So I'm looking on the 3rivers dynamic spine calculator and it says I need a 75# shaft for my 160gr heads out of my 55# howatt hunter with my strike plate built out. That sounds a bit stiff doesn't it? Or do those heads make that big of a difference?

Someone will help you on here. I just went through making arrows and these guys are the best.

How accurately did you enter the information is the key? The calculator is only a data base. It provides the closest relevant information based on the data it receives.

When I enter the information it gives me a dynamic spine calculation of 66.7lbs.. That's with a dacron string, 29" arrow, and .0125" thick strike plate.

Sounds pretty well right to me.

BUT, remember that spine isn't written in stone, and ALL bows will shoot a variety of spines more accurately than most of us are capable of sorting out.

Where's Aromkr? On a wood shaft spine goes up pretty drastically with any point over 125.

Bowmania

How far "out" is your strike plate from center? Variables are rampant in our sport, and especially in arrow tuning. Add to that the complication of human individual form, and you will see it's not an easy answer. Built-out has a lot of meanings, and why is it built-out? The Howatt Hunter is not cut far past center, so your arrow diameter will push it out of center anyway. Just curious here.

Boy oh boy, what happened to the good old days, when the Easton aluminum spine chart was the best we could hope for. LOL. And yes I agree with the above statements.

I just said it was built out to get the bows static spine to drop. Or else it says my 55# bow has a static of high 70s.

So what are you trying to accomplish? If you don't have a strike plate the bow is closer to center. So, the dynamic spine WILL increase. When you move the arrow further from center, the dynamic spine decreases. It's supposed to do that.

You can use centershot, and string material to manipulate spine nearly any way you want to with ANY bow.

Use as a guild then bare shaft tune . I use Stews to compare different arrow setups to known tuned arrow bow combos and a starting point with new to me bows. then I bare shaft to tune sometimes making strike plate adjustments (thicker/ thinner/ softer/harder Velcro vs leather) b55 vs fast flight and even placement of string silencers. with that said stews and 3rivers are always to stiff for my setups. https://vimeo.com/70422708

You know with all the talk and i mean a lot of it about arrow sizes spine etc . i think back to when i started i went to georges stouts shop when i bought my first bow he said lets try these they flew good i was done in like ten minutes he cut one inch off the arrow that was it now that was a compound bow it was easy done . well then came my recurve same thing tried a few different arrows walla done i think that is what we needs to be done go some were that has several sizes and length and try them .

Oh yea then we decided to make and try wood arrows george ordered some cedar from kinzeys then we were using them . i cannot remember all that much discussion about spine like on here . then a friend of our started making and selling arrows in the shop there again guy s came in asked for arrows Zak made them up and that was it . i still have some he made . he was very good a cresting them etc . i made taper blocks for the drill press so he could taper a hundred in say a half hour . it was simple then george bought the schieb spine tester give it to Zak so he could check them a little more but i used a tester i made it was not all that complicated as i remember .

Tracker

There is no way anyone can help you without all of the information. You don't indicate your draw length or arrow length, the material your string is made from. You say your strike plate is built out, but built out from what?

Bob

Exactly too many unknowns

I was just wondering if gaining 20# for static spine sounded right for only 35 grains. Like how much everyone has to increase for point weight.

I use the dynamic spine calculator and it is spot on for me. You MUST input every detail they ask for, and do so accurately. That will get you very close, based on my experience. There's a form factor adjustment section on 'Stus dynamic spine calculator' that will dial you in dead nuts on it. Do all this and you will be incredibly close, and avoid years of shooting poorly matched arrows, as I did.

I make cedar arrows for a friend with a 54 pound Howatt Hunter. He has just shy of a 28" draw, about 27.75". I make his arrow 28.25" bop. With a B 50 bowstring his bow shoots 55-60, with 125 grain heads.

Different people with better or worse release change everything. No chart or calculator can be accurate for all. the string goes farther around the fingers on some than others which changes the spine needed. Other pluck the string which also changes spine needed. these guys will get you in the ballpark close enough for you to tune your arrows.

Using wood that should be close, but what is your actual draw. I would think with a 29" shaft and a 28" draw and that 160 grain head you would shoot a 71-75# shaft ecsp if you built out the strike plate a bit if not then you may be able to shoot a bit stiffer. Shawn

One handy thing about wood.... JMO, it is far and away the easiest to trim to length. So at least you can start with shafts that are CLEARLY too long and work your way in. Hard thing about them is that you don't really know exactly what they're going to weigh....

You asked about the calculator - I've been messing with it A LOT lately, and for a #55 Hunter (1990, B-50), drawn about 26.5" or a hair more +125 up front.... Man, it is Dead Nuts. My strike plate is calf hair with a paper matchstick behind it, so I'm guesstimating 1/10". Stu says I need to hit #64.1 for that; today I was shooting some 28.5" 2016s... and the calculator says those come out #63.9. Fletched. Bare-shaft, they're #2 weak.

I was a little shocked when a bare 2018 hit right in there with them, but it measured out at 30" even, which (surprisingly) is only #61.2...

You nailed it scooby! I found a couple woodies that spined 74/75 and cut em to 28.5 BOP, draw is 27.5/28 abouts, shafts flew pretty darn perfect. Had to build out the shelf about 3/16" though. Just sounds funny, been shooting Selfbow's with 40# arrows on a 55# bow haha

Got one of these and it works for me.

Tracker well sounds like you have answered your own question shoot what fly the best .

Just got the same flyguy! I plane a couple dozen arrows a year and got tired of my homemade rig.

wow, I have never messed with one of the calculators before but I just plugged in my bow/arrow combo and it was freakishly close. cool stuff

Yes it is. Look, it may or may not be spot on for guys that have sufficient experience, it has been for me. I had no experience and no clue what to use so I went with the advice from a guy that shot cbows at a Mom and Pop store. As it turned out I was over spined, but didn't know it. I shot that arrow for ten years until I found this site.

I always suggest using the calculator for guys that really don't know arrow spine for their bow. Guys that know whats what from experience don't need it. There are so few trad shops nowadays that the usual place you get trad tackle advice is from cbow dudes at big box stores, and we all know that is a coin toss.

Anothe thing about the calculator is you can learn the subtle variation of what effects what by playing with the inputs. That is fast and way cheaper than constantly ordering parts from your supplier.

Funny thing... Now that I really do know what DOES work, I plugged in the numbers for the last couple dozen aluminums I bought; #64 is Correct; last two combos came out at #80-some and #94.

It works for my light arrows pretty good.

It is usually spot on for me, and when not it's still close enough to get me into the correct spine shaft.

You just have to be certain, that the numbers you are entering are correct. Then it will at the very least get you close.

The only problem with the calculator is - it cannot read, and compensate for variances in shooter form across the board.

Everything about the calculator assumes & works from a center line, and a perfect form. Something as simple as a rotated grip can change your personal results from that of the calculator, but with the personal form factor (included) you can adjust it, and save the results for next time.

Rick

So here is sort of a follow-up question on the OP....

And you probably have to own a good Chrono to answer it, but...

Given that the spine calculations seem pretty accurate, has it been your experience that the FPS figures are pretty close to ball-park? They look really optimistic to me, like maybe a good 10% higher than I'm really prepared to believe...

Thoughts?

Anyone?

Buehler?

Longbow 57#@27 TR 229.7 Chrono 173 Longbow 53#@27 TR 219.7 Chrono 162 Recurve 55@28 shot @27 TR 229.6 Chrono 182 Caldwell Ballistic Precision Chrono. My arrows average 8gpp for each bow 5 shot average +/-

Longbow 57#@27 TR 229.7 Chrono 173 Longbow 53#@27 TR 219.7 Chrono 162 Recurve 55@28 shot @27 TR 229.6 Chrono 182 Caldwell Ballistic Precision Chrono. My arrows average 8gpp for each bow 5 shot average +/-

Many times the FPS are a bit high. I think that it may bay be closer if one can honestly say that they can put in a 10 or better on the personal oomph scale. My wife's Lost Creek was exactly on compared to what the Stew calculator said. A couple of local guys had Bears and they were much slower than what the Stew calc said. I notice that are no Hills on either the the Stew chart or 3 Rivers. Find it interesting when Hill shooters get together around a chrono, the differences are remarkable from shooter to shooter with similar draws shooting the same bow.

I've got a chrono. I'll figure it out once I get my new string twisted up. Fun to figure out as I haven't tried it before with my bow. Mostly air rifles

The speed calculation is seldom spot on for me. I will get around a 5fps +\- variance, but usually it shows me slower than the chronograph does.

Rick

With the area Hill shooters, it seemed that some were brave shooting through the gates and others were timid. The bow cast does not begin until the bow string leaves the finger tips. if one has a very hard release when tuning arrows or testing for speed and a softer release when shooting at a 3d target or live game, the difference can really affect arrow flight, especially with carbon arrows out of none center shot bows. i have seen 20 fps variations. For myself I had a 10 fps variation, that told me that I had some release issues to think about. It is possible to really crank out the energy on a release, but I wanted to simply have consistently strong release that was natural and not over done. The chrono testing really helped me after I got comfortable with it. I found that shooting at a deer target some 25 yards away, while at the same time shooting through the chrono, was a great revealer to what I needed to do.

So, Jerry - you're saying the calculator was predicting 230 fps????

Yes. and I checked all my input and that is what numbers it kept showing. When I used my chrono I would get with in a couple fps each shot and a few duplicates. The spine chart is close for me but the fps isn't even close.

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