peregrin falcons dive 200+mph,can my parkjet go faster?

[stuart]

hey gang ,i have been reading conversations going on regarding how fast a certain plane can fly as per its power,size,prop size and pitch.

i recorded using a v3 pitot sensor on a hobbyking parkjet that give the top speed of any given flight. it reads speeds of 9mph to 300mph. the reading after doing wot dives around the field from very high up was 162mph. a fellow pilot says its not possible to exceed the maximum pitch/rpm/battery power/watts... ect..ect... loosing me in his calculations... and friend of mine here at wattflyer get different calculations from different sights online.

me ....i'm a simple thinker,so heres my question followed up by the pkj setup i'm using.


if a peregin falcon is the fastest animal on the planet,it can dive over 200mph and has been measured by reputible folks like national geographics documentory.

the speed an item free falls is around 120mph[i think,correct me if i'm wrong. so this lil bird with superiour aerodynamic can dive faster than other birds and attacks it's prey in the air if it wants with this blinding speed of 200mph+. they even perfected the way to breath at these speeds as other birds can't.

back to the pkj,i was told my 162 is impossiblewhy is that,if i point her straight down at wot it should be sleaker in flight than a peregin who dives...right?


i have to get to the club meeting ,but throw this out here at wattflyer to learn from ya all.


hobbyking parkjet,
donsrc wicked 3000kv brushless motor
60amp turnigy plush esc[set to low timing]
4.1x4.1 emp speed prop
1600mah 30c skyblue hobbypartz 4cell lipo

these are the watts up meter readings:wot 3 second bench test

[stuart]

thought i'd add the picture of the parkjet for size and shape

[rcers]

Sure it is possible. Here is how I would do it. Take the motor off. Find a nice slope and wait for the wind to howl. Then toss it off.

The issue with the dive is the distance and attitude of the plane (keeping it straight down is tough). At that speed you would burn altitude very, very quickly. Hard to do for long.

Mike

[gramps2161]

I like to see the pull out at the bottom of the dive if there is a pull out.

[NJSwede]

The answer is "it depends". The terminal velocity depends on the drag coefficient. It could be a lot more than 120 mph.

The pitch speed would come to 14.8 * 3000 * 4.1 / 1056 = 172 mph. So, no, with that power system, you won't reach 200mph in level flight. However, it would be possible to get more in a dive. Although, in my opinion, probably not very likely. You'll have to pile on an even more ridiculous power system, I'm afraid...

[stuart]

njs,theres the calculations that start me wondering how the falcon goes over 200,but the parkjet won't under power. it just boggles the mind how beautiful the peregrines design is so efficient for speed.

i understand the level flight restrictions to max speed calculations....it's the dive speed i can't wrap my head around. so was the 162 wrong on the parkjets dive.




.Videos for peregrine falcon videos youtubeHigh-Velocity Falcon - YouTube
3 min - Dec 27, 2007
Uploaded by NationalGeographic
www.youtube.com/watch?v=j3mTPEuFcWk

[solentlife]

Stu .... have you read the story "Jonathan Livingstone Seagull" ? In that there is a good run on how the Seagull achieves his wish to go fast ...

The Peregrine uses sweep back in it's wings and tail to minimise it's surface area to drag ... it's an extremely streamline bird in any case, but in that dive becomes more a missile ...

Your PKJ cannot emulate that. We suffer not only drag but also parasitic drag created by the blunt motor / mounts and other appendages at back end of the PKJ ...

Example : Look at the back of a SUV or hatchback car after it's driven through mud ... the back window is smothered in crap. Why ? parasitic drag is one reason ...

You've actually touched on a subject that has been going through my mind .. is it possible to clean up the back end of a PKJ so it's more streamlined ... reducing drag etc. but without completely enclosing motor and suffering heat problems ?

[NJSwede]

Originally Posted by stuart

njs,theres the calculations that start me wondering how the falcon goes over 200,but the parkjet won't under power.

Because whoever designed the ParkJet isn't God and/or didn't have billions of years to test the design (pick whatever suits your belief system... )

Nature is just mind-boggling when it comes to the ingenuity of design.

How the falcon does it? It transforms from bird into missile when diving. Think about a dart being thrown off the Empire State Building (DON'T!). It has almost no drag, so gravity can accelerate it to very high speeds before drag kicks in and cancels out the gravity force.

Originally Posted by stuart

i understand the level flight restrictions to max speed calculations....it's the dive speed i can't wrap my head around. so was the 162 wrong on the parkjets dive.

No way to tell without a wind tunnel test. Terminal velocity is easy to calculate, but you need to know the drag coefficient, and that can only be determined in a wind tunnel. If I were to guess, I'd say it's not impossible. The ParkJet is a pretty streamlined design and has a very small "wet" area, so the terminal velocity should be high. And, given the theoretical pitch speed of 172 mph, it's totally possible that your power system brought it up to, say, 130mph and gravity did the rest in the dive.

What I need to do is to spend the final hour needed to get my ParkJet in the air. It's been sitting on my bench for months now, neglected due to other projects and too much going on in my life...