1:3.7 Pilatus PC21 turboprop build
 

Latest build is on the 'slab', not strictly a jet in the overall scheme of things but a 'jet trainer' and running a turbine so seemed logical to post here.

The kit is an HT Modellbau one, and is the larger of the two available, just under 3M in length and has a span of 2.38M, overall weight should come in around the 20kg - that is if i don't go too mad on the additions [X(]

Jetcat SPT5 is planned, and a reasonable amount of scale bits, loads of lights and if able to source a working MFD set up in the twin cockpit.

The planned colour scheme is not sorted yet, but needless to say if WILL NOT be one of the 'standard' colour schemes, so if you have ideas then please post them, I am sure Ali would be interested to see what ideas you have.

Here's a couple of initial pics of the airframe..

marc

RE: 1:3.7 Pilatus PC21 turboprop build
 

Hi Marc,

And he was telling you to hurry up with my Eurofighter for that?? :D :D

Anyway, there is seemingly only 4 full size schemes! Didn't bother posting the all black one, the all red one or the all silver one. So, the best scale scheme is this one...

RE: 1:3.7 Pilatus PC21 turboprop build
 

However, if you're up for another pseudo scale scheme Al then.....

RE: 1:3.7 Pilatus PC21 turboprop build
 

Yep the yellow one has been spotted [X(] although I think a really 'pseudo' scheme is on the cards..

marc

RE: 1:3.7 Pilatus PC21 turboprop build
 

Could go Reno Air Race stlyle courtesy of 'Relentless'.....

RE: 1:3.7 Pilatus PC21 turboprop build
 

Or 'RAF' it?

Can you tell I'm not working at work :)

RE: 1:3.7 Pilatus PC21 turboprop build
 

Hey Mark. Yep it was a shame to tie up such a talented mans work bench with a done to death flying triangle! Especially as it is so heavy :eek::D
Thanks for the help on the schemes. Whats all this dragging colours from other models?? Thats not scale... the cheek of it! :D
Nemesis one is nice. I was actually thinking of looking into a nice swirly type scheme such as that.
I like the yellow but Mr S is not too keen. He showed me a scheme he was working on that is pretty tasty, but is quite similar to a new model I have coming :(

RE: 1:3.7 Pilatus PC21 turboprop build
 

Hello Marc
My Building is here:
http://www.rc-network.de/forum/showthread.php?t=87444
My first flight video:
http://de.youtube.com/watch?v=IIG79W5gnEU

Have fun!

Merry Christmas
Best Regards, Martin

RE: 1:3.7 Pilatus PC21 turboprop build
 

Ali, work in progress the colour scheme, have some neat 'abstract' ideas (just pitty Ray), will post as I get a few ideas.
Martin, cheers for the info, have followed your thread and will refere to it no doubt on this build ;) - might even re-do the manual for HT.....
Mark, I like the Euro;)

marc

RE: 1:3.7 Pilatus PC21 turboprop build
 

Marc,

Ali likes the Euro too he just can't bring himself to say ;) Anyway, better a manly Eurofighter than this gay looking Tucano thing! :D :D

'Abstract' ideas? Can it be more off the wall than the grafitti'd Jaguar!?

Cheers,
Mark

RE: 1:3.7 Pilatus PC21 turboprop build
 

I actually do like your Euro fighter... for the simple reason its a euro fighter and not another Euro sport. I think it will look the nuts with all is ordinance on, and I actually think it will fly more like a scale jet than a standard lightweight eurosport... such a shame its so ugly and triangle shaped!
Did you mean Graffiti Hunter??

RE: 1:3.7 Pilatus PC21 turboprop build
 

Doh, yep I meant Hunter! - Xmas tipple hitting the spot! :D

Don't go too abstract on this one. It's aesthetically challenged enough without you giving it another phobia with some mental colour scheme :D

RE: 1:3.7 Pilatus PC21 turboprop build
 

OK first impressions are good, the mouldings are very clean and the fuselage is nicely reinforced with carbon in the key places, the accessories are good quality and there seems nothing missed from the fittings. A huge box contains the cockpit items which i have not even dared to open yet as the instructions show there to be quite a few parts involved in the assembly!
The wings on this kit are composite, and are well made, the servo fixings are neat in that the wing has pre-moulded trays for the servos, and although the instructions detail Futaba servos, JR8511's fit nice with a little trimming of the grommet rubbers.
As the turbine is not here yet I decided to start a little work on the wings first. The proposed finished spec includes some 16 lights, excluding an attempt to work out a LCD driven MFD system and cockpit ambient lighting.
Started by cutting out the area for the wing leading edge landing light(s) and was pleased to see mounted behind the cut out a ply base to attach the lights to - a nice touch. Each wing will have 4 lights so running the cable and leads for the aileron was my first job. Unfortunately there are no pre-installed cable pulls, which is a little frustrating especially as attention to detail generally is very good. The internal structure of the wing seems full of ribs and ply parts which makes routing cable very tricky, especially when trying to get the exit point through the hole made in the forward section of the wing root rib. The aileron servo pocket has a hole cut for the servo lead to exit into the wing, but from this point on your on your own, and routing a cable from this tray area is really frustrating.
Eventually after an hour or so managed to get a piece of flexible 'snake' into the servo tray hole and out through the landing light cut out, from here another feed was eventually made through holes in ribs along the leading edge of the wing.
The gear supplied as an option with the kit is very nicely made, but unfortunately the gear is an air down - spring up system which is not ideal. In addition to this the full size aircraft has two circular discs mounted to the main wheels which when closed form a partial door, and are important in the overall look of the finished aircraft. The main gear on the full size has the leg and swing arm inboard, which leaves the wheel rim on the outboard side free for the circular disc to be fitted, the model has the gear leg and swing arm positioned on the outboard side so this makes the disc attachment much more complicated and not scale looking. To spin the gear over unfortunately then causes the leg to foul on the retract cylinder. A solution to this could be a retract with the cylinder at 180 degrees to the closed gear leg, so this and a few other options are being looked into, so thanks to Sandor in advance at Digitec.
As usual I will try to post as many pictures as possible, and please feel free to comment and provide advice/criticism along the way.

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

more..

RE: 1:3.7 Pilatus PC21 turboprop build
 

Little done on the hinging today. Started on the ailerons and rudder, the system used is wire through hinge points and utilises three substantial hinges on the ailerons and two on the rudder. Fitting the hinges to the control surface was simple, and a little sanding opened up the pre-cut slots, making a slot in the wing was another task altogether, as the hinges are very thick fibre glass board the holes required are quite large, after drilling with a 5mm drill bit into the recess in the wing trailing edge I slowly worked the holes into a elongated slot using a coarse round file. the wood running behind the wing recess is very hard and took some time to achieve the final satisfactory openings.
Once done the hinges were test fitted and then finally assembled for fist fixing. The manual suggests around 1.2-1.5mm gap around the aileron to wing surface so to achieve a consistent gap I wrapped a couple of rubber bands around the aileron, these gave the desired gap and held the aileron in the correct place all round the gapped mating surfaces.
Once fixed I noticed the wire retaining pin was very sloppy in the hinge holes, allowing a fair amount of unwanted slack, on measuring the wire pin it showed a diameter of 1.8mm, I tried some 2mm in its place and the result is slack free and rock solid, I guess there must be a slight tolerance issue in the wire or hole cutting but at least the right sized wire worked out OK.
Hinged the rudder in the same fashion using rubber bands, and applied aeropoxy to the inside surface of the hinge plate as I was able to get inside via the servo cut-out to apply the epoxy.

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

Hinged the stabs and fitted the horns to the elevators. To make sure nothing was going to move I drilled two holes in the stabiliser, one at the root and one at the tip, this allowed access to the outermost and innermost hinges inboard of the trailing edge, i then added some Aeropoxy to the exposed hinge shafts to provide extra security.

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

Another.....

RE: 1:3.7 Pilatus PC21 turboprop build
 

Elevator servos........ the kit has pre-moulded servo trays built into each surface, which in itself is a great idea, the only drawback is you are restricted in which servos will fit. The original model was fitted with 9kg Futaba servos, Ali preferes to use JR servos and 6 x 8511's were supplied for the job. After a few hours of sanding and grinding the trays to remove the gel coat, these servos just were not going to fit, whatever was done they remained proud of the surface and prevented the servo covers from fitting flush[:@]
Phone call to HT...... spoke to a very helpful guy called Rector who spoke good English, choices were, use a thinner servo like an 8411 (11kg) or remove the base of the servo trays and remake them with some ply glued to the 'top' skin, unfortunately this could not be done on the stabs as the depth of the tray was already touching the top surface. The original plane has been flying with 9kg Futaba servos without any issues on all surfaces including the flaps, so it was decided to keep the mouldings in tact and use 8411's instead of 8511's.

As the fit is tight I fitted a length of ribbon under the servo to provide a release strap to help remove the servo from the fitting, I discovered just how well this servo tray works without fitting a strap originally[:o]
A little vaseline on the servo grommets makes the whole unit fit really nicely. and the covers once cut to shape now sit flush as intended.

I understand increasing the servo tray depth is a mod HT are working on so a bigger range of servos can be used by shimming out the base of the tray to suit.

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

That servo hatch aint going no where! :D
Good news. The Turbo prop unit should be here next week!
Regards Al.

RE: 1:3.7 Pilatus PC21 turboprop build
 

Oh and I found some other schemes that I think might suit it!

RE: 1:3.7 Pilatus PC21 turboprop build
 

Marc's left space along the one edge for the latch bolt too :D

RE: 1:3.7 Pilatus PC21 turboprop build
 

I was hoping to see a few twist lock attachments myself :D

RE: 1:3.7 Pilatus PC21 turboprop build
 

You big bunch of tarts! ;)

Believe you me if I could find a decent tiny 1/4 turn lock I'd use it everywhere - Dzus and alike just don't make em small enough, and I've looked [&o]

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

The rudder in its standard form uses a single arm link, and although no doubt fine like this it was agreed that if a twin arm, pull pull set up could be used that this would be better and possibly safer. To get a double arm in the space where the servo fits is impossible, I tried all sorts of combinations to try to get the servo arm in and leave the rudder skins with two small openings for the arms, but was finally beaten. In the end I cut away one side of the rudder from the edges of the arm cut out down to the base of the rudder, then made a small replacement panel which screws into place after the arm is fitted, once painted this will hopefully be almost invisible. An 8711 with some modification finally rested in the base of the rudder. Next job rudder double arm..... made a drawing to keep the arm the same spacing as the holes on the servo arm, and cranked to align the holes with the hinge line, now I need your help, do I cut two slots in the rudder, which will need to be wider than the width of the arm to allow it to pass through the rudder and out the other side, glue it without really knowing how good the fixing will be inside, as there is possibly no hard point inside OR do I cut a section off the base of the rudder to suit the horn shape, insert a hard point and glue the whole thing up replacing the cut section, dap of filler and nobody's the wiser?

The nose gear housing is a thin ply 'box' which mounts on the back of the rear turbine former, the retract mounting is a doubled up selection of nicely cut triangular quality ply, into which fits the retract mounting plates via notches and lugs, a very secure system. The retracts supplied however are likely to be changed - the original system uses a wire pull pull steering system, the replacement system should hopefully if it fits use a fixed linkage pull pull servo set up. Thanks to Sandor who has supplied the replacement items for testing. The nose retract has a wider base plate so the original ply mounts had to be remade to allow more room, a small job for the little milling machine.

Once glued together the gear box will have the ply mounts attached and these will also fix to the front former. In addition to making the steering system less prone to tangled wires, it will allow the removal of the original servo tray mounting plate which extended the nose leg 'box' close to the main wing spar tube, leaving an awkward shaped area to fit the fuel tank(s) - with the servo tray removed this area will allow a good sized rectangular tank, and keep things close to the C of G.

A few pics to accompany...

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

few more..

RE: 1:3.7 Pilatus PC21 turboprop build
 

can you explain me what they are?
i also use small screws that are click and tight .
for removal you turn them 1/2 way and they let go.
i use them for cockpit and canopy,s sometimes

RE: 1:3.7 Pilatus PC21 turboprop build
 

Sandor could you send a few samples over, or post some pics for me?

Sent you a mail yesterday on the main retracts - give me a call if you can....

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

here you go
made by Robbe order number 6089
head is about 8-9mm

i did email you back right away

RE: 1:3.7 Pilatus PC21 turboprop build
 

Sandor, no mail here, tomorrow I'll phone..

marc.

RE: 1:3.7 Pilatus PC21 turboprop build
 

Decided to mill through the rudder instead of cutting a section out of the base, there was a hard point installed so the end result should be good and secure. Shaped the FR4 horn to fit and lined up the linkages. Put a securing screw through the centre of the horn and into the hard point just to keep things in place while the Aeropoxy was applied through a hole cut in the base to expose the horn.

M3 linkages and standard clevis control rods hooked the rudder up - no noticeable play and a good amount of movement. Next cut the slot for the Multiplex connector in the base of the fin, set the fixture below the surface by the thickness of the mounting plate so that when the other half of the connector is set into the top of the fuselage under the fin the resulting connection is flush. The fin end of the fitting was mounted to a ply former and this was glued into the base of the fin using the second half of the connector to keep the plate in the right position to leave things flush once dry.

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

Hi Marcs,,, May I ask what these kits cost,,, Awesome plane,

Dave

RE: 1:3.7 Pilatus PC21 turboprop build
 

Subscribed!!!!!!

RE: 1:3.7 Pilatus PC21 turboprop build
 

Replacement retracts are on their way from Sandor (thanks!) so fingers crossed when they arrive I will be able to reverse the landing gear mains so the linkage is inboard. In the meantime cut a few holes for grills and naca intakes, sanded the area for the speed brake and applied a chunk of carbon cloth to reinforce the area prior to cutting out.

Have ordered some carbon tubes to replace the main wing tube, stabs and rudder tubes, these are coming from NZ as this was one of the few places I could find the correct dimensions! The replacement tubes along shave around 1lb in weight - which will go back on no doubt but at least its a plan;)

Will fit the second aileron and start on the flaps next.

marcs.

RE: 1:3.7 Pilatus PC21 turboprop build
 

Looks like it might have to be another 'tank build' - as much as i really don't like making tanks, there seems to be very little on the market that would fit the space available, so have made a plug, covered it in profilm and will start covering if my last hope of sourcing one fails!
Now the original steering servo mounting is removed the freed up space for the tank gives a generous tank capacity option, taking the measurements from my plug a total of 134oz is available, thats around 3.9 litres which would give if filled full around 15 minutes at full throttle on the Jetcat SPT5.

marc

RE: 1:3.7 Pilatus PC21 turboprop build
 

Subscribing. Nice build and beautiful plane.

RE: 1:3.7 Pilatus PC21 turboprop build
 

Marc,

What is your trade secret to keeping the edges of the C/F cloth so nice and neat as witnessed in the last pic of post #33. I do pretty good with it in that respect, but just curious in the technique you use. Once again, another great build thread!

RE: 1:3.7 Pilatus PC21 turboprop build
 

Countryboy, all I do is cut the carbon cloth with a wheel knife along a steel rule following a template made from a piece of card or paper, that way the cloth stays put during the cutting. I apply resin to the surface of the fuselage and carefully lay the cloth onto it, give it 30 secs or so to start to soak in, that holds it in place, then I 'dab' the cloth down with some kitchen roll, this removes a lot of the excess resin whilst drawing it up through the cloth and stops the cloth shifting around too much - I find brushing drags the fibres away from the edge and can distort the cloth.

Hope that helps!

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

Worked a little on one flap tonight, cut through and squared out the hole for the secondary hinge in the fuselage, again no hard point of any substance behind so delved around and found that there is a void built around this opening inside the wing. Measured and cut the corresponding slots in the flap, and as per the wing no hard points just what appeared to be foam barriers mounted inside the flap around half an inch front the slot opening.

Lined everything up, sanded and filed until the hinges sat nice and level and scuffed the mating surfaces with a coarse carbide wheel and cleaned everything off with Acetone.

It took over one tube of Aeropoxy to fill the voids for the two hinges, and even then there was probably room for more [X(] - if your building one stock up on Aeropoxy you'll need it!

Masked and glued in the hinges, wiped the joints smooth with a wet cotton bud and removed the masking tape. I'll check it out in the morning.......

marcs

RE: 1:3.7 Pilatus PC21 turboprop build
 

Flap fitted and hooked up to the servo (temporarily) seems to work fine with plenty of travel.
The larger capacity cylinders arrived from Digitech for the Jet A1 retracts, with an extra 30% capacity these new cylinders statically worked the gear leg at around 60psi so running the system at 100psi should cover for flying conditions. Being slightly wider than the original spring/air units I had to mill around 1.5mm off the mounting blocks but there is plenty of material left to secure the retracts down. The gear looks much better reversed, and with a little tweeking of the gear door shape and adding the wheel disc, the final look should be much closer to the original.

Once this wing is all sorted, I will finish off the second, and then move onto the main instal.

marc.

RE: 1:3.7 Pilatus PC21 turboprop build
 

couple more