Korean Target Size

[Thomas Duvernay]

Here is what I posted on the LeatherWall:

Here is one for the mathematically inclined LWers.
In Korean traditional archery, we shoot at a distance of 145m (159 yds.). Our target is 2.67m H x 2m W (8.76' x 6.56'). Because of the long distance we shoot, people in some countries cannot find a place suitable for practicing. If one were to decrease the distance, what is the corresponding decrease in target size (and possibly bow draw weight)?

Would the decrease in target size be equal to the percentage of decrease in distance? For instance, if the distance was decreased from 145m to 100m, would the target dimensions decrease by 31%? What about bow draw weight?

T

and, when some points were not completely understood by members:

Not meaning to re-state a cliche, but size does matter...
The idea is to make hitting the target at shorter distances relatively difficult.

The size of the Korean target at 145m was set by the Korea Archery Association over forty years ago. Hitting the target anywhere on the face is one point; the center does not matter. Needless to say, if you have a 2.67m x 2m target at 145m or 45m, it does make a difference (at 45m, it would be somewhat like hitting the broad side of a barn).

As for the bow's draw weight, if you are shooting at a target 145m distant, your trajectory will be different than shooting at it at a shorter distance. For example, archers shooting a 35# bow will have about a 45 degree angle trajectory to send the arrow that distance; at a distance half that, a 35# bow would have its trajectory lowered. In order to keep an approximately similar trajectory, the draw weight would need to be lowered (by how much would be the question).

T

The best answer I received was this:

I'm not going to do the math for you but I will explain the logic IMHO.
In order to simulate the experience of long distance shooting at shorter distances not only does the target size have to be progressively smaller the closer it is to the shooter but the weight of the arrow has to be progressively heavier. That will ensure that the the archer has to change his point of aim. The weight of the bow does not need to be changed.

As for the target size the picture should be explain itself. Determining target size will be a breeze compared to determining the arrow weights needed. Then you also have to tune them to the bow. Same length arrows but heavier weights. Determining spine shouldn't be a big problem. If you measure the spine/deflection of a properly tuned arrow you can use that as a guide for heavier arrows.

The biggest math problem is going to be determining the proper weight of a particular arrow used for a particular distance in order to get the needed required point of aim the same for shorter distances as it is for the longer distance.

He also included a graphic to illustrate his point.



Discussion? Ideas?


T

[Thomas Duvernay]

Link: http://leatherwall.bowsite.com/TF/lw/th ... CATEGORY=5

[Bede]

Isn't something like the inverse square law applied when calculating the apparent size of objects? Rather than a straight line, the graph may have to be a parabola.

Increasing the mass of the arrow will also increase its kinetic energy with the same weight bow. There for it would hit harder. Perhaps adjusting your aim would be simpler.

[Thomas Duvernay]

Bede,

I guess the reason for either lowering the bow draw weight or putting weight on the arrow would be to simulate the angle necessary to hit the target if it were at 145m. I can attest to what happens when you shoot at Korean-sized targets at short distances (50m) with the same draw weight bow you would use at 145m--I not only hit the target easily, but I also put the arrow half-way through it.


T

[Bede]

Thomas,
I don't doubt you. My Korean bows deeply penetrate western targets at 50 metres and fellow shooters complain about the difficulty of pulling them out. Due to the stress on the arrows, I only use modern arrows for these events.

[M Hardman]

I've never heard of penetration like that from a low weight bow before
I know in the indoor season we use 40 cm faces at twenty yards to simulate the longer distances (60-80yrd ish perhaps). As difficulty is (in my opinion) rather unquantifiable, I doubt you can be exact without extensive testing.
You could take one consistent archer and shoot at the 145m target, register the number of hits and get an average number over a few shoots.
Then try to emulate that score at a lower distance with different bow weight target size, etc.

Mike

[Bede]

The penetration is only about 12 inches. The arrows have a lot of friction when they are withdrawn.

[Bill Metcalfe]

I brought home one of the modern bows made there in Korea. I use arrows that were made for a much heaver draw weight and fine that the 50# bow sends tha arrows so far into a makinze 3D targer that I break about half of them trying to pull the bow is a real shooter I do not get that kind of penetration with the 65# hunting bow that I normally shoot the changing ov the draw weight is bound to change the entire style and i see no way that it will be usable for practice purposes that is just my 2 cents worth. I am already looking forward to making the trip next year. Live well and help others live well Bill