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Old Dec 16, 2012, 04:25 PM
"Kneel before Zod!"
turbovector's Avatar
Tacoma, WA. USA
Joined Dec 2003
490 Posts
It's only 2 amps over max and has full airflow so it should be fine if the bearings don't give out. As soon as the weather cooperates I will have a flight report.

solentlife, are those red brick esc's?
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Old Dec 17, 2012, 06:08 PM
Note to self, put on pants.
Jayman72's Avatar
Australia, VIC, Frankston
Joined Mar 2012
89 Posts
Hey guys
I bought 2 x kits to fill out a HK order 6ish months ago. Time to build.
Read a fair bit of this thread.
Anyhow was watching TV show megafactories the other day on the new 747-8 jumbo and how they changed wing design to reduce drag caused by tip vortices and thought of the Parkjet straight away. Clearly at the speeds we are talking here, drag plays a big part. I am sure that by doing some mods to the wings and vertical stabs we could make these a bit less draggy which has got to help with top speed. Either by cutting the ends of the wing tip make a more gradual curve or even adding tip extensions to curve back and greatly reduce these tip vortices. I am not involved in aero in any way, just throwing science at the wall to see what sticks!
Jamie
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Old Dec 18, 2012, 02:55 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,389 Posts
Quote:
Originally Posted by turbovector View Post
I'm using a Turnigy 2826-6 2200kv.
On a 4S ? and a 5x5 ?

mmmmm just checked my data table and I had :

2200kv motor
5x5 prop
4S 1500 25C
~180W

Speed was 130kph

the motor I used there was a touch on small size and I would have probably been better running a smaller prop.

With the extra power yours shows ... and my 222kph was based on a 550W setup ....... I reckon you will be in the high 180's but I doubt you will crack the 200 mark. That needs more kv and brute force.

Nigel
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Old Dec 18, 2012, 03:02 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,389 Posts
Quote:
Originally Posted by turbovector View Post
.......
solentlife, are those red brick esc's?
Yep ... 2 x 50A Red Brick Opto ESC's

When run up with the 3800kv motors as you see there - before I got past about 3/4 throttle I had already hit over 100A and it was climbing alarmingly .. with the 4S LiPo in distress .. I actually saw the Velcro straps rise with the puffing ...

I have had good service out of RB ESC's ... it's ME that destroys them !! If i used them properly and not abuse them - they would last forever.
I'm bad as i want maximum power but need to keep weight down ... so I use as low ESC as I can, when you get to 50A and above - the ESC's become heavy and huge ! Think what twin 70's etc. would be like on the back of a PKJ !!

Nigel
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Old Dec 18, 2012, 08:00 PM
"Kneel before Zod!"
turbovector's Avatar
Tacoma, WA. USA
Joined Dec 2003
490 Posts
I am hoping it will do better than 180kph (111mph) but breaking 100mph is enough to make me happy. This is (hopefully) the fastest aircraft I have owned to date. The 4s i'm using is a Nano-Tech 1000 45-90c. Sounds like you need the 65-130c packs. I have read good and bad on the Red Bricks, I wanted to hear from someone using them regularly. My Birdie 50A weighs 44g, I can't imagine 2 of them on this airframe.
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Old Dec 21, 2012, 02:32 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,389 Posts
Quote:
Originally Posted by turbovector View Post
I am hoping it will do better than 180kph (111mph) but breaking 100mph is enough to make me happy. This is (hopefully) the fastest aircraft I have owned to date. The 4s i'm using is a Nano-Tech 1000 45-90c. Sounds like you need the 65-130c packs. I have read good and bad on the Red Bricks, I wanted to hear from someone using them regularly. My Birdie 50A weighs 44g, I can't imagine 2 of them on this airframe.
I don't use nano's ... i wont waste my money on them again.

Red Bricks ... in fact I have had good from them, apart fromn cooking them by deliberate overloading. They also can be programmed with the card from HK ... now that's a bonus if ever was one.
Birdie .. I have a 70A one in my F16 ... horrible ESC ! It works but it's so huge and awkward shape .. I will stick to Red Bricks and HK next time. I bought it as it was cheap and give it a try.

180kph ... mmmmm maybe ...further thought I think it will be less ... but I can be wrong.

For anyone interested my twin motors have just arrived and over next few days will be fitting and testing. For flight - that's questionable as winters arrived and we have deep snow and -9C out there. I will have to get help to clear an area so I can rig the bungee. There is no way I will let a hand launch with twin props !

Nigel
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Old Dec 21, 2012, 03:32 PM
Wats the worst that can happen
TheCure's Avatar
Canada, BC, Surrey
Joined Jan 2009
513 Posts
Anyone tried dual stock PJII motors with 4s, and maybe 5x5 props?
The stock motor pushes it pretty well with 4s - two of them should get close to 200km/h, no?
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Old Dec 22, 2012, 08:27 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,389 Posts
Quote:
Originally Posted by TheCure View Post
Anyone tried dual stock PJII motors with 4s, and maybe 5x5 props?
The stock motor pushes it pretty well with 4s - two of them should get close to 200km/h, no?
The main idea of the twin is to have contra rotation props and remove the torque problems of high power set-ups.

I would expect the stock motor in twin set-up should give a pretty reasonable result, 200kph is a tall order though - it depends on the pitch speed you can attain with it.

I'm a little delayed with setting up my Twin ... wife wants me to sort the lights and trees at front of house ... plus sort stuff indoors. I've been clearing my bench, actually my office desk !, of the QB10 parkflyer scratchbuild I'm working on ... so once that's all sorted - the twin will be set-up and tested.

Nigel
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Old Dec 22, 2012, 11:40 AM
Registered User
Joined Nov 2010
2 Posts
Be careful hand launching this plane. I cut a tendon in my middle knuckle right hand this week. It was my third time that day to fly the plane and kept the release hold too long. I have flown many wings and had two of the larger fun jet, but this is the first time to cut my hand and it was pretty bad. Had a hand doctor sew it up yesterday and recovery will take 4 to 6 weeks.
Watch that prop! I am going to start launching from holding the wing and not from under the plane.
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Old Dec 22, 2012, 02:39 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,389 Posts
Quote:
Originally Posted by Parkflyer_2010 View Post
Be careful hand launching this plane. I cut a tendon in my middle knuckle right hand this week. It was my third time that day to fly the plane and kept the release hold too long. I have flown many wings and had two of the larger fun jet, but this is the first time to cut my hand and it was pretty bad. Had a hand doctor sew it up yesterday and recovery will take 4 to 6 weeks.
Watch that prop! I am going to start launching from holding the wing and not from under the plane.
For about $15 - 20 ... you can build a good catapult bungee system ... much better than any hand launch and SAFER !

My system caters for my EDF's and Pushers ... once used - you wonder why never had one before !

Nigel
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Old Dec 22, 2012, 05:07 PM
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Joined Nov 2010
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Is there build instructions for the bungee catapult? I know it will be safer.

James
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Old Dec 23, 2012, 12:34 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
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Quote:
Originally Posted by Parkflyer_2010 View Post
Is there build instructions for the bungee catapult? I know it will be safer.

James
If you email me - I can send on my design ... simple ... effective.

It uses 10m 6mm Red Hi-Start bungee from Hobby King. It's doubled to 5m to reduce area needed to use. But still sufficient length to allow the angle and climb out.

Then 3mm braid line back to a ring on a simple pedal foot trigger.

Before the line reaches the ramp rails - it splits of to the model line with another ring. This is far superior to a single line system as no weight is on model until you release the main line

Ramp rails are simply domestic plastic plumbing pipe .. I use 1/2" but 3/4" would be better.

Here's the schematic :



The foot trigger :



Here you see how it works ... Nail sticking up through top pivoting piece .. tread on back part - front raises and pushes ring of the nail.



Main anchor for bungee (3 pegs - better safe than sorry !) ..




Packed up ready to go ...





Here's my T45 on the line ... here you see a clean launch ...



If you check out my Youtube channel : "solentlifeuk" you will see many videos of the system in use .. pushers, EDF's etc.

I prefer the longer bungee type as this instead of the type with bungee wrapped behind a ramp board ... they work, but the energy pull cycle is very short and if model is not away clean of the board - it's a crash ! With mine you get a steady pull for about 15m and then line drops away clean... never had a prop strike with pushers ...

I use 5kg tension for all my models which is actually a lot ... but they survive ! I have measured the exit speed of my rails ... the Hk Parkjet unpowered registered 113kph on the speed pitot ... that's literally as fast as the stock model !!

It's worth the little bit of time and effort to make the catapult ... took me just a few hours ...

Nigel
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Last edited by solentlife; Dec 23, 2012 at 12:48 PM.
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Old Dec 23, 2012, 05:41 PM
Registered User
tobydogs's Avatar
Joined Mar 2012
78 Posts
nigel,its almost funny how much fun the bungee can be. folks love to ask questions and its almost always a success to luanch these pkjs and funjets.

i agree with your longer bungee approach and would suggest anyone who can't nail stakes into the ground to use my weight method. i just leave the weight at the field so not to have to carry it in the car. the weight is hanging so i could paint it yellow. note the rails on my launcher are sliding at the "t" connections so i can adjust easily for funjet/parkjet/stinger. i do plan on shortening the hieght of the launcher. it also breakes down easy and use's velco straps to keep the pc's together when stored in the garage.
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Old Dec 23, 2012, 10:52 PM
Wats the worst that can happen
TheCure's Avatar
Canada, BC, Surrey
Joined Jan 2009
513 Posts
I just measured my newer un-maidened parkjet. Its got a 4200kv 2627 outrunner motor, 50a esc, 4.1x4.1 prop, running on a 4s 1300 nano.
I read about 1100g pull, 58a max @836watts. I think it weighs around 350g.

Am i going go have problem hand launching it?? Can i get by without a bungie if i apply liberal throttle to launch?
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Old Dec 24, 2012, 01:01 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,034 Posts
With that amount of power I would have thought she would have taken off vertically from your hand I once saw a Mugi Evo launched in a similar fashion and it only had half the power.
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