Home The News Hanger 9 Piper Pawnee - 80" span - built by John Carby-Hall
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Hanger 9 Piper Pawnee - 80" span - built by John Carby-Hall E-mail
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Thursday, 12 March 2009 09:01

I had been wanting one of these since I saw David Muir's fly at Rufforth in high Summer.  His flew in a scale like manner on the recommended electric set up of E-Flite 46, and a 4S1P 5000 mAh pack.  It had enough grunt for prototypical low passes, with hammer-head turns to line it up for the opposite run.  It did loop and roll, but looked a bit embarrassed doing so.

I put my order in at the Model Shop immediately, and was told that there were none in the country and the next delivery would not take place until the end of August.  In the event, none appeared until early December.  I was convinced that that the price would have gone up, but no, it was the same, less the Chancellor's pump priming two and a half percent VAT cut.

What do you get for your £123 or so quid.  ( As of today's date - 29 February, the price is now nearer £180) The answer is, a hell of a lot of ARTF, and it's Hanger 9 quality.  The box itself is quite intimidating.  Nothing that the petrol heads amongst us would be impressed by perhaps, but it was bigger than anything I had staggered out of the shop with.  Wherever it had been on its travels, the covering didn't seem to have been affected.  Everything looked taut, and I was interested to see that in common with many of their offerings, Hanger 9 gives you the option of electric or i.c. power, with hardware included for both.

I thought about that for at least ten seconds.  I have an RCV 58 doing nothing.  Then I looked again at the lovely light computer cut framework, and asked myself if I really wanted it shaking to bits, and soaking in slimy, smelly stuff?

I'm a great fan of the E-Flite 46 set up.  I have them in my Hanger 9 Pulse ( 5lbs 10 oz, and 94 watts/lb ) and my Banchee ( 4lbs 2 0z and 145 watts lb ).  The Pawnee is supposed to come in at between 8 and 9 lbs, so scale flying was going to be the thing, but that's the fun of electric.  All you have to do is get the set up right.

I made a start in the dark days between Christmas and the New Year.  It was far too cold to contemplate building in the garage, so I commandeered the spare bedroom.  Fortunately this really is an assembly process.  The only problem is space.  The thing is large. 

The well illustrated handbook would have you begin by assembling the undercarriage.  There is a spot welded and painted rendition of the full size undercart with a rather clever way of securing the 3.5" diameter wheels.  You take off the hub cap, unscrew 4 self tappers holding the two opposing halves of the hub together, and then take off the solid, but soft rubber tyre. Slide the inner hub on the axle, and secure it with a collet set-screwed on.

"Aha", I thought.  To avoid trouble down the line, I shall have to grind a flat on the axle, and then use thread lock to hold the allen screw.  Not a bit of it.  The axle was already pre-ground in just the right place.  I did thread lock it though.  Tyre on, outer hub screwed in place, and finish off with the hub cap.  That might need a touch of Uhu Por to stop it escaping. Repeat the process on the other side, and that's the u/c done.  Fix it with 4 conventional nylon straps, held with self tappers into predrilled holes.  This is all too easy!  What are they screwing into, and will they stand up to a duff landing.  Well, the whole fuselage is typically lightweight, but there are a couple of substantial hardwood beams to accept the screws, so I have high hopes.  If all else fails, the area can be reached from the underside, by cutting away adjacent covering film.

My first reaction was that there was a little too much side play allowed on each wheel.  With the single collet being in the centre of the hub, there is a need for some packing to get rid of this.  I'll revisit it and shim it out with washers.

The fin is already in place.  At this point, one has to do a small amount of actual fiddly work, and fit the rudder hinges, and the pre bent wire tail wheel wire, and nylon support.  The nylon support is first epoxied into the base of the fin, leaving the tail wheel wire in position for offering up to the hole drilled for it in the base of the rudder. All standard stuff.  You are advised to drill out the preformed slots provided for the furry hinges, before fitted the hinges, centred with a pin through, and epoxying the wire into the rudder hole.  I've never had an ARTF with so much done, so accurately, before.  So much so, that I felt a bit miffed when I had to spend a couple of minutes trimming the base of the fin to allow it to move easily past the tail wheel nylon support.

The tail wheel looked far too small for service on our grass field.  In addition, the hole drilled in it was marginally tight on the axle, so I looked in my magic spares box, and upsized.  Saved me freezing in the garage while I drilled out the hub as well. That was fixed with a small collet on each side, grub screwed with thread lock.

You're supposed to start on the wings next, fitting the aileron and flap servos, but I couldn't resist playing with the tail-plane.  There is no mucking about with a sharp scalpel, trying to cut away film without going through into the underlying balsa substrate.  Here, you are presented with two tail-plane halves, with a couple of small carbon fibre locating dowels on one half, and matching holes already drilled in the other.  In addition, each half has four holes predrilled, right through.  One has to offer one tail-plane half up to a precut slot in the fuselage, present the other half through from the other side, and ensure that the locating dowels engage with their matching holes.  Finally, the whole caboodle is secured with a pair of cap-head screws right through each half, through substantial fitted plywood lugs passing through the fuselage immediately under the tail-plane.  There is no way that that lot is going to let go.

That is only the start of it though.  The next step is to find the preformed brass brackets which attach, after putting an approximately 30 degree bend in the middle, to the tail plane top and bottom, using cap head bolts and self locking nuts.  A similar set up is fixed to holes in the fin, although these brackets have pre made-up straining wires, and clevises already fitted.  For the underside of the plane, the brackets screw into the fuselage.

The trick now is to rig the whole empennage so that the wires are at just the correct tension.  A slight problem is that the clevises are only of nylon, with self locking pins.  If you are unlucky, as I was, you shear off a pin.  I spent a whole hour looking for a matching clevis, or indeed any clevis that would screw on to the threaded rod of the rigging wire.  Eventually, I found a relic from the 1960s with the correct imperial thread, and used that.  Shortly after I found another bag of clevises which I had overlooked, and found that Hanger 9 had even provided spares. Doh!

Now for some real aeromodelling.  You need to drill the holes in the servo trays for your selected servos, centre the things, and fit the push rods.  Nylon clevises again.  These will have to be changed.

Each half of the elevator has its own wire pushrod, carried in a nylon tube.  The two pushrods are joined by collets after adjusting for neutral, and that's the tail feathers working. I registered one slight snag, when I had to saw 1/2" off the elevator pushrod which was over length.  Shock - Horror.

The wings emerge from their polythene chrysalis looking immaculate.  The flaps and ailerons themselves are pre-fixed, and stood up to the tug test. Each wing requires an aileron servo, and a flap servo.  These are fixed to pre made wooden fixing blocks that you have to measure for, and glue to the inside face of the servo covers.  All this epoxy mixing got me quite nostalgic. 

With this excitement over it was time to source and make up make up long extension leads, thread them through the wings, and then screw in the servos themselves, after centring them with a temporary hook up of the radio.  The flap servos both need extra long servo arms, which you have to supply.  More fiddling with nylon clevises follows before the flaps and ailerons can be considered complete.  The control surfaces were commendably warp free.

Now, assuming you have enough space, you can fit the wings.  A couple of carbon fibre rods slide through built-in tubes at the base of the fuselage.  The wings each slide on to the rods, and register just behind the leading edge with a dowel in a re-inforced hole in the fuselage.  You then need to turn the whole caboodle upside down, so that the two securing cap head bolts can be fitted into pre-drilled holes equipped with captive nuts.  Turn it back up the right way round again.

You have the option, and the fittings, for either an electric set-up, or an i.c. one.  I had bought an E-Flite 46 brushless which would more or less match a Synergy 75 A ESC with BEC.  With 6 servos, I reckoned the way to go would be to ignore the BEC ( remembering to take out the red positive wire on the lead from the ESC to the RX. ).  Instead I decided to fit a conventional RX supply.  These have come on a bit since last I bought one, and I used a JR 1500 mAh 4.8v NMiH battery. That should give me a few flights before it needs recharging.  The main flight battery will be a 4800 mAh 4s1p Lipo from Kokam, or similar. I already have one which has given me three years use, and still delivers the goods.

To mount the motor, you have to bolt a preformed and drilled X mount to the rear of the E-Flite 46.  This simple job requires that you first open out the holes in the X mount slightly to accept the provided screws.  The X mount and its attached motor is then fitted on drilled stand off pillars, using long steel bolts into prefitted blind nuts, using threadlock.

The ESC needed the usual soldering of connectors on the output wires, and a Dean's Plug on the supply wires.  It was then cable tied to the ply motor box where it will hopefully get enough ventilation.

A happy evening was spent programming the Spectrum TX.  Eventually, the ailerons waggled in the correct sense, the flaps had two positions of droop, the rudder and elevator worked correctly, and the fan blew the right way round.

An appropriate pilot was ordered from A H Designs.  He will be slightly small at 1:6 scale, and will not be wearing a flying jacket, helmet, or goggles.  The poor chap has to sit under a fully glazed canopy, which he can't have open because of the noxious chemicals that he is spraying, so he will wear a sweater, slacks, and a beany hat.  He may have his boots taken off, and his trousers rolled up to get him to clear the servos just ahead of his seat.

Not a lot left to do by this stage.  The nylon clevises concerned me, so I looked for metal ones. The threaded push rods have a thread used in the States, so any replacements have to be from there.  Great Planes make some.  These need back up bolts behind to tighten the whole assembly.  A final snag was that the supplied horns proved to have holes in them slightly too small for the clevis pins, even though it was an American kit.  These were opened out marginally with the correct sized drill, and I was relieved to find that there was no slop when all was connected up.

The cowl is secured by four cap head bolts, with a washer and small section of neoprene tubing on each, through pre-drilled holes, into pre-fitted blind nuts.  I changed this slightly, preferring to fit the holes in the cowl with rubber servo grommets, and fit each bolt with a washer, and tighten it down onto the grommet.  This gave a more secure fixing.

There is a lot of wiring floating about under the large front access hatch.  This is not helped by the fact that the wings have to be refitted for each outing, and that entails 4 servo connections coming up from the bottom of a commodious fuselage, and into the RX.  I chose to fit marked extension leads so that I could break the connection away from the radio.  Cable ties were used to tidy up the wiring and keep it from snagging the rudder and elevator servos.

The canopy is described as being fixed with canopy glue.  I need it removeable to fit Cropduster Charlie when he arrives, so it will be secured with screws, although that will entail fitting a few strategic internal blocks to screw into.

Couple up the data logger and check the performance figures on various props.  First up I used a new 4270, 4S1P lipo, Flight Power Evo lite V2 (last years technology, so 25% cheaper) but rated at 20C, 85 amp continuous, and with an all up weight ready to fly of 8lbs 4 oz, and an APC 13" x 6.5", I got the following figures:

Max Current draw.  48.28 amps - well within 75 amp capacity of ESC, and only sucking about 10C out of the lipo.
Maximum power 670 watts.  This should give around 80 watts/lb, which should allow it to fly, if not sparkle.  It's a scale beast, after all, and will be flown as such.

Pick the bones out of that!

Now all I need is the right day to test fly it.  Watch this space!