Frictionless barrel coating

General Discussion
pime3
rookie
Joined: 07 Mar 2016, 15:25

19 Sep 2017, 15:39 #21

Hello Hilltopwoodsman


Sorry for my long delay to answer.
Thanks for your good news.
Your reached distances 450-475 is amazing.

You are not far from the record.!

I have a lot of questions.
Will you give us some technical details about your materials?
Pipe long, caliber
Darts weigth,  shaft diameter, long
Propeler cone, commercialized or home made.?

By what mean do you measure or evaluate  your breath (pressure, flow, remain breath duration 0. 10s during your shoots. ?

For long flying times,  effect   of wind can be very noticeable.

So in case of reach the  record,  the direction and value of wind should be described, IMO.
I don't remember if Japonese described the wind conditions rigourously.


Sorry for my curiosity,  but it's for the good cause ☺

Perhaps if you give us some details , I could have some constructives suggestions.


PIME
 
Last edited by pime3 on 25 Sep 2017, 11:58, edited 1 time in total.
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Hilltopwoodsman
novice
Joined: 14 Mar 2016, 04:46

23 Sep 2017, 10:56 #22

Ok so here's more specifics about barrels and darts etc . For the farthest shots specifically,as I have other Barrels, I use an 8 foot  tedlon or oil lubed aluminum blowgun that's between .55 and .56 caliber . (I'm 6'3" tall so lung capacity and tube volume match well. ) I'm going by about 300 cubic inches of useable air in the lungs which is about average for my height according to common charts . The 1/10th of a second breath release is a common test done using a peak flow meter or special types of spirometers . And it is pretty common for most average persons to expel most of their useable air in that time . As I said before most people's actual lung capacity stays relative the same it's how much psi one can blow it out with that helps. Moving forward , darts are 3.5-4 gram nails with and made cone from plastic weather sheeting/ tarp sold by the foot at most hardware stores . Two to three wraps make a sturdy cone so it's not too thin but not too stiff either . Look for the black plastic it usually comes in one thickness. I've also tried abdominal/wasp style bodies made from enamel coated "rigid" foam (shaped to fit in the bore)with fletching behind it. Just like DavidCook and Sphingids posts . Other combinations for the same lung capacity but heavier darts include classic arrow carbon shafts 16" -32" inches long with foam sabot and classic fletching made from colored tape . Or cone as above with fletching also. They weigh about 20-30 grams and hit maximum range of 300-350 feet and are shot from a 5.5 foot 64 caliber aluminum pipe. And finally wind: I've seen in all the distance videos lights darts shot in a hot desert climate directly into the heavy wind . I've never done this . I'm not even sure how far my darts would fly if I had wind flags and waited for strong wind and then shot exactly with the wind behind the dart . That could push me easily into the 500 foot range. I also have shot the farthest with a very strong magnet holding the dart at the bore . It seems to add pressure build up before the whole flow of air takes the dart with it . I haven't been even able to find a one piece pipe that doesn't bend over eight feet otherwise I would try 10 foot .55 caliber for better record . How all that answers some of those questions for you and others ! Also read my other posts in other topic about long range shooting . More specifics there also .
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pime3
rookie
Joined: 07 Mar 2016, 15:25

25 Sep 2017, 11:04 #23

Hello Hilltopwoodsman
Thanks for your additionnal details .
"Bravo ! " to  persevere with long shoot distances and your methodological approach.
To reach 556 feet , a nozzle speed of 60 to 65 m/s is at least necessary with inclinaison 41 to 42 degrees because of Fd ( drag force during fly ).
 Your peak flow is probably (1)  high enough to reach 65 m/s with a pipe of caliber 14mm ( and lightweigth darts )
The weigth of darts must not be too high for reaching  the necessary nozzle  speed in accordance with your breath  and the Cd of dart must not be too high.
with propeller cone, Cd is about 0.3 in best case.
the external balistic taking into account Cd shows  that the weigth of dart must be >5grammes to reach 556 feet with 65m/s initial speed and a Cd=0.3.
But with >5g   , I think very difficult to reach such a nozzle speed.
ie .
I  performed,  and verified,  by measuring simultaneously  blowing pressure and nozzle speed , on cobayes and using  my blowing machine  ,  a theorytical model for internal balistic, taking into account  pneumatic losses, that shows  difficulties  for a human to reach the necessary breath pressure (2) and  nozzle speed with a dart weigth > 5g into your 55cal,  8feet long.

A chronograph should be very usefull to help you in your tests  and to verify you can reach =>60m/s with your darts and determine the max weigth .
Perhaps you should also adopt a smaller caliber to reach the necessary speed with of course a ligthweigth dart.

I made a lot of calculus by changing the different parameters
 I conclude  that the best way is to shoot  a very low Cd (<=0.15)  dart and to  retry fletching darts moved by lightweigth  sabots  in order to shoot lightweigth darts( <2g?)  that will permit to accelerate the speed at about =>60m/s with your .55cal 8feet long.
8 feet long is a max because pressure losses along this long  pipe.
In simulation ,there is a low gain of nozzle speed ,1%, changing 7feet to 8 feet pipe long and  for a 2g weigth dart.

Note (1) according statistic pneumology tables  with your tall and supposing you are 30-40 years old ? for man max peak flow.
Note(2)  more than  a mean pressure of  2psi (or 140mbar , already a high pressure value ) during the shoot, and for heavy darts (> 2g with .55 , 8feet).
 see an exemple of real pressure record ( year 2007 ) of Jeff BOULMIER , a famous shooter in cal04 during competition at 10m ( several world records ).
http://fssa.fr/photo/blow_pressure_jeff.jpg
And another record of Stephane JOUANNEAU , during tests of max power shootings ( max near 3 psi )!
http://fssa.fr/photo/resultats_stjo_serie5.jpg

if this can be usefull , this is pictures of my home made very lightweigth  fletching darts I published on FSSA.fr 
I just look for a long flat aera to test my very  low Cd darts or a candidat to try them Image

http://fssa.fr/photo/empennage_et_propu ... me_vga.jpg

http://fssa.fr/photo/darts_a_empennage_ ... ga_jpg.jpg


Good tests

pime






 
Last edited by pime3 on 05 Oct 2017, 09:20, edited 18 times in total.
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neondog
Addicted
Joined: 08 Jan 2009, 19:30

29 Sep 2017, 12:12 #24

I'm pretty sure that when Pime says "very little CD dart" he means a dart with a low drag coefficient. Thus the recommended return to fletched darts propelled by a light weight sabot.
United States Blowgun Associationusblowgun.com
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Hilltopwoodsman
novice
Joined: 14 Mar 2016, 04:46

05 Oct 2017, 13:28 #25

Yes Neondog I believe you're right , low drag . Thank you Pime for those numbers ..really very interesting . I will be trying your recommendations; lighter dart and sabot style shot . It's interesting that a bit over 200 fps will set that distance and I have yet to try shooting with wind behind the light dart . In the record video from Japan the man uses what appears to be wire shafts and that collapsible fletching but the dart seems short enough that he doesn't need extra weight toward the front of the dart for more stable flight. By the way, what kind of foam do you use for the sabot ? My rigid foam and other foams I've used fall apart , yours looks very sturdy but lightweight ....
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calina
novice
Joined: 02 Apr 2012, 07:41

06 Oct 2017, 05:07 #26

I read Pime's description on the French site (FSSA.fr) and he is cutting his plugs himself, on the other hand they look pretty much like these common closed cell ear plugs, if these are of a useful diameter to you.

https://www.mdsassociates.com/catalog/p ... d-earplugs
.
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pime3
rookie
Joined: 07 Mar 2016, 15:25

06 Oct 2017, 10:44 #27

Hilltopwoodsman wrote: Yes Neondog I believe you're right , low drag . Thank you Pime for those numbers ..really very interesting . I will be trying your recommendations; lighter dart and sabot style shot . It's interesting that a bit over 200 fps will set that distance and I have yet to try shooting with wind behind the light dart . In the record video from Japan the man uses what appears to be wire shafts and that collapsible fletching but the dart seems short enough that he doesn't need extra weight toward the front of the dart for more stable flight. By the way, what kind of foam do you use for the sabot ? My rigid foam and other foams I've used fall apart , yours looks very sturdy but lightweight ....
I use foam used in the swimming pools , see https://www.decathlon.fr/frite-en-mouss ... 16134.html

To cut the foam , it is essential to make specific tools in order to obtain directly the diameter with " clear tolerance "
see my method http://fssa.fr/photo/pime_s_tools_for_p ... am_vga.jpg

The sabot must slide into the pipe with a dry friction smaller than 3_4 grammes.
The length of sabot must be between 1.5 _2 diameter ( cal ) 
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