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Member postings for Andy Blackburn

Here is a list of all the postings Andy Blackburn has made in our forums. Click on a thread name to jump to the thread.

Thread: Canberra by Andy Blackburn PSS
19/03/2018 10:49:57

> Andy I think I need some help here.

Sorry to hear that you've been having some issues with the nacelles - it is reasonably straightforward once you know the correct technique, which I've detailed in a separate thread:

**LINK**

This shows the step-by-step process, and it doesn't take long to get a reasonable pattern. Let me know if it works for you or not and I'll amend the thread as appropriate.

Thread: Canberra Nacelles
19/03/2018 10:43:39

Here's a detail of what happens at the leading edge:

img_2266.jpg

...basically, you just fill-in any gaps with masking tape and draw on that.

img_2267.jpg

At this point it's probably a good idea to mark the nacelle quadrant on the back of the pattern - the longer and thinner the pattern is, the more tolerant it is of errors.

img_2269.jpg

This is the glass-slipper moment (it fits!). It took me less than 20 minutes to get to this point.

Here's the roughly-finished item than can be used to cut some nacelle quadrant, although you'll need another one to cut the quadrants that fit on the bottom of the nacelle:

img_2270.jpg

When the text talks about "darts", it's talking about these bits:

img_2270_annotated.jpg

- they're just bits cut from the wood to help it go around a 3D curve; but DON'T cut these until the 3/32" sheet nacelle quadrant (which should be the softest straight-grain balsa you can find) is glued to the wing; if you cut a dart that's too big, just fill the gap with another triangular shaped bit of wood and no-one will ever know. I've never done this, of course, and if I had I'd pretend that I hadn't... smiley

When glueing the nacelle quadrants, the really important thing is to follow the instructions on the plan and glue it securely to the wing surface before attempting to curve it around the formers - dampen the wood a bit if you have to but don't put it under any strain until the glue has fully set. Medium cyano and kicker is very useful here.

Edited By Andy Blackburn on 19/03/2018 10:52:27

19/03/2018 10:26:03

On reflection, the original Canberra B.2 article or build blog didn't really explain how the nacelle patterns were made; as you'll appreciate, there are a limited number of words available for a magazine article and there's a limit to how much stuff you can put in a build blog before it takes every waking hour to write down...

I didn't find any particular difficulty with it because I apparently stumbled on the correct technique at the outset - the three magic ingredients seem to be:

  1. Use a long, thin piece of paper
  2. Masking tape
  3. Trace the pattern multiple times (iterate)

So this is a (hopefully) short thread that describes how to make patterns for the Canberra nacelles;

img_2258.jpg

There are the tools required to to do the job; the pencil is the softest that I could find so that it's less likely to mark the balsa.

img_2261.jpg

The first thing to do is to cut the paper into strips of about the size above and tape together as shown.

img_2262.jpg

...and then the crucial (magic) bit is to hold it in place with masking tape (run it through your fingers first to make sure it peels off the paper cleanly) and just run your fingernail along the junction between the wing and nacelle...

img_2263.jpg

...pencil-in the line (try and get it right but it doesn't have to be dead accurate), unstick it it and cut with the scissors. Then stick it on again and go through the tap-mark-pencil-cut process again and it'll look a bit like this:

img_2264.jpg

Then do it again and you should be nearly there:

img_2265.jpg

...as you can see, it's converged onto the correct cut profile. More to come in a few minutes, I'd better post this because I'm not sure how much text/photos I'm allowed per post.

 

Edited By Andy Blackburn on 19/03/2018 10:26:20

Edited By Andy Blackburn on 19/03/2018 10:26:34

Thread: Another Andy Blackburn PSS Canberra
16/03/2018 15:47:44

> Planking - advice appreciated. Well, advice is always appreciated, but here it will be particularly welcome as I've not planked before.

WRT the planking; it's true that I used a couple of little plywood guages to get the right width, but after indenting each end I tapered the planks by eye using a coarse Permagrit block - you don't really need to use a guage.

All you have to do is make sure that you leave the middle bit alone, and then:

  1. Taper the nose part of the plank till it's roughly correct
  2. Taper the tail part, again 'till it's roughly right
  3. Finally, chamfer the edges in cross-section slightly (as per one of the fuselage cross-sections on the plan) so that adjacent planks will fit together.

Then it's a matter of glueing the planks in place (assuming that you've already chamfered the edges of the formers so that the planks fit), using medium cyano, and sandable woodworking glue (Aliphatic is best) to glue adjacent planks.

It takes me a few (4-5) minutes per plank; less fastidious people might be quicker. You'll have to cut some custom-shaped planks for the last bits.

Oh, and when marking each plank for the hatch formers, make a little indent with a razor saw otherwise the pencil mark will be sanded away...

Thread: Middle Phase 2
16/03/2018 15:29:42

All looking very neat, Jon. Very nice...

A.

Thread: Canberra by Andy Blackburn PSS
04/03/2018 22:40:21
Posted by Andy Meade on 04/03/2018 13:57:01:
Double digit decimals... On a balsa model?! Come on Andy, it's PSS, not NASA!

You're quite right, I normally only work to 1/10th of a millimetre on balsa...

In my own defence, I did send Pete an email to say that I wasn't expecting measurement to 1/100 th of a millimetre. Maybe I should have added a little smiley face...

smiley

A.

04/03/2018 12:31:12

OK, so bearing in mind previous discussions about trusting the parts and paper plans expanding and contracting with atmospheric conditions, either the plan or the parts could be at fault (although I suspect the plan, as previously discussed).

I know the original parts were OK (see the original build thread) and Sarik have seen these, so they'd have to be going some to get it wrong, although it depends how they've managed the process and I can think of a couple of ways that errors might creep in.

Can you please measure the gaps between the ribs on the mainspar for me? The correct distances (i.e. as designed) between ribs on the plan are :

R4-R5 : 59.96 mm

R5-R6 : 60.79 mm

R6-R7 : 60.79 mm

R7-R8 : 60.79 mm

R8-R9 : 60.00 mm

(note that the V-shaped laser burn will make the slots a little bigger. And I'm obviously not expecting you to measure to a hundredth of a mm!)

If it turns out that the parts are correct, you can add a bit of wood to the bottom skin (nobody will know). If it turns out that the parts are wrong, I'll talk to Sarik on your behalf...

rgds

A.

01/03/2018 20:49:53

1. The very thin root rib is indeed 1/64" ply, it's not in the wood pack as the stuff is about £300.00 per square foot but if you have some lying around it will stop the wing root looking a bit tatty over time - just draw around the wing root, add some appropriate holes any old how and carefully sand it to the wing profile. If only some clot hadn't forgotten to add a note to the plan... If you haven't got any 1/64"ply, a thick coat or two of epoxy finishing resin will do, flatting with a sanding block between coats.

2. It's not strictly necessary to add some 1/8" balsa at the top and bottom of the brass incidence tubes, but if you can spare the balsa and the time (about 20 minutes) I'd recommend doing it because it will make the wing root more robust, and that's where your finger will usually hold it.

28/02/2018 14:34:16
Posted by Peter Garsden on 28/02/2018 12:14:33:

...

The carbon tube and rod arrived. I am not altogether happy with the snug fit of the rod inside the tube, but it will do.

Try giving the rod a few thin coats of epoxy finishing resin, flatting down between each coat with fine wet & dry.

Thread: Another Andy Blackburn PSS Canberra
28/02/2018 08:51:35
Posted by Maurice Lester on 27/02/2018 20:22:16:

On the subject of missing parts we are also short of two wing ribs. The plan calls for two R4 in each wing but only two are included in the kit - again extras are easy to cut if you do it before glueing the originals!!!!

Oh dear. I refer you to my previous remarks (the ones about everything being on the original DXF files)... I'll inform Sarik.

I suppose it's inevitable that on something with as many cut parts as this, there will be some nistakes...

A.

Thread: Canberra by Andy Blackburn PSS
27/02/2018 19:42:32

I've not used the Hobbyking film but I notice that Sussex Model Centre are selling Monokote - which I like - if anyone wants to do the grey/black scheme. I wish I'd glassed mine, on balance.

But if/when I build a replacement, it'll probably be Monokoted...

BTW, quick reminder about the wing joiner - all will be well as long as (before glueing the outer tubes) you make sure that the aft part of the root ribs are flat on the board and the dihedral on both sides is the same...

Edited By Andy Blackburn on 27/02/2018 19:50:12

Thread: Is It The Tank Position?
25/02/2018 12:49:48

It might be the tank position...

But I've got an MVVS .49 and it does seem to be quite sensitive to fuel type; it runs fine on 5% nitro with 20% castor, but doesn't seem to like anything with a significant proportion of synthetic oil in it (tried 5% and 10% nitro, both equally unreliable). No idea why, maybe it's a viscosity thing? Or something?

Might be worth changing the fuel. Just a thought.

Thread: An Introduction to the PSSA 2018 Mass Build Project
25/02/2018 11:14:44

I was thinking about the clasic EG-N airfix scheme:

airfix-burma-hurricane.jpg

...but am really wary of the plug-in cannons. I might have to find an attractive burma/india MkII that has machine guns, I think there are a few in the one of the Osprey books.

Also, the MkIIs had (as well as a very slightly longer, very slightly re-profiled nose) an oil collector ring just behind the spinner; this will be draggy but I'm not sure I'll be able to leave it off. Maybe a bit of thick acetate with just the edges painted...?

Thread: Another Andy Blackburn PSS Canberra
25/02/2018 10:42:41

The jigging part on the picture above should have been part of the keel pieces; I'll add it to the list for Sarik.

Also, it looks as though the K6 pieces are cut from 1/4", but on the original (and on the first set of cut parts) they were 1/8" - as shown on the first page of the prototype Canberra build. But on the DXF files that were sent to RCM&E & Sarik, some fool (me) had somehow moved them to one of the 1/4" parts sheets. I think this was because they've always been marked on the plan as 1/4" parts, even though they weren't.

Please accept my sincere and abject apologies, and make yourself a couple of new parts from 1/8" sheet using the laser-cur parts as a pattern. And don't forget to add the servo mount (K6A) before glueing to the fuselage, otherwise they'll probably break as you're sliding them into the former slots - they're long parts and have a weakpoint where the servo goes. And don't forget that left and right K6's are mirror images - not that I'd make a mistake like that, I just made a spare in case it was needed. Ahem.

> And don't worry about "teaching granny to suck eggs" Andy, this is my first from-the-plan build, so any advice is welcome.

Then I admire your courage at choosing such a complex build for your first attempt! smiley

P.S. - your K7 pieces on the back of F10 look fine, although the original intention was to have them go right to the edge of the former. But what you have will be fine, it't only there to make sure that the stabiliser goes in the right place. It might look a bit confusing on the re-drawn plan because it looks as though it's showing the stabiiser - it isn't, the K7 parts are in the right place.

 

Edited By Andy Blackburn on 25/02/2018 11:02:14

Thread: An Introduction to the PSSA 2018 Mass Build Project
25/02/2018 09:40:51

I think I might be doing a Mk II with a tropical filter, possibly with a SEAC (India/Burma) colour scheme. Not sure about the wisdom of having cannons though because they'll have to be knock-off and will probably spend most of their time knocked-off in the long grass.

Thread: Hurricane colours, photos, video & scale references
25/02/2018 09:36:22

...and that's what comes of not paying attention to which window the text is going, first thing in the morning. Needless to say, that last post was intended to be a PM. Apologies... smiley

25/02/2018 09:33:30

Hi Peter,

I assume that your copy of "the Hawker Hurricane" is in good nick? Hypothetically, how much are you asking for it?

rgds

Andy Blackburn

Thread: Another Andy Blackburn PSS Canberra
23/02/2018 21:09:11

OK, so I've emailed Sarik Hobbies to alert them to the issue. Obviously, I haven't seen the wood pack that Sarik have produced, so I obviously have no idea what's present and what's not, or if there are any other issues.

I sent Sarik all the DXF files for the parts that I used to build the prototype model, including the changes that were made as the prototype was built; I don't know what relationship the final wood pack has to my original parts patterns, I'm afraid - sorry.

23/02/2018 20:20:33

Well, I'm pretty sure they were both on the original DXF files. I'll email Barry at Sarik.

23/02/2018 11:23:59
Posted by Devon Slopes on 22/02/2018 18:27:08:

The balsa does not quite match the plan - but this is not a complaint, the kit is really nice - just a warning to other builders to make sure the two keels are the same length (whatever that may be).

I also sanded off a certain amount of the "cinder" from the laser cutting process from the scarf joints where the halves of each keel join, and where the formers slot into the keels. The down side of doing this is you have to be careful not to significantly change the shape of the slots, but the upside might be that the glue joint will be better. Does anyone out there know if this is helpful?

If you look on the original build thread, about half-way down page 1, you'll see that I also had a similar problem with the parts not quite matching the plan; there were two reasons for this:

  1. The first set of parts that I had made (by SLEC) were exactly as the plan but the laser cut isn't vertical - it's V-shaped, and is typically 0.7-0.8 mm wide at the top for 1/4" sheet. I corrected the laser parts patterns by adding a kerf of about 0.3 or 0.4 mm (memory is hazy) and just used the original parts by arranging them on the plan (see below) in about the right position, checked that the fuselage former at about F6 would still fit, pinned them down and stuffing bits of 1/32" balsa squashed into a v-section into any over-large slots in the keel. But I hope Sarik are using the corrected parts - I know that they have the DXF files, and from the picture it looks to me as though they are.
  2. The laser-cut parts will be the right size, but the plan, having been by pulled through a large print machine using a roller which will typically be subject to a small amount of slippage, might not be printed at 100.0% the correct size, and then the finished print will be subject to differences in temperature and humidity, so it'll change size anyway, and what's delivered to you will generally will be a slightly different size to what it should be. This has happened since time immemorial. Or, more accurately, since the invention of paper.

What you're seeing is probably a product of the plan not being the right size. Balsa doesn't change in size with temperature and humidity anything like as much as paper - Trust the parts.

On the "sanding away the cinder" thing, that depends on how you've done it. If it's to make the keel parts fit, and if you've done it carefully so that the sanded edge is exactly at 90 degrees to the face of the keel, then that's a good thing and in fact you have to do this with the keel parts (same applies to the fin, rudder and tailplane parts) for the reasons outlined above.

(The easiest way to do this is to hold the part on a cutting mat with a slight overhang, and then use a Permagrit block - which has 90 degree corners and a smooth bottom face - very carefully to true-up the edge. Sorry for teaching granny to suck eggs but it occurs to me that people who haven't done this before might find it useful).

But I wouldn't do it with anything else, though, unless you find that you have to do it - for instance, before planking or covering the fuselage when you have to sand it so that the edges of the formers fit the outer shin properly.

I should also point out that some of the keel slots are already intentionally a little bit big so that there's a little bit of wiggle room in getting everything to fit. Also, some of the supplied balsa might well be a few tenths of a millimetre under or over the nominal size (this is quite normal for balsa, although ply tends to be a bit more consistent) so having the slots over-size is usually a wise move. It doesn't seem to affect the strength of the overall component in any practical way - if you pile it into the side of the hill at high speed it'll still come apart in the same way, but mine hasn't (yet).

 

Edited By Andy Blackburn on 23/02/2018 11:34:32

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