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help with tuning / spine for Hoyt CST?

835 views 9 replies 9 participants last post by  Arrowbender 
#1 ·
Hi all,

Longtime lurker, first time poster, thank you in advance for any help or advice you might have.

I don't have a lot of tuning knowledge, especially when it comes to arrows, and I'm having a problem that just seems weird to me.
Either that, or I completely misunderstood Easton's charts. Which, hey, sadly wouldn't be all that strange for me :wink:

Bow: Hoyt carbon spyder turbo, Z5 cams (number 3 I believe), 28 inch draw, 60 pounds give or take a few, Qad hdx rest (my first dropaway, I'm used to blades, but setup looks ok - it's dropping, no vane contact that I can tell from smearing goop on em), centershot at around 6/8

Arrows, I've tried the following:

Easton 2317 XX75 Camo Hunter shaft cut to 29 inches 125 grain head
Easton Bloodline 330 spine, shaft cut to 29 inches 125 grain head
Easton FMJ 5mm 400 spine, cut to 28 inches 125 grain head

The strange thing (to me at least) is, paper tuning shows that it likes the FMJ but the Bloodline and 2317 are showing left tears - weak it seems. I'd actually have expected them to be stiffer, or at least fine for a 60 lbs bow? Am I wrong?
What could be causing this please? Just them being the 1 inch longer makes that much of a difference? I shot weaker spines than these 3 out of my previous 60 pounders with no real issues...

(Also, I've no internet at home right now so I'll be checking in on this on my ancient flip phone thing but will not be able to respond til tomorrow - please take no offense if I respond slowly)
 
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#2 ·
Looks like you need a 340 spine if your gonna run that setup. That’s an aggressive cammed bow and your running 125 grains up front which weaken the spine even more. Cutting it one inch longer will make it even weaker since the spine rating is at 28”. Cutting it at 27” and running 100 grain heads won’t make it stiff enough either. You could even get away with a 300 spine if you run 125 grain head. The bloodlines or camo hunters should tune. Those both look optimum for your setup. Hope this helps. Goodluck.
 
#4 ·
Not really enough info here, there are a lot of reasons why you are getting a tear. A picture of each tear would help a lot. I have had quite a few 14 CST's, they are a great bow, but finiky to tune. The first thing I would do is remove that pretty wooden grip, but it is round. I like side plates the best on a Hoyt, you can tape it if you like, especially if it is too long after removing the wood. I am assuming you are getting a tail left tear, practice shooting with pressure more to the right side of the riser. You have yokes on this bow. if you are still getting a tail left tear, add twists to the left yoke (or remove from the right, most do 1/2 and 1/2) This requires a press, but work on your grip first.
As far as spine, 1 inch of length equals 25 grains of point weight which equals 5 pounds of draw weight. The 2 carbon arrows are about the same spine because the inch longer 330 cancels out the spine increase.Both of these shafts are weak, get some 100 grain points to test, or cut an inch off the 29" shafts.
You would do better shooting bare shafts through paper and at 20 yards with a fletched field point, it will tell you much more. Good luck.
 
#5 ·
1) Throw away thew Easton Tune Charts
2) The 330s should tune best. Strip all the vanes off your arrows and nock tune them through paper at about 7 yards and mark them for cock vane.
3) You will more than likely need to yolk tune to get the bullet hole with a bare shaft (this supports #1 above)
 
#7 ·
I really doubt it is the arrow giving you issues. Most likely inconsistency in your form. I have the same bow but with 65lb limbs and shot Injexion 400’s cut to 28” with 100gr points for several years with zero issues. Bow would shoot bare shafts and fletched arrows perfect out to 30. I have a #2 cam at 28”.

Also that bow won’t reach IBO with a number 3 cam at 28”. Trying some 100grain field tips would be the quickest way to figure out if your underspined, if it shoots better with them than either buy 100gr heads, add lighted nocks to the rear, cut 1” off of the arrow or buy new arrows.
 
#8 ·
With a hoyt, if you have a left tear, try putting twists in the left yoke and taking them out of the right. I have a tuning series coming out at Gold Tip that will cover all of this. It could be grip but as long as the arrow is stiff enough it should tune. Its all about where the sting hits the arrow and what influences that. If the arrows all shoot the same tear, within reason and can be nock tuned without to much trouble they are stiff enough
 
#9 ·
Well, it is time for you to learn how to tune your bow. Right now you are just sticking in different arrows and seeing if they will fix your problem. That really isn't tuning a bow.

We have specific tuning methods and you need to do your research and study how to do the jobs, most of them are going to require some cable and string twisting so a bow press is something you need access to.

I am a yoke tuner who uses a bare shaft and a paper tuner to get perfect arrow flight. To do this I move the bow string left and right to get it directly behind the arrow rest and that is done with leaning the cams with the yokes. This is just a little short explanation of how I do it. I do have a full write up of that tuning method and it works for a hybrid cam like the one you have.

As far as arrow choice, I would be perfectly fine choosing the two carbon arrows that you have and tuning your bow with them. The 330 spine is the more popular choice of the two but the 400 spine will tune perfect also.
 
#10 ·
Thank you all for the advice, lots of things I'm going to have to try.

For now, short version is I've moved centershot to between 6/8 and 5/8 and that's cleared the left tear for all 3 arrows, but it's not really where I'd have expected center shot to end up so I'm going to look at yoke tuning when I can get access to a press. I also still need to take the time to nock tune as well, I should be doing that anyway.

Re other fixes- 100 grain points didn't help, turning the bow down a few lbs didn't help (that's still weird to me), and I went back to my Faktor to see if I'd forgotten how to hold the Hoyt grip but that bow was still shooting clean holes with how I held it. I removed the grip on the Spyder anyway, didn't help the tear but I did like shooting it that way.

So I guess the arrows are fine as far as general spine goes and form is OK enough for consistent holes at least so I need to either get to a press and try the yokes or accept the odd center shot.

Re pictures of tears back when the center shot was at 6/8- no camera or smart phone, sorry.
You'll have to take my word for it, paper tuning fletched arrows at +/- 12 feet:
the 400 FMJ at 28 inches +125 grain head shot a perfect hole, The 330 bloodline at 29 inches + 125 grain head had a small but clear consistent left tear , and the 2317 at 29 inches with 125 grain point had a left tear of an inch or more so ragged it looked like I threw it through the paper myself.

I just expected it the other way around, really. I should maybe just shrug and go with the FMJs but I've only three left and I don't love the HIT system inserts what with me being a klutz with such things.

(Not going to bareshaft - a bareshaft aluminum arrow that I hadn't noticed got bent ended up so ridiculously far off the mark, I mean entire yards at no distance at all, that I'm traumatized for life and onlookers still rib me about it years later - I did mention the klutz part:embara:)
 
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