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Old Mar 30, 2012, 11:29 AM
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United States, LA, Shreveport
Joined Jun 2011
331 Posts
we need to get the owner of this thread (boxhead) to put links on the first post to pages with good notes.....this is a really fun plane when setup right
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Old Mar 30, 2012, 11:35 AM
Free as a bird now.
Brian Courtice's Avatar
United States, FL, Punta Gorda
Joined May 2002
6,576 Posts
I balance my PJ a few mm forward of the center of the finger holes. Would that be about right for bungee or rail launching?

Another point I haven't seen discussed is the location of the tow hook on the bottom of the plane. It's been my experience that a forward placement produces a lower trajectory but more stable launch, and that moving the hook back produces higher, but less stable launches. Where is the sweet spot for the PJ?

So far, I've had lots of good side arm hand launches like I showed in my video a few pages back, but I might like to give a bungee setup a try,
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Old Mar 30, 2012, 12:16 PM
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amba's Avatar
Joined Feb 2011
177 Posts
First successful flight, at last :)

After numerous ill-fated attempts (described earlier in this thread), today I finally managed to actually fly her wasn't simple, but lots of fun.

The last set of changes that made the difference were:
1. All launch attempts were done over a soft-grass field... in previous times I did not think this was important. But as I learned to today it is. It took me 4-5 attempts to get the hand-launch right. All futile attempts ended in the soft grass and I was immediately ready to try again. If this was done over hard surface, I'd be sitting repairing the PJ now instead of writing about how successful the flights were.
2. Motor and battery changed to lighter versions: 40g motor + 50g battery (instead of 60+120 previously)
3. Setting a 'hand launch' mode in my TX, where elevator is about 10 degrees up in the 'neutral' stick position. this was probably this second most important change I made. Launch attempts with no 'up' bias looked far worse than with this mode.
4. Propeller: 5x3 APC

That basically did it. Of course once it got in the air I became nervous as hell, the thing was not trimmed at all, and, it was (is) much faster and nimble than anything I had flown so far. I has to keep my right hand fingers on the stick (mode 2) and use my left hand to trim.
This was all done at 1/2 throttle, and still felt pretty darn fast.

In the coming few flights I hope to get used to it and be able to go faster. I didn't dare go higher than 2/3rds throttle today.


HobbyKing ParkJet, right after a successful test flight by Amit B, on Flickr
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Old Mar 30, 2012, 12:43 PM
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United States, LA, Shreveport
Joined Jun 2011
331 Posts
Yes Brian, Cog is Cog, same Cog if you dropped the parkjet off the side of a building for launching and your location sounds about right.
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Old Mar 30, 2012, 01:42 PM
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Finlande
Joined Dec 2007
422 Posts
I am really surprised guys you all seem to experience so much troubles launching this plane .
Mine is probably the easiest in my fleet to handlaunch .

I believe the secret is to gently toss the plane and avoid any javelin throw that will roll it on the left and dart it in the mud .

My technic is so :

On 3 cells , full throttle ( 250 W ) and a gentle straight toss with left hand even if I am right handed .

On 4 cells , 2/3- 3/4 throttle, ( far over 300 W ) ,just enough to feel the plane wants to leave the hand and the same gentle toss .

That way, my Parkjet just leaves my hand straight with absolute zero torque
I believe guys you may throw too hard and you get a twist at the end of your right hand course .

I darted in the dirt my 1400 W Funjet at launch almost every time till I learned that technic and I never missed a launch after that and torque effect alone isn't enough to roll the plane . I was most of the "torque" by throwing with my right hand

I got an 100 % handlaunches successes since I started to learn that new technic two years ago .

I know it's frigthening to launch left hand the first times but it is still much safer and most of all , if you screw it , your right hand is immediately ready to correct .

I just hope guys you get this little beast in the air cause it's a real blast to fly !!

185 km/h today on 4 cells with my best battery today . I think I am not ready for more yet cause it feels that I got a missile at the end of the line .
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Last edited by Jpette; Mar 30, 2012 at 01:51 PM.
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Old Mar 31, 2012, 08:54 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,380 Posts
Hoe to be home this week to put into practice all the chat ... beeen a long frustrating assigment !

Will report back what happens.
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Old Mar 31, 2012, 09:37 PM
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Australia, New South Wales, Sydney
Joined Jan 2011
109 Posts
video of hand launch

someone asked me to post a video of my hand launch technique a while back. Here's a couple from this morning, one good, one not good.

parky hand launch (1 min 4 sec)


enjoy.
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Old Apr 01, 2012, 12:07 AM
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Finlande
Joined Dec 2007
422 Posts
This is a very good illustration of my previous point :

We clearly see that by launching left hand , the twist in the wrist at the end of the throw is opposite and the plane rolls on the right . That is because you threw too hard like a javelin .

You need to toss it gently and it will leave straight .

Better throw it very slightly up but in no way like you did almost straight up .

In that video guys , there was no torque effect visible at all, just a roll on the right induced by a too hard throw with left hand .

When you throw it that hard with the right hand, you just get the same roll induced by the twist given by your thumb lower than other fingers and plane roll on the left , add a little touch of torque , plus a too steep up angle and you are straight in the dirt .
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Old Apr 01, 2012, 07:27 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,380 Posts
I haven't actually launched my PKJ myself yet ! I've always had a helper do it.

I launch all my others ... edf ... cessna etc. - but not Parkie !

the blo*** thing scares me to be honest even after all these years of flying !
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Old Apr 01, 2012, 10:37 AM
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Finlande
Joined Dec 2007
422 Posts
That's too bad man cause this is such a nice plane .

I just went flying today and I almost flew only this Parkjet . I had such a blast with it no matter if I put 3 or 4 cells .

To be really honest, I noticed today for the first times a very slight torque effect but nothing to worry about .

I actually launched by mistake just like Robinson did on that video , with too much force almost staight up . Fortunately, the plane which had almost stopped in the air had enough power on 4 cells to start climbing almost straight up .

I had more than 20 flights during this week-end experimenting with my eagle tree pitot tube used in stand alone which mean that all I get is the max recorded speed .

My motor is :

http://www.giantcod.co.uk/2217-2700k...-p-402979.html

With a 40A mystery ESC

My best recorded speed with APC 4,75x4,75 :

3S-Rhino-1050-30C : 162 km/h : 247W
3S Rhino -1550-30C : 169 km/h

4S Turnigy 1000-30C : 178 km/h : 380 W
4S nano-tech 1300-45C : 186 km/h


My recorded speed vary only 1-3 km from thoses max values.

Speed difference isn't that big between 3 or 4 cells :

Added power is hitting a "wall" because of the excess drag at thoses speeds .

I agree with you Solentlife that I could convert some of this power in speed by increasing the pitch . I"ll give it a try next time with a 4,75 x5,5 but my Turnigy packs won't cope wit it cause they already got pretty warm .

Let's go back flying guys cause this is such a fun plane !!
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Last edited by Jpette; Apr 01, 2012 at 10:43 AM.
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Old Apr 01, 2012, 01:51 PM
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Joined Feb 2012
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Is this plane good enough for a nanotech 1300mah 3cell battery with the hextronik 24gram 3000kv motor and 30 amp plush? Or is this battery to heavy or big?
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Old Apr 01, 2012, 02:07 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,713 Posts
Quote:
Originally Posted by Rabbern View Post
Is this plane good enough for a nanotech 1300mah 3cell battery with the hextronik 24gram 3000kv motor and 30 amp plush? Or is this battery to heavy or big?
Most likely be nose heavy and you be able to get the back far enough, I had a 26 gram motor in mine to start with and t balanced ok with rhino 750 3s.
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Old Apr 01, 2012, 02:20 PM
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Joined Feb 2012
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Oki then i will go for 1000mah's
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Old Apr 01, 2012, 05:21 PM
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Joined Mar 2012
78 Posts
i had hoped to fly my pkj#1 this afternoon but the winds p/u and all other pilots left. the club rules forbid flying alone. i didn't bring the launcher since i was late getting to the field and had wanted someone to toss it so i could trim it out before testing the bungee launcher. i now have a feeling the launcher is a waste of time and i should toss the pkj with the wing grip left handed[i'm right handed],at 3/4 throttle at a fairly steep upward angle with a arm sweeping motion and a step forward at the same time i will control the tx right handed.if the guys on flitetest videos can launch the stock pkj,we should be able to launch our more powerful birds ....aaaaarrrrrggggg ,i don't want the hassel of bungee launching.... if i find it hand launchable and already built the thing. it'll be for sale...lol.
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Old Apr 01, 2012, 06:30 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,713 Posts
Quote:
Originally Posted by tobydogs View Post
i had hoped to fly my pkj#1 this afternoon but the winds p/u and all other pilots left. the club rules forbid flying alone. i didn't bring the launcher since i was late getting to the field and had wanted someone to toss it so i could trim it out before testing the bungee launcher. i now have a feeling the launcher is a waste of time and i should toss the pkj with the wing grip left handed[i'm right handed],at 3/4 throttle at a fairly steep upward angle with a arm sweeping motion and a step forward at the same time i will control the tx right handed.if the guys on flitetest videos can launch the stock pkj,we should be able to launch our more powerful birds ....aaaaarrrrrggggg ,i don't want the hassel of bungee launching.... if i find it hand launchable and already built the thing. it'll be for sale...lol.
Pretty tough rules not being able to fly alone lol, I wonder why ?. Often I am the first and sometimes only person on the field and I love flying alone. I tend to land if any of the ic guys taxi out to take off.
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