trouble with Stu's calculator

[DaveT1963]

OK I plugged everything in to the Stu Miller's calculator and it states I need a 51.7# spined arrow. However, I use GT 33/55s cut to 30 inches with a 100gr brass insert and 175gr heads... the things fly like darts out of my bow and hit exactly where I look. They spine 34.4 on the calculator. Whern I use heavier spined arrows, or cut the 33/55s down they fly right and appear to be over spined? Just curious if anyone else has found a much weaker spined carbon to fly better out of a non center cut longbow (JD Berry Vixen - 51#s at 27.5 and I pull around 28.5 inch draw)

[xtrema312]

I tend to have to be weaker than the calculator with carbons, but I also find that the HFOC with extra overhang acts a little different also with a carbon.   There is kind of a second tune spot I can find with carbons tuned a lot weaker than they should be.

Your bow must be cut a ways out from center for that arrow to work.  I shoot bows about that same weight and just a little longer draw length. I can’t shoot the GT3555 because it gets too light for me when I get the point weight down to get it tuned.  I shoot a 30” 5575 with 100 gr. insert and 175 point out of my bows that weight.

[Whip]

I have noticed the same thing. My now is heavier - 57@29, and I use 55/75 GT with 275 up front just like you.  The calculator says my arrows are weak.  Used to fret about it, but have come to the conclusion that my goal is to get them to fly like darts, not match a number on a chart. The calculator is a good place to start, but not the end goal.
Shoot what works.

[WESTBROOK]

Thats pretty typical with the calculator and more so with bows 1/8 and more from center.

Eric

[threeunder]

That's typical for a lot of people using carbons.  Like Whip said, Stu's program is but a starting point.
I've found that carbons are pretty happy (read usable) from the point of being moderately underspined to the point of being spined correctly.  However, they are not happy at all being overspined.
Ken

[Shawn Leonard]

Remember carbons recover way faster than other materials used for arrow shafts. I am most certain that most folks should take most recommendations for spine and go a whole spine group lower, say .400 to .500 spine and than add 50 grains to what the recommended point weight was for the .400 spine and it will get them close. So if someone recommends a 30" 55/75 with 225 up front, go to a 35/55 with 275 up front and you will be better off and closer to what ya need to be shooting. Just my opinion. Shawn

[Caughtandhobble]

I roughly ran your numbers and I found that you're pretty much dead on with your setup, ~3 pounds difference. Like I said it is rough but I'm a believer in Stu's for a great starting point.

I do back Stu's up with bare shaft tuning. Stu's usually gets me pretty close. Bare shaft tuning gets me dead on.

[mcgroundstalker]

IMHO, Stus calculator is a starting point... Our physical make-up, how we hold and draw a bow, etc. are not part of Stus input...    It is a great tool none the less, and has helped with my shooting... Still, we need to understand that "we" are a big part of shooting accuracy.

... mike ...

[DaveT1963]

OK another silly question.  With higher point weight do you find that you need to lower nock point?  Since I added the brass inserts and also increased field points I noticed they tend to want to fly nock up.  If I drop the nock set 1/8 inch things straighten up pretty quick with bare shaft.

I do noticed that the 33/55s hit the target with nock left but hit where I am looking.  Is a little nock left on bare shaft exceptable?

[reddogge]

I don't mind a little nock high bare shaft, within reason. They seem to fly great with feathers and give me enought feather clearance to be shot off the shelf. When I tune as long as I get the right and left good I'm happy.

[Rob DiStefano]

Originally posted by Whip:
... The calculator is a good place to start, but not the end goal.  Shoot what works.

           

[bowslinger]

I have noticed the same phenomenon, that being if I shoot a heavier point, I need to shoot a lower nock height.

[Fanto]

i was shooting 3555s from my 55lb bow, cut to centre. (martin mamba)

i cut them to 29" and put 225 up front.

they were OK but the 5575s fly much better.

i use 7595s cut to 29.5 from my 60#. with 325 up front

cheers

[Archie]

Stu didn't work at all for me.  I quit messing with it and just bareshafted my way to a proper setup.

[StickSlinger74]

Originally posted by Archie:
Stu didn't work at all for me.  I quit messing with it and just bareshafted my way to a proper setup.

x2  I did the same thing.  Tried it a few times and always had me over spined for every bow even with all measurements put in correctly.  Bareshaft works for me every time!!

[DaveT1963]

I went out bareshafting today.... what I noticed was at 15 to 20 yards I could see the shafts take a hard bock right, tail high but then they strsightened upvfast and they still hit where I was looking.... both 15/35, 33/55 and 55/75s so I'm confused as heck.... all of them hit where I was looking but the 15/35s seemed to have most movement..... 33/55s and 55/75s both flew good no matter what size field point I used?

[DaveT1963]

I went out bareshafting today.... what I noticed was at 15 to 20 yards I could see the shafts take a hard nock left, tail high but then they straightened up fast and they still hit where I was looking.... both 15/35, 33/55 and 55/75s so I'm confused as heck.... all of them hit where I was looking but the 15/35s seemed to have most movement..... 33/55s and 55/75s both flew good no matter what size field point I used?

[DaveT1963]

33/55s just seem to be the best for my set up.  I started tinkering with cutting the shaft down and when I got to 28.5 inches, with 100 grain inserts and a 200 grain head the bare shafts seems to fly best.  I was planning on using 160 grain heads so I guess I will now need to fina a solid 200 grain broadhead to use.... any suggestions?

[JohnnyWayne]

I had a lot of trouble with it as well, switched to Arrow Dynamics shafts and haven't looked back  

[Shawn Leonard]

Use a 175 grain VPA Terminator, you will not notice the 15 extra grains in your arrow flight, I promise and once ya sharpen them a few times they will be around 170 grains anyway. Shawn