Author Topic: parasitic drag  (Read 1402 times)

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Offline Scyth

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parasitic drag
« on: February 10, 2019, 10:03:06 am »
Forget the amount of bow poundage you’ve got . . .

How much arrow parasitic drag do you want to occur ? ? ?

Foreground : a normal 5/8” x 4” sized fletching
( .625 x 4.0 ) / 2 = 1.25 square inches)

Background : my 7/16” x 3.5” sized fletching
( .4375 x 3.5 ) / 2 = 0.7656 square inches)

( . . . my fletching has about .6125 % drag comparing to “normal” . . . )
"Retirement is not a word in the dictionary of craftsmen
and I will carry on my work a long as I can . . . "

- Yang Fuxi

Offline Pappy

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Re: parasitic drag
« Reply #1 on: February 10, 2019, 03:41:05 pm »
OK, I guess you are saying larger feathers slow and arrow down more  ??? Who knew. ;) :)
 Pappy
Clarksville,Tennessee
TwinOaks Bowhunters
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Offline mullet

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Re: parasitic drag
« Reply #2 on: February 10, 2019, 04:10:27 pm »
Wow! Usually, by the time a deer or hog hears that drag they are stuck.
Lakeland, Florida
 If you have to pull the trigger, is it really archery?

Offline bronco611

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Re: parasitic drag
« Reply #3 on: February 11, 2019, 03:01:25 am »
since we like to tune with a bare shaft why not shoot bare shaft then you can be as math illiterate as I am an get by? Just kidding, I like slow arrows, makes it easier to see where it went when I miss!
FLINTKNAPPING IS EASY...I WAS ALWAYS TOLD I COULD BREAK AN ANVIL WITH A POWDER PUFF.

Offline Scyth

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Re: parasitic drag
« Reply #4 on: February 11, 2019, 11:01:09 am »
At 15 yards - point blank - the difference is hardly noticeable . . .

at 30 yards the cumulative difference is quite noticeable ! !

( . . . what I seek is the best possible solution to parasitic drag : waste not  ultimate applied energy of the bow  . . . )

http://www.tap46home.plus.com/mechanics/ffletch.htm

regards,

Scyth
"Retirement is not a word in the dictionary of craftsmen
and I will carry on my work a long as I can . . . "

- Yang Fuxi

Offline TSA

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Re: parasitic drag
« Reply #5 on: February 11, 2019, 07:02:50 pm »
i have chased my tail on this for years, and i dont know if there is a definitive answer.
in the end, i focused my energy on getting a really good bare shaft tune- got my spines all within a pound or two of each other, then with a well tuned shaft, i felt i could go with shorter , smaller fletches_ i use a 4" fletch, and certainly no higher than 1/2" at the high end of the shield cut.
and i could then also reduce my angle of helical- i still want them to rotate- but the less helical there is, the less drag.
i really work hard at getting the shafts really straight, and i get the broadheads properly centered and the glue on nocks properly centered- that way i feel that i can reduce some of the helical.

its all a trade i geuss- if one is shooting wide , heavy 2 blade  broadheads then i would think  more fletch would be advisable.
i like to shoot 3 blade heads- 1. cos i like the hole they make, and 2. i think they are less prone to planing-

i do need to use shields as they are part of my anchoring system, but from all i have read the banana cuts will  produce less drag and less noise.

another thing i strongly believe in, is putting a tail taper on the shafts( well most of you guys shoot , shoot shafts anyway- so they came pre tapered ;D) as one takes mass off the rear of the shaft, one is inadvertently improving the foc, on a std shaft its a ratio of about 1 : 1.6 .
so if you take 10 grains off the rear of the shaft- its like adding 16 grains to the front.
the increase in foc- (without actually adding weight to the front) helps an arrow stabilize quicker- and that in turn helps justify a reduction in fletch size. as i am relying on the well tuned shaft, and the higher foc to do most of the stabilization, as opposed to big ol' fletches dragging the shafts back into alignment via the use of drag and rotation.

we also have very wind conditions here where i hunt- and i seriously worry about the arrow weather vaning in a cross wind- smaller fletches also help in that regard.

anyway- i dont know if all that mumbo-jumbo helps at all- just my .02c on the conundrum!

i did a lot of tests, on how to improve the FOC, without actually adding mass to the front of the shaft, as i did not want excessively heavy arrows- just good 10GPP arrows with a good foc.
 helping to facilitate better penetration, better recovery times, and reduced drag on the stern.
i have those results from those tests- if they may help you

Offline rebsr52339

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Re: parasitic drag
« Reply #6 on: February 12, 2019, 01:48:22 am »
Scyth, haven't heard such a well defined dissertation on "parasitic drag" sense I graduated from Aeronautical Engineering. Well done and in "simple layman's" terms. Seriously, drag is a complex part of an equation which effects different bodies in somewhat different ways. Your graphs and explanations lay it out there. I personally use a low profile with a "very, very" slight RH twist mounted .63" from the bottom of the nock. My field tip arrows are stiff, bamboo and 33 inches long with a 29" draw with a 22% FOC and weigh in the 550 Gr weight range launched with my 48# self bow and track like a laser guided rocket. Where it goes is "all" up to me. Again a well done.
REB

Offline rebsr52339

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Re: parasitic drag
« Reply #7 on: February 12, 2019, 07:40:46 am »
Hat TSA, if you have the info tabulated etc, post it. Always like looking at interesting data. Maybe learn even more.
REB

Offline Scyth

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Re: parasitic drag
« Reply #8 on: February 12, 2019, 08:41:05 am »
Scyth, haven't heard such a well defined dissertation on "parasitic drag" sense I graduated from Aeronautical Engineering. Well done and in "simple layman's" terms. Seriously, drag is a complex part of an equation which effects different bodies in somewhat different ways. Your graphs and explanations lay it out there. I personally use a low profile with a "very, very" slight RH twist mounted .63" from the bottom of the nock. My field tip arrows are stiff, bamboo and 33 inches long with a 29" draw with a 22% FOC and weigh in the 550 Gr weight range launched with my 48# self bow and track like a laser guided rocket. Where it goes is "all" up to me. Again a well done.

. . . not my writing, but interesting nonetheless . . .

regards,

Scyth

« Last Edit: February 12, 2019, 08:52:25 am by Scyth »
"Retirement is not a word in the dictionary of craftsmen
and I will carry on my work a long as I can . . . "

- Yang Fuxi

Offline JEB

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Re: parasitic drag
« Reply #9 on: February 13, 2019, 06:52:28 am »
Sometimes we tend to over think things. I fletch an  arrow and shoot it. If it flies it stays in the quiver. My shots at deer and bear are 10 yards or  closer. The last bear I shot was at 7 yards. Not much space for a noticeable drag on the arrow.

Offline mullet

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Re: parasitic drag
« Reply #10 on: February 13, 2019, 04:22:40 pm »
I agree, Shot the only deer at Pappy's at 14 yards with a complete pass through. And, I couldn't count how many hogs at 3 to 10 yards and 3 Osceola turkeys. I'm not tryng to shoot game at long yardage. I got over that after giving up the Compound in '84. I worry more about hunting then shooting.

The research is impressive but not for me. I go to the woods and relax, been working for Engineers for 47 years.
Lakeland, Florida
 If you have to pull the trigger, is it really archery?

Offline rebsr52339

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Re: parasitic drag
« Reply #11 on: February 14, 2019, 09:40:40 am »
I heard that Eddie  ;D

Your right though, the last hog I shot was at 8 yards and a pass thru. Been a while thou. Getting back in it again.
Missed Hillbilly and JC coming over here this year to get their two apiece. Over run with those rascals. Later
REB

Offline mullet

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Re: parasitic drag
« Reply #12 on: February 14, 2019, 04:47:23 pm »
REB, this is Dick, right?
Lakeland, Florida
 If you have to pull the trigger, is it really archery?

Offline rebsr52339

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Re: parasitic drag
« Reply #13 on: February 14, 2019, 08:25:46 pm »
 YP ;D  ;D  ;D
REB

Offline Hawkdancer

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Re: parasitic drag
« Reply #14 on: February 15, 2019, 07:09:08 am »
Wow, Eddie!  47 year working with engineers?  You probably know what a slide rule is and how to work it! (lol) >:D!  I agree - woods time is for relaxing!  Scyth's info is interesting, though!  Got to get more range time to test some cuts.
Hawkdancer
Life is far too serious to be taken that way!
Jerry