Another Andy Blackburn PSS Canberra

[Peter Garsden]

I'm watching this with interest as I have halted mine at the wings whilst I do the Hurricane which is very nearly finished.

I agree with Andy - very good planking - much better than what I will be able to achieve I am sure.

[Andy Blackburn]

Posted by Devon Slopes on 28/07/2018 10:13:44:

Finally F11, the former right at the end of fuselage was designed when Andy thought the bottom tail region was going to be planked, so I made a new one which is round. You can see all these bits in the picture below.

In my own defence, I feel that I should point out that I'd corrected that on my own set of printed parts but obviously forgot to change the plan, which is what Sarik obviously used to generate the new parts. Mea Culpa.

A.

Edited By Andy Blackburn on 07/08/2018 08:52:38

[Devon Slopes]

Not to worry, Andy, it's a trivial piece to make.

So I pinned the supports for the tailplane in place on the fuselage. I then put the tailplane in on top, with a layer of plastic between the two. I then pinned the tailplane supports to the tailplane. Removing the pins from the fuselage then allowed me to remove tailplane and supports as a single assembly like this.

I checked the supports were seated properly on the tailplane, then put glue in the appropriate places on the supports, and re-assembled the tail as shown below. The wooden pieces on the tips make sure that the tailplane is held at the right angle (i.e. the equivalent of horizontal). Andy, if you are listening, is there any way of checking I have the decalage right? Should the tailplane be a zero incidence?

When it’s all dried you can take the tailplane off, and it looks like this. All I have to do now is block in the bottom part.

Peter, meanwhile, is making fantastic progress. We started at the same time. He started on the wings first, but completed those months ago, and has now overtaken me and seems to be almost finished. Oh, and in between he’s managed to complete a Hurricane. How do you manage it Peter? My only excuse at the moment is assembling an electric fuselage for a glider.

[Peter Garsden]

Glad to see you are making progress Devon Sloper - you are doing the bit I made a bit of a Horlicks with by gluing on the top pieces too soon. You can, however do it that way. It just means inserting the tailplanes through slots rather than from above. I did it that way because I am finishing with Solarfilm and had to cover them first.

How do I do it? Late nights and early morning mainly, having a workshop in the house which is a converted garage room, and being extremely unpopular with my other half who thinks "I am obsessed with playing with toy aeroplanes", something which has sadly slowed me down over the summer, so stick at going slowly,and carefully which you obviously do.

The Hurricane, however was a bit success, and a real hoot when we all flew together at the Orme - highly recommended. It flies like a dream, as well as the Canberra, I am sure knowing Andy's designs as I do.

Edited By Peter Garsden on 03/10/2018 18:50:00

[Devon Slopes]

No, this build hasn’t been abandoned, just that nothing has got done for the last two-and-half months due to other commitments, which included the new fuselage for an electric glider.

The wing joiner. Andy Blackburn says that “if you’re planning to play rough with your Canberra” you should go up a size in the wing joiner. Slopes Junior thoroughly enjoys his slope aerobatics, so I suspect I need to do this. The standard joiner is 6mm OD carbon tube with 4.5mm carbon rod inside it, so I’m going to 8mm OD carbon tube, with 6mm carbon rod. This means I will have to open out the holes for the joiner in the wing ribs.

Attaching the wings. I’m also wondering how to attach the wings onto the fuselage, which Andy recommends doing by tape, but says you can also do it by using a Multiplex Multilock plug and socket, but if you do so you need to make hard points to put them into. Not quite sure what this involves, but it looks like I need to work out how to do this before I complete planking the fuselage. So, I’ve dry assembled the starboard wing laser cuts parts so I can see what’s going on. It all seems to go together nicely, though you have to make another rib R4, which is easy to do using the sandwich method, with the laser cut R4s as the templates.

[Devon Slopes]

This is how I opened up the holes in the ribs for the wing joiner tubes from 6mm to 8mm. Because the side of the tube has to just touch the main spar, the centre of the new 8mm hole is offset forward with respect to the old 6mm one. So you can't simply open up the hole evenly all round. So I made two ply templates with 8mm holes made in the right place by comparison with the plan. I then "sandwiched" all the ribs together using the incidence tubes, double-sided sticky taped the templates in place and them opened up the holes using sandpaper wrapped around a pencil.

Note quite as elegant as it sounds, as a little more sanding had to be done to get the tubes in once the inner wing panels had been constructed, but more of that later.

[Devon Slopes]

Multiplex Multilocks. A decision almost made. I think I'm going to try holding the wings on with the multilock connectors. I could not convince myself that the magnets would have enough grab (the held 500 grams weight, which is less than my calculation for the likely pull); though they do work for Peter. So, here is the layout I'm thinking of. I have a ply plate that glues onto a former and longeron in the fuselage which holds the barrel of the lock, and a piece of ply in the wing which should transfer any force fairly directly to the wing spar (there is wood to go in above and below the spar, which should help further). I'm going to put the peg into the wing and then try it against a test piece to see if it works. I can't use the fuselage for the test as I don't know how deep to glue the barrel in until I've sanded the fuselage. Thoughts (as ever) welcome.

[Devon Slopes]

Structure around the incidence tubes and spar. So, here are the inner wing panels almost complete, at the stage of fixing in the spar and incidence tubes. You can see all the strengthening around the tubes Andy talks about. The incidence wires and main spar are slightly over length, I’ll trim them when I know how wide the fuselage is after sanding. You can also see the parallel lines I drew on masking tape on the building board to make sure the wing roots are parallel.

I made the mistake of scrounging the balsa which fits around the main spar from the wood which the wing tips are cut from, but then realised this must be soft balsa, and so made new ones from some other scraps from the kit. You can also see the hard points for the Multilock wing joiners (one of which has a Multilock plug in it) close to the spars. Also, I have faced the wing roots with 1mm ply. The advice is that this will protect the root from damage, but also you have to force a plastic wedge between the fuselage and the wing to disconnect the Multilocks, and I’d rather do that against ply than balsa.

And this is gluing the main spar to the bottom outer wing skin.

[Devon Slopes]

Hmm, ten months since I posted here. Most of the reason is that I decided I needed to build a 3 metre e-glider, which is now complete. Need, of course, is an interesting word when it comes to model aeroplanes, but I’m sure you will understand. The other interruption was the small matter of breaking the wing on my smaller e-glider, which involved assembling a new wing. But both these projects are done now, and in between you can see some progress has been made on the Canberra.

Of course, the world of Andy Blackburn Canberras has not stood still whilst my (limited) building skills have been being applied elsewhere. Mike Q started a build blog, which uncovered that both Scot Edwards 2 and Paul Ashford have completed models.

So, on with the build....

Mistake 4 was placing the inboard end of the aileron one bay too far inboard. I discovered this when cutting out the aileron, and fortunately had the picture shown below of what it looked like before the top skin went on. I've managed to bodge it back to be correct, but it was not my finest moment.

[Devon Slopes]

A slightly unusual view for this post. Looking from the back of the fuselage forwards, the slot being where the forward part of the tail fin will fit. This emphasises how foreshortened the picture is. To the top right is the area of the fuselage covered in the planking. As you can see the planking is now complete, and a lot of the sanding of the planks is now done. The bottom left is the tail bay area. Filling all this in felt a little as though I was making it up as I was going along, but its now done and roughly carved into shape. Now some more serious sanding is needed.

Handling the fuselage showed up the problems in my planking. Where planks had not glued to each other the fuselage would flex under hand pressure. Easy to cure though, by brushing white glue into the gaps. I was worried about cutting out the hatch, despite the marks I'd left all round the gap. So before the final planks went in I cut through the formers, so its now held in place largely by the planking.

[Devon Slopes]

Any Advice on Canberra Colour Schemes?

Progress is being made, and so I'm beginning to think about colour schemes. One of the things I learnt from building model railways is to pick things to do which lie within my modelling skills. Hence I was pleased to find that there is a colour scheme for the Canberra T4 which has all-grey wings. That should not be beyond my abilities with a spray can! But does anybody know if they were really grey, which is apparently as shown here? Or were they actually this greeny-grey shown here?

[Alan Gorham_]

The grey is light aircraft grey, a standard RAF paint colour. You can order the exact right colour from a paint supplier who offers paint to the BS381C spec. the colour to ask for is 627 Light Aircraft Grey.

[Devon Slopes]

Brilliant! Thank-you Alan, googling that spec gets to some useful sites.

[Devon Slopes]

Vacuum Forming?

Folks familiar with the Andy Blackburn Canberra will know that creating the engine nacelles involves shaping balsa sheets into compound curves (see Andy's thread on this). Having got the balsa wet, I formed the main curve by letting it dry around the vacuum cleaner pipe (hence my claim that it's vac-forming....). More seriously this was version 1 one of doing this. I found you get more curvature if you use tape as well as elastic bands, and run your fingernail along the back to pre-curve it.

Andy also describes how to make a template to get the shape right. I found that if you trace around the bottom of the keels onto a piece of paper (before you glue them on) you get a good first approximation for the edge which joins the wing.

[Devon Slopes]

 

I thought I'd better make a 2022 blog-post for this project before the year is over!  Its always been a background project to do in between other things, like the Inside F5J I've completed, or the 3D printed Eclipson Model S.  The overall weight was headed rather alarmingly upwards (or at least my predictions were), so although the fuselage is glassed and painted (though still a few coats to go) I'm going for Oracover for the wings and tailplanes. 

 

[Devon Slopes]

This "background" project which I do between other things has now reached the flyable stage.  Its still far from complete, but I want to fly it to find out if there are any problems that need to be solved before I spend time adding more details.  So, I'm waiting for the right weather when a willing launcher is available.   At the moment the all-up weight is around 1280g, so heavier than Andy's (1210g) and about the same as Peter Garsden's.  On the other hand I have the heavier wing spar, and I suspect I was not weight efficient with the structure around the multilocks that hold the wings on.  And of course details will add more weight!

[Martin Gay]

I don't think there will be a weight issue. I have seen Peter's model fly very well in surprisingly light light on the Great Orme.