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Canberra by Andy Blackburn PSS

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Peter Garsden13/03/2018 18:12:30
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As I said above, I made pin holes in the bottom sheet then joined up the dots with a line. The question is how to cut out the aileron, because one has to go through ribs cross grain. I used this very useful Tamiya balsa saw, which is very handy for all sorts of applications.

The link is here

Peter Garsden15/03/2018 08:30:48
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Last night I stuck on the wing tips (incidentally you need a right and a left wing tip as it is a 1/8 balsa 1/32 ply 1/2 balsa sandwich starting from the bottom, so don't make 2 right had version like what I did and have to almost start again), and the 1/64 ply root facings with epoxy.

With hindsight I should have used Aliphatic Resin for the wing root which grabs a lot better. Even using 20 minute epoxy it was starting to go off by the time I glued on the final wing root facing.

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In the above picture you can see the 1/16 ply insert to hold the bolts for the Aileron horn, which is good and solid

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Peter Garsden17/03/2018 19:37:38
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And so to the nacelles. It took me a while to figure how out how it all went together as there are many parts very cleverly designed with tabs, the CNC cutting very accurate. Andy - note to self - mark the plan with the part numbers shown. I think it would be easy to do. There is, however a sequence of drawings showing which order parts go together with details of the curving of the outer sheeting. There is a keel running top and bottom of the wing with formers at right angles number N1 to N10.

I decided to support the wing on blocks of foam as the keel underneath, otherwise applying pressure might crush the delicate structure

I decided to try alihphatic glue which is a wicking alternative to cyano. Less fumes but one has to pin it in position as it doesn't grab and set fast like cyano. It does,however, dry in about 15 minutes. Warning, however, it doesn't sand at all.

20180317_120717.jpg.

Peter Garsden17/03/2018 22:53:50
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1301 forum posts
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Devon Slopes18/03/2018 19:10:58
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Please keep posting the detailed pictures, Peter, I know I'm going to need them when I move on from building the fuselage to doing the wings.

Peter Garsden19/03/2018 08:22:25
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Well yesterday, I had an inert dispirited day trying to make the 3/32" curved 3D covers for the Nacelles. I made 2 paper patterns for one quadrant, and 2 attempts at a balsa shroud, neither of which worked. Andy I think I need some help here.

In the previous thread I said aliphatic glue - don't mean that I meant Super Phatic, sorry.

I read the instructions copiously, cut out a large sheet of paper to form my paper pattern, and laid it over the structure. I think the problem is that paper is too flexible. At the front, the sheet has to twist slightly to get over the front curve of the wing and down the side of the nacelle.

I marked top and bottom of the pattern on the paper and cut it out. I transferred it to balsa and it wouldn't fit. I tried again, and made another Horlicks of it. I gave up and watched the TV instead, disgruntled, and that was after cleaning the house as the trouble n strife is away, so I must be desperate!

My plan going forward is:-

  1. Use a cardboard template instead of paper.
  2. Use the wing root 1/16 ply rib I have made to mark off the top profile of the wing section and transfer that to cardboard
  3. Andy, you talked about cutting "darts" in the template, but I didn't understand what you meant. Can't remember if that is in the article from RCM&E or the building blog.
  4. I didn't even get onto the hot water soak, and rounding off with thumb nails at all.

This is probably the most difficult piece of building I have done so far - never shy away from a challenge though!

Andy Blackburn19/03/2018 10:49:57
425 forum posts
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1 articles

> 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.

Peter Garsden19/03/2018 13:18:57
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That's excellent Andy, thanks very much indeed, heartily and genuinely appreciated. Will save me from tearing what little hair I have, out.

Peter Garsden20/03/2018 20:42:39
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Just goes to show that a bit of good instruction and tips goes a long way. Last night I followed Andy's guidance, and heh presto it worked. What I wasn't doing is marking the outline several times and sticking the pattern to the wing. Still wasn't easy, but much easier.

I found the soaking of the wood with hot water really effective. I used cryano as suggested which didn't mind wet wood. Now I have to steam and bend a piece of 3/16 balsa which will be a challenge

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Trevor20/03/2018 22:24:29
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Looking good Peter! If the 3/16 fights back, you can always use two laminations of 3/32”.

Trevor

Andy Blackburn21/03/2018 10:48:40
425 forum posts
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1 articles

+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.

Bob Jennings 121/03/2018 12:07:31
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85 forum posts
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Nice one Pete, fascinating reading. I may have a go after the Hurricane build.

Peter Garsden24/03/2018 14:14:44
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1301 forum posts
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Good thoughts chaps on the sheeting. I will go for the 3/32" x 2 laminations as that will bend nicely and be stronger.

I just thought also that I would show you something which helps the paper template for the nacelle skins

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It sounds obvious but the template is 3D as Andy says and you have to snip the paper at the leading edge and trailing edge so as to avoid twisting the paper and skewing the pattern. If you don't do this, you will end up with a pattern that is too small at the front top over the sheeting/

20180324_075059.jpg

See what I mean about a gap at the top of the leading edge sheeting with the lack of a 3D perspective. The gap at the front is normal and has to be remedied by the application of masking tape to cover the space, then it works fine.

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You can see the various wedges which are covered in sellotape to stop them from sticking to the superglue

Peter Garsden24/03/2018 18:43:50
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1301 forum posts
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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.

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Andy Blackburn24/03/2018 21:05:40
425 forum posts
482 photos
1 articles
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

Peter Garsden26/03/2018 18:27:23
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1301 forum posts
888 photos

20180326_064706.jpg

We've definitely got a full extra set of parts for the nacelles. Sadly these will go into the bin.

I think that I will contact Sarik and point out the errors.

Edited By Peter Garsden on 26/03/2018 18:29:45

Andy Blackburn26/03/2018 21:53:39
425 forum posts
482 photos
1 articles

What, a complete set??

Extraordinary.

Mind you, as we have seen, getting a set of printed parts absolutely correct is a significant undertaking; I think the only way you can expect to have a decent shot at it is to cut the parts and then try a test build with the actual parts, correcting and repeating as necessary. That's what Traplet did with the Jet Provost parts, and they were almost 100% correct.

I think talking to Sarik is probably the right thing to do.

Peter Garsden27/03/2018 17:03:48
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1301 forum posts
888 photos

Thanks Andy. I have emailed Sarik and referred them to my blog. In many ways the wood pack is very good - lots of bits I wouldn't expect included and good quality machining with the name of the part printed on each one.

I was talking to Phil who said he did a beta test build with the Hurricane and he is still finding corrections. You can't spot everything. It is like editing text.

Anyway I will be adopting radio silence whilst I build the Hurricane, so you can avoid getting annoyed for a while!

I am thinking how difficult it might be to cover the nacelles in a different colour of solarfilm to the rest of the wings - not looking forward to that one. Here are the finished wings.

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