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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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larryjcr    RE:cruise speeds   7/7/2005 1:48:09 PM
Wing loadings figured as empty wt.(lbs)/wing area sq.ft. Spit LFIXE: 25.11 Spit XIVE: 27.27 Spit 21: 28.28, P51D: 30.58
 
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larryjcr    RE:cruise speeds   7/7/2005 1:51:42 PM
According to my ref. "the type (Spit 21) was too late to see war service" Although the first unit, No.91 Sq. at West Malling had re-equiped just before VE day.
 
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AussieEngineer    RE:cruise speeds   7/7/2005 7:54:54 PM
Yeah, it got in by skin of it's teeth.
 
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AussieEngineer    wing loading   7/7/2005 10:06:25 PM
Also the Mk I empty wing loading of 19.88 lbs/ft^2. 25.11 would have to be a clipped wing MkIX right?
 
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larryjcr    RE:wing loading   7/7/2005 11:25:31 PM
LFIXE. Clipped wings. Would have been a little lower for the HF. By the way, wing area for the Mk21, 244 sq ft, was very slightly larger than wing area for the earlier, elliptical wing Spits, 231 for the LFs (clipped) and 242 for the HF versions.
 
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larryjcr    RE:wing loading   7/7/2005 11:28:53 PM
Anybody got an answer to this question? By the Mk 21 nearly everything about the original Spit except the general layout and the landing gear had been redone. Why didn't they do anything about the weak, narrow track landing gear??. I know, in the MkI it was easier to stow in the thin wing, but when they redesigned the wing anyway ...
 
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AussieEngineer    RE:wing loading   7/8/2005 2:10:07 AM
I don't know, it would have made sense to try and do that from the beginning. It's one of "fixes" I recommended.
 
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Shooter    RE:wing loading   7/9/2005 6:02:49 PM
More answers, again; [That conflicts with what I have, unless what you reading is IAS, which would fit perfectly. That is for the Mk.XIV not the Mk.21.] No it does not. That is the "combat cruise" speed not the Eccono cruise speed. Since fule consumption goes up as the square of the differance in speed, the faster speed used much more gas and thus the plane could not reach its' plackard range. [Why would it not reach it's stated range,] See above! [ if that were the case wouldn't they have revised the range down? All the range and endurance data I have used are for aircraft that have either C or E armament and standard fuel loads. Not ones with additional tanks and removed weapons. ] The range figures are for standard planes with full fule and ammo flown at minimum throttle openings that the engine will tollerate without loading up. [The wing loading of late model spitfires was very close to that for a mustang. Both had similar wing areas and weights. ] Not true if you use loaded weights instead of empty mass. The Mk-XIV had an MTO weight of 10,280 pounds and a wing aria of 244Ft2 or a loading of 42.13Lbs/Ft2. IIRC! The Mustang with an MTO of 11,600 pounds and 240Ft2, Again IIRC, = 48.33Lbs/Ft2. Not a small differance. [Engine settings were just part of shifting from a cruise setting to a combat one.] See my other post as to what exactly that entails!
 
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AussieEngineer    RE:wing loading   7/9/2005 8:27:26 PM
Shooter, I can read, the speeds I am talking about are clearly most economical cruise speeds. http://www.lanpartyworld.com/ww2/images/pro_spit14_notes_24.jpg http://www.lanpartyworld.com/ww2/images/pro_spit14_notes_25.jpg They are pilots notes for a Mk XIV. It says The recommended speed for maximum range is 200-210 mph IAS. This is between 275 and 288 mph at 20,000 feet. The next page has a chart showing the miles per gallon for boost and rpm settings. Again this shows the much higher economical cruising speed. The wing loading of a MkIX spitfire at MTOW was only 30.73 lbs/ft^2. That is an even greater difference. I don't know what the wing loading for a clipped wing MkXIV would be, but it would be significantly higher. Switching to a cruise setting in a P-38 was still more time consuming than in a spitfire. The P-38 pilot had to deal with gun heaters, two fuel tank selectors and a more complex mixture adjustment.
 
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larryjcr    RE:wing loading   7/10/2005 1:08:53 AM
Shooter's comment on figuring wing loading on MTOW rather than EW led me to doing some minor number crunching. The difference between wing loading at EW and at MTOW is less than 30% for EVERY version of the Spitfire I've figured. It's over 50% for the P47D and just under 70% for both the P51D and P38J. No wonder the difference between a Spit and a Mustang is so much larger at MTOW. But the a/c obviously didn't remain at MTOW. By the time you climbed to altitude you'd already burned off enough fuel to effect the wing loaing, particularly in a Spit which carried less fuel to start with.
 
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