The little things

[RadSav]

I thought today was Friday   Maybe I slept a full 24 hours   So maybe you will have those heads Wednesday.  There will be a couple of them and your autographed book shipped out on Monday.

[D-Rock425]

I thought today was Friday   Maybe I slept a full 24 hours   So maybe you will have those heads Wednesday.  There will be a couple of them and your autographed book shipped out on Monday.

thanks Radsav your the best!

[D-Rock425]

I need to read that book by this weekend before the state 3-D shoot.

[RadSav]

Helical Fletching: Part 1

One of the easiest ways to improve your "in field" accuracy is getting your arrow to spin.  Ask any football fan what happens when a quarterback doesn't get good spin on the ball and they will tell you it usually results in a wounded duck.  The same thing can be said for an arrow that does not spin enough to use force for stability.

The physics of rotating forces is rather confusing so I usually simplify the technical with the term gyro stability.  In reality (simplified) resistive force upon the fletching supplies energy to rotate the shaft on it's axis creating a rotating force of momentum.  The opposing reaction of this centripetal force results in an outward centrifugal force.  The influence of the radially outward force is proportional to the mass of the shaft wall, the distance of the mass from the axis of the shaft and the square of the angular velocity.

The smaller the diameter or the lighter the arrow the faster it must spin to achieve equal stability.  This explains why it was so easy for us to gain stability in the old 2413 and 2213 aluminum shafts as the mass was concentrated further from the axis of the shaft and our mild offset fletching was enough.  Todays carbon arrows are not only lighter, but the mass is less concentrated and located much closer to the shafts axis as well.  We routinely got 1.5" broadheads to fly well on our 2216 shafts back in the mid eighties.  Try doing that today with a 300 fps arrow and a micro diameter carbon shaft.  It's not such a routine endeavor anymore!  Faster arrows do spin faster, but the amount of speed increase is not usually within proportion of the reduce weight and mass orientation of these modern carbon arrows.

These small diameter shafts of today also pose a challenge when it comes to achieving proper offset.  Offset of the fletching regulates the path of shaft rotation.  The more offset the less distance a shaft must travel to complete a rotation.  The less distance a shaft must travel per revolution the faster it spins.  But on such a small diameter a straight/flat clamp can not wrap the fletching around the shaft enough to put an appropriate offset.  The Helical clamp on the other hand rotates the vane base closely enough to the allow for a much greater offset and still make solid contact between the shaft and the vane base.  Some of the newer helical jigs really allow this to occur to a point of perfection.  Bohning's Blazer Helix and Helix tower, Arizona's EZ Mini and EZ Helical Pro are ones I have used that really get you maximum rotation and dang near perfect base to shaft adhesion.  They each have their quirks, but once you get the hang of it they work great!

 

[RadSav]

Helical Fletching:  Part 2

In the FOC section we covered pulling the arrow and the benefits that created.

FOC – Front of Center (Part 1 of 2)…

Charging this arrow with more energy holding cells in the front than in the back basically allows more velocity maintaining power to pull the arrow through the friction.  If we were to try and push from the back all the opposing forces impacting the front would make it difficult to maintain a straight line of flight and maintain a straight rigid shaft.
 
A good visual aid here is to lay a length of string on a table.  First pull the string from one end across the table.  Then try to push the string from one end across the table.

In that visual not only does pulling keep the string straight, but the straight path reduces the amount of friction applied to the string beyond just where the energy is applied.

Well, your fletching works best when it is also pulling.  Only this time the fletching is pulling in the opposite direction.  As the fletching absorbs energy to transfer into the rotation of the shaft it creates a pull, or more appropriately, a drag.  If we add that drag or opposing force of energy to the string example from FOC suddenly the string becomes straight and taut.  The more drag in a shorter amount of time and the arrow shaft and flight path straightens faster and the shot does a better job of holding true.  It also has an effect equal to an increase in dynamic spine.

Helical fletching creates a natural cup effect as it rotates around the shaft.  This cupping effect helps increase the drag upon the back end of the arrow until a maximum rotation velocity and energy transfer has occurred.  During this time of extreme opposing forces, maximum energy transfer forward and maximum drag, the arrow quickly recovers from its paradox.  The more drag the faster the recovery - assuming there is also proper energy forward.

Upon such time as the arrow reaches its peak rotational velocity the helical fletch and an offset fletch exert nearly equal amounts of drag.  This continues until the apex of the parabolic curve is reached and the arrow goes into its transition from being force motivated to gravity motivated.  During that transition the cupped effect of the helical fletched arrow helps stabilize the arrow once more by adding that little extra drag not present in a simple offset fletch.

I personally have not used a straight offset fletch while hunting in over 30 years.  I see absolutely no benefit to a straight offset vane.  Its effect on velocity is nearly nonexistent and its benefits scream loud and clear!  It may be a simple little thing, but it remains as one of the most important details in my arsenal. 

[Band]

Hang on while I go get a physics degree so I can re-read that.  Better yet, I'm going to make it easy on myself and just get helical fetching because Rad endorses it.

[Vo2max]

Let me begin by saying "thank you" to RadSav for this Great post and wealth of knowledge! I'm learning a lot and I've been into archery for 25yrs.

Anyway, I have a question: I am trying to bring up my FOC on my Easton FMJ 300 arrows. I currently calculate an 8.4% FOC using archeryadvantageonline.com. I'm contemplating a 75grain insert which will bring FOC to 14% or if I cut the insert down to 50grains it would bring the FOC to 12%... With to do?

Thanks in advance.

[RadSav]

Anyway, I have a question: I am trying to bring up my FOC on my Easton FMJ 300 arrows. I currently calculate an 8.4% FOC using archeryadvantageonline.com. I'm contemplating a 75grain insert which will bring FOC to 14% or if I cut the insert down to 50grains it would bring the FOC to 12%... With to do?

I'd say it depends on broadhead size and fletching.  If you have enough fletching, enough offset and an average broadhead I doubt you will see much difference between 12 and 14%.  If you are fletching with a jig that doesn't give you a real good helical offset, your fletching is small and/or your broadhead is big I'd go with the 14%.  FMJ's are nice arrows but they are not inherently stable with broadheads.  And they can be a pain to get full rotation due to small diameter combined with heavy weight close to the axis.  When I shot them I went 12.5% with right angle four fletch Blazers just under 3% os.  They flew great!!

[Gringo31]

Tagging to soak this up at a later date...

Thx Rad!

[Vo2max]

I'd say it depends on broadhead size and fletching.  If you have enough fletching, enough offset and an average broadhead I doubt you will see much difference between 12 and 14%.  If you are fletching with a jig that doesn't give you a real good helical offset, your fletching is small and/or your broadhead is big I'd go with the 14%.  FMJ's are nice arrows but they are not inherently stable with broadheads.  And they can be a pain to get full rotation due to small diameter combined with heavy weight close to the axis.  When I shot them I went 12.5% with right angle four fletch Blazers just under 3% os.  They flew great!!
[/quote]

Thank you for the reply...
I shoot two different broadheads and both a bit different... first, the Slick trick 100grain standards and second, the Muzzy Mx-3's. As long as I have the 3 blades lined up with my three fletches using the MX-3's they fly great. And, as long as the FOC is a bit farther forward my FMJ's fly great using these broadheads. If the FOC is a bit back (5-6%) I do not get very good flight. I use a 6degree (I believe... could be 3% however but I do not recall off the top of my head) helical using the Arizona EZ fletch. I've considered moving to the slick trick 125grain magnums but tried not to spend even more money in broadheads! Any input welcomed.

ERIK

[RadSav]

If that is the Arizona Mini it should be 4% if I remember correctly.  Nice if you can keep your fletching on!

If rotating your broadheads makes any difference at all you have problems somewhere.  And it usually isn't the broadhead! 

MX-3 and Slick Trick standards should be very much equal to one another.  The extra blade is about equal to the added width of the three blade.  Myself I'd choose the Slick Trick without a second thought.  Might be hard for me to not go with the 14% with those choices though.  Use some Blue stick on two arrows and try them both on a windy day.  Winner gets a chicken dinner and some real glue after that!

[Vo2max]

If that is the Arizona Mini it should be 4% if I remember correctly.  Nice if you can keep your fletching on!

If rotating your broadheads makes any difference at all you have problems somewhere.  And it usually isn't the broadhead! 

MX-3 and Slick Trick standards should be very much equal to one another.  The extra blade is about equal to the added width of the three blade.  Myself I'd choose the Slick Trick without a second thought.  Might be hard for me to not go with the 14% with those choices though.  Use some Blue stick on two arrows and try them both on a windy day.  Winner gets a chicken dinner and some real glue after that!

Thanks for the help RadSav! The EZ fletch has been great for me actually... have others had issues?

Oh, calling me out with my bow tuning abilities?  . Call away man! I could probably use the help. Just within the last two years have I begun to truly focus on tuning and the finite details it takes to become more consistent and proficient with the stick and string... too much school, job(s), moving, kids, life etc got in the way before.

Anyway, Thanks for the advice on the Slick Tricks... any belief that the magnums would be better? I'm going to get the 75grain inserts which will bring the FOC to 14% and see how they go. wish me luck.

Thanks again,
ERIK

[RadSav]

Oh, calling me out with my bow tuning abilities?  . Call away man! I could probably use the help.

Not calling you out at all.  When rotating broadheads makes a difference even in the slightest, I first look at spine, then bow tuning, then FOC, then fletching.  Any difference with broadhead alignment is going to happen in the first five yards of flight.  It's not that the alignment is making a difference - it's just that you have found a consistent point of failure.  That failure has nothing to do with the broadhead.  Perhaps a larger broadhead makes the failure more evident than another head would, but that's about it.

Unless your arrow is excessively long you can probably rule out fletching.  The Mini and the Blazers should be a fine combination.  Unless you are shooting an excessively long arrow and some monster poundage the 300 spine should not be flexing too much.  So now we are talking bow tune and FOC.  8.4% is not excessively light, but combined with a large broadhead in the MX-3 and the small diameter arrow it could certainly be enough.  Absolutely not optimal!  8.4% plus an ever so slight tuning issue would be my best guess.

Myself I would creep tune and bump up the FOC.  If you still see a difference I'd then take another look at the rest.  If the rest proves to be tuned to perfection and the rotation of a broadhead is still making a difference?  Then blame the fletching and step up to a Max Hunter or four fletch.  Though I doubt you will need to get much further than the simple FOC improvement. Unless, once again, you have very long arrows and are shooting Safari level poundage.

[RadSav]

What length are your arrows?  What bow/poundage/draw length are you shooting?

[JJB11B]

reading through all this makes me feel stoopid... I am having a hard time visualizing what you are saying. I know now that my bow is not tuned correctly though....HELP!