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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: Beginner builder
25/03/2018 18:05:49

I assume you mean BEC (battery elimination circuit) rather than ESC (electronic speed controller)?

Even if that's the case, I'm still a bit confused about the question; I assume that you want to know what you need (electronics-wise) to get a working model? I think it really hinges on what you're going to power the receiver & servos with, which is really about what you have available to recharge the receiver battery. The options are:

  1. 4-cell NiMh battery of (maybe) 1000-2000 mAh for a model that size (depends what will fit in the nose), and a fast NiMh charger. This has the advantage that it won't catch fire in a crash.
  2. A 2-cell LiPo of similar capacity and a separate BEC to get the voltage back down to 5 volts, and a separate LiPo charger.
  3. Some receivers and servos will run happily off a 2-cell LiPo, you'll still need a suitable LiPo charger though. This is probably the lightest set-up, but if you hit them hard enough LiPos will catch fire, so it's a question of balancing risk.

Edited By Andy Blackburn on 25/03/2018 18:07:15

Thread: Canberra by Andy Blackburn PSS
24/03/2018 21:05:40
Posted by Peter Garsden on 24/03/2018 18:43:50:

Sadly Andy, I have found another part cutting error. N4 should have a flat edge top and bottom, but the one which has been cut in the pack has a curved edge on one side. This led to me not being sure I had got it the right way up.

20180324_183301.jpg

Oh dear. That's clearly not right.

My prototype was built using parts patterns that I had laser-cut by a third party, and everything fitted (obviously). Your parts are produced by Sarik, and the fact that there are errors that were not present in the original parts set tells me that Sarik have produced their own patterns from the Canberra B.2 plan.

I have to ask - have you contacted Sarik to let them know that there are error(s)? You should really let them know, since they produced the parts that you bought and if corrections are required, it will be Sarik's responsibility to make them.

I should stress that I have no connection to Sarik, and I have no control over what they produce.

Having said that, though, I should point out that:

  1. The plan shows the part the right way up
  2. The reason that the slot in N4 is higher than the centreline is that - cunningly, I thought - it will only fit one way
  3. You can cut or sand a flat on the incorrectly-cut N4 and all will be well.

Edited By Andy Blackburn on 24/03/2018 21:06:49

Thread: Middle Phase 2
24/03/2018 10:09:32

I'm sure you're right. But in my head, there is much wringing of hands... smiley

23/03/2018 12:56:40
Posted by Jonathan M on 23/03/2018 11:32:45:

Cheers Andy!

Fair enough on the 'approved method', I'll give you that, but I'll also raise the stakes... to something really stupid that's just come to light...

i.e. this is my sketch for a white canopy against the black fuselage:

<snip>

But this is the sketch on the other side, which is bang in the way of the black switch! crying So will just have to fill and make good the lovely cutout I made earlier, and move the switch one level down!

dsc_0720.jpg

In your shoes I'd be a little concerned at weakening the fuselage by having a cut-out so close to the previous one; I'm envisaging a hard arrival into the side of the slope (I know you wouldn't do that, but one of your lesser-skilled colleagues might have to land it for you whilst you were unavoidably detained on important business elsewhere).

Had you considered putting the switch on the other side?

23/03/2018 11:15:31

Looking good, but still a bit pink-ish

> Tailplane 'cavity' insides lined with black:

...

> Which was pretty stupid really, as the whole bottom was then covered in black anyway ...

No, it's not - that's the neat (OCD) and accepted way of doing it. Or if it isn't the accepted way, I've been doing it wrong, which is entirely possible.

22/03/2018 07:54:43

I never thought I'd say this about a colour scheme that involves large areas of pink, but it looks very good. A bit, um, pink, of course, but still very good...

> @Andy, have you not heard of OCD? 🤪

Yes, and I'm also a sufferer, but I'm trying to do better - sometimes it's useful to pay attention to the detail but sometimes it's not. Personally, I find it very difficult to avoid paying minute attention to everything... smiley

21/03/2018 10:51:26

If that's on the bottom, I'd leave it be, personally. Nobody will notice... smiley

Thread: Canberra by Andy Blackburn PSS
21/03/2018 10:48:40

+1 for the two laminations of 3/32" - I did that on one nacelle, actually, works fine as long as you use a sandable glue (e.g. balsa cement).

Or you could put the 3/16" sheeting on with the grain spanwise; I did that on the other nacelle, and it works fine.

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.

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