Need for Research

[Ivan]

Hello All,

Warning: This is going to be a bit long winded.

I released a Birdcage Corsair a few months ago. It had been sitting for a couple years. I originally started it because someone wanted a Night Fighter Corsair with a Radome and the NF Corsairs had the framed Canopies.

The Corsair was a Project I started MANY years ago, back in 2001. This was my second completed aircraft design project. The ones before were a N1K2-J Shiden KAI which was lost entirely with a disk crash and a P-51A Mustang which was completed.

At the time, my view of CFS aircraft was that they were generally very crude. I was also trying to learn how to use Aircraft Factory 99. Each project at the time had a well defined goal. The goal for this project was to figure out how difficult it was to build an aircraft with a cranked wing such as a Stuka or a Corsair. I had found a few Corsairs available for download but other than the Alain L'Homme F4U-5, none of them were very good. Many folks repainted that post-war Corsair to be wartime versions. To me, this didn't seem appropriate because the -5 version had cheek pouches and a 4 bladed propeller unlike the wartime -1 Corsairs.

The idea of proper research didn't come up because I figured that very few of the aircraft for CFS actually looked like the real thing and also because the greatest concern was problems that would come up in actual building.

I spent probably not more than an hour or so in finding a drawing that looked like a Corsair. The next few days were spent with a dial caliper in measuring dimensions and using a calculator to translate into AF99. Correctly translating the drawing was important. Never mind that the drawing itself was rather poor.

The result was a "Airplane" that didn't have any serious bleeds and kind of resembled a Corsair. There were serious shape problems which I didn't notice because it was a "CFS Corsair". The first revision corrected some minor shape problems. The second revision added a pilot. The third revision happened several years later when it finally occurred to me that the bends for the wings were way too far out (about 1 foot). During this rebuild, I found that there were LOTS of other shape problems. The Wings and Flaps got a total rebuild but were altered a bit to make them fit the original Fuselage.

That is where this project stands today. I have been debating for a while whether or not to re-release this project because the shapes aren't very good. I probably will anyway because most of the work is already done and it only needs a couple hours to complete little stuff.

The moral of this story is to do your research properly to prevent problems WAY down the road.

- Ivan.

[Ivan]

Thanks to Hubbabubba and Alain Breton before him, the idea of locating the Virtual Cockpit view and Padlock view together is not a difficult task. This shows a successful confirmation of the VC and Padlock Views being in the same location or at least VERY close.

- Ivan.

[Ivan]

In doing some further research, there appears to be several distinct canopy types for the Corsair.
The F4U-1 had a Birdcage Canopy
Later -1 aircraft had a small bulge in the first bay to hold a rear-view mirror.

The F4U-1A through F4U-1D had a Windshield Frame that came to a rounded point at the top.
The Windshield Braces at the front came together a bit as they went up.
The Canopy Braces disappeared between the -1A and the -1D models but the shape didn't change much if at all.

The F4U-4 had a flat panel on the front Windshield Pane.
The Windshield Braces appear from the front to be parallel as they go up.
The top of the Windshield frame was flat to match the front Pane.
The Canopy was noticeably more bulged.
The later versions lost the semi-circular part at the rear of the Canopy Frame.

The F4U-5 added a Dorsal Fairing on the Fuselage at the Aft end of the Canopy.
The Canopy was bulged even more and reshaped to match the Fairing.

This is a fairly good example of a F4U-4 even though the author called it a F4U-1D.
The -4 had a Chin Scoop while earlier versions did not.
Note that it even has the 4 cannon typical of a F4U-4B?

http://simhq.com/forum/ubbthreads.ph...lacement_.html

Research is a good and necessary thing.

- Ivan.

[Ivan]

There are some problems with these drawings, but I really wish I had knew these existed before I started my project way back. From these drawings, you can see what the profile should really look like.

The problems I have seen with these drawings are the following:
1. The Pitot Tube is too short.
2. The Front Braces for the Windshield don't look quite right. I believe the bottoms are too close together.
3. The Landing Gear Doors are not correctly shaped.

If I had gotten it this close, I would have been happy.

- Ivan.

[Seagull V]

Some info available on the net :-

http://www.voughtaircraft.com/heritage/html/down.html
http://www.alternatewars.com/SAC/SAC.htm
http://membres.multimania.fr/wings2/

Regards, SG

[Ivan]

Thanks Seagull V.

Those are pretty good references.

Now, the next question is how badly do I want to fix my old Corsair before I release it.

- Ivan.

[Ivan]

The F4U-4 had a flat panel on the front Windshield Pane.
The Windshield Braces appear from the front to be parallel as they go up.
The top of the Windshield frame was flat to match the front Pane.
The Canopy was noticeably more bulged.
The later versions lost the semi-circular part at the rear of the Canopy Frame.
.

Early versions (WW2) of the F4U-4 had Canopies and Frames visually identical to that of the F4U-1D.

- Ivan.

[Ivan]

It is amazing how relatively small changes in shape make the whole aircraft look wrong. The Purple is MY Corsair. The Black is Paul Matt's drawing. His looks correct. Mine does not. This overlay drawing surprised me a bit with how small the differences actually were. The Aft Fuselage on mine is actually not as fat as I thought. Paul Matt's version is more fat.

I'll let you all decide. I had to seriously reduce the image to upload here. Anyone who wants the full sized version (about 1.8 Meg) can email me for the full sized version. It is set at 1 pixel == 0.01 foot which makes it about 3500 pixels wide.

Comments?
- Ivan.

[Ivan]

A proper rework of this project requires some tools that I haven't built yet. I figure that the Cowl should be moved down a bit as should the Center of Gravity of the entire model. This project currently stands at Version 3 which has significant improvements in wing shape over the last version.

Perhaps this aircraft should be released before further rework?

- Ivan.

[smilo]

A proper rework of this project requires some tools that I haven't built yet. I figure that the Cowl should be moved down a bit as should the Center of Gravity of the entire model. This project currently stands at Version 3 which has significant improvements in wing shape over the last version.

Perhaps this aircraft should be released before further rework?

- Ivan.

as always, it's your call.
if you're happy with the current version,
then, release it. if not, wait until you are.

i've always seen the corsair
as long and lean, proportionally.
the short, fat models
just don't look right to me.
but, maybe, that's just my perception.
or maybe, it's my old screen resolution.

i can't help but wonder,
why the discrepancy in drawings?
are Paul's measurements off?
i can't that imagine your's are.

[Ivan]

Hello Smilo,

Actually your confidence is misplaced. I KNOW the drawings I used way back are not accurate. I didn't do my research back then. AF99 was the greatest concern at the time. These days it is different. AF99 is easy. The shapes are tedious.

I found out when I tried to use another of these drawings for the N1K Shiden and the Cowl Scoops didn't even come close to matching photographs in the same chapter.

I believe that for the most part, Paul Matt's drawings are pretty good. That is good for my Corsair also because as you can see from the overlayed drawing, there isn't very much difference between the Black Paul Matt Drawing and my Purple 3D Model. The only thing I did to create the two drawings to overlay was to resize mine to 3333 pixels long (33.33 feet) and the Paul Matt drawing to 3334 pixels (33.34 feet). I used 33 feet 4 inches for dimensions. The Paul Matt drawing specifies 33 feet 4.125 inches.

My perception of my model being overly fat isn't supported by the comparison with dimensional drawings. Even the Engine Cowl isn't too fat. It is just a couple inches too high which throws the shape off. The back side of the Rudder is VERY close. The Fin is fairly far off except at the base. The Canopy is too high and narrow but you can't see it from the drawing overlays. Almost everything lines up on the Longitudinal axis. If you look at the the Landing Gear Doors, there are some significan differences, but I believe that is where Paul Matt's drawings are NOT accurate.

Either way, I figured the only missing things were a "ReadMe" file and couple Screenshots. With the rebuild, the AIR file, Checklist, DP, and probably textures would all change.

- Ivan.

[Ivan]

This is an overlay against another profile from a different source. It actually looks closer than the first one. This one shows a slight difference in the Engine Cowl Diameter.

So Which one is the CORRECT one????

- Ivan.

[smilo]

who knows?
got any production drawings?

i would bet that if you found
5 different sets of drawings,
you would find 5 different values.

it seems to me that, at this point,
it's up to your artistic license.

[Ivan]

Artistic License is fine, but it is also good to know what one is "Sposta" loo like. The two things that seem to vary a bit even in photographs are the Cowl and the Fin.

I have been looking around for a good CFS Corsair lately. They seem to be quite rare.....
Anyone have a link to one?

- Ivan.

[hubbabubba]

Hello Ivan

I can't tell you what to do, but I can tell you what I would do in similar circumstances. First, I would not hesitate to make a "collage" of different blueprints, taking what I think was more detailed in one and only sketched in another. Second, I would try to find the "right look" in studying photographic evidence. With your keen sense of observation, this is the kind of game you're better at than anyone else. Third, I would recognize that there's no such thing as a "perfect Corsair".

In a book called "Whistling Death - The Test Pilot's Story Of The F4U Corsair", the author says that modifications were so often made on the production line that someone having worked there, with a good memory, could tell you which month/week/day such airframe was rolled-out. So, if you see two different rivets' pattern on Corsairs of the same era, don't make too much of a fuss about it.