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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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MustangFlyer    RE:High-speed attacks? Carburettor Myth.   6/18/2006 6:30:32 PM
I'll get onto the outher points later but I've just finshed reading Alex Havery-Bailey's book "The Merlin in Perspective - The Combat years" Rolls Royce looked at fuel injection (or which they had considerable experience) but chose the carburettor (which fed into the supercharger inlet) because of the better charge cooling (worth 25C reduction in charge temperatures). On advice from the RAF negative G performance had not been forseen as an issue. It was quickly fixed (6 planes on trial at the end of the BOB), 1st by Tilly Shillings restrictor, quickly retrofitted to all Merlins), which reduced the problem to only contineous negative G, second by the SU negative G carb modification (created by Shilling's dept - which she was the head of). All subsequent SU or Bendix carbs used in Spits were negative (and zero) G complient. When RR moved to fuel injection (for the 100 series Merlin) it was a single point, injecting directly into the supercharge inlet, for the same charge cooling reasons. As well as more power, lowered charge cooling helped fuel economy, by avoiding having to inject a richer mixture to cool the cylinders. So it was a concious engineering solution to get more power out of a smaller engine. This paid off, in the BOB the Me 109 with the DB601 engine had almost identical performance to the larger and heavier Spit with a smaller engine. Note also that 100 octane fuel had no effect on high level performance (due to supercharger boost dropping off), where most of the BOB fighting happened. Like the later 150 octane it helped low and medium level performance.
 
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larryjcr    RE:High-speed attacks? Carburettor Myth.   6/19/2006 1:14:47 AM
AS you say, the tactical problems were unforseen, but they were still problems. The '109s could easily disengage by pushing over. Add the fact that optimum acceleration means unloading the wings, which added to the advantage.
 
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larryjcr    RE:High-speed attacks?   6/19/2006 1:19:50 AM
To AussieEngineer. I was under the impression that the prototype of the '109 had an American made CS prop installed on the British made Kestrel engine after some disappointment in intitial performance results, and that made a radical improvement on the a/c. When the Spits and Hurris finally got CS props during the BoB, it certainly improved their climb rate.
 
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MustangFlyer    RE:High-speed attacks? Carburettor Myth.   6/19/2006 4:58:01 AM
Dont forget that the better pilots learned how to minimise the problem by a quick half roll and dive. Great quote by Wing Cmdr Beaumont (of Typhoon, Tempest, Canberra and E.E. Lightning fame) and who flew Hurricanse in the BOB in no 87 squadron: "Another thing we did was to devise a manoeuvre which was aimed at getting us out of difficulty if we ever got into one. This may sound very extraordinary probably to practising pilots today, but it consisted of putting everything into the left-hand side of the pit. If you saw a 109 on your tail, and it hadn't shot you down at that point, you put on full throttle, fine pitch, full left rudder, full left stick and full forward stick. This resulted in a horiible manoeuvre, which was in fact a negative G spiral dive. But you would come out of the cottom of it with no Me 109 on your tail and your aeroplane still intact". Amazing.
 
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MustangFlyer    RE:High-speed attacks? Carburettor Myth.   6/19/2006 5:00:58 AM
Also, must have been a real shock for Me 109 drivers when the 1st negative G Hurris and Spits hit the skies in early 41. "I'll just dive away from this Schpitfire as I did on the BOB. What the ........", switch to sound of parachute opening.
 
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MustangFlyer    The Elliptical Wing - The Genesis   6/19/2006 5:13:57 AM
Mr Davis (part of the Supermarine drawing office at the time): "As further proof I have photocopies of some of the early calculations made in May 1934 on the F7/30, Type 224 development by R S Dickson, a young engineeer who made the project drwaings for Allan Clifton and Ernie Mansbridge. At the time the ammended design has a Goshawk steam cooled engine and a straight tapered wing. Dickson told me - 'The wing at this stage had no kink in it , as the F7/30, and was straight tapered, but later the final, elliptical shape was shown in my drawing. This was condemned as not producable in quantity, but the eight gun installation appeared about this time (F5/34) from the Air Ministry and it was not found possible to get the outer guns in a straight taper but easier in an ellipse. So the elliptical wing prevailed.' " (Morgan and Shcklady, Spitfire The History, Pages 19 & 20) QED I think.
 
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AussieEngineer    RE:High-speed attacks?   6/19/2006 5:17:45 AM
To be honest I don't know about the specifics of the prop used on the 109 prototype, I did know it used a RR Kestrel though. However, the production 109s up to some post BoB Emile sub variant had variable pitch props not CSPs. Even after that I don't think the automatic mode could be switched to a CSP setting like on the Fw-190.
 
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MustangFlyer    Spit Wing   6/19/2006 5:53:07 AM
The Spit was at the leading edge of design at the time, as I said before the F-22 of the time. Messerschmitt, Hawker and Supermarine all faced the same problem. How to get the best performance out of (maybe) 1,000hp. Hawker took the most traditional route and the Hurrcane should be seen as a transitional plane. Non-monocoque contruction (tubular), fabrix covered rear, thick wing. It resulted in an easy to build plane, with good (for the time) performance. But it was critically compromised, with little development potential. Due to the Air Ministry specifications it was a good gun platform, with 8 closely grouped .303 guns, later 4 x 20mm and some 2 x 40mm. Messerschmitt took a more radical approach (full monocoque) but dealt with the problem of performance by size. The Me-109 was as small and light as was possible (smaller and lighter than the Hurricane or Spitfire). In many ways it was more traditional, because he went for a high wing loading for speed, but a small size for weight and climb (empty: 4,180 lbs vs 4,341 for the Spit Mk 1. Max Take off: 5,875lbs vs 6,200lbs for Spit Mk 1). The big innovation was the slats. Much critisised by some (I think wrongly since they are used so much now) it meant that good slow speed performance could be obtained (e.g. for landing) even with the high wing loading. The small size came with problem. Fuel capacity was always going to be limited and arnmament was an issue. The became very evident in 43/44 against US bombers, with external 'bathtub' mountings being necessary for larger cannons in the wing, with the attendent effect on performance. The Me-109 could never had had 4 x 20mm internally mounted in the wings as did the Hurricane, Spitfire, FW-190, etc. Supermarine took it too the edge. A large wing (for low wing loading and hence climb and manoeuverability) capable of heavy arnament (and later more fuel). This should have meant much poorer performance and much more weight. Supermarine 'squared the circle' by making it so thin. More than the elliptical shape it was the thinness that delivered the perfomance and enabled the Spit to absorb a doubling of power over the 4 years (plus the best mach performance of anything). It was right at the limit of material science and production capability at the time and a very bold leap. Even slightly thinner and it would not have been strong enough and there was contant threat of not being able to actually build it at the beginning (so much so that the Air Ministry seriously though of abandoning it in 38). So from an aerodynamic point of view it was very much the leader in innovative design at the time. Supermarine also overcame the problem of strength by (again) a very innovative box spar design for the single spar, which was very strong. So strong that the Spit nearly doubled in weight and carried bombs, external tanks, etc with little problem later in the war, as well as having very high G abilities. There was a cost to this (as always), the Spit suffered wing twist behind the spar at high speeds, reducing aileron effectiveness. Note: I think I've finally worked out why the clipped wing Spit's roll rate improved so much, which I'll post later after some more checking.
 
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MustangFlyer    Anyone else (get involved).   6/19/2006 9:00:55 AM
There have been 15,906 views of this thread, anyone got any other data or comments? Apart from Larry (who I may disagree with on some things but respect highly), AE (always makes some interesting points) and myself , not much comment. Even if you are just interested and agree/disagree about some points, make yourself known, get involved, hey we don't bite. Some other forums I've seen there is a great sense of community, with people, sometimes, simply saying " that a great point" or "thanks for the information" even "I think thats thats wrong". Heck, just add a bad joke. Keeping the SP community going involves everyone being involved.
 
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MustangFlyer    RE:Spit myths -OB Huhmmm   6/19/2006 10:20:05 AM
Well OB, not that often we disagree but about the genesis of the Spit wing???
 
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