1/48 Boeing YB-40

Boeing YB-40 Escort Fighter 1/48 conversion project

Images and text Copyright © 2009 by Matt Swan

Developmental Background
       The Boeing B-17 was developed to be a self supporting deep penetration bomber, supposedly able to fly high enough and fast enough to avoid most interceptors and to be armed heavily enough to adequately defend itself against any Interceptor that did catch it. It sure sounded good on paper but when reality collides with theory things don’t work out so well. In 1942 B-17Fs were taking unsustainable losses during daylight bombing raids over the European continent and in November 1942 the XB-40 prototype was proposed. The XB-40 was a Vega built B-17F converted to a gunship. A chin turret was added with two fifty caliber machine guns, both waist gun positions were beefed up with secondary Browning machine guns and a second top turret was added just aft of the radio room. The bomb bay was replaced with ammunition storage and additional armor was installed for added crew protection. In addition the waist stations were staggered to provide for better gunner mobility.
       At this point 24 Vega B-17Fs were shipped to the Douglas plant for modification to YB-40 (Y signifies service test aircraft) and many different configurations of armament were fitted to different aircraft including four gun chin turrets and tail gun position, 40mm nose and tail cannons and as many as 30 hand held gun positions. In May of 1943 the first of nine operational sorties took place against Saint Nazaire. July 4 1943 was the last of these sorties with the YB-40 tallying five confirmed kills, two probable and one YB-40 lost. The net result of the program was not promising as the additional weight from armor and increased drag from additional guns slowed the ship down making it nearly impossible to stay with the primary formation during the return flight. This basically ended the YB-40 Escort Fighter program however one very useful feature did result from the program and that was the twin gun chin turret which was installed on all G production aircraft.
       I went to Joe Baugher's aircraft serial number site and was able to find this list of YB-40 numbers and block numbers. Joe has a great site and if you need an American aircraft serial number he probably has it.

Lockheed/Vega B-17F-10-VE
       42-5732 Assigned to 92nd BG, 327th BS, got lost on delivery flight from Iceland to UK May 1943, force landed in peat bog on an offshore Scottish island after running out of fuel. Removed to Stornoway and repaired. The aircraft was returned to USA Mar 28, 1944 then transferred to RFC Ontario, CA May 18, 1945.
       42-5733 *Peoria Prowler* assigned to 91st BG Jul 1943. Returned to USA Nov 2, 1943 then transferred to RFC Ontario, CA May 18, 1945.
       42-5734 *Seymour Angel* to 91st BG Jul 1943. Returned to USA Jan 25, 1944 then transferred to RFC Ontario, CA May 18, 1945.
       42-5735 assigned to 92nd BG, shot down by flak Jun 2, 1943.
       42-5736 *Tampa Tornado* assigned to 303rd BG Jul 1943 then transferred to 379th BG Sep 1943. Had been retired from use at Kimbolton by Oct 2, 1943 when it was shown to attendees at a party for local children. Returned to USA Mar 28, 1944 then transferred to RFC Ontario, CA May 18, 1945.
       42-5737 *Dakota Demon* assigned to 303rd BG Jul 1943 as "Dakota Demon". Returned to USA Nov 2, 1943 then condemned as salvage Jan 6, 1946.
       42-5738 *Boston Tea Party* returned to USA Nov 2, 1943 then transferred to RFC Ontario, CA May 18, 1945.
       42-5739 *Lufkin Ruffian* assigned to 303rd BG Jul 1943 then transferred to 384th BG Sep 1943. Returned to USA Nov 2, 1943 then transferred to RFC Ontario, CA May 18, 1945.
       42-5740 *Monticello* returned to USA Nov 2, 1943 then transferred to RFC Ontario, CA May 18, 1945.
       42-5741 *Chicago* assigned to 91st BG Jul 1943. Returned to USA Nov 2, 1943 then transferred to RFC Ontario, CA May 18, 1945.
       42-5742 *Plain Dealing Express* returned to USA Mar 28, 1944 then transferred to RFC Ontario, CA May 18, 1945.
       42-5743 *Woolaroc* returned to USA Nov 2, 1943. Reclamation completed Yuma AAF Jan 18, 1944. This is probably the best documented YB-40.
       42-5744 *Dollie Madison* returned to USA Nov 2, 1943. Condemned Nov 2, 1943

Lockheed/Vega B-17F-25-VE
       42-5833 converted to YB-40. Transferred to RFC Ontario CA May 24, 1945.
       42-5834 converted to YB-40, later converted to TB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.
       42-5871 converted to YB-40. Transferred to RFC Ontario AAF May 18, 1945.
       42-5872 converted to TB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.

Lockheed/Vega B-17F-35-VE
       42-5920 converted to YB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.
       42-5921 converted to YB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.
       42-5922 converted to YB-40, then to TB-40. Transferred to RFC Altus Oct 8, 1945.
       42-5923 converted to YB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.
       42-5924 converted to YB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.
       42-5925 converted to YB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.
       42-5926 converted to YB-40 then to TB-40. Reclamation completed at Hendricks AAF, FL. Feb 13, 1946.
       42-5927 converted to YB-40. Transferred to RFC Walnut Ridge Dec 19, 1945.

The Conversion
       My initial attempt at this kit was using the B-17G kit but after a very short time I realized this simply would not work for several reasons; the fuselage of the G is slightly wider than the F (which the conversions was made for) resulting in having to narrow the fuselage to make the new extended nose glazing fit. The waist windows are too tall and need to be shortened to match the YB-40 profile. The cheek windows are totally wrong – they are wrong on the F model also but somewhat easier to fix. So with all this said I will use an old B-17F kit as my donor kit. Now I have reviewed the B-17 kit previously and you can click here for a look at the plastic and history of that kit. Now by ‘Old’ I mean OLD. This is a kit I picked up from Evil-Bay a few years ago for a ten spot. The previous owner had started the build working on the fuselage only. He used vast quantities of Testors Orange tube glue and brush painted the fuselage with gobs of silver and lime green paint.
       To salvage my donor kit I first froze the fuselage then snapped all the glue joints. Next the models pieces were stripped of paint in Chameleon Paint Stripper – good stuff. During construction you may see some spots of green here and there; those are the few remnants of the original paint job. For the base conversion I am utilizing a very nice package from Paragon Productions, set #4849, intended to convert a Revell B-17F to an YB-40. I want to really detail the interior so here is a list of aftermarket sets I’ll be including in this build:
       Eduard set # 49360 B-17 colored nose PE detail.
       Eduard set # 49361 colored mid-section (radio room)
       Paragon set # 4814 Prop governors and wing intakes.
       Paragon set #48052 crew access doors.
       Paragon set #48103 B-17 dropped flaps.
       Squadron set # 9551 B-17 canopy set #1.
       Squadron set #9552 B-17 canopy set #2.
       True Details set # 48010 B-17 E-G wheels.
       True Details set # 48509 Cockpit detail set.
       True Details set # 48510 Waist Gunner detail set.
       You can click on any of the links above to see what each of those aftermarket sets look like.
       Decals will come from several sources, some from the original Monogram kit sheet and some will be custom made by yours truly.
       Documentation of the YB-40s was not very good and surprisingly few pictures of aircraft survive. I was only able to find about half a dozen pictures of different aircraft. Even operationally information is scarce. We do know that fourteen of these aircraft were placed with the 327th Bomb Squadron, 92nd bombardment group and 91st BG. Where the other ten YB-40s were assigned is a mystery although four of them were converted to TB-40s. Of those documented in the 91st and 92nd bombardment group we have serial numbers and names for some of the aircraft. We know that the basic paint scheme was the same two tone olive drab over light gray as commonly found with the B-17F which makes sense since they were intended to blend into the formation. With this known information I now need to select an aircraft to model, I like the name Seymour Angel, serial number 42-5734 and there is no photographic evidence on this aircraft so I can speculate on some nose art and armament configuration. I think I want to do something along the ‘Avenging Angel’ thing with artwork and want to place some 40mm cannons in the tail and put some kind of meat grinder in the nose. I still need to do a little more research into Angel artwork but I believe the basics for my conversion are now in place – it’s time to start cutting some plastic.

All of the basic cut work on the fuselage is done now with the top fuselage sections removed along with all the crew doors. I have built three 1/48 B-17s in my modeling career, the G the F and the E but all before the release of the True Details resin sets. I went ahead and purchased these sets when they first came out in anticipation of future builds. This will be my first experience working with them and I shall begin with the waist section. Because I staggered the waist windows the interior view has changed and I will need to add addition rib detail on both sides and opposite the aft crew door. One thing I saw right away was that the True Details floor section is totally inaccurate for the B-17. It should not be a totally flat floor but a narrow flat walkway down the center of the fuselage with step like constructions along both sides. I don’t think this will be highly visible in this build so I will not worry about it but on any future Visible B-17 build this will be a major issue.

I used a variety of Evergreen plastic strips to make my additional rib detail. Often during the detailing process I would test fit the fuselage halves and look through the windows to see exactly what would be visible and what would not to save myself some work. I had to extend the floor pan on both ends as a result of the staggered windows also. After two evening sessions of detail work the waist section is as done as it can be prior to paint. While I did not have any serious issues with this TD set I probably could have made cleaner and more accurate detail work from scratch in about the same amount of time as it took to use this set and add the additional work.

Next on the agenda is to fix those nose windows. Using a piece of leftover vacuform kit plastic that was the same thickness as the kit fuselage I cut blanks for the windows. These were rolled on a razor knife blade handle to impart a small curvature to them then glued in place. The seam was filled with Mr. Surfacer 500 and sanded smooth when dry. The inside was also filled and sanded. After this is all set up I will mark out new windows and cut them out.

While I’m waiting for putty and glue to dry in the nose I’ll work on the cockpit. All original kit alignment studs were sanded off then the TD cockpit was test fit. Overall this is not a very good fit and is just plain difficult. I hear that many of the TD cockpit sets were shipped short one control column and one seat but mine appears to be complete. I almost ditched this set in favor of an Eduard set but figured since I own the thing I will do everything in my power to make it work. Next B-17 build will get an Eduard set and we’ll see for certain which is better then.

4/17/2009
Before launching into a major build session with the cockpit area I went ahead and finished the nose windows. Basically I measured the existing windows, laid a flexible stainless steel ruler down the fuselage and drew some straight lines that where aligned with the other openings. Once they were marked out I used a burr bit in a Dremel to open them up and finished things off with a diamond needle file.

Any raised panel lines that were destroyed during sanding were simply scribed with the back side of an Xacto blade tip. When all is said and done it will be very difficult to notice any difference with the panel lines. I plan on using the Squadron replacement vac canopies but these are configured for the Monogram G kit which means some work need to be done to the F cabin roof. I cut it back to the top turret mounting ring and also removed the alignment pins from the interior so they would not conflict with the TD resin walls. I think I am ready to start work on the cockpit area. I shall begin with a base of drab green here, I know it is common practice to use interior green or a zinc chromate green inside a B-17 but they were not all painted that way, some were indeed drab green and there is evidence of at least one leaving the factory with an all black front office.
When working with the TD pieces each individual piece needs to be test fit and adjusted about five times before any glue is applied. Some of the parts like the seat back supports are insanely delicate and require some very careful sanding and cleaning-up. I also had some micro-bubbles here so repair work was needed as well. Piece by slow piece it does start coming together.

Having the nose hatch open means you can see inside and I don’t want simply a blank interior. First thing I noticed from walk-around images is that the underside of the cockpit floor is natural wood. This is replicated with oil paints using Mark Therrell’s oil technique. Details to the bottom of the floor pan are made from various things found around my workbench such as old mouse wire, thin solder and scrap plastic pieces. Cables are made from invisible thread painted silver. There is a lot of stuff going on under the main cabin floor on one of these aircraft and I have no intention of duplicating all of it, I just was to give an impression of this stuff when someone looks in here and let’s be honest, unless the viewer is handling the model and using a pen light the chances of seeing 100% of the internal detail here is very small.

While this all may look easy from the rapid progression of pictures it takes some serious time. I have 2 and a half hours tied up in each seat in the cockpit. There is over eight hours of time involved in detailing the cabin floor and countless adjustments and test fits. The large yellow Oxygen tanks do not fit either, I had to shave almost a third off the back side of the bottom tanks to get everything to fit but some of this may be a result of using the F kit whereas the details et is intended for the G kit which does have a slightly wider fuselage. Ultimately I have reached a point where I am fairly happy with the front office. There is a little more plumbing to be done but it must wait until the moment that things get closed up. Now it is time to take a look at the Gunner/Navigator station.
Unlike the Monogram G kit the F does not have any detail aft of the Bombardier’s seat, not even a navigator station floor or table – this must all be scratch built. In addition I am not building a bomber; this is a pure fighter so there is no bombardier station and no Norton Bomb Site. I found a fuzzy picture in Detail and Scale of the nose of a YB-40 along with a simple line drawing that, between the two, gave me a fair idea of how the gunner’s station was configured. First we have a seat that is closer in appearance to the pilot seat than the standard office chair type of seat we usually associate with this area. Second, there is a substantial piece of armor plate in front of the gunner. With this information in hand I am ready to start cutting plastic.

As stated earlier I am using the Eduard colored nose detail set here which needs some modification for the YB-40 configuration but still offers lots of good detail. The basic floor pan is painted with drab green then hit with some random olive drab. The seat is manufactured from one of the original kit cockpit seats. If you’ll remember at the beginning of this feature I stated that this is a recovered B-17 kit, in the image below you can see what the original kit seat looked like including gobs of glue and what it ended up looking like. I’ll be working over the second seat for the radio operator’s station later on. As a last detail to the floor pan I spotted it with some interior green to add some color contrast to the nose of the aircraft. I need to fashion a table for the navigator and got into a little plastic surgery – things were going so well at this point that I went ahead and prepared the basic floor and bulkheads for the radio operator’s station as well.

4/29/09
Once the basic floor pan was attached to the forward cockpit bulkhead I was able to hold the assembly in place and mark the fuselage wall for detailing. After the ribbing that would be visible was installed the area was painted with drab green then hit with some interior green. Once the base colors were on I started to apply the Eduard details to the walls. While doing this the navigator and nose gunner stations were finished off as well.

Once all the PE details were completed and the navigator seat installed I sealed the nose areas with Future then applied a sludge wash. Once the sludge wash had dried I cleaned up the center areas of each panel with a damp cotton swab. Here are some left and right side views showing the detail level. I still need to pick up some E string from the music store to make my oxygen lines but basically the nose is now 99% complete.

These two images you can click to view larger pictures

Remember those bulkheads and floor pieces I made for the radio room? It’s time to start detailing them. Beginning with the floor I used the oil technique to create the wood grain effect. The forward bulkhead gets the basic shelving installed from the Eduard set then is airbrushed drab green flowed by some interior green before the balance of the PE detail is added. The fire can and Oxygen tank are made from salvaged parts tree sprues. After attaching the forward bulkhead to the floor I started to test fit this to the fuselage and was very unhappy with the general fit. To rectify the issue I went to my local hardware store and picked up a contour gauge for seven bucks and used that to make a new aft bulkhead and some better bracing for the forward bulkhead. Contour gauges make all the difference in the world when scratch building.

5/19/09
I had already done some scratch work on the forward bulkhead and did not want to repeat that so I simply made a second bulkhead using the contour gauge and glued that onto the back of the first bulkhead. The aft bulkhead was made from scratch using various pieces of fine Evergreen plastic strips with the base piece being salvaged vacuform sheet stock. I needed to blank off some areas along the lower sidewalls at the wing root. Ultimately I plan on having the aft top turret removable so you can see some of the internal detail and from test fits I determined that not much of anything would be visible along the sides. With this in mind I just cut pieces of stock sheet and placed them along the bottom sidewalls. I had to take into account the wing lock tabs and cut some small slots into the sidewall pieces so everything would fit in final assembly.

All the instrument details came straight from the Eduard detail set. The second seat for the ammunition loader (a peculiarity of the YB-40) is a left over from the True Details cockpit and nose set. If you get both sets you end up with a few extra pieces that are duplicated within the sets. The second walk-around air tank is scratch built from plastic sprue and the magazine is from a Skunk Lab-Works decal set. When I test fit this assembly to the fuselage it dropped right in – a perfect fit on the first try. Next I test fit the resin top piece and found some interference with the top of the forward bulkhead and the top of the radio operator’s chair. After some artful sanding of the resin I had a good fit and was ready to move forward.
And I do mean ‘forward’. I had made a run to my local musicians’ supply store and got my hands on some old guitar strings (for free). Now you may (or may not) wonder why I did that and what relevance it has to this build. I have a variety of O2 tanks throughout this aircraft but nothing for air lines. I’m using short piece of small guitar string to make my air lines which allows me to finish detailing the forward area of the model. I’ll also use some of this string in the radio room and the waist section.

You can click on these to get a better view of the details.

I guess it’s time to move into the waist section and do something with those twin .50s. The ammo boxes are done with a wood finish per Mark Therrell’s feature on How to get Wood found in the ‘Tools and Tips’ section. The ammo feed belts provided by Paragon are done with Model Master Steel as are the gun bodies. The gun bodies are also dry brushed with silver then washed with a sludge wash to provide some depth. As these subassemblies get ready to be installed I’ll be making hydraulic lines from fine solder. The waist guns on the YB-40 were hydraulically assisted to reduce fatigue on the gunner from pulling these heavy pieces around.

I kind of lost my motivation on the waist guns so decided to put them aside for a little while and turn to the ball turret. While the Squadron replacement vac set does include a new ball turret I elected to use the kit parts as they have better frame definition and I wanted some beefier plastic to work with when cutting out the hatch. I was not sure how much detail I was going to put inside this thing, I have some very good pictures of the ball turret interior but would you really be able to see it? Even with an open hatch? I decided to add some padding for the gunner on the base of the ball and on the inside of the door. This was made from folded paper towel soaked with clear parts cement and painted khaki. As a bit of trivia did you know that the ball turret was equipped with a parachute and could be jettisoned in the event of a jammed turret to give the gunner a better chance of survival? Moving right along I used some Eduard masks on the ball then primed it with interior green followed by some neutral gray.