Arrow spine question for long draw archer - 33.5 in Draw length

[Billy Goat]

Wow this has been a great response! Both on which spine arrow I should use and on whether draw length affects spine. Thanks everyone!

@TX_hunter thanks for the comparison charts. I am indeed running a 125gr point and the accutough insert that comes with the arrow is 24gr with the ballistic collar at 15.5gr. I have been getting a slight nock right tear when paper tuning and was wondering if it could be from spine being to stiff….Looks like I need to add some weight to the front of my arrow. Thanks!

You likely aren't getting a "too stiff" paper tear. A centershot compound doesn't need an arrow to deflect around the riser.

You likely need to shim your cams to get everything centered for your form.

 

[5MilesBack]

From some basic calculations, 3" of draw length is roughly equal to 10lbs of draw weight.

I've always seen most bows increase about 20fps with a 10lb jump in draw weight. That would equate to 2" of draw length. But like everything else with archery........that may very well depend on the equipment. Just like with my bows, generally I see a difference in 1fps for every 3.5gr added or dropped in arrow weight.........while some bows are closer to 3gr and some closer to 4gr.

 

[Syng2015]

Hey guys

Shooting a Mathews atlas at 74 lbs, 33.5 inch draw length (I’m 6’8” with 7ft wing span)

Looking at kinetic khaos 250 or 200?? Arrows will be uncut at 32in

The arrow charts only look at arrow length and poundage, does having a longer draw length than arrow length have an impact on when choosing a spine? Thanks!

As you up arrow length, it's assumed you are upping draw length to match, since most people don't put 6" in front of the riser at full draw. You can say it's built into most charts. If you cut short, right in front of the rest, you can lean a little weaker if you're in between spines.

 

[Jg48]

I would expect it to. Consider a guy with a 29" draw shooting 30" arrows versus a guy with a 33" draw shooting 30" arrows........all else equal. That's a 40fps difference in arrow speed, therefore more energy launching that arrow. That has to affect the dynamic spine.

I'm shooting a measured 32 7/8" draw at 75lbs. I'm currently shooting .250 spine Victory RIP TKO Elites with 200gr on the front with insert and point, but also have some Apollo 250's as well. I shot GT Kinetic XT 200's for a few years. I didn't find them very durable at all. I had several break behind the insert. If it were me I would look at something more like the Sirius Apollo's, especially if you go .200 spine.

I actually just measured my draw length on a board. 33.25 measured and measured 74.5 lbs. you have as close as probably anyone on here to my set up. sounds like you have shot both .200 and .250 spine. I’m specifically looking at Black Eagle X impacts with a Snyder core system from Iron Will. I just got the pin wheel app AND archers advantage hoping to get some clarification, but basically .200 is too stiff and .250 is too weak.

I’ve never hunted but that is my goal, to find a mentor and learn. I have no plans of seriously target or 3D shooting for anything other than practicing for hunting.

What spine would you personally recommend?

Thanks!

 

[Billy Goat]

You can't go too stiff.


If your draw length was shorter, or your poundage was half what it is maybe. Too much is made of "too stiff" compound arrows.

 

[Jg48]

You can't go too stiff.


If your draw length was shorter, or your poundage was half what it is maybe. Too much is made of "too stiff" compound arrows.

Interesting. So “too weak” is more of a concern than “too stiff”. That makes sense to me, but I’m a noob for sure. Thanks for the input!

 

[Billy Goat]

Interesting. So “too weak” is more of a concern than “too stiff”. That makes sense to me, but I’m a noob for sure. Thanks for the input!

Yes, too weak you will pull your hair out trying to tune. Unless it's a women's or youth bow, you won't have issues with too stiff in a modern compound for hunting.

 

[5MilesBack]

Personally, I've found the 4mm arrows to be more trouble than they're worth. Will they work? Sure. But with your specs I think you're going to experience some issues eventually. Having said that, I've never tried the Snyder core system. But I prefer simple and changeable. I wouldn't want my BH's permanently attached. I've been using .204" arrows (5mm) pretty much exclusively for the past 15 years using HIT inserts. As for spine.........start with the 200's, then perhaps you can play around with some 250's eventually as well and see which ones tune better.

 

[moxford]

Agreed with 5MilesBack; I like .204 for hunting and component selection.

Too stiff means heavier arrow, adjustments to FOC, less forgiving, less arrow speed. I was launching 700+ logs for a while, but backed down a bit and like it more. Did love the momentum, penetration, and quiet bow though!

6'6" 32" draw

Cheers,
-mox

 

[galamb]

If you are considering using the Snyder Core's then go with more spine and pick the insert weight that weakens the spine back to the level you are looking for.

Yes, it does add weight up front.

Yes, you will lose some feet per second but if you don't go insane with the weight up front it could be a minimal speed loss.

Depending on your target distance the extra weight could be barely noticeable all the way up to "I don't like the trajectory".

I don't pull as long or shoot as heavy as you but as an example, I can shoot a 30" 400 spine from my recurve and get perfect flight matched to my bow power. I can also shoot a 350 and not be "overspined" (which really matters on a recurve) simply by adding 50 extra grains to the front end. Doing so gives it the same effective (dynamic) spine as the 400 because that extra 50 up front weakens the spine.

(but the 350 is running 15 fps "slower" due to the weight required to weaken it)

Alternately, I can add a weight (onto a nock bushing) - put 20 or 50 grains back at the nock end and "stiffen up" that 400 if it is a little underspined for my application.

There is always a way to turn a little weak or a little stiff (if you are close to the crossover points in terms of static spine) into the spine you are looking for - but it does mess with the weight which will rob you of a few/many fps.

I find it easier to work "backwards" - decide what "end product" you are looking for and then use a spine calculator to build virtual arrows until you find the combination you either want (or can live with) if there is nothing "off the shelf" that will fit your needs.

 

[Hunt4Wade]

Hey guys

Shooting a Mathews atlas at 74 lbs, 33.5 inch draw length (I’m 6’8” with 7ft wing span)

Looking at kinetic khaos 250 or 200?? Arrows will be uncut at 32in

The arrow charts only look at arrow length and poundage, does having a longer draw length than arrow length have an impact on when choosing a spine? Thanks!

200 would definitely be what I’d go with. I’m running 250s with 78.2lb draw @ 30” with arrows cut to 29” and 150 grains up front. With the longer draw length and arrow length, I can’t see 250s being quite enough spine. Especially with any amount of weight up front.

Longer draw length and longer arrow both effect spine. Both of which are reasons for stiffer spine in themselves.