ORIGINAL: Straightarrow
Ashby himself states that a high FOC light arrow will out penetrate a low light FOC by as muc has 50%. Now, if you were going to take that light high FOC arrow and compair it to a low heavy FOC arrow where would the penetration be tha same? In an earlier post someonse stated that if I shot a 420 gr arrow I would get 1/2" more of penetration. You are taking just one part of Ashby's report and running with it. To me you are in the "The world is flat" catagory.
You need to carefully re-read the report. Take a careful look at the graph.
First, his test are in animals, not foam. Second, none of his arrows were light weight. Third, he states in no uncertain terms, that substantial gain in penetration didn't occur until around 19% FOC. None of your test arrows are even close to that. Fourth, look at the graph and notice that the 14% and 16% FOC arrows had less penetration than the 12% FOC arrows. In other words, FOC is only a benefit when it's real high. He does say that more testing is needed to finalize his conclusions on this. He does say that initial testing does suggest that only extreme FOC arrows are advantageous in penetration. None of your test arrows approached this.
The point is, your test was with normal FOC arrows where his test shows no advantage. If you manage to build a proper arrow with an FOC of 19% or greater, you will find that it weighs at least 600 grains.
My arrow is at 18%. I'm pretty sure 18% is close to 19%. Or, do you count numbers different than I do? Just because he did not test arrows under 600 gr does not mean the same principle does not apply. I'm not really sur why you keep stating it has to be that heavy to accomplish this?