1/72 Republic XP-47F Kitbash/Conversion of Academy P-47D Razorback

[TheRealMrEd]

Just when you thought it was safe to get back into the water, there he goes again...!

 

Hi folks,  getting ready to start the latest chop shop conversion for my collection,  the  one-of-a-kind XP-47F, which is historical on two accounts.  First, Republic Aviation's first use of the Langley Field Wind Tunnel's data on laminar air flow wings, probably (at least in popular thought) derived from the Curtiss XP-46, also possibly used later on the NA-73 Mustang series (P-51's, Mustang I's, etc.).  Although, it is also said that North American also had extensive prior testing at their disposal -- who knows?

 

Anyway, the second reason the aircraft is historical, is because when they added the laminar flow, more "straight wing" wing to the aircraft, it changed the CG, so that (8 or 10 inched were added to the front cowl area, a mod which stuck on the later C and D model, etc.

 

Below is all the information that I have been able to come up with, so far:

 

 

 

 

Along with some drawing, which I have cropped for my own needs:

 

 

The original drawing can be had in a discussion thread over on the WWII Aircraft Forum HERE

 

Although, I found mine elsewhere.  On the WWII forum, there is also a second set of drawings, and a conversation about which is correct.  I have made my choice, as you will see in this build thread, as I'm not getting any younger, and as they say, I may be running out of "daylight" some day.  Hopefully, not too soon, as I have a pretty larger "bucket list"!

 

For this build, I will use my usual, more inexpensive than other kits, Academy P-47D Razorback, and the old generic aftermarket resin cockpit set:

 

 

Also, if anyone has any more data or photos, please feel free to jump right in.  Also, a reminder to those old, seasoned  scratch-builder and conversion maestro's, this build will be detailed in the needed areas, and may be old-school and archaic to some.  Primarily I do this to show younger or less-experienced modelers how I happened to do it, in hopes that more will jump in and perhaps contribute new ideas about easier ways or alternative modern materials to get the job done a bit easier.

 

I shall commence anon, stay tuned.

 

Ed

[AdrianMF]

Front row seat! 🍿

 

Regards,

Adrian

[billn53]

Right beside you, Adrian!  

 

-Bill

[dogsbody]

Move over, please! And watch out, there's hot coffee in the cup.

 

 

 

Chris

[stevehnz]

I'm not too late by the look of it, should be able to get a decent view still.

Steve.

[TheRealMrEd]

Welcome aboard, one and all.  Hopefully this will be a relatively simple conversion.  We'll see!

 

I began by printing out the above-posted drawings at about 165% of original.  This was derived by trial and error.  Then, I cut  out an upper and lower view wing outline, which was placed atop, in this case, the right wing.  Next, the excess part of the original kit wing was scribed along the paper template, to mark the trailing edge area that needs to be removed:

 

 

Above right, the scribed line can barely be seen, but it's there.  The paper template has been placed under the wing, to show how much area I'll need to add to the wing tip, eventually.

 

Next, a paper template is laid on a piece of plastic card, slightly less than 1mm thick, the next to the thinnest piece I have in my possession:

 

 

Above right, two plastic card pieces will be needed, one for each wing.

 

Next the scribed trailing edge pieces are removed from each wing top:

 

 

Above right the "X" 's mark where material will have to be sanded/scraped, from the underside of the top wing halves.  Also note that both wing tips have been sawn off the kit wings.

 

Next, the plastic card template is cut out to fit around the wheel well, which are molded in to the lower part of the kit wing.  The arrow, below, points to where I've cut out to clear the wing guns, which I'll try to retain, while "A" points to a part of the plastic card template, which will be separated from the rest, and glued to the lower kit wing half, aligned along  the front edge of the wing. "B" shows the rest of the card template, notched out for the gear well. "C" shows the other wing half, turned upside-down, to show the amount that will have to be added to the wing:

 

 

Above right is shown the actual cut-out template that I used, along with a ruler for scaling your own, should you want to build one of these.

 

 

Next, the "X" again show the area where I'll first roughly sand down, then scrape, using a #11 X-Acto blade turned vertical, almost like a miniature cabinet scraper.  Since the whole aileron was molded into the upper half of the kit wing, we'll have to remove what amounts to the lower thickness of the aileron, if that makes any sense:

 

 

Above right, the second template is shown before cutting, where "A" will be the separate front piece, as described earlier, and the lower "A", which allows for a cutout around the kit flap, will also be removed.

 

Below, one wing glued up, and the other, not yet glued:

 

 

Above right, both wings now glued up, one turned upside-down, to show the areas that will have to be built out to create the new wings.

 

I'll let the glue dry for a good while, while pondering my next move.

 

Later,

 

Ed

 

[RidgeRunner]

Count me in, Ed!!!

[AdrianMF]

Nice. Milliput or car body filler time?

 

Regards,

Adrian 

[TheRealMrEd]

12 hours ago, AdrianMF said:

Nice. Milliput or car body filler time?

 

Regards,

Adrian 

Hi Adrian!

 

Neither, because of the scribing I'll have to do, I'll be using plastic card with maybe a little bit of CA, sort of like with the YF-105A build.

 

Ed

[AdrianMF]

Ah-hah! Gotcha. All plastic. That's why you have been so neat with the cutting. Makes perfect sense.

 

Regards,

Adrian

[TheRealMrEd]

Hello all.

 

While waiting for the glue on the previous work to dry (I prefer letting the Weld-On #3 "hot" liquid glue I use to dry overnight before sanding), I painted up the resin cockpit (although the kit cockpit is better than many others!) and installed ii into one fuselage half, using CA and my ever-present backup application of Formula 560 Canopy Glue, and then glued together the fuselage halves, gluing a small section at a time, waiting a couple of minutes between steps, allowing the glue to set up a bit before moving on:

 

 

Another build bonus here, as mentioned earlier, is that the "D" fuselage of the kit is already the correct length for the "F" model, thereby saving the usual carnage on the fuselage and wing fillets on some of my other P-47 conversions!

 

Next, the two wings, showing the slight amount that will have to be filled around the guns.  I'm not too concerned about the fact that these guns are aligned with the wings, rather than the horizon, as real guns were never mounted on this aircraft; they simply used wooden dowels, and I'm far more concerned about getting the wings to "look" right, as we'll probably never be able to get to the truth, as Republic's records were all destroyed:

 

 

Actually, when looking at the pictures of the real aircraft, the wooden dowel guns are also on the wing center-line, unlike the regular P-47's.  Another fortuitous benefit!

 

Before moving on, a permanent magic marker is used to darken the edges of the template pieces added to the wings, to show the center-line, which will be useful later, as you will see.

 

 

Next, on the underside of the wings, scrap pieces of plastic card are glued on, where needed, using liquid glue:

 

 

Above right, when dry, the newly-added pieces are trimmed with an X-Acto knife, and gently sanded close to the template shape.  Then, the process is repeated on the bottom side, where the top wing has been sanded, and the bottom wing has not.  The added bits of card, marked "A", show random sorts of colors, where in a previous life, they were used for testing paint sample, and are not significant to this project.  As I've said many times, I never throw anything away...

 

In the next picture, the arrow shows where two layers of card have been added.  This is only because I try to use the minimum thickness that is needed.  As I've also stated before, I hate sanding, an odd admission from a confirmed kit-basher and conversion hacker:

 

 

Above right, both wing halves flipped over, and the process repeated.

 

Below, the picture shows why the magic marker was used earlier.  In this picture, the top half of the wing has been sanded down close to finished thickness, while the bottom half has not:

 

 

When sanding in two directions toward the line, a true edge of the wing can be determined, avoiding a "wavy" edge.  This technique is derived from the old vacuform building days, where parts were outlines with magic marker to tell you when to stop sanding.

 

As an aside to those who may be interested, another vacuform kit is in the building queue, coming up in the not-to-distant future...

 

Back later,

 

Ed

 

 

 

 

Edited February 2, 2023 by TheRealMrEd
monor addition

[Gondor44]

Interesting, the three view drawings of the aircraft show the difference in the wing which I easily caught though not everyone would see the difference as although its there it's not a huge change to the planform.

 

Gondor

[TheRealMrEd]

On 2/4/2023 at 12:54 PM, Gondor44 said:

Interesting, the three view drawings of the aircraft show the difference in the wing which I easily caught though not everyone would see the difference as although its there it's not a huge change to the planform.

 

Gondor

Yep Gondor, I only wish there were more views.  I'll just interpret them as to what I think should be reasonable.  Guess that's all we can do.

 

On another note, here we go again!

 

The cockpit has had the seat and  control stick added, and the needed surrounding areas have been painted before attaching the canopy:

 

 

Above right, the canopy has been added, using G-S Cement.  When dry, the usual scrub with 99% alcohol will be applied, to get any over-use of the glue removed.

 

Back to the wings, a couple of sawn-off bits of Lite-Brite pegs are used for the wingtip light lenses:

 

 

Above right, the gaps in the lower wings around the guns have been filled with Vallejo Plastic Putty (the long snout comes in handy here), and the putty is the smoothed out with a brush that has been dipped into water.  In the photo, only the wing on the left has been done.

 

Next comes the re-scribing of totally fictional panel lines.  I suddenly had an epiphany, the idea of using a Glue Looper tool to only apply thin CA cement to just the panel lines that I wish to fill,  rather than sort of smearing it all over the place.  Not sure if I read it somewhere, but it sure makes life easier!  Below is shown the scribing process in mid-stride. The "glue holder" is a plastic cup off a cough syrup bottle, heated with a hair dryer/paint remover gun, and while soft, poked with a paint brush handle, giving me a nice deep well to hold a drop or two of thin CA, and it doesn't tip over easily!:

 

 

Above right, the scribed upper wings.  the "X" 's mark spots where older lines have been filled with CA and sanded.  While being totally smooth, you can see where they were originally.  Also, please note that the ailerons end at the wing tip cap, and are very narrow at that point.  Easier seen on the right wing is the fact that the ailerons and flap do not meet.  There is a small gap.  I got that from blowing up (4x) the right rear view photo of the actual aircraft, and massaging it a little with AI.

 

The wings having been glued to the fuselage, the next picture shows "A", the original landing light hole filled, "B" it's new location drilled into the wing, "C" the newly-sanded smaller wing filet, vs. the original shape "D".  The "X" 's show where CA has been used to fill the old flap end part of the original kit, because although hard to see in this photo, the "F" model flaps ended before the wing filet, on both the top and bottom sides.

 

 

Next, the arrow shows where the "belly bump" of the "D" model kit has been flattened a bit, as the "B" model that the "F" originated from, did not yet have the added depth, for the center-line bomb mount of later versions.

 

 

Above, "A" shows where the exhaust outlet has been flattened a bit (B model) and "B" shows where the rear most outlet has been flattened, as that outlet was added to later models.

 

Below a denture floss pick has been used to "sand" between the gun barrels, and a small knife-edge file gas been used to clean up some small mold-parting flash from the gun barrels themselves.  Or in this case, I should say "wooden dowels" rather than gun barrels!

 

 

Next, getting ready to mask the canopy, using a set of commercial masks.  One of the problems that I have with commercial masks, particularly the yellow ones, is figuring out where each masking "shape" is on the sheet.  I decided to try adding a small bit of graphite dust from pencil lead scraped off a pencil lead, right out of Sherlock Holmes' bag o' tricks:

 

 

Above right, when smeared around with a finger, the edge "pop" a little more.  Only a tiny bit was needed, as I work under pretty strong magnification.

 

Well, I'll apply the masks to the canopy, and head for the paint booth. 

 

See y'all later,

 

Ed

 

 

[billn53]

Excellent!

[Lúcio]

On 1/31/2023 at 7:28 PM, TheRealMrEd said:

Anyway, the second reason the aircraft is historical, is because when they added the laminar flow, more "straight wing" wing to the aircraft, it changed the CG, so that (8 or 10 inched were added to the front cowl area, a mod which stuck on the later C and D model, etc.

Well, I hate to be the bearer of bad news but two pictures in Warren M. Bodie's "Republic P-47 Thunderbolt From Seversky to Victory", page 219, shows clearly that the XP-47F had B-model standard fuselage lenght, no extra front section as in C and later models. 

Text in another page mentions that the F received the QEC engine mount as in the C and later models but no mention of fuselage extension. 

Cheers,

Lucio

[TheRealMrEd]

1 hour ago, Lúcio said:

Well, I hate to be the bearer of bad news but two pictures in Warren M. Bodie's "Republic P-47 Thunderbolt From Seversky to Victory", page 219, shows clearly that the XP-47F had B-model standard fuselage lenght, no extra front section as in C and later models. 

Text in another page mentions that the F received the QEC engine mount as in the C and later models but no mention of fuselage extension. 

Cheers,

Lucio

Bad news back atcha!   Guess I should have posted the entire drawing, instead of just the portion needed.:

 

 

For those who didn't follow the link above, or with challenged eyesight, here is a larger version of the text.  Of course the aircraft started as  a plain "B"model, but then was modified.  The Quick Engine Change was what developed BECAUSE of the lengthening. Please note stated length 36' 1 " vs the "B" model at 35' 5"  --- 8 inches all day long.

 

 

 

More information/debate always welcome.

 

Ed

Edited February 9, 2023 by TheRealMrEd

[Lúcio]

Hi!

I started the thread in the link above and posted this drawing. 

But then the pictures in the book tells a different story. 

I don't have an image hosting service but I will get one and post both pictures here. 

Cheers, 

Lucio

 

[TheRealMrEd]

That would be great Lucio.  What I suspect you are seeing is perhaps the P-47B that was modified into the  "F" model, before they found out that the C.G. needed to be moved.  Also, FWIW, the test pilot felt that the handling of the aircraft was better with the 8" addition; another reason the QEC was happily carried forward to the later models.

 

Ed

[Lúcio]

I posted the relevant part of both pictures in the original thread:

https://ww2aircraft.net/forum/threads/xp-47f.51737/#post-1804020

Lucio

[TheRealMrEd]

Thanks, Lucio.

 

I responded to the photo in that thread, and unquestionably, that particular photo shows the shorter "B" nose.  Whether that was the final arrangement of the XP-47F remains to be seen.  I'm still thinking that they discovered the C.G. issue some time after the first flight with the new wing, but that does seem sort of silly for engineers not to predict such a simple thing!  Hopefully, one day, the mystery will be solved

 

Ed

 

 

 

[TheRealMrEd]

Hello again.

 

After masking the canopy and wing tip lights, the whole model was sprayed with a coat of Alclad2 grey primer.  Then, the undersides were done, using MM FS# 36270 Neutral Gray, and the top side was painted Colourcoats O.D. 41.  After that was dry, the area where the decals :would go was sprayed with Alclad2 Aqua Gloss, to give a smooth surface, and the few marking were applied with decals from the spares box.

 

 

Above right, the underside still has to have the tail-wheel "shim" painted, as I did on the P-47B Double Twister build, and the wheel wells given a black wash.  When all that was done, the entire aircraft was given a coat of Alclad2 Semi-Matte clear top-coating.

 

Then, the masking was removed, only to reveal:

 

 

Smutz inside the cockpit.  This occurred because my stupid self drilled the hole (arrow) to mount the aircraft on a piece or wire in a vise for painting, was drilled AFTER I buttoned everything up! Doh!

 

I managed to more-or-less save the situation by turning the model upside down, and using the tiny syringe-type eyedropper shown, injected a few drops of alcohol into the aforementioned nose hole, swished it around, then turned the model over so that the "smutz" could fall to the bottom of the cockpit, where it can;t be seen:

 

 

A

 

A clever solution you say?  Not so fast!  Because I had glued the canopy on with G-S watch cement, the alcohol dissolved some of that and ran out around parts of the canopy, where it promptly ate random bits of the topcoat and the O.D. 41,  which then had to be repaired, touched up, and ranted at.  Note to self:  when gluing an a canopy with G-S cement, water only must be used to clean out smutz that you never should have caused in the first place!  Did I mention that I'm old...?

 

Anyway, eventually all the odd parts were added, and she's done!  Since the only thing really different from the usual P-47's is the wing, I will only post a couple of pics here, and no RFI:

 

 

 

I used a little skin oil from my forehead to wipe on the sides of the fuselage, behind the cowling, to represent oil from the vents that has been wiped off by the ground crew, to give a little variation to the paint.  Remember, the P-47's didn't have exhaust residue on the fuselage sides, and since the guns barrels on the "F" model were simple wooden dowels, the would not be any "gun blast". 

 

The last remaining controversy about this aircraft, is the length.  I think that the picture mentioned by Lucio above, posted to the other group, clearly shows that at least at one point in it's life, the XP-47F had the normal, shorter length of the P-47B.  The discussion about this may never be resolved, but please look at the WWII group link mentioned, if you are interested.  I have also posted the NACA Langley wind tunnel report on the "F" wing, in that group.

 

In short, you can be certain, that if you use a shortened "B"model for this "F" variant, you will for certain be correct, for at least one point in time.  In 1/72 scale, at this time, we have no good version of a "B" model.  The old Lindbergh kit is accurate as far as shape goes, but to bring it up to today's kit standards would, I think, actually be more work than sawing the nose off another Academy razorback kit!  I know this, because I have one before me on the bench, and have been contemplating this madness for a couple of weeks.  Not sure if/how I will proceed, as I would like a pure "B" in the collection.  Do you suppose that Dora wings new 1/48 scale kit would be scaled down one day for us pure followers of God's Own True Scale?  One can only pray.

 

Meanwhile, here is a comparison, between this XP-47F model, and my earlier build of the XP-47B prototype, for easy wing comparison:

 

 

 

Here, the difference in fuselage length can be clearly seen.  I have shown how to build a short nose of the "B", converting the Academy "D" razorback kit, and this build thread shows how to build an "F" wing.

 

Go ye forth and build!

 

Ed

 

 

 

Edited February 13, 2023 by TheRealMrEd
pressed the wrong button!