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Old May 21, 2012, 11:24 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,121 Posts
Quote:
Originally Posted by tobydogs View Post
2nd attemp to post video of pkj#1....,man i su.k when it comes to computers.




sorry gang ,i give up with rcg posting vids......if you want to see a shaky first 50 seconds and a much better following 2 min flight . go to wattflyer thread "hobbykingparkjet....need for speed"

why can't i grab photos or vids by copy and paste them here at rcg....it's buming me out




Hobbyking parkjet...need for speed!!!!!!!!!!!!! ( 1 2 3 4 5 6 7 8 ... Last Page)
stuart Today 06:09 PM
by stuart........................................

dang ,i can't even post a link,what am i doing wrong?
You are not only one .... I have given up using the quick buttons here ...

a) url links I post without any additions ... I just paste it in ...

b) vids / pics - just take the url direct of youtube etc. and paste ...

RCG - is the only one that I have trouble with ... all others I use ... boat, gps, etc. quick buttons are fine.
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Old May 22, 2012, 03:18 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,144 Posts
Possibly lightest and slowest Parkjet?

I appreciate all those high-speed Parkjets. I am going a totally different route since I want mine for use in small parks - it should also fly slow when I choose to, and it should not do much harm when it hits someone by accident :-)

Here's a video of my first flights - 10g motor, 2s 180g lipo, 6A ESC. As a setup for city parks this works fine, not surprisingly.

I botched the very first flight, you will immediately guess what went wrong :-)

Parkjet HK 10g motor light & slow (1 min 12 sec)


cheers
Clemens
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Old May 22, 2012, 04:51 AM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,846 Posts
Quote:
Originally Posted by mopetista View Post
I appreciate all those high-speed Parkjets. I am going a totally different route since I want mine for use in small parks - it should also fly slow when I choose to, and it should not do much harm when it hits someone by accident :-)

Here's a video of my first flights - 10g motor, 2s 180g lipo, 6A ESC. As a setup for city parks this works fine, not surprisingly.

I botched the very first flight, you will immediately guess what went wrong :-)

http://www.youtube.com/watch?v=QyClIPfxSoQ

cheers
Clemens
More info I have all the bits including a spare parkjet although I would go 350 instead of 180.
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Old May 22, 2012, 05:44 AM
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Vienna, Austria
Joined Apr 2007
2,144 Posts
lipo for minimalist Parkjet

@aeromaniac - you are absolutely correct, 2s 350 are a better choice, the small gain in weight is insignificant, and duration rises. Also, my 180 were getting pretty warm...
Something else - thrust angle is too much "up", I had to straighten it, just like everybody here I guess
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Old May 22, 2012, 09:18 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,121 Posts
Quote:
Originally Posted by mopetista View Post
....................
Something else - thrust angle is too much "up", I had to straighten it, just like everybody here I guess
UP ? that is probably because you are using a much less powerful set-up than designed. The rear of the motor (prop) centre should be LOWER than the front ... meaning that as power / thrust increases the nose is pushed down to counter the increased lift. But as we get to excessive power as in my 550W and more - we experience strange effects where we start to reduce the downthrust angle to stop the model diving on full power ... or rearing up when power is reduced.
If you have low power ... it's possible that you are suffering lack of that angle to counter nose up.
I would be suprised if you raised the rear of the motor ...

If you use the beam supplied - it sits correctly into the slot moulded in.

Nigel
(running 3700kv + 4S 1500 25C + 5x5 prop gives 203 - 222kph, soon to maiden a 4400kv + 4S 1500 25C + 5x5 prop !!)
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Old May 22, 2012, 11:00 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,144 Posts
blowing up or down

sorry, didn't know there was one correct terminology for pushers as well, but you are correct, downthrust for a tractor prop means the prop is pulling the front down.

now my motor which I had glued to the REAR of the fuse was blowing the air UP, thereby pushing the rear of the model DOWN, so it may be called downthrust, and I will henceforth call it by that name

however since I did not use the motor mount things might be different as far as stock downthrust is concerned...
Anyway, now the motor has very little downthrust left, and the throttle-elevator mix should no longer be necessary...
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Last edited by mopetista; May 23, 2012 at 01:20 AM.
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Old May 22, 2012, 08:49 PM
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Joined Mar 2012
78 Posts
i'm starting pkj#3 tonight.just laminated the elevons with very thin ply using 2part epoxy.i'll be posting pictures of the mods done later and hope to get better vids soon on the wattflyer site.the one there was my first try using a keychain camera on my hat visor,man i fly to far away and move my head to much..lolbut i did get some nice flybys in the 3 min vid.

i hopfully be done this weekend and will post pictures then in order as to how i did them and some explainations for future builders.

this new pkj#3 will be using a nice new wicked 3000kv. i just ordered pkj#4...lol..and will experiment more with the 4850kv and other possible choices as other progress designes to gain great speed.
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Old May 24, 2012, 09:39 PM
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Joined Mar 2012
78 Posts
pkj#3 carbonfiber rod reinforcement of fuse,battery velcro strap,fiberglass tape to cover the fuse hing lines and the areas where landings can wear on the bottom. the 3" tape is way stickyer than the thin stuff hk sent in the kit. it also paints great. bungee hook is installed and a full sanding off of excess epoxy will happen before taping the bottom.
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Old May 25, 2012, 01:32 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,121 Posts
Anyone else had trouble with ends of elevons catching in grass .... basically the grass getting into hinge slot pulling on elevons ? Also crunching the wing tip / elevon ends ?

I'm considering fitting a cap to end of wings that also protects end of elevons ...
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Old May 26, 2012, 02:11 PM
just Some Useless Geek
Chicagoland
Joined Oct 2008
2,545 Posts
Protect the servo arms & elevons

My solution is the standard one: bring the servo arms up through the wing and put the control horns on the top side. I do that for pretty much everything these days. That and taping the hinge the long way to keep out externals.
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Old May 27, 2012, 02:38 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
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Quote:
Originally Posted by A Useless Geek View Post
My solution is the standard one: bring the servo arms up through the wing and put the control horns on the top side. I do that for pretty much everything these days. That and taping the hinge the long way to keep out externals.
I too do this ... both my 50mm T45 EDF and the Parkjet have top mount horns / rods ... but servos still in underside of wing. I use packing tape to seal up the servo / mount area once fixed to give a smooth surface.

My post was about the ends of the wings / elevons - where grass etc. gets caught .. the wing tips get crunched etc.
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Old May 27, 2012, 03:43 PM
just Some Useless Geek
Chicagoland
Joined Oct 2008
2,545 Posts
Oh, right. Well, you can try hot gluing some EPP winglets or tips plates to the ends of the wings. I used to put soft foam winglets on some of my sport planes so that when (not if) they tumbled on an unscheduled meeting with terra firma the replaceable winglet absorbed the damage. With the winglet sticking down that should keep some of the crud out.

Having low profile winglets sticking above and below the wingtips also traps air that would normally roll of the end of the wing and changes the behavior of the wing a little. You have to experiment to see what's gonna happen on a faster park jet.
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Old Jun 05, 2012, 08:13 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
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For my next trick .......... see attached piccie below ! It's a cut and paste impression of my next Parkjet project .........

This is getting serious ....

Question : If a motor / prop gives 150kph with single set-up ... what would a twin set-up of same motors / props give ?

OK main obstacles ? LiPo power ... ESC ... launching.

On the catapult ramp - the props are going to strike the rails if spinning .. so either a dolly is required for POWERED launch, or props stopped and horizontal for unpowered launch .. once clear of rails to then bring in power.

I'm holding back details of the actual specs I'm using .... I'd like to see it work first then all will be revealed ............
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Old Jun 05, 2012, 08:33 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Solent your talking some serious stuff here.i think your biggest headache with a twin will be space...2 ESC's big enough lipo....but will be interesting to see.effectively you cant say that if you get 150 km/h on a single setup it will double,unless you double the battery by the same used,which in this case will be impossible with the amount of space you have.but I'm looking forward to seeing your project
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Old Jun 05, 2012, 08:54 AM
just Some Useless Geek
Chicagoland
Joined Oct 2008
2,545 Posts
Yeah. Your basic problem, Nigel, is that the economy of scale doesn't track with multi-motor setups. Check out some of the discussion on the Multiplex Twinjet thread to see what I'm yammering about. I have a TJ that I'm building with some big motors, but it's more for the cool factor than for any attempt at real top speed. The fastest planes still use one motor and one prop.
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