Have you ever been in a situation where the bowyer tells you to use +15# with the bow you just bought. And you want to use carbons but haven't a clue how to tell what +15 means.
Here's a dynamic spine calculator that lets you set up your arrow with the FOC you want and calculate that spine the bowyer was talking about.
I was turned on too this today and spent some time working with it and my bows. Our Orion curve is a +15 bow. Meaning that you will find that the dynamic spine is 15#s heavier then the weight onthe side of the bow.
I spent the afternoon working on bareshafting my 45 @ 28" Orion recurve. I decided to try a string with less mass. And notice that my arrows that were tuned were now flying a little weak.
So out came the bareshaft. Ended up having to drop my point weight from 200 to 160. This gave me a dynamic spined arrow of 60#. After we were done I was working with the dynamic spine calculator and ran some 2016 shafts. Ended up with a 29" arrow with 125 gr point and 60# dynamic spine. Took a 2016 bare shaft out and shot the 3 D course at the house. I was holding kill zones out to 25 yds.
So now I have two arrows that shoot the same out of the same bow and the means to design many more combos.
Here's the download link to the calculator. It's pretty easy too use and seems to be dang accurate.
http://briefcase.yahoo.com/bc/hkg3sg1@sbcglobal.net/vwp2?.tok=bceRJecBj15UbCko&.dir=/Public&.dnm=Dynamic+Spine+Calculator+Rev1.xls&.src=bc
Mike
This is great!
I agree with Focusource. Sure is easier than hunting through a chart and guessing about various factors.
From a few test calculations I've done the result seem to be quite good.
awesome but it showed me that i cut my two dozen arrows a half inch to short.if i had'nt they would of have been within 0.2 bummer
Wingnut,
can you tell who the author of the calculator is and or its source?
I just played a little with it, using numbers for alums I have every parts specs in mind - and it was quite a bit off as far as total mass goes. It was more accurate though, when I added the weight of the insert to the weight of the actual point. This is not mentioned per se in the manual but is maybe intended this way?!
Yes you have to add in insert weight and nock adapters ect if you use them.It is very close if you enter everything right.I havw tried it with several combos of bows and arrows I shoot and it works for all of them.A great tool for guys that want to play with the heavy points,inserts and footing on there arrows.Nothing can be perfect for everyone because we all have that unknow factor that we can't add it.Us and the way we shoot. :)
Yep I figured the adapters and inserts in because they have such a large variance.
The other thing I recomend is get the arrow you shoot the best and that bareshafts great. Use it as your dynamic spine standard for that bow. Now play away.
Like I said, my 45 @ 28 bow likes 60# dynamic spine.
Mike
QuoteOriginally posted by Falk:
Wingnut,
can you tell who the author of the calculator is and or its source?
I just played a little with it, using numbers for alums I have every parts specs in mind - and it was quite a bit off as far as total mass goes. It was more accurate though, when I added the weight of the insert to the weight of the actual point. This is not mentioned per se in the manual but is maybe intended this way?!
I think Stu Miller on the wall.
I'm not sure on the author. Rusty sent me the link yesterday morning.
Mike
I can't open it
You have to download it and then open it in Excell.
Yep Stu is the author from what I've been told. He has it out for free download.
Mike
Is the center cut + xx distance past center or less than center? Does that make any sense to anybody?
QuoteOriginally posted by Andy Diggs:
Is the center cut + xx distance past center or less than center? Does that make any sense to anybody?
The number is the distance out from center. If it is cut past center then you need to enter - . If you get access and scroll down you can read all the variables and instructions for use. I have been playing with it as I tune some arrows to my new bow. I am working my way down to the calculator numbers to see how it works out.
Thanks. I should have read the instructions.
Thanks Mike :thumbsup:
This is a cool tool. question--how do I find the amo static spine of the arrow dynamics?? does anyone know ?? thanks
good stuff!
What number should I use for the AMO static spine on a CX Heritage 250. The spine is listed at .373 on carbon express' website. I've tried everything I can think of and can't get results that make sense.
I believe the static spine for the CX 250 is 84#.
You can divide 31.5 by .373 to get the spine weight. You can do this with any deflection. Butchie is right on of course!
i think the interactive chart is at least a decent starting point, but no chart is gonna even work up ballpark numbers for everyone. i'm one of those anomaly "everyone" folks.
beman 500 shaft, 29.25", 350grs up front, 4" 4-fletch lo-profile feathers, 585grs all up weight, 55.5# holding weight @ 29". bareshaft or feathered they fly just great at 5 to 35 yards. plugging in the numbers to the chart yields the following ...
(http://img.photobucket.com/albums/v82/rfdee/archery/carbon_spine.jpg)
Rob,
You might need to actually use the Other in the arrow shaft. I found the carbon XXX to be rather bland.
Put you weight and spine # in the other and I bet it's closer.
Mike
these are the numbers i get when using "other" - what am i entering incorrectly?
(http://img.photobucket.com/albums/v82/rfdee/archery/carbon_spine2.jpg)
Rob you are outside the norm.Most people could not shoot your setup at all.The numbers on the chart are probably pretty close but you still have to add in the human factor as you show.Sometimes things just work different. :)
BTW..It would be almost dangerous for me to shoot the setup that works for you.That unknown human factor again. ;)
QuoteOriginally posted by James Wrenn:
Rob you are outside the norm.Most people could not shoot your setup at all.The numbers on the chart are probably pretty close but you still have to add in the human factor as you show.Sometimes things just work different. :)
BTW..It would be almost dangerous for me to shoot the setup that works for you.That unknown human factor again. ;)
yeah, i'm weird - nothing i already don't know! :D
ooo, lemme add to this that in hunt camp other folks have shot my arras outta their bows (similar holding weights) and they also experienced those arras flying just great for them. maybe i oughta patent whatever i'm doing, LOL!
:D
The spine on your 500s is about 65lbs amo.It llooks like you have less entered in your second screen shot.
ok, i was using deflection, so here's what it takes to match my bow - 100 lbs! - yikes!
(http://img.photobucket.com/albums/v82/rfdee/archery/carbon_spine3.jpg)
Snag thanks for the formula makes the calculator work for me. I did a lot of bare shafting a week or so ago and came up using 250' cut at 30" 100g insert and 125 points. Using that information the calculator did this.
(http://i261.photobucket.com/albums/ii45/heilakka/arrows/ce%20250/spine.jpg)
Rob, I adjusted your point weight for those shafts down to 160gr. and got 57 and 56.8 It looks like you would need much heavier spined shafts to be able to bump up the tip weight to 350gr. You could put in a spine weight for Beman 400 or 340 and see how that works for your setup.
Les, looks like you are right on! Isn't it a beautiful thing?!! :clapper:
QuoteOriginally posted by snag:
Rob, I adjusted your point weight for those shafts down to 160gr. and got 57 and 56.8 It looks like you would need much heavier spined shafts to be able to bump up the tip weight to 350gr. You could put in a spine weight for Beman 400 or 340 and see how that works for your setup. ...
been there, done that - what would appear to be a correct beman shaft for my holding weight and arra length (400 and/or 340) are just way too stiff and the resulting bare shafts fly at least a bit cork-screwy and land crooked. adding feather steerage helps heaps. i can consistently bare shaft 29" 500's from all 3 longbows, 46-55#, with dart-like flight. heck, if it ain't broke ... :D
spent way too much time and money messing with carbons, and the only shafts/arras that work best for me are weak spined carbons. an exception are the tapered ad's that fly well if over 600grs.
a few things have been of pivotal help with carbon shaft selection - reading about howard hill's arrow selection, shooting style, and his ability to reasonably accurately shoot anyone's arrows ... and jim ploen's iam articles on aiming. this lead me to some aiming and form experimenting and though i can now shoot most any arra, it's the weak ones with enormous front end weight that work consistently best for me. besides, beman 500's are cheap. :D
Well if you went with MFX 340s with 11gpi and 340gr tips you'd be at 56.7 and 56.8. I am amazed that you can successfully bareshaft 3 longbows from 46#-55# with the same setup...but who am I to say different.
Snag: yes it worked well for me. :bigsmyl:
I am going to try and build a couple of carbons
for 2 bows my brother is bringing down in a couple of weeks. Will be interesting to see how close I am.
QuoteOriginally posted by snag:
Well if you went with MFX 340s with 11gpi and 340gr tips you'd be at 56.7 and 56.8. I am amazed that you can successfully bareshaft 3 longbows from 46#-55# with the same setup...but who am I to say different.
firstly and foremost, there are SO MANY factors involved in good arrow flight, including both the gear and the archer.
the feller that designed this dynamic spine calculator, stu miller, did a really darn good job of averaging lots and lots of data, but to take any of the results as gospel is a stretch for anyone - you, me, or even ol' howard.
there are any number of factors left out of the equation - physical stuff that's difficult if not impossible to factor in because it's all too variable. shaft material is one huge factor - static spine data for wood, alum and carbon can be intrinsically different and near impossible to compare within one set algorithm. how 'bout degree of centershot, the length of the front end package (as it affects the arrow's pressure point), or how foc and feather types affect the paradox? now add in the human factor - shooting form and shooting process.
none of this is to dis stu's neat interactive spine chart, but to advise stepping outside of the box a bit when matching arrows to both yer bow and yerself. can't hurt.
Rob I'm with you, I shoot 28" MFX500 out of 55-60 bows with 300gr up front and they bareshaft pefectly.
Rob,
You gotta remember the folks that are in need of this info are the ones coming on everyday asking "what arrow can I shoot off of this bow?"
This gives them a place to start other then someones elses guess.
Heck I saw a person the other day recommend a 2016 to a guy shooting a 40# Bear because he thought he should have more weight. At least with the calculator you can get in the ball park before you go buy the shafts.
And how in the heck can those arrows be flying that well with that light of a shaft? LOL
BTW it does cover degree of centershot quite nicely.
Mike
phil_ - this isn't an "us and them" thing, it just is what it is, no more no less. whatever works best is all that matters and we're all "experiments of one".
mike - i'm totally with ya mike ... as i stated, the chart is a real good thing, particular for those new to trad ... for some of the rest of us ol' curmudgeons, we just may have other ways of skinning da cat. :cool:
I dont know what im doing wrong but when i put in my setup info i get a .3 as the first # and a 76 as the second. What am i doing wrong?
I use a Carbon Experss Maxima 250 with a deflection of .407 so i devied that by .825 and get .493, i plug that in and get that wierd first #.
wtpops - the static spine deflection is in weight (pounds) not length (inches). i dunno what the cem 250's equate to in pounds, someone will chime in for sure .........
Dohh, i got it helps when you read the hole thread, found my answer on page 2. Thanks
That CE Maxima has an equivalent spine of 77.4
WT don't feel bad I did the same thing before I found Snags post. I was clueless.
Make sure to use the exact shelf strike plate location of your bow when using this formula. It makes a big difference. I say this because I initially just plugged in +1/8", but when I actually measured my HH Wesley, it measured +1/4" from string centerline to strike plate. Going up to +1/4" gave me 8# less spine than when I used the +1/8" figure. :eek:
On the arrow end of things, I like the outcome and plan to test it out and see if it's accurate. The best match I got for my 48#@26" HH is a GT 3555, 29" with 325 up front (100gr. brass insert, 100gr. broadhead adaptor, and 125 gr. glue-on broadhead). This would give me 580gr. total weight, 12 gpp, and a 27%( :eek: ) foc. :cool:
I think if you have a well tuned arrow to your bow already that is different from the bow side this calculator is still of value, because you can plug in a different arrow setup and match the dynamic spine of your good arrow on the arrow side of the chart, and ignore the bow side.
You can also run the test for your other bow setups, and if the error of bow and arrow side calculations are about the same for each of your bows as say 10.5# difference for you then just use that as a correction factor when trying to match a new arrow to a new bow to give you a starting point. Remember to start with the arrow longer than needed when you start tuning it anyway.
Does anyone have the formula to convert deflection measurements to Spine #s?
It sure would be handy since all the companys are giving deflection now.
Mike
It was posted earlier in this thread as 31.5 divided by the deflection as .xxx" or
31.5/.xxx" = # static spine
But when i checked it against my wood arrows the formula seems to come out as 27.5/.xxx" so I don't know if it is right.
I took store bought shafts marked 55-60# and used 57.5# as the spine, and 60-65# as 62.5# and multipled by the deflection as measured on my homemade spine tester to get this formula.
The 31.5 may work for carbon arrows I just don't know for sure. I'll test some GT's and see.
What I still don't understand, and maybe never will, is how can an arrow that with a 65# spine NOT fly weak with 350gr tips. I have tried to go up in spine weight with CE Heritage shafts that have 84# spine and if I go above 225gr. they bareshaft weak. At 225gr they fly perfect. So you are taking less spine and adding 125grs more and they fly like darts...?
QuoteOriginally posted by snag:
What I still don't understand, and maybe never will, is how can an arrow that with a 65# spine NOT fly weak with 350gr tips. I have tried to go up in spine weight with CE Heritage shafts that have 84# spine and if I go above 225gr. they bareshaft weak. At 225gr they fly perfect. So you are taking less spine and adding 125grs more and they fly like darts...?
ya think it might have something to do with the archer? :saywhat:
Heres a little trick I do to tell if arrow is too weak or stiff.. Get out in a field ( i prefer hilly)on a calm day. pick a spot on opposite hill at least 150yards away. Place your point of aim on the spot. Shoot 3 arrows...If arrows hit to the right of spot.aroows too stiff........hit to left....too weak.........start shooting different arrows of different spines.....till your arrow shoots straight.....this is not rocket science guys. If your arrow can't reach the opposite hill because your bow is too light....drop your bow and do 30 pushups
I've been piddling with this calculator to check my current arrows...have been teaching myself with my old compound arrows, 31.75" 2514's with 125 grain tips. I knew they were overspined, but until I knew the trad thing was going to stick, didn't want to order new.
With that setup, the arrows are 82.4 and the bow is 53.3, which makes me feel better about my group size.
A few days ago I ordered some CX Heritage 250's, planning on using 125 tip with 100 insert at 31.25" and crest wraps. That should give me 53.5 to 53.3. Can't wait to see how a more forgiving arrow that's pretty closely tuned to my bow will affect my shooting.
I believe this is the purpose of the calculator...to get a good starting point for us less experienced guys.
Ok I checked my Gold tip 5575 and using 75# got 28.5 the deflection measured .340" for me.
Gold tip 7595 using 95# I got 26.6 as the number to divide by the .xxx" of deflection which measured .280" for me.
The Gold tip numbers bracket my wood arrow numbers of 27.5 if I use the high end of the Gold tip spine range as the pounds of static spine. I only used one arrow each for the carbon test.
My spine tester is homemade and may have a degree of error associated with reading it.
imo, all shaft spine testing should be in deflection inches, as in days of yore - shaft on 26" centers, 2# hanging weight midway (13"), deflection measured in decimal inches. this makes for a very common playing field in shaft comparison, no matter what material is used.
years ago i built a dial caliper spine meter that just measures deflection - i realized early on that converting dial deflection into actual poundage was a wasted effort, and all that mattered were that the arrows (woodies, at the time) each were close in stiffness. a spine meter is good for woodies, for sure.
in any event, there will always be an interpretation as to what shaft "spine" (stiffness) will work best for an arrow that's built a certain way, with a particularly foc and type of steerage, out of a particular bow that's set up a particular way with regards to centershot and what type of string material and nock point heigth, and yadda yadda yadda. what a pain. and as stated much in this thread, stu's interactive chart can help those that do need help.
Rob, I also feel the deflection is a more useful measure than the poundage range so often used. I have long been frustrated by poundage charts for arrow spine.
I see Stu's Calculator as an improvement over the charts, but would like it in decimal inches of deflection much better, but then most archers don't have spine metters in my experience.
Oh and sorry about the link to Stu's diagram for center shot measurement on the other site. I didn't know.
QuoteOriginally posted by Douglas DuRant:
Rob, I also feel the deflection is a more useful measure than the poundage range so often used. I have long been frustrated by poundage charts for arrow spine.
it's the only measurement that's fact over interpretation.
I see Stu's Calculator as an improvement over the charts, but would like it in decimal inches of deflection much better, but then most archers don't have spine metters in my experience.
i agree about using decimal deflection. ain't that difficult to build a device to measure shaft deflection - a board, coupla dowels, a ruler, 2# fishing sinker lead, stiff wire, etc.
....
OK, I'm a dummy here. How do I figure the static spine for my arrows. I shoot 29"(bop)AD's Trad Lites. They are total 680grains, with 350 of that up front. I shoot approximately 11.1 gpi. Whats my static spine?
Mike
Rob, I agree about checking spine on a spine testor whether it be wood or carbon or whatever.
I don't think it "might be the archer" when referring to the bareshafting of 300+ tip weight on carbons 65# spine weight if cut at or over 29" long. I shoot a lot. If I am shooting well I will bareshaft so that I am sure my results are good. With 225gr tips the 84# shafts tuned perfect. When I go up above that they consistantly show weak. This is after many arrows.
Call me what ever you want but I think I will just come on here and ask you all, what will fly great out of my new bow :D
QuoteOriginally posted by kojac:
Call me what ever you want but I think I will just come on here and ask you all, what will fly great out of my new bow :D
ummm. a good arra? :D
QuoteOriginally posted by snag:
Rob, I agree about checking spine on a spine testor whether it be wood or carbon or whatever.
I don't think it "might be the archer" when referring to the bareshafting of 300+ tip weight on carbons 65# spine weight if cut at or over 29" long. I shoot a lot. If I am shooting well I will bareshaft so that I am sure my results are good. With 225gr tips the 84# shafts tuned perfect. When I go up above that they consistantly show weak. This is after many arrows.
i hear ya, david - if i was you i'd wonder how can that be, too ... but it is. guess i need to make up vid for you skeptics :D
This theme will be terminated then when will not be archers... Except for depth cut (on which paste all in succession) release is very important. The thick and rigid glove (and curve hands) at once will demand a rigid shaft. But a starting point - magnificent. Thank the author :thumbsup: .
I hope I don't sound like I don't believe your results Rob. I am just confused as to how this can be when I get such different results. Yep, I'm confused...not the first time! :confused: But as long as you are getting good arra flight and I am happy with mine that's all that counts.
QuoteOriginally posted by snag:
I hope I don't sound like I don't believe your results Rob. I am just confused as to how this can be when I get such different results. Yep, I'm confused...not the first time! :confused: But as long as you are getting good arra flight and I am happy with mine that's all that counts.
as i've said b4, there's more to good arra flight than physically measured criteria. it took me a long time and too much wasted money to for me to be a believer, but actions speak louder than words.
fwiw, i can't get beman 340 or 400 spine carbons
(29", 350 up front) to bareshaft straight (right tailing stiff) without resorting to my bag of form "tricks". just moving the 350gr insert/adapter/point over to the 500's makes them puppies fly on rails for me.
in my former life, as a looong time "serious" target archer, shaft selection was incredibly far more critical (fingers recurve, non-olympic freestyle) as distances ranged from 10 to 100 yards and the upright stance form, with under the chin anchor, dictated different bow and arra tweaks to get the missiles to group very well at all marks. for the most part, those arras were bareshafts, touting only 1.7" spin wings and a low 9-13% foc (we all thought that was heavy foc, when compared to the standard 7% foc). if i only knew then what i know now ....
This tool has been helpful to me. Im just getting back into trad. after many years w/ compounds. Just from tinkering w/ numbers, it sounds like a person could shoot GT 3555 AND 5575 out of the same bow just by adjusting point weights. For me, it sounds like a GT 5575 would be better because I want the extra weight.
sorry for the double. i put a 300 carbon for a ad heavy and i ended up at 50.1 shaft and 50.1 with a super shrew. i guessed they were about a quarter to three eighths off center.
Sorry if I sound dumb, but what is ads. Are you talking about arrow dynamic spine?
QuoteOriginally posted by Mark-R:
Sorry if I sound dumb, but what is ads. Are you talking about arrow dynamic spine?
i believe the reference to "ads" is for arrow dynamic tapered carbon shafts.
Sorry, I was refering to my Arrow Dynamic shafts. Any help on these?
No Help on Arrow Dynamics yet. Ted is sending me an assorted cross section of the shafts. I'm going to do the spine testing and should have some good data in about a week.
Mike
Thanks Mike. If ya would, could ya PM me the results?
I'll publish them here and pass them on to Ted Fry at Raptor.
Mike
any one using the offset caused by the plate on shelf. ie if your bow is center cut and you have a 1/16" plate do you put that in the calculator as +1/16. asking cause those numbers make big difference.
Les,
I used the actual cut of the riser and mine and now 3 others have tuned right up.
Mike
I am adding in the plate on mine. two bow have shown to be right on. and I am shooting better then ever. I have left a couple posts where Stu hangs out. Hoping to get a response from the author. Building out center cut with plate is one of the ways of tuning.
? Do you add the weight of your nock and wrap as nock end weight? Then use insert and point as point weight?
Just wanted to ad my thoughts about how the chart worked for me. I am in the same boat as Rob with shooting full length beman 340's with 385 grains up front. The chart says that I need to drop point weight down to around 200 to get in the ball park. My draw is a true 31 inches and pulling 66 pounds at that length. It works well with feathers and bare shaft.
How are you guys measuring the side plate? Site down the string / some kind of mini plumb bob? Measure the riser itself. This number seems to make such a difference that I wanted some good ideas for measuring it accurately.
thanks
From what I see, this calculator disagrees with the easton spine selector chart by huge amounts.
For instance, I'm trying to set up a 52" 50@28 Red Wing Hunter for turkey. I draw 28". The right side number is 48.0. I have been trying 2013 shafts cut to 28.5" with feathers. The calculator says I need to shoot 175 grain points to get 47.5 on the left side. I really hadn't planned on using 175 gr points for turkey.
Am I doing something wrong??
However the Easton chart says that with only a 75 grain point I need to be using 2018 shafts (the chart max's at 150 gr).
There's a hoop of difference between the weight and spine of a 2013 and a 2018.
Normally, I don't bare shaft my bows. I try 2 or 3 different spines, find the on that flies best and tweak it-point weight, fletching size, brace height, etc. When I get consistent, accurate arrow flight, I'm ready to go hunting.
I believe you will find the dynamic spine calc to be closer to reality then easton.
Theres is mostly for compound bows even though they have a recurve section.
Mike
i've found, for the very most part, that the easton shaft charts, as they apply to trad bows for alum, carb/alum, and carbon, aren't even close in too many instances, and for a number of archers (not just me).
With Stu's calculator you have more input for adjustments than Easton's.It can get closer.Easton't assumes ff strings and bows cut past center.It also assumes if you put in an arrow 30" long you are pulling 29" on draw ect.That can't be changed so it will not be as close if you are shooting outside the norm.With the other being able to set draw length and use an arrow of any length pluse the change in centershot will fine tune things much more.
Most of my bows are cut past center.I use skinny strings and with the longbow selected on Easton's arrow selector I have no problem shooting arrows they recomend.If I choose recurve they will give me a stiffer arrow than I need.Both Stu's and Easton's put me in the same range when I use the longbow seleaction.Close enough normal point weights will work. jmo
I have some 85#-90# tapered POC shafts that I pulled out and wondered if 250gr tips would work. I plugged in the numbers and found with 28.5"bop and 260gr tips (100gr.adapter w/ 160gr. field point) the numbers came up 62.3 and 62.8. So cut a couple down to 29"bop and gave them a bareshaft try...a little weak, went to 28.5" and they came in about 1"-2" weak! Perfect after fletching. Love this chart!
Okay, I measured my Wesley incorrectly. I initially had it at +1/4" offset, but I ran across an illustration of how to measure, remeasured it, and it turns out to be between +1/8 and +3/16, right around +5/32. SInce this isn't an option on the pulldown for offset, should I use +1/8" or +3/16" for my offset number?
Hmmm...maybe I should just figure the numbers for both +1/8 and +3/16 offset and split the difference between the final numbers?
On another note, speaking of discrepancies between the calculator and actual experience, allow me to add my own. According to the calc, my Wesley needs about a 46# spine (measured between +1/8 and +3/16 offset). I just finished putting together a dozen lam birch arrows that I've had stashed for a while, because I thought they might be too stiff. They're 5/16" diameter, 50-55#. I put my usual 3 5" RW shield cuts @ 120 degrees and 125 gr. field points on them and started shooting at 20 yds. I started full length and they were noticeably weak. When I got down to 28" on the nose (nock saddle to bop) they flew like lasers. I don't have a spine tester, so I'm trusting the vendor's numbers (Allegheny Mtn), but assuming they all truly fall into the 50-55 range, such arrows would give a spine between 55.3# and 60.8#, according to the calculator. That's 9.3 to 14.8# over the 46# number for the bow. That fits in well with what I've read so far about people using arrows 10# or so overspined for HH bows, but misses the calculator's "ideal" 2# variation between arrow and bow by a wide margin.
The only shortcoming with these arrows is that FOC is only going to be around 10%, even if I used 140 gr. HH broadheads (the heaviest 5/16" heads I know of). So...for hunting shafts, I'm thinking of some Surewood firs, with 100 gr. Woody Weights and either 150gr. Woodsman or 160 gr. Magnus I, which will give me about the same overall weight as the lam birches (about 14 gr. per lb), but an FOC of around 20%. The thing is, I figure with all that weight up front I'll likely need 65-70# spined shafts to maintain the same spine range as the birches.
Ultimately, it looks like the calculator is good for figuring basic arrow and bow spine numbers, but the suggested 2# variation between those numbers seems way low to me, at least for Hill bows. :confused:
pointystick, i think that for the most part, stu's dynamic spine chart is at least a spine base line that works very well for most folks, and way better than any static spine chart (i.e. - easton and others).
we are all "experiments of one", and there can be valid differences in what works and what doesn't. i'm one of those anomalies in that suggested spine weights prove way too heavy and weak spined shafts with heavy points works best for me.
in the long run, as with most things in life, there's no substitute for personal testing and surely ymmv! :saywhat:
Back on page 3, Wingnut asked for the formula for converting deflection to pounds. It is 26/deflection in thousandths, ie: 26/.500 = 52 lbs. This works for the 26" centers/2lb weight method.
I find this calculator very handy, but about 5 lbs light for me, shooting various wood arrows from various bows.
Many thanks to Stu Miller for making this available to us all. I'm sure he has more than a rainy afternoon invested in it.
Hey, guys. I hope I didn't come across as knocking Stu's work. I was only adding my experience to reiterate the fact that not all bows will necessarily follow the suggested formula. I plugged some of my cedars into the formula last night and they came out very close to the suggested weight (about 2-5# heavier than the calculated bow weight). Like I said, the claculator seems to do very well at figuring basic arrow and bow spines, but actual results can vary quite a bit. As Rob said, there's no substitute for personal testing. :cool:
I just got a reply from Stu regarding the center cut discussion.
-Stu Miller
PS. Regarding Les' question above, yes the strike plate should be included in the centercut input. Building this out is a great way to tune for a slightly underspined arrow and the caculator can help identify how much is needed. On additional word on centercut measurements, since this is a critical input and somewhat difficult to measure accurately, I will share a simple method I use. Please refer to the attached diagram.
(http://i261.photobucket.com/albums/ii45/heilakka/CenterCut_Measurement.jpg)
wing any word on the arow dynamics?
have tested a few of my buddies setups on here, only the ones with good flight were close or weak
high spine was the usual wobler
My main bow likes arrows 10lbs. under what this calculator suggests. Funny my other bows are real close to what it says.
Nope, still waiting to get them.
Mike
Hello All,
I appologize for any confusion caused by the use of this calculator. There seems to be a lot of questions coming my way about static spine measurement methods, centercut measurements, more carbon shaft details, etc......so....in hopes of clearing some of this up I have added the Carbon Express Hertitage shaft data to the dropdown list and also a section the will convert both ASA/AMO and ASTM deflections into AMO spine poundage. I agree with pointystick's point above that this will not work for some bows out there. It was designed around modern R/D longbows and recures and will get you very close for the majority of traditional bows out there. For the others you can tune in and when you find a good physical setup then run the numbers through the calculator and find out what the delta is between the bow and arrow numbers. For that particular bow you can then simply use this diffence which will remain constant when you try different arrow setups.
-Stu
No apology is necessary Stu. The calculator is obviously a labor of love and I, for one, appreciate your sharing all your hard work. The calculator has been extremely useful for me. Thanks again!
I will be looking forward to the updated version when it is released.
Stu,
How do I get a copy of the new REV?
Mike
Stu thanks for the continued hard work. I have tuned 2 bows in using the calculator and am in the process of doing 2 more that I am changing over from b-50 to fast flight strings and setting up for a week of hog hunting.
Where is the new revision available. I am very interested since I use CE heritage.
Here is the latest edition of the calculator
Allows custom input of deflection and conversion to spine weight. Also has some more carbons listed.
http://briefcase.yahoo.com:80/bc/hkg3sg1@sbcglobal.net/vwp2?.tok=bcCz6kcB3cFO.9ke&.dir=/Public&.dnm=Dynamic+Spine+Calculator+Rev3-20-09.xls&.src=bc
Mike
QuoteOriginally posted by wingnut:
Here's a dynamic spine calculator that lets you set up your arrow with the FOC you want and calculate that spine the bowyer was talking about.
http://briefcase.yahoo.com/bc/hkg3sg1@sbcglobal.net/vwp2?.tok=bceRJecBj15UbCko&.dir=/Public&.dnm=Dynamic+Spine+Calculator+Rev1.xls&.src=bc
Mike
Wingnut,
Thanks for the calculator and this thread, it's great! I used the calculator and had a couple of different sets of arrows made up and with out going into details, the set up that worked on the calculator fly like darts. Best results that I have had, without going through extensive trial and error. I realize that calculator is just a tool and can not be taken as absolute, but it sure got me to a great starting point. Thanks.
Stu, is the man. His calculator is the best thing since sliced bread :clapper: ...Van
Love it. What a time saver.. This version works on my Mac so now I am mobile..
I can't open it. I get an error message...
You need too download the file to your computer and use it with Excel.
Mike
Make sure you get rev 3-20-09 I think it is the only one on the link now.
Wow!!! It's a darned miracle, I don't know how to thank you. I've been scratching my head for a long time about shafts for Africa and you've just confirmed everything I needed to know.
The chef
Based on what I've seen out of my bows, the calculator seems to be spot-on for my aluminums. The CE line looks to tend towards the weak side however, given my tuning results.
Example: A CE 150 cut to 29" with 15 grains nock end weight (estimated - 9" arrow wrap) and 250 grains point weight, shows a dynamic spine of 47.8 pounds. I'm shooting a 52@28 r/d longbow, with the shelf built out to 1/16" before center, FF string, and a 28.5" draw. That setup gives a dynamic arrow spine required output value of 58.2 pounds. ...Yet the arrows I described bare shaft, and shoot fletched, perfectly out of that bow...not weak at all.
I think it's a wonderful tool for getting a good starting point on aluminums. Not too sure about the carbon values. No criticism implied. It's a heck of a lot better than anything I could put together!!!
Thanks Mike for the job done, very useful !
I have few questions :
Regarding the centershot (I've seen that I am not the only-one): on my recurve the shelf is cut 3/16 past center (information given by the bowyer), if I use a 1/16 thick rest, do I have to enter 1/4 or 1/8 in the calculator ?
In my opinion, the shaft size has to be taken into account in the calculation, for instance if my bow needs a .300 static spine shaft, the tuning will be very different if I use a 2514 or a FMJ 300 (18/64) shaft despite the static spine are the same. Assuming that the formulas were established for a 21/64 shaft (mean value) a centershot correction could be taken into account so that the dynamic spine required by the bow would increase if I use smaller diameter shafts.
Another point concerns the use of long brass inserts, I think that the flight is different if I use a 200 grains field points with standard aluminum insert and a long 100grain brass insert with a 100 grains field point due to more stiffness in the last 2 inches on front of the shaft . This effect could be taken into account by an artificial reduction of the shaft length equal to the difference between the used brass insert and a standard insert for which the calculations were established.
Just my 2 cents....
Did the calculator get moved somewhere? Both the first link and updated link are bringing up Yahoo home page and no calculator.
Me too!
ditto
TTT, I need this bad. Fellas?
All I get when I click on the link is a Yahoo news page. What am I doing wrong?
I let Stu know that the link is broken. I'm sure he will fix it.
Mike
Same here, yahoo news page!
Hello Guys,
I appologize but Yahoo has decided to discontinue their "briefcase" and this was the only place where I had access to store documents on the web. I will look for somewhere else to put the file but right now I have no options. If you need a copy, feel free to email me at:
hkg3sg1@sbcglobal.net
I will then send you the file directly. Sorry for the inconvienence, if anyone has any suggestion please feel free to pass them along.
-Stu
If it's a spreadsheet (excel) type file, you could get a gmail account and put it on their online documents.
Mike, when I click on the link, it goes to a Yahoo search page? I don't see anything about a spine calculator.
Bisch
If Stu don't mind I have it on my e-mail and can forward it to anyone who asks.
I also have a copy that Stu told me too share.
Email me at
wingnut@dryadbows.com and I'll forward you the latest edition.
Mike
updated link
http://www.heilakka.com/stumiller/