P-51D wings issue

[TheFlogger]

Hello gents and ladies!

 

A fella gifted me Airfix's 48th scale P-51D. (The bozooka carrying one, I dropped its link below) I will receive it  within a week.

 

I had read that to increase speed, wing upper panels were filled on some planes.

 

I wonder if my plane had filled panels or not. I appreciate  if someone can enlight me.

 

https://www.scalemates.com/kits/airfix-a05131-north-american-p-51d-mustang--1015635

 

Regards from cold Ankara.

 

Cheers.

[Rolls-Royce]

The primary reason was to maintain the claimed laminar airflow on top of the wing in order to reduce drag, improving speed and range. When your plane came out of the factory, it had filled, primed, and painted wing surfaces. Diagrams showing which wing areas were treated have surfaced here multiple times.

Edited December 16, 2020 by Rolls-Royce

[elger]

This thread might be helpful:

 

[Tail-Dragon]

The P-51D had the wing panel joints, rivets etc. (as indicated) filled, sanded smooth, primed and painted silver to give the smoothest wing surface.

 

 

 

This restoration has the most accurate wings that I've seen ...

 

 

 

It seems that most restored warbirds have unfilled (re-skinned, perhaps?) wings. While beautiful and picturesque, not historically accurate.

Edited December 16, 2020 by Tail-Dragon

[TheFlogger]

Thank you guys, all you are great!😃

[11bravo]

Just a side bar, by the time the Korean War rolled around some Mustangs had their wings stripped of putty.  These were either left in NMF or the entire aircraft was painted aluminum.  

[TheFlogger]

Ok guys, I am gonna apply  vallejo putty on over wing panels.

 

Hope  to share it here  soon.

 

Cheers 🖐

[Duncan B]

I'm not sure how Airfix have treated the surface detail but Meng went to town and back with lots of detail which needs filling.  Eduard went half way by adding panel lines but no rivets.

 

Meng wing, before and after

 

Eduard wing

Those gun inserts on the Eduard kit just did not fit well at all so they needed lots of filling top and bottom.

 

I used Mr Surfacer 500 on the Eduard kit but found that it was actually too thick and took a lot of sanding to remove. I learned my lesson and used Mr Surfacer 1000 (white) on the Meng and that was a lot easier to deal with.

 

Duncan B

[Toryu]

14 hours ago, Tail-Dragon said:

The P-51D had the wing panel joints, rivets etc. (as indicated) filled, sanded smooth, primed and painted silver to give the smoothest wing surface.

 

This diagram, albeit seen in this or a similar form in forums frequently, is only partially correct. The wing panel lines were only puttied half-way across the chord (to about the forward line of the removable gun panels). For keeping laminar flow only the leading edge of the wing up to the point of maximum wing thickness needed to be as smooth as possible.

In the field the putty tended to get washed out, so that panel lines collected dirt and thus became visible again.

 

Cheers, Michael

 

[Graham Boak]

I agree about the forward part of the coverage.  However I think it unlikely that the filler would wash out because filler generally doesn't, and even if it did, it is covered by a coat of paint anyway.  I can imagine it working loose as the wings flexed in flight and combat.  I have seen it written that the crew chiefs had the filler removed in service because of the work in maintaining it, but it would mean additional work removing it all rather than the few bits that had come loose, and just what sort of discipline or pride in work was there in the USAAF anyway?  Would there be no-one, on any fighter group, who knew why it was there in the first place?  Given the publicity given to the laminar flow wing, and the service manuals, I rather doubt it.  That some aircraft flew for some time lacking some part of this filler, is more likely than complete removal.

 

I've also seen it said that no-one noticed any difference, which is easy to believe as natural variation between pilots, aircraft and flight conditions varied considerably, and pilots had better things to do than carry out carefully monitored, measured and analysed performance comparisons.  That it made no difference is another matter, although I was taught that laminarity cannot be maintained beyond the first 10-20% of the chord anyway without impractical additional engineering into boundary layer suction.  That however is an argument about the abuse of the term "laminar".  It doesn't mean that attention to smooth finishes doesn't matter.  Possibly small in effect, but superior performance is dependent upon a lot of small items, all of which add up and few of which make any "noticeable" difference in themselves.  See the wide variety in rear-view mirrors.

 

It has also been said that this was discontinued on post-war aircraft.  Given the run-down nature of the service and the lack of qualified men, anything that reduced maintenance would be seen as desirable, and a one off-task like removing the filler from wartime builds would weigh much less against the expected years of service.  And by then who really cared about anything but jets?

[Mark Harmsworth]

This, I believe, is a period photo which may help to show what's being discussed.

Mark

 

[Jackson Duvalier]

12 hours ago, Mark Harmsworth said:

This, I believe, is a period photo which may help to show what's being discussed.

Mark

 

 

A good illustration indeed.  Given the abbreviated ammo bay door it appears to be a -B or -C model Mustang, but that really makes no difference to the factory putty application as far as I know.

 

I must give this thread credit for inspiring me to break out Mr. Surfacer and have a whack at the wings of a stalled Franken-stang build last night.  Cheers, gents!   😎

[Ray_W]

On 12/17/2020 at 9:04 PM, Toryu said:

The wing panel lines were only puttied half-way across the chord (to about the forward line of the removable gun panels). 

 

 

Ignoring restored warbirds (I agree that "Cripes 'A Mighty" is well done) and rather looking at period pictures, I just do not see this to be the case. (see ending edit) Even weathered versions exhibit that smooth P-51 wing with a feint panel demarcation across the whole wing. This is further supported by the well argued and evidenced work of Jennings Heilig on factory puttying specifications with the same conclusions as posted above by @Tail-Dragon.  This topic is such a regular in the forums and I am yet to see compelling evidence that contradicts the drawing as shown. If someone has strong contradictory evidence on period aircraft then happy to see it.

 

Some photos:  

 

Note smooth wings with visible feint panel demarcation on a well-worked aircraft. Little evidence of wing rivetting. Note pronounced screw fasteners (typical on NMF P-51) and visible yet flush fuselage rivetting. 

 

Again smooth wings, feint panel demarcation. Note visible flap rivetting.

 

 

Also, an underside view - image as posted by Peter @Magpie22 in the HVAR thread. Note smoothness of underside - feint panel lines and rivetting just visible but easily could be filled and certainly not as pronounced as the un-puttied flap which has significant "oil canning".

 

 

And more photos can be posted. For me the jury has returned and given their verdict - puttied wings per the drawings with feint panel line demarcation.

 

Only thing I should add, as always, try to find photo evidence of your aircraft. Some Korean War era US F-51's appear to have stripped wings, but not all. Maybe some deemed it no longer necessary. In the NASA/NACA archives you can find reference that the NACA "laminar" (I use the term guardedly) profile did not significantly improve P-51 performance, at other than high sub-sonic speeds, being blamed on manufacturing limitations of the time and the need to keep the surface in exceptional condition. 

 

EDIT: I revisited this subject this evening and decided to study assembly and maintenance instructions for the P-51 and found the following for the Mustang 1 which agrees with Michael @Toryu 

 

 

I will do more research on the later models although I know of a detailed description for repair and use of putty on the later models that I have somewhere describing the "glass like" leading edge finish. It does not counter the "filled wing" theory though with fillers and good surface preparation, not putty, being used in the less critical areas. 

 

 

Ray

Edited December 18, 2020 by Ray_W
More info

[TheFlogger]

20 hours ago, Mark Harmsworth said:

This, I believe, is a period photo which may help to show what's being discussed.

Mark

 

 

Wouww, this tells  a lot. I didnt know panels were filled at begining of construction. Thanks!

[Toryu]

It is indeed difficult to differentiate between puttied and non-puttied areas because the P-51's panel lines and rivets are very neatly finished. The picture below shows the clean finish of the (non-puttied) fuselage, and also that almost no panel line is visible on the leading edge access panel of the gear attachment, which was neither puttied nor primed/painted.

 

 

This is the correct wing treatment diagram -

 

 

The following production picture shows the treatment forward and aft of the 40% line -

 

 

... and after assembly with grey primer forward and zinc-chromate primer behind it (the stars-and-bar is just a stencilled placeholder). The few panel lines in this area are still visible -

 

 

This is not in contradiction to the picture presented above by @Mark Harmsworth which - in my view - shows hastily primed (but not puttied) rivets on the rear portion of the wing. Rivets are still visible, particularly behind the gun doors. A final picture displays the silver painted wing (panel lines still there!) -

 

 

As the non-puttied areas were also primed and painted the difference vs. puttied areas is nearly negligible. Taking camouflage, field conditions and repairs into account it becomes an almost academic point for the modeller if he fills all or half or none of the panel lines. It very much depends on the surface quality of the kit.

 

Cheers, Michael

 

(All photos for demonstration only from Larry Davis 1996 'Walk Around P-51D')

 

[Ray_W]

@Toryu

Michael,

 

Thank you. Very compelling arguments. What was your source of the wing finishing diagram? The same Squadron publication?

 

Ray

 

 

[Toryu]

@Ray_W  Hi Ray,

 

Unfortunately I don't have the original source of the diagram. I found it during last year's Mustang STGB (my model here) in a very profuse thread on detailing a P-51D model (here). The P-51 - particularly in 8th AF service - has been one of my deep-dive subjects for more than 40 years, and I'm still learning...

 

Best, Michael

 

[Ray_W]

 

28 minutes ago, Toryu said:

during last year's Mustang STGB

 

Hi Michael,

 

Exceptional build and my favourite version too. Sadly, even in a COVID year, it is impossible to get around all the builds and I tend to be more focussed on my current GB area or what pops up in WW2 chat. I will be building a RAAF P-51D in the ANZAC GB and this is why I have been floating around all the Mustang panel line discussions and references. I'll be using the 1/48 Eduard kit and reasonably happy with their surface treatment as is.

 

 

 

Although, I am crazy enough enough to tone down the grooving in the wings. Thankfully not a lot rivets to fill, if any.  

 

Ray

 

 

[TheFlogger]

I am thankful to all who responded my question.

 

My 1:48 p-51D 'little indian' will be with filled panel lines.

 

Thanks again.