FLYBOYJ
"THE GREAT GAZOO"
Says the non-pilot who read the manual.
Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (1 Viewer)
- Thread starter greybeard
- Start date
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GregP
Major
I wonder if he is a member of the flat earth society ... I personally know 3 or 4 people who have sailed around the world without falling off the edge. But maybe that's hearsay.
It is all taking on an air of comedy now.
drgondog
Major
Gently, use your vast analytical abilities and do a weights and balance chart for the the P-39Q (just the engine for simplicity) versus the P-63C.. Use the V-1710-85 at 1397# for the P-39 and V-1710-117-E21 at 1710#. Add Water Injection System weight of 50#(NOT INCLUDING WATER) and note that the empty weight has grown from ~ 5680 # (P-39Q) to 6850 (P-63C).
Especially notice that a.) The 'New mass' center moves to the rear as that is only possible space for auxiliary 2nd stage supercharger, and that b.) that the new mass of the new engine variant is not only greater by 360 pounds, but has moved at least least 6" rearward - in an airframe that already has major aft CG issues. and you have an empennage pitch control aerodynamic center at the same location from 'old P-39 CG' instead of installing a section aft of the cockpit to extend the empennage pitch control aerodynamic center - and haven't added vertical tail area to compensate for the yaw stability inherent in the P-63.
Imagine the built in aft CG condition as 'best possible' flight condition which only deteriorates when forward stores are expended? Imagine the increase in pitch sensitivity and tendendcy for stick reversals at all speeds. Imagine that moving the CG aft from Center of Pressure of wing is destabilizing to pitch control
Remember that you still have the small horizontal/vertical stabilizer of the P-39 (86% total Horizontal Stab Area of the P-63 H.Stab), a CG that has moved 6+in to rear of the production P-39Q.
In your infinite control of the pilot's operating manual is there a section that warns you about field mounting a 250 pound bomb under the engine compartment and asking a pilot to volunteer for the first flight?
buffnut453
Captain
Remember when I posted the Blackadder clip several pages ago? Told ya so!!!
Glider
Captain
As I am afraid we have all come to expect, you have proven nothing, absolutely nothing.
On one side we have the obvious,
1) How come you know more than the tens of thousands of engineers who knew every inch or the aircraft
2) How do you know more than someone who actually has access to the real aircraft
3) How do you know more about the balance of the aircraft than the people who designed, built, flew and too often died in the aircraft.
4) How you know more about the range of the aircraft, than the people who flew it and planned the missions
On the other side we have
1) I read a manual (badly, incorrectly and with more than a little selectivity when picking details)
If you were neutral, which argument would you give credence too?
GregP
Major
He's not neutral. Definitely in P-39 gear.
P-39 Expert
Non-Expert
AUX stage SC weighed about 170lbs and replaced the coolant tank that was moved forward behind the pilot. Moving the carbueretor from the aux stage to normal position on the engine stage SC would move a little weight forward also. Heavier 4 blade propeller would offset the weight of the aux SC. May need some ballast, maybe not.
wuzak
Captain
Maybe the supercharger itself weight 170lbs, but what of the other bits and pieces to make it work, such as the extension shaft and hydraulic drive, step up gears, etc?
drgondog gave you the weights of a single stage V-1710 and a 2 stage V-1710, which was a difference of 360lb. You're only allowing for half that?
May need some ballast? Like nose armour, perhaps?
P-39 Expert
Non-Expert
AHT says the P-39 engine weighed approx 1435lbs and the P-63 engine weighed 1620lbs. 185lbs difference.
Yes, the nose armor may be needed to be added back if ballast is needed.
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Why not use cast iron in the front fuselage? Cheaper and heavier, thats a real win-win.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I never would have thought of that.
P-39 Expert
Non-Expert
I don't and never claimed to.
I have also had access to the real aircraft, the one at the CAF museum in San Marcos. And I have seen plans and diagrams.
On this board we have diagrammed the balance many times.
There is a very simple chart in the pilot's manual. And reading Edwards Park's book about the P-39 in NG. And AHT, Vees for Victory, and many other reference books.
Have you read the manual? Read the Flight Information Instruction Chart? Figured range and radius for yourself?
Almost all of my arguments reference an original source document such as a Wright Field performance test from wwiiaircraftperformance.org, a pilot's manual, or a reference book.
Thats where the logic of these arguments go. You dont just add a bit here and there. I remember seeing CoG calculations on a Spitfire stating how much it was changed by lowering the undercarriage. It was a fraction of an inch, but it was measured as all these things were. If you look at how it pivots the wheels move forward as they are lowered, that changes the CoG.
drgondog
Major
Laughing loud at your ignorance. People who are stupid don't know they are stupid. DO THE EFFING MATH on the CG movement to install a heavier engine and supercharger/WI system in an airframe that required extending the length TWO FEET - Eight Inches behind the wing aerodynamic center - in order to move the H.Stab aerodynamic center Two feet further aft and increase the EFFING Empennage area 20% to be able to FLY the P-63 with the new engine/Water Injection.
I have to admit that I have confronted the most clever troll or stupidest debater in my 75 years of reasonably enjoyable life. You should be proud - either way - as I have seen and met many of both types. My hat is off to you.
Shortround6
Major General
Unfortunately actual facts are ignored if contrary to the desired narrative.
Yes the coolant tank was relocated. But it was the overflow/expansion tank. If I recall correctly it held 3 1/2 gallons (or 2 1/2?).
This hardly compensates for the aux supercharger. The rest of the coolant stays in the engine and the radiator (original location/distance from CG).
This has been gone over before.
But as usual the experts arguments revert back to the original misconceptions.
Yes the coolant tank was relocated. But it was the overflow/expansion tank. If I recall correctly it held 3 1/2 gallons (or 2 1/2?).
This hardly compensates for the aux supercharger. The rest of the coolant stays in the engine and the radiator (original location/distance from CG).
This has been gone over before.
But as usual the experts arguments revert back to the original misconceptions.
Thumpalumpacus
Major
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
So far we've covered every aspect except the weight of the marker lamps (nav lights) and the air pressure in the tires...
Thumpalumpacus
Major
Wooden empennage. Don't forget the wooden empennage.
