Broadhead info from Mag.
09-10-2004, 09:41 AM
#1
Thread Starter
Join Date: Sep 2003
Location:
Posts: 83
Broadhead info from Mag.
Ever wonder how everyone seems to claim that they “Fly like a Field Point”? First off, there is no government agency called, “Department of Archery” or the “Broadhead Trade Commission”. No one in this industry polices the rampant and wild claims in advertising. The top publications never, ever seem to slam any well-advertised product in a review for any reason. Even if that product doesn’t work as claimed.
If I were to go over all of the aerodynamic issues broadheads deal with, this segment would be 20 pages long. So, let us get a couple well-known aerodynamic laws out on the table: A sharp leading edge is NOT stable in flight. Look at any aircraft wing and you’ll see a nice radius leading edge with a taper to a sharper trailing edge in back. This alone should tell you that any fixed blade design is already in trouble. The obvious problem is we can’t hunt very well with dull blades with a nice 1/16” radius in front with sharp trailing edges. The fixed blade would fly faster and straighter this way, but severely affect its ability to make a humane harvest.
Just like aircraft or birds, the fixed blade design has yet another issue; total surface area. The smaller the surface area, the less drag you have and the faster you go. Most important is the surface area of the blades themselves. Forget the ferrule for the moment; it’s very happy riding behind the split air stream the tip created. The blades on the other hand are dragging themselves through unstable turbulence the sharp leading edge created. The more blades you have, the more averaging of this turbulence takes place. This may sound like a good thing until you realize that the more blades you have, the more blade area is exposed, the more aerodynamic drag you get. This drag at the front of the arrow causes unstable flight and a more rapid speed drop than fewer/smaller blades. Forget about blades that have a large cut out (or window) areas in them (mostly there to save weight, not fly better). Even though the exposed blade area is less, there is even more turbulence caused by the “open window effect”. What’s a Bowhunter to do? You could go to a baby stubby broadhead with very little blade area and get some (I said some) accuracy and speed back, but the wimpy cutting diameter is scary and if you were that good of a shot and liked tracking game forever and a day, a field point could kill too.
Let’s not just pick on fixed blades here. Almost all mechanicals claim they fly like a field point. I don’t know what kind of field point they use as a reference, but if they’re using a standard bullet nosed point, they are far from the truth. Just because a lot of the mechanicals have most of their blade area hidden, does not mean they fly like field point. Most Bowhunters are not good enough to shoot a one inch circle group at 40 yards like the X-Ring test machine, so anything that even groups in the target must be just as good. If any mechanical has its blades facing forward, or trip levers near or at the tip, you have an instant recipe for unstable flight and uncontrolled turbulent air thrown all around the rest of the broadhead and arrow. Is it most likely better than the fixed blade for flight? Yes, but that by no means is field point accuracy or speed.
In the next segment, we’ll cover “Speed and Energy at Target” and why everyone only talks about speed out of the Bow!
If I were to go over all of the aerodynamic issues broadheads deal with, this segment would be 20 pages long. So, let us get a couple well-known aerodynamic laws out on the table: A sharp leading edge is NOT stable in flight. Look at any aircraft wing and you’ll see a nice radius leading edge with a taper to a sharper trailing edge in back. This alone should tell you that any fixed blade design is already in trouble. The obvious problem is we can’t hunt very well with dull blades with a nice 1/16” radius in front with sharp trailing edges. The fixed blade would fly faster and straighter this way, but severely affect its ability to make a humane harvest.
Just like aircraft or birds, the fixed blade design has yet another issue; total surface area. The smaller the surface area, the less drag you have and the faster you go. Most important is the surface area of the blades themselves. Forget the ferrule for the moment; it’s very happy riding behind the split air stream the tip created. The blades on the other hand are dragging themselves through unstable turbulence the sharp leading edge created. The more blades you have, the more averaging of this turbulence takes place. This may sound like a good thing until you realize that the more blades you have, the more blade area is exposed, the more aerodynamic drag you get. This drag at the front of the arrow causes unstable flight and a more rapid speed drop than fewer/smaller blades. Forget about blades that have a large cut out (or window) areas in them (mostly there to save weight, not fly better). Even though the exposed blade area is less, there is even more turbulence caused by the “open window effect”. What’s a Bowhunter to do? You could go to a baby stubby broadhead with very little blade area and get some (I said some) accuracy and speed back, but the wimpy cutting diameter is scary and if you were that good of a shot and liked tracking game forever and a day, a field point could kill too.
Let’s not just pick on fixed blades here. Almost all mechanicals claim they fly like a field point. I don’t know what kind of field point they use as a reference, but if they’re using a standard bullet nosed point, they are far from the truth. Just because a lot of the mechanicals have most of their blade area hidden, does not mean they fly like field point. Most Bowhunters are not good enough to shoot a one inch circle group at 40 yards like the X-Ring test machine, so anything that even groups in the target must be just as good. If any mechanical has its blades facing forward, or trip levers near or at the tip, you have an instant recipe for unstable flight and uncontrolled turbulent air thrown all around the rest of the broadhead and arrow. Is it most likely better than the fixed blade for flight? Yes, but that by no means is field point accuracy or speed.
In the next segment, we’ll cover “Speed and Energy at Target” and why everyone only talks about speed out of the Bow!
09-10-2004, 09:48 AM
#2
Nontypical Buck
Join Date: Feb 2003
Location:
Posts: 2,994
RE: Broadhead info from Mag.
Look at any aircraft wing and you’ll see a nice radius leading edge with a taper to a sharper trailing edge in back. This alone should tell you that any fixed blade design is already in trouble. The obvious problem is we can’t hunt very well with dull blades with a nice 1/16” radius in front with sharp trailing edges. The fixed blade would fly faster and straighter this way, but severely affect its ability to make a humane harvest.
If broadhead were similarly designed, I would fully expect it to do the upside down version of archery... You'd have to aim really low
To me, when I see that claim, it means if I do my part (form, tuning, etc) the head will impact the same place as a like weighted field point. I'm not too concerned if they don't literally face the same aeordynamic consequences...
09-11-2004, 03:36 AM
#3
Nontypical Buck
Join Date: Feb 2003
Location: Vinton VA
Posts: 2,978
RE: Broadhead info from Mag.
I will agree that no broadhead will fly like a small field point everytime, but the smaller/short/low profille heads will group with field points for the most part with minimal fletching control. Even out of less then perfectly tuned bows. I am sure a "hooter shooter" or similar device can tell the differnce, but most bowhunters could not. Many broadhead mfg claim "field point accuracy" but they don't really say what they mean by it. It's all marketing, but I have found several fixed blades that will shoot well even with mismatched arrows, striaght fletch, and un-tuned bows. They are all short, low profile heads that seem to maintain similar FOC as field points of the same weight.
