Hobbyking parkjet...need for speed!!!!!!!!!!!!!

[stuart]

goodmorning LT,thats a possibilty that nigel also found a few posts ago.....great minds search alike...lol. thanks for posting your find and so far the closest and really exact copy of the pkj is the skyartec skyfun. this is going for $40 as a kit version. at least it's motor mount is stronger than the hk version.

anyway we decide to go will result in new investments,i'll be waiting for the test fight of the pkjs speed runs when the weather and camers are set for recording the runs...lazy..lazy...lazy is how i feel during the winter months. todays morning temps as per my cars reading is 12degs,dang thats cold!

MINI SKYFUN KIT

[solentlife]

I just don'tsee why Mini Skyfun is so expensive ? That's 2x the price of a PKJ kit ...

Nigel

[LowThudd]

A new one at Nitro. You could get 5 of them for the price of that Mini Skyfun: http://www.nitroplanes.com/91a-phoneix-pusher-kit.html

I am liking the EDF version for playing with: http://www.nitroplanes.com/91a-phoneix-kit-esc.html

Looks like a lot of fun, and if I kill it, I still have the EDF and ESC for about the same price as without the plane. lol

[solentlife]

Originally Posted by LowThudd

A new one at Nitro. You could get 5 of them for the price of that Mini Skyfun: http://www.nitroplanes.com/91a-phoneix-pusher-kit.html

I am liking the EDF version for playing with: http://www.nitroplanes.com/91a-phoneix-kit-esc.html

Looks like a lot of fun, and if I kill it, I still have the EDF and ESC for about the same price as without the plane. lol

mmmm another to the list ... good price ! but looks like EPS ?

is it available cheaply international though ... I have feeling this is same as HK Phoenix but that one is the EDF version ... just checked - its EPO.

Very small battery and motor spec though ! Reading HK reviews ... many advise against bigger batts ...

Nigel

[LowThudd]

Just saw this: http://www.ebay.com/itm/ParkZone-Bar...60281791020%26

Missing some bits, but might be usefull when modding.

[solentlife]

Originally Posted by LowThudd

Just saw this: http://www.ebay.com/itm/ParkZone-Bar...60281791020%26

Missing some bits, but might be usefull when modding.

But problem for Need for Speed is a group thing ... looking for a cheap fast pusher to replace the PKJ that all can buy ... one-offs are OK for a single person quest.
The Stryker anyway is outside the design parameter of the humble PKJ IMHO !!

Nigel

[solentlife]

For those who want a more sturdy PKJ ...

We see many modification recc'ds for this baby and I would like to now list my personal ones :

a) Elevons are flimsy to say the least and unsuitable for anything other than sport flying ... any hard manouevring or speed and they will soon let you know. On my first PKJ that hit 222kph - I did as many - used CF rod running span of them. But that soon proved to fail as the foam let the epoxy go and the rods starting to exit the grooves ... So I looked for alternative that would also be better cosmetically. Thin 1/16th balsa sheet epoxied to the underside of the elevons gives a nice smooth and strong stiff form. The balsa can be sanded to regain the trailing edge. The epoxy in the 'sandwich' really does stiffen it up.

b) The fuselage especially at wing joint and at rear where channel is cut for motor leads etc. is weak. So my remedy again is balsa but in form of 1/4 sq beams. 2 of them parallel set into the underside from just about where the airscoop hole is back to mid wing position. These not only are light - but with epoxy again are stiff ... they also provide anchor for stitching to hold the Velcro inside canopy for battery hold downs.

c) On the twin - the channel cut at rear of fuselage is filled in with pink foam to make more rigid.

d) Servo rods and horns on top of wing ... servo still fitted underside. 9gr used instead of the smaller recc'd. The stock control rods are fine and never given trouble.

e) Canopy hold down is by two bolts and blind nuts. The blind nuts are pressed into the underside of fuselage and the bolts go down through the side ;pieces of the canopy ... via holes in fuselage to the blind nuts. This makes sure that canopy becomes one with fuselage and helps stiffen it up. There is no chance of canopy ever 'flying off' in flight !! At over 200kph - it needs serious hold-down !

f) On the single motor PKJ - the motor mounts are fragile and my answer was a L furniture bracket drilled to fit motor ... the bottom part of the L then set into a slot below the wood beam and set in with epoxy. A single self-tapper then through bracket and up into the wood beam. This steel bracket enabled bending to desired thrust angle if required.

g) On the twin - I use plastic RCTimer beam mounts to 10mm sq beams epoxied alongside the fins and to the fuselage. These plastic mounts are more forgiving than metal.

h) Battery retention is by two Velcro straps as sold for 450 helicopters ... I first cut in half to i) remove the buckle, and ii) flip one round so they fasten together. Second the strips are epoxied into bottom of cockpit area and BEFORE epoxy dries - carpet thread is sewn down and through the balsa beams in underside of fuselage and back up ... tied of. Knots have a drop of CA applied to make permanent. My Velcro straps this way have never lifted !!

i) Once all done - I then smear a thin layer of epoxy along the centre fuselage underside to give some protection for landing.

I do not add anything to the wings - I keep to the original kit CF rods and that's all. The foam wing is thick and has proven more than strong enough.

I will mention glue joints though. The foam used is not so happy with epoxy without a little work done. It needs to be roughed up a little ... if left smooth - the epoxy cannot 'grip' and over time will 'let go' ... So scoring of the glue surfaces to give a good key for the epoxy to sink into and 'grip' cures that.... this applies particularly to the wing to fuselage joints.

So - nothing overly fancy in my mods ... simple, easy and seems to work.

When I renovate PKJ1 - decided that with no further kits coming out - have to recycle the old !! - I shall incorporate lessons learnt from it and PKJ2 ... I hope to have her back at speed ...

Nigel

[solentlife]

Got home flight details now - arrive early evening tmrw - bad news is -10C and loads of snow !! Not so much the cold but the snow depth makes using the catapult interesting !

Lets see what happens when I get home ...

Nigel

[stuart]

hey there nigel,don't worry about us waitting for the twin maiden...if it goes down in deep snow it'll be a drag getting it back. as for me,its going to be spring soon enough and club dues/ama fees are all paid so it just a matter of when. my pkj's,funjet,stinger are also going to wait till i get my winter thumbs warmed up to the sticks again...lol....

[solentlife]

Went flying today but wind was strange ... gusting and changing direction a lot ... flew the Cessna and didn't enjoy it all ... That is bad if I don't enjoy the Cessna. Snows not too bad ... about a foot deep - so bungee can work in that.... as long as I clear a 'ramp / trigger area' ...

Sunday 24th is a Latvian Meet in a town not too far ... so lets see what we can do there ...

Nigel

[dahawk]

Might want to check out the JPowers Screamer as a replacement. I beleive they are available in airframe only kits for pretty cheap. 100-120 mph on 4S

http://youtu.be/4Uqq0P3fIsI


http://www.hobbyb.com/2012-new-skyan...html?cPath=121

[solentlife]

The Meet was at a farm field with snow coverage total !!

Been OK for the slow stuff etc. but no way for PKJ Twin.

On the Screamer ... that's been looked at ... and is a prime contender along with a couple of others ...

Nigel

[solentlife]

Speed machines - any news on replacements yet ?

While stuck waiting weather for the twin ... decided to play pusher with some others ...

Check out : New Life into 50mm T45 - Pusher.

The test results are amazing and could produce a winning machine !!

nigel

[solentlife]

Today had attempt to get the Twin in the air ...

This highlighted a problem .... because the props foul the rails of the bungee launcher - it's necessary to fire her off dead-stick. By time you get power on - she's hitting the deck.

She's all repaired ready to try again ...

Vid to follow ...

Nigel

[solentlife]

Failed twin launch attempt ....

http://youtu.be/d5H2nt5O9vI

Nigel

[stuart]

hey Nigel,sorry to see the bungee launch didn't go well. was it out of alignment still ? the wing tipped almost immediately after release. i don't know,but wonder if for power off we should use longer line on the bungee. perhaps also stretch the bungee longer.

i have my bungee doubled and it pulls real fast and very hard....but i believe if i launched without power it would glide ground level and be difficult to slow throttle up.

I've been building this winter more than most. finished the bird of time,and am starting the great planes RV 4-40. this will be my second complete RV 4-40 build and hope to get the wing right. it's a dumb design for wing assembly and warps are common.[as others state in their build threads.] the GP RV is a beauty when complete and flys great. I'm going for a copy of the one i crashed due to cheap china equipment.

i won't be flying the pkj's or funjet till i get the fingers warmed up to the sticks again....also going on a 2 week cruise with the wife for our 25th annie 2nd week in april. so i hope to be hitting the Field regularly from may on. i hope you get the pkjt to fly and record a fast flight,it's been quite in the pkj threads this winter.

[solentlife]

Hi Stu ... have a good cruise - (my brother was Lead Surveyor checking out Cruise Liners in Florida ... he's now retired) ....

With my lack of time at home - I have to fly whenever I can. It's bitterly cold out there, but what to do ? I'm away again on 28th to Singapore ... so that will be 2 - 3 weeks away again.

I've been having a lot of thoughts on the failed launch ...

a) I would be reluctant to let anyone try hand launching her ... there's no protection for the hands top or bottom ......... so I'm committed to bungee. The tension I have is 5kg on the bungee ... so that should be more than enough. It was enough to get the 1.2kg Twister away ...

b) I'm now working on theory that because my motors are above the longitudinal thrust line of the model - that my slight down angle is pushing her nose down as well. I don't want to help launch by slight UP thrust angle - as that will be a killer once she's at speed. So I propose to take out all down thrust and level the motors.

c) Any slight misalignment of motors to EACH OTHER could introduce a roll moment...

d) I could also introduce a touch of up elevons at launch ... but will have to be careful not to have her loop up and over.

e) Another point is that my PKJ1 with single motor launches of ramp with cruise power engaged. That means I have authority over pitch without having to have hook back as with a glider. This twin though launches without power and so may need hook moved back similar to a glider to help get the authority back to elevons.

The twin against the single has a lot of specific factors that need care.

Today I will be cropping back 5x5 props to fit her to try and give it another go - once adjustments made.

She WILL fly !!

Nigel

[solentlife]

Well motors are now closer to zero thrust line ... in fact when I checked before altering - I was surprised how much DOWN was in the mount.



So shimmed and refitted ...





I added shaft cone nuts behind the prop nuts ... the contra prop had loosened its prop nut ! Plus it adds a few grams weight to tip her back a touch.

Here's my new props .... 5x5 cut back to 4.5 x 5 ... and matched via the blade balancer. Surprisingly - one prop even though cut, sanded together with it's partner was significantly out of balance and needed a sliver of tape on its back face.



and my prop cone tool .......... always looking for a rod or similar to tighten / undo these cones - I took a offcut of 2mm bar and created a bar tool. Wrapped L end with tape so I can see it in box and also protect my hand from rod end.



The Twin balances on the front edge of finger holes with 1600 Zippy Compact 4S ...

B*****y wind is up again - so today's trial cancelled await see what happens later ...

Nigel

[dahawk]

Might want to re-look at the Radjet 800. Inexpensive kit only's from HK. Lots of mod opportunities as shown over on RCG. Here's one doing 249 kph / ~ 150mph Fast enough for ya? http://youtu.be/tNkZqLZW2w0

-Hawk

[solentlife]

Originally Posted by dahawk

Might want to re-look at the Radjet 800. Inexpensive kit only's from HK. Lots of mod opportunities as shown over on RCG. Here's one doing 249 kph / ~ 150mph Fast enough for ya? http://youtu.be/tNkZqLZW2w0

-Hawk

Not sure what it is about the Radjet ... but I'm not a fan of it ... Looks all wrong to me with that strange wing form.

I've got Snice- Mitar about 50% done at moment .. waits my return to finish.

Nigel

[solentlife]

Health is getting to me at moment ... had a bad trip, ended up very ill but soldiering on ...

Have various things to sort ... cars blown a pipe in the heater so glycol is leaking to front drivers footwell .... house is needing work ....

But at least weather is not so bad ... so once I start to really perk-up health wise - will get on with the PKJ replacement and tests. As well as getting that pesky Twin flying !

I do have another suggestion for a PKJ replacement ... there's been a bit of a showdown between a Pusher guy and the 50mm EDF boys. Now that 50mm range has some really interesting possibilities - I'm leaving out the Screamer which was already suggested by others ...... The bare airframes are easily acquired from Hobby B in USA / Canada ... International postage is available ..


Ones that come to my mind are :

Mirage
F16
F18

with the Screamer as a possibility. I would expect the F18 and F16 to be the fastest ... but would probably have battery limitations.

Nigel