WesWorld

I think I've spotted a problem with water-cooled engines and Planebuilder: in general, it doesn't, and can't, take into account the weight of the radiator, piping, and coolant for the engine unless we input it. It's relatively easy to find the dry weight for lots of historical engines, and to come up with an estimate for a non-historical engine, but that doesn't include the radiator's weight, or the weight of the coolant. Anyone have a good approximation system for determining this weight? Or at least a set of data points?

Dry weight is just the engine weight sans fluids. The amount of coolant is ~ displacement and weighs less than water so maybe adds 20-30kg weight. I'm not sure whether the engine weight given in most sources includes the radiator and accessories. I'll look into it.

There is also no allowance for things like oil reservoirs, for example I think it was the P-47 that had a 50-gal oil reservoir behind the engine (or I could be remembering something wrong).

My assumption on these matters is that since RL planes sim fairly well using the dry weight engines, and the wet weight is so hard to find, that the designer of Planebuilder probably built it around dry weight engines and those weights likely wound up incorporated into the structure. Granted, that's pure conjecture, but it seems to make sense.

I found a report on the Bf-109 G-2/Trop that included some of this data: it included the size and weight of the radiators and head tanks, along with their capacity. The report is here: http://kurfurst.allaboutwarfare.com/Tact…_WdimPerf.html, while the numbers were 2 coolant header tanks (total weight: 7.3 pounds, total capacity 2.2 gallons) and 2 coolant radiators (total weight 262 pounds, total capacity 2.8 gallons). It doesn't mention what the total coolant capacity is, I'd assume the entire system (between the engine and the fluid lines) holds 2--4 times the radiator/head tank capacity, so somewhere from 10-20 gallons.

Quoted

Originally posted by Kaiser Kirk
There is also no allowance for things like oil reservoirs, for example I think it was the P-47 that had a 50-gal oil reservoir behind the engine (or I could be remembering something wrong).

My assumption on these matters is that since RL planes sim fairly well using the dry weight engines, and the wet weight is so hard to find, that the designer of Planebuilder probably built it around dry weight engines and those weights likely wound up incorporated into the structure. Granted, that's pure conjecture, but it seems to make sense.

The oil reservoir, oil coolers, etc, would be common between radial and in-line engines, so their weight could be subsumed into the program's calculations. However, the weight of radiators and their associated fluids are missing from air-cooled engined planes, the author couldn't include that weight into the program without some sort of switch, which I haven't seen.

Well here's an example of a historic plane simmed.
The Belgian Renard R-36. Engine is right, armament & payload (1x20mm, 4x mg, 8*10kg) is right. Max weight is correct, but sims as +300lbs more light. and very close for altitude. Speed is +3knts from historic.

Perhaps there is no specific accounting for the wet weight, but the model works to replicate the real life plane. So that weight is absorbed into something already. I don't think it is necessary to add weight.



R-36

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1937

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

Renard Fighter R-36, as historic. 1x 20mm, 4x 7.92mm



Characteristics:

Weight (maximum) 4,851 lbs
Weight (empty) 3,997 lbs

Length 28.018 ft
Wingspan 38 ft
Wing Area 205 sq ft
Sweep 6 degrees

Engines 1
Hispano-Suiza 12Y crs
Piston

898 hp
at 9,000 ft


Crew 1


Typical cost $0.028 million in 1935
Total number procured 32


Performance:

Top Speed 276 kts = 317 mph
at 9,000 ft
Mach N/A

Operational Ceiling 39,370 ft

Range 540 nm = 622 miles
with 175 lbs payload
183 lbs released at halfway point

Climb 2,683 fpm

Cruise 216 kts = 248 mph
at 24,000 ft

Corner Speed 192 KIAS =
219 kts at 9,000 ft
Mach N/A
Turning Rate 27.7 deg/sec
Radius 1,529 ft



Internal Data:

Intake / Fan Diameter 10 ft

Bypass Ratio 112.6

Engine Weight 1180 lbs
Overall Efficiency 22 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 290 kts
Wing Ultimate g Load 9.00 g
Wing Taper 0.5
Wing Thickness at Root 1.4 ft

Tail / Canard Factor 0.5

Number of Nacelles 0
Length 23 ft
Diameter 3.3 ft
Fullness 0.4

Fuselage Diameter 3.4 ft
Fuselage Fullness 0.3

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 72 percent
Unstreamlined section 1.6 sq ft

User equipment 700 lbs



vs. Real life


Sizes and weights
Total Length : 28.018 ft 8.540 m
Greatest height : 9.514 ft 2.900 m
Wingspan : 38.189 ft 11.640 m
Wing area : 204.516 sqft 19.000 qm
Max take off weight : 4851.0 lbs 2200.0 kg
Weight empty : 3307.5 lbs 1500.0 kg
Performance data
Max. speed : 273 kts 505 km/h
Landing speed : 62 kts 115 km/h
Cruising speed : 216 kts 400 km/h
Service ceiling : 39370 ft 12000 m
Wing load : 23.78 lbs/ft2 116.00 kg/qm
Range : 540 nm 1000 km
Propulsion
Kind : KVau
Type : Hispao Suiza 12 Y crs
Power rating (max.) : 898 hp 910 ps
Count : 1 1
Total power rating (max.) : 898 hp 910 ps
Other
Crew : 0 0
1
1
Armament : 1* MG 20mm, 4* MG Browning, 8* 10Kg Bomb.

There's not much difficulty in simming real-world planes, since there a number of areas in the model that can be tweaked to get the numbers close to right. Adjust cleanness up or down, max design speed, etc. All those things can be manipulated to get the sim to reflect real life.

What I'm concerned about more is things that are new, like for instance my DB-601 powered Fw-187A. The numbers look OK, in general, but...... I'd like to get it closer to what it should be, and an estimated cooling system weight will help that, for water-cooled engines.

Based on the data for the Bf-109 G-2, a quick approximation might be as simple as 10 pounds of cooling system per liter of displacement (for a pressurised cooling system). An unpressurized system, like on the Jumo-211, would either need a larger, heavier cooling system, or it would be limited at higher altitudes because it couldn't keep the engine cool. However, more data points would certainly be helpful.

Kirk, the problem with simming historical planes is that you don't know their limiting airspeed or gee factors.

I did a sim of the Re 2005 as I have loads of information on it and it came out about 600lbs too heavy. I suspect the weight difference is mainly due to the armament weight input being "dodgy"

I had put up the Renard because it was nice and close, but I had kept the limiting airspeed and G ratings down already to make Planebuilder work well. I have had problems with other historical aircraft, usually with the Planebuilder product coming out too heavy.

Anyhow, on the Renard, can we squeeze in a cooling system ?

Looking at the Renard for weight savings, I did find I was using the Pegasus 1,180lb instead of the Hispano-Suiza 1,036. There is another 54lb slop in the user weight. But the wing thickness scales right, the 9G loading is already below the recommended 10G for fighters, and the max design speed is only 6% more than the max speed, and should be more, not less.

Dropping the max design to the max speed and lowering the loading to 2G works& but is not reasonable. The payload needs to be 80kg (I put ammo in user weight) , and the base gun and ammo weights look reasonable, but the braced amounts could be off.

There is just not 360lbs (36L engine) of 'savings' to have.

As a conceptual matter, I do understand. If the consensus is to add a cooling system, eh ok, I can live with that.

I've approached it more from the thought process that radials are being doubly punished, once by their wider front area, and second by loosing much of their weight advantage since the liquid cooled engines are dry weighted. Unfortunately, if I am correct (and I could be wrong&horrors) in my supposition that the coolant system weight is already accounted for by inflated weights of other systems, it would be hard to correct.

I think the flaw is that radials get punished. There are several courses of action
-ignore it all,
-assign an weight (like Hrolf 10lbs x L) for cooling systems to liquid cooled engines, which may historical liquid cooled planes get hard to sim as a base,
-give radials a weight reduction to compensate for their lack of a cooling system. This could be -10lbs x L.
-some other course of action

There are, from my perspective, 2 flaws: 1, air-cooled engines get punished; 2, large liquid-cooled engines get a big break.

One place that might get some weight back on the Renard is classing it as a Conventional aircraft, rather than Carrier/Rough Field. For the day, taking off and landing on grass strips was the norm, nothing special, as opposed to having to have the additional bracing/reinforcement necessary to operate on a carrier.

While I agree with #1, I'd have to try some sims of late war planeswith bigger engines to see if I agree with #2.

As for conventional vs. rough field / carrier... yes, I'm expecting the normal to be "rough" grass strips, vs. a "conventional" paved airstrip. That selection is not meant to indicate carrier, just rough/unpaved airstrips. The PB Notes section does say that prior to 1930 or so you can ignore the distinction (and I presume go with the conventional).

Quoted

Originally posted by Kaiser Kirk
As for conventional vs. rough field / carrier... yes, I'm expecting the normal to be "rough" grass strips, vs. a "conventional" paved airstrip. That selection is not meant to indicate carrier, just rough/unpaved airstrips. The PB Notes section does say that prior to 1930 or so you can ignore the distinction (and I presume go with the conventional).

Judging by what I can find, rough/unpaved strips are the norm through the end of WWII, the paved strips we're used to were built during the war years to support large aircraft like the B-29.

Well wasted part of my lunchtime fiddling around trying a Hawker Tempest. There are, however, some big variables- armor weight (I used two 10mm disks), seal sealing tank weight (weighed 109kg in a P-39D, which had 120gal, so figured 327kg for 360gal).

Wing thickness, I took the default and subtracted 8" as I noted a reference to a 8" reduction from the typhoon. Fuseulage diameter had to be big enough for the Centaurus variant, so about 5 ft. Unstreamlined cross section is only 1/2 of a radial to account for the chin radiator. The maximum design speed is likely low, as my abbreviated search for data found indications of over 480mph/ 413kts in dives. Rate of climb is low and light weight is high.

So there is room for improvement.

But, I've got the dimensions close to right, efficient cruise speed, within a couple MPH for max speed at 17,000, and payload correct.

Overall it works out fairly close, though I can see a number of things I could push one way or the other, it doesn't look to me like it needs a 370lb cooling system to make it sim out correctly, and that would just further raise the light weight, and likely require reduction in the max design speed, which is likely inadequate already.

It's a quick rough sim, so there is likely things to improve.

Aircraft Type or Name:

Hawker Tempest V series 2

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1940

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

Attempted Sim of Tempest fighter/bomber. Self sealing tanks 1kg/3kg fuel. For 360gal, 711lbs for tanks



Characteristics:

Weight (maximum) 13,640 lbs
Weight (empty) 10,144 lbs

Length 33.7 ft
Wingspan 41 ft
Wing Area 302 sq ft
Sweep 5 degrees

Engines 1
Napier Saber IIB
Piston

2,400 hp
at 17,000 ft


Crew 1


Typical cost $0.063 million in 1944
Total number procured 128


Performance:

Top Speed 382 kts = 439 mph
at 17,000 ft
Mach N/A

Operational Ceiling 36,000 ft

Range 643 nm = 740 miles
with 2,031 lbs payload
2,128 lbs released at halfway point

Climb 3,356 fpm

Cruise 214 kts = 246 mph
at 11,000 ft

Corner Speed 290 KIAS =
347 kts at 12,000 ft
Mach N/A
Turning Rate 34.7 deg/sec
Radius 1,934 ft



Internal Data:

Intake / Fan Diameter 11.9 ft

Bypass Ratio 80.27

Engine Weight 2502 lbs
Overall Efficiency 25 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 400 kts
Wing Ultimate g Load 10.00 g
Wing Taper 0.4
Wing Thickness at Root 1 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 7 ft
Diameter 4 ft
Fullness 0.4

Fuselage Diameter 5 ft
Fuselage Fullness 0.3

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 82.5 percent
Unstreamlined section 2 sq ft

User equipment 2,722 lbs

Here's a counter-example: the He-100 D-1. The engine weight has been bumped up by 337 pounds to account for a 33.7 l engine. The empty weight is LOW, by 97 pounds, while the max speed is dead on, the max range is right, and the loaded weight is dead on.

Aircraft Type or Name:

Heinkel He-100 D-1

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1939

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

The initial service version of the He-100. Equipped with 1 20mm MG-FF in the engine block and 2 7.92mm MG-17s in the wings.



Characteristics:

Weight (maximum) 5,512 lbs
Weight (empty) 4,466 lbs

Length 27 ft
Wingspan 31 ft
Wing Area 156 sq ft
Sweep 0 degrees

Engines 1
DB-601M
Piston

1,184 hp
at 15,000 ft


Crew 1


Typical cost $0.027 million in 1939
Total number procured 2000


Performance:

Top Speed 362 kts = 416 mph
at 15,000 ft
Mach N/A

Operational Ceiling 37,000 ft

Range 500 nm = 576 miles
with 383 lbs payload
398 lbs released at halfway point

Climb 3,147 fpm

Cruise 250 kts = 288 mph
at 28,000 ft

Corner Speed 252 KIAS =
317 kts at 15,000 ft
Mach N/A
Turning Rate 21.3 deg/sec
Radius 2,890 ft



Internal Data:

Intake / Fan Diameter 10 ft

Bypass Ratio 95

Engine Weight 1657 lbs
Overall Efficiency 22.5 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 450 kts
Wing Ultimate g Load 10.00 g
Wing Taper 0.6
Wing Thickness at Root 1.3 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 9 ft
Diameter 3.25 ft
Fullness 0.5

Fuselage Diameter 3.25 ft
Fuselage Fullness 0.35

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 90 percent
Unstreamlined section 1.2 sq ft

User equipment 500 lbs

Nice Sim. My poor Fokkers will struggle to keep up until I ditch the low wing loading.

What I wonder is if the He-100D-1 lacked armor and self sealing tanks. The BF-109E-4 had armor and I believe was about the same time frame, certainly later German Aircraft did. Wiki doesn't say, but frequently those things are not specified. Add in 150lbs of armor and a 200lbs for self sealing tanks and they nicely take the place of the weight you've allocated for a cooling system.

Sure, it would do that, but it would do the same thing to a Fw-190, which didn't have an engine coolant radiator.

The D-1, which was built in 1939, before the E-4 (1940) might well have lacked those things, but it's not clear one way or another.

I'm still in favor of either leaving it alone, or granting radials a deduction of 10lbs/L.

Hmm.. your point on the FW-190... how does that sim out? Does it come out overweight?

Here's a Fw-190 A-8. I''ve gotten the speed to be correct, the max weight and range are on, and in this version the light weight is also on. HOWEVER, to get that light weight to be correct, I've had to reduce the engine weight by 10%, and set the type to Conventional, vs rough field capable (which if you define rough field as grass, the 190 certainly was).

Aircraft Type or Name:

Focke Wulf Fw-190 A-8

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1939

Description

Conventional Aircraft
Monoplane
Conventional Fuselage

Mid-war version of the Fw-190, equipped with 2 13mm MG-131s in the nose, 4 20mm MG-151/20s in the wings, and approximately 150 kg of armor.



Characteristics:

Weight (maximum) 10,800 lbs
Weight (empty) 7,619 lbs

Length 29.5 ft
Wingspan 35 ft
Wing Area 197 sq ft
Sweep 0 degrees

Engines 1
BMW-801 D-2
Piston

1,835 hp
at 15,000 ft


Crew 1


Typical cost $0.041 million in 1943
Total number procured 2000


Performance:

Top Speed 346 kts = 398 mph
at 15,000 ft
Mach N/A

Operational Ceiling 30,000 ft

Range 500 nm = 576 miles
with 2,148 lbs payload
2,231 lbs released at halfway point

Climb 2,105 fpm

Cruise 260 kts = 299 mph
at 21,000 ft

Corner Speed 315 KIAS =
397 kts at 15,000 ft
Mach N/A
Turning Rate 17.0 deg/sec
Radius 4,511 ft



Internal Data:

Intake / Fan Diameter 12 ft

Bypass Ratio 95

Engine Weight 2078 lbs
Overall Efficiency 24.2 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 450 kts
Wing Ultimate g Load 10.00 g
Wing Taper 0.3
Wing Thickness at Root 1.2 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 9 ft
Diameter 3.25 ft
Fullness 0.5

Fuselage Diameter 4.25 ft
Fuselage Fullness 0.3

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 85 percent
Unstreamlined section 3 sq ft

User equipment 2,200 lbs

Quoted

Originally posted by Hrolf Hakonson
Here's a Fw-190 A-8. I''ve gotten the speed to be correct, the max weight and range are on, and in this version the light weight is also on. HOWEVER, to get that light weight to be correct, I've had to reduce the engine weight by 10%, and set the type to Conventional, vs rough field capable (which if you define rough field as grass, the 190 certainly was).

Interesting. It looks like your changes trimmed 232lbs from the engine and ~216 from the landing gear, for 448. The BMW 801 is a 41.8L engine. If a 10lb/L deduction was made to that instead of 10%, it would make up 90% of the difference.

Hmmmmm. That would work, yes. It could be that you're right, that the 5% "miscellaneous weight" included in the model is intended to cover cooling systems and because of that penalizes the aircooled engines. Giving aircooled engines a subtraction from their weight, while counter-intuitive, would probably work.