How accurate is the 'dynamic spine calc.' ?

[Rob DiStefano]

imho, all spine charts - whether static printed or dynamic interactive - are helpful, but real world testing is always best.

[ranger 3]

Is there any other way to open it besides Excel, I don't have it

[Rob DiStefano]

Originally posted by ranger 3:
Is there any other way to open it besides Excel, I don't have it

get and use the free 'openoffice' ...

http://www.openoffice.org/

[TxAg]

This thread peaked my interest so I went back and took a look at my inputs.  Since the last time I calculated (maybe 6 months ago) I've revamped my form just a bit so my drawlength is about 1/2" longer now. To acommodate, I recently bought arrows 1" longer just to be safe.  With the new data, I'm within 0.1, while I was within 5.0 before that.

[daveycrockett]

I really think it is fairly accurate if fed the right info. You know the old saying, garbage in garbage out.

[ranger 3]

Thanks Rob, works like a charm

[wingnut]

I've been using and distributing Stu's calculator since it first came out.  What I find is you can be real close before you start testing.  Too many times I've wasted hours with combos that weren't close enough to adjust from.  With this I usually can take my points and go to work.  Set it up as designed and adjust point weight to weaken or strengthen spine as requires.

Had a customer the other day stop in and we designed an arrow.  He called Big Jim from the shop and ordered the shafts.
Fast forward a week and he had his shafts and fletched them up.  We again checked his drawlength and cut one arrow as designed in the program.

Took it out and it flew like a well arrow.

Set up number two for BAB (big a$$ broadhead)testing and started shooting two shot groups.  Made the nock point adjustment to move them together up and down.  They were hitting 4 inches left at 20 yds.  I went up 25 gr in point weight and they moved too center.  Added 25 grains more and they started stacking in the center every time.

What we found was that when he shoots, he ends up about 1/2" shorter on drawlength then when we tested him.  The additional weight makes the shafts slightly weak and thats exactly where we wanted them.

Took less then an hour and he walked away with the best shooting bow and arrow combo he's ever had.

Mike

[ishoot4thrills]

I like Stu's calculator. I think one of the most important entries is the one for the center-shot variation. If you're gonna enter something wrong, that's probably where it's gonna be. I think it's the most difficult one to get correct also. It's so important because it has so much influence on the final results and on arrow flight/spine.

[NDTerminator]

I don't know Stu but if I ever run across him I'm buying him a beverage of his choice.  Heck, I'll buy him a bunch.  At the cost of shafts nowdays, the money a guy will save in no longer flying more or less blind when trying/switching to something new is going to be substantial...  

[hkmp5]

You guys are the best!  To hear that this DSC is helping others and that you find value in it makes all of the long hours it took to define the equations it uses all worth while.  My intent for it always has been to provide a simple tool that would get most shooters very quickly into the ballpark from which they could "fine tune" with actual shooting.  I totally agree with Rob that actual shooting by comparing fletched and bareshafts will always be the end-all decision maker for whether things are tuned correctly.  That said and based on the mass amount of feedback I have recieved from all over the world, I am very please on the accuracy that it is providing to the majority of shooter who take the time to check the inputs carefully.  Finally, thank you all also for the help you have provided along the way with real world shooting experience and feedback...I appreciate all the experience and good data out there!  I will continue to add features and improve it as best I can.  I also promise that it will forever remain a free gift to our fine trad achery community.
God bless,
-Stu

[hayslope]

Stu,

I am only one of the "grateful" souls out there that thank you for developing this tool.

I am also one that can appreciate the amount of time that it must have taken to work out the formulas (having much experience at doing exactly that when Excel's "canned" formulas don't quite fit the bill).

Your "calculator" has certainly lived up to expectations.  At my age, I can think of many things to do in the amount of time I've saved using this tool.  My hat's off to you sir!

[lucky strike]

This might help some guys that are confused about
the shelf cut on Stu's calculator as to +and -.
For right handers:( Lefties do the oposite)
1-Hold the bow looking at the belly(side facing you when you shoot)and center the string to the middle of the upper limb.
2-if you see a space between the string and the shelf to your right hand side that is a minus figure.IF you see no space it is center cut. And if you see the shelf going past the string to your left hand side that is a plus figure.
3- now take a piece of masking tape and put it acoss the upper limb at widest point-measure the with of the limb and put an ink mark on the tape at the center point-From there make a series of 1/8" lines on the tape left and right of center.Mark the center line on the tape as zero.
4- put an arrow on the shelf,and eyeball down the shaft and put the string directly on the inside edge of the arrow shaft-without moving look up and see what line the string is on your tape marks.then subtract or add it to the mark you made for limb center-This will give you almost perfect + or - measurement for the cut # to place in Stu's calculator.( if your getting say a 3/16 figure it's probably the shelf material-just subtract it-almost all bowyers work in1/8ths.

By the way -we should commend Stu for the work he put into it-If done correctly it is extremely accurate!

[metsastaja]

Kind of what lucky was saying

[hkmp5]

Hello Hayslope,
Thank you sir for the kind words.  It is appreciation like yours that makes all the time and effort well worth while!
-Stu

[Freeze]

hkmp5,

Just used it (again) the other day to help a buddy change shafts.

Thanks for the great contribution.

-Freeze