One ninth of a Canberra

[Phil Cooke]

Very nice Scott - making rapid progress on this one

The raspberry ripple scheme that Matt was referring to was the classic Red, White and Blue of the Empire Test Pilots School at Boscombe down, various marks of Canberra have flown in these colours, either as ETPS or Royal Aircraft Establishment airframes - heres one example;

**LINK**

Edited By Phil Cooke on 20/08/2015 22:33:45

[Steve McLaren]

Yes super speedy! But it looks very neat too. Are you aiming for a particular deadline Scott? The Bwlch must be achievable at this rate - no?

[Peter Garsden]

Thanks for that explanation Phil - for the ignorant non-plane spotting trousered amongst us. It is only since joining PSSA that I have learned what a Canberra was, since seeing Simon's take to the sky. Just goes to show that I had a miss spent youth! If it flies anything like Simon's it will be splendid.

[Scott Edwards 2]

Got some major wingage work done over the wet weekend. The wing is really nice to build, and the accuracy of Andy Blackburns' plan is astonishing. The flat bottom means you can weigh it down and build it really accurately. The only tricky bit is getting the wing spar/joiner holes aligned which dictates the dihedral.

I've got a dihedral difference of 3mm between wingtips, but at this scale, heck ! I can live with that.

As for a finishing deadline - SEPTEMBER ???!!! hahahah very funny Steve. Next March is more like. I've learned from previous projects that getting the basic balsa airframe finished is still only a fraction of the overall timescale.

Picture of all the bits and pieces below, it reminds me of the Eric Morcombe quote - All the notes are there but they are not necessarily in the right order !

 

Edited By Scott Edwards 2 on 24/08/2015 12:26:31

[Andy Meade]

September it is then!

[Phil Cooke]

Your rate of building Scott is astounding though, regardless of when you put the finishing touches to this machine.

Pete I think I'm going to have to lend you some history books!!

[Scott Edwards 2]

Wet bank holiday weekends are what aeromodelling was made for eh !

The wings are now fully skinned, and the fuselage is in one piece. The fuse is round of course, and the wing roots are flat, so there is that gap between root and fuse that would normally require a stub-wing of some sort.

I've tried an alternative method that seems to have worked quite well. I damped some 1/8 balsa, and moulded it around the fuselage side and taped the edges down. Then mount the wing, and fill the gaps between the wing root and the 1/8th sheet with scrap balsa & PVA. When dry, remove from the fuselage, trim the excess 1/8 sheet away and then sheet the wing as normal to the edge of this curved 'false' root. You end up with a lovely curved wing root that mates to the fuselage perfectly. I was rather chuffed ! When the fuselage is covered, I will use the car body filler trick, and the fuselage/wing root joins should be almost invisible.

[Scott Edwards 2]

Isn't it nice when you get to the point when you can assemble a model for the first time !

About 90% of the balsa is now bashed. Nose piece, wing tips, curved fin leading edge and nacelles to go. Lots of filling and making good required though. I managed to put my thumb through a wing skin just for good measure as well grrrrrr....

The only tricky thing so far, is that the fuselage is round, so rolls about like a cold sausage on a paper plate at a party. The tail alignment went OK though ! When I built one fuselage side, I put in a hard balsa strip on the central datum line where the base of the tail sits. It was therefore a case of hacking slots in the fuselage so I could slide the tail through from one side and sit it on this datum strip.

Not that far from covering now. The fuselage is bit thin in places (my planking skills still leave much to be desired) so that's going to be glass cloth and Poly-C or equivalent. All other surfaces will be tissue and Poly-C.

I've had a weigh in too. The whole lot in these photos comes in at 2620 grams , nicely under 6lb which I'm quite pleased with. My target is 10lb all up, plus 2lb nose weight, so I'm on target (ish)

Only bit I'm not looking forward to is making the canopy plug, but Matt Jones Vixen log has really given me some fabulous ideas on that, but that's months away !

[Matt Jones]

Scott, that's a thing of beauty

[Andy Meade]

A man of taste and sophistication, flying his PSS models with a rudder

Looking nice Scott, lovely bit of shaped tree there.

[Phil Cooke]

looking great that Scott!! top work!

[Andy Blackburn]

That doesn't look bad at all, Scotty!

[Martian]

smashing work am going to follow this with pleasure

[Erfolg]

I am in awe, in approx. 1 month a pile of balsa has morphed into a model. The model itself is worthy of commendation as to the build quality, which is emphasis the difference to us balsa butchers and a craftsman.

I can only be thank full that i have not been cursed with the skill stick, as I would not have sufficient space to keep all the models. Just imagine the curse, like Midas, 6 models a year, rooms packed floor to ceiling.

Very well done, a commendation is warranted.

[Scott Edwards 2]

Craftsman ? Me ? Oh bless you Erfolg, I know people who would roll about laughing at me being described as a craftsman haha ! I am in truth a very very average basher of the holy balsa bush. Take a look at some of the stuff that Matt Jones or Andy Blackburn produce, now THATS craftsmanship. My aim is to build simple practical flying models using basic techniques, and also to prove that if I can do it, then really anyone can.

Anyhow - progress update ! Covering has commenced, and Austerity covering it is too. Big stuff can be a money hoover. 12 rolls of Profilm ? That's two hundred pounds sir. Glass cloth is 6 quid a square meter, plus epoxy at 15 quid a pint too. Yikes !

So what's the alternative ? Acrylic varnish and tissue. I like Poly-C, but that's £20 a litre. As far as I can research, Poly-C is 'Minwax Polycrylic' made by Ronseal and is the same stuff as their Interior 'Diamond Hard' Varnish. I've used both, smelled both, tasted both (yuk) and damned if I can tell any difference ! The Poly-C guys say they've added a magic ingredient, but that's possibly a drip of PVA if anything.

So - you can get a large tin of the Ronseal stuff for £25, decant it into 1 pint milk bottles and that's the equivalent of Poly-C at half the price. Bonus !

Tissue is, gulp, 30p a sheet ! Do these people think I'm made of money !!!!???

Pic of Scotts Austerity covering kit below. £30 quid all in. The brown sheet is 'Tufnel' from directplastics.co.uk Amazing stuff, tough as nuts and easy to work with. From one sheet of that you can cut about 50 bespoke surface control horns for tuppence ha'penny hahahah I love this hobby

[Scott Edwards 2]

Doesn't look much different to last time, but lots of the fiddly bits are now done. Nose and tail are shaped, all the waggly bits are cut out, faced and prepared for hinging, the servo cables are in, the fin leading edge shaped and glued in place and lumps and bumps filled in !

The fuselage is covered from the fin forwards, but needs a few more coats of Varnish before rubbing down ready for primer. I have to admit that I used glass cloth for the forward fuselage. My planking was a bit rubbish in places and I had thin patches, so I sucked up my pride and resorted to 34gsm cloth for added strength.

Keen eyes will spot the obvious lack of engine nacelles !! Andy Blackburn, he who designed the half sized version of this thing, is currently updating his plan, and knocking me up a set of double sized nacelle plans ! Bless him. The idea is to use a central crutch with formers, and then plank over the top. Should be nice and light.

I keep an eye on weight as I go, my local slope is a bit girly, so things have to be kept really light. Everything in these photos, is a smidge under 7lb which I'm pretty chuffed with, and nicely aiming for that 12lb AUW target.

[Matt Jones]

Now that is a lovely looking model, nice work and proper (i.e. wood) building. Definitely craftsmanship in my view

[Mark Kettle 1]

Nice Scott .

[Andy Blackburn]

Nice - in fact, very nice.

Nacelle formers and crutch are almost ready - read yer email!

A.

[Scott Edwards 2]

Met up with Andy B last week. He's updated his plan to add a crutch & former based nacelle design. Not only that, but he doubled it in size for me and printed it out ! Added to that he printed two copies, one to slice up and one for reference !!! He also bought me lunch What a thoroughly top chap ! Triple win.

I haven't built many models from plans, but I've done enough to know some are bl**dy inaccurate. Even CNC cut plans I've done have had big margins of error. Andys stuff is flipping micrometre bang on though. You don't need to do any second guessing, just cut it out and you know everything will fit perfectly.

The nacelles are 32 inches long, so it's a bit like building two small fuselages. However, a quick appointment with Mr Bandsaw now sees me with a kit of nacelle parts to crack on with later this week ...

[Andy Blackburn]

I notice you've cut the bottom half of the top keel off as a separate piece. Was this where Mr Bandsaw got a bit enthusiastic, or was it done so that the grain direction is more manageable? Do it need to alter the plan?...

Edited By Andy Blackburn on 21/09/2015 13:28:12

[Scott Edwards 2]

Alas no, that was in fact "une up de cock". Ahem. My basic failure to be able to read a plan properly. Thank you for highlighting this fact publicly on my behalf hahaha

A bit of selotape & PVA and bish bosh let's all pretend it didn't happen

[Steve McLaren]

Hi Scott. This build is looking fantastic and still coming along at an amazing pace.

But you aren't showing us much of the detail, and so I have a question which has been niggling me since you first showed the finished wing. For those of us who have never built a wing longer than a single piece of balsa:

You seem to have butt joints in the wing skins at the rib which will be in the middle of the nacelle. There didn't seem to be any internal lap plates, so will you be fitting a bandage type joint externally before you build the nacelle on top?

[Scott Edwards 2]

Jolly good question sir. The main spar is hard 1/4 balsa with a 1/16 ply plate bonded to it that extends slightly into the outer section of the wing. The primary strength comes from that. Where the inner panel of the wing meets the outer tapered panel is a double thickness rib (2 * 1/18 balsa) so the butted sheets overlap half of this double width rib. There is no bandaging or internal reinforcement.

I'm of the opinion that we massively over-engineer these things, and we instinctively build them to survive a crash rather than to fly. I've crashed many powered ARTF sports planes and always dissect them to see how they are built. Their minimalist structure is astonishing, and the wood is generally cr*p too. I've yet to make one fail in flight, and damn I've tried ! Similarly with foam wings, stick an old Acro Wot wing between two chairs and sit on it - you will be amazed how much it can take.

Here's a question (I don't have a clue what the answer is) A 5Kg PSS model with 100 dm2 of wing is dived vertically from silly height to say 30 m/s and then given 45 degrees full up elevator - what is the maximum instantaneous force on the wing at the root ? I suspect it's actually not greater than the 5Kg mass of the plane ?

[Steve McLaren]

You are right Scott - I certainly build mine for the crash case - but there's a good reason for that!

Interesting exam question you have set there! I shall ponder it while sitting on the beach tomorrow. My feeling is that our models are quite capable of pulling 5 or 6 'g' on the elevator like the full size stuff. What sort of radius of curvature do you think this hypothetical model will achieve? Maybe 10m at 30m/s?