Why can't I bare shaft tune?

[GMMAT]

Using a brass insert will stiffen your arrow, too.  The length of the insert is a portion of your arrow that is now NOT flexing.  I found this outtthe hard way (having epoxied in my 100gr. brass inserts).  30" 250 with a 225gr tip is fine.  Same arrow with a 100gr. brass insert and a 125gr head is too stiff.

If I had ANY advice to give on this....it would be 2 words.....HOT MELT!....lol

(I'll never use epoxy, again!)

Good luck!

[Don Stokes]

Feathers cover up a lot of spine and/or form problems, but when you put your broadheads on you'll find out if it's right or not.

[alex o]

I'm using Muzzy 125 Phantoms and they fly just like field points.

[xtrema312]

The spine calculator can only be used for a ball park number to start working.  I have had stuff tune 5-8 pounds off the calculator numbers and other stuff dead on.  50 gr. brass inserts are the basically the same length as standards, but 100's are longer and make the shaft act shorter in my experience.  When I ran your numbers based on the cut to center Predator at 60#@28 with 29" draw and FF string it was like 74# spine.  The arrow was like 50 something.  Now many things can change that number like silencers, bow quiver, brace height, bow efficiency, form, how hard you grip the bow......  

I have the latest version of the calculator.  I can run the numbers again tonight.  From what I saw last time that extra arrow length was a factor.  Cut that off and you would be close enough that other variables could get you tuned.  Now BH flight is what really matters in the end.  If you BH’ fly with the field points at say 25-30 yd. and you are shooting consistent then you should be fine, but you should also be able to shoot a reasonably consistent bare shaft also.  Got to love those Phantoms.

[xtrema312]

31" FMX 400 with 175 point is 57.7# spine.  60# @ 28" predator cut to center, FF string and 29" draw is 74.4#.  If you cut that shaft to 29.5", 1/2" more than your draw, and your bow is 60# @ 29" you would have 68.2 arrow and 70.5 bow.  That would be real close, and I would work that arrow length down a little at a time to fine tune to you.  That is what they calculator says for what it is worth.  If your side plate is built out some from center it would make a big difference also.  I would not seem like you would be way too stiff so it is hard to explain that your bare shafts go all over with no pattern to their flight.

[LC]

Beg borrow or what ever get yourself a video camera with a tripod and record your shooting. Bet if you watch closely you'll discover the problem and IF you fix it your shooting will improve along with your bareshaft tuning woes.

[alex o]

With the calculator ypou have to take into acount the thickness of the sideplate material. I am using the velcro sent with the bow which is kind of thick, puts me out to atleast 1/16", possibly 1/8"(hard to tell with the old eye)

[T Folts]

Alex
For me I used a wooden match taped on my bow to use as a site just for tunning. I had to start at 15yrd to get good groups with the fletched then once I was consitant paying attention to my form and smooth release. After I was ready I was able to move back. This took me quite a bit of work before I got consistant results. I also made sure my bow was straight up and down not canted.
Terry

[metsastaja]

Guys be careful with Stu's calculator version 8-9-09. Unless you are using Microsoft Excel.

Some of the other spread sheet programs Open Office.org for example give strange numbers that do not match and can be way off.

if you want to try the Stu's calculator it is available on line for download at

 http://www.heilakka.com/stumiller/  along with a pdf instruction sheet.

[xtrema312]

That is correct, and 1/8" makes a big difference.  Are you 60# at 28 or 29?  Do you have a Huntersnitche Predator?  If it is their standard riser cut and not some custom, they cut them past center and build them out to center with the strike plate material.  If I recall correctly mine liked a weaker shaft than the calculator indicated, but more like 5# weak.

I am running my numbers in excel.  The numbers I get for my bows are very accurate, but your mileage may vary.