Archery Talk Forum banner

1 - 17 of 17 Posts

USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #1
Acronyms we often use

AMO = Archery Manufacturers Organization
ATA = Archery Trade Association
BH = Brace Height or string height
DL = Draw Length
DW = Draw Weight
FOC = Front Of Center (how far the arrow's balance point is in front of the middle of the arrow's length - expressed as a %)
GPI = Grains Per Inch
HDS = Hoyt Dovetail System. The patented name for the ILF system we use.
IBO = International Bowhunters Organization
ILF = International Limb Fit Also known as the HDS
NP = Nocking Point on the string (also known as Nock locator)
OTF = On The Fingers
PW = Point weight (in grains)
TD = Take Down
TP = Target Panic

USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #2
Bow lengths and weights demystified

Riser, limb and total bow length.

For MOST ILF Olympic gear, risers come in 21" 23" 25" and 27"
There are a few risers out there that are 24"

ILF limbs come as Long, medium, short and extra short.

Very often the limbs have noted on the dovetail section what length bow would result on a given length riser or (H)andle
25" riser + long limbs = 70" overall length.
Medium limbs = 68"
Short limbs = 66"
Xshort = 64"

23" riser + long limbs = 68" overall length.
Medium 66"
Short 64"
Xshort 62"

And of course going to 27" riser add 2" to the 25" numbers.

FYI how AMO defines bow length is actually based on the string length + 3" to get a specified brace height. So most strings will be about 3" shorter than the listed bow length.

Bolt on limb systems are similar. Risers come in various lengths as do their limbs. Most are final bow lengths of even numbers.. Some bolt on limb systems are proprietary, some use the same bolt/pin patterns. Mix and matching MFG's is at your own discretion.

Weight Ratings on limbs are usually listed on the dovetail or lower limb face. While some manufacturer's will vary, most take their rating somewhere in the mid range of their limb bolt adjustment (ILF). Bolt on limbs are generally NOT adjustable. Most ILF risers have an adjustment range of a few pounds each way.

Ratings are given a poundage on a specific riser or bow length. AMO states that the draw weight will be measured at 28" AMO Draw length unless otherwise specified.

Shorter bows (often 48"-58") are often rated at a 24" DL

Many Custom built bows (older bowyers) will have the rating at a different DL. Something like, "36# @ 27" "

To get a calculated APPROXIMATE DW

If your AMO DL is longer than 28" you would add 2 lbs per inch (approx) beyond 28"
If your AMO DL is shorter than 28" you would subtract 2 lbs per inch less than 28"

A better way to find your DW OTF is a bow scale.

USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #3
Archers Paradox

Technically "archers paradox" or "The Archers Paradox" is the term "Straight as an Arrow". The paradox is, When we release an arrow, it is NOT straight.

What causes it to be bent? and how does that affect us? That will also be explained with the "dynamic spine" post.

When we draw the bow back, we store a great deal of energy in the limbs.
Regardless of tune and everything else, when we let go, (or release the string) all that energy has to go somewhere.

In a perfect world, the bow would be perfectly tuned. the string would begin it's travel forward in a perfect straight line (is your "bow in plane") and the arrow would be sitting perfectly center shot.
Your release would be perfect and all of the energy would be directed straight towards the target, STRAIGHT through the arrow and to the arrow point.
With all this energy being perfectly focused through the walls of the arrow towards the target there would be even pressure on both walls of the arrow and it would not collapse in any way and the arrow would stay perfectly straight. In this perfect world, the arrow walls would not compress at all and 100% of the energy would get transferred to the propulsion of the arrow and it would go exactly where it was aimed.

In the real world, our tune is never "perfect" and our release is never perfect. So lets presume you got a pretty good "eyeball setup" with your bow. (won't go into that here)
For a right handed archer, As you release the string you WILL push the back of the arrow towards the left. Because we are trying to put the energy somewhere, Arrow wall material can be compressed (to a degree) and we have to overcome inertia, (point of the arrow is heavy and doesn't want to move) the energy will cause the rear of the arrow to move before the front of the arrow. Because we "pushed" the nock end of the arrow to the left, it will start to move to the left. This will cause the arrow to "buckle" a little and bend with the middle of the arrow moving to the right.

Once we overcome the static inertia of the point of the arrow and now the whole arrow is moving forward, there is no longer enough force or energy to keep the arrow bent, The arrow will try to straighten out or recover from the bend we just put in it. With nothing to keep the recovery from stopping once it is straight it will flex and bend the other way, back and forth until all that energy is expended. Usually most of the way to the target..


USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #4
Dynamic Spine vs Static Spine

Static spine is a measurement taken by resting an arrow shaft on 2 points and hanging a weight in the middle of the span.

The amount of deflection created by the weight is what the measured spine is.
AMO (see above) in the effort to standardize manufacturing and marketing put forth some guidelines that all MFG's now follow for rating their arrows.
In simple terms, the larger the spine number, the weaker the arrow's spine is.
There are several different standards being used by different MFG for this measurement and actually differ a little with different materials. This will be in a different post.

Dynamic spine is a little harder to define but it is the affected amount of flex or bend created when an arrow is released from the bow.

So what affects dynamic spine? Just about everything.

As mentioned so many times FORM trumps a great deal of other things. Bad release, slow release, dropping the bow arm early, creeping, overdrawing, plucking the sting, peeking as you release, etc... All these will affect any tuning attempts you make.
This is why above I mentioned that part of the equation for help should include your "level of shooting/experience" as well as a score (which would be an objective indicator)

On the setup side, Centershot, tiller, brace height, actual draw weight (weight on the fingers). nock height, string material, string construction, strand count, serving type, length, things attached to the string, nock locator type, arrow static spine, stabilizer type and weights, etc etc etc.. You get the picture?

Things we as archers can change as far as arrows and bows that drastically change arrow spine(discounting form here)
spine - larger number = weaker dynamic spine
arrow length - Longer arrow = weaker dynamic spine
Point weight - heavier point = weaker dynamic spine
nock weight - Heavier nock = stiffer dynamic spine
Fletching - Heavier fletches = stiffer dynamic spine
arrow wraps - addition of arrow wraps = stiffer dynamic spine.

Things on the bow we can easily change

Draw weight more weight = weaker dynamic spine
Addition of a stabilizer = stiffer dynamic spine

slower strings (more strands or material change) = stiffer dynamic spine
thicker or more center serving (makes the string heavier/slower = stiffer dynamic spine
Nock locator, lighter (such as tie on locators) = weaker dynamic spine
setup Center shot, plunger etc.. Use tuning manuals to assist with this and bare shaft tuning.

Brace height - while this does affect dynamic spine I try not to use this adjustment for this as it also affects a lot of other parts of the tune. Primarily how the arrow releases from the string.

Resulting patterns shooting a bare shaft with fletched arrows MOST OF THE TIME.

Weak shaft pattern will appear with the bare shaft to the right of the fletched group. (assuming a RH shooter)
Stiff shaft pattern will appear with the bare shaft to the left of the fletched group. (RH)

Things that can throw off your test shots are of course are form, bad releases, clearance problems (some sort of impact arrow to riser) and improper setup (centershot, etc)

USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #5
Draw Length, Arrow length, AMO, methods, spine/numbers

Draw length

There are several ways people measure DL.

The preferred method is using a marked arrow, pulling it to your anchor point and having someone read the side of the arrow.
While it is used by many shops, and unfortunately it's in our Certification books the wingspan method is one of the least accurate ways I have found to measure DL.

There are several "variations" we often get to DL which make it very hard to help in discussions. The best method to use is the AMO standard since so many of the rest of the tuning info is based on this.

AMO describes actual DL as the distance from the base of the nock groove to the pivot point (deepest point of the grip) which is often the same as the rear plunger hole + 1.75"
AMO also describes the distance from the base of the nock groove to pivot point as DLPP or TRUE DRAW LENGTH.
So AMO DL is DLPP or True Draw length + 1.75"

Arrow length

Arrow length of an arrow is measured from the bottom of the nock groove to the end of the shaft, not including the point or insert.
Every so often you will see arrows measured as "C to C" or "carbon to carbon" or "Raw shaft". Usually this means the shaft only. no points, inserts, nocks, or nock pins
Since points are not all the same length, the total length of your arrow can be different than someone else's arrow of the "same length"
Be aware that nocks, nock-pin configurations, and overnocks are not all the same so this can affect your overall length as well.

Easton and several other MFG's list the proper way to measure for arrows as 1" past the arrow rest for cutting purposes. this is not the number you should use for DL!

Reading the numbers on your arrow shafts

For MOST aluminum or alloy arrows the 4 digit number is the diameter and wall thickness. NOT SPINE.
The first 2 digits xx00 is the diameter of the arrow in 64ths of an inch. for example, 1716's would be 17/64" in diameter.
The second 2 digits 15xx is the wall thickness in thousandths of an inch. for example, the 1716's would have a wall thickness of 16 thousandths of an inch.
While this number number does help us define the spine, the material or composition of the alloy will affect it's dynamic and static spine.

For most Carbon arrows, and Al-Carbon arrows There is usually a spine listed. If not, you may have to look them up on the MFG's website.

For Carbon Impact Superclubs (since I have been using so many of them) the numbers relate to their approximate bow poundage rating.

ie: 5/15 is for bows rated 5-15lbs. I have found that if you are cutting them to anything less than 28" they will spine Stiff.
FYI Carbon impact Super Club Arrows spines are approximately
5/15 = 1500
10/20 = 1200
15/25 = 950
20/30 = 820
30/40 = 620
40/50 = 500

Carbon impact also has a line called UltraFast which actually has a few additional spines.
710, 550, 450, and 400

Desert Island Trading Co.
4,757 Posts
a few more

CW = Compound women
CM = Compound men
RW = Recurve women
RM = Recurve men


USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #11
More acronyms. (Thanks Warbow)

BOP = Back of Point, a measurement of arrow length from the nock groove to the end of the shaft in back of the point.

TDL = "True" Draw Length, measured from the string groove of the arrow nock to the position directly above the deepest part of the grip (in many cases also the center of the rear plunger hole)

DLPP = Draw Length to Pivot Point, same as TDL

USAA Regional-L4 Coach
4,312 Posts

USAA Regional-L4 Coach
4,312 Posts
Discussion Starter #15

344 Posts
Does the glossary include a definition of “clickflinchohcrap?”
I believe that falls under the definition of 'form analysis request' or something of that nature :wink: or maybe could have the acronym of CFoC...similar to FOC but with with a whole new connotation!
1 - 17 of 17 Posts