Help with Stu's calculator

[Crash]

I'm having problems getting an arrow tuned to my new Zipper SXT and frustration is setting in on me.   I was hoping someone could run the numbers for me and help a brother out.  The bow is a standard SXT model, 40@28 drawn to 28.5".  I don't know what the centershot measurements are but it has the standard thin piece of calf hair sideplate.  I think I'm close but I'm beginning to doubt myself.  Thanks in advance.

[hayslope]

Jarrod

We'll need some more information from you to plug into the calc.

What arrows do you plan on using, as well as:
point/head weight
insert weight
fletching combination
wraps/nocks

Check with Bill Dunn at Zipper......he should know how the bow is cut and the thickness of the sideplate.

The calc is a MS Excel spreadsheet, so.....garbage in equals garbage out!  Got to put in accurate data to get useful information out!

[Crash]

See, I thought you could put the numbers for the bow in and it would give you recommendations for the arrows.   I have some 15/35's that are 29"s long with 100 grain inserts, some MFX's that are 29"s with 100 grain inserts and some Heritage 150's that are 29.5"s long with standard inserts.   All of them have standard nocks, 3 5 inch fletching, no wraps.  I have a variety of tips from 125 to 200.

[Night Wing]

Originally posted by Crash:
See, I thought you could put the numbers for the bow in and it would give you recommendations for the arrows.

It will so long as you provide the correct info in every one of the boxes in Stu's calculator. The most critical of all the boxes is the Center Cut/Strike Plate Position.....and you're not providing it.

It's not difficult. Take my Blacktail recurve for an example. A Blacktail is cut 3/16" past center. That's (-3/16) on Stu's calculator, but this "isn't" the correct number for that box since the strike plate thickness has to be subtracted out.

My velcro strike plate is 1/8" thick so that is (+1/8) or breaking it down to sixteenths of an inch....(+2/16).

Subtract: (-3/16) minus (+2/16) equals (-1/16) and the (-1/16) is the correct number for the Center Cut/Strike Plate Position box for a Blacktail recurve.

If you don't know if a Zipper is cut to center or past center and if past center, how much past center, call the bowyer. Then subtract the strike plate thickness out.

You can't "guess" in any of the boxes.

[mrjsl]

The arrows that shoot correctly out of both my bows are much weaker than the calculator recommends. All measurements are correct, and I've measured many times.

Moreover, I can set up different length arrows with identical dynamic spine per the calculator and find that they shoot differently (weak/stiff) for me.

I'd listen to what the arrows say rather than the calculator.

[Ground Hunter]

Don't argue with the arrow.

[Rob DiStefano]

the problem with all calculators and charts is that none are "real world", and all are guesstimates of sorts.  none of that stuff can compare to getting yerself a shaft test kit and do the proper hand's-on testing.

[metsastaja]

the Zipper Stx is -1/8
with your sideplate I entered 0.
try 175g BH on the 150's see what happens.

[Shawn Leonard]

Rob has it right!! I bet ya I can get ya darn close. Go with a 29.5" 600 spine and at least 225 grains up front. Stu always has me way overspined even when everything is entered correctly. You may even need to go to a longer arrow or 275 up front. Shawn

[Shawn Leonard]

150's no way even full length!! They are .487 spine again you need to go to a .600 spine if not a .700 spine. I have been at this a long time and have owned several Zippers. I shot 150's out of one of mine and that was 54#s at my 28.5" draw and I cut them to 29.5"s and shot 190 grains up front. The 15/35's(.600 spine) will work for ya but you will need a lot of point weight, like I said as much as 275 grains most likely in between 225 and 275. Shawn

[Crash]

Thanks fellows.  I thought I was close with the 15/35's, just extreme frustration setting in on me.  I hope the extra weight works Shawn as I was wanting more arrow weight than I am getting right now with 125's.