Colin Leighfield Posted May 23, 2014 Share Posted May 23, 2014 This has been on my mind for a long time, but if it had depended on my pencil and paper it would have remained a long way off. The opportunity to move it forward has been provided by Dylan Reynolds in his new venture Lasercraft Services. Working from a minimal three-view drawing and not too much else, he has been able by using CAD to produce a full-blown structural design and is now in the process of laser cutting the parts for me. In a separate thread, Robert Parker has launched his Short Stirling project and that is going to generate a lot of interest, it certainly interests me. What is not generally known is that the Stirling was actually the back-up to the Supermarine 317 designed by Reginald Mitchell, his last. The 317 was the RAF's favoured choice, but circumstances worked against it and when the two partly constructed prototypes were destroyed in a bombing raid on the Supermarine works at Itchen, Southampton, along with most of the documentation, that was the end of it and fortunately, the Stirling was there to fill the gap left by the 317. Although we recognise the Lancaster and Halifax as being our two leading heavy bombers in WW2, they both originated as twin engined medium heavy designs against specification P13/36. Both were adapted for four engines, the Halifax before its' first flight and the Lancaster later by conversion from the Manchester. The true heavy bomber specification was B12/36 and there were two designs chosen to be built against that from a number of contenders, the Stirling and the 317. There's a lot more to say about the detail of the 317 later, it was much more advanced than the Stirling and was designed for easy mass production, whereas the Stirling was labour intensive and slow to build. This first attempt to model it is at a manageable 1/16 scale, which gives a wing-span of 68.5" and a length of 52", with a wing area of 676.5 sq.ins. This has been chosen to match up to the 72" Nihuis Lancaster, which is 1/16 of the 102' wing-span original and I intend to use the same power-train. The sharply tapered wing will have 3 degrees of washout from root to tip. The intention if this is successful is to scale up to 1/12 as the next step, which will give 97" span and 73.5" long. I'm pre-occupied right now with getting two others finished off for Greenacres, the Seafang and Depron Barnstormer, also I'm starting the Chipmunk build in October, but I'm getting a bit more time to do things now, so I'm optimistic. Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted May 23, 2014 Share Posted May 23, 2014 i have been following dylans work on this one and now i can follow your build thread. yay Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 23, 2014 Author Share Posted May 23, 2014 Thanks Tony. It's Dylan's work on Tony's Shackleton and his own Albermarle that's provided a lot of the basic structural thinking for the 317. He's doing a great job and deserves all the support he can get. Quote Link to comment Share on other sites More sharing options...
Martian Posted May 23, 2014 Share Posted May 23, 2014 another build to follow Quote Link to comment Share on other sites More sharing options...
Dylan Reynolds LaserCraft Services Posted May 23, 2014 Share Posted May 23, 2014 and they say building is dead Quote Link to comment Share on other sites More sharing options...
Lindsay Todd Posted May 23, 2014 Share Posted May 23, 2014 Excellent project, great to see so many multi engine classics being built, will watch with great interest as this project progresses. Linds Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 23, 2014 Author Share Posted May 23, 2014 Thank you Lindsay, it won't hold a candle to your efforts but I hope it's interesting and unusual. I note that I said 1/16 scale, it is of course 1/17, as is the Nihuis 72" Lancaster. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted May 23, 2014 Share Posted May 23, 2014 Very good Colin, I like different the wing's a bit nice John Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 23, 2014 Author Share Posted May 23, 2014 Thanks John. It was a very clever design, losing Mitchell was a disaster really, if he'd survived I think this would have as well. Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted May 23, 2014 Share Posted May 23, 2014 Oooh those wingtips look "nice" and pointy Colin, that looks like it will be interesting to fly! Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 23, 2014 Author Share Posted May 23, 2014 Hi Chris. I had your DH88 Comet in mind when I first looked at this. It's got three degrees of progressive washout designed in from root to tip. I don't think it will be a problem. Although not fully elliptical, it's got some similarity to the Spitfire and Mitchell actually used the same NACA2200 wing section. Real Spitfires don't tip stall. There's only one way to find out and this is it. I'm looking forward to it. I've thought a lot about this tapered wing and tip stall issue and this could be the ultimate test! I'm not worried. Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted May 24, 2014 Share Posted May 24, 2014 This will be a good one Colin - I shall watch avidly! Terry Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 24, 2014 Author Share Posted May 24, 2014 Thanks Terry, I'll do my best because I'd like to move up to 1/12 for the next one and really find out what this would have looked like. I'm the world's worst for getting carried away by ideas and having projects drag on. I'm trying to change that by giving myself targets. Fingers crossed! Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted May 24, 2014 Share Posted May 24, 2014 Posted by Colin Leighfield on 24/05/2014 09:14:40: I'm the world's worst for getting carried away by ideas and having projects drag on. I'm trying to change that by giving myself targets. Fingers crossed! No Colin you're wrong there! You are at least no 2! I'm on the 'worst in the world spot' and hopelessly missing targets! Terry Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 24, 2014 Author Share Posted May 24, 2014 Oh dear! It seems we have the makings of a "world's worst" club. Quote Link to comment Share on other sites More sharing options...
Terry Walters Posted May 24, 2014 Share Posted May 24, 2014 LOL! Terry Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted May 24, 2014 Share Posted May 24, 2014 Put my name down John Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted May 24, 2014 Share Posted May 24, 2014 i wont join in then Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted May 24, 2014 Share Posted May 24, 2014 Of course the Supermarine 317 would have suffered from exactly the same problem as the Stirling in that it could not accommodate anything bigger than a 2000lb bomb but to be fair this was the maximum sized called for in the specification. It appears that the fact the Lancaster could carry larger was simply a by product of the way Roy Chadwick designed the bomb bay structure. Quote Link to comment Share on other sites More sharing options...
David Pearce 4 Posted May 24, 2014 Share Posted May 24, 2014 I recently read “Schneider Trophy to Spitfire” by John Shelton. Covering the design career of R J Mitchell, it’s a good read and it does have a very short passage on the Type 317. Interestingly, the design was lighter and smaller than the Stirling, Halifax and Lancaster yet was significantly faster, had a longer range and carried a larger bomb load. Off course this was unproven but the author does make the point that “Supermarine estimates were achieved when its designs flew . . .” Food for thought. A fascinating project Colin, and one I’d love to see fly. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted May 24, 2014 Author Share Posted May 24, 2014 Simon is exactly right, it seems odd now that the specification for the strategic heavy bomber aimed at a large number of Armour Piercing up to 2,000 lb. bombs while the medium heavy specification left scope for an uninterrupted bomb bay with the potential for larger bombs which later went through 4,000, 8,000 lb. Blockbusters and even the 5 and 10 ton Tallboy and Grand Slam in the Lancaster. Even so, it does not mean that the 317 would not have been a very effective heavy bomber, the USAAF B17s and B24s carried out their strategic bombing campaigns without using very heavy individual bombs and were effective enough. If Mitchell had survived, I've no doubt that he would always have been in front of the game as preferences on ordnance developed. Putting the bombs into the wings wasn't unique by any means either, but in the 317 Mitchell did it deliberately for two reasons:- Using the weight of the bombs to offset the bending loads on the wings enabled a reduced structure weight and it also reduced the fuselage cross section by 42%, one of the key reasons for the anticipated high speed. In the front on view, that exaggerates the actual thickness of the wing because of the small fuselage section, made even more apparent because of the very broad root chord of the wing. Parts of the leading edges also were used as fuel tanks with a further offset on bending loads and reduced the structure weight even further. Mitchell also had original thoughts on the design of the gun turrets, each could carry two or four guns, but they were set low, so that the gunner had a clear view over the top of them. If the 317 had continued, it is likely of course that a mid-upper turret would have been required later and that would have reduced the top speed, but it would almost certainly have been considerably quicker than its' contemporaries. It's all speculation now, but there's no harm in that and I'm quite fired up by this. David, thanks for your interest, hopefully we will see this fly before too long. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted June 21, 2014 Author Share Posted June 21, 2014 I had the great pleasure of meeting Dylan Reynolds and Tony Bennett at Greenacres today. Tony had brought the amazing Shackleton MR2 he is building from the CD design and laser cutting work done by Dylan. (Lasercraft Services). Also, Dylan had brought the box of parts he has made for my Supermarine 317 after doing the CD design work based on very limited drawings from me. Very clever. I can't start this for a few more weeks, until I have finished the delayed completion of the Seafang and the Depron Barnstormer (frustration). Still, look at this, I can't wait. Quote Link to comment Share on other sites More sharing options...
Pup Cam Posted June 21, 2014 Share Posted June 21, 2014 Just found this thread - this is going to be very interesting! By the way, I'll probably be somewhere on that missed target list. Triplane ready for the commemoration of the start of WW1 - Doh! Alan Edited By Pup Cam on 21/06/2014 22:04:10 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted June 22, 2014 Author Share Posted June 22, 2014 New targets Alan, get it ready for the commemoration of the end of the first year of World War 1! That's when they realised that it wasn't all over by Christmas! Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted June 23, 2014 Author Share Posted June 23, 2014 We are on holiday for a couple of weeks after today so I won't be able to get on with this for a while anyway, but I thought I'd have another look this morning to get my head around the way it goes together. These parts fit together quickly. There's a lot of bits, but once I've identified where they all go, it will assemble very quickly. Dylan has cut all the ribs with tabs set to give the required 3 degrees of wash-out, the panels will be built inverted on the board. Will require some working out for the wing tubes, but that shouldn't be too difficult. Quote Link to comment Share on other sites More sharing options...
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