Stu's calc doesn't match my result

[FrankM]

Just as a test, I put some 250 grain weights on my arrows. They shot really nice. Seems better than 145, 175, and 200 weights. Stu's says my dynamic spine is 44.2. The bow dynamic spine is 66.2. Does this ever happen?

[sawtoothscream]

Same here. According to the calc my arrow right now is pretty under spined.  My bareshaft tuning and everything else says there about perfect.  Although I could just be inputting wrong info.  I made arrows that said they were right and were to stiff for my bow and I had to add more wiegbt up front to get them to hit good.

[Swamp Yankee]

Make sure the center cut and plate thickness numbers are correct for your bow; it makes a big difference.

[FrankM]

I was real careful about the adjustable rest. Right now it's set to -1/16. I do have a NAP flipper rest that is a bit forgiving of spine.

[Javi]

Originally posted by FrankM:
I was real careful about the adjustable rest. Right now it's set to -1/16. I do have a NAP flipper rest that is a bit forgiving of spine.

How far past center is your riser cut? A flipper is a thick rest.

[LCH]

Mine does the same thing I thought it has something to do with my releaseLCH

[Javi]

If the riser is cut to center and you are using a strike plate or stick on rest you have to measure the thickness and show it as a positive..  My Sarrels is cut to center and I'm using a velcro strike plate that measures a 1/16" thick... I enter + 1/16" makes a huge difference in spine if you go - 1/16 instead..

[JCJ]

Me too!

According to my bow inputs for a Holm Made Osprey it indicates I should be shooting and arrow with a dynamic spine of 53.1 however an arrow with a dynamic spine of 35.4 bare shafts and paper tunes when fletched perfectly. Go figure.

[Bow Bum]

Stu's calc only started matching my real world resluts when I started to be VERY METICULOUS of the measurments of insert, and nock weights. ACTUAL draw length. And ACTUAL center cut and strike plate thickness.

I'm using bold, becasue I know I made these mistakes thinking that it would be close enough like when shooting a wheel bow.

Stickbows are more fun, but when it comes to tuning, the devil really is in the details.

Best of luck,

Brian

[FrankM]

The bow is a Jaguar Recurve. I measured the distance with the two string method and a ruler. Did it multiple times to make sure I didn't put any pressure on the strings.

I was shooting 145 gr. points for practice and everything seemed fine. Arrows flew pretty straight and hit what I was looking at at 17 yards. So, I decided to try some heavier points. I used 175, 200, 250. The heavier they got, the faster my arrows settled down, and still hit what I was aiming at. Does that just mean the heavier arrows are "compensating for my technique"?  Or am I just discovering the proper arrow setup I should be using?

[metsastaja]

YES THIS DOES HAPPEN.

There are many reports of guys taking a tuned arrow and while playing around add 100+g to the front end and the arrow flys great.

[awbowman]

Mine was right on the money with my Black Widow.

[SlowBowke]

Ok, Im old..stuck in my ways.....etc etc.

Stu is a GREAT guy!! The program has been an awesome thing for a lot of guys.

That said?  For me, the same ol, same ol....."shoot em and adjust length or head weight" has just worked too many decades to want for more.

When I have to break out a calculator for trad gear......FOR ME.......a red flag starts waving in my head.

One of the things I LOVE(a great many, I might add) is the SIMPLICITY of traditional gear.

Personally, I find it a negative end result to get away from that.

I tried some suggestions Stu gave me and some info I gave HIM had to be wrong, is all. End result was "less" than what I had.

NO OFFENSE, Stu, our friend! I'm SURE it's more me understanding than his error but I sat and realized one day......

"it aint broke.......no fixing needed".

FYI, though, Im not anal about everything being exactly alike for my hunting needs, NOR "perfect". May differ for others. Nothing at all wrong with that.

God Bless

[snag]

I have tuned lots of arrows (wood, aluminum, and carbon) and used Stu's calculator to get me in the ball park. Everytime, IF I put the right info. in, it has worked great! Can't stress this enough..."junk in, junk out" sort of thing. I like to bareshaft tune my arrows so it is very revealing if I have done something wrong. By starting with a slightly longer shaft than what Stu recommends and then cutting it down it has saved me lots of time and heartache. THANKS STU!              

[kat]

Nothing is fool proof. I also have a wide discrepancy with Stu's calculator.  However, there are a lot more positive results than negative.

[Flying Dutchman]

I calculated 5 different bows with Stu and checked the outcome with bareshafting. Stu was every time dead on.

[Buckwheaties]

I love to mess with Stu's calculator.. Until I got ALL of the input #'s correct, I played hell with it, BUT after reading and studying his directions on the updated version, Valla!! it's right on..
the advice on junk in-junk out is so correct.. I had previously just eyeballed my center shot (ok, that's about a 16th) type thing. Also the 100 gr brass insert was just put into the insert box (how much difference could that make) type thing? Once I actually measured my true draw length numerous times with a close-pin (it changed the #'s) and measured the actual draw weight of the bow,(it changed too) and the actual center cut of the bow by laying it on a table method as explained in the new instructions,(it changed too) and finally doing the brass insert properly. GUESS WHAT?? got the best flying arrows I've ever had... Thanks Stu.... the new instructions really helped to bring it all together for me..

[ROB TAYLOR]

Myself and a few friends that I KNOW know how to properly tune have vetted Stu's calculator extensively.  

So....here's the raw truth.  There are only two ways that you will NOT get anything beyond what I would call a 90% tune result from the calculator.

1.  Garbage in-garbage out......you are not entering the info accurately....period.

2.  You have a form/release that needs compensating for in the calc and you have not figured out what that is (under the "form factor" setting).  Mine, for example, is -1.

The reality is that there are those among us unwilling to spend the time to really explore the physics our pursuit reqires....even from the layman's point of view.  I cringe when I hear people tuning a bow to "hit where I look", etc., regardless of actual arrow flight.  The goal is to get the bow/arrow system tuned for absolute harmony/synergy and THEN re-program the operating mechanism's computer (your brain) through repetition to be able to aim (yes, we all do aim) the system to impact the target as desired.

The nuts and bolts of bow tuning and arrow flight can not be treated with the same subjective romanticism that many of us assign the overall "trad" lifestyle if one expects consistent, truly tuned arrow flight.

As for the common mantra of "I shoot trad gear because of it's simplicity"....I can only say that we must have vastly different definitions of "simple".  If less parts=simple, then maybe.  But I find it damaging to one's argument who says that they use stick and string to hunt because it's so much more challenging in one breath, then say that the tuning of said equipment is "simple" and easily accomplished using some sort of combination of "feel" and anecdotal black magic in the next breath.  I, for example, can tune a compound in an hour or less to superb hunting accuracy and arrow flight and rarely have to adjust a thing for a year or more.  My recurve, however, is a completely different story.  It's tuning has so many more variables that I can not see how it could be "simpler".

All of this is not to say in any way that there are not those out there that will be good shots or successful hunters doing it some other way, but I believe utilizing Stu's calc and other methods that have peeled the layers back to raw science will get most shooters closer to their full potential quicker.  But hey, some just enjoy the journey....and that's OK, too.

[boznarras]

I had a similar experience.
I was using GT5575s with 100g inserts and 175g points and getting good flight. I came at this by bareshafting and using test points, etc. When I Stu'd this set up it said I was way underspined, about 30 lbs low.
So I put together some arrows that conformed to the calculator, GT7595s +100g insert+125g points, and thankfully,they shoot good too. I did have to raise the nock point because they were shooting higher.
Can't argue with results. Maybe the program gives a good suggestion, but not the only answer. It is certainly a fast and cheap way to get a starting point.

[FrankM]

This is how it began. A few days ago, I found that my inputs were wrong. My arrow rest was measured incorrectly. When I fixed that, my bow and arrows were 66.2 and 66.4 dynamic spine. The arrows flew great!  Then just for funzies, I put more grains on the point, and they still flew great, and seemed to be more "laser like" with each increment in point weight. That was what caused me to make this post. I can shoot the 145 gr. points and they'd be fine. But I'm kinda seeing no reason not to up the point weight.