Weighted inserts spine?

[Shleprock]

Do weighted inserts change the spine of the arrow?

[jbuck9]

Yes they do, if you need more weight up front ,I like too use a heavy adapter for the B.H.
 Adding weight up front weakens the spine.

[amar911]

Weighted inserts don't actually change the spine of the arrow, but extra tip weight will weaken the spine and make the arrow shoot like it has a lower spine. That is because a heavier tip increases the inertial resistance of the front of the arrow, so the shaft will bend more as it tries to force the front of the arrow to start moving. Some people refer to this as the point "pushing back" on the arrow as it resists the force of the limbs acting on the string to move the point forward. The word "inertia" comes from the Latin word "iners" which means lazy. An object with mass is said to be lazy and doesn't want to change its velocity or direction unless a force is exerted on it. The higher the mass, the greater the force that is needed. Thus, a greater force must be exerted by the limbs, through the string, then through the arrow shaft, in order to make a point of heavier mass begin to accelerate forward. When that happens, the force being exerted longitudinally through the arrow shaft will cause it to bend more laterally and thus make the arrow behave as if it had less bending resistance (i.e., a lesser spine). Actually the spine stays the same but more bending takes place because a higher peak force is being exerted on the shaft.

Allan

[champ38]

Ive got to where I just avoid the brass inserts, that go up in the shafts, when bare shaft tuning. I use a heavier head and an adapter to add wt to the front. Last time I tried tuning with the inserts, i was ready to pull my hair out before I was done....I use the Bemans and the inserts (100gn)are inset approx 2-3 inches, I know they effect the spine..just dont know HOW they affect the spine..??

[Richie Nell]

I just got finished with my last hair.  I have pulled them all out.  I've been shooting several hours today trying to get me bow, 70lbs @ 30.75 in., to shoot a 31" CX 350 with 100 grain inserts and 250 grain head.  NO STINKING LUCK.
I have moved silencers down, built out the side plate. NO LUCK.
After moving nock point up and down I can't even get the porpoising to stop. UNBELIEVABLE.
I am missing something OR I am barking up the wrong tree because it is not supposed to work.

What stiff, narrow, carbon arrow WILL work with my bow and 300 + grain heads?

Anyone? Anyone?

[amar911]

Richie,

I can tell you that I have been shooting AD Hammerhead Trads with either 100 grain brass inserts and no screw-in weights on the back of the inserts or 100 grain brass inserts with 70 grains of screw-in brass weights on the back of the inserts. I also am using aluminum collars over the end of the shafts between the shaft and the brass insert, and I am using uni-bushings and g-nocks along with 4" four fletch at the tail end. I have 300 grain heads on the arrows. My draw length is a little shorter than yours at 29 1/2", and my arrows are 31 3/8" from the throat of the nock to the front of the brass insert. The bow I shoot them out of is a 60" Super Shrew 68#@29 1/2". I get great arrow flight. The Hammerheads may not be "narrow" by your definition, but they sure work well for me. I also shoot a lot of Carbon Express arrows. They are really nice but are more sensitive to bow variations than arrows made up using the AD shafts.

If you go over to the Dark Continent forum you will see some more information about heavy arrows from heavy bows. Also, you might give Paul Mattson at Badger Arrows a call. He has a lot of experience with arrow selection. Hope this helps.

Allan

[katman]

Richie, my guess is your soft in spine, decrease point weight or add another set of silencers to the string or lower brace height. You may try the grizzlystick safari's, seriously stiff arrow.

I have found that a 300gr point with aluminum insert vs a 200gr point and 100gr brass insert do not have the same dynamic spine on the same arrow, putting some of the weight in the shaft stiffens the dynamic spine for me. Has anybody else seen this?

[Richie Nell]

Thanks guys....Allan, I really like the narrow diameter of the carbons.  I normally shoot the fat 2317's and they shoot very well.  I just wanted to try a stiff narrow carbon. I thought the CX 350' would do the trick.

Katman....I haven't added silencers but I have moved them toward the middle. No significant change.  However I haven't lowered the brace height. Actually I raised it back to 9 inches (it gradually lowered to 8.75) where I normally keep it where it is the quietest.  Maybe I need to lower it a bit.  The CX's currently have the 100 grain inserts.  Based on what you have said  the arrow would be even weaker if I used the aluminum insert instead.
I have ruled out the Grizzlystiks because of price and large diameter like my 2317's.  
I don't know if it is possible but ideally I would like a super stiff and light arrow where I could add a pile of weight to the front, which is where I want it.
Your input is really appreciated guys...I hope I can reciprocate.

[mscampbell75]

I havent used the brass inserts, but I questioned using them on a recent tuning post to get my point weight up because my shaft was overspined .  He is how it was explained to me.

The extra legnth inside the shaft (lenght of the longer brass inserts) in now rigid.  We know for sure that the part of shaft where the longer insert make contact with the shaft at will NOT bend, effectively makeing the flexible part of shaft shorter.  ie:  a shorter shaft a stiffer spine.

NOW, take that same weight and put it out front of the shaft with a shorter insert, giving more  part of the shaft flexiblity, will give a weaker spine.  Plus, the extra wight is out front now , whick make the shaft act even weaker.

To me a brass inseret is a catch 22.  

More weight up front=weaker spine

Less part of the shaft being flexible=stiffer spine

Atleast that how me and the voices inside my head have in fiqured out.  I choose to stay away from them.  Not say they wouldnt work for you or anyone else.  

[Richie Nell]

So...if I could find something about six inches long that would fit tight inside the front of the shaft then it would be alot stiffer.

Any ideas?

[Soilarch]

Anything I can think of that would fit and be stiff will also be heavy.....meaning you still have to give up your heavy heads.

Here are some ways I know of to effectively stiffen the spine.  They all have trade-offs.

Add a fourth fletch (and go with longer ones)
Use a dacron string instead of FF
Use a heavier nock (or try to add "some" weight to the back of the arrow
Add weight to the string (more silencers)

Basically, anything to lessen the "thump" your arrow is getting up the rear by your bowstring.

[katman]

How much foc are you looking for?, I would think that with that length arrow 100 gr brass insert and 200gr heads you would be over 20% and into Dr Ashby's efoc as long as you do not have cap wraps and huge feathers. An extra set of silencers would rob energy from the arrow, might be worth a try tying on a second set of rubber whiskers and see if you can get the cx to tune, you have plenty of horespower in the 70# and 30.75 draw.

The grizzlysticks are very costly and have a large front end but are tapered and recover quickly which helps penetration. I have broken every shaft I have owned hitting something else besides the intended target except the safaris. The AD are also a very nice tapered shaft, I use them for 3D. The tapered shaft shoots better over a wider spine range and you may need that for your heavy poundage. Good luck on your search.

[Richie Nell]

"Anything I can think of that would fit and be stiff will also be heavy.....meaning you still have to give up your heavy heads."

If a long internal footing makes the arrow stiffer...the weight of the same footing will not weaken the spine like the heavy heads do..does it?

"How much foc are you looking for?, I would think that with that length arrow 100 gr brass insert and 200gr heads you would be over 20%"

Yes it is about 21% with that setup.  I could live with that if it didn't kick left.

It sure is nice to discuss this with lads that know more than me.

Thanks

[Soilarch]

Richie, you're correct, it's adding weight but not weakening the arrow.  The way I think about it is to think of it as supporting it's own weight.

Since you're asking about 300+ grain head I figured you're on the path to high FOC...and adding weight (by using internal footings) anywhere but the tip is kinda counterproductive. That's why I mentioned the weight.

[Richie Nell]

Soilarch,
"not weakening" or actually stiffening the arrow?

If a 6" internal footing will stiffen the arrow  then that may be all I need.  Then I could add good weight to the front to get whatever FOC it will allow. I have no idea if it will work but if it has worked for others I will try it.

I do plan on using 5 inch nanner turkey feathers but I don't want to do too much, if anything, to slow the arrow in order to stiffen it.

Thanks again.  
It sure feels good to solve all the worlds problems with such an inadequate thinker.

[Soilarch]

Can't answer that.  Not done it myself.  I read waaaaaay too much on here and other places.

Seems like it depends on too many variables.  It stiffens PART of the arrow...and effectively shortens the part of the arrow that does flex. It's kinda like adding weight and shortening your arrow. Taking an inch off the length of an arrow is a routine way of stiffening the whole shaft.  BUT remember your adding weight that the part of the shaft that does flex will have to support.

Confused yet?  Sorry I'm not a very good communicator.  

The answer I guess is that you have to try it, play with different lengths of footing and see if things improve.

[Richie Nell]

Good info.

thanks

[Hud]

Garlin, basically adding 25 gr. up at the head, insert or adapter, will change the spine on Aluminum arrows approximately 3-5 lbs. Example: if you go from 125 gr head to 150 gr. the shaft spine is 3-5 lbs lower.  Sometimes you can compensate by lowering or raising the string 5-10 twists. If your arrow weight is around 9x the effective weight of the bow, your arrow weight is good. Example: 9 x 65# = 585 grain arrow.

Richie, you mention a the brace height of 8.75" +/- is that what the factory recommends? My set for a 66# @28" Bear Custom TD is 7 3/8" which is lower than the factory and what most people use. But it works fine for my 29" XX75 2219's. Try a lower string with the stiffer shaft.

If the arrow kicks left of where your 2317 shoot, they are stiffer, weak would go to the right. If they shoot left, we can lower the string, or add weight. But, you already have 300 gr. at the head. That suggest the shaft may be too stiff period. Just the opposite if they are right. Make sure the nocks are not tight and lower the string.

Best flight from an arrow comes around 27". Arrows that are longer, or shorter may not shoot as well and certainly, won't be as stable in the wind. Increasing the forward weight changes the flight characteristics as well. Putting too much weight out front will result in a loss of trajectory. Imagine what would happen if you were shooting an arrow of 700 Grains. You might get great penetration, but your range would be limited to 30 yds. It has been my experience that if the balance point is more than 3" ahead of the mid-point (tip to nock), the arrow will drop faster than if it is more balanced.

[Richie Nell]

Whoaaa Nelly.....

"If your arrow weight is around 9x the effective weight of the bow, your arrow weight is good. Example: 9 x 65# = 585 grain arrow."

  Not if I want heavy more powerful projectiles.

"Richie, you mention a the brace height of 8.75" +/- is that what the factory recommends?"

  Yes..that is what Black Widow recommends and it seems to be the quietest at that point. However I am not opposed to changing it if it helps stiffen arrow spine.

"If the arrow kicks left of where your 2317 shoot, they are stiffer, weak would go to the right. If they shoot left, we can lower the string, or add weight. But, you already have 300 gr. at the head. That suggest the shaft may be too stiff period. Just the opposite if they are right."

  I think you may have that backwards. I wish it would kick right, then all you kind and generous guys would not have to put up with all my ignorant questions.  My 2317's kicked right until the 300 grains I put up front weakened it juuuussssttt right. But they are still fatter than I would rather have.

"Imagine what would happen if you were shooting an arrow of 700 Grains. You might get great penetration, but your range would be limited to 30 yds."

  Yea..I don't want to shoot 700 grains...its too light. I shoot 750 to 950 grains from 30 yards with no problem whatsoever, as do many others.  To me, the drop or loss of trajectory has nothing at all to do with accuracy.  
I personally don't know many people who shoot animals much more than 30 yards with any arrow.

If my arrow shoots perfectly flat from 25 yards
away then my arrow is too light for my bow and I am waisting the lethal characteristics of the weapon in hand.

[Hud]

Richie, I think I understand what you want, but you are going where few have gone, "The Road Less Traveled". The manufacturers don't know you yet, and they don't see a demand. Have you contact any carbon guys to see what they have to offer?

If you get a chance look at the latest issue (fall) of TradArcher's World, the article by David Soza "Tuning the Carbon Arrow". Although he is working primarily with lighter weights, he may give you some ideas.