Measuring "Forgiveness" and other Properties on a Bow

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Jul 5, 2022
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Hey all, I've had a PSE X Force Dream Season since around 2010 and frankly have had no complaints with the bow. It's maxed out at 54 lbs draw weight, has easily taken down any deer I've shot (and half the time the arrows just blow through the deer and I can't find them), I shot a 3D league back in high school with it and placed pretty well, etc. However, I recently decided to look around at what technology has changed in the archery scene and additionally build another setup for target shooting.

As I read various forum posts on the internet, looked at specs around today's modern bows, and watched reviews on Youtube, I kept hearing a lot of qualitative terms describing upgrades. "This bow has a much smoother draw cycle." "Longer bows/wider limbs are more forgiving." "This cam is very aggressive." "There's so much more to a bow aside from speed and weight."

While I'm in no way discrediting any of these claims (and have witnessed some of them myself), it did make me wonder:

Has anyone come across videos where people measure and quantify these properties?

I've seen some high speed videos of shots and things like that but otherwise haven't stumbled across too much on this.

Professionally, I work as an engineer and teacher (if my username didn't already give that away). So I'm thinking about spending the rest the summer creating a short Youtube series where I start with some of the physics around archery (which I know has been done before), develop a test rig, and then try to measure various things on a few different bows I've got access to.

PS: I know a lot of building a bow setup revolves around what's comfortable for the individual using it, I just want to see if I can start to put hard numbers to that (for at least myself).
 
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sndmn11

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I have never seen quantitative analysis of bow model forgiveness. I have seen draw force curves on graphs, but none for all available draw lengths of that model.

It would be cool to see if generic thoughts about brace height, riser length, deflex/reflex, etc could be established as fact. I would bet though that there would be a good deal of variation and models with similar physical specs would present a wide variety of attributes.
 
OP
aerophysicist
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I have never seen quantitative analysis of bow model forgiveness. I have seen draw force curves on graphs, but none for all available draw lengths of that model.

It would be cool to see if generic thoughts about brace height, riser length, deflex/reflex, etc could be established as fact. I would bet though that there would be a good deal of variation and models with similar physical specs would present a wide variety of attributes.
Yeah I've seen some generic draw curves as well but wasn't sure if there was a collection somewhere where someone's already done this. I seen things like this done for batteries, motors, propellers, etc. in the RC community...but those things are also usually cheaper vs. buying a bunch of bows.

Part of why I asked the question I did is because I've been brainstorming ideas around the best way to measure the "feel" of a bow's grip. I think you'd need to have something that measures the different pressure points along the whole back of the grip...and likely at points on each side to see if the bow is twisting a lot. I've got some ideas, but it would be great if I could see some things that other people have tried.

I've also seen the new Mantis X8 sensor that's used to help people understand what they're doing during their shot. I'd definitely set up something similar to that myself.
 

sndmn11

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I would consider tuning to achieve a standardized metric of being in tune, like a bare shaft through paper from a shooting machine, then adjusting the rest and timing (separately) in all directions to test "forgiveness" as a measure of precision.
 
OP
aerophysicist
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That's a great suggestion. I was originally thinking about things like slightly angling the whole bow, slightly moving it in any direction, etc. I didn't even think that forgiveness could be considered an aspect of slightly improper tuning.

The paper tuning discussion was something that also got me started on this. I spent some time tracking down the cheapest high speed camera I could find so I could have one of my students do image processing on the high speed video. The plan is to see how well we can "paper tune" with high speed footage.
 

sndmn11

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That's a great suggestion. I was originally thinking about things like slightly angling the whole bow, slightly moving it in any direction, etc. I didn't even think that forgiveness could be considered an aspect of slightly improper tuning.

The paper tuning discussion was something that also got me started on this. I spent some time tracking down the cheapest high speed camera I could find so I could have one of my students do image processing on the high speed video. The plan is to see how well we can "paper tune" with high speed footage.

I bring that up because I believe some well known target archers find that their most forgiving setup from a precision and accuracy standpoint (group tuning) point is often not a bullet hole through paper.
 
OP
aerophysicist
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I bring that up because I believe some well known target archers find that their most forgiving setup from a precision and accuracy standpoint (group tuning) point is often not a bullet hole through paper.
Wow no kidding, I might need to watch a few more video interviews with some professional archers to get a better grasp on the current go-to methods for getting the best tuned bow.

I've personally never felt like I needed to paper tune to get very tight groups and from a few things I read it sounded like some people were calling it more of a "quick way" to tune for hunting.
 

Marble

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Forgiveness, as I have understood it, relates more to ATA and brace height. The last variable is the holding weight.

Those are probably things that can be measured.

For the most part, or ever IME, you don't see pros or people in competition shooting small ATA, short brace height and high let off. I have my theories on why this is. Asked on how it's been explained to me. But it's never been quantified to me. Nor have I seen it.

The feel of a bow, how I describe it, is how the shot goes off. How the bow reacts after the shot. How the back wall feels at full draw. How the cam feels during the draw.

These things cannot be quantified. It is a subjective feel. Based on experience, draw length, strength, overall fitness, time shooting the bow, past experience with other bows. The list is endless..

Sent from my SM-G986U using Tapatalk
 
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OP
aerophysicist
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Forgiveness, as I have understood it, relates more to ATA and brace height. The last variable is the holding weight.

Those are probably things that can be measured.

For the most part, or ever IME, you don't see pros or people in competition shooting small ATA, short brace height and high let off. I have my theories on why this is. Asked on how it's been explained to me. But it's never been quantified to me. Nor have I seen it.

The feel of a bow, how I describe it, is how the shot goes off. How the bow reacts after the shot. How the back wall feels at full draw. How the cam feels during the draw.

These things cannot be qualified. It is a subjective feel. Based on experience, draw length, strength, overall fitness, time shooting the bow, past experience with other bows. The list is endless..

Sent from my SM-G986U using Tapatalk
Yes for ATA I think that can be determined in part as a moment of inertia thing...basically, the longer something gets, the more effort it takes for you to "twist" it in your hand (wind resistance aside).

Brace height might be related to moment of inertia (since I'd assume that a longer brace height generally puts the cams back farther behind the grip), though I also wonder how much the arrow-string contact time might have an effect. Since a 30" draw with 6" brace height means you're pulling the string back 24" where a 7" brace height means 23" of string travel.

Holding weight will be interesting/fun. I was just shooting this last weekend and turned up my holding weight to get a better release from my hinge release. This might be specific to the person...or might play a role in consistency with the bow itself.

I 100% agree on your points with feel. It is very subjective and likely has (too) many different variables that must be taken into account. However, I like taking a shot at challenges like this to see if I can get some idea of the aspects that matter.
 

Marble

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Yes for ATA I think that can be determined in part as a moment of inertia thing...basically, the longer something gets, the more effort it takes for you to "twist" it in your hand (wind resistance aside).

Brace height might be related to moment of inertia (since I'd assume that a longer brace height generally puts the cams back farther behind the grip), though I also wonder how much the arrow-string contact time might have an effect. Since a 30" draw with 6" brace height means you're pulling the string back 24" where a 7" brace height means 23" of string travel.

Holding weight will be interesting/fun. I was just shooting this last weekend and turned up my holding weight to get a better release from my hinge release. This might be specific to the person...or might play a role in consistency with the bow itself.

I 100% agree on your points with feel. It is very subjective and likely has (too) many different variables that must be taken into account. However, I like taking a shot at challenges like this to see if I can get some idea of the aspects that matter.
If you want to get a "better release" not sure what you mean by that with your hinge, it cam be affected by changing your draw length. If you want to experiment a little bit with this, try an exaggerated closed stance. Like standing facing more to your target. It will shorten your draw length and it will make it difficult to pull through with back tension. Then close your stance and put your feet directly in line with your target. This will increase your draw length and make it easier to pull through.

Most people do not realize this and never figure out why they struggle with shooting high on up or down hill shots. Shooting up or down at angles will change your body geometry and you need to make adjustments to your stance to compensate.

Sorry I ranted off topic....

I hope you find some interesting facts with your search.

Sent from my SM-G986U using Tapatalk
 
OP
aerophysicist
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If you want to get a "better release" not sure what you mean by that with your hinge, it cam be affected by changing your draw length. If you want to experiment a little bit with this, try an exaggerated closed stance. Like standing facing more to your target. It will shorten your draw length and it will make it difficult to pull through with back tension. Then close your stance and put your feet directly in line with your target. This will increase your draw length and make it easier to pull through.

Most people do not realize this and never figure out why they struggle with shooting high on up or down hill shots. Shooting up or down at angles will change your body geometry and you need to make adjustments to your stance to compensate.

Sorry I ranted off topic....

I hope you find some interesting facts with your search.

Sent from my SM-G986U using Tapatalk
Thanks for the input! Yeah I'm using a fulkrum flex and have it set pretty "hot" right now. So I did shorten my draw length (because despite what I was told at my local archery shop, it was tough to pull through the shot).

However, after I shortened the length, I decided to put a bit more holding weight on it too because I still felt like I had a lot of control between the time the release "clicked" and the time the bow shot. This was causing me react in anticipation from time to time and pull some shots to the side.

So to your point, (and the point of the title of this article) I'm defining a "better release" as one where I'm less unsure of when my bow will shoot once I'm anchored and begin to pull through my shot. Currently the only ways I'm measuring that are: 1. Am I aware that I slightly jerked my bow? 2. Did the arrow go to a different place than where I wanted? 3. Once my release clicks, is there a lot of time before the arrow fires? 4. When this problem occurs, do I still face it if I switch to my thumb trigger release?

I'm pretty new to hinge releases -so I'm still trying to get the right setup figured out.

The stance thing is something I'm always extremely conscious of. It's definitely something I check before each shot I take. I've never experimented with tweaking

Overall, I'm always still learning -so thanks again for any input.
 
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Forgiveness is really just measured in score. Its when you make a shot that didn't feel perfect, but it still hits where you wanted, or very close.

It's hard to make it quantitative, but if you shoot a lot of rounds for score you can track that to find what helps you.

We know certain things contribute to make a setup more forgiving, but things like torque tuning will tailor the bow to you, many will play with the timing just slightly as well.

Generally it's longer ATA and Brace height, but I think it's probably more likely a certain minimum number for a shooter, more isn't always better, but might not really hurt.


I shoot several rounds a week for score, that's the only way I have found to measure progress. What feels best initially isn't always what is best.
 

TX_hunter

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I think probably the best way would be to set up a bow, then shoot for score, or long distance groups.

Record scores/group size. Do it under different conditions (wind, fatigue, high heart rate). Take a lot of samples.

The bow that produces the best groups would be the "most forgiving". This is a lot of work and time consuming, and your results may not match the next guy.

Shooting a bare bow at 5 years in a shop like a lot of reviews or tests do really don't tell you much. Personally I'd rather take a gamble, buy a bow and shoot if for a while, and if I don't agree with it then just sell it rather than try to pick by feel from blind bailing a few shots.
 
OP
aerophysicist
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Yeah trying to isolate a lot of the variables is a very tricky thing. The human part of things does play a huge factor in the whole situation.

I'd be hesitant to shoot the bow myself for these unless I'm measuring how I treat the bow.

Things like the wind and all of that stuff is also tricky because sometimes you get constant wind, sometimes you get gusts, etc.

I posted this in another thread, but I found a presentation I did back in undergrad where we were trying to do wind tunnel testing on how vane angle effected drag/rotation. I thought at the time about how we could test stability in the wind with regular arrows but it's not super easy unless you set up a bunch of fans and try to measure/control the airspeed.

It was still a very fun project though.
 

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Marble

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Thanks for the input! Yeah I'm using a fulkrum flex and have it set pretty "hot" right now. So I did shorten my draw length (because despite what I was told at my local archery shop, it was tough to pull through the shot).

However, after I shortened the length, I decided to put a bit more holding weight on it too because I still felt like I had a lot of control between the time the release "clicked" and the time the bow shot. This was causing me react in anticipation from time to time and pull some shots to the side.

So to your point, (and the point of the title of this article) I'm defining a "better release" as one where I'm less unsure of when my bow will shoot once I'm anchored and begin to pull through my shot. Currently the only ways I'm measuring that are: 1. Am I aware that I slightly jerked my bow? 2. Did the arrow go to a different place than where I wanted? 3. Once my release clicks, is there a lot of time before the arrow fires? 4. When this problem occurs, do I still face it if I switch to my thumb trigger release?

I'm pretty new to hinge releases -so I'm still trying to get the right setup figured out.

The stance thing is something I'm always extremely conscious of. It's definitely something I check before each shot I take. I've never experimented with tweaking

Overall, I'm always still learning -so thanks again for any input.
Try shooting without the click. For me, I discovered it was lengthening the time of my shot and interrupting my shot process. I switched and all is better.

Sent from my SM-G986U using Tapatalk
 

Marble

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Forgiveness is really just measured in score. Its when you make a shot that didn't feel perfect, but it still hits where you wanted, or very close.

It's hard to make it quantitative, but if you shoot a lot of rounds for score you can track that to find what helps you.

We know certain things contribute to make a setup more forgiving, but things like torque tuning will tailor the bow to you, many will play with the timing just slightly as well.

Generally it's longer ATA and Brace height, but I think it's probably more likely a certain minimum number for a shooter, more isn't always better, but might not really hurt.


I shoot several rounds a week for score, that's the only way I have found to measure progress. What feels best initially isn't always what is best.
Torque tuning is something I have never done. And know nothing about. I would like to do this on my envicta for indoor this winter. I've messed with timing, draw length, tiller, holding weight and firmness of the wall.

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Torque tuning is something I have never done. And know nothing about. I would like to do this on my envicta for indoor this winter. I've messed with timing, draw length, tiller, holding weight and firmness of the wall.

Sent from my SM-G986U using Tapatalk

It has helped me with all my bows. I have talked to another guy that I trust and he has said that on one bow it made no difference, while another he had to do it.

So it might or might not help, but it's actually really easy to do, so I don't see a downside. I usually do it pretty early in a bow setup anymore.

The Invicta is a little harder, cause depending on the rest it can be a hard to have much adjustment, at least without it being way back, really nice bow otherwise.

Don't know that you will see much of a difference TT for indoor, but outdoors is where it will shine.
 

Marble

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It has helped me with all my bows. I have talked to another guy that I trust and he has said that on one bow it made no difference, while another he had to do it.

So it might or might not help, but it's actually really easy to do, so I don't see a downside. I usually do it pretty early in a bow setup anymore.

The Invicta is a little harder, cause depending on the rest it can be a hard to have much adjustment, at least without it being way back, really nice bow otherwise.

Don't know that you will see much of a difference TT for indoor, but outdoors is where it will shine.
My Axius has the Fast Eddy and in-line QAD rest so not much adjustment there. But the Invicta has a spot hogg edge and Acheive XP, so I've got room to mess with it. I'll talk to my buddy and get his input. Thanks!!

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Ashenwelt

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If you can watch some videos with MFJJ this year. He has a fairly recent push that basically the old brace height story isn't as useful and he recommends reflex length and riser height. It was an interesting discussion on one of his YouTube videos.

Also you will need to work on what you define smooth draw as. Some people consider this ease of draw, others as pulls like a recurve, some pulls the same weight, etc.

I will say trying the Primes this year showed me there was something to their idea of stopping tourqe and even some fighting against cant by default

Good luck!
 
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