This concept occurred to me too, but i'm not sure if the arrow rotation provided by the fletching would contribute more to the arrow's penetration than a straight drag of the arrow with no rotation that you'd get with a spinning insert. Need some testing.
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Heavy arrow build thread
- Thread starter DanielB89
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GTel
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That makes a lot of sense. Might allow the arrow to steer the broadhead better if spinning faster without causing additional drag from the broadhead. On the contrary, it could potentially cause more planing if the broadhead isn't spinning as much. Only testing will tell.
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deertrout
Well-Known Member
Yeah, that's kinda where my little brain was telling me this would go. I've had my archery mentor's voice stuck in my head for over 20 years when he preached, "you gotta spin the arrow!" to prevent wind planing with 2 blade cut on contact heads. Maybe with the better understanding of bow tuning we have now where you can get a bow shooting darts without fletching even glued on yet, that isnt so much the case, but I still think you gotta spin the arrow.
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Yeah, I'm not sure if that's good or bad. When i shot fixed i always used a strong helical fletch to spin that head.
Here is the response I got from Rob Neilson of the Ashby Bowhunting Foundation.
I stand corrected on my theory that there could be some level of energy transferred to a single bevel head due to arrow rotation. Apparently not.
I still wonder where the energy, (how ever minimal it may be) of the rotation of a shaft goes upon impact.
But it seems that a spinner insert would not contribute in any way to our efforts to increase penetration.
Mr. Tom:
I would say the centrifugal force of the arrow in flight would not contribute on impact…your arrows Momentum is what drives the arrow through on impact and that is where the 12 factors come into play…structural integrity, perfect flight, etc. Take one of your arrows, spin it, then grab it in two fingers while it is spinning and see if it keeps spinning. The feathers on your shaft act as an arrow stabilizer by inducing drag and causing the arrow to spin. This improves accuracy and helps correct imperfections from the shooter. If you had a left bevel head with right wing helical…they would fight against each other creating a floating effect of your arrow in flight. Always match your bevel and your helical, i.e., left bevel with left helical, right bevel with right helical.
All things equal a spinner insert will not increase your penetration. I will say with moving parts – and not all equipment manufacturers are equal – they would be more prone to damage/breakage than comparable solid inserts. I will say if your bow is tuned and you have proper arrow spine/broadheads – you can achieve perfect flight with a wide range of arrows/broadheads. The apathetic excuse of I use this because it flies the same as my field point…many times the bow is out of tune, could be the arrows and broadheads are under-spined as they are trying to be light and fast and the bow is too efficient for the shaft they are pushing, could be they did not bareshaft or nock tune their shafts, could be the shooter and not the bow/arrows at all, or other issues.
I have my bow set up where I can shoot from 525 grains to over 1300 grains….all fly perfectly as I dialed every arrow in to that bow after I tuned the bow. A bow is either tuned…or it is not. My personal set up for everything from small through large game is 675 grains total, 340 grains of head, insert/outsert/footing up front that gives me 25% FOC. I shot a bull nilgai with this set up on an almost full frontal at just under 40 yds, hit the scapula/humerus joint perfectly, split the bones, split three ribs, penetrated lungs, liver, stomach, intestines and lodged in the pelvic bone. 5’ of penetration after penetrating/splitting the heaviest bone on the animal.
Hope this helps and do not hesitate to contact us…we are here to help all bowhunters be successful, ethical and lethal!
Thank you,
Rob
I don’t know who Rob Neilson is but I agree with his points. Although the amount of helical will speed up or slow down your arrow, I can’t see the actual spin of the arrow being transferred to any measurable (or useful) energy upon impact. Also his point about the bow being tuned or not is spot on. I can shoot any weight arrow through my Halon 32 and it flies perfect...assuming the spine isn’t too weak.
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I went to the Ashby studies and reread the Single bevel section. This has been stated a couple times above, but this provides a good example of why a single bevel rotates -
“Why do single-bevel blades rotate? If you happen to have any kitchen knives with a single-bevel edge, give this a try. While keeping the blade's width absolutely vertical, try cutting a thin slice off a big roast or ham ... or even a sizable chunk of cheese or a big tomato. What happens? The knife blade 'walks' to one side; the side opposite the single bevel. The cutting edge is deviated by the pressure the meat (or whatever it is your slicing) is exerting on the blade's bevel – and which isn't being off-set by having an even amount of pressure 'pushing' on the other side of the blade (the side with no bevel).”
And further down:
“Because the tissue's 'push' on the broadhead's bevel is not met by any 'tissue push' on the opposite side of that individual blade's edge, the edge is shoved sideways; just as the knife's blade edge was when it made that 'walking cut'. Since a broadhead is piercing the tissue, and both its edges are being forced sideways (in the same direction) the broadhead rotates as it move forward.”
Further down are a number of examples of single bevel performance through various bones, including pictures comparing single and double bevels. He also performs a test using potatoes and a “free-rotating shaft”, showing a single bevel splitting a potato just by pushing it through.
Since it doesn’t appear that the arrow shaft is assisting the rotation (other than pushing the broadhead forward), you may get slightly better rotation of the broadhead since it doesn’t have to also turn the arrow. Just a theory though, would need to see test results.
I’m sticking with the static inserts for now, I don’t like the idea of introducing a moving part into my arrow.
Here’s a link to the full write up - https://www.tuffhead.com/why-single-bevel
“Why do single-bevel blades rotate? If you happen to have any kitchen knives with a single-bevel edge, give this a try. While keeping the blade's width absolutely vertical, try cutting a thin slice off a big roast or ham ... or even a sizable chunk of cheese or a big tomato. What happens? The knife blade 'walks' to one side; the side opposite the single bevel. The cutting edge is deviated by the pressure the meat (or whatever it is your slicing) is exerting on the blade's bevel – and which isn't being off-set by having an even amount of pressure 'pushing' on the other side of the blade (the side with no bevel).”
And further down:
“Because the tissue's 'push' on the broadhead's bevel is not met by any 'tissue push' on the opposite side of that individual blade's edge, the edge is shoved sideways; just as the knife's blade edge was when it made that 'walking cut'. Since a broadhead is piercing the tissue, and both its edges are being forced sideways (in the same direction) the broadhead rotates as it move forward.”
Further down are a number of examples of single bevel performance through various bones, including pictures comparing single and double bevels. He also performs a test using potatoes and a “free-rotating shaft”, showing a single bevel splitting a potato just by pushing it through.
Since it doesn’t appear that the arrow shaft is assisting the rotation (other than pushing the broadhead forward), you may get slightly better rotation of the broadhead since it doesn’t have to also turn the arrow. Just a theory though, would need to see test results.
I’m sticking with the static inserts for now, I don’t like the idea of introducing a moving part into my arrow.
Here’s a link to the full write up - https://www.tuffhead.com/why-single-bevel
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DRR324
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Following this and studying it as well. My first thought on the spinners, are they designed to help with arrow flight issues from possible broad head planing? I feel like the shaft rotation would help to rotate the single bevel through a body cavity, whereas the spinning insert would stop that rotation once the head enters the cavity. Of course the videos hitting the milk jugs and stopping rotation leads to further unanswered questions...
I media the broadhead is in causes the rotation....the tissue is causing the ''push'' like stated above...water in a milk jug has very little resistance so the mechanical rotation won't happen like in a dense media
Rob is from the Ashby Bowhunting Foundation which is where I sent my original question asking about arrow rotation, spinner inserts, and if they have any effect on single bevel penetration. Rob shared my questions with Dr Ed, and Rob was the one that just sent the reply to my questions after he and Ashby discussed them.
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I agree with Mr. Neilsons points too. However, I do still believe that there is a lot of merit with the spinning insert concept; especially when you consider the whole benefit of an EFOC or an UEFOC arrow. Remember, this is kind of a paradigm shift as we have always thought of the push of the arrow instead of the pull from a heavier front end. The dynamic on how we have thought about arrow penetration is now somewhat reversed with high FOC arrow builds. So the spinning insert, in my mind, MAY in fact, facilitate greater penetration NOT by the momentum so much from the spinning but because there is now not a "binding" of the full length of an arrow while the heavy tip "pulls" the arrow through because of the "spin-able" insert. Does that make sense? I believe the merit of these may still be valid upon impact. The RF talks about "impact paradox" in his videos and I totally agree. So now we've been focusing on the side to side "yaw" of the arrow but what about the force at the tip and along the length of the shaft upon impact. So a typical, I'll call it a "static" arrow is spinning and hits bone and drives through but there is movement of the animal, shot angles are never perfectly at 90 degrees perpendicular to the animal so that arrow will still be most likely entering at an angle of some kind and that, in and of itself adds friction and drag on the entire shaft as the heavy head pulls it through. Force vectors are not completely straight so as the arrow and shaft hit the animal, force is also now being applied along the entire length of the arrow as it enters at an angle. And these vectors are not parallel to the impact point, they are angled as well. Add to that, the variety in the "medium" the broadhead and arrow are going through, I.e. hide, sinew, muscle, bone, cartilage, etc. and yes the arrow is tuned and with a heavy setup the broadhead is doing the work but there is still drag and other resistance and friction on the shaft as it goes through. Now with a spinning insert, theoretically, the heavy point is almost tailless now and as it hits and tries to pull the arrow shaft through the animal, because it can spin and it is pulling the shaft, there is potentially less drag on the entire arrow because it doesn't have as much of the resistance from the arrow through the rest of the medium as it goes through it. The only comparison I can think of is cleaning your firearm. If you have ever tried to clean a rifle bore with a tight fitting patch, especially when you are pulling the patch back through the bore, the cleaning rods that spin are much easier to pull through then a static rod. They are easier to push through too but with high EFOC arrows we need to think of the impact paradox and now how about the concept of "Penetration paradox"??? Is my reasoning flawed????
The arrow is going 200fps, give or take, I just can't see the spinner being able to just spin while inside the animal....there is still meat fully surrounding the blades....if anything is spinning once the broadhead enters (excluding mechanical bevel rotation) it's just the arrow behind the broadhead.
DRR324
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I agree with Weld. I would believe the broad head would briefly stop spinning as it enters the hide, and then possibly begin to rotate again (single bevel) through the cavity as it “pulls” the arrow. Would really enjoy some scientific research, slow mo videos, etc regarding these inserts vs static inserts.
The very instant that a single bevel impacts the target, the torque begins. At that point, its has not yet reached its full leverage behavior, but it has begun the twist.
Now, does a spinner free up the head (from the influence of the shaft) and allow the head to continue unencumbered? Or does the arrow (as a unit) retain more torque and split bone better WITHOUT the spinner?
We may be splitting hairs here (no pun intended), but I want to ensure I get every last fraction of an inch penetration. 1% more could mean an exit wound and that can mean the difference between a blood trail and no blood trail.
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I don't think there is any pulling going on with arrows, just propulsion and plain inertia. If you drive a single bevel wood chisel into the surface of a board at an angle it's either going to drive in the wood deeper or skip off depending or which way you have the bevel.
I love that post.
In my mind, the jury is semi-split on spinner inserts but I really like the thoughtful analysis.
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michigandrake
Well-Known Member
Guys ..... lets not out thing the room here. So the over or under rotation of a single bevel at impact is what ...... 13th, at best, on the list of penetrating factors and we are talking about giving up, at least a portion of the number one factor to achieve what ..... a minimal, possibly theoretical gain. I view the penetrating factors as a logarithmic function where the first few items really get you to the upper levels ....... from there the rest of the small stuff adds little bits. You can't mess with the foundation items or the whole system becomes less stable. I am a firm no when it comes to spinning inserts.
Art_Vandelay
Active Member
do you align the index nub or the cock vane with the spine?
Both. I'm shooting with the cock vane facing away from the riser, just like a recurve shooter, so the cock vane and index nub align. Didn't do that with shoot-thru rests, but I find it gives me the best vane/cable clearance with my current setup (NAP Apache drop- away rest on a Redhead Toxik XT bow).
hokiehunter373
Well-Known Member
25"