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Arrow Shaft Tuning for the Advanced Olympic Bow Competitor

George Tekmitchov Senior Recurve Engineer, Hoyt Archery, Inc.

International Technical Advisor, Easton Technical Products

How to Win Any Archery Competition in Two Easy Steps

•Step 1- Perform well enough physically and mentally to score a ten.

Step 2

•Repeat Step 1.

What is “tuning”?

• Tuning is the process of harmonizing the three elements of the archery system- the bow, arrows, and the archer.

• For example, a good bow and a good shooter cannot perform optimally with poor arrows. Each element in this three-element relationship, or triad, has equal importance.

Elements of premium performance arrows in order of importance

1. Consistent spine 360 degrees around the shaft (+/- .010” or 0.25 mm maximum)

2. Good nock end straightness (+/- .001” or .025 mm is OK)

3. Consistent weight- (+/- 2 grains is OK)

4. Good overall straightness (+/- .003” or .076 mm is OK)

Importance of spine

• A spine variation of as little as +/-.015” (0.3 mm) can cause a loss of 2 POINTS in a 12 arrow set (!)

How Spine is measured

• An 880 gram weight is applied to the center of the shaft, which is supported on 28” (711.19 mm) centers

• The amount the shaft bends under the weight is the “spine value” expressed in inches.

• There are special considerations for locating the nock end datum when measuring barreled shafts such as X10/ACE.

“Static Spine” vs “Dynamic Spine”

DYNAMIC SPINE

Arrow at Rest Arrow Under Stress

of Release

STATIC SPINE (Side Load) (Column Load)

Arrow Under Stress of Hanging Weight

(880 grams)

Direction of Force

Direction of Force

Why spine is important- Arrow Oscillation

The oscillation magnitude and rate are determined by the shaft spine. This

affects clearance and grouping.

Arrow Cycling

The consistency of this “cycling” depends entirely

upon consistent shaft spine.

A consistent shooter cannot compensate for inconsistent

spine.

Basic tuning

• The bare shaft planing test is an excellent starting point for tuning the recurve bow with finger release.

• Paper testing can give false information with the recurve.

• The bare shaft test does depend on consistent shooting ability.

Bare Shaft Tuning can help with:

• Correct shaft spine size

• Correct point weight

• Shooter consistency

• “porpoising” and “fishtailing” corrections

• Clearance problems

A bare shaft should have the same weight and components

as the fletched shafts.

• Add weight as needed to the rear of the shaft to compensate for the loss of the vane weight.

• Don’t shoot further than you can hold gold with fletched shafts

Consequences of centershot

misalignment include critical tune and false

stiffness readings

Nocking point/Porpoising

• The first thing to check and correct for is the nock point height. This controls porpoising.

Nock point

Determining proper basic spine with the bare shaft test

Arrow too stiff

• Increase point weight

• Increase bow weight

• Decrease string strands

• Decrease nocking point mass

• Use a less stiff nock

• Use lighter fletching

Arrow too weak

• Decrease bow weight (big effect!)

• Increase string strands

• Increase nock end weight (heavier fletching, use arrow wrap, heavier nocks)

• Stiffer nocks

Fishtailing

Fishtailing causes

• Shaft too weak

• Shaft too stiff

• Point too heavy

• Point too light

• Centershot incorrect

• Bad clearance

Arrow length • Generally, recurve setups are preferred

with not less than 2 cm of shaft (not including point) in front of the plunger at full draw.

• This is more forgiving of release variations.

Nock-to-string tension

• This is very important especially with lighter weight bows.

• Arrow should separate from string with a light tap. If it falls off under its own weight it’s too loose.

• If the arrow can pull the string more than 1.5 cm without releasing, it is too tight.

Consistent Grouping

Solving insufficient clearance

• Check rest and clicker clearance

• Check to be sure you have the correct spine

• Check nock fit on string

• Fine tune the bow

Solving excessive drag

• Increase point weight or overall shaft weight

• Increase bow velocity

• Decrease vane size

• Decrease vane angle

• Decrease vane flutter

History of the modern competition target shaft

• 1947: Californian Larry Hughes wins USA nationals with aluminum arrows made by Doug (Jas. D.) Easton.

• From 1950 through 1983, archery worldwide is completely dominated by the Easton aluminum

arrow. First, 24-SRT-X, followed by XX75,, and

ultimately, the Easton X7.

• 1960’s saw competitor shafts in fiberglass but with no real impact or particular success.

History of the modern competition target shaft

• First carbon fiber availability to sporting goods and consumer markets occurs circa 1969. Jim Easton makes an initial investment of $10,000 USD to facilitate further development by an early maker of the exotic material.

• 1971: Jim Easton and Aldila Corporation colloborate on the first carbon fiber arrow shafts. With these early arrows proving to be brittle and difficult to make straight and consistent, Easton started working on a better method to build a carbon shaft that could be straightened to better tolerances and survive impact with hard buttress materials. By 1982 this led to successful construction of the first A/C arrow shafts. (In the interim Jim also worked to incorporate carbon fiber in bow limbs, leading to the first successful carbon limb: the 1976 Hoyt TD2 used to win Olympic Gold in Montreal by Darrell Pace (USA).

• 1983: First Easton A/C shafts released, used in 1984 O.G. by Gold Medalist Darrell Pace (USA)

• 1987 Beman Diva won FITA World Outdoor Championship

• 1987 Easton develops A/C/E barreled AC shaft

History of the modern competition target shaft

• 1988: Jay Barrs (USA) wins Olympic Games with new Easton A/C/E arrow shaft

• 1992: Prototype X10 (“big barrel”) shaft built on ACE core sets new FITA records in 1992 but does not fare well in windy Barcelona- Sebastian Flute (FRA) wins O.G. with ACE shaft

• 1994-95: X10 developed and released in late 1995 in preparation for Atlanta OG

• 1996: Justin Huish (USA) wins O.G. with Easton X10

History of the modern competition target shaft

• 2000: Both Olympic Games men’s and women’s gold medals won with Easton X10

• 2004: Both Olympic Games men’s and women’s gold medals won with Easton X10

• 2008: Both Olympic Games men’s and women’s gold medals won with Easton X10

• All major outdoor recurve World Records set since 1996, and all Olympic medals (men’s and women’s) accomplished with X10.

Carbon Fiber (in)Consistency

• Aluminum alloy is still much more consistent in specific stiffness-Young’s Modulus (E)- than even the highest grade carbon fibers

• This resulting lack of stiffness consistency requires workarounds and compromises to ensure excellent spine properties

• One of these workarounds is weight codes

Understanding weight codes

• You cannot have perfect spine AND perfect weight consistency with carbon fiber arrow shafts. One or the other must be compromised.

• It is easier for end users to segregate shafts by mass weight than by spine.

• This is why Easton groups high-end shaft production runs by weight.

Understanding weight codes

• Variations leading to the need for weight sorting are not just limited to CF variation

• There is also resin system and mechanical variation to contend with

• Only a 100% weight-sorted AND spine-sorted CF shaft can approach the consistency of aluminum

Understanding weight codes

• Easton strives to minimize the number of weight codes for each shaft series by continually improving processes and materials without compromising the tunability of shaft models over time

• C3 is the “center” nominal code for any given shaft size

Understanding weight codes

• All ACE and X10 weight codes cover a total spread of 1.5 grains (.097 gram)

• All packaged shafts are toleranced at +/1 0.5 grain

• It is easily possible to mix shafts from two adjacent weight codes with no ill effect (”heavy” C.2 and “light” C.3 for example)

Understanding the Barreled Shaft

• Easton X10 & ACE are barreled

• This gives aerodynamic advantages

• This improves clearance

• It also makes the shaft more forgiving to an inconsistent release

• It does, however, require some special considerations- especially in selecting centershot

Tuning the Barreled Shaft

• A small change to the nock end can have a big effect on the overall shaft spine reaction - but, beware!

Barreled shaft tuning guidelines

• When first setting up shafts, leave them 2 cm long to allow adjustment.

• When adjusting the nock end of the shaft, only trim 4-7 mm at a time- the stiffness will change very rapidly past a certain point which varies with every user.

• Most X10 shafts stiffer than 550 spine should be run “down the middle” for centershot reference.

White Board Discussion

• Shaft design and nock end stiffness

• Nock End Datum

• Fine Tuning Guidelines

• Point component bonding and tuning considerations

• Nock considerations and tuning impact

Fine Tuning

Plotting chart

Document the setup

• Write down all the important measurements !

• Nocking point height

• Brace height

• Tiller

• Bowstring material & strand count

• Correct draw weight

• Distance from clicker to button

Arrow troubleshooting

• Straightness

• Nock straightness

• Nock indexing

• Loose or damaged point

• Loose or damaged fletching

• Damaged shaft

• Arrow mass weight consistent?

Fine Tuning- Nocking point

• This is done first. Move the nocking point up by 0.8 mm.

• Plot the result. Write down the adjustment!

• If improved, move another 0.8 and repeat.

• Re-zero and repeat process in other direction.

Fine tuning- left-right impact

• Adjust cushion plunger pressure with small increments

• Always take notes!

• Look for arrows that do not group with the others

Fine Tuning

• Number the arrows individually

• 50 meters is a good distance

• Warm up before starting

• Shoot 6 to 10 fletched shafts and plot the group

• Write down the number of each arrow on the plot chart

• Repeat 4-5 times

Fine tuning- Important points

• Always install all accessories on bow as intended for use. If you change a major accessory you should recheck the fine tune!

• Good quality arrows and nocks are absolutely essential to a good fine tune.

• A change to the archer (form, draw length, hand pressure, etc.) can cause a change to the bow reaction and the tune.

Fine tuning- important points (cont.)

• Change only one variable at a time!

• Always take notes.

• Repeat testing on another day to ensure consistency.

• Don’t try to fine tune in poor conditions or when not shooting/feeling well.

• Fine tuning will often change the bare shaft impact point. This is the new, “correct” impact point for that specific bow (not necessarily all bows you may shoot)

Propaganda

Yes, I do work for a living

Carbon ION

• H Series design & benefits

• Short Draw light Poundage

• Straightness +/- .003

• High Precision (HP) insert (Patented)

• 2 sizes: 600 & 500

• Direct fit “H” Nock

• Factory Diamond Crested

• New for 2012

• Ultimate compound bow field arrow

• Point end tapered as X10; parallel at nock end for added tail spine

• 9 Sizes: 380; 420; 470; 520; 570; 620; 670; 720; 770

• Optimized for performance in all targets

• New for 2012

A/C PRO FIELD

Hoyt History • Earl Hoyt Sr. and Earl Hoyt Jr. founded Hoyt in

1931 (Father & Son)

• The Hoyt archery company was originally based in St. Louis, Missouri USA.

• The first Hoyt products were wood arrows

• Easton acquires Hoyt in 1982.

• Hoyt moved offices to Salt Lake City, Utah USA in 1983 and then moved all manufacturing to SLC in

1990.

From 1931 to present day, Hoyt has innovated more archery products

and has been awarded more patents than any other archery company in

history. • Hoyt has more than 20 Archery patents and many

more currently pending. For example • Stabilizers in 1961 • First Carbon Wood Limb • Syntactic foam core material for use in recurve limbs – 1986 • AIM String System • “TEC” bow riser design in 1996 • Split limb systems in 1996 • “Cam & ½” cam system in 2003

Olympic Success

In 1972, the first archery Olympic competition in modern times was held. Hoyt Won all gold medals in both the men and women’s competition.

In every Olympics since, Hoyt bows have won medal after medal and have dominated the competition with the majority of all athletes using Hoyt bows.

Dynamic Flex Control

•Controlling the In-plane Flex and out of plane Flex and why it matters.

Paralever Pocket

• ~40% Reduction in Stress in the Riser

• More Stable Platform for the limb

• Less Vibration within the System which promotes a more stable and consistent shot.

Geometry of a Recurve

Bow

Formula F7

•The Fastest Formula Series limb

•Triaxial Carbon

•Enhanced recovery rates

•Optimum Torsional Stability

•All temperature performance

What’s New

Enhanced Geometry that produces a smoother draw cycle.

Less Vibration

Steadier aiming and holding

More consistent grouping, More forgiving

Hoyt Tough Bow Testing

Dryfire testing 80lbs @ 30” draw

(90 ft*lbs minimum)

Dryfire Standards(Minimum):

Handle = 1500 dryfires!

Result = Toughest most durable archery system in the industry.