Spine Tester Design

[gfugal]

I've never heard of bareshaft testing but it sounds like a great idea. How do you normally tell if an arrow is too strong or too week like that? It seems that main problem is arrows with too strong of spine. 

[bjrogg]

Bare shafting is just what it sounds like. You take your arrow with point on and no fletching shot it at target from about 6 yards. If it flies straight it golden. If it flies sideways with tail end to the left (for right hand shooter) spine is to weak. To make dynamic spine heavier you can shorten length of arrow, or use lighter point. If arrow flies sideways with tail to the right spine is to heavy. To make dynamic spine lighter you can file or sand shaft diameter or use a heavier point. For hunting arrows you bare shaft with same weight target points as your broadheads, then switch points when done broad shafting. One other tip mark arrow to know which way you have arrow on bow. Sometimes arrow will shoot lousy  one way and you flip it over it shoots great. You want to know which way so you fletch it right. Also it's usually best to have stiff side towards bow. It's also important to have constant release and anchor. I hope I explained that so you can understand it. It sounds complicated but once you figure it out it's really simple
Bjrogg

[loon]

I had light arrows with a 200gr point (plenty of foc, maybe spined 35#-40#), out of a 50# bow. They were still hitting the target at an angle at 20 yards. Maybe it was also my release, but spine definitely matters

[bjrogg]

If spine isn't right for arrow to match bow. They will fly sideways with out fletching. They will if there to weak (tail to the left) and they will if there to stiff (tail to the right). A longer arrow with a heavier point will make actual dynamic spine of arrow weaker.  If you cut a inch off same arrow, or put a lighter point on it. This same arrow will have a stiffer actual dynamic spine. The real nice thing about spine tester is once you find the magic combination for your bow you can much more accurately duplicate another arrow. If I didn't explain this so you can understand it just try shooting next arrow you make without fletching ( I never fletch mine without shooting them first anymore). Then flip arrow over and shoot it with other side against bow, or add tip weight, maybe shorten arrow .Once you see what's happening the light bulb might come on. The bow can make a huge difference to. A bow shooting off the handle will be fussier about arrow spine then a bow with arrow shelf cut close to center shot. Hope that helps I'm trying to keep it simple it actually really is.
Bjrogg

[bow101]

If spine isn't right for arrow to match bow. They will fly sideways with out fletching. They will if there to weak (tail to the left) and they will if there to stiff (tail to the right). A longer arrow with a heavier point will make actual dynamic spine of arrow weaker.  If you cut a inch off same arrow, or put a lighter point on it. This same arrow will have a stiffer actual dynamic spine. The real nice thing about spine tester is once you find the magic combination for your bow you can much more accurately duplicate another arrow. If I didn't explain this so you can understand it just try shooting next arrow you make without fletching ( I never fletch mine without shooting them first anymore). Then flip arrow over and shoot it with other side against bow, or add tip weight, maybe shorten arrow .Once you see what's happening the light bulb might come on. The bow can make a huge difference to. A bow shooting off the handle will be fussier about arrow spine then a bow with arrow shelf cut close to center shot. Hope that helps I'm trying to keep it simple it actually really is.
Bjrogg

Yabut.  What is a Yabut.?  Kind of like a Rabbit.?  Nope.!  Just a discrepancy in arguments or opinions.
Just finished 1/2 dozen arrows they all fly ok but one.  Can you really get any better odds after doing paper tuning or bare shaft tuning.
I have read countless articles about the Masters like Fred Bear.  The wall flyers were broken and discarded.  Why keep a bad arrow. 


Agreed...........?......

[bjrogg]

Let's just agreed to disagree 101.
Bjrogg

[bow101]

Let's just agreed to disagree 101.
Bjrogg

Yup your opinion,  what makes you so right.?  You disagree with the likes of Fred Bear, and you are an expert....... >

[bjrogg]

Happy Thanksgiving 101

[bjrogg]

Gfugal I hope this offers you some help. I'm not claiming to be an "expert" but I have learned a few things from people much smarter than me and this is how I use bareshaft test and spine tester and scales to reproduce my arrows as close to the same as I can. I especially like it for my stone point hunting arrows that I want to replicate but really don't want to shoot a lot. Those I make to the numbers that work for my target points and knap point to that weight. I know there are some other good post on bareshaft testing and spine testers. Also a lot of you tube videos out there too.
Good luck try it if you like I didn't invent it but I do use it.
Happy Thanksgiving
Bjrogg

[Danzn Bar]

I'm with ya BJ...
DBar

[bjrogg]

Thanks Bill, you would definitely be one of the people I learned from. Thanks so much for taking the time to show me a few of the tricks of the trade.
Bjrogg

[bow101]

Happy Thanksgiving 101

I'm on Canada time...

[bjrogg]

I noticed that 101, I do hope you had a good one just the same. I really do mean that 101 and many happy days besides
Bjrogg

[bow101]

Seriously bjrogg...: do you really get 80-85% accuracy from wood arrows...?

Second question how about 30 yard shots. ?   Its a tough call especially from a wood bow.

Thirdly, would I attempt a kill at 30 yards. ?  not with my shooting ability.   Others have though using traditional bows...

[gfugal]

I'm putting this here mainly for my own reference so I can find it again years down the line. Someone asked how to determine spine for an arrow shorter than 26" so you can compare short arrows bendability to longer arrows.

You can figure this based off the equation to the far right in figure 1. The little squiggly thing in the equation in both images represents deflection. The second image shows the simplified equation solved for deflection. Using this equation you can solve for the theoretical deflection at 26 inches.

For example, If you measured a deflection of 0.35 inches at 24 inches then to get the deflection at 26 inches you plug it in.
 D1 = D2•(L1^3/L2^3) = 0.35•(26^3/24^3) = 0.35*(17576/13824) = 0.35*(1.27) = 0.44
Therefore the deflection at 26 inches is 0.44 inches or 59 lbs.

This is only helpful if you want to compare to 26" arrow shafts. If you don't care about that then just get a deflection value and use that to compare to other 24" or whatever length shafts you happened to measure.