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323 | Speed Spitfire | Modified Mk I for an attempt on the world speed record and first flew on 11 November 1938 and would eventually reach a top speed of 408mph. Unfortunately rival aircraft in Germany were approaching 470mph and the Speed Spitfire project lapsed. |
I dont know anything about the speed Spitfire really but unless Supermarine were told to do it by the government, every hour spent was an hour wasted, around 1938 Supermarine almost lost the contract for Spitfires because they werent making nearly enough, messing about with a record breaking version wasnt in the plan. In any case the Mk IX that appeared only 4 years later was faster with all the wheels guns and armour of a fighting planeThank you so much pbehn!
Yes, you're definitely right. In those years the engine development proceeded extremely fast. Therefore in a few years the developed hp on average were almost doubled!I dont know anything about the speed Spitfire really but unless Supermarine were told to do it by the government, every hour spent was an hour wasted, around 1938 Supermarine almost lost the contract for Spitfires because they werent making nearly enough, messing about with a record breaking version wasnt in the plan. In any case the Mk IX that appeared only 4 years later was faster with all the wheels guns and armour of a fighting plane
There is a small amount in my book about it, but 408 mph (true) at 3000ft was the actual test result. Engine power was 1990 bhp at 3000rpm, this was reported on 30th may 1939. Prediction without a radiator was 425mph. Drag was 53.3lbs at 100ft sec (standard spitfire was 60.2lbs). It had a Watts four bladed fixed pitch propeller of 9.75ft dia, giving .832 relative Mach tip speed at 400mph, using the RAF 6 profile.Hi everybody,
Reading the Valiant publishing concerning the Spitfire Merlin powered versions I came to know about a special version of this legendary aircraft: the "Speed Spitfire". It was a modified version of the Mk. I Spitfire created in 1937 to beat the world top speed record. Unfortunately, this project turned out to be quite disappointing, since while remarkable steps were made towards increasing the Merlin engine power, german competitors such as the He 100 and the Me 109 R (or Me 209) ketp to increase the speed to be overtaken.
I became rather curious about this shiny, blue, Spit, but I can't find any futher information about it and, in particular, there is no apparent record of its maximum speed. This seems to be really absurd for an aircraft nicknamed as "Speed" Spitfire.
I would be really grateful if someone could kindly share any information about it.
Below there is a beautiful photograph of the Spitfire N.17 aka Speed Spitfire.
Thanks a lot in advance!
View attachment 643186
(source: Speed Spitfire N.17)
...unless Supermarine were told to do it by the government, every hour spent was an hour wasted, around 1938 Supermarine almost lost the contract for Spitfires because they werent making nearly enough, messing about with a record breaking version wasnt in the plan.
I have seen several times in books and websites that drag is reported for a speed of 100 ft/s, which is only 68 mph or 110 km/h.There is a small amount in my book about it, but 408 mph (true) at 3000ft was the actual test result. Engine power was 1990 bhp at 3000rpm, this was reported on 30th may 1939. Prediction without a radiator was 425mph. Drag was 53.3lbs at 100ft sec (standard spitfire was 60.2lbs). It had a Watts four bladed fixed pitch propeller of 9.75ft dia, giving .832 relative Mach tip speed at 400mph, using the RAF 6 profile.
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As a guess I would think that is the fastest wind tunnel they had at the time.I have seen several times in books and websites that drag is reported for a speed of 100 ft/s, which is only 68 mph or 110 km/h.
That's the speed of a motor car, not a fighter plane that can fly about a factor 6 faster.
I know that drag increases with speed squared (for a given air density), but that is only so if the drag coefficient of the plane would be independent of speed, which I don't think is true as Reynolds and Mach numbers will be different at different speeds.
Measuring drag at 100 ft/s and then having to multiply this number by 36 to estimate drag at 600 ft/s seems rather primitive to me.
Does anybody here know why drag often was measured at only 100 ft/s ?
My father worked within a few hundred feet of the NACA/NASA Langley wind tunnels (there were several) for nearly 40 years, and a close friend who is about to retire was part of the team who operated this tunnel. Growing up 3.5 miles away in the 60s-80s, we could hear the tunnels roar when they were being operated.This tunnel which helped USA win the war according to the article operated at upto 120 MPH on a full size single seat fighter, it became operational in 1934.
I`m only a stupid mechanical engineer, not a proper aerodynamicist, but I would think it would be useful to have a look at Reynolds at sea level and room temperature at 100f/s and then compare that with reynolds at 300mph at atmospheric conditions prevalent at say...30,000 feetI have seen several times in books and websites that drag is reported for a speed of 100 ft/s, which is only 68 mph or 110 km/h.
That's the speed of a motor car, not a fighter plane that can fly about a factor 6 faster.
I know that drag increases with speed squared (for a given air density), but that is only so if the drag coefficient of the plane would be independent of speed, which I don't think is true as Reynolds and Mach numbers will be different at different speeds.
Measuring drag at 100 ft/s and then having to multiply this number by 36 to estimate drag at 600 ft/s seems rather primitive to me.
Does anybody here know why drag often was measured at only 100 ft/s ?
I disagree. The work was done under an Air Ministry contract. In any event, the airframe mods weren't really that extensive. New windscreen, new wingtips, new engine mounts, flush rivets. The major mod was the new pressurized cooling system. The Speed Spitfire was the first Merlin powered aircraft to fly with the pressurized cooling system. The once through system was a later modification. In fact, Rolls Royce learned a lot about the capability of the Merlin and the whole experiment was worth it for that alone.I dont know anything about the speed Spitfire really but unless Supermarine were told to do it by the government, every hour spent was an hour wasted, around 1938 Supermarine almost lost the contract for Spitfires because they werent making nearly enough, messing about with a record breaking version wasnt in the plan. In any case the Mk IX that appeared only 4 years later was faster with all the wheels guns and armour of a fighting plane
I`m only a stupid chemical engineer, not a proper aerodynamicist either, but familiar with Reynolds numbers in other situations.I`m only a stupid mechanical engineer, not a proper aerodynamicist, but I would think it would be useful to have a look at Reynolds at sea level and room temperature at 100f/s and then compare that with reynolds at 300mph at atmospheric conditions prevalent at say...30,000 feet
I was sort of putting a time scale to the issue, the UK were commissioning tunnels through the 1930s. The Speed Spitfire was abandoned in 1938, that NACA tunnel was state of the art in 1934. The thing is everyone wanted to use wind tunnels, in UK or USA I doubt a racing plane would get priority over a military project unless orders came from very high up. Also it is easy to say "only 100 ft/sec". A hurricane force wind is 74 MPH and above, even these slow wind tunnels were recreating a hurricane force wind, but it has to be of known and reproducible speed, with smooth flow and precise measurements of forces need to be taken.I guess pbehn could be right that in Britain the fastest full-size wind tunnel at that time operated at only 100 ft/s, although NACA managed 178 ft/s (120 mph) but I guess they had a bigger budget.