length for a Compound Bow

Power and size

The two most important measures when choosing a bow are its power and size, because depending on our strength and openness we will choose the one that best suits us.

Power

This measurement is measured using the 28” opening standard, normally known as the AMO standard. This standard, and the way to measure it, was established in the 50’s by the Archery Manufacturers and Dealers Association (AMADA), later AMO and current ATA, in order to facilitate the selection of a bow to those who bought it in USES. Later, the other manufacturers from other countries have adopted it.

To measure the power of an arc using this standard, we will measure 26” ¼ to the deepest area of ​​the handle and then add 1” ¾ to obtain 28 ″, as shown in the diagram.

The power that gives us at that distance should be the one that marks the arc. According to the Archery Trade Association, it may have a tolerance of ± 1 #, as indicated in its manufacturer’s manual for the year 2000.

The same formula is used to measure the opening. To do this you must start by measuring from the rope, or the inside of the stock if we measure an arrow, to the same point on the handle and add 1 ”” to that measurement. Keep in mind that this will be the opening that you will have to use in the arrow selection tables along with your real power.

Size

This measurement, which can also lead to error, must be measured from the rope groove to the rope groove at the back of the arch. Knowing this, it is easy to understand why our mounted bows never measure the same as their size, although you may not believe it many people are surprised to realize it.

For compound bows we will use 3” shorter strings and for straight or hybrid 2” bows. Thus, for a 68” compound bow, the measurement of the string is 65” and for a straight or hybrid, 66”.

On this measure there is a belief that arches of a certain size are for a certain opening only. While this is true of compound bows designed for precision competition, all other bows and designs do not have to meet that rule in the same way. That is why from Lignum we recommend consulting and consulting with the manufacturer before buying a bow.

How to Measure Draw Length on a Compound Bow
Source Flickr

FistMele and tiller

In the lateral image, in addition to locating the face and back of the arch, we find two measurements that must also sound familiar to us, the fishmeal and the tiller. About the fist Mele, I invite you to read the articles that Fist Mele previously dedicated to him. A very traditional anglicism and Fist Mele II and we go directly to explain some aspects of the tiller.

The tiller

The tiller gets its name from the rod that was used to measure it, in turn this is called so because of its resemblance to a tiller or tiller, in English. In this rod the difference that must exist between the upper and lower shovel was marked.

To take this measurement correctly, we will do it from where the body melts and the shovel begins, looking for the perpendicular with the rope, as shown in the diagram.

Since the position of the hand on the bow and on the string are asymmetric so that the blades work in synchrony, they must be offset so that one has a greater distance to the string than the other. Typically, the upper blade is ¼ inch larger than the lower blade.

To adjust an arch accurately, it is necessary to take into account whether the grip used will be Mediterranean or Apache, in addition to the opening to which it will be used. These parameters make the measurement to which the arc synchronizes different. A well-balanced arc is reflected in greater precision and regularity of shot even when the release fails us.

Conclusion

I hope you found this Note interesting and have solved some doubts about the measures of the arches, if any more should arise, do not hesitate to leave it in the comments and if you found it interesting, remember to share it so that the archer culture reaches all corners of the world. planet. Good loose and until the next Lignum Note.

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