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These have been mentioned in various threads in the past, but I’m curious – how many of you EFOC freaks are using them? Why or why not?
Since switching to 4 x 2-1/4″ straight fletching, my arrows are pretty darn quiet – are there other advantages to the using turbulators that I’m not thinking of?
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I am also shooting 4 X 2.25 feathers and use turbulators. But to be honest I use them because Ed says they make a difference. My eyes and ears can’t not see any diff with or without them.
The only downside I see to using such small feathers is i lose sight of the arrow in flight after about 20 yards.
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“After 20 yards?!” Good Gravy! Arrows much beyond that are a blur to my aged eyes anyway.
Ed gives me whatfor whenever I talked to him (wrote) about my personal limitation of 3″ feathers…(3″x 1/2″) 😀
I just don’t trust my consistency that much to drop smaller…
Alas, I followed every post in another forum for a long time that he and OL Adcock posted including the turbulator results. I even bought engineering tape but it turned out to be too wide for their research… (stuff’s expensive and I found some on sale) Doh!
As I understood it, the benefit was if you’re set up is a slight bit squirrely with your UEFOC %, then the turbulator will help stabilize it all. (could be dead wrong on that–going on aged memory)
I’ve hit a formula about 28% FOC and that didn’t seem to NEED the turbulator, (in my memory) so I didn’t spend the extra $$ to experiment with it.
I “THOUGHT” it was MOST beneficial above 30% or something??? ED???
I still crown dip my arrows to aid in visual contact… but from behind, that only helps as critters run off mostly. (or digging them outa the leaves) Not from behind unless you got squirrely flight… which is where I thought the turbulator effect came in to stabilize.
Regardless, I’ve been doing the EFOC, just not the UEFOC. One friend, a devotee of the UEFOC, even switched out his nocks to up his FOC by using lighter, smaller nocks. I found the cap wraps too heavy, (lowered my FOC a LOT) so went with crown dip or spray…but I NEED that white on there to follow the arrow (or find it in the duff! 😯 )
I got stuck in a rut because I have a custom chopper in 3″, I stick with that (well, Matt Gundock has it now and sells custom turkey and other feathers)… and haven’t found I need the turbulator. Or so I tell myself!
Good luck you guys!
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Thanks, folks. That’s kind of what I thought – that it’s another item for the toolbox, particularly if you’re flight is squirrely and/or noisy, but that’s it’s not essential. I can’t say I’ve felt a need for them with my own setup, but I was just curious if I might be missing something.
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I’ve just put one on one of mine. Honestly I’m not seeing or hearing a difference, but it is something both the Doc and Troy B. recommend with the little fletching. I just bought some arrow wraps and cut a strip off the end of one of them (I think that was Troy’s suggestion). It’s quick, easy and cheap. Or frugal as Grumpy would say 😉
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Gentlemen, If memory serves, the goal when adjusting/testing the size of the fletching on tuned FOC arrows was to get the size down to as small as possible. This added significant FOC up front as a little off the back compounds to the front. The feather size one would end up shooting was the very shortest you could get away with that would still control a broadhead in a stiff cross wind, and account for a sloppy release. The arrow flight was supposed to be a little squirrely but be corrected by addition of the turbulator which in effect causes turbulence along the arrow shaft starting 1/4″ in front of your fletching. This made your small as possible fletching more effective as the feathers were able to “bite” into more of the turbulent air.
I have found with my own set up at around 32-34% UEFOC that I do not need them until my feathers get REALLY small:) I have one set fletched with 1 3/4 x .5″ feathers in a 4 fletch. The FOC on those are at 34%. I found I need the turbulator to stabilize the small fetching for hunting. Boy are they quiet with the small feathers!
Jans
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jpcarlson wrote: Gentlemen, If memory serves, the goal when adjusting/testing the size of the fletching on tuned FOC arrows was to get the size down to as small as possible. This added significant FOC up front as a little off the back compounds to the front. The feather size one would end up shooting was the very shortest you could get away with that would still control a broadhead in a stiff cross wind, and account for a sloppy release. The arrow flight was supposed to be a little squirrely but be corrected by addition of the turbulator which in effect causes turbulence along the arrow shaft starting 1/4″ in front of your fletching. This made your small as possible fletching more effective as the feathers were able to “bite” into more of the turbulent air.
I have found with my own set up at around 32-34% UEFOC that I do not need them until my feathers get REALLY small:) I have one set fletched with 1 3/4 x .5″ feathers in a 4 fletch. The FOC on those are at 34%. I found I need the turbulator to stabilize the small fetching for hunting. Boy are they quiet with the small feathers!
Jans
I can’t add ANYTHING to that!
Ed
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I realize we’re largely in the academic realm at this point, but I’m still trying to wrap my head around this, so bear with me (and I didn’t major in physics…). How does turbulence ahead of the fletching create more pressure, and thus more stable flight, than clean airflow would? I always thought it was just the opposite. I would think that turbulence would create less consistent pressure on the wing, and thus less consistent “bite” of the feather in the resulting airflow. What am I missing?
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Now this is not a precise, scientific explanation of how a turbulator works, and isn’t meant to be, but it will help give you the concept of how the turbulator works.
When air flows over the shaft and fletching there is a layer of air called the “boundary layer” between the surface of the shaft and much of the feather’s surface, where the air is relatively undisturbed. The air will flow smoothly in this thin boundary. Addition of a turbulator forward of the fletching ‘trips’ this laminar airflow, creating many small swirls of air. These swirls are now pressing on the feather’s surface laterally; from the sides of the feather. This increases pressure between the feather’s surface and the air, increasing the drag created on the feather surface. Think of pinching the sides of the feather between your thumb and index finger. The harder you squeeze the feather the more resistance it causes on the feather’s surface, increasing ‘drag’.
Hope that helps.
Ed
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Thanks, Dr. Ed. That give me lots more to ponder, but that was a great explanation.
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This is odd.
From my reading concerning turbulators and aerodynamics the turbulator actually reduces drag. Although surface friction goes up from the turbulent airflow, it is more than offset by reduction in overall drag because that turbulent airflow delays separation of the boundary layer airflow from the surface.
If I recall correctly O.L. Adcock was experimenting with turbulators to assist in making some of his flight archery records.
The problem with them is that in order to achieve optimum results they can’t just be placed where ever you want.
Here’s some additional reading on them:
http://en.wikipedia.org/wiki/Turbulator
and:
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Of course there is a Wiki page devoted to ‘turbulators.’ Why didn’t I think of that? 😉
Thanks for that link, Bender – that Wiki page offers a really good explanation. It makes more sense to me now. I can also see how the benefits might be quite subtle, but beneficial nonetheless.
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Sorry, but I wasn’t at home for the weekend.
If I remember right O.L. wrote about it on TG, but it was pulled.
He said it would be like on an airplane wing. The wing is on the backside created as a tearoff edge (turbulator) so air flow becomes turbulent, goes under the wing and lifts the plane.
For an arrow: The feathers job is to stabilize the arrow. They are doing this by draggging (acting as a brake). The more air drag the fletching has the more it will stabilise the arrow.
So you can glue on bigger feathers or you increase the air drag.
I played it with wood arrows. The turbulator made the arrow acting stiffer, just like lowering the brace height. It’s not 5# but it’s noticeable.
I’m also not a physician, so I hope I explained it right.
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tg2nd wrote:
If I remember right O.L. wrote about it on TG, but it was pulled.
🙄 Unfortunately, not surprising…
Anyway, thanks for all the contributions, folks. I’m going to play around with them and see if I notice any differences.
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Yes the whole purpose is of course to create turbulence. Its what you DO with that turbulence that matters. So I guess that by proper placement one could create a net INCREASE in drag as in Dr. Ashby’s explanation, OR one could create a net DECREASE in drag, such as when they are used in aircraft.
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Bender wrote: Yes the whole purpose is of course to create turbulence. Its what you DO with that turbulence that matters. So I guess that by proper placement one could create a net INCREASE in drag as in Dr. Ashby’s explanation, OR one could create a net DECREASE in drag, such as when they are used in aircraft.
Now you’re cooking!
I’m trying to not get too technical here, but the effect a turbulator creates on a moving object can be either to increase pressure or decrease pressure. Say what? Yes, the ‘net effect’ of how the turbulator affects the moving object depends on where the turbulator is placed and the profile of the object. First, one needs to recognize that there are basically two types of ‘drag’; “skin/surface drag” and “profile/form drag”. Turbulators are used to increase the ‘surface’ drag and/or reduce the ‘form drag’.
The classic example of turbulator “net effect” is the golf ball. The dimples on the surface of a golf ball act as turbulators. They both increase the surface drag and decrease the form drag. However the net effect on a golf ball is reduced drag. Why? The ‘form drag’ results from the ‘wake’ a moving object creates. In the case of the golf ball the form drag begins just back of the widest portion of the golf ball. Thus, there is a sizable area (more accurately, volume) of form drag. Though the golf ball’s dimpled surface (the turbulators) increases surface drag on the portion of the golf ball being pushed through the air it also disrupt the air flow at the edge of the golf ball, creating a turbulence in the air which help fill in the ‘void’ just behind the ball, thus reducing the ‘vacuum effect’ behind the golf ball. This is also why long-range bullets have boat tails and is one of the (many) uses of air foils (‘spoilers’) on race cars. The reduce the form drag.
Now, think about the shape of our fletching. There’s not very much ‘area’ behind the fletching, so the form drag is minimal, and they don’t create much of a ‘wake’ immediately behind the fletching. (As an aside, the vertical trailing edge of the A&A fletching creates less turbulence – less form drag – than any other trailing edge profile on fletching – which also makes them more silent in flight.) However, our fletching has a lot of surface area. By placing our turbulator forward of the fletching we are increasing the surface drag significantly. The net effect of increasing surface drag when ‘form drag’ is minimal is going to be an increase in total drag force.
It’s hard to make a complex explanation simple but I hope that helps clear up the different effects of a turbulator.
Ed
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Gotta wonder what the cavemen would say to that! Or the Indians for that matter but . I love the technology for what it is but I had good luck without the feathers before I could afford them 50 years ago squirrel hunting. I don’t know but were things that much better then?
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Ok, correct me if I’m wrong here. So, using a turbulator essentially creates more drag due to the turbulant air flow over the feathers. Correct ???
This lets us use the smallest feather possible with the same affect as a bigger one. Correct ??
Ok, here’s the big question. Is the FOC gain really that great to warrant this ??? Is there really that much difference from 3×5 inch to,say, 4×3 inch ??
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Archer38 wrote: Ok, correct me if I’m wrong here. So, using a turbulator essentially creates more drag due to the turbulant air flow over the feathers. Correct ???
This lets us use the smallest feather possible with the same affect as a bigger one. Correct ??
Ok, here’s the big question. Is the FOC gain really that great to warrant this ??? Is there really that much difference from 3×5 inch to,say, 4×3 inch ??
Yes it is! But you also need EFOC or better UEFOC arrows.
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bearbowbob wrote: Gotta wonder what the cavemen would say to that! Or the Indians for that matter …
An interesting thing is that turbulators are found on ancient, pre-historic aboriginal boomerangs. For years these were thought to be merely decorations but more recent wind-tunnel testing has discovered that these are deliberately placed scorings that create a turbulator effect, increasing both flight time and stability.
We ‘moderns’ ain’t as far advanced from primitive man as we like to think we are!
Ed
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bearbowbob wrote: Gotta wonder what the cavemen would say to that! Or the Indians for that matter but . I love the technology for what it is but I had good luck without the feathers before I could afford them 50 years ago squirrel hunting. I don’t know but were things that much better then?
Well, considering that many Native American tribes (among others) used high FOC arrows, short r/d bows, and some even apparently used much smaller fletching than what we consider “standard” today, I’d say that we’re mostly re-learning what was pushed aside as the enthusiasts of our sport chose to focus on other archery “traditions” throughout much of the 20th century. Not much that’s truly all that new here, really.
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Bender wrote: An arrow stabilizes with both drag AND spin. Out of curiousity, any idea what a turbulator does to spin?
On arrows in the upper EFOC range and into UEFOC I use a straight, A&A pattern fletch; no helical and no off-set. The natural curve of the feather creates enough spin to stabilize even very large broadheads. The A&A fletching is very small, with small surface area. I’ve never tried to measure the spin difference. Rather I tune the fletching size to be the minimum that will stabilize the broadhead to be used, under all wind conditions.
There is also some question as to whether any spin is needed at very high levels of FOC (at all practical ranges). The PNG natives, shooting arrows in the upper 30% to low 40% FOC range use no feathers, and their arrows appear very stable in flight. To be consider also is the very long shafts they use. The significant surface area of the shaft would also provide a large ‘surface drag, factor; much greater than what we have on our shorter, smaller diameter shafts.
Ed
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Smithhammer wrote: I’d say that we’re mostly re-learning what was pushed aside as the enthusiasts of our sport chose to focus on other archery “traditions” throughout much of the 20th century. Not much that’s truly all that new here, really.
Amen, Brother.
Ed
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Now this is interesting. Long story how it came about, but I got to have a conversation with a guy that is into model aircraft. He applied turbulators to his T-45 jet model aircraft. At first he didn’t have them, but then later did apply them. He simply placed them in the same place and orientation as they are on the real jet, but to scale of course. Sure enough, just like on the real ones, he got a slightly slower stall speed, that is the wings maintained lift and stability at slower speeds and/or greater angles of attack. The effect DID scale, AND produced a measurable result.
No, spin is not strictly “necessary” for stabilization. But I also know I want all the help I can get. 🙂
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Ok…. i’m still getting used to the idea of actually testing out this EFOC thing. I have always been a strong believer in the spin of an arrow having a significant role in the stabilization of arrow flight. But… i was doing my tests with high speed arrows with low FOC at 10-12% at distances of a 100 yards.
Being a relatively open minded person, with a love of adventure, i have decided to play with an EFOC set up and test it out thoroughly against my moderate 15-18% FOC set up.
That being said, would it be safe to say that when using less FOC, more helical and arrow spin plays a bigger part in stabilizing arrow flight VS EFOC philosophy?
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kirkll wrote:
That being said, would it be safe to say that when using less FOC, more helical and arrow spin plays a bigger part in stabilizing arrow flight VS EFOC philosophy?
Kirk –
Good on you for deciding to get first-hand experience and figure out what works best for you. I know that may sound obvious, but I’m continually amazed at how many people reach their conclusions before doing what you are…. 😉
I can’t speak for everyone’s experience with FOC – even amongst those of us that are sold on the benefits of high foc arrows, there are still a variety of opinions when it comes to appropriate fletching. But in my experience, I agree with what you say above. Basically, the more you steer the arrow from the front (with high point weight) the less you need to steer/stabilize the arrow from the rear.
Personally, I’m shooting 4 x 2-1/4″ fletch, with just a very slight offset, and the natural helical of the feathers. And they visibly spin in flight. I currently have 25% FOC, with 300gr. up front.
Even when I used larger fletching, I never used much helical. A need for a significant amount of helical and offset in order to acheive good arrow flight is, imo, an indication that I need to revisit my tuning.
Please keep us updated with your experiments – we all can learn from this.
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Smithhammer wrote: [quote=kirkll]A need for a significant amount of helical and offset in order to acheive good arrow flight is, imo, an indication that I need to revisit my tuning.
With an arrow having a FOC in the upper EFOC range, or greater, that says it all!
When trying for UEFOC it becomes a balancing act. Sometimes adding a VERY SLIGHT amount of fletching offset allows a shorter fletch to give complete stability, under all wind conditions, and that can save a few grains of weight at the arrow’s rear. As the FOC enters the UEFOC range, and trying for maximum FOC, every grain shaved off the arrow’s rear becomes important. Other than that, with feathers, straight fletching is all that’s ever needed on arrows in mid-EFOC, or greater, range.
Ed
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