Little (Or Possibly No) Drag from Open Canopy In-Flight

[Magic Zach]

When opening the canopy, it has little or perhaps no additional drag.  So players might as well fly around with their canopy always open if it never slows them down.
Test is performed by flying at mil power at SL with canopy closed for a couple minutes.  Then pull a loop, open the canopy, and continue flying at power at SL.  Test also contains the Spitfire, FW190A, and P-47.

canopy drag test.trk

[kablamoman]

This should be high on the priority list as it's a pretty glaring oversight related to the flight modeling.

[grafspee]

Do anyone has speed trials with canopy open/close ?

[=475FG= Dawger]

Its probably faster with the bubble canopy open. 

[grafspee]

9 hours ago, =475FG= Dawger said:

Its probably faster with the bubble canopy open. 

Rather obvious, but how much?

[=475FG= Dawger]

10 hours ago, grafspee said:

Rather obvious, but how much?

I don't think the OP thinks its obvious. He seems to think there should be a huge drag penalty with the canopy open.

But there will be no official data.

 

[grafspee]

10 minutes ago, =475FG= Dawger said:

I don't think the OP thinks its obvious. He seems to think there should be a huge drag penalty with the canopy open.

But there will be no official data.

 

So only thing left is CFD done by ED to determine exact numbers then.

My guts were telling me the same thing, that high speed tests with canopy open/close does not exist, and at slow speed, like landings or takes off makes no difference.

Edited January 19, 2023 by grafspee

[Magic Zach]

On 1/20/2023 at 7:25 AM, grafspee said:

So only thing left is CFD done by ED to determine exact numbers then.

My guts were telling me the same thing, that high speed tests with canopy open/close does not exist, and at slow speed, like landings or takes off makes no difference.

 

Yeah during low speed, it wouldn't have much of an impact on drag.  However at high speeds, if the canopy were suddenly open it should have a rather notable impact on drag and affect your overall speed

[=475FG= Dawger]

17 hours ago, Magic Zach said:

Yeah during low speed, it wouldn't have much of an impact on drag.  However at high speeds, if the canopy were suddenly open it should have a rather notable impact on drag and affect your overall speed

Where is your data on that?

It is likely a lot less impact on speed than you think.

Bubble canopies produce drag themselves, especially at speed.

The result of removing it might be very close to zero.

And there is no data.

We do know the birdcage canopy is faster than the bubble, contrary to what might appear logical visually,  so the assumption that this can be inferred accurately is false.

[grafspee]

No data available but at least in p51 case canopy when opened is elevated up, so it is obvious that drag will be higher.

Another case would be when canopy is jettisoned.

[Magic Zach]

16 hours ago, =475FG= Dawger said:

Where is your data on that?

It is likely a lot less impact on speed than you think.

Bubble canopies produce drag themselves, especially at speed.

The result of removing it might be very close to zero.

And there is no data.

We do know the birdcage canopy is faster than the bubble, contrary to what might appear logical visually,  so the assumption that this can be inferred accurately is false.

We do know that when pilots would pop off or open their canopy at high speed, they were pushed down pretty incredibly into their seat.  So this does already tell us that there was a pretty significant redirection of air with bubble canopies open.  This would incur more drag.

[=475FG= Dawger]

21 hours ago, grafspee said:

No data available but at least in p51 case canopy when opened is elevated up, so it is obvious that drag will be higher.

Another case would be when canopy is jettisoned.

 

6 hours ago, Magic Zach said:

We do know that when pilots would pop off or open their canopy at high speed, they were pushed down pretty incredibly into their seat.  So this does already tell us that there was a pretty significant redirection of air with bubble canopies open.  This would incur more drag.

These are both assumptions that the change in drag post canopy opening results in an increase in drag. This may or may not be true and the magnitude of any change is not knowable without actual flight testing or some very sophisticated computer modeling.

Is drag different after opening or ejecting the canopy? Yes. Is it more or less drag? Unknown as is the degree of change.

[Magic Zach]

Are you honestly suggesting that opening or ejecting the canopy would decrease drag?  Are you actually backing that?

On 2/1/2023 at 7:58 PM, =475FG= Dawger said:

 

These are both assumptions that the change in drag post canopy opening results in an increase in drag. This may or may not be true and the magnitude of any change is not knowable without actual flight testing or some very sophisticated computer modeling.

Is drag different after opening or ejecting the canopy? Yes. Is it more or less drag? Unknown as is the degree of change.

 

[grafspee]

@Magic Zach I think he is saying that there is equal chance that drag will decrease, increase or stay the same. 

[=475FG= Dawger]

4 hours ago, Magic Zach said:

Are you honestly suggesting that opening or ejecting the canopy would decrease drag?  Are you actually backing that?

 

Yes, I am suggesting that it is possible. Bubble canopies are proven to increase total drag when compared to other canopy installations. Removing a bubble canopy removes X amount of drag and this value may be greater than the amount Y of drag added by not having any canopy. 

Grafspee has it correct. We cannot know if the total drag is higher, lower or equal without actual flight or wind tunnel ( real or sophisticated computer modeling) testing.

[Hobel]

  

this is not about whether the Bubble canopies of the P51 is worse than others, but whether the P51 slows down when the canopie is dropped and I would simply say yes without hard data.

 

 

 

 

With and without a canopie x) :

 

 

 

Edited February 5, 2023 by Hobel

[ShadowFrost]

20 hours ago, =475FG= Dawger said:

Yes, I am suggesting that it is possible. Bubble canopies are proven to increase total drag when compared to other canopy installations. Removing a bubble canopy removes X amount of drag and this value may be greater than the amount Y of drag added by not having any canopy. 

Grafspee has it correct. We cannot know if the total drag is higher, lower or equal without actual flight or wind tunnel ( real or sophisticated computer modeling) testing.

I disagree, a bubble canopy adding more drag is in reference to an "inline" canopy or other design, not to no canopy at all. A windshield with its edge exposed will create turbulence and increase drag compared to a full bubble or other design. Removing the bubble canopy would only further increase the drag, not decrease it. 

Given that it goes against the conventional understanding of aerodynamics, I would say the burden of proof is on you to say that no canopy reduces drag compared to having a canopy. 

Overwhelmingly, a partial windshield or open canopy will be more draggy than a fully enclosed canopy. However, of the fully enclosed canopies and fuselages, there are designs between the two that have better performance at the cost of visibility.

Now, canopies do add drag overall to the aircraft, but you must have them. An aircraft with only a fuselage (no exposed pilot or canopy) would be much more clean of a design aerodynamically than any of the relevant canopy designs for WW2 aircraft. The bubble canopy adds drag in comparison to the earlier P-51A/B canopy. If either design were open or missing it's canopy, it would add drag and be extremely uncomfortable for the pilot at higher speeds.  

Edited February 6, 2023 by ShadowFrost
Clarity

[=475FG= Dawger]

On 2/6/2023 at 12:17 AM, ShadowFrost said:

I disagree, a bubble canopy adding more drag is in reference to an "inline" canopy or other design, not to no canopy at all. A windshield with its edge exposed will create turbulence and increase drag compared to a full bubble or other design. Removing the bubble canopy would only further increase the drag, not decrease it. 

Given that it goes against the conventional understanding of aerodynamics, I would say the burden of proof is on you to say that no canopy reduces drag compared to having a canopy. 

Overwhelmingly, a partial windshield or open canopy will be more draggy than a fully enclosed canopy. However, of the fully enclosed canopies and fuselages, there are designs between the two that have better performance at the cost of visibility.

Now, canopies do add drag overall to the aircraft, but you must have them. An aircraft with only a fuselage (no exposed pilot or canopy) would be much more clean of a design aerodynamically than any of the relevant canopy designs for WW2 aircraft. The bubble canopy adds drag in comparison to the earlier P-51A/B canopy. If either design were open or missing it's canopy, it would add drag and be extremely uncomfortable for the pilot at higher speeds.  

 

That’s a lot of talking to get nowhere. There is no data on the drag differences between no canopy and canopy closed. Assuming there is a huge drag penalty based on looks is not valid. In the absence of data, the flight model should be left alone. 

[Machalot]

My car tells me to close my windows to reduce drag if I go fast with them open. I presume there's some data behind that. 

[Hobel]

vor 6 Stunden schrieb =475FG= Dawger:

That’s a lot of talking to get nowhere. There is no data on the drag differences between no canopy and canopy closed. Assuming there is a huge drag penalty based on looks is not valid. In the absence of data, the flight model should be left alone. 

Did you see the video I posted, is it so unlikely that something similar happens with the p51?

[=475FG= Dawger]

2 hours ago, Hobel said:

Did you see the video I posted, is it so unlikely that something similar happens with the p51?

Again, a visual of wind tunnel testing of a car does not produce data. It produces a “feeling”, a guess, a presumption. 
 

Bubble canopies are well known to produce more drag than their more streamlined counterparts. They are an aerodynamic concession to improve pilot visibility and freedom of movement. This increased drag isn’t all from parasitic drag. The exaggerated curved shape of a bubble canopy itself produces induced drag. 

So using a streamlined canopy as a control, both the bubble canopy and no canopy produce more drag. How much more for each? We have some data for the bubble canopy in the form of loss of top speed, although this data isn’t perfect in the case of the P-51. We have no data for canopy removed flight.

How do you propose to quantify an unknown and unknowable quantity of drag change between two untested cases? 

 

Edited February 8, 2023 by =475FG= Dawger

[ShadowFrost]

9 hours ago, =475FG= Dawger said:

Again, a visual of wind tunnel testing of a car does not produce data. It produces a “feeling”, a guess, a presumption. 
 

Bubble canopies are well known to produce more drag than their more streamlined counterparts. They are an aerodynamic concession to improve pilot visibility and freedom of movement. This increased drag isn’t all from parasitic drag. The exaggerated curved shape of a bubble canopy itself produces induced drag. 

So using a streamlined canopy as a control, both the bubble canopy and no canopy produce more drag. How much more for each? We have some data for the bubble canopy in the form of loss of top speed, although this data isn’t perfect in the case of the P-51. We have no data for canopy removed flight.

How do you propose to quantify an unknown and unknowable quantity of drag change between two untested cases? 

 

 

A windshield alone, absolutely produces more drag than a bubble canopy. A bubble canopy reduces drag compared to a windshield only, however, a more streamlined concept further reduces drag than both the bubble canopy and windshield only. 

And yes, the turbulence in the video is important aerodynamically. It shows you the disruption of airflow compared to with the roof on which in turn is increasing drag. Why would this not happen for the P-51 if you removed the canopy? Why is the P-51 special? 
 

[peachmonkey]

1 hour ago, ShadowFrost said:

It shows you the disruption of airflow compared to with the roof on which in turn is increasing drag. Why would this not happen for the P-51 if you removed the canopy? Why is the P-51 special? 

nobody's saying that, I think. The question is how much drag it actually induces and what are its effects on the top speed. Yes, it adds drag. Now what?

[=475FG= Dawger]

4 hours ago, ShadowFrost said:

A windshield alone, absolutely produces more drag than a bubble canopy. A bubble canopy reduces drag compared to a windshield only, however, a more streamlined concept further reduces drag than both the bubble canopy and windshield only. 


 

How do you know this? Where is your testing of this theory that proves this assertion?

Which is the entire point. There is no data. No one actually knows. They are just making the assumption because it "looks" true.

[ShadowFrost]

2 hours ago, peachmonkey said:

nobody's saying that, I think. The question is how much drag it actually induces and what are its effects on the top speed. Yes, it adds drag. Now what?

Actually, Dawger suggested both. "...We cannot know if the total drag is higher, lower or equal without actual flight or wind tunnel ( real or sophisticated computer modeling) testing."