So I've been fiddling with my new (very old and well used, but new for me) fletching jig and the tomatoe stakes from the garden center. I've weighed out the 4' lengths to get what I think will be around 525 grain arrows when finished.
I found that the shaft diameter varied greatly for the same measured weight (actual raw shaft weight). Straightened all the arrow shafts, and this weekend I measured the deflection of one of my existing hemlock arrows that shoot well. I cut 15 arrows to match that deflected shape, but did leave them a bit long for now.
Cut nocks, and fletched up 5 arrows on Saturday. Then I hit a brick wall. You see, I'm still confused about tomatoe stake spine and weight forward effects of taper - and if my boo can even be considered to be tapered? (perhaps it's tonkin?).
On my existing, good shooting, arrow - I measure a spine of 45# (i.e. 0.625" deflection at center) It is cut to a length of about 29.5". So that should make the corrected spine about 7.5# less. That leaves me at 37.5# spine which works out to 10# less than my bow. Good enough I think, except that when I cut my bamboo to a length of 31", it still feels much stiffer than my good shooting arrow did at 29".
I did a bunch of searching on the site, and found good stuff. Anyway - the point of this post is to quote Justin and ArtB. I found the following in a post from 2007, and thought it was good to bring it current. I found it helpful, and although the concept is simple - I guess I needed a reminder.
"If you cannot understand the way length changes spine, try this. Take a new pencil and grab the ends and break it. Now take one of the pieces and grab the ends and break it. Now take one of those pieces and grab the ends and try to break it. It is still the same pencil diameter. Still just as tough/weak as it was when it was full length. But because it is shorter it SEEMS tougher. The arrow is the same way. You cut it shorter and it reacts different even though it is the same arrow. Justin"
"Point weight is an issue also....if replacing a 125gr point with a 145gr point subtract 5#. For 160gr, 175gr, 190gr etc, add or subtract one spine range for each weight change. - ART B"
"Here's how I handle the problem of weight forward on cane/boo shafts. I allow 10# for the shaft's natural taper and start a couple inches longer (for spine adjustment) then needed to begin with. I then find the center of the shaft and mark that. Next I balance the shaft on a pencil to find it's balance point. I then measure the distance between the two marks and then adjust the spine 5# for each 1/2" of difference. Example: If the marks show 1" difference between them then that additional 10# pounds I first added compensates for the difference and no additional spine would be needed (this is where that extra 2" of shafts length we started with would be used for spine adjustment if needed). That's seems to work really well as far as getting a good spine match in a set.-ART B"
