Andy Blackburn
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Everything posted by Andy Blackburn
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All good advice. The only thing(s) I'd add are: There's no strength in the joint itself (see Bob's post above) so I usually just use a small amount of fast-drying PVA (Speed Bond or similar) around the edges of the root joints (i.e. near the veneer), held together with masking tape overnight. It's best to eyeball the tip incidences and if it looks as though there's a warp (sometimes but not always the case) then some or most of it can be taken out by angling one of the roots; it's more important that the tips are straight than the root, otherwise you'll need aileron trim for straight and level flight. Not usually a problem with Chris Foss wings though. Edited By Andy Blackburn on 28/03/2018 21:26:12
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Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
Looks very good indeed, and better than mine ever did. Very professional - looking forward to seeing if fly. A. P.S. - still very pink, though... -
Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
You could just declare it flight-ready and do the maiden flights like that to see how it looks. Then if you think you need a canopy, you can add one... -
Looking forward to this - someone (can't remember who) had an F.3 enlarged from Andy Conway's original plan in the 1990s and performance was excellent. Good luck with it.
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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.
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Beginner builder
Andy Blackburn replied to John B 2's topic in Gliders and Gliding - General Discussion
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: 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. 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. 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 -
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. 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: The plan shows the part the right way up The reason that the slot in N4 is higher than the centreline is that - cunningly, I thought - it will only fit one way 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
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Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
I'm sure you're right. But in my head, there is much wringing of hands... -
Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
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! So will just have to fill and make good the lovely cutout I made earlier, and move the switch one level down! 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? -
Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
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. -
Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
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... -
Middle Phase 2
Andy Blackburn replied to Jonathan M's topic in Gliders and Gliding - General Discussion
If that's on the bottom, I'd leave it be, personally. Nobody will notice... -
+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.
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> 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.
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Here's a detail of what happens at the leading edge: ...basically, you just fill-in any gaps with masking tape and draw on that. 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. 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: When the text talks about "darts", it's talking about these bits: - 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... 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
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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: Use a long, thin piece of paper Masking tape Trace the pattern multiple times (iterate) So this is a (hopefully) short thread that describes how to make patterns for the Canberra nacelles; 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. The first thing to do is to cut the paper into strips of about the size above and tape together as shown. ...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... ...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: Then do it again and you should be nearly there: ...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
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