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Academy Su27 1/48 question


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Howdo all,

 

I posted the following over on Britmodeller so apologies if you've read this already. I didn't get a response so I've posted here in case someone new sees it and is able to help. Here goes (with slight editing of the original post)...

 

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Disclaimer: By asking this question I could be missing something obvious thus making a complete fool of myself. If so, please feel free to mock me, and apologies for the extreme nerdiness and seriousness (I'm usually not at all serious)  :bangin:

 

My first post so a quick intro. After many years I've come back to aircraft modelling where I scratchbuild in metal (not plastic) in quarter scale. To help with construction I pick up the most accurate kits I can find and use those as a base reference but then use billions of photo's and confirmed measurements to get to the end result.

 

I've been looking at my Academy Su-27 1/48 I bought about 20(?!) years ago. I had heard about the inaccuracy issues, in particular the length where it is said that the model's length included the pitot tube, when it shouldn't have, hence it appears short, i.e. 1/50 rather than 1/48, plus other issues. Here's my question...

 

I have been trying to find the primary source for the length and width of the Su-27, especially with or without the pitot tube. The earliest, and only, reference I've found to the 'length without air pressure receiver' is Andrei Fomin's early Polygon (1992) publication where he states "Длина без ПВД - 21.935(m)". All other 'main' publications I've managed to consult, mostly Russian, and including Fomin's later Airfleet book, have just given the length (21.935) although Moroz et al (2004) gives 21.835m which may be a typo'. There is no mention of 'length without pitot tube'. Width is given as 14.7m (without missiles attached) although Gordon gives the seemingly more accurate figure of 14.689m. I did check the multi-authored Истребитель Су-27. 'Начало истории' and 'Рождение легенды' (which appear to be the best books on the Su-27) and no dimensions are apparently given (although I may have miss something deep in the text, and my Russian is not fluent). There is a scaled factory drawing but... well, you know, ...it's a drawing. None give a primary 'from the horses mouth' reference for this info'. Is there irrefutable proof that the length (21.935m) of the Su-27 excludes the pitot tube?

 

The reason I ask is I checked photographs of Su-27 (and Su-30 - same length and width) in planform. My theory was that length divided by width will give me a ratio that can be used to determine if the length given includes the pitot tube or not. The ratio of published measurements is 1:1.492 (21.935m/14.698m, assuming these measurements are correct). The photo's I found were far and few on the interweb thingy but I did manage to find a few Su-27's and Su-30's to check (please note I don't have the links as I wasn't expecting to find anything but these can be refound if required). This was done in Photoshop using the 'ruler' to measure from the outermost part of the wing (without missiles) and from the tip of the tail boom to the tip of the cone and again to the pitot tube. I only chose photo's that were as close to planform as possible, of sufficient resolution, and were apparently free of distortion. The margin of error is difficult to determine but needs to be borne in mind.

 

I found 6 images and the results were...

 

Width to Length (tail boom to nose cone tip): 1) 1.437  2) 1.449  3) 1.455  4) 1.442  5) 1.432  6) 1.472

Width to Length (tail boom to pitot tube tip): 1) 1.493  2) 1.496  3) 1.506  4) 1.487  5) 1.489  6) 1.525

 

The difference between these ratios in length is about 70cm (the length of a pitot tube?) on the real aircraft so quite significant. What is interesting is the consistency of images 1 to 5 and how close the W/L ratio is to that of W/L ratio of published measurements, 1.492. Number 6 is a little bit off either way it seems but not sure why. Obviously more images need to be checked to see if this was a pure fluke or not and ideally someone with a tape measure on the real thing. Maybe others here who have their own Su-27 images in planform can check?

 

Before taking this further (it has ramifications on the Academy kit build in ways not considered before), am I talking rubbish or is there some merit to the above? That's if that irrefutable proof isn't presented of course. :unsure:

 

Cheers,

Feisty

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i think you'd wasted your time on that flat earth theory.

sorry if i didn't give you "the absolute proof"  that Academy had "pooched" their kit in a fashion the real Sukhoi Flanker didn't.

but, after seeing how Hobby Boss, Kinetic and GWH have achieve model kits that manage to match "factory" drawings outlines on most elements...  (photos will nearly always suffers from some parallax effect)

and that when you compare all those kits, it is Obvious that the academy kit is wrong. (the geometry of the tails shows)

 

for me, the only cure for the academy flanker misshape is to look at it from some 3/4 angle, or something like that... 

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21 hours ago, mingwin said:

i think you'd wasted your time on that flat earth theory... [clip ]  ...for me, the only cure for the academy flanker misshape is to look at it from some 3/4 angle, or something like that... 

 

Thanks for the reply. I understand where you're coming from. However, I always like to find out and prove things for myself which includes comparing the model (or its parts) to a myriad of photos. I also realise I am questioning the gospel but the gospel is not necessarily the truth. I found a discrepancy that's apparently too consistent so I have to question the gospel.

 

The thing about drawings is that they're not based on bona fide factory drawings. The 'third party' drawings vary in quality and accuracy and I know of no drawing that is 100% accurate. In parts, yes, but not as a whole. Presumably drawings are based on photographs and actual measurements of the aircraft where the latter is allowed. They are susceptible to human error. I always use as many photos as possible to gauge accuracy, and with regards to proportion, etc. only those photos taken with a lens that does not distort the image, i.e., a standard or telephoto lens. For a model manufacturer to base a model on a drawing (often the case in the early days) is increasing the risk of error, hence such errors in models are not uncommon, although errors occur for other reasons too of course.

 

Compared with photographs, the Academy kit is wrong in several respects, not least the tail plane shape (you don't need a drawing to see that; it's evident from photos). Other errors included the cockpit shape and size, and its placement (appears too far back), latitudinal cross-section of the canopy, the length of the airbrake, the slope from the wing to body (too deep) and a few other things. However, some aspects that were considered wrong aren't so much - this includes the nose cone that only appears slightly too thick (by about 0.5mm or so, and can be sanded to shape) when compared with photo's, otherwise it looks spot on. When I compare the Academy kit to various planform photo's, taking the rear end as the baseline, then the kit turns out to be quite accurate in overall dimensions expect that it has been foreshortened in the mid-fuselage area, and the body needs to be brought forward in that are by a few milimetres (hence the short airbrake, etc.?) along with the forewing needing to be being brought forward where it connects to the fuselage, swiveling on the outer end of the leading edge flap (nose-cone is of the correct length!). All errors prove consistent when referenced to a variety of suitable photographs.

 

Agree about the parallax which is why I chose photos of aircraft that were as close as possible or perfectly in planform. Any deviation by as much as a few degrees (which would be fairly obvious in the photos) only equates to a few inches and not enough to create a significant enough standard deviation to account for the difference in ratio I'm finding, and that can be proven by experiment and simple geometry. An example of the type of photo I used is here... https://c1.staticflickr.com/5/4296/35567143920_00365cc8b0_k.jpg. I have since found a few more photos in planform and the ratio mentioned in my opening post is still consistent.

 

This wouldn't be so bad if was some scientific endeavour but as it's 'just' modelling I'm acutely aware that I'm being very, very nerdy. :rolleyes:  😉

 

FM

 

PS. I do hope there is a prize for the nerdiest thread of the year 😀

Edited by Feisty Midget
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there was some drawings of the Su-35 on the Sukhoi Bureau website a while ago. (maybe KNAAPO website)

i have a few of them somewhere somewhere in my computer. and i remember having seen comparisons on the web. 

 

sometime, in the end, you have to rely on experts...  unless you go somewhere they have the real aircraft and take some measurements.

 

you're maybe just a few years late( i'd say 8 or 10), on that very subject, to have the "proper" expected answer to your quest... from this board. 

it's not like if it wasn't an interesting subject... i have 8 academy flanker in my stash... all slightly started to various stages (and some under broader surgery for the Sol conversion sets)...but also the "others"...from HB, KH, Kinetic, and GWH...

 

i've also spent countless hours looking at photos...to end up to the same conclusion as most experts said.

(and this, is without pointing the 1/72 Svezda Su-27SM kit... which is made in Russia, where designer where  granted access to the "real thing"... and their kit also has the same "good" outlines shape proportions...)

 

maybe you'll prove me wrong, but, till then, i'll still believe the earth is round...

 

 

 

 

Edited by mingwin
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