Stolid Bull Black Thunder and Hex 5s tuning issues

Kerf

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I have a conundrum.
Until recently I was shooting my Stolid Bull 25? ILF riser with medium Hex 5s 38# limbs pulling 39 OTF. 8125G 18 strand string. Brace height 7 7/8?. Nock height 1/2?, true center shot and zero tiller.
My arrows are 27 3/4? ACE 570 spine with 100gr break off points, Easton pin nock, Beiter #2 asymmetric nocks and GasPro 1.75? shield vanes.
Total arrow weight = 296 grains (well above Borders? recommended weight). GPP = 7.58 and FOC = 15.3%. I shoot three under barebow.
That was my ?best tune? but the bow was NOISY and I couldn?t group bareshafts. Lower BH gave me contact with the riser and plunger setting and tension made no difference.
I know from others on this forum and Border themselves that neither the Sids nor Holger (who makes the BT) recommend pairing this riser with Hex limbs above 6 but Holger has a video of him shooting the BT and Hex 5 limbs.
Taking Sid?s advice, I have now changed the string to a 14 strand FF.
This significantly changed the tune. The bow is now pulling 35#, the arrows were acting (not surprisingly) stiff, my BH had to go up and the bow is still noisy. No matter how I fiddle I can?t get bareshafts to group - I even tried some old ACC 3L-04 spined for 36#, and both sets of arrows going porpoising down range no matter what nocking point height I try!
I?ve been trying to tune this rig on and off for pretty much a year now and I?m completely stumped.
I?m considering going for some suitably spined heavier arrows that will give a GPP over 10 to see if that improves matters.
Or perhaps some more conventional profile limbs - CVXs perhaps?
Or, heaven forbid, changing the riser - maybe a Tempest?
I?d be grateful for the thoughts of any wise heads out there..
Thanks in advance
Kerf
 


Timid Toad

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HexV need a much higher by than most of the following Hex series, so you're heading in the right direction - I shout my HexVs off an 8-8.5" bh, 68" bow. Personally I'd stick with the 18 strand string. 14 is ok for short bows and Hex 7s or 8s. For me anything less than 18 is torturing my bow.
Sounds like you have contact between arrow and bow. This will produce noise and make arrow appear to be stiff, as well as make it flap about all over as it leaves the bow.
Firstly work out what's hitting what. My guess is it's the nock hitting the riser around the rest. If you can't eliminate contact, you probably need a different spine. Get some cheap singles to play with or borrow a few.
 


Kerf

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HexV need a much higher by than most of the following Hex series, so you're heading in the right direction - I shout my HexVs off an 8-8.5" bh, 68" bow. Personally I'd stick with the 18 strand string. 14 is ok for short bows and Hex 7s or 8s. For me anything less than 18 is torturing my bow.
Sounds like you have contact between arrow and bow. This will produce noise and make arrow appear to be stiff, as well as make it flap about all over as it leaves the bow.
Firstly work out what's hitting what. My guess is it's the nock hitting the riser around the rest. If you can't eliminate contact, you probably need a different spine. Get some cheap singles to play with or borrow a few.
Thanks Timid Toad. (I did thank you at the time but the forum revamp seems to have made it disappear).
My tuning problem is now solved. The solution was ..... heavier arrows
I was shooting ACE 570 spine with a grain per pound value of just over 7.
I had done the lipstick and talc test and could see no evidence of any arrow/riser contact.
Someone suggested the arrows were too light so I tried some heavier ones with a total weight of 459 grains giving me a GPP of 11.7. Result - an instantly quiet bow and bareshafts grouping with minimal tuning. They fly like lasers with only minimal detriment to my sight marks. But comfort over speed, as they say.
I’m guessing the lighter arrows just weren’t sucking up enough of the bow’s energy and the noise (and inability to tune) were the result of effectively dry firing the bow.
 


Timid Toad

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Great you are happy. Incidentally, what spine and point weight are your new heavy shafts?
 


Kerf

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Great you are happy. Incidentally, what spine and point weight are your new heavy shafts?
Became of a mix up I ended up with two sets of new arrows!
Easton Full metal Jacket Deep Six Injexion - GPI 9.8, length 31.5”, spine 400, Deep Six insert, 100 gr point, Easton G nock and Gas Pro Olympic Efficient vanes. Total weight 459 grains, GPP 11.78.
Easton FMJ Match - GPI 9.4, length 31.25”, spine 450, Carbon One 120 grain break off point, Carbon One nock pin, Beiter asymmetric pin nock, Gas Pro vanes as above. Total weight 421 grains, GPP 10.78.
Went through the tuning process and found a BH of 7 3/4” was the sweetest. Nock point at only 3/8” (I shoot three under barebow). Pretty much true center shot.
Both sets shoot as well as each other, group very well and the bareshafts of both fly into the group too. I’m at a bit of a loss to understand this but as you have said in another post, Border limbs are quite forgiving of spine.
I also tried a few different strings and found Angel Majesty 777 gave the best balance between speed and noise tho the noise difference was marginal as the bow is now extremely quiet.
Kerf
 


Timid Toad

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And along the way I suspect you've shot a lot of arrows and learned a lot about your shooting and your bow :D
 


Kerf

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And along the way I suspect you've shot a lot of arrows and learned a lot about your shooting and your bow :D
You are spot on there. It’s been a frustrating and ultimately rewarding experience which has taught me much. I understand my technique and my rig so much better. I am now at peace with my bow and really enjoying this wonderful sport once again.
 


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