F4U-7 lower nose panels and under nose supporting structure, between the cowling ring and cowl flaps deeper than on the F4U-5/AU1?

[detail is everything]

@Tailspin Turtle in another topic you have said 'I’m limiting myself to filling around the edges of the many existing (and some excellent) F4U reference works'.

 

I have a question about the F4U-7.  Other Corsair experts may have the answer

 

Were the lower nose panels and under nose supporting structure, between the cowling ring and cowl flaps deeper on the -7 than on the -5/AU1?

 

The F4U-5, AU1 and F4U-7 development was meant to minimise re-tooling.  The main external nose area changes centred around air inlet arrangements on the cowling ring

 

Nose wise, the F4U-5 and AU-1 were (I believe) the same except the latter had the -5s supercharger ducting removed and the the cheek inlets on the cowl ring smoothed over. The nose shape and cowl flap arrangement remained the same with the space and supporting structure for the superfluous ducting retained to minimise re-tooling.

 

So I'm assuming the nose panels between the cowling ring and cowl flaps are the same for the -5/AU1.

 

Because the ducting was removed, possibly to reduce the glare from the exhaust stacks at night that had been a shortcoming of the -5, the exhaust indentation on the side of the AU-1 fuselage was located lower (encroaching into the removed ducting space) than the F4U-5's which had to sit above the supercharger ducting. The panels immediately behind the cowling flaps would thus be different due to the relocated exhaust indentation.

 

The F4U-7 was basically an AU-1 with an F4U-4 supercharged engine.  Whilst the 4 and the 7 both have chin inlets on the cowl ring, they are there for different reasons.  The -4s was to feed its supercharger, but the -7s was to feed its oil cooler.  This was because the tooling for the wing root intakes had been irretrievable altered, since the AU-1 was the last planned variant, so oil coolers could not go back in the wing root leading-edge intake slots -5 style.  On the -7, the wing root intakes fed air to the supercharger and carburettor. On the -5/AU1, the wing root intakes fed air to the oil coolers and carburettor.

 

It was not economically feasible to retool for the limited number of French aircraft being purchased, so room was found for a single oil cooler in the nose, just aft of the second row of engine cylinders fed by the chin inlet. Engine combustion and intercooler air was routed from the leading-edge intake slots.

 

The oil cooler ducting on the 7 went under the engine and I guess what I'm asking is, was the existing AU-1 space below the engine deep enough to accommodate the ducting, without deepening the nose between the cowl ring and cowl flaps i.e. were the lower nose panels interchangeable between the AU1 and -7?

 

Most illustrations of the -7 I see show a deeper fuselage between the cowl ring and cowl flaps, meaning the lower nose panels would not be interchangeable between the AU1 and -7

 

These illustrations help to illustrate what I mean

 

Many thanks in advance

 

Edited November 25, 2022 by detail is everything

[Antti_K]

This is all very interesting, as I have been studying the F4U-7 for some time now (and currently building the Hasegawa kit).

 

Combining data from various resources (including Tommy's excellent web page) has lead me to the following:

• F4U-5 tooling was used for the cowling for -7, but the internal structure for fasteners was completely different
• cowling panels weren't interchangeable between F4U-5/AU-1 and F4U-7 without modification
• it looks like that same panels for fuselage underside were used in AU-1 and F4U-7, and
• it looks like that only the cowling was deeper in F4U-7 than in AU-1

 

If you are building the Hasegawa 1/48 scale kit, remember to fill and sand flush those "former" oil cooler outlets.

 

Cheers,

Antti

 

[Tailspin Turtle]

Unfortunately, I don't have accurate enough drawings or pictures to be certain of the difference in the lower cowling between the AU-1/F4U-5 and the F4U-7. It's possible, because of the length of the cowl ring, that the oil cooler air scoop was the only significant cowling external shape difference between the AU-1 and F4U-7. However, in the low-fidelity side view drawings I have, it looks like there might have to be discontinuity in the side view between the aft end of the bottom of the cowl ring and the bottom of the lower cowling—like there is at the firewall of the all three when viewed from above compared to the F4U-4 and earlier Corsairs—unless the lower cowl panel was deepened at its forward end. There's also the question of the depth of the -7's oil cooler affecting the shape of the bottom of the cowling. I'll see what I can find.

 

Note: An admin has objected to my providing links to my blogs as they violate Britmodeller policy on advertising. If someone wants the link to my AU-1/F4U-5/F4U-7 post (or any other) please don't hesitate to send me a PM or contact me directly.

Edited November 28, 2022 by Tailspin Turtle
Clarification of the comparison in the second sentence.

[detail is everything]

Tommy

 

Many many thanks (again) for your help Tailspin.

 

This was my previous post on these three closely related variants, which (along with your excellent  'Tailhook Topic' blog on them) helped me and others better understand the differences between the variants, as partly summarised at the beginning of this topic.
 

 

[Seawinder]

22 hours ago, Tailspin Turtle said:

Note: An admin has objected to my providing links to my blogs as they violate Britmodeller policy on advertising. If someone wants the link to my AU-1/F4U-5/F4U-7 post (or any other) please don't hesitate to send me a PM or contact me directly.

If any admin is seeing this, allow me to state my opinion that this is a totally ridiculous policy. First off, TT's continuing, generous offering of expert information has been a tremendous boon to us modelers for years. Second, I fail to find any commercial content in his blog when I go there. Exactly what is he purported to be advertising? If Britmodeller policy doesn't allow this sort of collegial sharing of data, then the policy needs to be revised. Pip

[detail is everything]

Looking at the noses of a -5 and a -7, the latter's chin inlet is considerably deeper than the cheek inlets of the former.  Possibly because the single chin scoop has to allow a similar mass of air to be taken in as that by the two cheek inlets.  Even so, it looks as though the under engine ducting to the oil cooler would be outside the original AU-1 under engine nose structure, Giving a flatter under nose profile?

 

Compare http://www.frenchwings.net/navy/gallery/displayimage.php?pid=629&fullsize=1 with http://www.frenchwings.net/navy/gallery/displayimage.php?pid=926&fullsize=1

 

 

[Antti_K]

3 hours ago, detail is everything said:

Possibly because the single chin scoop has to allow a similar mass of air to be taken in as that by the two cheek inlets.  Even so, it looks as though the under engine ducting to the oil cooler would be outside the original AU-1 under engine nose structure, Giving a flatter under nose profile?

 

The chin intake (F4U-7) is the for the oil cooler only, so I'm not sure about the equal amount of air to be taken in. You are right about the nose profile. Check this in-flight photo showing a flat under nose profile: https://www.asisbiz.com/il2/Corsair/FN/pages/Vought-F4U-7-Corsair-French-Navy-Flottille-12F9-BuNo-133727-patroling-the-Suez-Canal-1956-01.html

 

Cheers,

Antti

[Greg B]

7 hours ago, Seawinder said:

If any admin is seeing this, allow me to state my opinion that this is a totally ridiculous policy. First off, TT's continuing, generous offering of expert information has been a tremendous boon to us modelers for years. Second, I fail to find any commercial content in his blog when I go there. Exactly what is he purported to be advertising? If Britmodeller policy doesn't allow this sort of collegial sharing of data, then the policy needs to be revised. Pip

We had discussed this with TT and informed him that we were happy for it to continue as was. Provided that the posts were just not links to his blog and nothing else.

 

Secondly, if you disagree with site policies the sensible option is to contact the admin team by PM instead of publicly. You may therefore then receive the correct information and avoid making a very public post that is incorrect.

[Julien]

On 28/11/2022 at 17:50, Tailspin Turtle said:

 

 

Note: An admin has objected to my providing links to my blogs as they violate Britmodeller policy on advertising. If someone wants the link to my AU-1/F4U-5/F4U-7 post (or any other) please don't hesitate to send me a PM or contact me directly.

No this is not true you were asked to provide reason and description for your links not just post a link without it. 

[Seawinder]

If I've ruffled any feathers, I apologize. Indignation got the better of my common sense.

Cheers, Pip

[Greg B]

No problems Pip

[Bill S]

@detail is everything  Here are a few more clues to the differences:

VS-806341-1       F4U-7    Panel Assem Engine Accessories Lower Wing Gap LH

VS-806341-2       F4U-7    Panel Assem Engine Accessories Lower Wing Gap RH

VS-80639-1         F4U-7    Panel Assem Engine Section Group Accessory Compartment Top

VS-80364             F4U-7    Shutter Inst Engine Section Group Oil Cooler (Rear of Oil Cooler)

VS-80620-1         F4U-7    Cowl Assembly (Nose Cowl)

VS-80622-1         F4U-7    Panel Assem LH (Lower Side Cowling)

VS-80622-2         F4U-7    Panel Assem RH (Lower Side Cowling)

VS-80655-1         F4U-7    Cowl Flap Installation

VS-80638-1         F4U-7    Panel Assem (Lower Aft and touching cowl flaps)

 

@Tailspin Turtle asked if I could help, alerting me to this post. I am working the cruddy microfilm scans I have to make them usable. 

Out of curiosity, how much detail are you looking to model? Just getting the same right? Un-cowled? Super detailed?

 

V/r

Bill

 

[detail is everything]

@Bill S many thanks for considering this.  It would be great if an explanatory/illustrative note could be provided for each of the changes you list above

 

for modelling purposes I'm really interested in the external differences between the -7 and its -5/AU1 cousins.

 

Comparing from an un-cowled point of view would be very interesting too. Especially if you could compare a -7 equivalent of the -5 photo below so you can see how the oil cooler ducting relates to the undernose cowling flap structure (i.e. did the oil cooler sit in front of the cowling flap structure or behind it, and if the latter, how did that interfere with the owling flap structure?, that sort of thing).

 

 

 

 

 

Personally I love detail (hence my user name) and there are rivet counters out there who would be interested in the super detail for model building purposes too.

 

Thanks in advance

 

 

Simon

[Bill S]

Here is the first of two drawings to help visualize some of the differences. First up the VS-80300 F4U-7 Power Plant Unit. You can see the air scoop, oil cooler location and shape.

[Bill S]

Here is the drawing of the engine cowling with notes about part numbers for various panels. Anything specific to the -7 had VS-8XXXX part numbers. I did see a slight mismatch where I joined a couple of images together, sorry.

[Tailspin Turtle]

Bill - excellent drawings. I was working on an illustration combining the F4U-4 chin inlet with the F4U-5  and came pretty close to the same outline. Have you got something similar on the F4U-5 and/or AU-1 so we can sort out this lower cowl flap difference (it looks like the difference might be very slight but required because of the slightly different lower cowling necessary to fair into the oil cooler air scoop)? Also, where does the oil cooler air exit? There should be a movable flap on the bottom of the fuselage aft of it.

Edited December 6, 2022 by Tailspin Turtle

[Bill S]

I have been looking for the same drawing of the F4U-5 for your comparison. I also found some interesting shots of the AU-1 with cowl flaps open.

 

The first attachment is a cowling installation drawing for the F4U-4. If compared with the earlier drawing I posted the difference in attachments and panel shapes are evident. Apologies for the dark lines, the microfilm was damaged.

 

 

This photo is the top view of an AU-1 Powerplant Assembly. Interesting to note the stand has a ring that allows the powerplant to be rotated for ease of work task.

 

This photo is LH view of the Powerplant installed in an AU-1,

 

 

The next three photos are various views of AU-1s with the cowl flaps open.

 

The final photo is the AU-1 powerplant on the stand RH side.

[Bill S]

@detail is everything and @Tailspin Turtle  Did you get what you needed?

 

My last post appears to have killed the topic.

 

bill

 

[detail is everything]

If you had similar photos for the -7, we could consider the differences.

 

At the moment my conclusions are  as per my post of 29 November i.e. the -7's chin inlet is relatively deep compared to the -5's cheek inlets.  and it looks as though the under engine ducting to the oil cooler would be outside the original AU-1 under engine nose structure, Giving a flatter under nose profile?

 

So the cowl ring and bottom nose panels between the ring and cooling flaps are unique to the -7.

[Tailspin Turtle]

15 hours ago, Bill S said:

@detail is everything and @Tailspin Turtle  Did you get what you needed?

 

My last post appears to have killed the topic.

 

bill

 

Bill - Thanks very much for those (I missed seeing them before). I'll take a look at the difference in cowl flaps when I get a chance.

 

[detail is everything]

On 12/19/2022 at 1:58 AM, Bill S said:

I have been looking for the same drawing of the F4U-5 for your comparison.

@Bill S any luck with that?

 

@Tailspin Turtle Looking at your blog on the matter, you say

 

Another is that the Corsair marked as a USMC VMA-212 AU-1, including BuNo, at the USS Alabama Battleship Memorial Park in Mobile, Alabama was actually a former French F4U-7;  the -7 cowl was subsequently replaced with an AU-1's, which still left miscellaneous antennas as configuration anomalies. It is now on display at the San Diego Air & Space Museum, again as an AU-1.

And the French F4U-7 war bird featured in a walk-around photo collection here: http://www.arcair.com/awa01/601-700/awa689-Corsair-Salaun/00.shtm is reportedly a converted F4U-5N. Its authentic cowl (note the bulge and chin inlet) reportedly came from the F4U-7 that was on display at Mobile, Alabama.

 

This suggests that  the cowl flap arrangement and support structure is common to all three variants with the exhaust indent position common to the AU-1 and -7 (higher on the -5).  You just have different cowl rings and air trunking and, in the case of the -7, a deeper bottom cowl panel.

 

On the -5 and AU-1, there is a curve up from the bottom of the cowl flap support structure to the bottom of the cowl ring.  On the -7, the cowl ring has a deep lower air scoop from which the trunking for the oil cooler runs back below the engine to the oil cooler which (I assume) sits in the space below the engine created by the deeper, flatter line of the bottom panel running back from the cowl ring air scoop to the the cowl flap support structure.

 

It is not clear to me where the -7 oil cooler sits in relation to the engine and cowl flap support structure.  I assume in front of the latter and fairly forward to maximise the created space which reduces rearwards. The photo of the -5 with engine panels off shows no space between the engine and the cowl flap support structure.

 

Some clarity would be appreciated.

  

 

 

[Bill S]

3 hours ago, detail is everything said:

@Bill S any luck with that?

No Sir, that nasty four letter word, W@RK has precluded any hobby research. I will keep it on my list of things to look for.

3 hours ago, detail is everything said:

  

 

 

 

[Tailspin Turtle]

9 hours ago, detail is everything said:

@Bill S any luck with that?

 

@Tailspin Turtle Looking at your blog on the matter, you say

 

Another is that the Corsair marked as a USMC VMA-212 AU-1, including BuNo, at the USS Alabama Battleship Memorial Park in Mobile, Alabama was actually a former French F4U-7;  the -7 cowl was subsequently replaced with an AU-1's, which still left miscellaneous antennas as configuration anomalies. It is now on display at the San Diego Air & Space Museum, again as an AU-1.

And the French F4U-7 war bird featured in a walk-around photo collection here: http://www.arcair.com/awa01/601-700/awa689-Corsair-Salaun/00.shtm is reportedly a converted F4U-5N. Its authentic cowl (note the bulge and chin inlet) reportedly came from the F4U-7 that was on display at Mobile, Alabama.

 

This suggests that  the cowl flap arrangement and support structure is common to all three variants with the exhaust indent position common to the AU-1 and -7 (higher on the -5).  You just have different cowl rings and air trunking and, in the case of the -7, a deeper bottom cowl panel.

 

On the -5 and AU-1, there is a curve up from the bottom of the cowl flap support structure to the bottom of the cowl ring.  On the -7, the cowl ring has a deep lower air scoop from which the trunking for the oil cooler runs back below the engine to the oil cooler which (I assume) sits in the space below the engine created by the deeper, flatter line of the bottom panel running back from the cowl ring air scoop to the the cowl flap support structure.

 

It is not clear to me where the -7 oil cooler sits in relation to the engine and cowl flap support structure.  I assume in front of the latter and fairly forward to maximise the created space which reduces rearwards. The photo of the -5 with engine panels off shows no space between the engine and the cowl flap support structure.

 

Some clarity would be appreciated.

  

 

 

There's an illustration of the -7 oil cooler installation in that blog post (https://tailspintopics.blogspot.com/2017/04/the-last-propeller-pulled-corsairs-f4u.html). Combined with Bill's -7 powerplant inboard profile posted in this thread on 5 December, the oil cooler is located just aft of the cowl flaps.  I'm sure that the -5 and AU-1 structure supporting the cowl flaps  isn't applicable to the -7, which is why there are different part numbers. With respect to the commonality evidenced by the conversion of the F4U-5 war bird to a -7 lookalike, I suggest that since it doesn't appear to have the oil cooler in the inboard wing leading edge, that it utilized more than just the cowling of the Mobile -7, e.g. to include the cowl flap mounting structure, cowl flaps, oil cooler installation, etc., possibly everything forward of the firewall. Since the Mobile -7 was rebuilt as an AU-1 solely for static display, its internal structure and hidden mechanisms on the bottom of the cowl and forward fuselage would not have to be strictly accurate, as the antenna configuration is not.

Edited January 29, 2023 by Tailspin Turtle

[detail is everything]

Thanks both, that is now super clear.  Now understand that the oil cooler is just aft of the cowl flaps.  As you say, the ducting to the -7 oil cooler would come into conflict with the lower -5 and AU-1 cowl flap mounting structure, From what you are saying, the conversion of the F4U-5 war bird to a -7 lookalike, was a lot more comprehensive than just swapping the cowling ring and lower cowling panel.  It is unfortunate that it has since been returned to a -5N.

 

An engineering maintenance manual or even photos of an actual -7 under maintenance would be handy.

 

Looking at WIKI, there are just two -7s flyable or otherwise.

 

133710      F4U-7    John O'Connor                               United States                                           Airworthy (though extensively damaged in 2019 so maybe not)

133722      F4U-7    Erickson Aircraft Collection            Madras, Oregon, United States               Airworthy

 

Neither represents an F4U-7!

No mention of a -7 in France!

Edited January 30, 2023 by detail is everything

[detail is everything]

Having trawled through the Erickson Aircraft Collection Facebook photo library (literally hundreds), I found the following which may be useful

 

 

 

 

-7 masquerading as a -4 for the film Devotion

 

compare with the AU-1 photo