Blackburn Skua

[Pawel Burchard]

Tried to match plans published in mushroom book to Skua photograph and came up with something like this -

Any thoughts? Are there any other reasonable drawings of Skua out there?

p.

[davidelvy]

I would be very wary of suggesting that plans are wrong because they do not match a photograph. There are a number of stages in the protographic process at which distortions can occur. Such things as the angle between the subject and the lens (rarely an exact 90 degrees), the type of lens used, the printing process and, where the photograph is from a book or a web page, any distortions introduced deliberately in order to make a photo fit a page. When it comes down to it the only to check if a drawing is accurate is to take a tape measure to the real thing - but being careful not to wrap the tape around a curve. Of course, this is a bit of a non-starter with an aircraft such as the Skua, where the only examples of the real thing are twisted wreckage pulled out of watery graves.

This is a can of worms that gets opened periodically, so expect a few responses.

[grahamwalker]

Tried to match plans published in mushroom book to Skua photograph and came up with something like this -

Any thoughts? Are there any other reasonable drawings of Skua out there?

p.

Interesting but was the plane levels on all 3planes as which the camera would have to be matched to the said same planes?

well i know what i mean

graham IKBA wit Hons

[Edgar]

There is a certain French-Canadian, who makes a career out of insisting that you can check kit dimensions against photographs, and the method is more accurate than any commercially available plans. He's like one of those infuriating round-bottomed dolls, which, however many times you smack them down, keep bobbing up again.

There is another set of drawings, of the Roc & Skua, available from HPC Publishing, which originated in Alan Hall's Aviation News; his work is something of a curate's egg, and it really depends on who did the actual drawings, but it will probably be better than the "Marty Method."

Knowing the man behind the Mushroom series, he takes great pride in the efforts he makes in getting things right.

Edgar

Edited March 19, 2012 by Edgar

[JamesP]

Have you checked whether the plans or photo match the published length and span?

[CarLos]

Have you checked whether the plans or photo match the published length and span?

This would be my first step!

Plans are very often off scale - or worst: distorted in one dimension - and this sometimes escapes the publisher.

[Pawel Burchard]

Somewhat better quality -

this time I tried to match the wing... Assuming span is 14,1 m and length 10,8 m the plans in mushroom book are accurate.

Maybe there is indeed some deformation in photograph, although it does not look to be distorted.

p.

[Simon]

Have you checked whether the plans or photo match the published length and span?

Ratio of length to wingspan is 1:1.3056. Taking the image into Photoshop, the wingspan is about 222.6mm, so the fuselage should be around 170.5mm. The fuselage length on the drawing is about 171mm, and on the photo is about 176mm. Not scientific, but a good indication...

Simon

[mick b]

Knowing the man behind the Mushroom series, he takes great pride in the efforts he makes in getting things right.

Edgar

He managed to miss the rearward rake of the Skua undercarriage in his plans, despite photographs clearly showing the same in the book!

Mick

[Test Graham]

Putnam's Blackburn Aircraft since 1909 gives a span of 46ft 2 in and a length of 35ft 7in. The MM book says the same, so that gives us a scale span of 182.8mm and a scale length of 150.6mm, a ratio of 1.213. Which I think makes the point about distortions.

[Pawel Burchard]

Hello Graham Any 'primary' data concerning Skua dimensions we are aware of?

[Test Graham]

The Putnam book was written with access to Blackburn archives at HSA Brough - I think it will be as close to primary as you can find. Another source may be the Pilot's Notes, which I presume will be available. I don't have a set.

[Halibag]

The length quoted - is that tail-up, or tail-down? That can make a bit of a difference...

Dave

[Simon]

Putnam's Blackburn Aircraft since 1909 gives a span of 46ft 2 in and a length of 35ft 7in. The MM book says the same, so that gives us a scale span of 182.8mm and a scale length of 150.6mm, a ratio of 1.213. Which I think makes the point about distortions.

With apologies to Graham, and putting my pedantic hat firmly on , 46 ft 2 inches is 554 inches (46 x 12, + 2), or 14017.6 mm (1 inch = 25.4mm), and 35ft 7 inches is 427 inches (35 x 12, + 7), or 10845.8mm. That gives a ratio of 1.297, which is near as makes no difference the same as the ratio taken from the figures Pawel quoted in post number 7. 1/72 scale of that would be 195.4 mm and 150.6mm, not 182.8mm and 150.6mm.

Of course it's now very late and well past my bedtime, and I may be completely wrong so apologies all round if I am...

And as Dave (Halibag) says, it depends on how the figures given in the dimensions was measured.

Cheers

Simon

[Navy Bird]

I don't think the camera angle can make the fuselage appear to be longer (considering that the camera appears to be pretty much square on to the wings). If the tail were nearer or farther away from the camera than the wings, the fuselage length would be appear foreshortened.

If the wings were not level to the camera, for example, the port tip closer to the camera than the starboard tip, then the wingspan would appear foreshortened, and you could get a higher ratio of length to wingspan. But that sure doesn't look like the case in that photo. So the longer "looking" fuselage in the photo must be due to some other effect.

I think you should try and fit the fuselage length, and then see what the wings look like. Since the fuselage is longer, the fit should be better (the wings should be out by less than what the length was out originally). "Were there different marks of the Skua with different wings?" he asked sheepishly, as one with no knowledge of the aforementioned subject.

Cheers,

Bill

[davidelvy]

I think you should try and fit the fuselage length, and then see what the wings look like.

Cheers,

Bill

To be honest, I think it would be better simply to forget this exercise, unless the point is simply to satisfy curiosity. It involves measuring something which is suspected to be inaccurate against something which is likely to be distorted. The end result cannot reveal which is accurate - assuming that is the point of the exercise.

[Test Graham]

With apologies to Graham, and putting my pedantic hat firmly on , 46 ft 2 inches is 554 inches (46 x 12, + 2), or 14017.6 mm (1 inch = 25.4mm), and 35ft 7 inches is 427 inches (35 x 12, + 7), or 10845.8mm. That gives a ratio of 1.297, which is near as makes no difference the same as the ratio taken from the figures Pawel quoted in post number 7. 1/72 scale of that would be 195.4 mm and 150.6mm, not 182.8mm and 150.6mm.

Simon

No, you are spot on. My apologies for not checking my numbers more carefully. (Not an excuse, but that mistake wouldn't have been made with a slide-rule, rather than just believing whatever the computer told me! garbage in garbage out.)

I agree that distortion from the camera viewpoint would have given a shorter fuselage rather than a longer one, but that only suggests that the distortion was in the printing of the original or by the publisher.

The difference in length (nose-up or nose-level) would be only a few inches, and not relevant here (a few mm overall?). Given that the source appears to be Blackburn documentation, I would assume it was in-flight attitude that was quoted, as is usual. On the other hand, a carrier aircraft is perhaps the one example where the ground (or deck) attitude is important?

[Work In Progress]

I agree that distortion from the camera viewpoint would have given a shorter fuselage rather than a longer one, but that only suggests that the distortion was in the printing of the original or by the publisher.

Logical, however the roundels appear circular. Mind you, I have not put a ruler on them. Assuming the original poster has the best version of the pic, could he confirm the circularity of the roundels? Doing so would reveal any printing distortion, and further analysis of their shapes may reveal a bank angle, as may comparisons between the roundel sizes.

[seadog]

Bear in mind with older cameras using a focal plane curtain shutter, you can lengthen or shorten a moving object...as the exposure is made by a moving slit formed by the curtains - have a look at early shots of racing cars - eliptical wheels, due to a vertical shutter curtain....

F

[Pawel Burchard]

have a look at early shots of racing cars - eliptical wheels, due to a vertical shutter curtain....

Ok, but this Skua was, I presume, photographed from another aircraft flying approx. with the same speed.

I do not have a better copy of the photograph, I found it on the web.

p.

[Work In Progress]

Bear in mind with older cameras using a focal plane curtain shutter, you can lengthen or shorten a moving object...as the exposure is made by a moving slit formed by the curtains - have a look at early shots of racing cars - eliptical wheels, due to a vertical shutter curtain....

F

That's an interesting point, but I always thought the "leaning" wheels on Edwardian racing car pics were to do with the wheels actually rotating. I don't really know enough about it, but it's clear that there are a lot of potential complexities affecting photo interpretation, not just the usual arguments about colours.

[Pawel Burchard]

Another one

this time I multiplied length of the drawing by 103,5% - assuming the measurement 10,8 m was taken with tail down and the a/c axis is about 15 degrees to the ground.

p.

[John Aero]

I will come in here with a note of extreme caution. Go to a myriad number of books from Janes to the Boys book of Planes and you will find the length quoted for the Meteor NF 14 as 51'.4". Well my researches some time ago proved by accurately measuring 3 aircraft that the true length is in fact £49'.7" The same as it's predecessor the Mk 12. Also the DH (single seat) Hornet is quoted as either 30' or 37' and this can be found on DH drawings (one of which I have ) It's true length is 38' 4" (I used DH production drawings and I found that the AP(held at Rolls Royce) frontispiece is usually correct). So depending on what Blacburn drawings were used for the info the published data can be in error even from a manufacturer. Having said that, photo measuring is fraught with problems especially if the photo is in a book because printers are buggers for teasing stuff " to look right". So what is the true length of a Skua?

John

[John Aero]

The first prototype was originally 33' 2.5" long and later it was stretched to 35' 7" so depending on what figures were appended to drawings we have room for error from the start.

[Test Graham]

Yes John, that's what both the Putnams and the MM book say - is there any evidence that they are not right? Where did you get your statement from? Is it a different source, but are any of them independent?

It's common to point to errors in even official documents - IIRC the Defiant Mk.II manual doesn't allow for the extra length of the Merlin XX on overall length, which has misled at least one model manufacturer. Attention has to be paid to the issue number of manufacturer's GAs - have they really been modified correctly to allow for production changes? Often not - that's not what they were for. However, the majority of such statements are right, and unless good evidence does exist just being sceptical is unproductive. That two different lengths are quoted for prototype and production suggests that at least one obvious trap has been avoided.

re the latest Photoshop manipulation: it's a shame that wing tip and root chords are not one of the dimensions normally listed. I'm sure that many models could have avoided errors if they had been.