# Spitfire does it have a single-spar wing



## thedab (Jul 22, 2013)

And does it make it a weak wing???


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## FLYBOYJ (Jul 22, 2013)

Went through this on an older thread. It has a single main spar but does have two spars in the wing.


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## Kryten (Jul 22, 2013)

thedab said:


> And does it make it a weak wing???



Weak compared to what?, for it's application the wing was strong and reliable enough to carry the aircrafts various marks without a major redesign, it carried less bomb weight than a hurricane but unclear if that's due to lift rather than strength?


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## fastmongrel (Jul 22, 2013)

Kryten said:


> Weak compared to what?, for it's application the wing was strong and reliable enough to carry the aircrafts various marks without a major redesign, it carried less bomb weight than a hurricane but unclear if that's due to lift rather than strength?



I remember reading somewhere that a clipped wing Spit could carry a heavier bomb load than a normal wing Spit, this seems counterintuitive to me surely a bigger wing means more useable lift.


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## Procrastintor (Jul 22, 2013)

Perhaps less drag, which allows for some added bomb weight. Just a guess though.


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## thedab (Jul 23, 2013)

Right this is from Flight fedruary 8, 1940

wing | main spar | construction note | 1940 | 0363 | Flight Archive

it say that the Spitfire had a single-spar wing

what make a single-spar wing??


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## riacrato (Jul 23, 2013)

Are you a troll trying to cause another flame war or am I just getting paranoid  ?

Anyway, I suggest you search for that other thread about this topic. Pretty much everything to be said was said there. To put it as neutral as possible: 

Group 1 will say: On a single spar wing, one spar (the _main spar_) and the leading edge form the (D-)box that bears most of the forces / loads acting on the wing. The wing can still have one or more_ secondary spars_, to hinge control surfaces to, but the load distribution makes it a _single spar_ wing. This point of view defines the Spitfire and Bf 109 as single spar designs and is the pov of your article's author.

Group A will say: Simply count the spars. By that definition the Spitfire has two spars and the Bf 109 has three, I think, but I'm not sure on the latter.


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## riacrato (Jul 23, 2013)

And now for my personal opinion:

Ask yourself, is a bicycle with training wheels a bicycle or is it a quadracycle?
*runs*


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## thedab (Jul 23, 2013)

Sorry all, I just found that old thread, the search is not working for me, so I had to go through aviation page by page.

so sorry about that.


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## fastmongrel (Jul 23, 2013)

thedab said:


> the search is not working for me, so I had to go through aviation page by page.



I often find its better to do a google search than use the search function


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## stona (Jul 23, 2013)

Beverley Shenstone described the Spitfire wing, in writing, as having a single spar (plus D box). That's good enough for me.

Cheers

Steve


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## thedab (Jul 23, 2013)

it look like that the undercarriage is mounted to the wing main spar.

how much force go through that spar on landing???


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## FLYBOYJ (Jul 23, 2013)

The wing has two spars. I don't care who says what, I don't care if you raise RJ Mitchel from the grave. It had TWO spars!


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## Aozora (Jul 23, 2013)

FLYBOYJ said:


> The wing has two spars. I don't care who says what, I don't care if you raise RJ Mitchel from the grave. It had TWO spars!



Looks like two spars to me...sparring partners? The main aerodynamic loadings were taken care of by the mainspar and leading edge box. From what I have read somewhere (wish I could remember where) the design of the undercarriage meant that the landing loads were distributed evenly along the centre-section of the spar, plus the design of the the spar meant that it was more than strong enough to take the loads; if anything, in a heavy landing the undercarriage pivot point was more likely to break than the spar was to even bend.


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## stona (Jul 23, 2013)

FLYBOYJ said:


> The wing has two spars. I don't care who says what, I don't care if you raise RJ Mitchel from the grave. It had TWO spars!



No point in arguing. I know what Shenstone wrote, I can reproduce it here when I get home in about 10 days time. I may well have quoted him in that old thread in any case. If the word of the man who designed the wing isn't good enough for you then nothing will be 

It seems obvious to me that he considered it a single spar design due to the vast majority of forces being borne by the main spar (and D box). I don't have figures available for that or what was borne by what you perceive as a second spar towards the back of the wing.

Cheers
Steve


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## cimmex (Jul 23, 2013)

FLYBOYJ said:


> The wing has two spars. I don't care who says what, I don't care if you raise RJ Mitchel from the grave. It had TWO spars!


Every aircraft engineer will call it a single spar design. Show me one plane with aileron and flaps without a rear spar to attach them. I don’t know any.
cimmex


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## stona (Jul 23, 2013)

cimmex said:


> Every aircraft engineer will call it a single spar design.
> cimmex



Indeed, the man who designed it did!

Cheers

Steve


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## razor1uk (Jul 23, 2013)

With regards the Spitfires, there is a slim rear spar for mounting the flaps and ailerons to, this (was then, and now still) is termed parasitic or auxillary spar because it is designed only to handle the loads from them; the flaps and ailerons to the wing structure itself. 

Where a spar handles a portion of those too loads along with the weight of the wing, its structural loadings, flight loadings and associated stresses and has attachment locations main fixings methods too, it is termed a 'Single Spar Wing' funnily enough.

Modern jets differ a lot from 40's props, even the teachers who teach the designers have changed along with systems, naming abbreviation methods etc, let alone 85+ years of technical development inbetween.
Spitting dummies out too early eh? wait a lil' longer 1st at least..


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## FLYBOYJ (Jul 23, 2013)

cimmex said:


> Every aircraft engineer will call it a single spar design. Show me one plane with aileron and flaps without a rear spar to attach them. I don’t know any.
> cimmex



And every mechanic or assembler will call it two spars based on the reasons you have given! This "singe spar" BS was a marketing tool. 

"SPAR - any of the main longitudinal members of the wing of an airplane that carry the ribs" 

One could come up with a ton of semantics, bottom line there's two spars in a Spitfire wing.


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## razor1uk (Jul 23, 2013)

Obviously your ignoring the point of why its called a single spar wing FBJ, fair enough then, talk only about your own countries aircraft then. It got feth all to do with marketing, and all to do with loadings and stresses, that's why.


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## FLYBOYJ (Jul 23, 2013)

razor1uk said:


> Obviously your ignoring the point of why its called a single spar wing FBJ, fair enough then, talk only about your own countries aircraft then. It got feth all to do with marketing, and all to do with loadings and stresses, that's why.



Put a hole in the "aft" spar of a spitfire wing and start pulling some Gs, see how long it stays together. It's a load carrying member. It doesn't matter if its a British, American, Russian or Martian aircraft, it has TWO (2) spars!!!


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## stona (Jul 23, 2013)

Here's a couple of pages of a report on the Spitfire wing from the Journal of Aeronautical History (from the Royal Aeronautical Society) which give a modern view of the structure.












They refer to the spar as the main spar which is self explanatory. Nobody has attempted to deny the existence of a secondary structure towards the rear of the wing to hang flaps etc on. Shenstone and Smith didn't refer to this as a spar at all and both repeatedly referred to the wing as "single spar". 

The structure of the wing was and is nonetheless a single spar design.

Cheers

Steve


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## FLYBOYJ (Jul 23, 2013)

"Single mainspar" And the "aft" thingy?!? IT'S A SPAR!!! Oh ok, let's call it "a secondary structure towards the rear of the wing to hang flaps etc on." 

Call it a "secondary spar," it's still a spar!

Again I repeat;

"SPAR - any of the main longitudinal members of the wing of an airplane that carry the ribs" 

If it looks like a duck, quacks like a duck......


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## Shortround6 (Jul 23, 2013)

cimmex said:


> Every aircraft engineer will call it a single spar design. Show me one plane with aileron and flaps without a rear spar to attach them. I don’t know any.
> cimmex



If you look you can find some planes with "false" spars, a structural member that ties a number of ribs together and provides an attachment for ailerons and flaps. However it does not attach to or carry though the fuselage ( and thus connect to each other) and in some cases there are TWO false spars that do not meet directly. One for the aileron and one for the flap. They may both attach to the same rib but at different points on the ribs length.


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## stona (Jul 23, 2013)

Well Flyboy let's just agree that you are right and Shenstone, Smith and the Royal Aeronautical Society as well as JAD Ackroyd CEng, FRAeS (who will almost certainly google nicely) are all wrong and leave it at that 

Cheers

Steve


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## FLYBOYJ (Jul 23, 2013)

stona said:


> Well Flyboy let's just agree that you are right and Shenstone, Smith and the Royal Aeronautical Society as well as JAD Ackroyd CEng, FRAeS (who will almost certainly google nicely) are all wrong and leave it at that


We'll do that. And I'll also bet I've repaired more SPARS then all of them put together!


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## razor1uk (Jul 23, 2013)

It could be worse, it could be connected with nautical terminology...

We/They I weren't disputing that FBJ, and nor what you have done too or what on the ground what the grunts/erks etc call things they work upon. 

A file is a file, either if it is a bastárd file or a roughing file, but they both do different jobs along similar lines - you wouldn't say that braizing, mig welding or tig welding are all the same would you or that a V6 is the same as a V8, V12 or a gas turbine?

Yes that wing does have two, but only one is the main, you could include the 'D' box leading edge as a possible third in that case, but still only one main fuz to wing that handles all the loadings.


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## stona (Jul 23, 2013)

I just found a note that Cole wrote that what we call today the secondary or auxiliary spar "mounts to the main spar". If this means it transfers some of its load to the main spar might this be why the designers and other Supermarine engineers in the 1930s considered the wing to be of a single spar construction? It also attaches to the fuselage but both the attachment and the element itself are extremely flimsy when compared to the main spar and it's attachments. The strength of the wing certainly does not come from the box formed by the skins between the main spar and this rear auxiliary.
Cheers
Steve


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## Kryten (Jul 23, 2013)

Hell guys , your arguing semantics, Flyboy is correct when he says it's twin spar when considered in the context of span wise load bearing members, it has two to carry separate loads, however if your referring to main load carrying structure then it can be considered as single spar, as in it has one main load carrying spar, lost in translation or what!


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## Aozora (Jul 23, 2013)

Shortround6 said:


> If you look you can find some planes with "false" spars, a structural member that ties a number of ribs together and provides an attachment for ailerons and flaps. However it does not attach to or carry though the fuselage ( and thus connect to each other) and in some cases there are TWO false spars that do not meet directly. One for the aileron and one for the flap. They may both attach to the same rib but at different points on the ribs length.



Them's what you call spar-ribs...great with barbeque sauce and hot fried potatoes Barbecue sauce spare ribs: Recipes: Good Food Channel


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## drgondog (Jul 24, 2013)

cimmex said:


> Every aircraft engineer will call it a single spar design. Show me one plane with aileron and flaps without a rear spar to attach them. I don’t know any.
> cimmex



You are playing with Semantics. I am an 'aircraft engineer', with focus on airframe structures and aerodynamics.

The 'structural item/spar/thingy' at the training edge with sustain lateral, torsion and bending loads. The latter places it in the category of 'spar' - you used the term yourself.

Whether someone wishes to say the Spit is a single Spar design only begs the question - define 'spar'.


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## stona (Jul 25, 2013)

drgondog said:


> Whether someone wishes to say the Spit is a single Spar design only begs the question - define 'spar'.



You are absolutely correct. All I can say is that Shenstone (and several other Supermarine employees including Mitchell himself, at least on one initialled document) did not consider the secondary/auxiliary/ rear spar, whatever we want to call it today, to be a spar by their contemporary definition. They all considered the wing to be a single spar construction. 

Modern engineers, as cited in the RAS paper, extracts of which I posted, seem to call this a "single main spar" construction which obviously indicates that they would call the secondary or rear spar a spar.
Times, definitions and usages change.

I also agree that we are arguing semantics. The structural strength and integrity of the Spitfire wing comes from that main spar and D box.

Cheers

Steve


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## FLYBOYJ (Jul 25, 2013)

"SPAR - any of the main longitudinal members of the wing of an airplane that carry the ribs" 






The single spar semantics IMO was just a marketing tool to make an aspect of the aircraft look better on paper. Call it a "main spar" or call the rear "thingy" a secondary spar, as Bill pointed out...

"The 'structural item/spar/thingy' at the training edge with sustain lateral, torsion and bending loads. The latter places it in the category of 'spar'


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## razor1uk (Jul 25, 2013)

Not another spin cycle please, I think we all agree it there is a spar at the rear of the wing yes!?; which in the posted design pic, that the rearwards one is not even 2/3's the structural thickness of the front one - some of the ribs where they attach to the front main spar, next to the gun mountings, are thicker than that rearwards located (secondary/parasitic) spar, or the offshoot from the the same main spar that travels rearwards along to the rear root-wing attachment point.

The apparent discussions are about the different semetnics the rear/auxillary/parasitic/secondary/trailing spar and how that is termed (by its usage), or by its apparent 'marketing appeal' or some such other modus operadai. 

Ok, should some persons locate post and discuss and compare that design to the design other WW2 era wings, what are the similarities between them and differences relating to the Spitfire design? or not?

While the description of a "SPAR - any of the main longitudinal members of the wing of an airplane that carry the ribs" is undoubtably correct, I can't help but feel its of a very simple explanation. Some like to stir the pot and watch where the bubble go it would appear - following post number 2.


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## Edgar Brooks (Jul 26, 2013)

Gentlemen, it might well be that, in aeronautical engineering terms, the Spitfire wing was referred to as a "single-spar design," but, in purely physical terms, it also contained two spars. The mainspar attached to frame 5, with 7 bolts, while the rear spar used a single bolt; however, before somebody says that it did nothing, at the end of the war, Park, in the Far East, was told not to use certain Mk.VIII XIVs, because their rear spar attachment points were faulty, and the wings could fail during heavy manoeuvring.
Drawings 30008 sheets 2509, 2425, 2427, 2428 show the construction, and assembly of the component parts of the "rear spar," which was attached to the wingribs, wingtip, and fuselage frame 10. These drawings, and their annotations, must have come from Shenstone and Mitchell.
There are general assembly drawings, which refer to a rear spar, and drawing 30027 sheet 12, for frame 10, also shows "rear spar attachment points," so all this argument would seem rather pointless.


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## Shortround6 (Jul 26, 2013)

People can go to the cut away drawing section of this web site and look at quite number of different wings. Some aircraft had a rather confusing array of "spars", granted in some cases these are artists interpretations of wing construction. But you can find some 'different' configurations. The P-47 used two 'main' spars and 3 auxiliary spars. One Auxiliary "spar" runs from rib #4 to rib #7 about 1/2 way between the front and rear main spars and helps take the landing loads and brace the wing for the landing gear cut outs. Another Auxiliary "spar" runs from rib #1 to rib #12 and supports the flap from rib #1 to rib #9. It doesn't appear to attach to the fuselage or carry through the fuselage. The last Auxiliary "spar" runs from rib #9 to rib # 19 (last rib) and supports the aileron. it runs behind the flap spar and meets the rear main spar about were the last rib is. While these auxiliary spars do stiffen the wing and resist bending of the wing panels themselves they do NOTHING to keep the wing from bending at the fuselage joint and transfer NO load to the fuselage structure.

The rear "thing-a-ma-bob" in a Spitfire wing does even if it is only a few percent of the total load.


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## OldSkeptic (Jul 28, 2013)

drgondog said:


> You are playing with Semantics. I am an 'aircraft engineer', with focus on airframe structures and aerodynamics.
> 
> The 'structural item/spar/thingy' at the training edge with sustain lateral, torsion and bending loads. The latter places it in the category of 'spar' - you used the term yourself.
> 
> Whether someone wishes to say the Spit is a single Spar design only begs the question - define 'spar'.



Well said. To prevent us all going through this one ... again...

How about we just say the "Spit had a primary front spar which carried all the major wing loads, with an secondary, non load bearing but stiffening, rear spar".

Or even "it had 1.5 spars" .............................


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## Gixxerman (Jul 28, 2013)

Main secondary spar seem fair descriptions to me, 2 spars or 1.5 if you like but not just 1.


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## fastmongrel (Aug 3, 2013)

2 nice pics of a Spit wing from -- Welcome to Avspecs Ltd -









I am saying nothing about how many spars I can see


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## OldSkeptic (Aug 4, 2013)

Nice pics. And a reminder that, th0ough everyone tends to concentrate on the aerodynamic designers of the Spit wing .... the structures people had to male it work and be strong and light enough to be functionlal.


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## gumbyk (Aug 4, 2013)

I was about to post those pics, fastmongrel.

I think what the real issue here is, is that what is termed 'single-spar' is a misnomer. A single spar wing is a theoretical construct (unless we're talking helicopter rotor blades). But, wings have been termed 'single spar' even if they have multiple spars, but most of the loads being transferred through one main spar.


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## razor1uk (Aug 4, 2013)

Indeed so guys.
The pictures that rear spare is slighter at a glance than in the draughted design pic, even wing root bracing and stiffening longerons from the main are more substantial structurally - hinting at the role the wing skins played in 'tieing' it all together. I can see why some earlier marks of wings could have some rearwards structural wing problems if used on later marks of engine fusalage.


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## nuuumannn (Aug 4, 2013)

Off topic I know, but that top picture shows the wing of Spitfire XIV NH799; it's a little further along since the pictures on Avspecs' website were taken, but, it'll be flying by early next year (fingers crossed).


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## fastmongrel (Aug 5, 2013)

nuuumannn said:


> Off topic I know, but that top picture shows the wing of Spitfire XIV NH799; it's a little further along since the pictures on Avspecs' website were taken, but, it'll be flying by early next year (fingers crossed).



Avspecs post some great photos on facebook I wish they would put more up though I suppose they are very busy. It would be a dream job to work there maybe one day if my numbers come up on the Lotto I could go over and help out (also known as getting in the way) even if it was just making the tea and sweeping up the workshop.


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