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Old Dec 31, 2011, 03:41 PM
Wonderfully Wicked
The Don's Avatar
Willoughby, Ohio
Joined Jan 2002
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Build Log
Wicked powered Hobbyking Parkjet

Build log for the Hobbyking Parkjet model found here:
http://www.hobbyking.com/hobbyking/s...dProduct=18249
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Old Dec 31, 2011, 03:41 PM
Wonderfully Wicked
The Don's Avatar
Willoughby, Ohio
Joined Jan 2002
13,204 Posts
Started my build today.

Notes:

1) I suggest using a magnet on the front of the hatch instead of the metal bar, mine was pretty easy to get the canopy to come off.

Don
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Last edited by The Don; Feb 29, 2012 at 12:04 AM.
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Old Jan 01, 2012, 12:15 PM
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Maryland, USA
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I finished up my HobbyKing Parkjet this morning, and maidened it. Build report in this post; maiden report in the next one.

Equipment:

Wicked Jr. motor (the 3200 kv one)
APC 4.5x4.1 prop
Jeti 18A ESC
HXT500 servos
3S 850 mAh 20C LiPo (the one that comes with the SkyAngel mini-EDFs)

This plane is basically like a mini-Stryker -- only with a pretty canopy, and a roomier, easier-to-deal-with electronics compartment area. My build, and my equipment used, are very similar to my lightweight Stryker build that I documented here. I'm attaching a photo of both of my Wicked Jr.-powered wings together for comparison (Stryker and Parkjet).

Some issues on the build:

1. I didn't used the supplied motor mount. There are too many complaints about it's flimsiness/breakage, and it needlessly puts the motor up high, where it's likely to cause a pitching moment. So I used one of those inline plastic stick mounts, same as I did on my Stryker. But one thing to think about when doing this with the Parkjet is that the molded-in trough for the stick is not exactly parallel to the fuse...it angles up a little towards the back. They probably did this to counteract the pitching effect of the supplied elevated motor mount. I didn't bother leveling it out before gluing in the motor stick, but I kind of wish I had (see maiden report).

2. The HK equipment list calls for 4.5g servos, and the servo pockets are just the size for HXT500s (5g), so that's what I used...though I was a little unsure whether that would be enough of a servo for this fast of a plane. No issues with it on the maiden anyway...the plane was appropriately responsive at all speeds. One or both HXT500s was pretty noisy though. I don't like the HXT500s as much as I like the HXT900s...they just don't seem to be that good of a servo in my experience.

3. I considered flipping the servos around and having the servo arms come out the top of the wing like on the Stryker. But the Parkjet wing is too thick to do that without some surgery beyond just poking a hole for the arm, so I didn't bother. If I was going to spend more time on this build and really do it nicely, I would fill in the supplied servo pockets with blocks of scrap foam and dremel out new pockets on top.

4. Center of gravity: I found that for the plane to balance at the center of the finger holds, I had to position the 850 mAh battery at the very back of the compartment, pushing up against the ESC wires and the foam of the compartment lid (which I had to trim a little to clear the battery). I installed a velcro strap there, and velcro on the floor (photo). For the maiden, I positioned the battery a little more forward to get a CG about a quarter-inch forward of the center of the finger holds..."just in case."

I used full-temp hot glue to put the model together, except for the canopy which I glued on with Foam-Tac. My AUW came to 9.6 oz/273g.
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Last edited by herk1; Jan 01, 2012 at 02:53 PM.
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Old Jan 01, 2012, 12:29 PM
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Maiden report:

Throws: I set my low-rate throws at a "guesstimate" of 4mm each way for both aileron and elevator, and that worked out pretty well. If anything, maybe a little too sensitive on ailerons, depending on your personal preference...i.e., if you like a plane that can roll at three rolls per second...which I do!

It was a little windy...about five or six mph average, and little gusty. Of course, the wind direction was right out of the sun (one of those "Murphy's Law" things). I gave the Parkjet a sidearm frisbee-toss (to avoid the prop passing over/near my hand) at about 2/3 throttle and about 30 degrees up-angle. This is the launch technique that I have found works best for me with my Strykers. It worked well enough with the Parkjet too, and away she went!

It took a whole lot of "up" elevator trim...I lost count of the clicks I put in...and a lot of right aileron trim too. I'm curious how much of that elevator trim will need to be taken out after I try a flight with the CG moved back to dead center of the finger holds.

The plane flies a lot like a Stryker (which is a good thing), except for having a much faster roll rate, and generally being somewhat more twitchy and less stable. So, it's more responsive, but consequently less relaxing to fly. The Wicked Jr. provided way more power than needed...I spent most of the time at 40 to 50 percent power, with occasional bursts of full power to test the speed. It's pretty fast -- seemingly about the speed of my stock "funfighter" J-power Corsair on 3S.

There was a noticeable climb/up-pitch when going to full power. So I kind of wish I had leveled out that stick-mount trough that I mentioned in the build report.

I flew for eight minutes on the 850 mAh battery, which was only charged to 85% due to the cold weather. When I got back home and put the battery on the Cellpro, it showed nearly empty -- only 4% charge remaining.

Overall, this plane is a pretty nifty parkflying little-brother to the Stryker.
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Old Jan 01, 2012, 07:04 PM
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Nice where did you get that motor mount? Any video?
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Old Jan 01, 2012, 07:31 PM
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It's this motor mount:

http://www.hobbyking.com/hobbyking/s...5pcs_bag_.html

No video, but I might try to get a doppler sound recording to measure the speed.
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Old Jan 02, 2012, 09:37 AM
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Quote:
Originally Posted by herk1 View Post
It's this motor mount:

http://www.hobbyking.com/hobbyking/s...5pcs_bag_.html

No video, but I might try to get a doppler sound recording to measure the speed.
Great! Use those before!
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Old Jan 02, 2012, 02:23 PM
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Thanks for your rfeport. I wil use your lessons learned when I build mine
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Old Jan 04, 2012, 12:44 AM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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Thanks for posting all your info. I plan on using the Wicked Jr 3200 as well in my built.
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Old Jan 05, 2012, 01:51 AM
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Is the wicked Jr 3200 can be used on 4s? Or maybe you have one in the 2200Kv?

Mine is getting ready.
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Old Jan 16, 2012, 08:31 AM
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I really like the way that orange paint goes with the stickers to give more color to the model! I wish I had thought of that. I put the supplied stickers on my model too, but just on the plain white foam. I usually don't use the supplied stickers/decals for a kit like this, but I think the ones that come with this model look pretty nice.

I dopplered my Parkjet at 82mph. Which is pretty good considering that Don gives the motor/prop pitch speed as 85mph. The Parkjet is a pretty sleek/low-drag airframe. On the same excursion, I dopplered my funfighter Corsair at 75mph. So my feeling that they were close in speed was true.
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Old Jan 24, 2012, 09:24 PM
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Pacifica,CA
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Quote:
Originally Posted by choopi View Post
Is the wicked Jr 3200 can be used on 4s? Or maybe you have one in the 2200Kv?

Mine is getting ready.
Choopi,

I just tested out my Wicked 3200 on 4s which I plan on running on this pj. I ran it for 5 sec wot on a 1000mah 4s 30C
I got 340watts @ 24 amps under 13.5V & 1lb 1oz thrust. This was with a 4.1x4.1 apc prop. The motor was only 70 degrees warm. I also tried a 450mah 4s 35C battery which gave me 288Watts @ 22 amps.
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Last edited by awayne; Jan 25, 2012 at 05:33 PM.
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Old Jan 25, 2012, 05:33 PM
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Don, what timing setting do you recommend for the Wicked Jr 3200kv motor? I have mine set to low right now. Thanks!
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Old Jan 25, 2012, 05:39 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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I usually runs on low as well. The 3200 Jr motor has 9 magnets so is in between the typical 12 mag and 6 mag motors. I have never run that motor on 4S like you are doing. I am interested in how log it will hold out.

I will be starting my build on this model shortly. I have been cleaning my whole modeling area now for weeks now as it was at the point of so much mess I could not build anything anymore. I am just about done and it is nice to see clean model area again!
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Old Jan 25, 2012, 06:10 PM
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I haven't started building it yet. Once I've flown it a few times I'll be sure to post. Thanks!
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