Sovietwarplanes

Here's an interesting thread from Scalemodels.ru, with links to a really well-done Russian site which contains many documents and photos related to GPW weapons, vehicles, and personalities:
http://scalemodels.ru/modules/forum/viewtopic_t_23193.html

This is an excellent site, and well worth investigating carefully. The way some of the booklets are presented in a page-turning format is something I've never seen before - look for the one which shows Russian aircraft propellors, for example.

One of the links from the Scalemodels.ru thread produced this image:

(http://s2.postimage.org/5Hmwr.jpg) (http://www.postimage.org/image.php?v=Ts5Hmwr)

After some reading of Milos Vestsik's "Lavochkin La-7" and Yefim Gordon's "Lavochkin's Piston-Engined Fighters", I concluded that the aircraft in this photo is the La-5 "206" (the designation "206" was merely the last three digits of the aircraft's 8-digit serial number). This was a production La-5FN which underwent extensive tests and modifications in the TsAGI windtunnel during 1943, to try to refine the performance of the La-5 design. These modifications were eventually incorporated into the design of the La-7.

What is interesting (to me, at least!) is the shape of the La-5FN cowling in this plan-view photograph - it is clearly a bulged cylinder like the La-5 and La-5F, and not a straight-sided cylinder like the La-7. And certainly not onion-shaped, as sometimes shown in older drawings!

John

Hi John,
From the photo, it looks as if the horizontal plans were all covered by fabric, not only the elevator.
Massimo

Great picture, John.
The one observation I'd make is, it's still difficult to really tell the plan-form of the cowl without a direct-overhead view.  I suspect if the camera were moved so that we could see from overhead, it might be more of that "onion" shape of the La-5 and 5F.

Thanks, Greg! Personally, I think the onion-shape idea is incorrect for any of the La-5 series, but that's just my opinion - go here for Massimo's article on the subject, where he does leave the door open to either possibility for the La-5 and La-5F:
http://mig3.sovietwarplanes.com/la5/cowling/cowling.html

John

For those many visitors who just can't get enough of the topic of La-5 cowlings, check this out. Here's what usually appears in drawings and reference photos as the standard La-5FN cowling:

(http://s2.postimage.org/Lhrqi.jpg) (http://www.postimage.org/image.php?v=TsLhrqi)

Note the hinge line along the side of the cowling - the two joined panels open outwards and up, being also hinged at the top of the upper panel.


Now here's another La-5FN photo - the La-5FN intake is clearly visible at the top, as is the diamond-shaped "FN" logo on the side of the cowling; it also shows the flat exhaust outlet covers of the La-5FN:

(http://s1.postimage.org/hirQJ.jpg) (http://www.postimage.org/image.php?v=gxhirQJ)

In this second image, the same cowling panel locking devices as used on the La-5 and La-5F are visible. In this case, what was a hinge line in the first photo is now a joint where the upper and lower panels meet. Here, the upper panel opens upwards on a hinge at the top of the cowling, and the lower panel drops down on a hinge at the bottom.

So, apparently there were two types of La-5FN cowlings, early (the second image) and late (the first image). I hope others find this interesting!

John

Now there's a shock, differently designed and fitted components on the same type of soviet military machine!

:)

I've noticed the same, subtle discrepancies while pouring over photos in my references.  Sometimes the cowl looks very rounded, sometimes almost cylindrical.  Maddness, I tell you!

Hi John and Greg,
I think that the plates were made with simple curavatute (parts of a cylinder) but assumed the bulged look while closing the panel. Probably there is something protruding on the internal horizontal structure aside the engine, and the plates were forced between this internal part and two external steel coils when the panel is closed. This could be a way to prevent vibrations of the panel due to airflow.
Massimo

Hi all,
amazing how is this topic regularly revived but am afraid it's in the category of "beating the dead horse".
I offer rather simple and perhaps primitive explanation why the idea of "bulged", "onion shape" or, in other words, 3-dimensional shape of cowling panels on ANY La-5 version should be discarded:
1. no reason for it from engineering point of view, engine itself was of constant diameter and complex shape of these panels would present an unwelcome manufacturing nightmare
2. had the cowling panels been 3D how do you explain that in ANY picture the hinge line is STRAIGHT? Technically impossible, or isn't it?
Btw 2 different systems of panels installation/opening (as described by John Thompson earlier) are (should be) well known.
Too much of analyzing outdated drawings and pix taken from variety of angles? I don't know but on the most recent La-5 Zvezda 1/48 kits the cowlings are cylindrical. So are on 1/72 AML kits.
Mario

Good points; I was specifically referring to the La-5FN, though, not the La5 and La-5F, where the early version (with the clamps) is well known. I never saw it on a La-5FN before, but I probably didn't look carefully enough.

Re the 1/72 AML kits, this also is true, except for the La-5UTI, which has the "onion-shaped" cowling like the VES/Cooperativa "LaG-5", and as shown on the old (outdated, as you have pointed out) Voronin drawings.

John

Mario, you make a couple of good points.  Given the desperate need in the GPW to have easy-to-produce aircraft, it wouldn't make any sense to make anything more complex than it needed to be.  Also, drawings are not to be trusted.  I've learned this, sometimes to my regret, with drawings on the Shturmovik.

Regards,

Jason

Hi Mario, :)
it's not so obvious. On other similar planes, whose radial engines have the same type of symmetry, the cowling is onion shaped, as on the Kawasaki Ki-100.
From an aerodynamic point of view, this could be advantageous to reduce vortex formation. They are not difficult to build: many other panels of La-5 and other planes have double curvature, ex. the front ring.

Again, there is no reason to think that models are necessarily more accurate than drawings, and by sure not more accurate than photos.

I've already explained my point: the panels of La-5, all versions, are pieces of cylinder, but they curves when they are forced in closed position. This idea is based on photos. Unless one has quoted factory drawings or remains of the real piece, photos are the best documents that he has in his hands. :)

Massimo

Good points; I was specifically referring to the La-5FN, though, not the La5 and La-5F, where the early version (with the clamps) is well known. I never saw it on a La-5FN before, but I probably didn't look carefully enough.

Re the 1/72 AML kits, this also is true, except for the La-5UTI, which has the "onion-shaped" cowling like the VES/Cooperativa "LaG-5", and as shown on the old (outdated, as you have pointed out) Voronin drawings.

John
[/quote]
Supplemental info here
http://www.postimage.org/image.php?v=Pq1W1gyi (http://www.postimage.org/image.php?v=Pq1W1gyi)
Your 2nd pic may show very early production La-5FN (as indicated but "old" green-black camo?) where La-5 cowling panels hinge system was still retained. Just a theory.
Cheers,
Mario

Massimo,
I just wanted to contribute, after a long time! ;D ;D
Seriously, comparison to Ki-100 is not a good one. It's cowling is made of several individual panels fastened with Dzus'.
I don't think that aerodynamic cleanliness in that area of the airframe would ever overweight increased man-hours for complex parts manufacturing.
Sorry but I just cann't imagine, technically-physically, how can the straight part curve upon closing?
As I said initially there are pix and there are pix, I recommend to go through this thread to see some interesting ones
http://scalemodels.ru/modules/forum/viewtopic.php?t=2645&postdays=0&postorder=asc&&start=0 (http://scalemodels.ru/modules/forum/viewtopic.php?t=2645&postdays=0&postorder=asc&&start=0)
Cheers,
Mario

I'm with you completely here - this is a fairly important piece of the airframe, not a simple fairing, which might be flexible (e.g Spitfire wing root fairings).  The rings are clamps, not corsets.  However, any fairing that did bulge out would also open up a large gap, which is clearly not visible.

If it bulges, then it is specifically designed and manufactured to bulge.  As earlier aircraft are straight, then the only reason for doing this would be to reduce the cross-sectional area before and aft of the bulge - again, there is no sign of this.

Hi Marian, :)
your contributions are welcome, of course.


You are considering thin metal parts, as sheets and rods, as rigid pieces, and could be not exact. They could bend.
An example: imagine to bend sharply a piece of paper at 90? on a line. When the piece is shaped so, the line must be straight, as the rod of the hinge at mid of the sides of La-5FN cowling when it's open.
But if the sheet is made plain again, as when the cowling is closed, it can be curved, and the old bending line is not necessarily straight.

Now, imagine the open cowling of the La-5FN. When open, the rod of the hinge is obliged to be straight.
When the panel is closed but uncostrained, it becomes more flexible because its rod can bend freely.
But when the panels are closed and constrained, they become more rigid because their front and rear edges are pressed from outside to inside by coils, and a mid point is pressed from inside to outside by the internal strut visible aside the engine.

Massimo

Hi Massimo,
Sorry for being so persistent but what you're saying defies some principles of aircraft construction. Those pieces are supposed to be rigid, they not only cover the engine but also bear forces and tensions imposed on the airframe by aerodynamic forces. If you look at this pic again you'll see that those panels are strengthened from inside!
http://www.postimage.org/image.php?v=Pq1W1gyi (http://www.postimage.org/image.php?v=Pq1W1gyi)
Thickness of metal sheets covering the aircraft can vary from 0.6mm to 2mm. I just can not imagine how they can bend easily resulting, in addition, to material fatigue!
I didn't quite undestand what you meant "constrained by coils"?
Cheers,
Mario

Hi Mario, :)

For coils, I mean two thin strips of metal that seal the front and rear gaps of the cowling and are locked by some fast-lock tensioner; they are visible on photos, sometimes unpainted. They press the side panels from outside to inside. Should panels be undeformable, they would be unuseful.

This image shows the hinge of La-5FN seen from upper-front position, and the perspective shows the curvature. But I know that this could be the early type cowling without central hinges.
(http://mig3.sovietwarplanes.com/la5/cowling/cow5fn10.jpg)

I have not yet found a definitive photo showing the shape of the cowling of late type. The most satisfying available till now is
(http://mig3.sovietwarplanes.com/la5/cowling/cow5fnp1.jpg),
that shows a more straight line of the early type. Have you found better images showing this line?

There is a photo of La-5FN in factory, with the coils not yet installed, at pag.52 of  Lavockins' piston-engined fighters of Yefim Gordon. If the plate stays in closed position, it means that it has already found some stop, probably the longitudinal strut aside the engine and/or something on the lower side.
The hinge line appears straight, but a gap of some millimeters is visible on the front.
When the coil will be installed, it will press the plate aligning it to the frontal ring, and bending it. However, it's question of few millimeters only.

Apart  from the discussion on La-5, I would make some considerations about fatigue: all aluminium alloy structures of the planes are projected for a limited fatigue life. The structure of DC-3/C-47 is the only exception  that I know.
The rod of the hinge is, by sure, made by steel, that is more resistant to fatigue than aluminium alloys. Besides, if the tension due to deformation remains within the limit of the Wohler diagram, the fatigue doesn't affect the piece.
The important in-flight rigidity of pieces is the rigidity of the ensemble in flight condition, not the rigidity of separed pieces. As an extreme example, one can think to fabric, that is not rigid in itself but only when constrained on a metal structure.

Massimo :)



 

I agree with you that all aircraft parts will bend - making them totally rigid would make them too heavy.  You are also right that the strength of a structure is in the complete structure.  However, you are wrong that a panel edge, clear of a hinge, will move millimetres when tightened against a former.  It will move thous.  Thousands of an inch.  The metal isn't that flexible over short distances.

Even were you right, you are talking about only that part of the panel adjacent to the edge.  It will not result in a bowing effect over longer distances visible to the eye. Plus, as I said before, any bowing would result in distortion elsewhere and visible gaps and steps.

The metal strips around the cowling are simply fasteners, probably chosen to avoid the production problems of more normal fasteners and their resulting drag.  In order to produce the kind of compressive force your argument requires these cowl strips would have to be tightened with powerful jacks.  These don't seem to be visible in any photos I've seen, and indeed would rather run counter to the Soviet practice of minimal specialised support equipment.

If any were bulged, this was a design and manufacturing feature.

Here's a photo that was posted recently on Scalemodels.ru by mmoustaf. It shows a slight curvature of the La-5FN hinge line, which suggests that the cowling is, in fact, bulged slightly when closed:

(http://s3.postimage.org/TovNS.jpg) (http://postimage.org/image/34gvsjsec/)

Also of interest, I think, is the painted tips of the prop blades, not commonly seen during the GPW. The photo is captioned "Alexandr Matashov and Vladimir Morozov at Konigs", but is undated. As best I can determine, "Konigs" is the town of Konigs Wusterhausen, which is located a short distance to the southeast of Berlin. This was part of the area occupied by the Red Army during their advance on Berlin; the area in which Konigs Wusterhausen lies eventually became part of East Germany. This suggests that the photo was taken either very late in the war, or, more likely, early in the post-war period. If correct, it may provide some information regarding the implementation of painted prop tips on VVS aircraft.

John

Hi John,
good image; but we don't know for sure if this is an early-type cowling, or a late type hinged between the panels; so, it's difficult to take it as a proof of the theory that the hinge bends.
Regards
Massimo

You're right, although I don't see any sign of the latch which should be present if this was the early cowling.

Late La-5FN:

(http://s2.postimage.org/Lhrqi.jpg) (http://postimage.org/image/2nzvyedlw/)

Early La-5FN:

(http://s1.postimage.org/hirQJ.jpg) (http://postimage.org/image/z42zawck/)

I still think it's a late-type cowling, but I don't post these things to try to win arguments; I just like to present the "evidence" and let the jury decide for themselves. I'm easy... ;)

John

This metal distortion suggestion can be shown to be wrong with a piece of paper and a curved surface.  Being in the UK, I'd suggest a milk bottle, but any sizable cylinder would do.  Take the paper and fix one end, wrapping the other around the cylinder - imagine this the Lavochkin's engine cowling and trim to an appropriate size.  Now fix the other end.  The paper conforms to the curve of the cylinder, with straight sides.  Now loosen the bottom edge, and try to create a bulge shape in the side of the paper.  You CANNOT do this without creating large distortions and gaps around the edges of the paper, particularly the bottom edge.

If there was a bulge in the cowling, then it was preformed in the part, and will be visible with the cowling open or closed.  I'm reluctant to take sides, but I will point out that such a piece would require a heavy press, and be much more expensive in time and effort than a simple 2-D curve which could be done on any metal former.  It would also require curved interior strengthening pieces.  This doesn't sound like Soviet WW2 production methods to me.

Cann't agree more. It will be a simple cylinder to me until someone (in Russia) finds a wreck and prove it otherwise.
Cheers,
Mario

About the bulbs, hood, studied a lot of photos and different views. There are photos where the bulb is very well seen, there are photos where the bulbs are not at all. Does not depend on the time of release, or the modification or the state of the aircraft. In the technical description of the plane of the hood is written very little. I do not think that the bulb hood was originally intended. But it is.
 The most probable cause of the bulbs have already voiced Massimo. The fact that the hood on the La-5 blew down the special steel strips. The anterior and posterior junction with the effort. In the middle of the hood is the support ring deflector cylinder engine. On this ring glued felt tape to seal the joint. Depending on the shrinkage of the ring, and the tension force of tightening steel rings, the hood can deform considerably.
In working on a master model, I tried to do the hood in the form of an absolutely correct cylinder. So, it looks a cylinder shaped hood quite unlike the picture. So I gave a barely noticeable 0.5-mm follicle and hood soon became like a photo.

Thanks for the information, Musa! I had decided that I wasn't going to dispute this any longer, but regardless of what logic may suggest regarding whether it's theoretically possible for the cowling panels to deflect or not, the fact remains that some photographs do show the hinge line to be bulged, just as you've stated.

John

I understood we were talking about the sides of the panel, not the hinge line.  Is this not a piano hinge?  If it is, then it CANNOT bulge, for it HAS to be straight to work.  Not theoretical, but very real and practical.  This reminds me of the old (very old) plans and models of Bf109s, which had a curve from the cockpit to the nose instead of the real straight line, with the panel curving only outside the length of the hinge mechanism.

If it is not a piano hinge, ok, this posting is not relevant, but engineering realities are not "theoretical".

Piano loop can not operate in a bent condition is true. But the conversation is not about that. It is a strain panels hood during the contraction of steel bands. Due to the elasticity of the metal in the free state loop is rectified and everything is working.

I have doubts about that by itself.  However, for the hinge to bend, you are not only bending the (arguably flexible) panel but the rigid structure to which the other half of the hinge is attached.  This seems unreal to me. 

You also have to be opening gaps between structures - are these visible?  To say a little more about this, think of the circumferences of the sections.  It is one length where it is circular(ish) at the front and back of the cowling.  If it is to bulge in the middle, then it must grow to have a larger circumference, and this cannot be done without opening gaps.  Big, aerodynamically important, gaps.

If there is an "onion" shape to the cowling, then it was built that way not created by Samsonovitch bending metal structures.

Here's a picture from the factory documentation:
(http://s14.radikal.ru/i187/1012/03/85a71521c0e5t.jpg) (http://radikal.ru/F/s14.radikal.ru/i187/1012/03/85a71521c0e5.jpg.html)

Thank you, Musa - that's exactly what I expected. Slightly bulged in plan view, and not onion-shaped! How it gets that way is not important - both the drawing and photos show exactly what I've been saying.

John

Hi Musa, :)
those images are excellent, but represent the LaGG-3 M-82, that is the prototype, that had a slightly different cowling. To obtain a demonstration about late type La-5FN, we have to find images of that type with the hinge on the sides and see if it's curved or not when sealed by coils.
Regards
Massimo

Hello sovietwarplanes fans:)
Yesterday i recived Zvezda La-5FN 1/48
What do you think about its geometrical accuracy?

Hi Flanker! This thread from Scalemodels.ru might be helpful:
http://scalemodels.ru/modules/forum/viewtopic_t_21930_start_0.html

Also this one:
http://scalemodels.ru/modules/forum/viewtopic_t_2645_start_0.html

John

Superb. Have a question with canopy, and only small discrepancies with the stabilizer.

Thank you all.
Musa ,Zvezda La-5FN 1/72 is not scaled down 1/48?

Is there any aftermarket for Zvezda FN 1/48 ?
Are you planing to release new correct canopy?

It would be wonderful if the Zvezda 1/72 La-5FN was a scaled-down version of the 1/48 kit, but I'm afraid it's not. The 1/72 La-5FN is a very old kit that was first released about 25 years ago by Italeri. If you want a 1/72 La-5FN, the KP/Kopro kit (also reboxed by Mastercraft and Amodel) is still your best bet!

Regarding aftermarket for the 1/48 La-5FN kit, Vector has a complete cockpit set in resin, plus some other stuff - go here and scroll down a bit:
http://www.neomega-resin.com/vector/cockpits.htm

There was a vacuformed canopy available from Falcon/True Details, but I think it was intended for the Hobbycraft 1/48 La-5FN/La-7, and I have no idea if it was better or worse than the kit canopy - probably worse, but I'm only guessing now!

Musa can probably add some more items to your shopping list! ;)

John

No. He was already doing the "Vector".