Heavier # limbs require WEAKER spine???

[GMMAT]

Kris:

Yes.  Too stiff (for the heavier limbs).  That's what is perplexing.  I bareshaft tuned the 50's a couple weeks ago.  The bare shaft that flies like a dart thtough the 50#ers is 30-1/8" long BOP with a 175gr. FP.  THAT arrow shows STIFF out of the 56# limbs.  When we went to the 31" arrow (everything else remaining constant, arrow-wise), it flew great.  Now....Have I tried the 31" from the 50#ers?  Nope.  They could very well fly great.

[Kris]

Jeff,

This whole thing can kind of become a word game, if you know what I mean?  I was actually curious to know what you see when a bare shaft tells you it's "too stiff", specially.

So you added 7/8" to your arrow going from a 30 1/8" arrow to a 31" arrow, which slightly reduced the dynamic spine of that shaft, and that longer bare arrow now flies through your 56# limbs, whereas the 30 1/8" did not, correct? And both these shafts had the same aluminum inserts with 175 grain FP's.

You are going from a 60" bow to 62" bow, which requires a different string.  Is your 62" 56# limbs tuned to these shafts as well as your 52# limbs are?  Different limbs will require a different brace height, nock height, etc. so tune the heavier limbs like you intend to have these shafts fly through them, at least.

You said you are drawing the two bows exactly the same length, just so you know that you are in fact, drawing the weight you think you are.  Often people going to a heavier bow draw shorter.
 
My point being, that what you may be calling "too stiff" is a function of variables that are not 1:1 between different weight limbs.  Your observations of "too stiff" maybe a difference in tuning or a misdiagnosis of "too weak".  I don't know you or your depth of experience with trad. gear and mean no disrespect by suggesting any of these things.  They are just some of the things I think about when tuning, plus a whole bunch more.  I have been shooting traditional for 35 years.

I went out tonight with my 57#@28" Silvertip TD, CX 250 Heritage shafts cut 29.5" BOP to trough of nock, w/50 grain brass inserts, fletched w/3, 5" parabolic fletches, tipped with a 125 grain Judo and had exceptional arrow flight, nothing I would come close to calling over spined or "too stiff".  I have also bare shaft tested the same arrow with similar results.  This means nothing for you and your unique style of shooting but is a similar comparable numbers wise.
 
A shaft I’ve had great luck with for this weight Silvertip is the Beaman MFX 400's.  You can bare shaft these out to 25 yards with perfect arrow flight with 100 grain brass arrow inserts and 175 grain FP’s.  A highly durable and accurate shaft as well.

Call me or write if you would like to talk further, sorry for the long response.  There are many variables that affect tuning and it is not often correct to attribute what we see, to one variable.  Always ask yourself more questions.
Good luck

[Apex Predator]

If you weren't sure you were not drawing the heavier bow less, I would have said that's your problem.

[Steve O]

I bet it is the extra length of the 62" limbs.  They are going to have an "easier" draw cycle and you will have a cleaner release both from the extra length and poundage.

[GMMAT]

Jeff,

This whole thing can kind of become a word game, if you know what I mean? I was actually curious to know what you see when a bare shaft tells you it's "too stiff", specially.

So you added 7/8" to your arrow going from a 30 1/8" arrow to a 31" arrow, which slightly reduced the dynamic spine of that shaft, and that longer bare arrow now flies through your 56# limbs, whereas the 30 1/8" did not, correct? And both these shafts had the same aluminum inserts with 175 grain FP's.

 That is 100% orrect.

You are going from a 60" bow to 62" bow, which requires a different string. Is your 62" 56# limbs tuned to these shafts as well as your 52# limbs are? Different limbs will require a different brace height, nock height, etc. so tune the heavier limbs like you intend to have these shafts fly through them, at least.

 Not sure what you're saying (I admitted being new to all this).  The string is different, of course.  We adjusted nock height when we bare shafted.  Same string make-up (both from Dave).  I don't shoot the same shaft (length) from the different limbs....so it's hard to say if they're tuned to the same shafts.  They're both 250's but you know the difference in length I mentioned.

You said you are drawing the two bows exactly the same length, just so you know that you are in fact, drawing the weight you think you are. Often people going to a heavier bow draw shorter.

 And I understand that.  If I didn't have my buddy there watching, I wouldnt be so sure.  

My point being, that what you may be calling "too stiff" is a function of variables that are not 1:1 between different weight limbs. Your observations of "too stiff" maybe a difference in tuning or a misdiagnosis of "too weak". I don't know you or your depth of experience with trad. gear and mean no disrespect by suggesting any of these things. They are just some of the things I think about when tuning, plus a whole bunch more. I have been shooting traditional for 35 years.

 No offense taken!!  I'm VERY new to all this, but my friend Page is a state champion shooter....and an accomplished personal bowyer.  He's won with the bows he's built.  He's the most knowledgeable traditional mind I know & have access to.  He's not all that perplexed.  I just wanted to understand it better.

I went out tonight with my 57#@28" Silvertip TD, CX 250 Heritage shafts cut 29.5" BOP to trough of nock, w/50 grain brass inserts, fletched w/3, 5" parabolic fletches, tipped with a 125 grain Judo and had exceptional arrow flight, nothing I would come close to calling over spined or "too stiff". I have also bare shaft tested the same arrow with similar results. This means nothing for you and your unique style of shooting but is a similar comparable numbers wise.

 One thing Page taught me is.....Brass inserts change everything.  I used to shoot 50gr. inserts....and then 100gr inserts.  I can tell you from experience that you can take 2 identical 250's cut to 30" and put 175gr. on both (one utilizing a 100gr brass insert and the other utilizing a normal insert and a 160gr head)....and you're subject to different flight/spine characteristics.  I just went through this with a set of arrows I now find useless!!....lol

A shaft I’ve had great luck with for this weight Silvertip is the Beaman MFX 400's. You can bare shaft these out to 25 yards with perfect arrow flight with 100 grain brass arrow inserts and 175 grain FP’s. A highly durable and accurate shaft as well.


Call me or write if you would like to talk further, sorry for the long response. There are many variables that affect tuning and it is not often correct to attribute what we see, to one variable. Always ask yourself more questions.
Good luck

 Thanks so much for the response.  I agree that EVERY little things affects something.

[WESTBROOK]

Tried it without the quiver yet??

Eric

[Kris]

Hey Jeff

Thanks for your nice response; you answered things in a very logical way.

Page sounds like an outstanding resource, he no doubt, knows what he's talking about.  I would utilize his expertise, as I’m sure you are.

So, I know more about where you are coming from, you are not far off on anything, for that matter.  What are you actually having a problem with?
 
You should be able to get good/great arrow flight with the 30 1/8” fletched arrow with your heavier limbs as well as your 50# limbs.

Which brings up another question; why are you shooting two different length arrows, to compensate for the BH, or, is that what you did to tune that shaft to your heavier limbs (i.e. left them longer)?
 
I have never been a fan of cutting arrows to tune them, I know what arrow length I need/want, and go from there.  A person still has many tools to work with w/o cutting, provided you’ve started with shafts that are spined in the ball park.  I would pick one arrow length that works for you, say 30 ½” and use other techniques to tune your shafts to the bow.
 
I wouldn’t worry if you can’t get 'perfect' bare shaft arrow flight (but it is a huge plus).  I hate to say it, but yes, fletching can/will correct for it.  I have found the CX Heritage series to be more difficult to tune than other carbon shafts, but admittedly have not used them as extensively either.  I think it might have to do with their wood grain wrap (purely speculation and my unproven opinion).
   
There are all kinds of tricks for getting an arrow to fly, and you touched upon one when you mentioned FOC or weight FRONT OF CENTER or FORWARD OF CENTER and that involves manipulating the amount of the weight at the front of your arrow.  It does several things and Page can probably tell you all about it.  Yes, it will change the dynamic spine and it is the rage right now for increasing penetration and improving arrow flight, in most cases.  It is a very useful and important tool to know something about.
   
There is good info you can read on all of this.  One resource is here on TRADGANG and is in the Ashby articles post by Rob DiStefano and is on the Main Forum.  You can write me a personal email address if you can’t find that specific info, as there are many updates to pour through.

 Another really excellent learning resource is by O.L. Adcock, and he’ll explain more about what ‘over & under spine’ means plus a ton more.  A must read!

 http://www.bowmaker.net/tuning.htm

This is all fun and once you get the hang of it, is totally addicting; you‘ll love challenging yourself to tuning arrows and bows.  I have not even scratched the surface on what you can do to make all this stuff work for you.  Welcome to the Club!

Sincerely - Kris

[foudarme]

just an idea, what do you think about that: your heavier bow is longer, your fingers are less pinched by the string, your release has become clearer, the resulting paradox is less important...you can shoot a weaker arrow !

[wingnut]

The proof will be the next step in the tuning process.  Leave the bareshaft testing behind now that you are close and go to broadhead testing.  Do the same as with bareshaft only shoot your broadheads and target points and compare group location.  If they shoot together out to 40 yds or so.  You are tuned and ready to go.

Mike

[GMMAT]

Thanks guys.  I ordered BH's Thursday.  We'll see.  I did orded 185gr heads.  Looking forward to building my first "real" trad arrow, myself.

I appreciate all of your replies.

[Greg Skinner]

I agree with Wingnut.  The broadheads will tell the real story.  I use the big 200 grain Ace as my broadhead for testing.  If it flies good, I figure I am OK as long my finished point weight is within 10 gr plus of minus. Of course you may have to do some mixing and matching of inserts, adaptors etc. to get the right weight combination.

[Don Stokes]

Jeff, the quiver can most definitely make your bow need weaker spine. I've seen it many times, and I don't use a bow quiver because of it.

My theory is that the heavier mass of the bow with quiver added (and your 62" limbs are likely heavier, too) makes the bow move a little more slowly to the side at the shot, so the arrow has to bend a little more to clear the riser. Anything that affects the overall mass of the bow affects spine to some degree.

Bows that are made less centershot (by building out the strike plate) require less spine than they did before. Likewise, bows that are made heavier in mass (by adding a loaded quiver or any other kind of weight) may require less spine than before. It all has to do with the shaft clearing the riser during the dynamic movements that take place when a bow is shot.

It follows that lighter mass bows are more sensitive to the addition of a quiver than heavy mass bows. A person shooting a bow that's relatively heavy in mass may not notice the effect of adding a quiver, but a person shooting a lighter mass bow probably will.

Don't get me started on string silencers...  

[GMMAT]

Thanks, Don.  I stated the EXACT same theory as yours when I was discussing this with Tommy (Rocky Mtn. Specialty Gear) the other day.  It made sense in my mind.  I've got some brass knobs coming for a new Silvertip riser I have on order.....and I'm betting even that causes me to have to shoot weaker spined arrows.  The extra riser length will also make a 60" bow a 62" bow (which will also make the 50# limbs 48#'s).  I'm anxious to see how it turns out.....and to stop the tuning merry go round.

[Bill Kissner]

In my opinion Bjorn got it right a couple pages ago when he ask if the string aligned the same. He was talking about the center shot. If the string aligns a little farther to the right of the side plate, it will affect center shot and require a lighter spine. The opposite is true if it aligned a little to the left. The difference would not have to be very much to make the spine change.