I'm playing around with Stu Miller's Spine Calculator because I'm going to foot some carbons with aluminum. When I do the calculations for adding a 2" footing at a total of 24gr it increases my spine by 6.4 pounds. I'm confused by this, I figure adding 24gr up front should weaken the spine and I don't see how only 2" of footing could cause any increase in arrow stiffness, due to the fact that I don't see those first 2" having any flex to begin with.
What is everyone elses thoughts on this?
The added weight would weaken the spine, but 24 grains shouldn't matter much, and a 2 inch footing shouldn't make any difference either. Except give you a pretty tough stumping/small game arrow.
don,
Those are my thoughts also, but the calculator show an increase in spine by over 6 pounds.
Why not foot a bareshaft before fletching and see how it compares to the same bareshaft with no foot? I use just a one inch piece of aluminum on my carbons and they shoot the same as the non-footed arrows fletched. I would be interested in your results compared to Stu's chart.
Send Stu an email and ask what he thinks on the question. I believe the calculator is wrong. I have used 1 inch thru 4 inch footings and have seen no real appreciable difference in spine for the same arrows. The added weight weakens them a bit as the foot length increases.
I've had the same results. No noticable change in spine either way.
Troy
I think the "theory" is that by sleeving the front 1 inch or 2 inches or what have you, you are making that portion much stiffer therby effectively shortening the shaft by that amount. Now instead of a 29" shaft flexing upon release you have a 28 or 27 inch shaft flexing upon release. I don't know if it makes a difference or not. I foot mine prior to starting my tuning and take length off the back end and play with point weight to dial it in.
It is weight added to the end so weaker acting arrow. If the footing is real long and gets on the rest that, could change things a little moving the center of the arrow out a little.
I would think the last few inches of a shaft bend, but so little I do not think you can even measure it without some very sophisticated equipment or measurements.
I have seen some noticeable change due to footing, insert and point changes where the combination was the same weight as a light inserted, no footing and heavier point, but the insert and footing moved more of that weight in back of the end of the shaft.
I think it increases the spine a little because there is that much less arrow to flex when shot therefore even though you are adding weight it is also like shooting a shorter arrow.
I just footed some 55-75's with 2" of 2216. I can see no difference in flight whatsoever. Most of the footing is over top a stiff glued-in insert anyway.
I like Stu's calculator but dont understand the footing part.
Rob
I tried a long (4") footing. Just acted like extra weight. Made my arrows shoot weak.
I tired some 3 inch footing on my carbons also. When I bare shafted them, it made my arrows shoot weak; just like what Prairie Drifter said.
the only way footings could inhibit the shaft's ability to flex would be if it were longer than the internal inserts which on the Easton/Beman Axis/MFX and others with the H.I.T.system would mean pretty long footings. These "calculator" systems sometimes are off by more than a little.