When people hesitate over replacing a bow, the usual question is “after how many years do you replace a yumi?”
It is not decided by years. Two bows of the same age can be in completely different condition if one was drawn six days a week and the other only a few times a month. A bow is replaced according to its condition, not its age.
This page sets out the signs that make you consider replacing a bow, and how to tell whether it is time to replace it or still usable.
There are two kinds of reason
Do not mix these up. The reasons are quite different.
| Reason | What it means | How to judge |
|---|---|---|
| 1. The bow is damaged | Loss of strength (hetari), delamination, loss of nari, kogai and so on | Judge by the condition of the equipment |
| 2. The archer has changed | You want a stronger bow, you are moving from namisun to nobisun, or you want to move to bamboo | Judge by the archer |
Reason 2 is less “replacing” than “adding” or “changing over.” The old bow has not gone bad, so you can pass it to a junior or keep it for practice.
A bow in reason 1, however, is not usable even if you keep it. It is also a safety matter, so if in doubt, ask your teacher to look at it.
Signs that the bow is damaged
The bow has lost draw strength (hetari)
A bow loses draw strength as it is used. This is less deterioration than a change that comes from the material being used.
You usually notice it indirectly. The following are possible signs, not proof; the cause may be your form or your arrows, so have it checked.
- Your arrows start to land low: the same aim no longer reaches
- The bow draws more lightly than before at the same target: this can be the bow changing, not you improving
- When measured on a bow scale at a bow shop or club, it comes out lower than the marked strength
Do not mistake “it got lighter and easier to draw” for improvement. If you keep drawing a bow that has lost strength, your own sense of draw strength drifts. How to think about the right draw strength is explained in a separate Japanese-language article on this site.
The nari has gone out of shape
Nari (成) is the shape and curve of the bow. Look at the unstrung bow from the side and check whether the curve is symmetrical on the left and right. Look for twisting, or a curve on one side only.
Another sign of lost nari is that the string does not sit on the centre line of the bow when strung (the string does not run straight). A slight distortion can sometimes be adjusted at a bow shop, but if it keeps coming back, the bow is nearing the end of its life.
Delamination of glass and carbon bows
The clearest sign on a synthetic bow is delamination, where the layers begin to lift apart.
- White lines or streaks along the side of the bow, or near the tips (urahazu at the top, motohazu at the bottom)
- When you press, that part feels different
- A sound you did not hear before when you draw
If you find delamination, do not draw that bow. If you keep using it, it can break in the middle of the draw. Glass and carbon bows are the synthetic ones; bamboo bows behave differently, as described below.
Kogai in a bamboo bow
A bamboo bow can suffer kogai (笄), a split in the outer bamboo (the bamboo on the outside of the bow). The Suizan bow shop column “When to replace or repair kyudo equipment” describes it as “a state in which the bamboo splits because force is applied sideways across its lengthwise fibres.” Putting it right is said to be a major repair involving the outer bamboo, so ask a bowyer what is possible for your bow.
A bamboo bow can be repaired over a wider range than a synthetic bow, so talk first to a bowyer (yumishi) or a bow shop. “Broken” does not automatically mean “replace.”
All of these signs have one check in common. Look along the whole length of the bow in a bright place, both before stringing and after. Making this a regular habit, for example about once a month, helps you find problems earlier. The care routine is covered in Yumi Care and Storage.
Judging when the archer has changed
Here the bow is not being replaced because it is damaged, so there is no need to hurry. But if you time it well, the expense can be combined.
Raising your bow strength
If your current bow has gone soft, and you also want a stronger one, replacing it can do both at once. On the other hand, if the bow is in good condition and you only want more strength, there is value in keeping that bow (there are times when body or injury send you back to a lighter bow).
Moving from namisun to nobisun
If your draw has grown longer and the length of the bow no longer fits, the problem is size, not strength. Namisun is the standard length, and nobisun and ni-sun nobi are longer.
Moving to bamboo
Going to bamboo because a synthetic bow wore out is not a sequence we would recommend. Daily care of bamboo (stringing and unstringing, storage temperature and humidity) is more delicate than with a synthetic bow. Decide on bamboo for its own sake, not “while I am replacing the bow anyway,” and you are less likely to go wrong.
Three things to check before you replace it
What looks like a problem with the bow sometimes is not the bow. Check the following first.
- Is the string worn? A stretched string changes both your sense of draw strength and where your arrows land. See Spare Bowstrings and Tsurumaki
- Has the nakajikake become thicker or thinner? Nakajikake is the wrapping on the string where the arrow is nocked. If the way the arrow sits changes, the way it flies changes
- Has your yugake changed? If the condition of the glove, such as its thumb part (boshi), changes, your release changes. See Yugake Lifespan and Repair
These three wear out before the bow does. It is not unusual for the cause of “something is wrong with my bow” to turn out to be one of them.
After you decide to replace it
Before you go to a shop for a new bow, write down the draw strength, length and grip thickness of the bow you now use. “About the same as now” is not enough to choose by. If you have the numbers, you can compare.
- Buying used? See Buying a Used Yumi
Decide what to do with the old bow, too. If it is in good condition, you can pass it to a junior or keep it for practice. Avoid passing on a damaged bow. The person who receives it may draw it without knowing its condition.
FAQ
How many years does a glass bow last? It cannot be given in years. It varies greatly with the number of arrows drawn, storage conditions (heat, humidity, direct sunlight) and whether it is left strung. Even of the same bow, one left strung in a club room clearly wears out sooner.
How much draw strength does a bow lose? It varies greatly between individual bows, and no single figure can be given. If you are concerned, measure it on a bow scale. Clubs and bow shops have them. Judging by feel is unreliable, because it gets mixed up with your own improvement.
If the delamination is small, can I keep drawing it? Do not draw it. From outside you cannot judge accurately whether it is small or large. Have your teacher and a bow shop look at it.
If a bow breaks, can it be repaired? A bamboo bow can sometimes be repaired. A synthetic bow is said to be hard to repair in many cases because of its structure. In either case, the judgement comes after a bow shop or bowyer has looked at the actual bow.
This page is a general overview. A bow’s condition cannot be settled without seeing the actual bow. If you are unsure, always have your teacher and a kyudo equipment shop look at it. This site is an independent information site about kyudo equipment. Back to the English guide home page.