- Thread starter
- #121
Re-engined planes
- Thread starter tomo pauk
- Start date
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
Shortround6
Major General
So not the WEP indeed, but it also claims 90 HP less for take-off thany you do
Might depend on manifold pressure used but 1300 is a fairly common number.
True
Crappy answer----it depends. Since war emergency power is ONLY available BELOW the rated altitude of an engine (and the further below the the higher the power--within reason) and since the MAX speed of an aircraft was often reached within several thousand feet ABOVE the the rated altitude of the engine it may make no difference to the "book maximum speed". Max speed was were the thrust (power) was the greatest in relation to drag. As the airplane climbed, say to 20,000ft were the air is about 1/2 the density of sea level the drag is going to drop to 1/2 the drag at sea level. If the supercharged engine can provide enough power the plane will be faster at the higher altitude until engine power falls off faster than the drag is going down due to thinner air.
As a for instance and keeping with our P-40 motif, The P-40F is often quoted as being just a few mph faster than a P-40E for peak speed. While this is true what is often over looked is that the P-40F acieves this speed around 5,000ft higher than the P-40Eand at 20,000ft it is actually about 25-30mph faster than a P-40E and the higher you go the more advantage it has. The P-40F is slower than it's peak speed at any altitude below about 20,000ft and this is were WEP comes in. at about 12,000ft it may be doing 340mph instead of the 360+ it can do at 20,000ft. Using WEP may allow it to do 350 or a bit more (example don't quote this
which while helpful in a fight doesn't change the max speed in the brochureThe another table (down) claims cca 700 lbs less for every weight category (also from 'P-40 in action'), confirming Wiki. In the Variants P-40F Warhawk, Kittyhawk II site they post another set of data (from Joe Baugher), with values in between (6600 empty)
weights can be all over the map. The weights I gave you were for a plane 109lbs over the manufactures guarantee weight which means it was 1.25% over weight, it could just as easily been 1-1.25% under weight and once again the 'empty weight" offers the most possibility for confusion. Americans changed their weight procedure to move armor and bullet proof glass from the useful load category to the "armament provisions" category included in empty weight between the E and F models. please note that "armament provisions" does not include the weight of the guns
British "tare" weight often does not include the radio so a British prepared handbook will show different weights than an American handbook.
Question on the "designed Gross weight" the P-40 had three tanks in the fuselage, does the "designed Gross weight" include the weight of the fuel in the rear fuselage tank? which would work out to about a 45.5 US gallon difference in the weights you posted.
I will note that while the first 2 power references look OK the military one looks highly suspect. The RPM is all wrong for a military power setting on a Merlin and the altitude seems to be way too high for the power quoted.
I have found another source which gives ratings of.
take off------------------1300hp/3000rpm?+12lbs boost.
Max power (combat)---1240hp/3000rpm/+9lbs/11,500ft low gear
Max power (combat)---1120hp/3000rpm/+9lbs/18,500ft high gear
Please notice the difference in manifold pressures and also the height at which the peaks occur. 9 lbs may be all the supercharger can provide at those altitudes but at 5,000-7,000ft lower the supercharger can provide more manifold pressure due to the higher ambient air pressure. This is if the pressure regulator is adjust for it and would constitute the WEP.
WEP is also limited by not exceeding allowable coolant/cylinder temperatures and oil temperatures, subject to being shot at
Last edited:
Shortround6
Major General
Spitfires had a lower wing loading to begin with and had a shorter take-off run.
LE slats do squat for take off.
- Thread starter
- #124
Only the Seafire III (of fully navalized Sefires) had lower wing loading, but, since they managed to take off a) with bombs, and b) while using shorter deck, the navalized 'P-40s' would've be in no disadvantage there.
Later Seafires were as heavy as my 'P-40/F12C', and were still capable to take off with bombs.
The Spits have had thinner wings, so less lift there @ low speeds - advantage 'P-40'.
Sorry, I disagree
- Thread starter
- #125
...
...
WEP is also limited by not exceeding allowable coolant/cylinder temperatures and oil temperatures, subject to being shot at
(in order not to quote the whole post)
Informative - thanks
Shortround6
Major General
Would you please check your figures again, since no Seafire until the last ones ( MK 47? and such) went over 8000lbs in clean condition and NO P-40 after the C model was under 8000lbs clean (unless it had less than ful internal tanks) and since the normal Spitfire wing was slightly bigger than a P-40 wing I am having a a hard time figuring this one out.
You are counting on a generality here and neither actual lift coefficients or measured performance.
Sorry, I disagree
Well, if you can show me a lift to angle of attack chart that shows this to be true I might agree with you. Since the charts that show change in lift coefficients in relation to angle of attack don't show any real improvement over an unslatted wing until the slatted wing exceeds about a 12 degree angle of attack (and a max improvement at 18 or more degrees) I would say you are either using a very unconventional takeoff procedure or they don't do any good. Landing is another story where the glide slope angle can be combined with a nose up attitude to get the required angle of attack on the wing.
this is in regards to leading edge slats or slots and not in reference to drooping leading edges which are not the same thing.
Shortround6
Major General
(in order not to quote the whole post)
Informative - thanks
You are welcome.
Some sources I am using for engine figures are "British Piston Aero-Engines and their Aircraft" by Alec Lumsden (some of the higher ones).
"The Merlin in Perspective-the combat years" by Alec Harvey-Bailey and the Rolls-Royce Heritage trust.
Several editions of "Jane's all the Worlds Aircraft" and several editions of "Aircraft Engines of the World" by Paul Wilkinson.
- Thread starter
- #128
- Thread starter
- #129
Down is the excerpt from book 'Seafire' - all other fully navalized Seafires after Mk.III (=Merlin aboard) have had Griffon installed, and weighted from 7000 lbs empty on - same 7000 lbs I was estimating for fully navalized 'my' P-40.
Wing area was 236 ft^2 vs. 242 for Seafires = 2.5% (negligible) advantage Seafire. As you see on the table, they could take off with 500lb bomb, even from RN (= smaller than USN) carriers.
I admit that I have not dug uut the exact figures for lift coefficients; please toss some info if you find it before I do. However, I still believe that ticker wing of P-40 provided more lift
No such detailed info from me yet, but, again, toss any info (table, drawing etc) that could prove your or my claim.
FWIW, some of CV planes sported the slats (SB2C eg.), so think my claim has merit.
Attachments
- Thread starter
- #130
In my favourite master-slave vogue, here is the beefed-up P-39. The slave engine supercharger is mounted instead of 37mm, 2 x 0,50in, their ammo, and synchro gear. 4 x .50in in wings.
Sure enough, turbo-supercharger might have been installed, with exhaust gasses transferred to front (second pic).
Sure enough, turbo-supercharger might have been installed, with exhaust gasses transferred to front (second pic).
Attachments
Sort of off the topic, but related to re-engining planes, are there detailed plans that show what the initial Rolls-Royce proposal to mount a Merlin Engine behind the cockpit in the P-51 would have looked like? I've seen photos of the mock up taken from a bad angle, but no actual drawings.
- Thread starter
- #132
- Thread starter
- #134
I've attached a table from manual for Fw-190A-8 (dated sept 1944), showing that it wouldn't enjoy any power-to-weight-related advantage vs. my proposed designs ('P-40' P-43) using R-2600 (1700 HP in 1942, 1750 in 1943, 1900 in 1944, without any development it might have received).
Eg. the R-2600 from 1943 was able to produce:
Eg. the R-2600 from 1943 was able to produce:
while driving planes of well under 7000 lbs empty equipped.
Attachments
Last edited:
- Thread starter
- #135
In order to avoid problems with BMW-engined Fw-190, RLM might have ordered such a hybrid: Fw-190 with DB-601E/605A.
3 cannons (one central, two in wings - firing out of prop disc), glycol radiator under the engine, in enlarged cowling together with oil radiator. Though nominally with 10% less power, the weight would've also go down (no hull MGs, their ammo synchro gear), while DBs offered greater reliability then 801 prior 1943. And difference of power at altitude would've been negligible. Drag would've been reduced a tad.
The versions with 1800-2000 HP in DB-605AS/AM/D would've been awesome.
3 cannons (one central, two in wings - firing out of prop disc), glycol radiator under the engine, in enlarged cowling together with oil radiator. Though nominally with 10% less power, the weight would've also go down (no hull MGs, their ammo synchro gear), while DBs offered greater reliability then 801 prior 1943. And difference of power at altitude would've been negligible. Drag would've been reduced a tad.
The versions with 1800-2000 HP in DB-605AS/AM/D would've been awesome.
Attachments
Last edited:
Shortround6
Major General
The US Navy and the RN operated a bit different. US Navy liked to use large deck parks (many aircraft occupying the aft end of the flight deck) and while they could catapult some aircraft the idea was to fly off as many as possible without using catapults for a much faster pace of operations. This obviously limits the take-off distance to somewhat less than the full length of the carrier. The RN was much more likely to only have a few planes on deck at a time , slower pace but higher percentage of deck available.
I admit that I have not dug uut the exact figures for lift coefficients; please toss some info if you find it before I do. However, I still believe that ticker wing of P-40 provided more lift
Well, for an early Spit
fire see: Spitfire Mk I N.3171 Trials Report
Notice the difference just propellers can make.
For a later Spitfire see: http://www.spitfireperformance.com/spitfire-fix-ads.jpg
500yds to 50ft at 7450lbs
For a P-40E see: http://www.zenoswarbirdvideos.com/Images/P-40/P-40TOCLC.pdf
1800ft (600yds) to 50 ft at 7500lbs.
Granted the MK IX has a bit more power but I am not seeing a advantage to the P-40s thicker wing.
See: chapt4
GO down to figure #63
quote"Slots.- The maximum coefficient of lift may be increased through the use of a slot formed by a leading-edge auxiliary airfoil called a slat. Figure 63(a) illustrates the operating principle. When the slot is open, the air flows through the slot and over the airfoil. The slot is a boundary-layer control device and the air thus channeled energizes the boundary layer about the wing and retards the separation. The airfoil can then be flown at a higher angle of attack before stall occurs and thus get a higher... CL,max value. A curve showing CL as a function of a [Greek letter alpha] for the normal and the slotted airfoil is given in figure 63(b). Notice particularly that for angles of attack less than the stall angle, the airfoil lift curve is relatively unaffected whether the slot is opened or closed."
Slats do work for landing and they help a lot with maintaining aileron control at speeds close to stall.
I have seen other charts and have a few in books but my scanner skills are weak
Shortround6
Major General
Where are you getting the "well under 7000 lbs empty equipped"from?
The Fw 190 you are quoting is listed as 7608lbs empty equipped. Granted it has 2 to 2 1/2 times the fire power of a four .50 cal plane (or more) .
An old book lists weights for the FW 190A-3 as 6,393lbs empty, 7,110lbs empty equipped and 8770lbs loaded. This is for 7.9mm cowl guns, MG 151 in the wing roots and MG/FF guns in the wings.
Empty equipped for a P-40E is 6700lbs and for the F is 6980lbs and that is with engine weights 3-400lbs lighter than the R-2600 (including radiator and coolant) . Dropping a pair of .50 cal guns isn't going to cut it. Chopping the wing to 200sq ft might save you 172lbs at the very best.
As far as the comparisons to the FW 190 goes the R-2600 cowling is going to be 6-8in bigger in diameter than the BMW 801 cowling. This trivial 6in increase actually means about a 24% increase in frontal area.
As your own figures show the FW 190 has about a 3,700ft altitude advantage. or to put it another way the R-2600 would be putting out approximately 1250hp at the altitude the FW has 1420Hp.
By the way the R-2600 received a fair amount of development, Difference between 1600hp and 1700hp models was a change from a forged aluminum crankcase to a forged steel crankcase among other things. The Steel crankcase had the strength to allow for the higher rpm. The 1900hp models changed from cast cylinder heads to forged heads and changed from machined cooling fins on the cylinder barrels to sheet metal fins rolled in machined grooves called "W" fins. Considerable retooling of the factory was needed to change over. The Stronger cylinder heads and much increased cooling fin area allowed for the higher power output. There may have been other changes too.
- Thread starter
- #138
Okay, then we'd launch Dauntleses 1st
Well, for an early Spit
fire see: Spitfire Mk I N.3171 Trials Report
Notice the difference just propellers can make.
For a later Spitfire see: http://www.spitfireperformance.com/spitfire-fix-ads.jpg
500yds to 50ft at 7450lbs
For a P-40E see: http://www.zenoswarbirdvideos.com/Images/P-40/P-40TOCLC.pdf
1800ft (600yds) to 50 ft at 7500lbs.
Granted the MK IX has a bit more power but I am not seeing a advantage to the P-40s thicker wing.
Tnx for a thorough info.
The Mk.IX have had 25% more power for take off than P-40E later, and that is quite a lot. The R-2600 of the same era have had the same power for TO as Merlin 60 series
See: chapt4
GO down to figure #63
quote"Slots.- The maximum coefficient of lift may be increased through the use of a slot formed by a leading-edge auxiliary airfoil called a slat. Figure 63(a) illustrates the operating principle. When the slot is open, the air flows through the slot and over the airfoil. The slot is a boundary-layer control device and the air thus channeled energizes the boundary layer about the wing and retards the separation. The airfoil can then be flown at a higher angle of attack before stall occurs and thus get a higher... CL,max value. A curve showing CL as a function of a [Greek letter alpha] for the normal and the slotted airfoil is given in figure 63(b). Notice particularly that for angles of attack less than the stall angle, the airfoil lift curve is relatively unaffected whether the slot is opened or closed."
Slats do work for landing and they help a lot with maintaining aileron control at speeds close to stall.
I have seen other charts and have a few in books but my scanner skills are weak
I think that pushing a plane to take advantage of greater AoA would permit it to reduce TO distance, or to take off with greater load from same TO strip.
- Thread starter
- #139
P-40F (6 MGs) was 6300 lbs empty equipped. We delete 2 MGs and their ammo (-180 lbs for guns only), and substitute the engines (+400 lbs, if even so). Result is circa 6500 lbs for P-40 with R-2600.
Of course, but we do not need such firepower - no heavy bombers to take down.
Yep, think those figures are pretty accurate - the A8 paid the price for it's heavy punch. OTOH, the engine of A3 not as reliable as later BMWs, nor as many contemporary Allied Axis engines in wide use, and the plane would be still some 600 lbs heavier then a 4-gun P-40 with R-2600.
Please re-check your figures. Down is the table with weight for P-40N variant that reinforce my figures.
The difference in engine diameters is 4in, so the cowl would've been that much wider.
Sure, but it has to pull a 1000 lbs heavier plane
Of course it received the development, but never received ADI, nor it was tasked to qualify for military rating.
Attachments
Shortround6
Major General
Uh, pushing a plane to take advantage of a greater angle of attack how?
Plane accelerates down the strip, tail comes up and angle of attack on the wing falls to near zero, Or for trike gear aircraft angle of attack stays low until nose wheel comes of the ground.
Trying to pull the plane up too soon means it stalls and crashes back on the runway or you force the tail back down and increase drag while partially blocking the tail surfaces.
The idea is to get to flying speed as soon as possible. I still can't see how trying to taxi/accelerate down the runway/carrier deck with the wing tilted at 12 degrees or better is really going to work.
