Fester's Drop tank rack test results (testing requested)

[Citabria]

I was curious to see the impact of the drop tank rack on top speed so I tested it using the e6b. it seems the higher the speed the slightly higher the drag penalty.  thanks to banshee7 for help testing.

tests conducted at 5000 feet. wep off. 100% fuel. if rack taken drop tank dropped before engine start. smallest ammo load taken.

fw190a8 348mph. 342mph with rack. -6mph

fw190a5 352mph. 345mph with rack. -7mph

fw190d9 367mph. 359mph with rack. -8mph

Ta152 353mph.  353mph with rack. -0mph

Bf109f4 328mph. 324mph with rack. -4mph

Bf109g2 349mph. 344mph with rack. -5mph

Bf109g6 342mph. 337mph with rack. -5mph

Bf109K4 367mph. 362mph with rack. -5mph (WEP 397mph. 391mph with rack. -6mph)

Spitfire XVI 336mph. 336mph with slipper tank rack. -0mph

f4u1a 353mph. 346mph with rack. -7mph

f4u1d 345mph. 345mph with built in racks -0mph

(if you have a favorite airplane you would like to test head to the training arena and use 5000 feet wep off and record level speed after it stabilizes (3-4 minutes) with and without the drop tank rack. don't take gun pods. just take the smallest ammo load and 100% fuel.)

thanks.

[Banshee7]

Thanks for the info Fester:aok

#S#

Banshee7

[Citabria]

ki84 343mph. 343mph with racks. -0mph

i don't think any other planes have rack drag modelled as they are all older models. except the p38 p51 and p47 which all have racks fixed that can't be removed thus shouldnt have more drag from carrying tank racks.

[Karnak]

I think the Ki-84's racks are fixed as well, thus the 0mph difference.

[Guppy35]

Fester, are you talking about the bomb racks on the Spit 16 wing?  There was not drop tank rack since it was a slipper tank on the centerline that didn't have a rack, just a couple of small stops that caused the drop tank nose to fall forward and away from the fuselage after it was released.  

The wing racks were standard to the late E Wing on the Spit as it was strengthened a bit to handle the bombs carried on the wing.

[Citabria]

just the slipper tank attachment mechanism guppy. no pylons for ordnance or anything was looked at.

adonai told me the other day spit16s had a performance hit from the slipper tank mechanism but seems to not be the case.

[kozhedub]

Seems taking the tank on the D-9 is simply not worth cost incurred in drag/speed.

-1A as well .

Better to use lower rpm settings to extend internal fuel.

[Widewing]

Fighters That I have previously tested that have bomb rack drag calculated into the basic drag model included those listed below. These aircraft do not show any measurable loss of speed if initially fitted with bombs or drop tanks. There may be others not tested yet. Adding rockets is another story as rocket tabs, rails and tubes DO have a drag penalty.

P-38G
P-38J
P-38L
P-40E
P-47D-11
P-47D-25
P-47D-40
P-47N
P-51B
P-51D
N1K2-J
Ki-61
Ki-84
F4F-4
FM-2
F4U-1C
F4U-1D
F4U-4
F6F-5
Typhoon
Tempest
Spitfire Mk.VIII
Seafire Mk.II
La-5FN
La-7

At 5k in MIL power, the Spitfire Mk.XVI loses 3 mph (335 mph vs 338 mph) if you add wing racks. There is no measurable loss for taking a centerline bomb or slipper tank (like the Mk.VIII).

My regards,

Widewing

[Banshee7]

I ahd the pleasure of Helping Fester get some of these numbers.  We had a great time shooting the $*** while our planes were topping out.

#S# Fester

#S#

Banshee7

[Capt.Joe]

Yeah, what about tests with rocket rails?

[mtnman]

Originally posted by Citabria
... it seems the higher the speed the slightly higher the drag penalty...

 

It's been a long time, but from what I remember drag does increase as speed increases, at least to a point.  

For example- at the extreme low end, does the bomb rack cause any drag at all if the plane isn't moving, or if there is no airflow across it?  The drag penalty would increase with airflow, and would be less at 25mph than at 250mph.

I would expect the drag penalty of the bomb rack would be less noticable at low speed, but more noticable at high speed.

Based on this argumant, a bullet would decelerate quickest at its initial high velocity, but the rate of deceleration would decrease as its speed decreases.

I really can't remember how to explain it, high school was a long time ago.  Maybe a phyics guru could explain it better (maybe even correct my errors...)

MtnMan