Iv been playing around with the stu miller calculator with different length of alloy footing to change the dynamic spine of my carbon shafts and I was just wondering if any one has done this before. The main reason I want to do this is I want my arrows to be a set length and weight so I don't want to drop point weight or shorten the shaft to increase the dynamic spine but by putting 6" of alloy footing on the carbon shaft I can dubble the dynamic spine of the arrows I already have with out having to buy new arrows
Thanks in advance for any input
Cheers jim

Sounds like over kill to me. I know you don't want to buy new arrows but I have found that what works for me is getting the shaft that works best without footing and then add  just one inch of footing so the spine is not affected at all. If you find a correct length that gives you the stiffness you need I would try to use some sort of internal footing (a hardwood dowel) to arrive at the same outcome.

I have found that it doesn't work. I have added up to 5" of footing. The arrow acted like I just added weight to tip, making the dynamic spine weaker. YMMV.

The internal or external support (footing) lowers the dynamic spine unless it is long enough to stiffen the Arrow's ability to bend. I could increase spine with an internal carbon shaft that extended just past the halfway point of the arrow (front half, so 16" or more). Short pieces only added weight up front and lowered the dynamic spine. - Jay

I have tried it and did get the results i wanted but it created a small "bump" in feel and  arrow movement as i drew the arrow and the back lip of the footing came across the shelf. This was a distraction to me so off they came.

Rick, try (if your arrow will allow) putting an internal piece in, gluing it with gorilla glue. No bump. - Jay

Wouldn't adding internal or external footing over six inches(depending on arrow length) cause the arrow to bend(paradox) at the last 3/4's of the arrow only, causing unstable arrow flight. And wouldnt that create a weak point during paradox at the end or the footing(internal or external)? Just asking

Timothy, it doesn't seem to, once you get past the center of the arrow. I did the work to build the arrows with an internal shaft full-length, got those to fly bare-shaft perfect. This was to get a very heavy arrow (over 1,000 grains) for my 80# bow. Then, to achieve Extreme FOC, I began to cut down the full internal shaft to 3/4, then 2/3, finally ending just about 3/5. For each of these arrow types, I was able to achieve perfect bare shaft flight. I think that once you "fix" the center of the shaft, where the natural inclination of archer's paradox is to concentrate the force, you achieve an increase in relative (and actual, as I measured it) spine. This whole project, done for one buffalo hunt, took nearly a year. The arrows flew perfectly, and my wife and I each took water buff with longbows in Australia. - Jay