Is there a rule of thumb for "xx" grains increase in point weight will decrease the spine by "xx" pounds?
I know there are other tuning factors such as how close the bow is cut to center and the length of the shaft, but I'm just looking for a place to start.
I used to shoot bows 55-60 lbs, and now I'm down to the 40 pound range give or take (both longbows and recurves). I've got several dozen wood shafts in the upper 50 to upper 60 pound spine. They are various woods-- fir, poplar, chundoo, split hex pine, and even some coyowood shafts that I would like to use if I could tune them to the lighter bows. If I can't tune them to the lighter bows, I'd rather sell the bare shafts than start messing with making arrows and then find out they are still too stiff.
Thanks.
Might try playing around with the Stu Miller calculator (3Rivers has a version of it)
Put in your info and then just change the point weight to see what gets you close to matching your needs.
The designated spine value on wood shafts is for a 28" arrow with a 125gr head. For each inch over 28" subtract 5# of spine weight and add 5# for each inch under 28". For each 25grs over the 125gr point subtract 5# of spine weight and for each 25grs under 125gr add 5# of spine weight.
Pat B, very good info... thank you.
Thanks--both of you guys. That's just what I was looking for. Between leaving the shafts longer and increasing point weight I should be able to get those shafts tuned to my lighter bows.
You may find that will all vary depending on the bow. Jumping from 125 11/32" heads to 190 grain heads can get different results with different bows. With some bows, I can see no difference from 125 to 145 grain target heads. Extra length in arrows also will give different results for different bows. head weights have more effect on longer arrows than on shorter arrows, you get more waggle per grain with extra long shafts. i imagine there are still a bunch of guys with odds and ends down there in SC. My son Cody use to shoot at the club grounds connected to the grave yard a lot. He was home, here in OC this weekend, he shot most of my bows, I noticed that his 1.5" longer draw required a few major changes in arrow spine requirements for the particular bows.
Pavan--I know Cody through some mutual friends. I've shot with him a few times. I think we may have shot the Nebraska Trad shoot with him once too. That range by the graveyard, Tryhedron, is closed now and I sure miss having someplace close to shoot.
I've got a few different bows so I expect some variation--I was mainly trying to determine if tuning was in the realm of physical possibility.
it is, but in the long run specific arrows for each bow would be better. You may need to go to 190 grain field points if you have been accustomed to 125s. Cody now lives in Des Moines and is a CPA/Auditor for the Marsh McLellan company.
Yes, every bow is different as is every shooting style. The closer you are to center shot the less critical the spine usually is. Also have specific arrows dedicated to each bow. I shoot mostly selfbows without a cut out shelf so the arrow has to be able to paradox around the bow. The formula I gave works well for selfbows and glass bows but tune the arrows to your style of shooting and a specific bow for best arrow flight. I've used the formula for doweled shafts as well as cane and hardwood shoot shafts. With cane and hardwood shoots you also have to consider the natural taper. That alone can reduce the effective spine by up to t 10#.
For me 35 grains of point weight for a 5 pound change in spine works. That would be for example if a 50-54 pound spine range and 125 grain points worked for you, 55-59 pounds of spine would call for 160 grain points.
This is a timely thread for me.
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Quote from: Pat B on June 22, 2019, 12:51:25 PM
The designated spine value on wood shafts is for a 28" arrow with a 125gr head. For each inch over 28" subtract 5# of spine weight and add 5# for each inch under 28". For each 25grs over the 125gr point subtract 5# of spine weight and for each 25grs under 125gr add 5# of spine weight.
Am I missing something????? Isn't this a**-backwards????
For each inch over 28", shouldn't you add 5# spine?
For each 25gr if point weight over 125, shouldn't you add 5# spine?
If you add shaft length or point weight, you are weakening the arrow, and as such would need to increase shaft spine, correct?????
Bisch
Disclaimer: I AM NOT A WOOD ARROW GUY!!!! That is why I am asking.
Bisch--You are right about the effects, but the GOAL is to weaken the arrow. My shafts are over-spined for my lighter bows.
Between 125 and 190 gr, I found that 7gr point weight needed about 1 lb spine. It varied some with shaft spine, heavier spines took more point weight. When I went above 200 gr points, the increase in spine really slowed down. Going from 225 gr Tuffheads to 300 gr only upped spine need by 3-4 lb.
I shoot 160 and 190 grain points all the time. They are mounted on 45-60# spined arrows and are shot out of 30-43# bows, both recurves and longbows. I don't worry about what spine charts or experts say. I know they all will shoot straight out of any of my bows because IMO spine is not that critical, nor is grain weight. Every archer/bow combination is capable of accurate shooting with 15-20# spine and 50-75 grain weight variation. Unless you possess shooting machine qualities you won't be able to tell the difference.
So that said in your situation Scott S adding point weight will help you use your existing shaft supply as well as making your arrows longer but I'm not a fan of that since that changes your aiming functions in secondary vision. I always keep my arrow length the same and just shoot. You will gradually weed out any consistent errant flyers.
Another thing you can do is use the stiffer spines in center cut bows and the lower ones in non center cut ones.
Also, the most important thing to remember is figure the entire length of your shaft. If it's a 28" bop arrow it uses a 29" shaft so that automatically decreases ones spine by 5#.
Just shoot and enjoy, it's not rocket science!
Well said, Kelly. I agree with all of it.
A 28" arrow is measured from the back of the point to the bottom of the nock if I'm not mistaken so the spine value of that arrow is for that 28" arrow, not a 29" arrow even though the actual length of the shaft is 29" or slightly less.
Quote from: Scott S. on June 23, 2019, 10:18:40 AM
Bisch--You are right about the effects, but the GOAL is to weaken the arrow. My shafts are over-spined for my lighter bows.
you can try a string with more strands or thicker center serving like.026 that will weaken your arrows.