Center Shot ain't always good!

[Ed Ashby]

#5089

On the “Time to increase FOC” thread I mentioned that building out the arrow plate – making it thicker – was a useful tuning tool when working with the higher amounts of arrow FOC. It allows a weaker dynamic arrow spine to tune to a given bow. Then it occurred to me that there’s another point about center shot bow design that I should have mentioned.

When a bow is TRUE center shot – that is, the center line of the arrow precisely aligned with the bowstring – it can cause problems with arrow tuning and arrow flight. At ‘true center shot’ the arrow doesn’t know which way to flex first, when a force is applied on the nock end. This is especially true when the arrow is on an arrow rest and makes no contact at all with the bow’s sight window. Since there’s little or no ‘resistance’ applied to one side of the arrow, the arrow becomes ‘confused’ (for lack of a better term). It doesn’t know whether it should first flex to the left or to the right. This is one reason that a markedly stiffer arrow spine is required when the bow is truly ‘center shot’.

With a normal FOC arrow, the less center shot a bow is greater the degree of arrow paradox, and the more fletching required for the arrow to quickly recover. With normal FOC and a center shot bow design there will be a lesser degree of arrow flex (compaired to a non-center shot bow). This means that the duration of paradox will be less, even on a unfletched shaft, and less fletching will be required to overcome the paradox. That’s because of the stiffer spine required when using a bow with a more center shot design; nothing else. It’s stiffer so it flexes less when a given force is applied. At a given draw weight and bow design, and using the same amount of weight at the arrow’s front, the more center shot the bow, the stiffer the dynamic arrow spine rquired to tune correctly.

EFOC/Ultra-EFOC arrows, even when shot from a bow having no sight window cut into the bow at all, recover from paradox as quickly (or more quickly) that a normal FOC will from a true center shot bow. That’s why I can have my Ultra-EFOC arrows flying dead straight; showing dead straight target impact; at distances as close as one yard, and maintaining that dead straight impact at every range from there back.

There’s nothing magic about a center shot bow design. Like so many other items, the degree of a bow’s center shot is one of those things that’s as much marketing hype as it is something of significance in the level of accuracy or performance that can be achieved from a bow.

Ed

[David Petersen]

#37244

Ed said: “EFOC/Ultra-EFOC arrows, even when shot from a bow having no sight window cut into the bow at all, recover from paradox as quickly (or more quickly) that a normal FOC will from a true center shot bow.”

OK, Ed, as your crash-test dummy, I must ask what exactly are you saying here? That my homemade longbows with no centershot perform with EFoC arrows just as well as a centershot bow … or are you saying that with my near-centershot Shrew longbows I might get better flight — and/or be able to get good flight with higher FoC on a given arrow without that arrow falling underspine — by building out the back of the rest plate? Or all the above? Or am I missing it entirely? 😕 dave

[Ed Ashby]

#37259

OK, Ed, as your crash-test dummy, I must ask what exactly are you saying here? That my homemade longbows with no centershot perform with EFoC arrows just as well as a centershot bow

Yes. When tuned with EFOC arrows total recovery from initial paradox (to be distinguished from arrow vibration during flight) is as quick from a non-center shot as from a (near, in the case of your Shrew) center shot bow.

or are you saying that with my near-centershot Shrew longbows I might get better flight and/or be able to get good flight with higher FoC on a given arrow without that arrow falling underspine — by building out the back of the rest plate?

Correct again. By building out the side plate on your Shrew you will be able to make a too weak spined EFOC arrow (caused by the added weight up front) tune correctly to the bow.

This isn’t the easiest of concepts, so fire away if the’s stii not clear.

Ed

[Str8arrow]

#37386

Ed, I think I understand what you are saying, but I’m a bit confused by my experinece. I’ve always found compounds very easy to tune due to (I think) the spine forgiveness built into a centershot bow. Or, maybe it’s just the consistent release from a mechanical release. When tuning my traditional bows, it always seems I’ve got to fiddle with my tip weight and arrow length to get the best flight. Or, are you only referring to the arrow recovery speed from paradox?

[Ed Ashby]

#37593

Steve, some of both. Speed of paradox recovery with a tuned EFOC setup from a non-centershot bow will be as quick, or quicker than paradox recovery from a well tuned arrow from a center shot bow.

No question but that a mechanical release makes a huge difference in getting consistent flight but, at least for most compound shooters, there is also an illusion of tuning ease. That’s created by the ability to just move the sight a bit to have it coincide with the point of impact of the arrows. Combine that with the very consistent grouping of a release, which groups even moderately tuned arrows very close together, and you have what appears to be a ‘tuned’ setup that isn’t really tuned.

If you’re doing either careful bare shaft or careful paper tuning with a compound it can be (an usually is) an even more tedious job then bare shaft tuning EFOC arrows from a non-center shot bow. It’s amazing how many “perfectly paper tuned” setup’s I’ve seen that are no longer ‘tuned’ when you change the distance from bow to the paper! No matter how badly an arrow flys, chances are it can punch a perfect hole in the paper at some exact distance. It’s just like a broken clock; which has the percisely correct time … twice a day.

Deviations in the quality of flight of anything less than a very well tuned arrow are more easily visible to the eye from non-center shot bow. That’s because the initial degee of paradox is greater. This becomes even more pronounced on a bare shaft, where there’s no fletching to speed stabilization of the arrow’s flight. However, with a well tuned EFOC arrow from a non-center shot bow recovery from even a massive degree of initial paradox (the initial bending that the arrow has to do to clear the bow) occurs in miliseconds. From a center shot bow, which will tune correctly with a much stiffer spine, the degree of initial paradox will be much less, ergo, it is less visible to the naked eye, but full recovery (with a normal FOC arrow) from the paradox will take as long or longer as that of the EFOC arrow from the non-center shot bow.

In tuning arrows with high amounts of EFOC to compounds I’ve found it benificial (makes it easier to get correct tuning) if you first make absolutely certain that the arrow rest is adjusted to be slightly off of center shot (move the rest just a touch farther away from the bow than where center shot truly is). I like to move the rest away from the bow enough that I can just barely visably detect that the arrow’s tip is now definitely, without question left (or right, for a left handed bow) of perpendicular to the bowstring. That’s to avoid that ‘confusion’ of the arrow ‘not knowing which way to bend first’ that occurs when the arrow is at true centershot.

The first time I tried to bare shaft tune an EFOC arrow to a compound I hit that problem; a perfectly center shot rest alignment. It was a right hand bow, but no matter which arrow setup I tried, one shot would go markedly weak spine and the next shot would go markedly stiff spine. Adjusting tip weight was showing no logical effect on the bare shaft tuning. I could increase or decrease tip weight substantually and the same pattern would show up; one shot weak spine, then next stiff spine. It nearly drove me nuts until I figured out what was happening, moved the arrow rest out and, bingo, the compound bare shaft tuned just like any other bow I’d tuned. No problem at all.

Ed

[Patrick]

#37930

Wow, VERY interesting! From what you’re saying Dr Ashby, it seems to me that with perfect center shot the release becomes even more critical, because just the slightest flaw in form can cause the arrow to want to go right OR left.

EDIT: The more I think about my supposition, the more I think I’m off target.

[Str8arrow]

#37967

When I tune a compound, I bareshaft just like my trad bows. I think one reason I find it easier is that I adjust draw weight instead of tip weight or arrow length to tweak it just right. It’s really quick to do it that way. The other thing I found I had to do was spine tune the arrow. I built a spine tester because I found carbons to have a very inconsistent spine from arrow to arrow. I would mark the stiff side of each arrow and then cull out those that varied more than .01 from each other. I really got great flight that way.

[David Petersen]

#38078

ED — I asked: “or are you saying that with my near-centershot Shrew longbows I might get better flight and/or be able to get good flight with higher FoC on a given arrow without that arrow falling underspine — by building out the back of the rest plate?”
You responded: “Correct again. By building out the side plate on your Shrew you will be able to make a too weak spined EFOC arrow (caused by the added weight up front) tune correctly to the bow.”

Now, this may seem like a minor point at first glance, but considering how many archers comment that they would like to experiment with increasing FoC but love their current arrows/shafts and fear they will go underspine with more weight up front. Suddenly, with this new info/insight, next time I find my arrows starting to act overpowered as I add weight to the front, I may be able simply to add a layer of self-adhesive backing … and see what happens. Can’t wait to try this but frankly I’ve been amazed at how much weight I can put up front without hitting spine problems. At least with carbons. I’m now building up a dozen experimental footed woodies to see just how much EFoC I can get, and we shall see. Thanks again! dave

[Jason Wesbrock]

#38137

Patrick wrote: Wow, VERY interesting! From what you’re saying Dr Ashby, it seems to me that with perfect center shot the release becomes even more critical, because just the slightest flaw in form can cause the arrow to want to go right OR left.

EDIT: The more I think about my supposition, the more I think I’m off target.

I don’t know about the wanting to go left or right part (never looked into it; never needed to) but it’s been common knowledge for many decades that setting up a bow for perfect center shot is a huge no-no for finger shooters. That’s why you won’t find any tuning guides out there that suggest otherwise.

I don’t know if it’s been mentioned yet in this thread, but there is an important distinction between center shot and center cut. Center cut is when a bow’s sight window is cut to the exact center of the bow. Center shot is when the center of the arrow shaft is in line with the center of the bow. Because of the diameter of the arrow shaft, the only way to get perfect center shot is to have a sight window that’s cut at least half the width of the arrow shaft beyond center. In reality, the widow would have to be cut ever further beyond center than that due to the thickness of the strike plate.

[Patrick]

#38144

J.Wesbrock wrote: I don’t know about the wanting to go left or right part (never looked into it; never needed to) but it’s been common knowledge for many decades that setting up a bow for perfect center shot is a huge no-no for finger shooters. That’s why you won’t find any tuning guides out there that suggest otherwise.

I guess I was thinking of it more theoretically, not necessarily with either fingers or a release. Prior to reading Dr Ashby’s report, I’d NEVER heard anyone say an arrow precisely centered would need to be stiffer spined, and in fact figured it was a no-brainer that the opposite would be true. I’m having a difficult time understanding how that is. I’m not disagreeing with Dr Ashby, I’m just trying to wrap my head around the concept…unsuccessfully so far.

J.Wesbrock wrote: Because of the diameter of the arrow shaft, the only way to get perfect center shot is to have a sight window that’s cut at least half the width of the arrow shaft beyond center. In reality, the widow would have to be cut ever further beyond center than that due to the thickness of the strike plate.

Good point.

[Jason Wesbrock]

#38174

Patrick wrote:
I guess I was thinking of it more theoretically, not necessarily with either fingers or a release. Prior to reading Dr Ashby’s report, I’d NEVER heard anyone say an arrow precisely centered would need to be stiffer spined, and in fact figured it was a no-brainer that the opposite would be true. I’m having a difficult time understanding how that is. I’m not disagreeing with Dr Ashby, I’m just trying to wrap my head around the concept…unsuccessfully so far.

I completely understand. Sometimes these things can be a bit confusing. Here’s how it works.

For a finger shooter, an arrow will flex side-to-side a given amount during the shot. How much it flexes is determined by a few different factors, but let’s isolate the major contributor, its dynamic spine. The weaker the shaft, the more it flexes. The further from center cut a bow is built, the more the arrow will have to flex to get around the riser (weaker arrow). Conversely, the closer to center cut the bow is built, the less the arrow will have to flex to get around the riser (stiffer arrow).

Let’s assume you have a perfectly tuned arrow and are shooting a recurve cut to center (remember, not center shot, but center cut). Your arrow flexes just enough to get around the riser as-is. If you build out your strike plate 3/8”, your arrow is now too stiff to properly flex around the riser, and you will now need a weaker dynamic spine (weaker shaft or more tip weight).

The opposite holds true if you properly tune for 3/8” from center cut, and then move your strike plate in 3/8”. Arrows that used to properly flex around the riser are now flexing more than they need to (i.e. they’re too weak) and you’ll need to increase your dynamic spine.

[Ed Ashby]

#38268

Dave, you have the right method down. I routinely use layers of tape to build the arrow plate out when I need to tune in an EFOC arrow that’s shooting just a bit weak spine.

Jason, I should have made that point more clearly. Glad you added it! In the first post on this thread I put what I meant – “When a bow is TRUE center shot – that is, the center line of the arrow precisely aligned with the bowstring – it can cause problems with arrow tuning and arrow flight.” – but really should have mentioned that center cut and center shot are not the same thing. Thanks for the add-in and clarification. It’s an important point for trad shooters, shooting with the arrow in contact with the riser. Its real easy for filks to confuse ‘center cut’ and ‘center shot’.

Along this same line, whenever the arrow is in contact with the bow’s riser don’t overlook that shaft thickness also affects the degree of center-shot, and becomes a factor in tuning. The larger a shaft’s diameter the weaker the dynamic spine required to tune perfectly. Conversely, the thinner the shaft the stiffer the dynamic spine will need to be. The center line of the thicker shaft sits further from the center line of the bowstring, and it will have to flex more to clear the riser and flex back for perfect alignment. The thinner the shaft the closer its center line will be to the bowstring’s center line, and the less it must flex to tune correctly. Applying this to a ‘traditional’ riser cut beyond ‘center’, to ‘true centershot’, that ‘true center shot’ will be correct for only one diameter of shaft. Use a shaft having a greater diameter and the bow is no longer ‘cut to center shot’. Use a shaft with a smaller diameter and the riser is now cut ‘past center shot’.

Ed

[Patrick]

#38314

So…am I to understand you guys to be saying that the reason for using a particular spined arrow is only to clear the riser? I really have to hit the reset button and reconfigure everything I thought I knew about the bow to arrow relationship if that is so. If not…well…maybe I’m just a lost cause.:oops::lol:

My understanding was that you needed to use a particular spine for a specific set-up simply because an arrow/broadhead combination demanded it, in and of itself. It appears to me, you guys are saying that is NOT the case. My brain is going to explode (noone panic…It’ll be a very small explosion)

[Ed Ashby]

#38377

Patrick, there are a host of factors that enter into ‘the correct spine’, but it’s definitely not an ‘in and off itself’ situation of just the broadhead and the shaft. If that were the case all you’d every need is a way to measure the static spine and a point weight chart showing which static spine you need for that weight of point. Finding the correct dynamic spine is what tuning is all about. It’s why I bare shaft tune every setup, even those I only use in testing. Without the correct tuning of every arrow setup the testing would be more or less meaningless.

Every factor about the bow, the arrow, the setup and the shooter himself affects arrow tuning. Even the type and quality of your release and the bowstring you use becomes a factor.

Looks like you’re seeing that now! 💡 😕 😀

Ed

[Patrick]

#38384

That is an interesting aspect that I really had NO clue about. AND, here I thought I knew everything. Now, at long last, I REALLY do.:lol:

I was over simplifying to intentionally focus on the main aspects of what I knew (or thought I knew) in relation to what I wasn’t sure I understood. I’m not even sure that made sense. I need a drink :shock::lol::lol:

I love learning and discussing this type of stuff, I just don’t always have the time to type out my questions precisely as I would like to. Sometimes, my own fault:oops:. Sometimes, work gets in the way:roll:.

[Ed Ashby]

#38405

Patrick, have a drink for me too. With all the things to deal with just trying to walk I’m already too unstable to consider having one! 🙁 Boy, I do miss my sundowners. 😥 How I would love to be looking forward to a good Wild Turkey 101 about the time the sun greets the desert sands!:)

Cheers,
Ed

[Patrick]

#39394

I had a couple drinks for you Dr Ashby. 😉

[Ed Ashby]

#39405

The help’s appreciated, Patrick! :lol::lol::lol:

Ed

[MontanaFord]

#39557

I think I also now understand the difference between center-cut and center-shot…lol…I was just waiting for somebody else to ask the question for me…haha…Thanks Patrick. And thanks Jason and Ed, too.

Michael.

[Patrick]

#39597

Sure thing Michael. I live by one of my all-time favorite quotes (by Chris Berman, from a hilarious ESPN commercial):
“There is no such thing as a stupid question, just stupid people that ask questions.”
So, you see…I never worry about asking a stupid question. :lol::lol:

[Author]

Posts