Well, it’s a long story and I will go off topic even more… maybe the moderator could move this into a more appropriate topic. So, here is my take at it:
I must say first that I can only speak for SMG bows, carbon laminated, artificial horn version. I only shoot two YMG and two Kaya bows, and found them to be about the same, but I did not shoot them for a long time in order to get a better comparison between the makers. Also, the force-draw curve looks almost the same.
In 2009 I bought my jung-gung, 49# at the same time with a friend who got a 50# jang-gung. At the time I didn’t notice the change, but after shooting side by side it was clear that his trajectories were lower. When I measured the bows draw-weight curve, it became clear why. Then I tested both bows with a chronograph and found out that the jang-gung was about 10fps faster.
First, compare the measurements in this thread paying attention at the 49# jung-gung and 50# jang-gung: http://www.koreanarchery.org/punbb/viewtopic.php?id=232
The curve of the jang-gung is better up until 28 inches, and from that point on the bows have almost the same curve. Actually, the shorter bow stacks a tiny bit more. Also, I calculated the total energy and the jang-gung had between 5 and 10% more energy stored. Efficiency came somewhere between 65 and 80% for both bows, depending on the type of release: snap or holding for 2-3 seconds. The jang-gung had of course better efficiency by about 4% to 7%.
In terms of feel, I could say that the longer bow feels indeed stronger in the first 10 inches or so, but after that I could not really make a difference. Overall, I find the longer version nicer to draw, because you need to apply more force all the way, while still being smooth. It is actually smoother after you pass the first 7 or 8 inches.
As for reliability, I can only speak from experience on my 49# SMG jung-gung. In 3 years it shows no sign of defects. I shoot for about a year at 33”-34”, then dropped to 32.5”, used it in rain, shoot 6 gpp, I applied excessive torsion in the handle, I’ve hit once an object with the lower siyah…the bow is still shooting great. With the jang-gung I shoot regularly with 6-7gpp and this bow is a “wonder” to me, especially after the accident it had. I would really like to know what kind of glue they are using.
The tricky question is about higher vs lower weights. After doing all those measurements (see the thread mentioned above), I brought the curves of a stronger and lighter bow on the same scale and it became obvious that as the draw weight increases, the bow stacks less and preloads better, having a more level curve, which of course, is better.
For lower poundage (50# @ 29”), I would say not to worry about bow lifetime, except if the bow has some manufacturing or material issue. Most problems I have heard of are breaking of the carbon fiber on the back of the bow. The artificial horn versions are the most reliable though. Still, I have heard of higher poundage bows having a bit more frequent issues. I’ve not measured exactly but I have the impression that the carbon fiber on the back is the same thickness for all bows, and just the core differs in thickness. If this is true, maybe the stronger bows are reaching closer to the carbon fiber tensing limit, causing a break there. From this point of view, it would be better to have a longer bow with a shorter brace height if one wants to stress the limbs less. So from a technical point of view, the longer bow should be more reliable at long draws. Personally I would like to see a bit more width in the limbs in the high pound bows, maybe just 3mm or so, as this would make them a bit more stable and reliable, but a bit slower too. Anyway, this is speculation as I have not measured the carbon fiber thickness in stronger bows. I would be curious to see one of the stronger bows that were recently ordered on this forum.
In stringing I have not found any differences. After all, there is just one inch difference between the two. As for stability, I think it depends a bit more on luck. They are pretty flexible though and can be corrected with a bit of heat. More width would help improve stability, but sacrifice speed.
I recently tried to acquire another jang-gung, but since it was not available at the time I received another jung-gung, “korean tiller” SMG. This 2012 version is different from the 2009 version. The top limb is more curved and a bit stronger and the difference between the top and bottom limb is higher. Although I have not measured it yet, I can feel the first inches stronger, but still not as good as in my jang gung (2011 version).
The good news is that the bowyers are constantly improving the bows so I guess it’s becoming easier to get high poundage bows these days.
