HK Parkjet gets to Latvia ...

[solentlife]

Finally the box arrives ......



Little bit dented ... but seen far worse.

Open box and see what we have ....





Building as we all now know with these kits is pretty simple and quick ... parts slotting into place ... epoxy .... done.



I've decided on my colour scheme and first is to do the light coat ... the underside ....



Paint ? I was going to airbrush with gloss enamels ... but decided to go the easy route and buy the ready acrylic cans ....



You will notice that I haven't mounted any gear yet ... the aileron servo cutouts are obviously for micro servos and these will be enlarged to take 9gr servos. The arms going UP through wing to have rods above to stop snagging in grass etc.

Stick beam and alloy motor mount for the 3700KV motor lined up for it ....... Noted that props fit adaptor fine in pull version - but as pusher need to be drilled out to fit !

Now just waiting paint to dry to get on with next colours etc.

[earthsciteach]

Is this what you are putting the 5x5 prop on? Did you get a chance to bench test the combo to see how it worked out?

[solentlife]

Yep ... 5x5 on a 3700kv heli motor ....

The HK page actually says a 5x5 prop ... but I realise that's for a 2S set-up I believe.

I will bench test once all fitted and ready to go. If it turns out wrong - I shall reduce diameter of prop ... by cutting the 5x5 and that way keep the pitch for speed.

As you know - I'm going for speed above all else.

[earthsciteach]

Oh, yes! You and your need for speed...

I see HK is advertising their new EDF combos with aluminum fan shroud. They don't have the 50 up yet, but have 64, 70 and 94mms.
http://www.hobbyking.com/hobbyking/s...C_Products.asp

What esc are you using with your 4s, again? Stock?

[solentlife]

Yep- stock ..... so many posts / youtubes with stock and 4S ........... so I decided to give it a go ... works fine.(T45)

On the Parkjet - will be using a 35A bog standard ebay job - actually the ESC that went with it in my spare 450 heli ... as the HK Red Brick I ordered for it had to replace the Ultimate ESC that gave trouble.

[earthsciteach]

I have a 4s in my HK cart, along with some other treats - two edf kits (Scramcat and 50mm F-18) plus another 2200 mah, 3s. Its a decent price, even including the international shipping. I'm trying not to hit 'purchase' though! Not a good week to be spending money on myself...

[solentlife]

Now into starting the top colours ....





Once this green is dryish ... the brown will be sprayed on .. no use of masking tape or blind masking ... it will be sprayed to blend edges ... The green here is actually more than final will show - but brown is ok to over spray to create the edge

The acrylic has reacted in a couple of places possibly with release fluid or something on the foam .. but no problem ... first coat should react ... next coats will fill in / sort.

This acrylic is really looking good ... very glossy so really a representation of camo scheme ... thought about using matt paints as my ME109 ... but I want slippery scheme for speed !

The canopy - I am leaving clear as I have a Speed sensor I want to read through the canopy ... but I may paint some framing on or use trim tape.

[solentlife]

Originally Posted by earthsciteach

I have a 4s in my HK cart, along with some other treats - two edf kits (Scramcat and 50mm F-18) plus another 2200 mah, 3s. Its a decent price, even including the international shipping. I'm trying not to hit 'purchase' though! Not a good week to be spending money on myself...

The 920mAh 4S gives a very short run time .... so I wonder what to do ... most I read guys are using 1000mAh - which is only a smidgeon over what I have ...

[earthsciteach]

Paint looks sweet!

I can't imagine how I would fit a 1000 mah into the Mig. But, now you've just caused the cost of my order to increase!

[Fishbonez]

Paint look awesome. Looks very Sci Fi.

[stuart]

looks great,i like the camo paint job idea. looking foward to seeing the powersetup your planing.keep those pictures coming

[solentlife]

Now you can start to see my idea ....







So wait for another drying period enough to allow adjacent colours .... to give more coats. So far only Green - Brown - Green alternates ... still needs a couple of browns and at least one more green.

When the edging tape stopping overspray to underside is removed - I expect to have some paint lifted ... my idea is to spray some underside colour into a beaker to give me some liquid to touch up with a brush ...

I'm getting thumbs up from wife - so it must be ok !!

Once colour scheme is set - then it's install CF rods and gear ... yes I know I should have installed rods before painting ... but it's not a problem as it's underside overall grey ... so a quick spray and bingo.

[stuart]

just a suggestion,use the carbon fiber rods supplied with the kit on the te of the ailerons to stiffen the outer tips during high speed runs. i also added very..very thin ply to increase there strength.

i had slightly thicker carbonfiber rods laying around to install in the fuse. you'll notice there's a certain amount of flex just forward of the carbon fiber rods ,so i used a dremmel to cut a thin slot and add another carbon fiber rod just aft of the le on the wing....the wing don't flex anymore so if you plane on reaching speeds of 140mph+ and going into bank and yank return turns you might want to concider adding these extra measures which don't add weight but do add strength.

i'm actualy on my way to my not so local hobbyshop to p/u ca and epoxy,also am changing the plastic cleavises for metal one using fuel line to insure nothing breaks in flight. which reminds me,i didn't use the hkpj control rods supplyed as they also flex to much cause there to thin.

these are just suggestions as i'm on my second pkjet with another one on the way from china...lol...cause when i crash...i crash big.





switching the clevises was suggested by gramps here at wattflyer and a very good idea if my hkpj and multplex funjet ultra are going to be flying projectiles in excess of 120mph....i hope to reach these speeds and then more....,just like you...gotta need for speed!

[stuart]

wrong picture....opps,this one shows to carbon rod added just aft the leading edge. it's also the precrash photo befor breaking the fuse nose in 3 large pc's.

[solentlife]

I'm considering thin ply sheet to line the battery bay ... gives me something to lock the velcro lipo strap to ... Rx to ... etc. plus giving added strength to the machine. I'm not worried about a few extra grams ... and CF is only in Riga - 3hrs drive ...

I also have long BBQ bamboo skewers ............ wonderful for repairing fuselages !!

[solentlife]

My next mission is to choose the battery and layout of gear ..........

I have :

800 mAh 3S 20C .... 2 of them

1300 mAh 3S 25C .... 2 of them

1800 mAh 3S 25C .... 2 of them

and a bagful of Heli LiPos of 2100 - 2800 mAh 3S 30C

plus 2 of 920 mAh 4S 25C

My thoughts are to go for the 1300 in it ... but run time is going to be low.

Then where to mount the Pitot sensor for my Eagletree Speed Sensor ?

[stuart]

some folks bore a small hole in the front of the canopy to cool the esc and battery,but my esc is mounted to the stick outside the canopy for maximum cooling. my rx is all the way forward and i bet you could fasten your speed recorder device to poke out the canopy like it was a refueling rod...lol..and then you can read it easily.

to get cg with a 1300mah 3cell,the battery will be more midway in the canopy compartment space.

i would consider trying to use the 4cell you have if your motor can handle it. guys who are speed freaks will go beyound manufactures power suggestions just to scream thru the sky faster then the next guy..lol..

the motor i have yet to try out thats installed in the hkpj uses 4cell 1600mah and belongs in a funjet.has a 4.1x4.1 emp prop,60 amp plush esc,and the motors a 3000kv[man its loud] should be a riot to control. what bugs me is the motor in the funjet i have yet to maiden using a 2800mah 30c 4cell dosn't sound or feel nearly as powerful as the hkpj. i have to wait for some warmer weather to give them a go. now building weather here in nj,usa. glad your sharing your build of the parkjet,i'm looking for the next approach to build em faster.

[solentlife]

Trouble with the 4S as I found with my EDF - the run time is abysmal ! I was up for about 3mins before I crashed .... checked the LiPo at home and only 15% left ...... that's on a 50mm EDF with 4200kv motor.
The 1800 3S gave me 6.5 mins.

I've just realised ........ stupid me !! That's interesting that the run-time is direct multiple of the other near enough .... 920 gave 3, 1800 gives 6.5. For some reason I expected the 4S to be better.

The parkjet is fitted with a 3700 450 Heli motor, a Wester Engineering BL. This was very crisp response unit in my spare 450 Heli ... gave about 8-9 mins on a 3S 2100.... in hovering. So a 1300 on it ? calculation if same as abaove gives 4.9 mins .... at speeds I'm hoping for - I reckon my concentration will crap out before that !

Speed sensor ... the PKJ has an advantage over my T45 .... the canopy is more of a long bubble so the probe can find a level attitude easily. The T45 canopy is angled up as it goes back - impossible without adding blocks to level the probe.
The refueling probe idea was same as I had - but unfortunately the probe tube is long and straight. It would be magic if Eagletree were to produce a shaped one to mimic a refueling probe ...

Once I get a few additional probes etc. - I'm thinking to add shaped foam blocks to fuselages so the tube can be fixed in place ...

I thought about fixing under the nose sticking out like some jets have ... but then remembered that we often have incidents where nose hits ground first !!

I hope to run up the motor today ... will report ...

Really annoyed this morning ... masking tape lifted patches of my PKJ scheme at the joint of underside paint to camo top ... now have to find way to patch up without using tape....

[solentlife]

CoG point .....

Can someone measure ideal CoG point from NOSE of PKJ please ? I see various posts on various forums - but no real agreed CoG point ... so if we can have a few replies of where people have theirs set-up to ..... would be great for not only myself - but anyone else entering the PKJ world !

I will now spend time while paints drying measuring and calculating theoretical CoG ...

I realise that we have finger holds that are also CoG points .... but I am also wondering if anyone works outside of those ?

I have run the PKJ dimensions through 5 different online and Excel CoG calcualtors ...... WOW what a load of #$%^&*. Measuring the PKJ - I get a CoG as approx 200mm back from root LE ( that is taking the FIRST point of change of fuselage to aerofoil ).
4 of the calcs tell me to set CoG at ~115mm back from LE ... the 5th at 145mm. Not a lot of use !!

To satisfy any of them - MAC has to be set at 42.6% .....

Back to finger holds !!

[solentlife]

really getting annoyed with the joint line of under and top colours !

If I finger the tape to reduce stickiness ... it bleeds under. If I don't finger it - it lifts the paint ...

I tried spraying into a cup and using the liquid to touch up - doesn't work !

Tried mixing brush paints to get same shade ... failed.

So will have to try and find an answer ... pity that shop doesn't do same colours / paint in brush form as well ......

BUT the model really looks the part .....







Decals going on .............

Other fake reg- ID being made at local vinyl shop ...........

[solentlife]

Apart from the Reg code letters .. she's up for gear now :







Note the sneaky use of part of the supplied decals .... to spark up the underside ! The CF rods have been left unpainted ... I think the black line adds to the scheme.

You may note if you look closely at photos - the canopy is not sitting fully down ... the ESC is too short to motor and prevents rear of canopy sitting down. I shall take soldering iron while enlarging servo bays to open up rear under canopy to allow the 35A ESC to sit in better. I'll probably shave a few mm of bottom of that rear part of canopy as well.

The motor to ESC leads - I will put a screw and tie-back at front of beam so leads are pulled to centre and not trying to escape to side all the time. This will help with canopy fitting ...


OK - here's the motor :





Given the power set-up ... no way I will self launch for maiden ... i will get our groups expert to give it the heave with me trembling at the sticks !!

[Fishbonez]

Wow she looks awesome. You have made a tremendous amount of progress in just a short amount of time. Cant wait to here how she does in the sky

[solentlife]

When I'm home - I'm HOME !!

Just enlarged the exit from canopy ... in the end I decided to cut the rear of ... behind the V slot ... angled the joint so the tail opf canopy foam is angled up from base ... giving a larger area of exit.... Once the epoxy dries - I'll show what I mean...

Slots cut in wing for servo arms to exit top of wing .... Looks like I may have to get some longer arms and then EPA travel right back ....

Rods I will use are ex heli 450 flybars - I have loads of them from my 450 crashes .... bent and no good for 450 use but excellent push rods that don't flex !

Servo slots have been enlarged - will clean up with balsa plate and hot glue once servos in place ... and then tape over ... quick grey spray ....

I'm already nervous about this thing !! It's so light and so much power fitted .... ?

[solentlife]

So set-up ......

Elevons control rods etc. via top of wing ...



Canopy rear altered to allow larger ESC to be near motor and have good air flow ....



Under canopy ....



Note the markings inside canopy area ... these are for different LiPo's to give me balance point.
The two antenas ... one lies along the cockpit floor at edge with clear tape holding it, other as you see is 'loose' and just fed into canopy when closing up ... this gives a reasonable aspect for them

Then :
ESC set down in ....



Now here comes the frightening bit !! This machine should carry a health warning ... should be kept under lock & key ........

I ran up the motor and two things happened .............. 1. the room (big party room) took on a TORNADO aspect !, 2. My wife in russian told me NEVER to run up something like that again inside .....

I shut it down before I hit full throttle .... I had already passed the 300W mark ... it was just way out of this world !

But I have a small problem .... the ESC stuttered ... so will need replacing. I couldn't get a smooth throttle out of it .... so flight testing will have to wait for a replacement ESC .............

I've been with RC for over 35yrs and this machine makes me nervous ! I flew pylon ... aerobatics .... all sorts ..... but this machine is something else entirely.

[solentlife]

Can anyone give me sensible settings for elevons movement ?

I have feeling that this machine is sensitive to an extreme ....