Advice for fixing false weak spine

[Kyle85]

I've got a new Poison Dart on my hands - beautiful work by Buddy Gould, will share pictures at some point.  It's a 62" 2-piece Longbow pulling 53# @ 28", I pull 26.5", am comfortable in my stance and form, and started tuning up some Traditional Only shafts in 400 and 500 spine.  All shafts showed up weak with 50 and 100 grain inserts, 150 and 200 grain points, arrows cut from over 28" to 27 1/4" and all combinations therein.  I somehow wound up fletching 3 of the 400 spine shafts at 27 1/4" with the 50 grain inserts - that show up weak with either weight point when bare shaft - and fly... OK at 10 yards, but I can see that tail flicker side-to-side. 

I did fix the original nock high early on by slowly inching my nock point down, and now they're an inch or less high and I called it good.

I did try a 300 spine shaft that also showed up "weak" but it also jumped high a couple of times, which I attribute to bouncing off the shelf and kicking up. 

Bow came with velcro side-plate, that I replaced with a strip of stealth tape.  Tape shows no signs of wear at all after all the shooting.

Brace height is 7.5" per bowyer recommendation, and I've checked and adjusted as my new D97 string settles in. 

Shooting 3-under.

I have a bunch of 400 spine shafts that shoot well from my 60" 51# @ 28" centaur with 28" shafts with 100gn inserts and 200gn points, so I decided to believe in my "false weak" hypothesis and ordered a dozen 500 spine shafts to start over with and if 400 is better I'll do that, but I suspect 500 may be the key as the centaur is cut to or past center, but the Poison Dart is cut before center. 

Any advice from the peanut gallery?  Did I leave any considerations out?  The 400 and 500 appear equally weak - I am shooting bare shaft into a block target, not through paper.  Any thoughts or crazy ideas welcome.

[Smguinnip]

Maybe try and make your shaft shoot stiff to confirm or eliminate a false weak reading, lower the point weight by a good bit, and if you have anything that you could add as a heavy string silencer that would slow the string down (beaver balls) closer to the center of the string. If these things stiffen the shaft, then the shafts are truly weak. If there is no wear on your side plate, then it’s possible that the arrow is flexing around your riser and coming off weak. Every bow has its own personality.

[Kyle85]

Yup, I tried the 300 spine with 100gn points and that's when I got the high bounces and otherwise still read "weak" (nock left on RH bow). Currently running dynapuff silencers.

I'll just start with a 30" 500 spines and work back from there lol.

[Smguinnip]

What distance are you bare shafting at? I’ve found that with a higher FOC arrow, they will start to correct themselves in flight, kinda like having fletching on them. I would check the bare shafts at 5 or 6 feet to see what they are doing as they are leaving the bow, possibly coming out weak and correcting them selves at longer distances. Funny how this tuning stuff can be fun and annoying at the same time.

[Kyle85]

I've been shooting at 6-10 yards

[McDave]

The main thing that jumped out at me from your first post was that you are cutting these arrows very short.  I realize that your DL is 26.5”, but I have found in general with carbon arrows that they perform best at longer lengths, say 29” and up.  They need enough length to bend, i.e. achieve archer's paradox.  I know this isn't very scientific, and you can ignore it for now, but if all else fails, try tuning to a 29” arrow.

[Kyle85]

OK why not? All else seems to have failed for the moment, thanks for the tip!

[Orion]

Hmmmmm.  A 500 with 200 grains up front should be great plenty for your set up.  I'm thinking the arrows are slapping off the shelf, causing a fish tail, which registers as a tail left weak spine at 5-10 yards.  I assume you're not plucking the release, which would cause this.  The other possibility might be a too low brace height (regardless of the bowyer's recommendations).  Raise the brace height a half-inch and see what happens.   

[Longtoke]

I think Orion is on to something.  I would guess your weak reading are flalse and are from a too stiff of an arrow smacking against the bow and flicking outward on tail end making it look weak.

could be wrong but that is my best guess.  shoot through some paper,  use a slomo camera if you have one. 

 if you are getting weak readings with 4oo spine cut short  i think it is a false positive. 
i would guess a 500 spine arrow someone around 28 inches with a 200-250ish grain head would be in the ball park

maybe even a 600 with a 170-200grain head?   

if you were to use a 400 spine arrow cut short to draw length at that draw and that poundage i would expect a 300-400 grain arrow tip.  i think you are getting false readings from the arrow slapping against the shelf.   

[MnFn]

l think Orion might be right. I went thru a period of time where My arrows were constantly showing weak. I had to shoot around 78# before they were ok. I don’t remember the bow weight I was shooting at the time but the problem was in my form, I was torquing the bow when I shot.

After I figured that out I was able to drop back down to a more realistic spine with good flight.

[Kyle85]

Thanks everyone.  When the shafts come in I'll try increasing brace height and I'll start with a long 500 spine arrow and work back to see where that takes me.  I'll report back in a couple of weeks when I have time to chase it again.   

[Kyle85]

UPDATE:

The 500 spine shafts came in, and I made two pairs of arrows - both 28" with 50gn inserts and 200gn points - two at 400 spine and two at 500 spine.  I lengthened my brace height to 8", then lowered my nock point a little more and BAM - all weak spine errors disappeared completely with both arrow types. 

However, I still get a nock high.  I tried switching to 150 grain points and got no difference in spine read or nock read.  I tried lowering the nocking point a little bit more, but the arrow already appeared canted upwards to begin with, so I didn't go very far (1/8") and it didn't seem to help.  I tried going back up higher again and instantly got the weak spine error again. 

When I shoot all the bare shafts at the new-normal nock height with zero weak spine error I get a strong nock-high, and proceed to shoot a bunch of 400 spine fletched shafts at the same distance (~7yards or so) and get a slight nock low, which I attribute to a slight over-correction by the fletching after coming off the shelf high.

Is it me here with a bad release? 

Is it possible this is a limb timing issue - i.e. a disparity between stiffness of the top and bottom limb of the bow?

Do I just fletch some shafts and call it a win?  That feels like giving up - the nock is way out of whack and I can see the fletched shafts porpoise-ing in flight.  I feel like I'm close but I'm not sure what I'm missing.

[Kyle85]

Also, I wanted to express my gratitude to you all for the useful advice - it's helpful to pull from the experience of so many people! 

[Kyle85]

OK I poked around old posts on fixing nock high and changed 4 things at once! 

I didn't have a bottom nock set so I added one. I was shooting off velcro, which I replaced with a Bear rug rest and added a toothpick under the rug at the crest / high point, then I put two more twists in the string and let it rip and BAM - fixed my nock high.

...but then I was back to the very weak spine error   

I let the two twists back out and raised the nocking point a bit, and the nock height stayed OK and the weak spine improved some, but jeez is this a picky bow!  Probably just need some more little fiddles but I think I'm closer than I was at least.

[Michpatriot]

The main thing that jumped out at me from your first post was that you are cutting these arrows very short.  I realize that your DL is 26.5”, but I have found in general with carbon arrows that they perform best at longer lengths, say 29” and up.  They need enough length to bend, i.e. achieve archer's paradox.  I know this isn't very scientific, and you can ignore it for now, but if all else fails, try tuning to a 29” arrow.

This was my very first thought! I've had arrows start to tune almost at the rest\rug..and never act right..weak stiff weak stiff..nothing to push against maybe? but then I move up a spine and add 2" in length and they bare shaft perfect..I CAN NOT SHOOT SHORT ARROWS!!! For reference I shoot 32-1\2" carbon length 350spine from a 40# marked bow that I draw to 30" hang 3+ or so inches to the point in front of the shelf..and they shoot like darts bare!

[Kyle85]

Hmm... I did try a 29" 500 spine arrow and that showed very weak as well, perhaps I can just try a 30" 500 and see where that takes me.  I don't have any long 400 spine shafts, but maybe I should bite the bullet and order some of those as well. 

[Wheels2]

Increasing brace will cause the arrows to act even stiffer.  Higher brace equals slightly shorter power stroke and less energy imparted to the arrow.

[Terry Green]

Stay after it Kyle....

Food for thought.....

When you have 4 things to change, change one at a time.  That way you will know what change worked.   

[tbird-51]

I’ve been reading this thread for a bit and just had to give my thoughts. Whenever I struggle with something as you are, I’ve found that if I set up my camera in video mode, I often see things happening with my form that I did not realize was happening..such as, string pluck, improper back tension, and a big one, bow hand grip and follow through. With your bow# at your draw length, a 29-29.5” 500 spine arrow with 225-275 grains up front should fly if form is correct. Just my thoughts, not a professor on the subject, just 30 years of tinkerin.

[Kyle85]

Terry,
    Your advise is eminently reasonable and shows sound judgement and profound wisdom.  But... you know... I wanted to be BOLD!!

Tbird, thank you.  Maybe I'll try the 500's some more before giving up on them. 

Went to the range yesterday where I could let the arrows stretch their legs out to 25 yards.  I fletched one each of the 28" arrows in 400 and 500 spine, with 50gn inserts and 200gn points.  400's flew much better at that length, and the shorter 400's I made earlier flew even better.  500 would kick sideways hard before correcting eventually.

Bare shaft 500s hit the far right of a 5' wide target at 20 yards, and one of those was a 29" shaft.  I'll try some other combinations including some longer arrows in both spines too and play some more.  Thanks again!