I have 54lb widow with bamboo limb cores. I bare shafted a bunch of woodies and ended up with a cedar that spined at 76, 145gr point, and 29.5" long. It showed slightly week on bareshaft testing but once finished, sealed and fletched it flew great with any BH I put on it. I wanted to try some laminated birch so I ordered some 75-80 spine from a reputable dealer, cut them to the same length as my cedar and bare shafted them. They showed extremly week. I cut a half inch off and dropped the tip down to 125. Still showing weak. I can't understand why if they are both the same spine, the lam birch won't fly the same. Could it be the weight difference?? the birch arrow is 100grs heavier than the cedar. Any input is greatly appreciated. One note: I don't have a spine tester, and I know the cedar shafts are the correct spine. They were tested by a friend!
Chuck, you made the fatal error in tuning. You always verify with point weight before you cut. Odds are the arrow were WAY over spined and the tail of the arrow is hitting the shelf/sight window giving you a weak indication when the opposite is true. By cutting you've made the problem worse. The key to this stuff is if you make a change and don't see a change, you went the wrong way. You can't trust that a spine that works from one batch of arrows will do the same from another, there's too much variation in wood densities, diameter, and probably several others we don't even know about. Go up in point weight, since you've cut them, you may have to go up a lot..O.L.
First off, it's important to check the spine on a scale. You don't always get what you order. I've had some shaft makers tell me that one needs to go with a higher spine with hardwoods compared to cedar. Don't understand the dynamics behind it, but it has worked for me. I've shot 10#-15# higher in hardwoods than I do in cedar, and they worked fine. Didn't have to go that high to get good arrow flight though.
Thanks for your help guys. I'm gonna try again with a full length shaft and much heavier point and work from there. It makes sense the arrow hitting the shelf!