Amodel 1/72 Yak-9U

[John Thompson]

Here's an interesting article from Scalemodels.ru about building the Amodel 1/72 Yak-9U; apparently the wing needs to be moved back toward the tail by about 3 mm:
http://scalemodels.ru/modules/forum/viewtopic_t_20289.html

It's too bad Moskit stopped production before the replacement exhausts for this kit were completed; the kit exhausts are not very well detailed.

John

[John Thompson]

Hmmm - as it happened, I had an Amodel Yak-9U at exactly the right stage of assembly (fuselage halves glued together; upper and lower surfaces of the wings glued together but still separate from the fuselage) to test this out. As can be seen from the images in the Scalemodels.ru thread, moving the wings back 2 or 3 mm leaves a nasty-looking, crescent-shaped gap which has to be filled without eliminating the panel line between the fuselage sides and the wing roots. The person building the model seems to have done a very neat job of it, but it does look challenging - I might try multiple narrow strips of thin plastic sheet. Also note that he extended the wing root intakes forward to correct their shape and length.

John

[Massimo Tessitori]

I'm worried:I've the Yak-9U, Yak-9P and Yak-3VK-107, I suppose that the same thing is valid for all three types. My worry is for the panelling, in particular. Is the thing visible on photos, in your opinion?
Massimo

[John Thompson]

I'm worried:I've the Yak-9U, Yak-9P and Yak-3VK-107, I suppose that the same thing is valid for all three types. My worry is for the panelling, in particular. Is the thing visible on photos, in your opinion?
Massimo

I'm working on it - part of the problem is finding a good clear side-view photo of the Yak-9U or Yak-9P which has visible reference points on it, so I can scale this to 1/72. I think I have one from Stapfer's "Yak Fighters In Action" book but I'll need some "alone time" at the photocopier to resize this photo. That might not happen until Saturday...

Another problem is that the English translation function on the Scalemodels forum seems to be very unreliable lately - today when I tried it (several times) I kept getting a message at the bottom saying "Error on page", and no translation. I mention this because yesterday when it was working, I'm sure one of the participants in this thread ("А-Макетчик") said something which suggested he had some connection with Amodel, and that they learned after releasing the kit that something was wrong. Today I managed to copy and paste his post to Babel Fish; that translation says:

"Model was done in essence on the crosswind of Kondratyev + the measurements of console and tail assembly Yak-9 +[kniga] Of [stepantsa]. It is written in [Stepantsa], that on Yak-9U for retaining the centering with the heavier engine, the wing is moved forward 100[mm], that I strictly and made. When in me appeared the book Of [lyurancha] about Yak-9[P] with the [obrazmerovkoy] and the tying of wing to the fuselage, it turned out that in the real wing on Yak-9U/P was on the contrary, moved (in comparison with Yak-9) back. Thus on our model, wing is moved forward approximately on 2,8 mm. generally that, about this on [RUMODe] in the review paper about the models Yakov it is written sufficiently long ago, and I was confident, that this is well-known fact."

The reference to "RUMODe" is (I think!) this page:
http://www.rumodelism.com/sunduk/kit007.shtml

...which, when also given the Babel Fish treatment, yields the following on the Amodel Yak-9U kit:

"A -model? and here it differed, having recently let out the latest of the warred modifications of this fighter - Yak-9U with the motor VK -107. Review of this model in ?M-[Khobbi]? of № 2-2004 was very favorable. And to me castings were at first greatly pleased, the study of model, it seemed, at the high level, in spite of the casting of low pressure.

But here during assembling of enthusiasm it [poubavilos].

Materials on Yak-9U war time and drawings for this modification to scale 1:72 are published in the journal ?aviation and the time? of № 3 in 2005 g. the fuselage of model and wing separately to them correspond rather well, on the wing, true, practically there are no air ducts in the root. And the serious oversight of developers here was revealed - with jointing of fuselage and wing the latter is displaced forward almost to five millimeters, because of what indistinct characteristic fairing came out. Without the surgical intervention not to manage - wing must be shifted back and sealed the formed hole, but the fairing about the water radiator to, on the contrary, displace forward, for which it is necessary to saw. And, it is subjective, [melkovat] it somehow, although corresponds to drawing, possibly, it is worthwhile to increase to the millimeter, once already this matter."

Some further investigation should be useful... 

John

[John Thompson]

Well, here are some more details of my struggle to understand the Yak-9U and its proportions! The monograph Skrzydla 20 (Yak-9P; much as I want it, I don't have No.22, which is devoted to the Yak-9U) has drawings by Zbigniew Luranc, which were apparently made using measurements taken directly from a preserved Yak-9P.

The main profile view in these drawings also includes those actual dimensions. What we need is a measurement which relates some fixed point on the fuselage to another fixed point on the wings. The distance from the bottom of the rudder post (ref. 7530 mm) to a point which (by coincidence) corresponds to the location of the main landing gear attachment point (ref. 2145) is 5385 mm. Dividing this by 72 to convert to the World's Most Popular Scale gives a dimension of 74.8 mm. Laying out this dimension on the fuselage and aligning the wings so that the landing gear location is 74.8 mm from the bottom of the rudder post results in a gap at the front of the wing of about 2 mm. So, based on this analysis, the wing, as Amodel made the kit, is 2 mm too far forward. This gap looks very similar in proportion to that shown in one of the images from the Scalemodels.ru thread (see below), but it's not anywhere near the 5 mm suggested in the Rumodelism article. The dimension of 74.8 mm also corresponds very well to the dimension used in the Scalemodels.ru image of 84.5 mm, which includes the chord of the rudder.

It's too bad the online translations which I quoted in my previous post are so poor; it would be helpful to know exactly what the original writers meant - one seems to be saying the error is 2.8 mm, the other says 5 mm. There must be some explanation for this disagreement.

Here are some images; the first one is from the Yak-9P walkaround on the Moskittech site:



The second one is from the Scalemodels.ru thread:



What I am trying to show is how the wing root fairing on the real aircraft extends well ahead of the leading edge of the wing, and how this corresponds to the gap created on the model by moving the wing back by 2 mm (approximately). This also means that the filling of this gap should be done by adding material (strips of plastic sheet, or filler putty) to the wing, not to the cutout in the fuselage as I originally imagined; this makes the task somewhat easier for anyone who wants to tackle it!

If I learn anything more, I'll certainly post it here! Assuming what I've written so far is correct (or close to it), the next problem, as Massimo recognized, is the possible need to relocate other details, such as the radiator housing, which is molded as part of the wing underside. Amodel might have located this correctly, relative to the fuselage, so if the wing is moved back 2 or 3 mm, then the radiator should be cut away and moved forward by the same amount...  

John

[John Thompson]

"Model was done in essence on the crosswind of Kondratyev + the measurements of console and tail assembly Yak-9 +[kniga] Of [stepantsa]. It is written in [Stepantsa], that on Yak-9U for retaining the centering with the heavier engine, the wing is moved forward 100[mm], that I strictly and made. When in me appeared the book Of [lyurancha] about Yak-9[P] with the [obrazmerovkoy] and the tying of wing to the fuselage, it turned out that in the real wing on Yak-9U/P was on the contrary, moved (in comparison with Yak-9) back. Thus on our model, wing is moved forward approximately on 2,8 mm. generally that, about this on [RUMODe] in the review paper about the models Yakov it is written sufficiently long ago, and I was confident, that this is well-known fact."

Does he mean that the wing was incorrectly shifted forward approximately 2.8 mm relative to the Yak-9, when it should have been shifted back instead, and therefore the real error relative to the full-sized Yak-9U is actually 2.8 X 2 = 5.6 mm? Or does he mean that the error is 2.8 mm relative to the real Yak-9U? A correction of 5.6 mm seems almost impossible, but would explain the figure of 5 mm in the other quote. Maybe someone who is a member of the Scalemodels.ru forum could ask "А-Макетчик" for clarification of this point? Thanks!!!       !!!

John

[Massimo Tessitori]

Hi John,
I think that he means that the first source mentioned to move forward the wing of 100 mm, that are 1.4 mm in 1/72; he did this; he, instead, should have moved it back of 1,4 mm. So, the total error is 2.8 mm.

By the way, there is an excellent profile photo of a U.S. captured Yak-9P on Yakovlev's piston-engined fighters, of Gordon and Khazanov; the photo is taken from the side, and shows the wells well aligned during a takeoff, being a nearly perfect profile. Do you need a scan?
Massimo

[John Thompson]

Thanks, Massimo - I should have thought of that possibility myself! 

Thanks for the offer of the scan, but I have a copy of that book, so I'll check it out tonight.

John

[John Thompson]

Here we go again - no wonder I don't actually build any models...

Tonight I opened my copy of Gordon and Khazanov's "Yakovlev's Piston-Engined Fighters" to page 134 to see the photo of the captured Yak-9P as suggested by Massimo. I decided to take measurements directly from this photo, rather than messing around reducing it to 1/72 scale. There is a slight perspective error in the photo, but I took this into account when measuring - I used a fuselage panel line which aligns with the landing gear location in the drawings as the actual landing gear location in the photo to eliminate the slight perspective change due to the wing axis not being perpendicular to the camera's "line of sight" (I hope that's clear!). Below I give first the dimensions from Luranc's drawing as referenced yesterday, then the measurements right off the photo for the same dimensions:

Luranc: Dimension from nose (minus prop) to main landing gear location: 2145 mm
Dimension from nose (minus prop) to rudder post: 7530 mm
Ratio: 2145/7530 = 0.285

Photo: Dimension from nose (minus prop) to main landing gear location: 42 mm
Dimension from nose (minus prop) to rudder post: 147.5 mm
Ratio: 42/147.5 = 0.285!

How about that!  So, this suggests (as if it was really necessary for me, of all people, to prove Luranc's drawings to be correct) that the dimensions on the drawing are accurate, certainly to within any sensible variation relative to 1/72 scale. Therefore, if the dimensions on the drawing are correct, then the calculation I did last night based on those dimensions is also correct. The wing needs to be moved back at least 2 mm to position it accurately. I say "at least" because it's extremely difficult (for me, anyway) to hold the parts together and measure the location of the landing gear at the same time; personally, I'm happy to accept А-Макетчик's error figure of 2.8 mm - apparently he was the one who was there "when it happened", so to speak.

One further point: The dimension from the nose (minus prop again) to the leading edge of the wing root where it wraps under the fuselage is 1160 mm. Converted to 1/72 scale, this equals 16.1 mm. Measuring the Amodel fuselage, this dimension is 16 mm (as closely as I can measure it). This shows that the wing root will be correct if the wing is moved back as described above, and the wing root built forward to the location as provided by the cutout in the kit fuselage; in other words, just what I said last night.

There - I hope you're all happy now... 

John

[Massimo Tessitori]

Hi John,
this looks credible, but don't make things easier. So one could add material to the front wingroot and air intake... the difference should be clearly visible in a drawing from above or below.
Could you, please, post a top or above scan of your best drawings of the type?
Massimo

[John Thompson]

These might help (from the Scalemodels.ru thread) until I get a chance to scan something (but it will be Yak-9P drawings, not Yak-9U, since I have Skrzydla 20, not 22):





John

[Massimo Tessitori]

Hi John,
so, the ventral cooler has to be moved forward of 5 mm too? And the small outlets?
Massimo

[John Thompson]

Hi John,
so, the ventral cooler has to be moved forward of 5 mm too? And the small outlets?
Massimo

Good news - using Luranc's drawings again, the lip of the cooler housing is located at 3670 mm back from the front face of the fuselage. Divided by 72, this gives a dimension for the 1/72 kit of 51 mm. Measuring with the wing in its forward position (as provided by Amodel), the dimension is 48 mm approximately. With the wing offset to the rear in its corrected position, the measurement is 51 mm! Therefore, the housing (which is molded as part of the wing undersides) does not have to be sawed off of the wing and moved forward, it can remain in one piece with the wing. Likewise, the oil cooler outlets do not have to be modified either.

Edit - Sorry, I should also have mentioned that the position of the Amodel cooler housing is correct relative to the flaps, etc., on the underside of the wings, so this also demonstrates that the housing does not have to be relocated.

John

[Massimo Tessitori]

Hi John,
this is a luck. But there was written something about a shift of 5 mm somewhere in the Russian post, and I see the profile of the cooler in the window of the piece in the photo from below, that seems to be repositioned. So, are the side view and lower view consistent?

About the use of photos: I think that they could be utilized with the due precaution. Parallax errors are  gradual, while an eventual local error in the positioning of wing and coler, well at the center of the photo, should be well visible.
I suggest to scan, copy and glue the photo on the drawings by using Photoshop into a separate layer; to change the color of the lines, and make the upper layer semi-transparent to compare drawings to the image.

Massimo

[John Thompson]

Hi John,
this is a luck. But there was written something about a shift of 5 mm somewhere in the Russian post, and I see the profile of the cooler in the window of the piece in the photo from below, that seems to be repositioned. So, are the side view and lower view consistent?

I think the 5 mm number came from the article on Rumodelism.com (see one of my earlier posts for the URL), and was in error; I pretty much discarded that after you posted your explanation of how the 2.8 mm (1.4 + 1.4) number was derived - what you said made perfect sense based on the comment by А-Макетчик in the Scalemodels.ru thread.

Regarding the alignment of the radiator housing intake with the drawing, I think maybe what's at issue here is the "correctness" of the drawings one chooses to believe. I compared the Amodel wing with the 1/72 drawings in Luranc's book and also the drawings in Robert Panek's Mushroom Modeller "Yakovlev Yak-9U & P" book, and the radiator housing intake aligns almost perfectly with both drawings. It might be off by 1 mm (or less), but not enough to be bothered sawing off the housing and moving it. If one thought it was important, it would be easier to reshape the intake slightly.

About the use of photos: I think that they could be utilized with the due precaution. Parallax errors are  gradual, while an eventual local error in the positioning of wing and coler, well at the center of the photo, should be well visible.
I suggest to scan, copy and glue the photo on the drawings by using Photoshop into a separate layer; to change the color of the lines, and make the upper layer semi-transparent to compare drawings to the image.

Massimo

I agree completely. I think photos can be used to evaluate dimensions of something that is directly in front of the camera, or in a situation where the photo is taken from a proper distance (for example, as in the article that you have on your MiG-3 reference page showing the nose length of early and late MiG-3's to be the same).

Unfortunately I don't have Photoshop, I only have the photo editing software that comes with Windows XP (Microsoft Digital Image Standard 2006 Editor). I haven't checked to see if it has the capability you describe, but I will!

John