Spitfire clipped wings

[Bilbo_Baggins]

2 questions regarding this machine:

 

Is it faster in level speed and by how much?

 

How does the climb performance differ?

 

Thanks ?

Edited February 20, 2020 by Bilbo_Baggins

[Barnacles]

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.

[Avimimus]

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

Edited February 20, 2020 by Avimimus

[Bilbo_Baggins]

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 February 20, 2020 by Bilbo_Baggins

[ZachariasX]

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‘t 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.

[Bilbo_Baggins]

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‘t 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 February 20, 2020 by Bilbo_Baggins

[=621=Samikatz]

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

[Barnacles]

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.

[HandyNasty]

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 February 20, 2020 by =FSB=HandyNasty
Edited for clarity's sake

[Bremspropeller]

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.

[Diggun]

Plus the clipped wings looks much cooler? 

[Bilbo_Baggins]

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 February 20, 2020 by Bilbo_Baggins

[Bremspropeller]

Depends...

[ZachariasX]

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:

 

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.

 

[Bremspropeller]

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.

 

[Talisman]

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

[Elem]

https://www.quora.com/Why-did-some-Spitfires-have-clipped-wings-in-WW2

[Avimimus]

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!

[ZachariasX]

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.

[=RS=Stix_09]

Reviving this couple month old thread I have a question.

 

Question how does this relate to in game performance vs a real case study?

(in relative terms as test that follows was done on 2 identical modified  MkVB, both tested with and without clipped wings (Merlin 45M dif to what we have in game, with  similar  horsepower to the MkIXe in game ) do results follow these same lines..) 

 

Quote

This removed something in the region of 4 feet from the wingspan of a normal-span Spitfire, improving its roll moment (one area where the Fw190 completely outperformed it) considerably and increasing its speed at low level. Additionally, the implementation of the Merlin 45M with smaller supercharger cropper blades at the impeller yielded 1,585hp @ 2,750ft and +18lbs of boost, increasing initial rate of climb to 4,720ft per minute @ 2,000ft.

Climb

The average difference in time during zoom climbs from 20,000 to 25,000ft was 15 seconds in favour of the standard Spitfire.

From 10,000ft to 15,000ft no differences were indicated.

 

 

 

Details of the test done follows with ref link: (Test trials and comparisons actually done, between clipped and non clipped wings on Mk VB's)

Spoiler

Quote

https://www.quora.com/Why-did-some-Spitfires-have-clipped-wings-in-WW2?share=1

Air Fighting Development Unit at Duxford

Clipped-wing (32ft 6ins) Spitfire versus standard wing (36ft 10ins) Spitfire

The following information comes from flight trial held late in 1942.

Method of test

Two Spitfire Mk Vb aircraft were selected with as near-identical performance as could be managed, the loading and equipment carried were standard in each and the propeller, engine and finish of each aircraft were similar.

A test flight was made under maximum cruising conditions and no differences could be determined. The wing tips were then removed from one aircraft and trials were carried out, each trial being performed twice to enable the pilots to be changed. The wing tips were then replaced and removed on the other aircraft and the tests repeated.

Differences in speed were taken as relative increases or decreases owing to possible instrument inaccuracies, and position error differences with and without tips.

Readings for level speeds were taken at 10,000, 15,000, 20,000 and 25,000ft, zoom climbs were made 10,000 - 15,000ft and 20,000 - 25,000ft and dives were made with similar engine settings.

 

Results of Comparative Tests

Level Speed

• 10,000ft: In each case the clipped-wing Spitfire proved the faster by a small margin of about 5 mph.
• 15,000 and 20,000ft: The average results at these two heights showed that the difference in speed is not measurable.
• 25,000ft: The standard Spitfire is very slightly faster than the clipped-wing Spitfire.

In all level speed runs the clipped-wing Spitfire accelerated faster than the standard Spitfire.

Climb

The average difference in time during zoom climbs from 20,000 to 25,000ft was 15 seconds in favour of the standard Spitfire.

From 10,000ft to 15,000ft no differences were indicated.

Dive

In all diving tests the clipped-wing Spitfire drew away from the standard Spitfire.

Manoeuverability

At all heights to 25,000ft the rate of roll is considered improved by the removal of the wing tips.

Roll rate for a standard Spitfire was 105 degrees per second at 200mph. This was increased for the clipped-wing version to 175 degrees per second at the same speed. It should be noted that the clipped-wing version suffered the same difficulties in the rolling plane as the standard fighter as the speed of the aircraft increased.

The response to aileron movements is very quick and very crisp. Four dogfights were carried out, starting with the standard Spitfire on the tail of the clipped-wing Spitfire. On two occasions the clipped-wing Spitfire evaded so rapidly in the rolling plane that it was able to lose the standard Spitfire and reverse the positions in about 20 seconds. On the third occasion the clipped-wing Spitfire was also able to lose the standard Spitfire. The fourth occasion was at 25,000ft and the standard Spitfire was able to keep the clipped-wing Spitfire in sight.

The minimum turning circle of the clipped-wing Spitfire at 20,000ft has been increased by 55ft at 1,025ft compared with the Fw190 turning circle of 1,450ft (RAE Farnborough figures). This slight increase does not therefore detract from the fighting qualities of the aeroplane in any way, since the clipped-wing version is unlikely to be in combat with the standard Spitfire.

Take-off

No difference was detected.

Landing

No difference was detected.

General

The view downwards over the reduced wing tips is improved considerably. The strengthening of the wing by removal of the wing tips may permit higher maximum IAS to be used.

 

 

Also

Concise Guide To Spitfire Wing Types

http://spitfiresite.com/2010/04/concise-guide-to-spitfire-wing-types.html

Edited May 29, 2020 by =RS=Stix_09