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Subject: How to fix the design defects of the Spitfire airplane of WW-II.
Shooter    5/26/2005 5:12:16 PM
Given 20-20 hind sight, It is easy to see where R.M. went wrong with the Spitfire! The following list of items is my idea of how they should have done it, IF THEY HAD READ ANY OF THE COMMON TEXTS instead of designing a newer SPAD for the last war! 1. Start with the late Seafire or even better the Martin Baker MB-5! they have contra props and wide track gear. The MB-5 also has a much higher LOS out of the pit forward. This is also one of the Spits larger problems. 2. Change the shape/planform of the wing and eppinage from eliptical to trapiziodal. The eliptical surfaces caused the construction time and cost of the Spitfire to be more than double that of the Mustang and almost as much as the P-38. 3. Reduce the wing cord and thus area by 35-40%! This reduction in surface aria will increase the cruising speed substantialy! This is probably the single biggest defect in the design. The change in aspect ratio will also help fuel ecconomy! 4. To compensate for the increased landing and take off speeds install triple slotted fowler flaps with a long hinge extension. This gives a huge increase in wing area and changes the camber for supirior "DOG FIGHT" ability, should you ever need it! ( because the pilot really screwed up!) At full extension and deflection, they would reduce the landing speed by 11~13MPH? (Slip Stick calcs!) 5. Remove the wing mounted radiators and install a body duct like the P-51 or MB-5! This one change would add ~35MPH to the plane? 6. use the single stage griphon engine and install a "Turbo-charger" like the P-38 and Most American Bombers had. This would increase power and save weight, both significant contributers to performance. 7. Remove the guns from the wings! This would lower the polar moment of rotation and give the plane snappier rates of roll! It also makes room for "wet wings" with much more fuel. A chronic Spit problem. It also fixes the Spit's gunnery problem of designed in dispersion! 8. Install the Gun(s) in the nose! Either fireing threw the prop boss/hub or on either side 180 degrees either side of the prop CL. This fixes the afore mentioned dispersion problem. One bigger gun between the cilinder banks or upto four 20MMs beside the engine or both, depending on what your mission needs were! 9. Make a new gun based on the American 28MM or 1.1" Naval AA ammo! This shell was particuarly destructive, had a very high MV and BC and was all ready in service. A re-engineered copy of the existing gun to reduce weight and increase RoF is a faily simple task. Pay the Americans for it if British spring technology is not up to the task! it also frees up much needed production capasity for other things. 10. Design a new drawn steel "Mine" shell for the above gun! Spend the money to load it with RDX instead of the TNT used for the first 4/5s of the war. 11. Pay North American or Lockheed to design it for you, since the Supermarine staff was to tied up fixing the origional spitfire design to get it done any time soon. Did I miss anything?
 
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AussieEngineer    RE:How to fix the design defects of the Spitfire airplane of WW-II.   5/13/2006 10:11:20 PM
the next milestone is 1111 I suppose, not far off
 
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MustangFlyer    RE:Spitfire VII performance + Merlins   5/15/2006 3:33:13 AM
I has to do a bit of digging for this. Mk VII: High altitude fighter (strato spit). Merlin 61, 64 & 71 engines. Checking the serial numbers I could only find a few Merlin 71 engines used (not many VIIs made anyway). Merlins: 61 - Early Spits VII, VIII & IX. First production 60 series enging. 63 - Some Spit VIIIs. Uprated and strengthened. 2 piece head, strengthened supercharger quill shaft. Allowed higher boost level. 64 - Most Spit VIIs. A 63 with Marshall cabin blower for pressurisation. 66 - Spit Mk VIIILF, Most IXs(LF). Low altitude version. Changed supercharged and propellor ratios. Rated to 25 lbs boost with 150 octane. 70 - VIIIHF, a 66 optimised for high altitude. Changed supercharged and propellor ratios. 71 - A 70 with cabin blower. 72/73 - Same as 70/71 but reversed cooling system for Mosquitos. Packard: V-1650-3. Same as M63. V-1650-7. Same as M66.
 
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MustangFlyer    Spitfire & Rear Tank + air war   5/16/2006 5:41:37 AM
The Spit might not have been quite so sensitive to rear weight as most people think. This has tended to become a bit of a myth, like the engine cutting out under negative G, partially fixed from 41 onwards (all models), totally fixed 42 onwards (VII,VIII, IX, late Vs, etc). Quote: Shea-Simmonds (test pilots), 1/6/45 (June 45). Rear Fuel Mk IX, "with 25 gallons of fuel in the rear tank it is just acceptable for combat". Boscombe Down: January 1945. ML 186 (Mk IX). Handling test with 75 gal(UK) rear tank. "The acceptable aftmost CoG position for combat manoeuvres was 9.9in aft of datum (34 gals used from rear tank)." Remember the limiting factor in range was the remaining fuel after combat to return to base (ie no drop tanks left and some of the rear tank burned off). The Spit was very economical at cruise (as was the Mustang), typically 6-7 air miles per (UK) gallon was the norm. Even 20 or 30 gals left made a huge difference to return range. This was the limiting factor on the Jug. At most economical crusing it could make a reasonable 60-70 (US) gallons per hour, but any more power used (such as for combat, escape or climbing) and you quickly hit 200-300 (yes really) gallons per hour. I've crunched the numbers so many times and I can't get the early Jugs (P47C, pre P47D-25, all with 300 US gals of fuel) much past 400 miles, under any realistic scenario. The need for boom and zoom tactics made this worse. The Jug used around 200 gals per hour climbing at military power. So a 400 mile mission meant, at best, one pass at the enemy then home at most economical speed. It just didn't have the fuel to climb back up again for another attack, remembering that the Jug had to extend far away to a safe distance, before slowly (grindingly, an unkind person woudl say) climbing back up to combat height. If the '43 generation P-38s had been more reliable and better at altitude then they would have made a much better impact (don't get me wrong, if I'd been on a long range mission in the Pacific in 44 I'd have wanted to be in a late model P-38 as well). As for the impact of small numbers of (theoreticaly possible long range Spits), look to the P-51B/C. Even when they only had (sometimes) 20-50 for a mission they made a tremendous difference. The key was the Luftwaffe's tactics. They depended on their twin engined planes (Me-110s and Ju-88s) with rockets to break up the formations, then the single engined planes took out the stragglers. As soon as there was a decent escort fighter available this system broke down as the twins were slaughtered. The Luftwaffe simply didn't have a high performance twin (e.g. Mosquito/P-38) or enough single engined planes. At high altitude only the Me-109 was acceptable, but with extra guns fitted (it took, on average, 20 x 20mm cannon hits to take out a bomber) its performance was crippled (its great weakness, light guns, great against fighters, poor against bombers). Heavily gunned FW-190s had the same problem, poor performance normally at altitude, worse with extra guns and armour. Even a few escort fighters could decimate the twins and over-gunned singles and the Luftwaffe simply didn't have enough pure fighter singles to protect them. So they could fight against the escorts, or take out the bombers, not both. Lucky for us that Galland wasn't listened to and they didn't build enough single engined fighters in 42/43, as well as a decent twin (e.g. Ta-154). If they had a P-38 or Mossie it would have been much tougher. A fast twin could have hit the bombers then escaped with acceptable losses, again leaving the stragglers to the singles, or even the twins on a second pass .. ouch. If they had built the number of fighters that Galland wanted in 43 .. ouch again. You could argue that the air war was won by the side that made the least mistakes.
 
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MustangFlyer    RE:Spitfire & Rear Tank + air war   5/16/2006 8:06:55 AM
Whoops mistake. The best figure I could find for the Jug was 66 gallons per hour, not 60. Sorry. Mutter, mutter, blasted keyboards, grumble, humm ......
 
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Cromwell    RE:Spitfire & Rear Tank + air war   5/17/2006 4:42:52 AM
Hi MF Many thanks for the information. Could I ask where you found the figures? I'm certainly not doubting your calculations: just interested in finding other sources of info. C
 
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larryjcr    RE:Spitfire & Rear Tank + air war   5/17/2006 5:50:00 AM
I had always assumed that the negative-g engine cut out had been fixed in the MkV, just due to the fact that complaints about it stopped. Even then, '109 pilots continued to disengage by diving away, so they still, obviously, had superior acceleration in initial dive. This habit gave the early P47 pilots a number of easy kills well into early '44 when they should have known better. You're quotes for the acceptable cg shift are for '45, so assume that they are with very late model Spitfires. Perhaps the heavier a/c had something to do with it?? Note that the RAF took most (or all??) the fuselage tanks out of their Mustangs becasue they didn't like the effect of weight back there, and the Mustang was both heavier than the Spit, and, due to layout, had the fuselage tank closer to c/l so weight there would have less effect on cg. Won't try to argue your math, just point out reality. The '47s escorted well into wester Germany, and getting home after combat was always the queston for them. The 'bolt could handle so much external load that after they got the wing pylons, range with the drop tanks was never a problem. Your observations on the importance -- and limitations of the German twin-engine a/c are certainly true. Similar problems with the later '109s with the 30mm cannon, or underwing rockets. Fighter-vs-ftr capabilities were deliberately sacrificed for anti-bomber weaponry. The '109s and '190 weren't heavy enough to handle both mission well in one package. Also why the P38 could reduce bomber losses effectively in spite of the small numbers available. In spite of twin engines, and size, it was still a capable ftr-vs-ftr type. Certainly better than anything else the Luftwaffe was going to meet over central Germany in '43.
 
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MustangFlyer    Cromwell RE:Spitfire & Rear Tank + air war   5/29/2006 5:12:04 AM
Sorry about the delay in replying. I'ts been a bit of work pulling all together. For hard information of fuel usage I used the hard sources from the SpitfirePerformance website. They have the actual test results and copies of the aircarft performance cards. I also used them for the P-47 model. The numbers they have are for the P-47N, which I adjusted (favourably) to estimate the P-47C early P-47D. For example, for climb performance I used the P-47N figures without a drop tank, as it was heavier (due to the wet wing). It should be roughly the same as a P-47C with drop tanks. For serial numbers and specifications of Spitfire I used the bible: Spitfire, The History by Morgan & Shacklady. This book takes a LOT of reading as many details (e.g. rear tank COG tests are buried away in the text amongst the hundreds of pages). But worth the effort. Thats how I worked out the Mk VII's with Merlin 71s, I went through the serial numbers and checked the engine types (tedious). I'm just buying a couple of books on the Merlin, so I'll have some real details in a few weeks. The power they got out of it was amazing for the size (and the time). 27 litres, vs 36 for the Griffen & Sabre or 56 for the R2800, incredible. If you get anything let us know. Ebay is a good source for many books as well as the second hand dealers. If anyone can get more on the P-47 let me know and I'll be able to update my model with any new figures. Cheers. Ap[arently (I'll confirm when I get the books) the 100 series (final) were rated at 30lbs boost!!!
 
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Cromwell    RE:Cromwell Spitfire & Rear Tank + air war   5/29/2006 8:34:54 AM
Hello MF Many thanks for the info: I've been out of action too, due to a leg operation. C
 
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MustangFlyer    RE:Cromwell Spitfire & Rear Tank + air war   5/29/2006 8:42:37 AM
Ouch, ok now?
 
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MustangFlyer    The wing   5/29/2006 8:55:21 AM
I should add that the 'bible' is interesting about the development of the elliptical wing. Earlier designs didn't have it (really). It came about for similar reasons why Republic (P-47) and Hawker (Tempest) adopted it as well. Depth for guns. (Note, I'm not so familiar with the P-47 design but I expect very similar reasons) The Tempest wing came about from the same design logic, very thin (for performance) + low wing loading = lack of space. Using the elliptical wing gave the space without sacrifising the perfornace, typical design compromise. Would Mitchell's team stuck with that if they knew they would have to make 22,000 of them? Who knows. It worked, hard to argue with success.
 
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