Martin Harris - Moderator Posted March 8, 2021 Share Posted March 8, 2021 A recent thread invited memories of first RC models. In the course of checking my facts, I looked up the Sterling Models Cessna 180 that introduced me to the joys and pitfalls of radio modelling over 45 years ago and discovered that Outerzone has downloadable plans and even cutting templates for the ribs and formers. Cessna_180_45in_oz4984.pdf1.69 MB · 5 downloads (Lower resolution that the actual download) Tucked away in my loft, I still had the pressed steel nose cowling that I never got around to fitting. I have unfinished business with that Cessna - to cut a long story short (see the "memories" thread if you want the gory details!) the total flight time was in the order of 2 seconds - so in the spirit of many a full sized Spitfire "restoration", my plan is to rebuild my first radio model from the cowl piece backwards! To drag the model into the 21st Century - and give it half a chance of outlasting the original's (sorry, rebuilt model's previous) total flight time, my plan is create an additional single channel/blip throttle flight mode to give me the best of both worlds with modern radio on 3 channels. This will enable trimming flights with the ability to simulate the handling with the MacGregor single channel equipment fitted for the ill-fated maiden flight. An option might be to build a reduced dihedral wing with ailerons but at this point I'm preferring to stick with the spirit of the original design. I've never published a build blog before - finished project photos hide a multitude of sins - but I'll bite the bullet and risk exposing my workmanship to ridicule as a spur to get on with the job. 2 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 8, 2021 Author Share Posted March 8, 2021 In the best traditions of Blue Peter, here are the downloaded templates, pasted to appropriate sheets of balsa and ply that I prepared earlier: Next will be the rather lengthy process of cutting out the parts so the next update will take a little longer. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted March 9, 2021 Share Posted March 9, 2021 Ah, that's what the piece of metal is, thought it was a Moderators knuckle duster. ? 1 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 9, 2021 Author Share Posted March 9, 2021 Let that be a warning to any hecklers! ? 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 9, 2021 Author Share Posted March 9, 2021 Had a coffee break from gardening duties and made some holes with a scalpel - beats digging them with a spade! Removing the fiddly bits before cutting the parts from the balsa sheets should minimise breakage. 1 Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted March 9, 2021 Share Posted March 9, 2021 This is a great thread Martin. Spurred on by another great thread. I think this, and 'The Dark Nights Fix Up' are far more responsible for the balsa shortage than wind turbines! Good luck, I shall enjoy watching this unfold. I certainly won't be ridiculing; let he who is without sin and all that... Graham 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 10, 2021 Author Share Posted March 10, 2021 Well, my cutting arm is a bit sore now but the "kitting" stage is progressing well and I've certainly broken the back of the job with a combination of traditional scalpel cutting and the aid of some power tools. The ply parts are all done and I'm down to the last few sheets of the balsa parts. I vaguely remembered that the fuselage construction seemed quite complex (the main reason for the very bodged "repair" after the disastrous first flight) and it's surprising how much goes into the structure of this little model. If you've been following the story, you might notice that an engine has crept into the picture. Yes, it's the very same Enya .09 that hit the ground a millisecond before the rest of the model. I haven't decided whether to try using it - an .09 is at the bottom end of the power range and it might be a bit raucous in these noise sensitive days. I think a .15 might be a better choice. With an astounding lack of foresight 45 years ago, I must have discarded the undercarriage which is described as spring steel. I think my best bet may be to lay up a carbon fibre one although I do have vague thoughts of using a cheap steel rule from Poundland which appears to be made from spring steel. 2 Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted March 10, 2021 Share Posted March 10, 2021 Respect to your patience Martin, that's a fair old pile of balsa Matey. D.D. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 10, 2021 Author Share Posted March 10, 2021 Tell me about it Dwain! I do have a labour saving technique for shaping the ply and thicker balsa parts. After quickly cutting them out without attempting to shape them, I remove any notches from balsa parts and then use my table sander to trim them to the line. Although a vicious tool, capable of sanding inches per second from balsa, it’s very easy to control and gives the benefit of perfect 90 degree edges. The attached video was filmed trimming 1/8" birch ply using just one hand instead of both, as per normal which gives finer control - I needed one to hold the camera. Sanding.mp4 2 Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted March 10, 2021 Share Posted March 10, 2021 An Excellent tool, I have one myself, with a smaller wheel and a belt on top. Good when getting laminated blocks square, for motor mounts. D.D. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 11, 2021 Share Posted March 11, 2021 I built this back in maybe the mid 70's, built mine control line, lasted half a lap..... Fox 19 up front 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 11, 2021 Author Share Posted March 11, 2021 Too responsive in pitch? Looked lovely...what a shame. Half a lap? I bet it lasted over twice as long as mine! 1 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 11, 2021 Share Posted March 11, 2021 12 minutes ago, Martin Harris - Moderator said: Too responsive in pitch? Looked lovely...what a shame. Half a lap? I bet it lasted over twice as long as mine! Too much engine, and high incidence on the wing, combined with small elevator movement, it climbed into a loop, went over the top ending in the poor thing hitting the tarmac vertically. The biggest bit was the engine and a nylon bag full of balsa, previously the wing...... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 11, 2021 Author Share Posted March 11, 2021 One good reason to check the incidences while I’m building it but as it was designed for single channel and there’s a reasonable amount of down thrust I suspect that you’re right that the 19 was the cause - around 27% over the maximum design engine size...and airframe designed to climb at neutral trim on an .09! 1 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 11, 2021 Share Posted March 11, 2021 At 15 with no modellers for guidance, we just tried stuff, we had no idea about c of g..... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 11, 2021 Author Share Posted March 11, 2021 Cracking build for a 15 year old! 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 12, 2021 Author Share Posted March 12, 2021 Today has revealed a few frustrations. When I cut out one of the sheets of ply components - the one with lots of fiddly bits - I realised just in time that I'd picked up a sheet of light ply rather than birch ply and was quite relieved not to have wasted time making wing braces and other important parts twice. Today, I continued the marathon kitting process and decided that some trial fitting would be judicious in order to correct any small errors that might have crept in to the downloaded cutting patterns - the fuselage construction being semi self jigging and built in the hand rather than over a plan. After cutting and sanding down the engine bearers to size (I only had some slightly larger material to hand) to check that the chosen engine would fit, I tried a dry trial assembly - and nothing made sense. I printed out the fuselage side view at 100% (8 A4 sheets), hoping that it was drawn at full size - thankfully it was. The problem was then immediately apparent - the keel was massively under sized! As it wasn't visible on the plan, it hadn't been as obvious as you might think. Cessna 180 Fuselage Plan.pdf My heart sank at the realisation that the pdf file had been correctly printed at 100% and was obviously wrong. Some random checks on other components from different files showed that all those checked corresponded with the printed out/stuck together plans so I had some confidence in rescaling the rogue file. A quick calculation resulted in me printing it at 127% which seemed to get the required result on the keel piece (the longest component) so I stuck the patterns onto a fresh piece of birch ply and retired to the workshop for more sawing and sanding. The undersized components are sitting on the plan Once done, things made far more sense and the engine bearers aligned with the formers perfectly. Mind you, I then realised that there were no slots drawn for the tabs to locate the undercarriage plates between two of the formers - easy enough to work out their position but it does mean that any confidence in the completeness and accuracy of the redrawing process has been called into question and I'll need to proceed with care - the downside of downloading a plan from the internet but all part of the fun... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 12, 2021 Author Share Posted March 12, 2021 9 hours ago, Danny Fenton said: Too much engine, and high incidence on the wing, combined with small elevator movement, it climbed into a loop, went over the top ending in the poor thing hitting the tarmac vertically. The biggest bit was the engine and a nylon bag full of balsa, previously the wing...... Looking at the fuselage plan pdf in my previous post shows a degree or so of negative incidence on the tailplane, several degrees positive on the wing and only a little downthrust - so there's little surprise that, especially with a suspect C of G (I have no recollection of balancing it on my fingertips) and a hard upward chuck, my little .09 powered version stalled and plummeted under full power. I think I'm a little wiser these days but time will tell... 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 12, 2021 Author Share Posted March 12, 2021 Building a self jigging fuselage from downloaded redrawn plans is turning out to be stimulating for the brain - very much an exercise in 3D thinking. I’ve spent several hours fettling and dry fitting parts so that they align correctly but I do seem to be getting somewhere now. Dry trial assembly It doesn’t help when details like the undercarriage plate tongue slots have been omitted! I shall definitely have to proceed with care... Before I can make much more progress, I need to decide how to proceed with the undercarriage which is built into the structure at an early stage. My options are to try bending one from Dural, lay up a carbon fibre/fibreglass version or experiment with recreating the original spring steel one using material from a pound shop steel rule. 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 12, 2021 Author Share Posted March 12, 2021 Well, some more thought about the steel rule (too thin and some doubts about softening/drilling/hardening/tempering anyway), the unknown strength of a home carbon fibre lay-up and the absence of any hard alloy in a suitable thickness got me thinking and I have a plan... I annealed some dodgy B&Q aluminium and cut/bent it to shape and mirrored it with piano wire which I will araldite to the leading edge of the ali. The tangs of the piano wire helper shouldn’t show too much behind the wheels and I’m hoping this will suffice for the demands of a lightweight model - the instructions reckon that the flat spring steel one supplied originally would stand up to a “severe pounding”! 1 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 12, 2021 Share Posted March 12, 2021 "the flat spring steel one supplied originally would stand up to a “severe pounding”! I will vouch for that, one of the few surviving parts of mine! 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 13, 2021 Author Share Posted March 13, 2021 Despite some misgivings with some glaring errors on the cutting patterns, some fettling and adjustments have resulted in the whole front section coming together quite nicely and despite some wrongly drawn oversized holes (which will be filled with offcuts after assembly - the undersized ones and a few overlapping tabs were easy to sort) the whole thing holds together without any glue. The use of CA glue will certainly speed up the process over the specified method of double gluing and waiting for balsa cement to set (that brings back memories - I do miss the aroma and the finger picking afterwards) . Once the undercarriage assembly is completed, I should be OK to start actually building the fuselage - the u/c is sandwiched between two ply plates which means it's built in permanently. The fuselage is constructed from the undercarriage formers (visible in the trial assembly) to the tail first and then the nose section is built onto the rear fuselage. Thankfully, the patterns for the fuselage sides are accurate to the plan so the rigging angles should take care of themselves. Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted March 13, 2021 Share Posted March 13, 2021 'Interesting' build....... good to see! GG Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 13, 2021 Author Share Posted March 13, 2021 A bit of work between gardening duties - the composite aluminium/piano wire undercarriage assembly is now sitting on a radiator being bathed in warmth to assist the setting of the full strength Araldite. I wonder what the collective noun for G clamps is? At least I’ve found a use for the undersized undercarriage plates... I’m considering reinforcing the assembly with a wrap of thin tinplate epoxied around the wire and over the legs...little extra weight or thickness but a lot of support for the wire. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 14, 2021 Author Share Posted March 14, 2021 Another artefact from that Ill-fated first attempt at RC flying has emerged...and no, I don’t intend utilising it in the “rebuild”... Having bought the radio from the model shop second hand, I do recall that I phoned MacGregor's to see if I could get some instructions, which they sent by return. A week or two later I received a tersely worded "reminder" from their accounts department that I owed them 12 1/2 pence for the instructions and postage... 1 Quote Link to comment Share on other sites More sharing options...
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