Does a Broadhead change arrow spine?

[capt eddie]

I was bareshaft testing some arrow shafts today.  The shafts were showing perfect to slight stiff. Out to 27 yard they still hit within 3 inches.  So I thought that I would try a broadhead and see what type of flight I could get.  At 13 yards the BH was 5 inches weak.  I changed the plane of the BH several ways to check alignment.  Any way that I turned the BH I got the same result. 5 inches weak. The Bh and the field point were both 300gr. And the BH is only 3/4 inch longer then the FP. Should I adjust the weight of the BH to get the shaft to fly slight weak.  I also tried a snuffer BH with the same results.5 inches weak at 13 yards.

Did you shoot the broadhead on the bare shaft?

If so, dont do that anymore! Weird and dangerous stuff can happen with a BH on a bare shaft!

Do your bare shafting with field points until everything is just right, then shoot BH's on fletched arrows to verify that fly good and go to the same place.

Bisch

[Pine]

2X what Bisch said

[bigbadjon]

A broadhead of the same weight will not change the spine of a shaft. It will magnify unmatched spines and arrow straightness issues though. Like the others said a broadhead needs a fletching wider in the back than the broadhead or the front of the arrow will steer and cause all sorts of erratic flight.

[capt eddie]

I have the safest of settings for this type of experimenting. And there is nothing within 50 yards of this target.  I used a three bladed snuffer as well as a ribtek.  They both flew the exact same on two different shafts.  The FP was straight down the middle.  The BH were 5 inches to the right.  Nock left.  Should I just fletch them up or get the BH to fly a little heavier?  Thanks guys.  I knew that I would get some slack for the BH.  But I live in the country and this is not my first rodeo.  Just my first carbon bronco.

[BigJim]

Even when broadheads are of the same weight as a field point, they may fly slightly different due to them being wider and longer. The larger the head, the stiffer the shaft needs to be..typically to achieve the same quality of flite.
Shooting a bare shaft broadhead...other than being dangerous won't tell you a thing. As the shaft paradoxes around the bow, the broadhead will catch air and there is no feathers to help stabilize the arrow (field points don't catch nearly the same amount of air). The bare shaft broadhead will then try to swap ends if possible or at least fly erratically from side to side.

The excessive tuning is only really necessary to make a broadhead tipped arrow fly where we look and to the same inpact as the field point arrow.

Even if the arrow is a little stiff for the field point, you will likely never notice as it doesn't take much to make a field point arrow look like it is flying well. I read hundreds of posts and work with many people that mention how their arrows "fly like darts" with field points but are bouncing off the bow...making terrible racket and wearing out the shelf/sideplate material or have many other maladies that are un noticeable until adding broadheads.

good luck, bigjim

[capt eddie]

Big Jim.  At this time in the tuning.  I have found that 300gr on the GT teeter between very slight stiff very slight week, down the center.  Even to 27 yards.  I am getting a pattern bareshaft that I would be happy to get with a fletched arrow. Within 3 inches.  And I know it is my form that makes the inconsistence. Is this where I should just fletch up an arrow or am I looking for a defined weak spine? That will stiffen up with feathers.  Yes These GT do fly better then anything else I have ever shot.Extra 75 gr shows more weak then I think I need.

[DaveT1963]

The final test for me is to shoot three BH tipped arrows and 3 field tipped arrows at the same spot out to 40 yards.  They BH arrows nd Field points should group together pretty consistently.

[KenH]

A broadhead does not change he spine of a shaft.  Spine is a function of the arrow's material, density/diameter and length.  A broadhead can change the balance of an arrow but not it's spine.

[Michael Arnette]

X3 what Bisch said!

[Michael Arnette]

That being said...I think that a BH changes spine slightly due to wind deflection. I normally bare shaft tune just barely weak with the field points and then select a BH of the same weight. I've found that different BHs tune differently as well.
Of course I always check as Dave said by shooting both together.

[**DONOTDELETE**]

Originally posted by capt eddie:
Big Jim.  At this time in the tuning.  I have found that 300gr on the GT teeter between very slight stiff very slight week, down the center.  Even to 27 yards.  I am getting a pattern bareshaft that I would be happy to get with a fletched arrow. Within 3 inches.  And I know it is my form that makes the inconsistence. Is this where I should just fletch up an arrow or am I looking for a defined weak spine? That will stiffen up with feathers.  Yes These GT do fly better then anything else I have ever shot.Extra 75 gr shows more weak then I think I need.

Definitely time to fletch them shafts... i think you'll find once you've got the spine tuned those broadheads will cooperate much better with fletching...... Big Jim nailed it...

[Pat B]

25 grains of point weight difference will change spine by 5#, heavier for lighter spine, lighter for heavier spine...at least with wood arrows. I don't shoot others.

[capt eddie]

Thank you to all that has responded to this thread. I will fletch some arrows up and see where we go from there.

[Diamond Paul]

A really long bh can change the balance point, literally changing the foc of the arrow, which may have an effect on dynamic spine.  Also, don't take for granted that a bh weighs exactly what it claims to weigh.  Sometimes they don't.

[Bill Carlsen]

If you fletch them and shoot them I bet your  broad heads and field points will shoot the same.

[capt eddie]

ell I fletched up two arrows.  One with a BH and One with a FP One bareshaft. The bareshaft flys straighter then both fletched arrows.  They both impact stiff left 3 inches at 20 yards.  The bareshaft is in the bullseye.  Sometime straight sometimes 1 inch stiff.  I put a 72gr nut under the FP and BH.  They fly perfect to the bulls.  The bareshaft is 3 inches weak. Do they make brass inserts for the GT?  I think that would solve my problems.  Any comments would be appreciated.

[capt eddie]

I just ran the numbers through 3 rivers spine calculator chart.  My bow had 88# dynamic spine and the arrows had 43.7# dynamic spine.  Where could I be messing up.  The Treestick is cut 3/16 past center if I am not mistaken.  Maybe the center cut is putting the arrow behind the center line.  Could this be possible?

[Diamond Paul]

I think most people find that a slightly weak bareshaft tends to give the best shooting arrow when fletched, since fletching effectively stiffens the arrow just a bit.  You might have a fletching contact problem if the fletched shafts are that far from a bareshaft that centers the bull; that arrow should shoot with fletchings.  Try rotating the nock and try different fletch orientations and see if that brings them in with the bareshaft.

[Diamond Paul]

Or raise the nock point just a little; it might be too low with fletchings and you are getting some kick off the shelf.