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Bilbo_Baggins

Spitfire clipped wings

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2 questions regarding this machine:

 

Is it faster in level speed and by how much?

 

How does the climb performance differ?

 

Thanks ūüėä

Edited by Bilbo_Baggins

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There's very little difference between the speeds at low alt, and at high alt the non clipped wing is an mph or two faster. I've not checked this in game though.

Climb rate I don't know.

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Frontal cross-section (and even wetted area) doesn't matter that much if you have huge draggy tip vortices?

Edited by Avimimus

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5 hours ago, Avimimus said:

Frontal cross-section (and even wetted area) doesn't matter that much if you have huge draggy tip vortices?

 

So what about P51 and Fockewulfe - high-speed machines for the era, yet with draggy tip vortices?

 

Regards

Edited by Bilbo_Baggins

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1 hour ago, Avimimus said:

Frontal cross-section (and even wetted area) doesn't matter that much if you have huge draggy tip vortices?

 

It matters. But in this case, it is not about the vortices. The wings were clipped to improve roll rate at high speeds, where control forces become problematic, especially when being confronted with the Fw190. So, as for clipped wings in 1943, think Fw190.

 

They traded roll rate for some slow speed turn. Pilots hated the machine¬†though, because the great turning abilities (when ¬†getting slow) could save them. Rolling scissors were obviously not an intuitive combat maneuver on the average.¬†In principle, the turning abilities shouldn‚Äėt have been too much affected, as the Mk.V LF had a higher boosted engine. At least at low level, where this type was very fast. But since at¬†least medium altitudes were mostly required during missions, pilots hated this plane¬†even more, as the smaller diameter, higher geared supercharger would drop off fast in performance.

 

In later Marks (IX, XII, XIV) the wings were clipped for increased roll and to keep wings skin from wrinkling. Those late Marks were fast enough for the pilot to induce excessive wing twist and flexing when really working the controls. Those Marks were also powerful enough to compensate for the increase in wing loading, hence there is mostly little difference in performance beyond facilitated roll. At very high altitudes, the clipped wings will be noticed though.

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3 hours ago, ZachariasX said:

 

It matters. But in this case, it is not about the vortices. The wings were clipped to improve roll rate at high speeds, where control forces become problematic, especially when being confronted with the Fw190. So, as for clipped wings in 1943, think Fw190.

 

They traded roll rate for some slow speed turn. Pilots hated the machine¬†though, because the great turning abilities (when ¬†getting slow) could save them. Rolling scissors were obviously not an intuitive combat maneuver on the average.¬†In principle, the turning abilities shouldn‚Äėt have been too much affected, as the Mk.V LF had a higher boosted engine. At least at low level, where this type was very fast. But since at¬†least medium altitudes were mostly required during missions, pilots hated this plane¬†even more, as the smaller diameter, higher geared supercharger would drop off fast in performance.

 

In later Marks (IX, XII, XIV) the wings were clipped for increased roll and to keep wings skin from wrinkling. Those late Marks were fast enough for the pilot to induce excessive wing twist and flexing when really working the controls. Those Marks were also powerful enough to compensate for the increase in wing loading, hence there is mostly little difference in performance beyond facilitated roll. At very high altitudes, the clipped wings will be noticed though.

 

So would you say it's basically the same in level speed and climbing performance at lower altitudes, just with the addition of a more responsive roll rate? 

 

I find this machine quite an interesting experiment in aerodynamics - such an iconic airframe, and clipped of it's wings just like that. 

Edited by Bilbo_Baggins

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iirc clipped wings also prolonged the life of the airframe for bomb carrying Spits. Reduced strain on the wings or somesuch

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11 minutes ago, Bilbo_Baggins said:

 

So would you say it's basically the same in level speed and climbing performance at lower altitudes, just with the addition of a more responsive roll rate? 

That's pretty much how I see it.

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From my tests back in 2018 when the mark IX came out, that is to say, before 150 octane.

Also, I am unsure about the IAS to TAS conversion I used. But the main take-away remains

 

 

(First row is full wings, second row is clipped wings;  full throttle and RPM)

 Deck 500m 1000m 1500m 2000m 2500m 3000m 3500m 4000m 5000m 6000m 7000m 8000m

   

 541 550 560 570 579 588 598 603 605 612 633 647 644
546 553 563 573 582 592 601 608 610 616 637 651 647

 

 

 

So, I have the clipped wings spit being marginally faster in level flight at all tested altitudes. Presumably, the full wings are better the higher up you go. So maybe the full-winged Mk.IX is faster at 10km. I was too lazy to check it

 

 

 

 

 

Edited by =FSB=HandyNasty
Edited for clarity's sake

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5 hours ago, Bilbo_Baggins said:

So what about P51 and Fockewulfe - high-speed machines for the era, yet with draggy tip vortices?

 

Induced drag only plays a major role at high CL/ low airspeed.

At low CL/ high airspeed, the tip-vortices are of minor importance.

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Plus the clipped wings looks much cooler? 

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24 minutes ago, Bremspropeller said:

 

Induced drag only plays a major role at high CL/ low airspeed.

At low CL/ high airspeed, the tip-vortices are of minor importance.

 


In laymen's terms, does that mean a squared wing tip like the P-51 and Fockewulf will be less efficient at low airspeeds, e.g turning performance/dogfights, but more efficient at maximum straight level speeds?

Edited by Bilbo_Baggins

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1 hour ago, Bilbo_Baggins said:

So would you say it's basically the same in level speed and climbing performance at lower altitudes, just with the addition of a more responsive roll rate? 

 

I find this machine quite an interesting experiment in aerodynamics - such an iconic airframe, and clipped of it's wings just like that. 

 

As @Bremspropeller says, induced drag is not that much different at higher speeds. In case of the Spit, she really has very big wings for going fast, but they also have a very thin profile. So the possible speed gains can only be modest and have never seen them specifically mentioned. They are only mentioned in context of the higer boost of the single stage Merlin the LF Mk.V Spit used.

 

What the wingtips do is produce a significant amout of lift at low speeds that was felt by the crews, hence she wasn't as good in low speed maneuvering. This is in fact an alteration that is ofen done. There are glider planes allow you to chane the outermost wing section and add another 2 meters or so. The performance is altered by such. You can see here:

 

pol_dg800-18.gif

There is a speed range, where 15 m wingspan is very near 18 m wingspan in performance. The gap opens up at slow speed as well as at higher weight.

 

I'm not so sure if the wingtip really reduced the vortex as a winglet would. Camm slightly clipped the Tempests eliptic wings as well. The Mustang doesnt have pointy wintips but it is a VERY fast airframe.

 

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30 minutes ago, ZachariasX said:

I'm not so sure if the wingtip really reduced the vortex as a winglet would.

 

Again, depends... :)

A less than optimal winglet might create a virtual wing-stretch (higher aspect-ratio) - depending on how well it is integrated into the 3d-flow of the entire wing.

A really cleverly designed winglet has a forward lift-component, creating "thrust", hence reducing drag on top of influencing the tip vortices.

 

Doesn't the DG-800 also have flaps? There is little gain between a 15m "Rennklasse" wing and an 18m bolt-on job onto that wing. The most decisive areas are at high CL (hence slow and/ or with high wing-loadings). Things only get really interesting beyond 20m wingspan on gliders - those tend fly like pigs, though.

 

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I seem to remember reading somewhere that the clip wing Spit variant accelerated faster, was quicker in a dive and the wing could withstand greater air speed.  Also, better visibility due to reduced wing area (I find this helps in IL-2 GB when hunting for contacts below and when flying in formation with other aircraft in my squad).

 

Happy landings,

 

56RAF_Talisman

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4 hours ago, Bremspropeller said:

Induced drag only plays a major role at high CL/ low airspeed.

At low CL/ high airspeed, the tip-vortices are of minor importance.

 

I guess a better way to express what I was getting at: The addition of the wingtips to produce the elliptical wing produces surprisingly little additional drag in spite of the increased surface area.

 

The exact contributions to this phenomenon (aspect-ratio, lift-distribution, spanwise flow, tip vortices) might be debatable... but I think it is still something worth remarking on!

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2 minutes ago, Avimimus said:

I guess a better way to express what I was getting at: The addition of the wingtips to produce the elliptical wing produces surprisingly little additional drag in spite of the increased surface area.

 

That's not how this was planned. The Spitfire is a plane of the old days that was supposed to fly of a patch of grass with a fixed pitch wooden propeller. To make the aircraft fast, this propeller is very coarse pitched, making it terribly inefficient at take off. Hence they required the Spit to come off the ground easily. You do this by giving it a very low wing loading.

 

The Spitfire in an incredibly handy plane for it's weight. So if you own a golf course, you're fine using it from there as well.

 

Mitchel now was confronted with the task of making a wing that is essentially too large at full speed: he made the profile as thin as possible and he chose the eliptical shape as this was known to have little induced drag. We're still talking about an 1'000 hp aircraft here that goes ~350 mph tops.

 

From here on, the engine got more powerful, the propellers vastly more efficient. Having more power enables you to increase wing loading without significant performance penatly. (Think Fw-190 here again.)

 

In reality, the surface of the Spit is far less than perfect, probably rendering theoretical truth like the eliptical outline being more efficiant as the tapered trapeziod shape irrelevant for practical purrposes. Several planes got their wing clipped as well, very prominantly the A6m3 Hamp (Zero). There, they omited the very corresponding part as was omited in the Spit. Also there, same as with the Spit, the lack of lift was noticeable. A "good" wingtip mediates considerable lift to the wing. For the Spitfire it was mainly noticed in slow turns, in case of the Zero it was an reduction of the planes mileage. It lost range, as it didn't fly as efficient anymore at lower ratings for cruise. But it gained in roll as well.

 

As soon as you are riding the low end of the lift polar, this becomes noticeable. It is there, where added induced drag hurt you, mainly becuase you're at a higher AoA due to less total lift.

 

Thus, the smaller wing is draggier, but only at slow speed. At full speed, the smaller wing is the better. That is why airliners have a wing that is as small as possible and rely on high lift devices for most flight configurations other than cruise.

 

It is doubtful that the elipitc wingtip is per se such a great thing in practise, as it hasn't really been used since then. All things fast didn't use it. The Temptest being an exception, as it had to have a sort of an eliptical wing because Sydney Camm was certain that the Air Ministry only bought planes with eliptical wings. But even then he shaved off part of that.

 

4 hours ago, Bremspropeller said:

Doesn't the DG-800 also have flaps? There is little gain between a 15m "Rennklasse" wing and an 18m bolt-on job onto that wing.

Agan, depends. If you fill her with water, the extra lift helps. And yes she has flaps. But the principle still applies, although at reduced rate.

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