Questions for the tuners

[Camo6]

Hey all,

Have a question for the experts on my latest arrow build. I recently picked up a set of Evolusion Vantage shafts in 400 spine. These are a .204 diamater arrow designed by an Australian company.
Previously, I'd been shooting GT traditionals and had built some heavy arrows in .340 spine that sported 350gn up front but dropped pretty quick. This was fine as my hunting ranges with this arrow were expected to be very short but I wanted to build some faster, flatter shooters for lighter game.

So I went up in spine to a 400 in a .204 arrow to maintain foc. I've kept them full length as I reference the tip for aiming and added a 55gn outsert. I tried bareshafting them but am reluctant to put too much faith in that as I have only been shooting trad for a year or so. So I tried paper tuning and found that even at full length and the 55gn outsert, I still had to up the tip weight to 250gn in order to get neat holes, anything less was tearing stiff. So I'm back to a relatively heavy arrow with decent foc. I could probably drop back to a 200gn tip and lower the brace height but the high brace height has worked well for silencing the bow. It just seems to be a lot of point weight for a 400 spine.

Entering my specs into the 3 Rivers calculator recommends a 125gn tip to match the arrow to the bow. I know my form isn't perfect but surely not that inconsistent to get results wildly different to the 3 Rivers spine calculator. I've played with the PFF settings and they still don't bring me within 10#. The calculator doesn't have my bow or arrow in the selection charts but I tried to go with the closest options.

So, to pose my questions, do .204" arrows have a 'stiffer' dynamic spine when compared to a similar spined .246" arrow? Could my release be causing consistent stiff tears? Anyone else running similar specs? Would appreciate any advice from those that enjoy tuning their arrows. Apologies to those that think you should just shoot arras.


Bow is a LH Hoyt Satori 21" with Hoyt Trad longs. Shooting 52# at 29.5". BH is around 8.75". NH 3/8 shooting 3 under.

[katman]

What are the gpi of both shafts?

[Camo6]

The 5mm shafts are 7.1gpi. Pretty sure the GT trad 340s were 10.5gpi

[McDave]

The gpi of the GT 340 trads is 12.1

You're not going to get a significantly flatter trajectory until you get the arrow weight down to 10 gpp or less, which in your case equates to an overall arrow weight of 520 grains or less (520 grains / 52# = 10 gpp). With that bow, you could safely shoot an arrow of 8 gpp or less, but for a hunting arrow I wouldn't go much less than 9 gpp, which would give you an arrow weight of 468 grains.

The .204 diameter arrow might give you a higher dynamic spine than a comparable .246 diameter arrow, since the .204 would be closer to centershot, but the difference wouldn't be very significant. Since the Satori has an adjustable centershot, whether you are using the included shelf rest or an attached rest, you might as well adjust the centershot to the ideal position, which is where the arrow tip is just outside the centerline of the bow.

3/8” nock height would generally be on the low side for a 3 under grip.  If you were bare shaft testing, you could find the ideal nock height, but since you're not, I would set the nock height at 5/8”.

[Camo6]

Thanks for the advice, McDave.

My GT Trads were just the standard shafts which Gold Tip list as 10.5gpi not the Classic series.

I think I've resigned myself to the fact that I'll need to go to a 500 spine in order to get a flatter, faster shooting arrow for this bow. I suspect my 340s are shooting stiffer than I may have thought which is why I figured a 400 would cover my needs. I guess my main question is why the 3 Rivers calculator was so far off when I put in my numbers? I've done a bit of searching and it seems it should only be used to get you in the rough ballpark but even with the form factor maxxed I was still off by 10 pounds. I guess I'll chalk it up to experience and use these shafts for a high foc arrow and trial some 500s soon. I'm enjoying the arrow builds just as much as the shooting.

I'm running a PN Springy with an Accutune so adjusting centreshot is easy enough. Although the head on the shaft of the Accutune is wider than the berger hole so it bottoms out preventing true centreshot. I'll probably drill out the first couple of threads on the riser to give it more travel or just switch to the standard springy rest threaded shaft.

In regards to the nock height, I had been running 5/8" but the bareshafts I had shot were very nock high. Even when paper tuning there was a large high tear. Dropping it to 3/8" corrected this.

[McDave]

Seems like you're on the right track, Cam. Sorry I can't answer your question about the 3 Rivers calculator, but I don't use it. From my experience, you should be able to use a .400 spine with a heavier point, like 200-250 grains, or .500 spine with a lighter point, like 125-150 grains.  You may have to cut the .500 spine shaft back some to get perfect tune, but you have at least 1 1/2” to play with, if your draw length is 29.5” and your shaft length is 32”.  Granted, cutting the shaft will affect your POI if you use the point to aim, but having a flatter trajectory is going to affect your POI anyway, so you might as well kill two birds with one stone.

[Wheels2]

The thinner diameter puts your centershot off as compared to the .246" diameters.  tail left for RH shooters.
Makes them act weaker.
And not all arrows are truely the spine deflection as marked.

[Camo6]

Thanks for the advice, guys. I've got some 250gn vpa 3 blades that will suit these shafts and looks like I get to play with some 500s.