Tim Hooper Posted March 30, 2012 Author Share Posted March 30, 2012 OK, the tops of the nacelles are planked and rough-sanded, which is good. On the other hand, I seem to have a bit of a wall with the canopy. I've tried several pop, cider and assorted drinks bottles - all to no avail unfortunately. So I need to re-think this a bit. Bear in mind that I want other people to be able to replicate the ST as it's presented in the photos, so I'm not going to start faffing about with experiments in home-moulding; was there ever a better way to dissuade potential builders? Hmmmmm.............. tim Quote Link to comment Share on other sites More sharing options...
Tim C Posted March 30, 2012 Share Posted March 30, 2012 Tim, Others have used to http://www.vortex-vacforms.co.uk, if you can produce the former, he can vacform canopies to order for future buildersr, not expensive either. I have a feeling Nigel Hawes used him on his RCM&E design plans Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted March 30, 2012 Author Share Posted March 30, 2012 Thanks for the link Tim! For the present I'm going to take the easy way out, and make a 'solid' canopy from foam, with either glasscloth or brown paper on top of that..... tim Quote Link to comment Share on other sites More sharing options...
Mastercrashman Posted March 30, 2012 Share Posted March 30, 2012 Hi Tim Further back in the thread you were discussing scaling with Adrian Day. You advised multiplying all the dimensions with the same factor. As the area of the wing increases out of proportion to a linear scale up (and vice versa with a scale down) how do you cope in your scale designs with the different wing loadings . You would have a warbird for instance turning into a floater with a scale up. Do you plan for heavier gear in this case. Or have i got the concepts wrong. MC Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted March 30, 2012 Author Share Posted March 30, 2012 Hi MC! What you say is quite right! Doubling a model's size increases it's wing area by a factor of four. Mind you, don't forget that you're also doubling the model's third dimension too, so you're actually cubing it's volume (a factor of eight). Imagine doubling the size of a 1" cube - you end up with 2" cube with a volume of 8 cubic inches, yes? So, the extra structure in the enlarged model does indeed seem to cancel out an ever-decreasing wing loading after all! Most of my models, regardless of size, seem to end up having a wing loading between 16 and 20 oz per square foot. tim Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted March 30, 2012 Author Share Posted March 30, 2012 Eeny, meeny, miney, etc....... You'd have thought that at least one of this lot would double up as a canopy, wouldn't you? Sadly, no. OK, so the cider gets it first..... Plan B involves sticking great big lumps of blue foam to the fuselage, with the intention of hacking them into some sort of appropriate shape later! Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 30, 2012 Share Posted March 30, 2012 Hi Tim, what are you joining the blue foam with to avoid ridges when you sand? I have a smallish vacform table if you want to send me the final plug? The twin looks great, started the Elf yet Cheers Danny Quote Link to comment Share on other sites More sharing options...
Mastercrashman Posted March 30, 2012 Share Posted March 30, 2012 "Mind you, don't forget that you're also doubling the model's third dimension too, so you're actually cubing it's volume (a factor of eight). Imagine doubling the size of a 1" cube - you end up with 2" cube with a volume of 8 cubic inches, yes?" Thats interesting Tim, I never thought about that. I've wanted to downscale a couple of larger models (and try a quck foam build) for a while but didn't have the confidence to try. I'll do a simple scale down. Thanks again for the info. MC Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted March 30, 2012 Author Share Posted March 30, 2012 Danny, I've pretty much switched from PVA to aliphatic these days (despite the fact that I can get gallons of free PVA from work.....sigh....), as it sands easily. Anyway, I'll probably glass/WBPU the foam after it's sanded to shape. Would that be suitable as a plug? MC, it all starts to make sense now, doesn't it? tim Edited By Tim Hooper on 30/03/2012 20:04:54 Quote Link to comment Share on other sites More sharing options...
Mastercrashman Posted March 30, 2012 Share Posted March 30, 2012 "MC, it all starts to make sense now, doesn't it" Tim, it would be if I could do it from scratch. Do you keep some treasured tome at your fingertips when you do your scratch designs or do you just know it now? Is there any book that you have found to be aerodynamically understandable for aeroplane modellers? I would agree that if an aeroplane looks right it will probably fly right and I have made simple gliders using that principle but it wouild be nice to have a reference to be able to take it that bit further. Sorry to hijack your build thread with all these questions but now I've got your attention I hope you don't mind if I milk the occasion a little bit further. MC Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted March 31, 2012 Author Share Posted March 31, 2012 MC, I don't have a magical guide, I'm afraid. Having said that, I want 150"° of wing area for every lb of AUW. The tailplane is likely to be at least 12% of the wing area. The CG usually gets set at 28% of the MAC. The wing is set at 1-2° of incidence. Zero incidence on the tailplane. No downthrust on a low-winger, 2° on a high-winger. 12% ClarkeY aerofoil on a slow scale or biplane. Semi-symmetrical aerofoil on a lively sports model. Nothing to too complex...... tim Quote Link to comment Share on other sites More sharing options...
Mastercrashman Posted April 1, 2012 Share Posted April 1, 2012 So that's your secret . Thanks for that Tim. Regards MC Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted April 4, 2012 Author Share Posted April 4, 2012 Right then, after a mad weekend of celebrations, I actually got back into the workshop for an hour this evening! The foam canopy has been hacked to shape and then glass-clothed, using water-based polyurethane vernish as a resin. Hopefully this will give me the option of moulding an acetate canopy later. The wing was turned upside-down, the undercart temporarily fitted and the lower nacelle formers glued in place, prior to planking. Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted April 10, 2012 Author Share Posted April 10, 2012 There's an old story about a famous sculptor being interviewed by a reporter; "So how do you go about sculpting an elephant?" The sculptor replied; "Easy - start with a large block of marble, and simply remove anything that doesn't resemble an elephant........." The same applies to cowls - except that you have to make your block to begin with before you start to find the cowl within..... About time we had a look at the overall progress, I think! Edited By Tim Hooper on 10/04/2012 21:26:40 Quote Link to comment Share on other sites More sharing options...
Lindsay Todd Posted April 11, 2012 Share Posted April 11, 2012 Very pretty little thing that Tim, probably go like a rat up a drain pipe I would think. Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted April 11, 2012 Author Share Posted April 11, 2012 Posted by Lindsay Todd on 11/04/2012 00:33:10: Very pretty little thing that Tim, probably go like a rat up a drain pipe I would think. .....or wallow around the runway like a floundering fish! That's the appeal of this scratchbuilding lark - the big question of whether the thing will actually fly or not! tim Quote Link to comment Share on other sites More sharing options...
Stefan Hafner Posted April 11, 2012 Share Posted April 11, 2012 Ah, but Tim, everything will fly with a certain amount of encouragement, its more of a question of how long it'll fly Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted April 11, 2012 Share Posted April 11, 2012 its too pretty not to fly well, but i am with Linds its gonna go like stink! please video the maiden, and you may need the bike clips for the landing me thinks. possibly start your downwind turn in staffs Seriously looks great Tim Cheers Danny ps hows the Elf? Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted April 12, 2012 Share Posted April 12, 2012 Love it Tim, looks like a right ol' rocket ship Quote Link to comment Share on other sites More sharing options...
Rex Keene Posted April 13, 2012 Share Posted April 13, 2012 Tthat's a lovely looking build. Could you give a bit more details of the electrics? Im planning an electric twin of a not dissimilar size, but I haven't decided the power train yet. thanks. Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted April 14, 2012 Author Share Posted April 14, 2012 Thanks Guys! The airframe is now liberally covered in filler, pending rubbing down prior to covering. I suspect the nacelles may take a bit more than normal attention..... Rex, I'm fitting a pair of Turnigy D2826/10 1400Kv outrunners, 7x4 props, 25A ESC's running off a 3S pack. This is an untried set-up for me, so I can't yet comment on its performance. tim Quote Link to comment Share on other sites More sharing options...
Rex Keene Posted April 14, 2012 Share Posted April 14, 2012 Thanks for that. So it's one receiver, which feeds two ESC's, which each in turn control their own motor? and all that, plus the servo's, is driven from one battery pack? Can any/all receivers drive two ESC's, or does it take a specific model? ( sorry for the hijack!) Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted April 15, 2012 Share Posted April 15, 2012 Hi Rex , Any receiver can drive two Esc , just think of them like a servo you just need a Y lead . Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted April 15, 2012 Share Posted April 15, 2012 Tim , Very nice aeroplane that . My next model was going to be a twin as i have three identical motors waiting for a home , i think you have come up with a real belter Quote Link to comment Share on other sites More sharing options...
Tim Hooper Posted April 15, 2012 Author Share Posted April 15, 2012 Rex, Like Stephen says, just connect the two ESC's to the receiver through a standard Y-lead. No probs! Stephen, what size of twin are you looking at? Mind you, if you have three identical motors, then..... Quote Link to comment Share on other sites More sharing options...
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