Primitive Archer

Main Discussion Area => Bows => Flight Bows => Topic started by: Badger on October 14, 2017, 08:35:10 pm

Title: Question on fletching theory
Post by: Badger on October 14, 2017, 08:35:10 pm
    Suppose you had a stiff fletching .01 thick and 3/8" high X 2" long, it seems it would cause little drag as long as the arrow was going straight but have good influence anytime it wandered off straight and bring it back to straight quickly assuming good point weight. I think I have been making my fletching to short in height and length and too thick. It would seem we only need drag when things aren't going well otherwise. 
Title: Re: Question on fletching theory
Post by: willie on October 16, 2017, 04:44:38 pm
Quote
It would seem we only need drag when things aren't going well otherwise.

from working with boats and rudders quite a bit, I would say you need enough steerage to keep thing going well at the lowest speed of the trajectory.
Title: Re: Question on fletching theory
Post by: avcase on October 17, 2017, 12:43:52 pm
According to the rocket builders, the most efficient vane is rather tall and short. The most efficient cross-section is an airfoil because the job of the vane is to provide a counteracting lift. An airfoil does this very efficiently as long as it isn’t misaligned so far that it stalls.

But, with natural materials, this isn’t so easy to do, especially using feathers. I think the Turkish Flight arrow fletch profile is a pretty good compromise where feathers are concerned. It would require a very stiff feather to go much taller and shorter without fluttering.

Alan
Title: Re: Question on fletching theory
Post by: Badger on October 17, 2017, 06:27:57 pm
   I am really not sure when I started the post exactly what I was trying to say but basically I have always thought of the fletches as something I wanted as little of as possible. I am now starting to think studying them might put them to better use. I don't believe the short low fletches can get the arrow to respond as quickly as needed. Light arrows will slow extremely rapidly when they are not in line.
Title: Re: Question on fletching theory
Post by: DC on October 18, 2017, 12:12:10 pm
Has anyone ever tried a different method instead of fletching? I don't know, maybe dragging a ball of fluff or something. Also once the arrow flight has stabilised, what can happen to disturb the flight?
Title: Re: Question on fletching theory
Post by: avcase on October 19, 2017, 12:41:58 pm
One year, one of the Flight archers shot these very short arrows with a long overdraw device called a majra that resembles a tube that was split in half lengthwise. The arrow is nocked to the string and the majra is drawn back with the arrow. He was using a modern bow and very short graphite arrows with no fletching and a heavy point. They seemed to fly pretty well and I believe landed over 300 yards away. His regular length feathered arrows didn’t go quite as far, although they were also heavier so it wasn’t a completely fair comparison.

Once an arrow is stabilized, it is continuously being forced to change its direction due to the curved arc of its trajectory. There are also atmospheric disturbances that occur. The wind a couple hundred yards above the ground is usually different than on the ground where the arrow is launched. I’ve seen Flight arrows do a little dance after they initially stabilize as they encounter turbulence or layers of changing wind direction.  We often find arrows pointing in unexpected directions where they land. Sometimes even pointing the opposite direction that they should have been travelling.

Alan
Title: Re: Question on fletching theory
Post by: sleek on October 19, 2017, 04:00:21 pm
Longer is always better. Things move faster through a fluid the longer they are.
Title: Re: Question on fletching theory
Post by: willie on October 19, 2017, 04:37:08 pm
I was looking for info on laminar flow, (which could be a good thing when designing an arrow for flight), and found this report that has some interesting observations about fletching choices. Are the gas-pro vanes  being used in the non-primitive classes?

 http://www.sciencedirect.com/science/article/pii/S1877705813010680#
Title: Re: Question on fletching theory
Post by: Del the cat on October 21, 2017, 02:25:04 am
I was looking for info on laminar flow, (which could be a good thing when designing an arrow for flight), and found this report that has some interesting observations about fletching choices. Are the gas-pro vanes  being used in the non-primitive classes?

 http://www.sciencedirect.com/science/article/pii/S1877705813010680#
Another "scientific" article written by someone who doesn't understand what the Archer's Paradox is....  >:(
Del
Title: Re: Question on fletching theory
Post by: avcase on October 21, 2017, 01:57:43 pm
I was looking for info on laminar flow, (which could be a good thing when designing an arrow for flight), and found this report that has some interesting observations about fletching choices. Are the gas-pro vanes  being used in the non-primitive classes?

 http://www.sciencedirect.com/science/article/pii/S1877705813010680#

I feel the research these guys are doing in the wind tunnel is pretty well done. It gives some indication of the effect of arrow vibration on drag, which can be pretty significant. One thing I don’t understand in this report is why one type of vanes has such a dramatic effect compared to the other. I guess it may have to do with vibration from fluttering, but it is just a guess. I am not aware of anyone who tried Gaspro vanes in flight shooting. The king of vanes used for Flight archery is another type of very stiff Mylar vane that does not have a curled shape.

Alan
Title: Re: Question on fletching theory
Post by: Badger on October 21, 2017, 03:57:13 pm
   Allen, has anyone ever dried wood vanes. I made a couple the other day and I liked the way I was able to work it. and shape it. Not so sure how well it would come out of the bow though. I am thinking an offset string might remedy that.
Title: Re: Question on fletching theory
Post by: willie on October 22, 2017, 04:02:12 pm
Quote
One thing I don’t understand in this report is why one type of vanes has such a dramatic effect compared to the other. I guess it may have to do with vibration from fluttering, but it is just a guess.
Seems like a reasonable guess, Alan. The spinwing rotation rates are along the order of 4800 RPM @ 150 FPS, as reported in an associated study    https://www.researchgate.net/publication/235908721_Aerodynamic_properties_of_an_archery_arrow
while the gas pros were reported to not have any rotation in the wind tunnel.  Hope it doesn't take near that much rpm to add stability to a well balanced flight arrow.

Title: Re: Question on fletching theory
Post by: avcase on October 23, 2017, 11:57:14 am
Less than 1000 rpm should be more than sufficient. 400-500 rpm should be enough to keep the arrow from bobbing up and down as it realigns itself to a constantly changing direction of travel.  I am not sure how much of an effect this will have on laminar Vs. turbulent flow around the arrow. The model I was playing with always assumes turbulent flow. My real arrows seem to do about 20% better than the simulation and I figure that this might be due to the assumption that the arrow is always 100% turbulent.

It seems one is probably better off always insuring turbulent flow for a target arrow.

Alan
Title: Re: Question on fletching theory
Post by: JNystrom on October 23, 2017, 04:28:55 pm
Interesting tech talk about fletchings! Just popped in to my mind that we haven't talked about two fletch arrows. So the arrow would be fletched only with 2 feathers. Not on opposite side, but on their "original" place, only the third missing. A fletching at say, 10 o'clock, the second at 2 o'clock. I heard that Monus uses this method of fletching and well, has succes. Next time you hit your arrow and break a fletching, just rip the rest off and shoot a perfect flight arrow! Lol...
In case this is proved to be complete nonsense, i blame Mikke (m.reinikainen atleast in paleoplanet) :D.
Title: Re: Question on fletching theory
Post by: avcase on October 23, 2017, 05:22:26 pm
   Allen, has anyone ever dried wood vanes. I made a couple the other day and I liked the way I was able to work it. and shape it. Not so sure how well it would come out of the bow though. I am thinking an offset string might remedy that.

Steve,
I’ve never tried wood vanes. I believe they used to be used on crossbow and ballista arrows. I think I would try bamboo. Tonkin cane would probably be able to take some impact if made thin. I think it would be a lot like the vanes made from horn.

Alan
Title: Re: Question on fletching theory
Post by: JNystrom on November 03, 2017, 02:51:48 pm
So... two fletch, anyone? Not the traditional, but the style Monus uses.
Title: Re: Question on fletching theory
Post by: joachimM on November 03, 2017, 04:22:23 pm
... the most efficient vane is rather tall and short ... But, with natural materials, this isn’t so easy to do, especially using feathers. I think the Turkish Flight arrow fletch profile is a pretty good compromise where feathers are concerned. It would require a very stiff feather to go much taller and shorter without fluttering.

Alan

So if stiffness of feather vanes is an issue, why not reinforce them with the most obvious resource to primitive bowyers: (tacky) hide glue?
It might even allow us to use thinner feathers, e.g. chicken or duck wing instead of turkey / goose, the latter being much thicker and causing more drag.
Title: Re: Question on fletching theory
Post by: Badger on November 03, 2017, 04:31:32 pm
   I was thinking similar, Hide glue on vanes should be fine. I was going to try shellac.
Title: Re: Question on fletching theory
Post by: willie on November 03, 2017, 07:26:49 pm
It might even allow us to use thinner feathers,   :OK

JNystrom, sounds like something worth trying.
Title: Re: Question on fletching theory
Post by: Aussie Yeoman on November 27, 2017, 11:45:30 pm
Years ago I was able to examine a crossbow and bolts from Vietnam, brought back from the war as trinkets.

The bolts had a fletching of thinly split bamboo folded into a triangle, bound into a slot. Of course this mean the bolts were double-fletched. The shape of the vanes were short in length but stood high off the shaft, much like the shape of a concord. It was set as close to the back of the bolt as could conveniently be done so secure with a wrapping behind it.

I thought it was fascinating.