Rotational Flight... Energy Lost?

[BT]

SMJ got me thinking.
(Don't start sending him hate mail! )

What are the losses that one might suffer from fletching an arrow to enhance rotation?.

As I was driving around today, I started thinking about this and the more I thought about it.....the more I started to think that my chosen straight fletch may be more beneficial than I had imagined.
So far, the only positive I have seen from rotational travel is stability.....which is over rated (IMO) in my past hunting scenarios.
The negatives however are numerous (potentially) in those same hunting scenario's in respect to the following....

As was stated previously elsewhere b SMJ, it takes energy to spin an arrow.
Any energy spent is energy lost unless the end result lessens the overall workload to a degree greater than the energy spent to accomplish that feat.
This follows the same logic as the Momentum V.S. K.E. argument.

With guidance being tossed out for hunting scenarios from 0 - 50 yards, what benefit to the helical/off set fletch?.
I simply see none
I have seen negatives when speaking to plastic vanes hitting light obstructions.
But that isn't fair to discuss right now (I guess) since I am talking about energy losses in flight.
I do see that at some point down range, energy losses will be very real, but to what extent?.
I don't know as it would be enough to be bother with

Impact energy loss with COC or Chisel is another question
Where is energy being transfered to and which head allows more transfer back into the shaft as compared to the area of impact?.
(Spiker and I were talking briefly about this yesterday)
Does shaft rotation detract from transfer to the impact area? and is that loss (if it exists) increased by a COC head as opposed to the chisel point?.
Is it easier to break a reed by bending it or by twisting and bending it.
Is it easier to enter any material (under forward rotational force) with a drill bit or a spade bit?.

Here is where I really see losses stacking up dependant on the degree of off set or helical.

Discussion group?

[madoktor1]

Ok let's see if I can get my thoughts straight. I see helical and off-set as two separate scenarios due to the radical difference in angle. Off-set is usually minimal and a straight angle whereas helical is literally twisted around the shaft and provides more drag surface.

I prefer a slight off-set to a straight fletch for quicker stabilization and flatter trajectory over distance. Of course this is perceived from shooting both straight and off-set styles back to back. I will usually shoot a little higher with an off-set than with a straight from 30-50 yds, but I it applies more for longer shots than short ones. With my set up, I do not notice an increase in arc until I get to 50 yds. and beyond with an off-set. The arc increases at 30-40 yds. with a straight fletch. As far as speed and impact go, I don't believe there is enough difference in these two to worry about. The actual figure would probably be several digits to the right of the decimal point.

I think helical would be a different story. It would flatten and stabilize almost immediately, but speed and KE would drop off more quickly than either of the other fletch styles. Like the 5" Flu Flu's that were mentioned in another post. The drag coefficient would be increased exponentially and I would venture to guess that KE would be reduced by almost half as would your range. It would not even come out of the bow as fast as any other style.

I can see advantages in an off-set from personal experience but see no advantages in a helical other than Flu Flu's which are designed for nominal KE in a short distance as they are used a lot for hunting various winged animals.

Now for the broadheads. I believe there would be more energy loss quicker with the COC with any kind if rotation because of the larger area the force is being applied to. Like drilling with a spade bit. During the course of the drilling process, you can feel the torque in your hand by the drill wanting to spin back so the force required to turn the spade bit is greater that for a drill bit. Therefore, the force exerted on the COC is greater than the chisel point but the COC has more area to disperse the force so there would be less transfer back to the shaft as more would be applied to the tip of the COC. The chisel point would have more forward momentum with more energy transferred to the shaft because of less resistance on impact. Like the drill bit.

I think what would affect either broadhead as much as amount of rotation, would be the size of the point. The larger the point, the more energy that will be lost at impact from rotation. Whereas a straight fletch removes all of this from the equation. If there is no rotation, then there would be no loss or transfer of energy. An object in motion tends to stay in motion unless acted upon by another force. In this case, the rotation would be the other force.

As for the reed, it would be easier to break it by bending it than by twisting and bending because the twisting would increase the tensile strength of the reed. This would also mean more force to bend it. JMO.

Hope it all makes sense. LOL

[BT]

good God!...we were separated at birth!!

I think helical would be a different story. It would flatten and stabilize almost immediately, but speed and KE would drop off more quickly than either of the other fletch styles. Like the 5" Flu Flu's that were mentioned in another post. The drag coefficient would be increased exponentially and I would venture to guess that KE would be reduced by almost half as would your range. It would not even come out of the bow as fast as any other style.

I can see advantages in an off-set from personal experience but see no advantages in a helical other than Flu Flu's which are designed for nominal KE in a short distance as they are used a lot for hunting various winged animals.

Traditional archers would enhance performance by using a helical fletch pattern as well as some compound shooters that shoot fingers.
The reason being is that as the arrow enters the archers paradox, the drag/rotation of the helical will aid in stabilizing the arrow faster than the offset fletch pattern.
Second choice would be the straight 4 fletch pattern which is the best of both worlds in terms of drag and clearance.

As for the reed, it would be easier to break it by bending it than by twisting and bending because the twisting would increase the tensile strength of the reed. This would also mean more force to bend it. JMO.
Hope it all makes sense. LOL

Hmmm....that sounds good.

Here's something to consider....
Are we talking directional fibers or non-directional?.
Here is what I am thinking....
If you have a directional fiber, the act of twisting those fibers against each other over their length would act to weaken the center where the maximum leverage is achieved.
I do not mean to say weaken the overall strength but rather the spine.
When twisting, at some point the center will try to overcome the stress by moving out of it's center line if force is applied inward as well.
Am I correct?....I cant state this as a fact but I bet it would be easy enough to test with a laser level and a scale.
What I have seen is that directional shafts are very strong, until you twist them.
By contrast, non-directional shafts are near impossible to twist in the first place
SO...if we are referring to twisting the most common shaft construction, I am pretty sure you are correct.
As to what little twist as could be added, it would indeed act to add strength as I don't believe it could actually be twisted far enough to cause detriment.

[SPIKER]

Wax on...Wax off....

[smj]

Wow... Lets see...

No net gain by having the arrow turn... What about during big wind? Now, this would also take in FOC, tip design, and so on... But does the added stability of spinning during flight add to the performance when the wind is screaming? How much force from fletching is needed, and at what point does more fletch driving just become overkill?

A quiet arrow is an efficient one. If it spins, how much energy is spent? Probably a lot to get it started spinning - relatively speaking. Probably not much to maintain spinning once started, assuming that the arrow is otherwise quiet in flight. Flu-flu's are not quiet in flight. In general, feathers make more noise than smooth plastic... Plastic being faster.

If you have a good group at 50 yards - probably just need to fletch up a couple arrows, differently of course, and see what the difference is in drop over 50 yards. That would indicate the difference due to spin/fletching loss. Still, if the arrow makes noise, the loss would not be purely spin conversion loss. A noisy tip is a thief, too.

COC verses chisel tip - other than breaking bone, I suspect that the COC wins every time - provided it is really sharp, twisting or not. Also assuming well designed tips, with quality blades. Chisel tips have 3 or 4 blade edges and pressure faces (thinking of rotational forces), not just two as with a simple COC tip.

[royden]

interesting thoughts

too much for 0530 before work!

I notice two things, spinning arrow would restabilize better if something goes wrong - release, grip, wind, etc. Straight fletch demands better condidtions. spinning arrow may also stay straighter on impact and flex less, therefor losing less energy A good comparison may be a blade of grass stuck thru a fence post - how exactly does a tornado do that???

the center of the broadhead has the least amount of energy loss when spinning - the outside edges of an 1.25" head take the most energy to turn (try turning a 1"hole saw by hand, versus a 1/4" drill bit)

I'm late for work now!!

[Buckshot06]

Dec 31, 2008 7:29:12 GMT -5 royden said:

interesting thoughts
I notice two things, spinning arrow would restabilize better if something goes wrong - release, grip, wind, etc. Straight fletch demands better condidtions. spinning arrow may also stay straighter on impact and flex less, therefor losing less energy

I agree , but also a COC head may lose some KE do to spin but compared to what and how much? A chisel tip takes more KE to push through hide than a sharp COC. So what is the KE difference verses a spinning COC and a straight fletched chisel tip BH very little I think. Flight is what matters a straight flying arrow will be able to use its whole mass as one compared to an arrow that wobbles in flight will loose more KE due to drag in the air and will not be as efficient on impact with the tip of the arrow no longer being pulling the arrow through the target but rather being pushed off center by the arrow hitting at an angle with even more KE loss do to this. All my shots are less than 50 yds so a straight fletch works great for me. I am able to robbin hood arrows out to 30 yds with set up and see no real benefit as to put an offset or helical on my arrows.

I ask you this "is it easier to cut your steak by slicing through it or by spinning your knife across it?" Here lies your answer IMHO, which takes more energy. So the faster your arrow spins the more stable it is in flight but your BH has a harder time trying to cut through the hide and tissue for bigger KE losses at impact. This is were I feel you will see most of your KE loss not in flight but at impact of the target. You won't see this KE loss with a Field tip but with a BH it will be very evident.

[BT]

Dec 31, 2008 0:26:09 GMT -5 smj said:

Wow... Lets see...

No net gain by having the arrow turn... What about during big wind?
Now, this would also take in FOC, tip design, and so on... But does the added stability of spinning during flight add to the performance when the wind is screaming? How much force from fletching is needed, and at what point does more fletch driving just become overkill?

I think that this would depend on the wind direction.
If a wind is coming from the right and the fletching is turning to the right, that would act to have the fletching digging into that wind....tunring the tail end of the arrow with it.
Same with an on coming wind.
In turbulence, it is better to go straight than curved.
Like putting you hand out the car window....if you hand is horizontal or angled to allow the air to ramp over your hand, no problem.
So....I would suspect that you have a 50-50 chance of having the wind hamper performance with anything like helical or offset.
It would only be a matter or error dependent upon the aggressiveness of that fletch angle.

A quiet arrow is an efficient one. If it spins, how much energy is spent? Probably a lot to get it started spinning - relatively speaking. Probably not much to maintain spinning once started, assuming that the arrow is otherwise quiet in flight. Flu-flu's are not quiet in flight. In general, feathers make more noise than smooth plastic... Plastic being faster.

Plastic is faster (on average) after 40 yards but inside of 30, I haven't chroned any plastic vane that is faster than a parabolic cut feather.
Dorg from firenock is working on a vane that may (sound like it will) out do any feather at any time in regard to speed.
But for now...I haven't seen one.
It's not just the weight reduction (although that is the high % reason) it's also the fact that a feather reduces it's mass (lays down) and then regains that mass as speeds decrease.

If you have a good group at 50 yards - probably just need to fletch up a couple arrows, differently of course, and see what the difference is in drop over 50 yards. That would indicate the difference due to spin/fletching loss. Still, if the arrow makes noise, the loss would not be purely spin conversion loss. A noisy tip is a thief, too.

Plastic V.S. plastic ... thats a good idea.
However, to really know....you would need perfection on the shot.
Anyone got a hooter shooter?

COC verses chisel tip - other than breaking bone, I suspect that the COC wins every time - provided it is really sharp, twisting or not. Also assuming well designed tips, with quality blades. Chisel tips have 3 or 4 blade edges and pressure faces (thinking of rotational forces), not just two as with a simple COC tip.

Absolutely.

[BT]

Dec 31, 2008 7:29:12 GMT -5 royden said:

I notice two things, spinning arrow would restabilize better if something goes wrong - release, grip, wind, etc.

AHHA!...it wold stabilize it better (? I'll come back to that better thing ) in the direction of path AFTER the fact.
Which means the arrow is going right where the error puts it! ;D
Rotation isn't going to correct directional error caused by release or impact with a twig on the way to the target.
Now about that better thing. ;D
(sorry buddy...I have to go after this one )
I will agree with you in total if we are talking 3 V.S. three but straight is not meant to be shot with three fletch
If you are shooting straight then you are going to fletch in an extra vane/feather.
With a 4 fletch.....there is no way at all that 3 fletch offset is going to out perform for stability.....until we really start getting some distance on that shot.
Out where you reside...I would fletch up 3 vanes and offset...no question about it.
However, at 50 yards and under (with 95% of the shots being 45 yards or less) three fletch (and plastic) is not maximizing the potential for arrow construction.
JMO

Straight fletch demands better conditions. spinning arrow may also stay straighter on impact and flex less, therefor losing less energy

I need a high speed camera!...Dorge!!! grab your camera buddy!
Again...4 fletch (straight is far more forgiving due to increased drag without influence to the shaft.
On impact, the arrow that is going straight is going to have no torque at all.
Contrasting that is the helical that is twisting on impact.
I doubt that in either scenario would effect a non-directional shaft but on shafts that have directional fiber....I would bet on the arrow which impacts straight and true.

the center of the broadhead has the least amount of energy loss when spinning - the outside edges of an 1.25" head take the most energy to turn (try turning a 1"hole saw by hand, versus a 1/4" drill bit)

Agreed.
This is most reflected in heads (such as the Stinger) which change their weight by increasing the blade area.
The heavier the head, the poorer flight.

[BT]

Dec 31, 2008 8:48:58 GMT -5 Buckshot06 said:

I ask you this "e; is it easier to cut your steak by slicing through it or by spinning your knife across it? end quote ;
Here lies your answer IMHO, which takes more energy. So the faster your arrow spins the more stable it is in flight but your BH has a harder time trying to cut through the hide and tissue for bigger KE losses at impact. This is were I feel you will see most of your KE loss not in flight but at impact of the target. You won't see this KE loss with a Field tip but with a BH it will be very evident.

I think that visually I can use your example to illustrate what you are saying by rephrasing it.
Is it easier to push a steak knife straight into a rhinehart target or to push the steak knife in as you are turning it?.
Thats a visual with depth and one that anyone can try on a similar target