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Old Feb 19, 2013, 07:21 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
I've just gotten off the phone with a mate that says they dopplered his radjet on sunday doing 306km/h
he runs NTM 2836 3000kv on 4s and 4.5x5.1 prop.I'll ask him to record a vid and post it on here so we can compare,but that's crazy if it's true!
here's the motor
http://www.hobbyking.com/hobbyking/s...00KV_755W.html
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Old Feb 19, 2013, 10:56 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,489 Posts
Until we can check .... my spreadsheet gives a likely speed of about 250kph ...

It's not unusual for claims to be made of the highest figure shown by Doppler. But many I have dopplered - the real speed is much lower. Some speeds are incorrectly determined because of short run, turn in the run causing a greater doppler shift, change in throttle etc. There are many reasons that speed can be mistakenly displayed.

It is one of the reasons I like my V3 speed checker to verify my Doppler runs.

Nigel
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Old Feb 19, 2013, 01:39 PM
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ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts
Jayman72 , I am running a 4.75 x 4.75 prop.
.I love your canopy Pin and hole mod, I will be stealing that idea.
I have a 3s 900 mah coming in the post wonder if the 20 amp esc will take it?
Today I had another bluesky lunchtime flight, this time I was exploring the slow speed handling of the parkjet. Its great, I was flying with enough height for a stall recovery , gettingsslower and slower until she was just crawling along on 1/4 throttle and nearly full up elevon! It did bite eventually but was provoked with a left turn. It really is a great plane. Fast and slow . I absolutely love it. Oh yeah a group of kids in the park stopped and watched for a bit and all I could hear were words like ' that's cool man. '
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Old Feb 19, 2013, 03:20 PM
Note to self, put on pants.
Jayman72's Avatar
Australia, VIC, Frankston
Joined Mar 2012
89 Posts
Quote:
Originally Posted by ledzep76 View Post
Jayman72 , I am running a 4.75 x 4.75 prop.
.I love your canopy Pin and hole mod, I will be stealing that idea.
I have a 3s 900 mah coming in the post wonder if the 20 amp esc will take it?
Today I had another bluesky lunchtime flight, this time I was exploring the slow speed handling of the parkjet. Its great, I was flying with enough height for a stall recovery , gettingsslower and slower until she was just crawling along on 1/4 throttle and nearly full up elevon! It did bite eventually but was provoked with a left turn. It really is a great plane. Fast and slow . I absolutely love it. Oh yeah a group of kids in the park stopped and watched for a bit and all I could hear were words like ' that's cool man. '
Zep might be a bit touch and go on the 20A esc. If in doubt swap it out. You should have a bit of headroom for safety. You dont want to loose a plane for the wrong reasons. Get yourself a wattmeter. There perfect for this. I want to keep my parkjet close to stock for great slow speed flying also. Got enough fast stuff already. Almost finishing the Adrenalin Rush Balsa hotliner. Fast planes are great but if it has to come in hot for every landing that can get a bit anoying.
Jamie
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Old Feb 19, 2013, 07:59 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,489 Posts
Quote:
Originally Posted by ledzep76 View Post
Jayman72 , I am running a 4.75 x 4.75 prop.
.I love your canopy Pin and hole mod, I will be stealing that idea.
If you go way way back in threads - you will find others who have used pins in canopy .. double magnets .... nylon wing bolt ... allsorts.
My preferred method now is a wing bolt either side of mid section of canopy down through fueslage to bilnd nuts in bottom. This makes sure canopy locks into position, stiffens up the fuselage, can never fly-off when in the air and at speeds that rip away magnet held jobs !

Quote:
I have a 3s 900 mah coming in the post wonder if the 20 amp esc will take it?
My advice to anyone with these PKJ ... up to a 50A ESC anyway whatever you do. The standard Hobby King and Mystery 50A is cheap enough and it will cover near all power set-ups apart from the real hot ones without problem.

Quote:
Today I had another bluesky lunchtime flight, this time I was exploring the slow speed handling of the parkjet. Its great, I was flying with enough height for a stall recovery , gettingsslower and slower until she was just crawling along on 1/4 throttle and nearly full up elevon! It did bite eventually but was provoked with a left turn. It really is a great plane. Fast and slow . I absolutely love it. Oh yeah a group of kids in the park stopped and watched for a bit and all I could hear were words like ' that's cool man. '
Believe it or not - even a heavy PKJ will slow down remarkably ... the main point to watch is that you install everything evenly balanced not only longitudinally but across as well. Checking transverse balance is recc'd ... and if found not equal - you can correct by use of a nail or similar pushed into wing tip on light side ...

Nigel
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Old Feb 20, 2013, 03:18 PM
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ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts
I just dopplered my crappy video!
Results are :-
66 mph 65 mph 64 mph 62 mph into wind.
82 mph and 84 downwind.
So I reckon a consitant 10 mph wind speed.
Average Airspeed of 74 mph or 119 kph.
I used rcspeedo on an andriod phone. It is difficult to tell how accurate it is but the fact that the first three result were dropping by 2 mph per run would make sense as the battery voltage would be dropping.
My goal is 100mph on a 2cell.
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Old Feb 20, 2013, 09:00 PM
Gravity sucks.
Australia, QLD, Toowoomba
Joined Mar 2011
563 Posts
Quote:
Originally Posted by ledzep76 View Post
I just dopplered my crappy video!
Results are :-
66 mph 65 mph 64 mph 62 mph into wind.
82 mph and 84 downwind.
So I reckon a consitant 10 mph wind speed.
Average Airspeed of 74 mph or 119 kph.
I used rcspeedo on an andriod phone. It is difficult to tell how accurate it is but the fact that the first three result were dropping by 2 mph per run would make sense as the battery voltage would be dropping.
My goal is 100mph on a 2cell.
If you're limiting yourself to 7.4 volts, the only way to get more speed (power) is to increase your amps and or your efficiency.
I'm sure you knew this already though - certainly an interesting challenge.
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Old Feb 21, 2013, 11:39 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,489 Posts
Speed = Prop PITCH with RPM ......

Simple.
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Old Feb 24, 2013, 11:50 PM
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sonnydc's Avatar
Joined Dec 2011
134 Posts
Heres a video of the 2700kv motor with a 4.75 x 4.75 and 3s 1800mah 40c battery in action. You can have a better view if you watch it in high definition.

EPO Parkjet Mk-II with 2700kv Motor (3 min 2 sec)
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Last edited by sonnydc; Feb 25, 2013 at 01:44 AM.
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Old Feb 25, 2013, 01:15 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
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Quote:
Originally Posted by sonnydc View Post
Heres a video of the 2700kv motor with a 4.75 x 4.75 and 3s 1800mah 40c battery in action. You can have a better view if you watch it in high definition. ......................
131 kph and then near end speed is dropping to 120 ... 116 ... 115kph ...

This is very good on a 2700 ... and matches stock Mk 2 on 3000kv.

Nigel
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Old Feb 25, 2013, 01:19 AM
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sonnydc's Avatar
Joined Dec 2011
134 Posts
I tried using a 6x4 apc clone but my parkjet keeps on digging to the ground upon launch.
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Old Feb 25, 2013, 01:24 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,489 Posts
Quote:
Originally Posted by sonnydc View Post
I tried using a 6x4 apc clone but my parkjet keeps on digging to the ground upon launch.
There's no way to get a 6" to launch properly ... the PKJ has a short wingspan and needs speed to steady it ... so any torque on launch is hard to counter. As you go up in diameter you are increasing the flywheel effect ---- torque.

Anyway a 4"pitch is going down and all you would do here is reduce amps on motor but stay with literally similar overall speed if lucky.

If you can suffer the amps ... go for a 5x5 ... you'll probably hit 140 - 150kph then.

Even at 130+ ... it's still an adrenaline rush ...

Great

Nigel
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Old Feb 25, 2013, 01:41 AM
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sonnydc's Avatar
Joined Dec 2011
134 Posts
Thanks Nigel

Now I need to find a new place to fly. The housing project had already started in this area and the available space would be cut in half. Not good for speed flights.
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Old Feb 26, 2013, 01:58 PM
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ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts
Stefan Pointner mit Funjet Ultra die zweite, jetzt aber richtig ! 300 + km/h (2 min 43 sec)

I know its not a parkjet but Oh boy does this thing shift.
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Old Mar 14, 2013, 07:36 PM
Registered User
United States, KS, Potwin
Joined Mar 2012
37 Posts
We are still waiting for the PJ-Twin....
Come on Nigel, get it in the air.
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