Another Stu Miller calculator question

[Prairie Drifter]

Originally posted by rod251:
.

  I entered both with a 28" draw rating, and entered my 26" actual draw length.  I entered the same strike plate thickness, and the calculator entered the same centershot on both bows.            

The calculator sets the centershot measurements but it DOES NOT show what it has entered. Set it to a measurement and then change bows, you'll see that the measurement doesn't change in the box ,but does change internally. So to answer your question, the bows have a different center cut to the risers.

[snag]

As I understand it the Stag is cut to center or "0" and the Sage is cut past center to -3/16".

No glitch in the program, just glitch in info. input....usually is "user error"...I speak from experience! haha

[Forrest Halley]

Originally posted by Swamp Yankee:
Guess I'm on of the few who have a couple of "dead to nuts" setups that Stu's calculator agrees with using 0 as the Personal Form Factor.  Seems to me if the calculator almost always tells you to use a too stiff an arrow, perhaps playing with the form factor might be a way to "calibrate" the calculater to your particular shooting style.

When I read the directions on how to use the calculator after using it a couple of times I found that the calculator is pretty spot on with the zero personal form factor. I am not getting the fps predicted and in fact fall 20 fps short. I'm extremely worried about it can't you tell? The fact that it has so many shafts in its database and in fact turned me on to a great shaft that I had not heard of before is awesome. I feel it's a valuable tool for ballparking arrows into tune. I find it's hard to beat CoolFlex insert glue teamed up with Stu Miller's for keeping arrows tuned to an archer who is getting stronger and more consistent over months of practice. They both save lots of money in wasted arrows shafts.

[rod251]

Originally posted by snag:
As I understand it the Stag is cut to center or "0" and the Sage is cut past center to -3/16".

No glitch in the program, just glitch in info. input....usually is "user error"...I speak from experience! haha

I figured something funky was going on.  I'm glad you guys figured it out for me.  In other good news, I should be able to replace the brass inserts in my current arrows with aluminum inserts and hit my spine numbers for the Sage right on the money.  Now I just gotta wait for Mr. UPS man to do his thing.  It doesn't help matters that the issue of Fish, Fur, and Game I ordered was out of stock so 3Rivers had to substitute another issue, delaying my order.  Oh well.

[Flyboy718]

Originally posted by rod251:
I know arrow calculators aren't the final word in tuning.  Nothing beats getting out in the yard and flingin' arrows at a target.  But what I'm asking is, with equal values being entered into the program, why would it say a 40 lb bow needs a stiffer arrow than a 45 lb bow?

Rodney,

I have a similar problem.  I just purchased a 50# @ 28" Quinn Stallion and I draw just shy of 30" so...about 53# at my draw.  I had some 2117 cut to 30" with 100 grain points that were tuned to the same type of bow but 45# @ 28"  I knew they would show pretty weak when I go to shoot the 50# Stallion...I decided I wanted to see how weak they would be and if I could make them work somehow with Stu's calc.  Surprising the arrow shows a much higher dynamic spine than what the bow needs...hmmm it's really strange.  So Stu's calc is saying they should be way stiff and when I go shoot they are way weak.

[Rob DiStefano]

hysterically, for the very most part, all carbon shafting has an incredibly stiff dynamic spine versus it's static spine.  many bowhunters are using 500 spine for a 29"+ arrow loaded with 350grs or more up front, out of 50-55# stick bows.

[metsastaja]

Sage and stage have different center cuts.
sage is -3/16 while the Red stag is 0.

So your tow bows are different from the start. Center cut makes a difference.

If using new DO NOT PUT number in center cut. It is already programed across. Just enter thickness of Strike plate added.

[Flyboy718]

Originally posted by Rob DiStefano:
hysterically, for the very most part, all carbon shafting has an incredibly stiff dynamic spine versus it's static spine.  many bowhunters are using 500 spine for a 29"+ arrow loaded with 350grs or more up front, out of 50-55# stick bows.

That's funny...the last time I used carbon was out of my Quinn Stallion Classic 40# @ 29" and I draw to almost 30".  I was using an Easton 500 Lightspeed cut to 29.5" with a NAP flipper rest and 100 grains with 18 grain standard insert and bareshafted perfect at 15 yards.

[Rob DiStefano]

Originally posted by Flyboy718:
 

Originally posted by Rob DiStefano:
hysterically, for the very most part, all carbon shafting has an incredibly stiff dynamic spine versus it's static spine.  many bowhunters are using 500 spine for a 29"+ arrow loaded with 350grs or more up front, out of 50-55# stick bows.

That's funny...the last time I used carbon was out of my Quinn Stallion Classic 40# @ 29" and I draw to almost 30".  I was using an Easton 500 Lightspeed cut to 29.5" with a NAP flipper rest and 100 grains with 18 grain standard insert and bareshafted perfect at 15 yards. [/b]

just goes to prove there are some interesting variances in good working setups ... that the software won't catch.   :D

[metsastaja]

An other small thing THE FOOTING BOX if you use an insert longer the 1/2 inch i.e a 100g brass you need work with the Footing Box. You would change it to yes. add the length of the insert longer then 1/2" and leave weight at 0 since you have calculated it in the insert weight.

[Ray Lyon]

I think it's a little of both.  Use Stu's to get you close and then fieldwork from there.  I find that with my wood and carbon arrows, the numbers are right on from the calculator, but I had already done the fieldwork a couple of years before entering the data. I just wanted to try the software for fun.

[GreenGrizz]

This is just speculation of course, but I think the difference you're seeing is the result of whatever formulas/data Stu used to factor a bow's efficiency.

You can take two bows that both draw 50#'s @ 28" but one of them may not be as efficient at transferring that energy to the arrow as the other. The less "efficient" bow will require a weaker spine than the more "efficient" bow. The arrow shot from the less "efficient" bow will also be slower.

I know this was kind of long but I've been looking at the same thing on that calculator trying to figure out what's going on.

[hkmp5]

Hello All,
Les hit the nail on the head.  The difference is due to the riser cuts of the two bows.  With the Sage being cut 3/16" further in that trumps the draw weight differences by far.  

Also, if you ever want to know what specifics the DSC is using for the automatic inputs just click on the "Data Library" tab at the bottom.  The top line shows all the details with the bow inputs over to the right hand side.  You can see the bows riser cute dimension, the strike thickness, and also the resultant strike position.  Also, if you are not sure exactly what static spine so of the shafts are just select the one you want from the main page and you can see it's details also in the Data Library top line.

There is a new version coming out in Jan which has corrected the speed issues.  Originally the equations were developed off of shooting bench data which uses a clean mechanical release.  I know that none of us have such a great release as that and loose some speed there as well as from slight creep.  The new speed calculation will take both of those into consideration as well as the effect of draw length and not just weight at final draw.  I know you will be much more satisfied with the new speed number accuracy.
Also the new version will be able to handle tapered wood shafts.  Finally figured out how to predict the effects correctly.  You will be able to enter final nock diameters and length and the dynamic spine, final weight, FOC% will all change accordingly.

-Stu Miller

[GreenGrizz]

Stu,
I know I'm not the thread originator but I still wanted to say thanks for clearing that up for me also (The light is slowly coming on).

Jess

[rod251]

Thanks Stu!  I meant to respond to your email yesterday but I got really busy and never got back online.

[Night Wing]

Glad to hear there will be an updadted version of the calculator coming in January. I'll be looking forward to "putting it through it's paces".    :D

[metsastaja]

That is wonderful news Stu. A tool that keeps getting better and better. I want to thank you for the time and effort you have put into this over the years. It is a great gift to the community.

If anyone is wondering where to get the calculator
here is the address.

 http://www.heilakka.com/stumiller/

[TxAg]

Sounds great Stu. Can't wait to play with the new one. I love using the caclulator to get me close...takes so much guess work out for me and saves me money.