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

[ShadowFrost]

41 minutes ago, =475FG= Dawger said:

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.

I don't have any wind tunnel testing on the P-51, correct. I do however have seen substantial wind tunnel testing on race cars, and even we do similar. A certain series removes the roof on their cars to increase drag to make the show better. I have never seen an example of a windshield (only) performing better than a fully enclosed canopy/roof or similar design in regards to drag. 

If you wish to redefine your argument as "we don't know how badly the canopy being missing would effect top speed performance" that is far more reasonable. However, you said "...We cannot know if the total drag is higher, lower or equal without actual flight or wind tunnel ( real or sophisticated computer modeling) testing." and "Is drag different after opening or ejecting the canopy? Yes. Is it more or less drag? Unknown as is the degree of change." which indicates you believe it could be either which is incorrect. 

It will most certainly add drag, how much specifically, will require data. 

Edited February 9, 2023 by ShadowFrost

[Machalot]

3 hours ago, =475FG= Dawger said:

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.

Not because it looks true. It's very well established in the field of aerodynamics that bluff bodies with aft flow separation have higher drag than streamlined bodies. You can find this in many textbooks and published papers. While I agree we don't have quantitative data specific to the P-51 canopy, but I'm surprised you would call this an unproven theory. 

[=475FG= Dawger]

7 hours ago, Machalot said:

Not because it looks true. It's very well established in the field of aerodynamics that bluff bodies with aft flow separation have higher drag than streamlined bodies. You can find this in many textbooks and published papers. While I agree we don't have quantitative data specific to the P-51 canopy, but I'm surprised you would call this an unproven theory. 

The assertion was  "A windshield alone, absolutely produces more drag than a bubble canopy." not bluff body versus streamlined.

 

[peachmonkey]

13 hours ago, ShadowFrost said:

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." 

at this point I'm not even sure what you're trying to get out of this discussion. Dawger is taking a scientific and empirical position. You Others seem to simply rely on the visuals, and of an automobile out of all things, that doesn't have that ginormous windmill in front of it. Point is there's always some drag. Arguing that the cockpit cover produces less drag vs no cover at this point is purely speculative because you don't have the data for either of the cases. What now?

edit:  from my lament's point of view watching MythBusters continuously kept proving that the intuition != reality 

Edited February 9, 2023 by peachmonkey

[Machalot]

2 hours ago, =475FG= Dawger said:

The assertion was  "A windshield alone, absolutely produces more drag than a bubble canopy." not bluff body versus streamlined.

 

Why don't you think that applies? 

[Magic Zach]

On 2/5/2023 at 8:16 PM, =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. 

And it is at this point that I cannot take anything you have to say seriously anymore.  You're saying that because bubble canopies increased drag vs the razorback/birdcage canopies (correct), therefore removing the canopy entirely will remove drag?  I'mma be straight with you, this makes it sounds like you have never stuck your hand out the window of a moving car before.  Because canopy type B has more drag than type A, does not mean that severely "modifying (ejecting canopy)" of type B will suddenly remove the drag.  That is not at all how aerodynamics work

On 2/8/2023 at 11:20 AM, =475FG= Dawger said:

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. 

We can, with reasonable assumptions, predict which directions some effects will go.  What you're implying (cannot tell if drag will change at all without breaking out the NACA windtunnel) is akin to suggesting that we cannot know if a rock will fall if it is let go 

Edited February 10, 2023 by Magic Zach
politeness

[=475FG= Dawger]

On 2/9/2023 at 7:34 AM, peachmonkey said:

at this point I'm not even sure what you're trying to get out of this discussion. Dawger is taking a scientific and empirical position. You Others seem to simply rely on the visuals, and of an automobile out of all things, that doesn't have that ginormous windmill in front of it. Point is there's always some drag. Arguing that the cockpit cover produces less drag vs no cover at this point is purely speculative because you don't have the data for either of the cases. What now?

edit:  from my lament's point of view watching MythBusters continuously kept proving that the intuition != reality 

 

Thanks for summarizing my point. However, I don't think its going to have any effect, as subsequent posts eloquently demonstrate.

[NineLine]

I'll take a look and ask the team.