Pinwheel app for determining spine

[Bmoore]

Hey all, been contemplating an arrow build for a long time and decide before buying shafts I’d do a spine check. So I downloaded the software for archers xpert program on my laptop. Put in my arrow and bow info and it says 250 spine is a bit too stiff but 300 is really weak. Today at work I downloaded the pinwheel app for my phone which should be the same software and put data in there and it said 300 was optimal but on the weak side and 250 was way too stiff.
Anyone know why these would come up different values. Or otherwise have advice for which way to go?

bow is Obsession Turmoil
30” draw 68 lbs peak weight

Arrow idea is victory Rip Tko with 50 grain easton brass insert and 150 grain broadhead. Add a 10 grain iron will collar to make it bomb proof.
Wrap and 3 fletch blazers on the back with a lighted nock.
I tried adjusting arrow length from 28 which is shorter than I’ve run in the past out to 29.5 which puts the broadhead clear of the riser. The length made some difference but the patter still stands.
Any help with this would be great. At this point I’m just getting in my own head and not sure what to do. Paralysis by analysis for sure.
Thanks in advance.

 

[Mighty Mouse]

No idea why the mobile and desktop versions are giving you different results. I think you could get 250 or 300 spine to tune just fine. FWIW the spine calculator on Victory's website suggests 300 spine for a 29.5" arrow with 210 gr on the front and 50 gr on the back out of a 350 fps IBO bow at 68#.

 

[Bmoore]

Thanks for the feedback. I actually downloaded the software because victory website called for 300 spine but I had a gut feeling I needed 250. That started the downward spiral of overthinking everything in the first place.

 

[Bmoore]

So I’m messing with the phone app it seems I have two options that get into the green optimal range.
One is to turn the bow down to 65 lbs and run the arrow at 28” long. This gets 300 spine nearly in the middle but just slightly on the weak side.
The second is to turn the bow up as high as I can 70 lbs assumed for this, and run the arrow at 29.5 inches long . That puts me just barely in the green but heavy on the stiff side.
If thsi was your setup, what would you run? Am I putting too much weight on the software? Open to all replies. Thanks.

 

[Mighty Mouse]

IMO you're overthinking it and putting too much emphasis on the software's recommendation. Either of those arrow builds will work fine. I'd personally go with the 250 spine at 70# (assuming that's a comfortable draw weight for you). You could start with them a bit longer than 29.5" if you're worried about being too stiff and leave yourself the option of trimming them down later.

 

[4fletch]

Hey all, been contemplating an arrow build for a long time and decide before buying shafts I’d do a spine check. So I downloaded the software for archers xpert program on my laptop. Put in my arrow and bow info and it says 250 spine is a bit too stiff but 300 is really weak. Today at work I downloaded the pinwheel app for my phone which should be the same software and put data in there and it said 300 was optimal but on the weak side and 250 was way too stiff.
Anyone know why these would come up different values. Or otherwise have advice for which way to go?

bow is Obsession Turmoil
30” draw 68 lbs peak weight

Arrow idea is victory Rip Tko with 50 grain easton brass insert and 150 grain broadhead. Add a 10 grain iron will collar to make it bomb proof.
Wrap and 3 fletch blazers on the back with a lighted nock.
I tried adjusting arrow length from 28 which is shorter than I’ve run in the past out to 29.5 which puts the broadhead clear of the riser. The length made some difference but the patter still stands.
Any help with this would be great. At this point I’m just getting in my own head and not sure what to do. Paralysis by analysis for sure.
Thanks in advance.

With 210g on the front and roughly 29 inches c to c i would run the 250 spine. You start hitting near 70 pounds and up and 30+ inches on complete arrows 300 spine is eeeehhhh! Do not get me wrong i have done it and every old guy at the shop will chuck you a handful of 300 spine carbon arrows, but I would not do it now.
Mid to high 60 pounds with 29+ arrows is that tipping point on the calculators math between 300 and 250.
Ill shoot 300 spines with a total arrow of 30 and a half, 31 inches and 175g up front at mid to high 60 lbs. Crank up the weight point or draw and i switch to 250 spines.
This is more a personal choice based on a couple factors not perhaps what is "right".