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Old Mar 12, 2012, 05:38 AM
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Finlande
Joined Dec 2007
422 Posts
Too bad cause with the motor mount aligned with the wing you wouldn't have any handlaunches problems .
My setup is with a 70g motor and battery weight doesn't matter at all !!

I can fly either with a light Rhino 3S-1050 at 100g or a Nano-tech-4S-1300 at 155g and honestly , weight doesn't affect at all the launches .

Solentlife

I finally got to fly again that small monster which is crazily fast . With the 4S-1300-45C pack and over 400W on my 2700 kV motor and a 4,75x4,75 prop , I estimate my speed in the 200 km/h range .

Unfortunately, my pitot tube got stuck in the propeller and was destroyed pretty badly ,so now that I finally get to fly the plane , all I can do is estimate roughly my speed .

I am not sure I really want more speed cause it is already crazy enough like that.
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Old Mar 12, 2012, 01:30 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,566 Posts
I still think that most of the problems of launch are not line of motor - but pure torque.
The PKJ has a short wingspan, but wide chord. This means that until wing flies - it torque rolls very easily.

I'm running 5x5 prop at very high rpm - the model is torquing opposite to the prop. This I consider is most peoples problem as well - reducing prop size is a help and why I've cropped my 5x5 to 4.6 x 5 ... also what's needed is to learn the technique for each PKJ ...

I too can carry various batterys ...
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Old Mar 12, 2012, 01:51 PM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Guys I say this again.all models like thiis will have a torque effect on launch
its not the mount.all that is needed is slight and i mean very slight right aileron upon launch,too counteract the torque effect and you have a nice smooth launch I've had no issue with torque roll and plunges on launch....maybe i should've shared this tip long ago or maybe i did can't remember but thats the answer too the launch
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Last edited by chop stiX; Mar 13, 2012 at 01:23 AM.
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Old Mar 12, 2012, 02:35 PM
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Finlande
Joined Dec 2007
422 Posts
I think that 80% of what we believe as the torque left roll comes from a bad launching technic .

If you throw right hand, your thumb finishes it's course lower than other fingers like when you throw hard a ball and this creates the so called " torque" .

My "Torque" problems with my 1200 W Funjet finished after I started to launch left hand .
With left hand, as we are not used to throw anything with it, all we can do is a gentle toss and fingers finishes their course level and "torque" is gone .

I never missed a handlaunch after I started the left hand technic and torque , especially with this parkjet doesn't exist at all , at least with a 4,75 inches prop , no matter how hard I hit the throttle .

I know you don't believe me guys but you are creating yourself the "torque" .

Just give it a try and you"ll see by yourself .
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Old Mar 12, 2012, 03:27 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,566 Posts
I think it becomes a combination of many things. No one thing being the whole answer.

I have a great launcher in my group - as he learnt on his overpowered Skyfun .... but he's not always there.
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Old Mar 12, 2012, 09:02 PM
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Joined Aug 2005
412 Posts
sadly my pj mk2 (stock motor) is becoming weak. looks like i have to upgrade my motor to a faster one. anybody know which motor is good for a drop in replacement (not the stock one again) from hobbyking?

i was hoping to keep the stock mk2 esc as well if i could have it that way. my batts are all 800mah and gives me 7 min flights with the stock electronics. anybody got a link? cheers
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Old Mar 13, 2012, 12:21 AM
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Australia, New South Wales, Sydney
Joined Jan 2011
115 Posts
finally getting my Mk III parkjet in the air

Thought I'd share my first good flights with my MkIII PKJ:

Parkjet MkIII - first good flights and crashes (6 min 49 sec)


I spent quite a bit of time building this up only to have a number of launch fails beating the crap out of it until I realised the thrust angle was pushing it nose in. Live and learn. So its a bit beat up now but I've got it flying nicely and will try with a bigger 3S soon. If it lasts! Its bags of fun just as it is though.

Turnigy 2836-3400
Turnigy Trust 45A
Turnigy nanotech 1000mah 25-50C 3S
HK stick mount.
prop 5.5x4.5 (I think, it doesn't say)

One thing I did to stiffen and strengthen the fuse was to lay a bed of gyprock weave and epoxy down on the inside fuse bed. It kind of blocks the air intake (or should I say dirt intake) but that's not a problem. I did the same with the control surfaces to stiffen them. This has saved the airframe a ton of times already. In the above vid you see me sail the plane nose-in to a mesh fence - it just bounced off no worse (than it already was) for wear. I also use glass fiber tape a lot!

In my view this bird is way over weight with my current setup (which is nabbed from the rcfoamfighter dudes on the tube) AUW is around 480gm. I really don't know how you guys get your birds launched with the bigger systems you are wedging in but more power to you!
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Old Mar 13, 2012, 01:17 AM
ExPat
Aero Andy's Avatar
Spain, Murcia, Mazarrón
Joined Apr 2010
1,600 Posts
Hi Graeme

Nice video and great location to fly in, and love the way you bounced it off the fence. Thanks for posting the vid.
Andy
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Old Mar 13, 2012, 03:29 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,566 Posts
Nice one Graeme .... only bit missing is seeing the actual launch technique -as you seem to have it sussed.

It annoys me that I can launch my Cessna, T45 EDF ..... near anything except this baby.

2 things I have found, a) it is extremely sensitive to CoG, b) the airframe vs wing span is way out in the torque roll field.... I'm sure a longer span would cure most of the ills. But then you'd increase drag and compressability .... yes I include Compressability, something usually reserved for supersonic aircraft and reason for swept wings etc. We are pushing these baby's to speeds that make the mind boggle, the airframe design is an all-lift design including the central fuselage, meaning short span wing.

Once I get back from this assignment - about 2 weeks, I shall be trying out the small props and building speed / thrust back up to my record breaking 5x5.

Even with the short 25-30ft or so on last outing till it torqued / dived in.... the V3 Pitot recorded 74kph straight out of launch ! That just shows how much power is being pushed through this small airframe and that was only half throttle.

Unfortunately as it's only end of winter in Latvia, fields and grass are bare, hard frozen and totally unsuitable for glide tests to get best launch technique. In summer - it's easy to find a "soft" long grass area to test glide. But I cannot wait that long.
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Old Mar 13, 2012, 06:02 AM
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Finlande
Joined Dec 2007
422 Posts
The problems could also come from a lateral unbalance .

This plane seems very sensitive to that and after I changed a servo control rod for a bigger one and added the pitot tube on the same side of the plane, it became barely controllable cause the wing would suddenly and repeatedly drop on the left and this could be mistaken with torque .

I just had to put that pitot tube ( just a few grammes ) on the other side and the plane became docile again .
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Old Mar 13, 2012, 01:14 PM
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meshyx's Avatar
Norway
Joined Feb 2010
602 Posts
I finally cracked the launching technique and thought I could talk about it here. I launch left handed discus style with thumb on bottom, and have done so with lots of wings.
I am running a 24gram 3000kv motor with a 4.5x4.5 prop, and a 3s1000mah battery, which should make my parkjet pretty average and representative.

I turned down the elevon movements to 6mm up and 5 mm down, and I usually go to 50% roll rate once I'm safely up in the air. I run with the CG at the front edge of the finger cutouts +- 5mm or so. This is probably nose heavy, but it doesn't seem to matter much for this style of flying

I now launch at a bit under half throttle, and give it about half right stick, which moves the right elevon about 3mm up. I had been launching with no right, and full right, and both usually ended in disaster. Since I started using half throttle and half right, I've had at least 10 successful launches with no crashes.
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Old Mar 13, 2012, 01:50 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,566 Posts
I also considered the lateral balance aspect.

Interesting post about half aileron stick on launch. All my launches have had left rolls to inverted, I correct and end up flicking over to right and in. The launch with slight right stick may just be the answer i need. The launch of these is a nerve wracking affair I find after so many crashes.
The 222 run I did had a very shaky start where I just managed to pull her up and away from ground.
I think a catapult launcher needs to be designed for these!
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Old Mar 13, 2012, 03:33 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,566 Posts
OK ... question...

I use a 9X radio and connect one elevon servo to Ch 1 ailerons, other servo to Ch 2 elevator. The radio then via mix gives me elevon control.

I'm consideriing fitting a gyro I have spare from my 450 back-up helicopter, my motor came from there actually ! ... The Gyro is a rate Mode / Heading Hold model and can be switched by Tx on / off ... from HH to RM etc.

What if it was fitted to the PKJ ... full Heading Hold to control roll on launch, once flying flick switch to bring it back to Rate mode or even off ?

Other question of course is how to connect as elevon servos are separate ch's ... ?????
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Old Mar 13, 2012, 05:10 PM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Quote:
Originally Posted by solentlife View Post
I also considered the lateral balance aspect.

Interesting post about half aileron stick on launch. All my launches have had left rolls to inverted, I correct and end up flicking over to right and in. The launch with slight right stick may just be the answer i need. The launch of these is a nerve wracking affair I find after so many crashes.
The 222 run I did had a very shaky start where I just managed to pull her up and away from ground.
I think a catapult launcher needs to be designed for these!
This is what I said yesterday and in previous posts
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Old Mar 13, 2012, 05:28 PM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Quote:
Originally Posted by solentlife View Post
OK ... question...

I use a 9X radio and connect one elevon servo to Ch 1 ailerons, other servo to Ch 2 elevator. The radio then via mix gives me elevon control.

I'm consideriing fitting a gyro I have spare from my 450 back-up helicopter, my motor came from there actually ! ... The Gyro is a rate Mode / Heading Hold model and can be switched by Tx on / off ... from HH to RM etc.

What if it was fitted to the PKJ ... full Heading Hold to control roll on launch, once flying flick switch to bring it back to Rate mode or even off ?

Other question of course is how to connect as elevon servos are separate ch's ... ?????
the right servo plugs into you "aileron" channel and the left into the "elevator" channel on your RX.you have to set the "wing type" to elevon and your tx/rx WILL KNOW IT'S ELEVON AND WILL WORK CORRECTLY.
A gyro come on man,thats cheating....it makes you no better a pilot.Just learn yourself mentally to apply some right stick upon launch to counter the "torque effect" before you know it, you do it without even thinking about it.
You don't wanna be like Bill Hempel and "hover with no hands" but in the vid you can check the gyro's on the tail correcting the surfaces.as far as I'm concerned thats just plain stooooopid and rowdy.now for Joe street it looks cool,but for us REAL rc pilots its a slap in the face IMHO.No disrespect to him,he is a really good pilot,but thats just not a good thing to portray
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