** BROADHEADS ** Science & Math

[nexus]

Let me try to be clear, because I often am not. The tuning of ones bow is an effort to balance forces throughout the flight of the arrow. The finer forces induced by the selected point (target, broadhead) at launch are tuned out, as much as possible, to use the least amount of blunt force vane steerage after the launch (the vanes can provide a major parachute effect - see Kupper experience above). The combination of point design, arrow spine, arrow diameter, rest alignment, yoke tune, arrow material, vane design, FOC, and the myriad of other features work together (or against each other) to produce the final POI variability. But you are correct RosinBag, the greatest variable still is the Indian.

Still would like to see a couple rounds from someone like Shane (no pressure) who has a reputation for tuning and shooting. I'm guessing his POI variability is going to be more linear (archer limitations over distance) than parabolic as predicted by the velocity calculations.

Just staying with the thought of the thread, so does this mean a good archer has a 1" group per ten yards only for field points? A hunter would then need to use a different standard in determining his effective range when using a broadhead. Just asking everyone there thought as I am working on a different article that incorporates effective range and traditional accuracy metrics.

 

[ontarget7]

Okay, so I looked at the OP's chrono data and all the "real world experience" posts; I am wondering why both sides of the argument can't be right here.

Clearly the data shows a dramatic drop in arrow velocity at greater distance with the introduction of the broadheads. But it would seem to me that this reduction in velocity is less a function of broadhead drag (force/resistance to the broadhead shape) versus the likely increased vane steering necessary to offsetting the initial planing (cross force) of the broadhead at launch. I would think, the induced drag on the vanes is the greatest drag coefficient; that's why we use different styles, lengths, and heights to steer an arrow.

That being said, the impacts of broadhead planing should be able to be minimized through fine tuning to significantly reduce the larger vane steering impacts. There are many different forms of tuning, but it would reason that if one is trying to ensure that the bow is casting the arrow in direct line with the force from the string to minimize initial future broadhead planing, bare shaft tuning (zero vane steering) would be well suited for the job (also checks arrow spine - minimizing vane steering associated with shaft flex). I would suspect that is why Shane (ontarget7) can demonstrate that his fixed blade broadhead hits with his field points at 80 yards. He has tuned his bow to the point that the dominant vane steering forces have been minimized regardless of point. And as the OP chrono data showed, if the bow was not finely tuned (Shane feel free to take your bow out of tune prior to hunting season to demonstrate...lol) the vane steering forces would greatly increase and result in field points and broadheads having significantly different POIs and velocities down range.

Lastly, if the difference in POI was predominately related to the drag coefficient of the broadhead design, this would be a constant and not able to be compensated for at all distances as previously posted (i.e., on target at 80 yds but high at 20 yds). However, if the real issue is vane steerage, then once tuned, the bow should shoot spot on at all distances out to the limits of your tune.

Shane we've seen the video at 80 yds and that your bow appears tuned for this distance, can you shoot the same arrows at 20, 40, and 60 to see how "high" your arrows impact relative to each other at these distances?


I need more coffee this morning....

Let me try to be clear, because I often am not. The tuning of ones bow is an effort to balance forces throughout the flight of the arrow. The finer forces induced by the selected point (target, broadhead) at launch are tuned out, as much as possible, to use the least amount of blunt force vane steerage after the launch (the vanes can provide a major parachute effect - see Kupper experience above). The combination of point design, arrow spine, arrow diameter, rest alignment, yoke tune, arrow material, vane design, FOC, and the myriad of other features work together (or against each other) to produce the final POI variability. But you are correct RosinBag, the greatest variable still is the Indian.

Still would like to see a couple rounds from someone like Shane (no pressure) who has a reputation for tuning and shooting. I'm guessing his POI variability is going to be more linear (archer limitations over distance) than parabolic as predicted by the velocity calculations.

Just staying with the thought of the thread, so does this mean a good archer has a 1" group per ten yards only for field points? A hunter would then need to use a different standard in determining his effective range when using a broadhead. Just asking everyone there thought as I am working on a different article that incorporates effective range and traditional accuracy metrics.

I feel your thoughts are spot on with my experience in tuning and shooting broadheads down range.
Well put

It may be a few before I can post you a video at varying distances with my work load. However, I will make that happen at some point.

I never compensate for broadhead impact and I’ve been able to group at all ranges with broadhead and fieldpoints.

It reminds me when I first started posting stuff about bareshaft tuning videos etc and guys claiming it was impossible to group together since bareshafts would have far less drag. There is way less variance in bareshafts and fletched than you think.

This is 40 yards

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[Brendan]

@nexus - In my mind, you're overcomplicating it, and talking about some things not really related to the issue at hand. But, you definitely touch on the right points.

It's not this:

Clearly the data shows a dramatic drop in arrow velocity at greater distance with the introduction of the broadheads. But it would seem to me that this reduction in velocity is less a function of broadhead drag (force/resistance to the broadhead shape) versus the likely increased vane steering necessary to offsetting the initial planing (cross force) of the broadhead at launch. I would think, the induced drag on the vanes is the greatest drag coefficient; that's why we use different styles, lengths, and heights to steer an arrow.

It IS this:

Lastly, if the difference in POI was predominately related to the drag coefficient of the broadhead design,

What we're talking about is this. Take two IDENTICAL arrows. Same everything, except on one arrow you use a 100gr field point, on the second arrow you screw off the field point and use a 100gr fixed blade broadhead. Then, you shoot them out of the same bow using a shooting machine.

I don't want to say drag from the vanes is irrelevant, it's just that it's the same between the two arrows, so irrelevant in talking about the difference in drop between those two arrows.

What is relevant is that the fixed blade broadhead will have higher drag coefficient, will slow the arrow faster, will have a lower average speed to target, and will drop more than the field point.

If you tune them to hit the same at close range, the broadhead will be low at long range. If you tune them to hit the same at long range (i.e. planing up), they'll be high at short / mid ranges.

The magnitude of how much difference you see and at what range would be due to a whole number of factors. Think about drag coefficient, drag in a laminar vs. turbulent flow (linear vs. exponential), momentum of the projectile, speed of the projectile, etc, etc.

And at the end of the day, the difference is going to be pretty damn small at short ranges to the point it doesn't matter for most people

 

[ontarget7]

I think Shane is an outstanding guy when it comes to tuning. In his video he even states he wasn’t able to hold in the exact same spot. I also think two arrows isn’t enough for me to say it is doing what the video is trying to show.

I say put a fresh target up and shoot 20 of each and see if they are still doing what the video portrays.

There was no compensation on hold on target and I would be completely lying if I could say I was holding on the exact same spot at 80 yards.

You donate the arrows and broadheads, since a good portion will get ruined and I’m all in

I’ve been grouping with fieldpoints and broadheads for years with zero compensation for drag.

Again, it reminds me when most found it impossible to group bareshafts with fletched down range do to the difference in drag.
I feel the momentum carries with the fletched arrow where bareshaft not near as much, so the impact point when tune is right is really very small. Way smaller than many might think.


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[nexus]

Shane - I look forward to the videos. I've had similar experiences with regards to broadhead flight out to my limits.. Might be interesting, if possible, to demonstrate the field point to broadhead groups before and after bare shaft tuning (same arrows - same bow).

RosinBag - When you say POI at the same spot in your challenge, what are we defining as the same? Same hole or within some other defined radius? Thanks for the thread and information. Been a long time since the old Physics classes, but always love a good science brain teaser.

 

[5MilesBack]

...

RosinBag - When you say POI at the same spot in your challenge, what are we defining as the same? Same hole or within some other defined radius?

With a Hooter Shooter it should be same hole. Without a HS, the two arrows touching (repeatable) should be good enough IMO.........just depends on the distance and how many times you shoot them. I would love to have an unlimited supply of arrows and BH's and shoot a bunch of each all at the same bullseye at the same time, to get a feel for a 20 or 30 arrow average group size. But as soon as I can see the fletching in the target, that's what my brain sees and that's where the arrows hit. That's why I like shooting groups in the bright sun with my bright yellow fletching.

 

[RosinBag]

Shane - I look forward to the videos. I've had similar experiences with regards to broadhead flight out to my limits.. Might be interesting, if possible, to demonstrate the field point to broadhead groups before and after bare shaft tuning (same arrows - same bow).

RosinBag - When you say POI at the same spot in your challenge, what are we defining as the same? Same hole or within some other defined radius? Thanks for the thread and information. Been a long time since the old Physics classes, but always love a good science brain teaser.

Nexus, I think you are far above me in the physics realm, I have no special skills. I probably max out knowing stuff starts out at a speed and then slows down.

By for me my personal dispersion is at long range, 80 and above, a four inch aiming circle. With most bows, 270-299 FPS, that is about a one yard difference. I think that is pretty damn good.

With a Hooter Shooter, that is doable without a doubt. If by human, we will need to get a Broadwater to come shoot it for us. I don’t think anyone in this forum can consistently shoot 80 yards in a four inch group. And if they are, there is a lot of money out there waiting for your skills.

I think I shoot pretty solid, but a top level pro is so far above the second tier group it isn’t even comparable. A top level pro is probably five times as good as a second tier level Free Style archer doing very well in local and national tournaments.

For example, today me and my buddy were shooting our target bows at 111 yards, because that is where the shade was. Shooting at a five inch dot, and groups of five arrows, I would in nearly every end shoot what I considered a poorly executed shot. That shot would be 10” out at that distance. Top pros dispersion for a bad shot is just an inch or so out. They are that much better.

 

[JNDEER]

So... If someone was able to group a BH and FP out to distance.... then it would be safe to assume that the BH and FP travel at the same speeds at that distance??

 

[RosinBag]

So... If someone was able to group a BH and FP out to distance.... then it would be safe to assume that the BH and FP travel at the same speeds at that distance??

Not at all based on what I have seen. I can get them to group at say 80, but the BH is substantially higher at 20. One of the more physic engineers will chime in I am sure, but I guess it is due to launch characteristics leaving the bow.

It is completely impossible for them to have the same speed at distance if the BH has more drag than the FP. My Sevr was even 10FPS slower at distance than my FP and that BH has a pretty small design.

 

[RosinBag]

I just went back to the top of his thread, 8 FPS slower at a 100 mechanical Sevr to FP.

 

[JNDEER]

I agree Rosin.

My point was that is someone who shoots very well (ontarget, Justin, 5Miles, etc) can hit the same spot with a FP and BH at 20-80+... then the only explanation is that the arrow that has the BH and the arrow that has the FP must have virtually the same FPS at the ending distance.

 

[307]

To be valid in shooting a group with any human archer, the human would have to be blinded to which projectile he/she was shooting. Otherwise bias is inevitable and "corrections" will take place in order to improve the outcome.

 

[307]

I agree Rosin.

My point was that is someone who shoots very well (ontarget, Justin, 5Miles, etc) can hit the same spot with a FP and BH at 20-80+... then the only explanation is that the arrow that has the BH and the arrow that has the FP must have virtually the same FPS at the ending distance.

Which is impossible, and that should tell you something. Other variables are compensating...

 

[RosinBag]

To be valid in shooting a group with any human archer, the human would have to be blinded to which projectile he/she was shooting. Otherwise bias is inevitable and "corrections" will take place in order to improve the outcome.

307 you are 1000% spot on with this.

The mind will make it you compensate even when you don’t know your doing it. That is why the shooting machine is invaluable.

And back yard shooting lacks the pressure to prove you are a good shooter. Big tournaments and money will put the pressure on and will show your flaws better than anything.

Even the best archers in the world, rarely shoot as well in a tournament verse when they practice.

 

[ontarget7]

So the guys that can group fieldpoints and broadheads together up close and down range are just compensating for it all the time ?

Do you realize it would take an exceptional archer to always be on when calculating that. I’m a fairly decent shot but definitely not that good.

It’s a combination of tune, archer being one with tune and overall broadhead selection. I’ve tuned a lot of bows for people over the years and have first hand experience with them as well. Feedback on broadheads and fieldpoints hitting together. Many never thinking it was possible.

I won’t bother boring you with a video. From the responses here, it’s obvious, even a video wouldn’t prove anything and just end up being a waste of my time.

Unfortunately, it’s to bad, as it’s definitely possible to achieve.

I’m out




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[Billy Goat]

So the guys that can group fieldpoints and broadheads together up close and down range are just compensating for it all the time ?

Do you realize it would take an exceptional archer to always be on when calculating that. I’m a fairly decent shot but definitely not that good.

It’s a combination of tune, archer being one with tune and overall broadhead selection. I’ve tuned a lot of bows for people over the years and have first hand experience with them as well. Feedback on broadheads and fieldpoints hitting together. Many never thinking it was possible.

I won’t bother boring you with a video. From the responses here, it’s obvious, even a video wouldn’t prove anything and just end up being a waste of my time.

Unfortunately, it’s to bad, as it’s definitely possible to achieve.

I’m out




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I'd appreciate a video. I have said that I know my setup will put fp to bh at 65 yards. I haven't noticed a difference at close range but it very well could be that it shoots a half inch high with fp's at 25 or 30 yards. With a hunting bow I would say that is still grouping with my fp's but I guess some would not.

 

[5MilesBack]

Do you realize it would take an exceptional archer to always be on when calculating that. I’m a fairly decent shot but definitely not that good.

This ^^^^. If one could "aim off the bullseye" that consistently to put the two together, they would be an absolute exceptional shot........even better than just aiming at a bullseye and hitting it.

 

[5MilesBack]

Not at all based on what I have seen. I can get them to group at say 80, but the BH is substantially higher at 20. One of the more physic engineers will chime in I am sure, but I guess it is due to launch characteristics leaving the bow.

From my experience, tuning adjustments show a much greater impact at distance than they do up close. And that makes sense, because the further the arrow goes out the more offline it will continue to fly. A minor adjustment will also affect up close, but is much less noticeable to the human eye.

So, if your BH's are hitting below your FP's at 80.....let's say 2"........and you make an adjustment that brings those two together at 80, the difference at 20 should be much less noticeable than that. So what do you mean by "substantially higher at 20"?

If I put a 1/2 or full twist in a cable that changes where the nocking point is in relation to the arrow rest and that brings BH's and FP's together at 80, both those arrows are still leaving the bow at the same angle. I.E......the bow and rest don't know what's on the end of that arrow. So they should still be very close together at 20 yards.......the launch angle is identical for both arrows.

 

[nexus]

Well that's a bummer. Would have liked to have seen a good shooter record some tests.

As I have always said, there is no doubt in my mind that both camps are right here. The data can be accurate but the overall cause is a function of the total system not the "straw that broke the camels back".

A system that is not in optimal balance will often show significant impacts associated with minor changes. A system that is optimized will operate more efficiently even in the event of minor changes. A bow is no different.

 

[307]

So the guys that can group fieldpoints and broadheads together up close and down range are just compensating for it all the time ?

Do you realize it would take an exceptional archer to always be on when calculating that. I’m a fairly decent shot but definitely not that good.

It’s a combination of tune, archer being one with tune and overall broadhead selection. I’ve tuned a lot of bows for people over the years and have first hand experience with them as well. Feedback on broadheads and fieldpoints hitting together. Many never thinking it was possible.

I won’t bother boring you with a video. From the responses here, it’s obvious, even a video wouldn’t prove anything and just end up being a waste of my time.

Unfortunately, it’s to bad, as it’s definitely possible to achieve.

I’m out


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Well, then accept Doug's challenge on the shooting machine. Eliminate the major variable in the system (the human) and see if your hypothesis holds up...