Archery Nation
Archery Nation
Archery Nation
Would you like to react to this message? Create an account in a few clicks or log in to continue.



 
HomeGalleryLatest imagesSearchRegisterLog in
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing Archerynation-2-1
Like Us
Order your Fobs here
Photobucket
Who is online?
In total there are 3 users online :: 0 Registered, 0 Hidden and 3 Guests

None

Most users ever online was 190 on Fri Apr 09, 2021 6:11 am
Navigation
 Portal
 Index
 Memberlist
 Profile
 FAQ
 Search
Latest topics
» My Hoyt AlphaMax 32
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptySun Feb 03, 2019 11:05 am by bigbuck150

» FOB's and NAP Apache
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptySat Oct 25, 2014 11:09 pm by dano

» noob
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptySat Oct 25, 2014 10:53 pm by dano

» Why?
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyWed Jan 22, 2014 12:08 am by tradermike69

» New Guy from Missouri
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyMon Jan 20, 2014 3:16 pm by tradermike69

» New Wanna Be Here
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyMon Jan 20, 2014 12:02 am by tradermike69

» Flu Flu Arrows with a compound bow
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptySun Dec 08, 2013 12:53 pm by oldmanontheriver

» i need help, with fobs not mentaly
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyFri Mar 15, 2013 10:19 am by Norwegian Woods

» New member from Norway
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyFri Mar 15, 2013 10:07 am by Norwegian Woods

» QAD Rest set up
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyThu Feb 07, 2013 8:31 pm by grumpy413

» New to fobs.
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptySun Feb 03, 2013 7:36 pm by Plrosey33

» How much will the extra weight affect arrow spine?
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptySat Dec 22, 2012 11:15 pm by Stykbow1

Loading...
Search
 
 

Display results as :
 
Rechercher Advanced Search
March 2024
MonTueWedThuFriSatSun
    123
45678910
11121314151617
18192021222324
25262728293031
CalendarCalendar

 

 HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing

Go down 
AuthorMessage
Paul Morris
Admin
Paul Morris


Posts : 42
Points : 64
Join date : 2011-01-05
Age : 63
Location : Arizona

HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing Empty
PostSubject: HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing   HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing EmptyThu Jan 06, 2011 7:46 pm

My background is Mechanical Engineering. I had spent the better part of 12 years working at a rocket ranch (Hughes Missile Systems). I am also lucky enough to say I have not missed an archery Elk hunt in 28 years. I am even luckier to say it has been with the same group of friends. My thoughts regarding bodies in motion come from crunching the numbers. My thoughts regarding arrow flight comes from hunting and the frustration of getting a broadhead to fly. So in a nut shell.....I am a "hillbilly" engineer and proud of it.

The 3 basic principals to the flight of the FOB are; drag, spin and lift. For my thoughts on spin and drag please see thread https://archerynation.forumotion.com/t32-spin-and-drag

Lift
As we all know, the top of an airplane wing has more surface area than the bottom. The air that travels under the wing has pretty much a straight shot to the back while the air that travels over the top has a longer way to go. Both the air on the top and bottom has to meet at the back of the wing at the same time so the air on the top of the wing is forced to go faster than the air on the bottom. Based on the laws of fluid dynamics, the faster a fluid is moving the lower the pressure. So the top of the wing has a lower pressure and creates lift.

The FOB lift is a different animal all together, but it does follow the laws of fluid dynamics. The air that enters the FOB is funneled through the ring wing, hits the fins like a fletch (causing rotation) but also induces circumferential lift (360 degree lift) the ring wing acts like an airplane wing even though it is not shaped like a conventional wing. This is caused by the fact that the air traveling inside the FOB is going slower than the air traveling outside the ring wing. This pressure differential causes the lift (true lift created by pressure). So in effect, the FOB is trying to pull itself apart. It is basically an air gyro. It does not lift the back of the arrow. It provides as much lift up as it does down and side to side. All we have done is taken the drag component (momentum transfer of the air hitting the fins) and used it for good. This effect is substantial and greatly reduces the oscillation of the arrow = more KE downrange.

If you look carefully at the fin structure you will see that the fin is a double back wedge shaped. The volume of the internal structure of the FOB is therefore reduced as you move through the FOB causing the compression. A closer look at the fin structure will reveal that the last 1/4 of the fin profiles back to a sharp edge, basically a reverse wedge. This is where the decompression takes place. This structure is a kind of Ventura as the fins are wedge shaped but angle back to a sharp trailing edge. So the volume decreases and then opens back up. We found that this decompression induced a greater torque (spin) without having to increase to angle of the wedge thus keeping drag at a minimum. The fact that the air is being compressed does take energy, however, the fact that the air increases in mass makes the air contacting the fin more efficient. Heavier air has more bang for the buck causing a higher torque for a quick spin up. Not faster spin, just getting up to terminal spin quicker.

It is the Lift that makes the FOB work. That is how we get so much bang for the buck out of something that is only 1/2 inch long. This is also why some folks think the FOBs make more noise. But that is for another thread all together!

Well…..Those are my thoughts of how a FOB works from a proud “hillbilly” engineer.

Best regards

Back to top Go down
http://www.starrflight.com
 
HOW THE FOB WORKS- Lift- Something never applied to arrow flight-It’s all in the ring wing
Back to top 
Page 1 of 1
 Similar topics
-
» Broadhead flight issue???
» Which rest works best?
» Arrow velocities
» My arrow sling
» How much will the extra weight affect arrow spine?

Permissions in this forum:You cannot reply to topics in this forum
Archery Nation  :: Nuts and Bolts of Arrow Flight-
Jump to: