Canberra by Andy Blackburn PSS

[Peter Garsden]

For those who were following 2 slides back, don't. I have realised that it is going to be very difficult to put the tailplane brace in, now I have glued on the top blocking, so best to glue the tailplanes, and top blocking all in one go once the blocking has been shaped - also you can't get the blocking of the underneath of the tailplane until you take the fuselage off the board.

Also showing the 3D printed air intakes that John Hey kindly made for me - some covering also now on - hoping to bring to the Orme.

[Phil Cooke]

love the intake detail Pete! Super stuff!

[Andy Blackburn]

That does look like a nice set of turbine blades!

However, bear in mind that my engine intakes were flat so would very probably have had lower drag, if you find it's an issue then I recommend the use of an acetate disc with a small circular hole cut in it for the starter fairing - you'll still be able to see the intake detail but the air won't.

[Bob Jennings 1]

Nice one Pete! Can't wait to see it in the film!

[Peter Garsden]

Thanks, again, for the tip, Andy - will see how it flies at the Orme, then adapt if necessary.

Have managed to cover the wings, tailplane and fin at the caravan. Just the fuselage to finish next week.

Oh and covering the nacelles was nowhere near as difficult as I feared. Did it in 2 pieces quite easily.

[Piers Bowlan]

Very nice bit of covering there Peter, which one are you using, Hobbyking film? Apologies if you already said somewhere earlier in the thread.

[Peter Garsden]

Thanks Piers. I am using Solarfilm which is still available on their own site now. I think they are still supplying the punter rather than the wholesaler and selling off all remaining stock. I find Solarfilm easier to stretch but not as removable as Oracover.

Back to the fuselage - have now finished planking. I just don't think I will finish by the weekend so it may be the Hole of Horcum before I am done.

This also shows the amazing sanding tool Andy suggested which works a treat

1. 120 grit sandpaper
2. 2 Layers of thick cardboard from an A4 pad.
3. Lay the sandpaper oversize on the fuselage and tape it down.
4. Contact adhesive through out one piece then the final piece, then an outer layer of sandpaper to aid grip.
5. I used a permagrit file to file off the proud sections then this tool to finish off - excellent

[Peter Garsden]

I have made the hatch for underneath the fuselage. So for pointers:-

1. I didn't realise that one has to cut through the former in the middle as well as the outer formers which meant I couldn't get it to release at first.
2. I used 1.5mm x 6mm magnets and indented them into the edges.
3. I made some facings out of 1/32" ply for the 5mm carbon rods which are needed to stop the hatch falling off on landing because it is underneath the fuselage.
4. As Andy says in his article you need a screwdriver to prise the hatch off.
5. 4 magnets seem fine to hold it in place.

I had 2 sets of F4A formers so used them at the end to double up the sides of the hatch

This photo does not show the ply facings I made for the dowel holes

[Peter Garsden]

Now back from the weekend and hoping to finish the Canberra by the Hole in Horcum event next weekend. If not, then it will definitely be ready for the Orme Meeting in October.

I thought long and hard as to whether to attach the fairings before covering or after. I decided that it would be a lot easier after covering because of those nasty edges. I thus marked up the position so that I can line up the Solarfilm with the red stripe down the side. I am hoping to do the top white in one piece first because dark colours show up under light colours - particularly blue under red.

I am going to make a cardboard template for the stripe. The foam cradle definitely helps a lot.

The holes in the middle, by the way are for the central carbon spar which must not impact the balsa so is oversize, a hole for the servo lead, and finally a hole for the Ideal models wing retainer plug - don't know if I will be able to get to it from inside the fuselage. We will see.

Edited By Peter Garsden on 15/09/2018 09:26:58

[Peter Garsden]

I also decided to make the whole for the canopy and pilot. Don't make the same stupid mistake as I. I marked out the canopy without realising that the fuselage was vertical - it is round, so insert the fin first and line it up! I cut it out then had to glue it back again, when I realised that the spine was not in the middle. It has to be cut out to make way for the pilot

Top tip - use high quality nail scissors to cut out the canopy. The bent forks make sure you don't cut into the pattern as long as you point them away from the direction of cut. These are Fiskars.

Then one has to make a cockpit floor out of 1/4 to get the pilot in the right position.

Obviously make it in 2 pieces because otherwise it won't go through the hole. Tricky to get it to fit inside the curve.

[Peter Garsden]

So to covering, and how to put on the Solarfilm so that the colour scheme lines up. I made a template out of cardboard. I already had cardboard templates for the wing root - comes of it not being included in the woodpack, so I thought that I should:-

1. Break with tradition and cover the top first because it is white. If you start with a dark colour it shows through light colours, as I discovered with the dark blue.
2. I laid on the white beyond the cut line then pinned the template to the sides using the wing joining wires to line it up, and then cut it back with a new scalpel blade. If you use anything blunt it rips and makes a mess.
3. I will next lay on the red stripe, then finish by lining up the blue, again using the cardboard template. It will be a bit tricky. I will lay up the blue underneath in 2 pieces

[Peter Garsden]

Not quite finished but thought I would post a sneaky assemble. Lots of things to finish like the canopy to glue on, instrument panel to print off, horns to make and attach out of flbreglass sheet, fairings to fashion etc

And a big thank you to Andy for pointing out that I had the canopy the wrong way round. Now corrected quite easily without a lot of hacking

[Peter Garsden]

Last bit now then nearly home - aiming to maiden at the last PSS event of the year in October **LINK**

There are parts of this build which are really easy and satisfying despite publicity to the contrary eg the planking, and parts which are tricky - eg the fairings, which I have ummed and ahhed about. Andy recommends inserting bits of thin balsa between the root rib and the fuselage, but this is tricky.. One then releases the root rib tack glues spots from the wing to leave the fairing in place and remove the wing.

The problems are that:-

1. I covered first wtih film which was a mistake as one gets glue all over the fuselage.
2. I didn't make pieces deep enough at the trailing edge which means I have had to heavily fill afterwards with talcum powder filler.
3. The second wing I am using the cardboard template I made for the root rib (not included in the wood pack, which works much better.
4. It is still tricky to hold the pieces in place and the wing on whilst inserting pieces because this can push the wing away from the fuselage.
5. You have to chamfer the balsa to accept the curve of the fuselage to fit which is tricky. I know Tom Cooke was worrying about this bit of construction, I have to say with good cause.

The handy balsa trimming tool Andy made and shows in his article works really well - a blade glued between 2 pieces of 3mm balsa, but I think you could us 2mm? What did you use Andy?

Edited By Peter Garsden on 30/09/2018 07:42:10

[Peter Garsden]

I have found a Canberra cockpit layout which I have printed on photographic paper as usual, but it cannot easily be seen but hey ho. Here is what I found. i reduced it to the correct size by measuring the bottom length. I use Adobe Fireworks.

[Andy Blackburn]

Posted by Peter Garsden on 30/09/2018 07:40:34:

The handy balsa trimming tool Andy made and shows in his article works really well - a blade glued between 2 pieces of 3mm balsa, but I think you could us 2mm? What did you use Andy?

I just CA'd a new scalpel blade to the bottom of a piece of thick balsa (like, 1/4" or 3/8" ) so that it could be easily held, then just ran the resulting tool along the wing surface (that is, the blade is in contact with the wing surface) so that it cut through the soft balsa that had been stuffed into the gaps.

BTW, I'm a bit puzzled by the problems you're having with this bit, I thought it might be the worst part but - for me - it turned out to be quite straightforward. Here's what I did, from memory:

• Tack-glue the ply root facings to the inside of the wing ribs with tidy dots of CA or balsa cement - can't remember which.
• Install the wings on the fuselage and glue the root facings to the fuselage where they touch the fuselage.
• There'll be a gap at the trailing edge, stuff a small (but sightly oversized) bit of medium balsa into the gap (wrap some sandpaper around the fuselage to get the right curvature so that you have about 6-9mm of balsa supporting the TE of the ply root facing.
• Cut the bit of supporting balsa to the right profile using the tool.
• From now on it should be plain sailing because all you do is repeat the following until there are no big gaps left: find a short (2-4 inches) gap, sand a chamfer on a slightly oversize bit fo soft balsa, stuff it in the gap (squashing with fingers if necessary), tack glue it to the root facing (because we don't want glue mess on the fuselage), cut it to profile with the tool, then glue it in place properly.
• Run a new blade between the wing root and ply root facing to separate them, and then remove the wings.
• Fill in the inevitable small gaps with filler.
• When dry, sand and cover quickly in case one of your mates comes around an makes an unkind comment about all the filler.

HTH

A.

 

 

Edited By Andy Blackburn on 30/09/2018 11:28:15

[Peter Garsden]

Thanks Andy - I did all of this apart from gluing the wing root to the fuselage, which was a bit obvious when I think about it, and would have helped a lot. Just goes to show how just a small obvious missed step can make all the difference.

[Andy Blackburn]

Posted by Peter Garsden on 01/10/2018 08:12:23:

Thanks Andy - I did all of this apart from gluing the wing root to the fuselage, which was a bit obvious when I think about it, and would have helped a lot. Just goes to show how just a small obvious missed step can make all the difference.

Ah! ... Well, that might do it.

Colour scheme starting to look very nice indeed, BTW.

[Peter Garsden]

Have come across a problem chaps. The elevator servos are in as per the photograph. I made up a Y Lead and connected it, then tested it expecting the servos to both move in synchronisation, but they didn't, obviously. They move in opposite directions.

I don't want to turn one of the servos round, so what should I do? I tried V Tail layout but that also move the rudder servo, obviously.

How can I make the servos move together in synchronicity both together to operate the elevators at the tail?

Do I use 2 channels - I could use separate channels and make them both elevator - that way I could reverse one of them if necessary?

Any ideas anyone?

[Phil Cooke]

I think you have 2 options Pete - use an inline servo reverser cable with the Y lead into one channel or (better solution) is to use a programme mix on your TX with a 'Master and Slave' channel set up - the 'slave' servo will follow the master channel (elevator) - you can get rid of the Y lead then too so a neater solution!

[Andy Meade]

Back when I was using Futaba kit on the A10, I had a similar problem, and solved it thus:

• use the vee tail mix
• in the mix menu, bring the rudder movement down to zero, so the rudder stick has no affect on the elevators
• mix channel 8 (or any free channel of course) to rudder

ét voila. It's sort of a blend between Phil's and your solution Pete, as I found there was a limitation in the crow braking system which would not drive the second mixed-in elevator in the "elevator compensation" part of the crow braking menu. Anyway, tis another way round, your mileage may vary depending on TX.

Edited By Andy Meade on 03/10/2018 08:56:26

[Andy Blackburn]

On the prototype I had the model set-up with two elevator servos exactly as Phil describes above; the only time you need to use a Y-lead is if you haven't got enough channels.

BTW, I also used one channel per aileron so that it was easier to adjust them, so there were a total of 5 channels used:

• Left Aileron
• Right Aileron
• Left Elevator
• Right Elevator
• Rudder

+ a small amount of aileron-rudder mix as described in the original article, and I think I had about 2:1 aileron differential. Also a small amount (~10%??-ish) of expo to get all the surfaces back to a linear movement with the sticks. Might also have had a little bit extra expo on the elevator because you don't need very much movement at all - it's quite a short-coupled airframe.

HTH

[pete taylor]

I've taken to using separate elevator servos quite often recently and have found that the simplest way is to use a servo reverser on one side.

Neat, reliable and works as decribed.

[Peter Garsden]

Thanks chaps, for such a wide variety of solutions. I have tried out the programme mix version and found it the most ideal. As I am not using flaps, I have plugged one elevator into channel 5 and reconfigure it to elevator. Works a treat. This also enables me to trim each elevator separately for throw, sub-trim, and so on. Many thank yous all. Just to show you are all watching.

Take your point on Crow Andy - will check out my spoilerons to see if it is a problem. If necessary I will adopt the V Tail solution. That was my first thought, but I didn't fiddle around. What I was worried about was if I turned down Rudder to Zero, would the Rudder channel still work.

Anyway I can experiment.

See you all at the Orme in just less than 2 weeks.

[Peter Garsden]

The separate channel solution works a treat chaps. Thanks. All now connected up and working perfectly in synchronicity.

Another question for you bright (old?) things. Andy specifies the following in his article

Ailerons + 10mm/-17mm - not a problem as I usually dial in Aileron Differential

Rudder +/- 27mm - again not a problem

Aileron Rudder mix - add 3mm of rudder with aileron - again not a problem as I have a programme for that - done - mixing channels

Elevator - +5mm/-7mm - not a lot. Andy explains that it is very responsive - presumably because of the long moment arm because the elevators are quite small. He also explains it needs more down than up because of the dihedral on the tailplane which is quite marked.

The question is - how do I dial in some differential elevator movement.

I understand I could do it mechanically by raking the servo horn either forwards or backwards, but I don't want to do that as I have already set them up at 90 degrees and would probably have to dismantle the snakes - I might have enough movement on the screw adjustment.

Does one use the throws using something I never use if I can help it ie End Point Settings?

Thanks Chaps, your last answers were really helpful.

Incidentally if anyone is building the Canberra and doesn't have the article, I have a pdf copy I can email you.

[Phil Cooke]

For small refinements like this - I personally think its best to build with mechanical symmetry and make the refinements in throws using the Servo Travel Adjustment feature on your Tx. You should easily be able to allocate +5mm and -7mm with a little bit of effort in that particular function (Im assuming you're using a Futaba set up - other systems may use a different term for the same feature?)