Hello all!
I decided I need a place to compile all my findings from analyzing the many technical drawings I scanned from the Smithsonian's microfilm collection. It would be pretty difficult to find a more confusing aircraft to research or model, because of decisions made by Martin, the USAAF/USAF, and persistent myths that get repeated very often, and I want to spare any future researchers/modelers from getting confused or stumbling upon incorrect info. I plan on uploading some spreadsheets at a later date to replace my outdated and incorrect table found elsewhere on this forum. They will be:
-A table of all stations for the fuselage, wing, ailerons, wing flaps, nacelle, fin, rudder, stabilizer and elevator, detailing what parts were located where for each B-26 model.
-A table describing the production models listing serial numbers along with who's been converted into what.
-A table showing how many different versions of each subassembly existed, and what models used which.
-A table listing all B-26-MA and B-26B squadron assignments as best I've been able to find.
-A table describing the "B-26 Skeletons", a concept I'll explain later in this post and which I think will be very helpful for any future modelers and kit builders.
First things first: Defining Terms
Talking about the B-26 is by its very nature confusing, so I will do my best to avoid using conflicting terms. I will also be doing my best to use the language used in the technical drawings. I will also avoid using fractions when talking about dimensions because I find them annoying and they're harder to use in 3D modeling software.
Production Models
-B-26: the term I'll use for the rest of this thread when referring to all models of the aircraft, or nonspecific models.
-B-26-MA: the term I'll use when referring to the first production model, of which 201 were built. Martin and the USAAF just call this the B-26, which makes thing confusing. People (myself included elsewhere) usually call it B-26-MA, and while I have not found any official use of this name and the B-26 predates the USAAF's use of production suffixes (-MA, -MO), a way to refer to specific models is needed for clarity's sake so it'll have to do.
-B-26A: the term Martin uses to describe the A and A-1 models, because they are identical other than the engine
-B-26B: the term Martin uses for all short wing B-26B models (B-26B-MA through B-4), but only the short wing models. The Tail Section assembly was significantly redesigned to accommodate the new twin-gun turret, but the empennage stayed the same (with the exception of a new rudder with broader ribs from 41-17704 onwards). This new tail assembly made the fuselage 0.5" shorter than the previous models, at 698". The last 141 B-26B-4s may have had the "B-26B-1" waist gun positions installed at the factory. All B-26B-4s had a new longer landing gear strut that was mounted lower on the fuselage, I'm still researching its specifics as the only drawings I've found seem to contradict photographic evidence.
-B-26B-MA: the term I'll use to refer to the first production block of the B-26B, of which 308 were built. Again the same problem as the B-26-MA necessitates adopting unofficial terminology.
-B-26B1 Quick Fix (QF): Martin's term for the long wing B models fitted with the same manual turret as the short wing models (B-26B-10-MA & B-15-MA). Despite changes to the Aft Fuselage assembly to accommodate the new fin and waist gun positions, the most parts of the B-26B's tail section and its overall contours were maintained. I'll describe the long wing modifications in more detail in the Skeleton section.
-B-26C Quick Fix (QF): Martin's term for B-26Cs fitted with the same manual turret as the short wing models, effectively making this term interchangeable with "B-26C-5-MO" since that is the only production block it applies to. This production block was also the only one to retain the waist gun position from the B-26-MA and is often seen with the waist gun position of the "B-26B-1".
-B-26B1 Permanent Fix (PF): The tail section was once again redesigned to accommodate a Bell M-6 tail turret, as was the rudder for better streamlining with the turret's canopy. Stabilizer, Elevator and Fuselage Aft Section stayed the same. These modifications reduced the B-26's length from 698.5" (58' 2.5") to approximately 675" (56' 6"). Includes blocks B-26B-20 through B-55)
-B-26B1: Martin's term for all long wing B blocks. USAAF Tech Orders sometimes refer to this model as the B-26B-1, which is very confusing because of the...
-"B-26B-1": A term often used to describe B-26B-MAs bound for the MTO that were modified by Martin's Omaha Modification Center to be more combat capable. I'm not sure this term was contemporary nor who it was used by.
-B-26C Permanent Fix (PF): To the B-26C as the B-26B1 PF is to the B-26B1. Includes blocks B-26C-10 through C-45.
-B-26C, B-26F, B-26G: Pretty straightforward, Martin's terms for all C, F, and G production blocks. F and G models are also called "Twisted Wing" or "Drooped Fuselage", because the wing and everything attached to it (nacelle and landing gear) was rotated 3.5 degrees to increase takeoff performance. I don't know what point they were rotated around, but suspect either the center or bottom of the Center Wing's Rear Spar. I'm not very knowledgeable on the F and G models. Sharp-nose (not shark-nose, as sometimes stated, sometimes called Revised Leading Edge) aileronsmay have been introduced on the 51st B-40-MA, I am not sure whether any B-26Cs had those were introduced on the 1st B-26B-40-MA and the 76th B-26C-35-MO (the latter of which was built as an AT-23B delivered to the USN as a JM-1). Starting with the B-26F-2 the M-6 tail turret was replaced with the M-6A, which had a canvas cover instead of the semi-spherical plexiglass cover of the M-6.
Fuselage Group
-Nose Cone: Martin uses both this term and Nose Turret to refer to the Plexiglas nose cone, I prefer the former.
-Forward (Fwd) Fuselage: Martin's term for the forward fuselage assembly, which extends from station 33 to station 230.75. Contains the nose gear and the bombardier, pilot, co-pilot, navigator and radio operator's stations.
-Pilot's Enclosure: Martin's term for the cockpit canopy.
-Center Fuselage: Martin's term for the center fuselage assembly, which extends from station 230.75 to station 434.25. Contains the wing center section, the forward bomb bay and the aft bomb bay.
-Rear Fuselage: Term I'll use for the entire aft fuselage assembly, itself made of two large assemblies, which includes the entire fuselage from station 434.5 onwards and the tail turret.
-Deck Turret: Martin uses this term, Dorsal Turret and Upper Rear Turret to refer to the Martin 250CE electric turret located at station 460.25.
-Tunnel Gun: Martin's term for the ventral gunner's position. The gunner fires a .30 cal (sometimes replaced with a .50 cal) out of the camera hatch which extends from station 512.25 to station 548.375. This gun position as well as the camera hatch were deleted from the B-26B-10-MA onward.
-Waist Guns: Also called Side Guns in early Martin drawings & documents, there were three or four main configurations:
-Tail Section: Term I'll use for the assembly that extends from station 581.375 onwards. Contains the stabilizer's center section and the tail gunner's station.
-Fuselage Tail Cone: Removable endcap for the tail. Extends from station 693 to station 698.5 on B-26-MA & B-26A, or station 670.75 to station 698 on the B-26B. B-26B1s, Cs, Fs and Gs did not need tail cones.
Wing Group
-Center Wing: The section of the wing located inside the fuselage. The spars in this section are connected to station 230.75 and station 346.25 by shear webs and are straight and of constant section, perpendicular to the direction of flight when viewed from above. This section extends 46" from the fuselage centerline, to wing station 46.
-Outer Wing: The panel that makes up most of the wing. This section extends from station 46 to station 364 and can be divided into Nose Section, Main Wing Section and Trailing Section. The Nacelle and Wing Tip attach to this section.
-Wing Main Section: The section of the Outer Wing between the two wing spars, that the nose and trailing sections attach to. To this section attach the nose section, trailing section and landing gear.
-Wing Nose Section: The section of the Outer Wing forward of the forward spar, which is itself built of several smaller sections. Contains the landing lights, running light and deice boots (if fitted).
-Wing Trailing Section: The section of the Outer Wing aft of the rear spar, which is itself made of two sections. The inboard section contains the wing flaps, while the outboard holds the ailerons.
-Wing Tip: The section of the wing extending from station 364 onwards. It contains navigation lights and the pitot tube, as well as one of the aileron hinge brackets in the long wing models. Deice boots are also be attached to this section if installed.
Engine/Nacelle Group
-Nacelle: the term Martin uses to describe the entire nacelle assembly, including the engine hood. Stations are measured along the thrust line, with station 0 being the intersection of the centerline for the propeller blades.
-Engine Hood: the term Martin uses to describe the engine cowling. It is split into five (5) components: two (2) upper panels (which include the carburetor ducts), two (2) side panels and one (1) lower panel (which contains the oil cooler duct). Extends from station 6.6 to station 53.59 (for the upper panels) or station 54 (for the lower panel). These panels are attached to the engine via two mounting rings.
-Desert Cowlings: the term the B-26B manual uses for the engine hood upper panels fitted with enlarged air intakes to allow for installation of air filters. These were fitted to "B-26B-1s" and all production models from the B-3 to the G-25-MA.
-Venturi Cowl: the term Martin uses to describe the section of the nacelle aft of the engine hood and forward of the firewall (station 104.25), with holds the engine's accessories including the oil tank and oil cooler. It is split into five (6) panels: two (2) upper panels, two (2) center panels and two (2) lower panels. The two (2) fairings for the tailpipes are also a part of this unit and are located between the center panels and the lower panels. The upper panels extend from station 53.59 to station 103.65, the center panels from station 54 to station 114.74, and the lower panels from station 54 to station 103.65.
-Tailpipe: Martin's term for the exhaust stacks.
-Rear Nacelle: the term Martin uses to describe the assembly that extends from station 103.65 onwards. This section attaches to the wing outer panels and contains the landing gear doors.
-Nacelle Tail Cone: Martin's term for the removable endcap for the nacelles that extends from station 229.25 to station 262.16 on short wing models and from station 218.13 to station 262.16 on long wing models.
Skeleton
A WIP version of this is available here: B-26 Skeletons. See reply #12 for notes and instructions on it.
So, with that out of the way, what the hell is a B-26 Skeleton? Simple, it's what you get when you combine the smallest amount of information required to describe the airplane's geometry. For scale modeling, it's useful to figure out lengths and distances when modifying kits. For 3D modeling, it's a very helpful tool in order to accurately place all the subassemblies. These are still WIP but I plan on sharing the blender files for them once they are complete. Currently missing are the main landing gear, the nose gear doors and all other doors, the tail turrets, the wing flaps and the ailerons. I also have yet to add the arcs for the tips of the wings, stabilizer and fin. I also have yet to make a skeleton for the non-Quick Fix B1 & C or the B-26F & G, the latter two because I have very little information on then.
I will now use the skeletons as a visual aid to explain how the B-26's wings and empennage were enlarged. Black represents the B-26 and B-26B, while orange represents the B1/C Quick Fix. It's important to remember that Martin's priority was reusing as many components as possible, and keeping the attachment points the same.
First off, the wings. Martin kept the center wing and the wing main section's geometry the same, though the parts themselves were not kept. The nose and trailing sections were replaced with ones with longer chord at station 364. The new trailing section was significantly larger and responsible for the most noticeable change in the wing's shape. Since Martin had to redesign this section anyway, they switched from split flaps to slotted flaps as recommended by NACA. The old wing tip was replaced by a new unusually long unit which extended from station 364 to station 426. This made each wing 36" longer, for a total increase in span of 72" or 6'. Keeping the main section's contours meant the nacelles needed much less extensive redesign.
For the empennage, Martin had less constraints. As such, they essentially just extended the old units at the bottom. The fin and rudder grew 20", while each stabilizer and elevator grew 24.25".
While the old fin was held in place only by two bolts at the spar and a row of screws attaching its lowest rib directly to the skin of the upper fuselage, the new fin's lowest rib was now recessed and a new hinge bracket & bolt was attached to a bracket near the leading edge. As such, the fin now had three attachment points, wish the resulting skirt receiving a rubber strip at the interface with the fuselage. The lower section of the rudder was redesigned to still fit in the old fairing at the top of the tail section (note that the orange and black lines intersect at the bottom of the rudder trim tab's trailing edge). The main priority for Martin was keeping the rudder's attachment points the same, particularly the torque tube contained in the aft fuselage.
The theoretical rudder hinge's centerline was thus kept, while the fin spar and nose of the rudder gained a distinct break/angle in their lines. It's worth noting that with this change Martin also changed the datum for the fin's stations from a line tangent to the fuselage centerline to the theoretical base of the fin, which used to be station 34 (which was also the same between all models). So while the fin gained 20", one must subtract 14" from the short-wing B-26s' stations to find the corresponding stations and ribs on the long wing models. Most of the fin's ribs were reused.
The Stabilizer was trickier to modify because three mounting points had to be kept: the front spar, the rear spar and the elevator torque tube. Martin also wanted to avoid reshaping the fuselage frames entirely if possible. The solution was an extension that had constant section between the two spars, with only the nose ribs tapering. The elevator was a much easier affair, with Martin extending its bottom and then simply "cutting" (reshaping) the ends of the trim tabs so that they lined up with the pre-existing fillet from the B-26B. A new fillet and the two bulkheads that held the stabilizer's spars were some of the very few changes made to this section.
B-26B Tail (note that the angled/cut section ends at the elevator):
B-26B1 "Quick Fix" Tail (angled/cut section continues into the elevator, rounding off into the trailing edge with an arc of radius 5"):
Hope y'all find this informative!
-Matt
Edit: Revised 5 December 2024 to correct information on sharp nose ailerons, as per post #18.
I decided I need a place to compile all my findings from analyzing the many technical drawings I scanned from the Smithsonian's microfilm collection. It would be pretty difficult to find a more confusing aircraft to research or model, because of decisions made by Martin, the USAAF/USAF, and persistent myths that get repeated very often, and I want to spare any future researchers/modelers from getting confused or stumbling upon incorrect info. I plan on uploading some spreadsheets at a later date to replace my outdated and incorrect table found elsewhere on this forum. They will be:
-A table of all stations for the fuselage, wing, ailerons, wing flaps, nacelle, fin, rudder, stabilizer and elevator, detailing what parts were located where for each B-26 model.
-A table showing how many different versions of each subassembly existed, and what models used which.
-A table describing the "B-26 Skeletons", a concept I'll explain later in this post and which I think will be very helpful for any future modelers and kit builders.
First things first: Defining Terms
Talking about the B-26 is by its very nature confusing, so I will do my best to avoid using conflicting terms. I will also be doing my best to use the language used in the technical drawings. I will also avoid using fractions when talking about dimensions because I find them annoying and they're harder to use in 3D modeling software.
Production Models
-B-26: the term I'll use for the rest of this thread when referring to all models of the aircraft, or nonspecific models.
-B-26-MA: the term I'll use when referring to the first production model, of which 201 were built. Martin and the USAAF just call this the B-26, which makes thing confusing. People (myself included elsewhere) usually call it B-26-MA, and while I have not found any official use of this name and the B-26 predates the USAAF's use of production suffixes (-MA, -MO), a way to refer to specific models is needed for clarity's sake so it'll have to do.
-B-26A: the term Martin uses to describe the A and A-1 models, because they are identical other than the engine
-B-26B: the term Martin uses for all short wing B-26B models (B-26B-MA through B-4), but only the short wing models. The Tail Section assembly was significantly redesigned to accommodate the new twin-gun turret, but the empennage stayed the same (with the exception of a new rudder with broader ribs from 41-17704 onwards). This new tail assembly made the fuselage 0.5" shorter than the previous models, at 698". The last 141 B-26B-4s may have had the "B-26B-1" waist gun positions installed at the factory. All B-26B-4s had a new longer landing gear strut that was mounted lower on the fuselage, I'm still researching its specifics as the only drawings I've found seem to contradict photographic evidence.
-B-26B-MA: the term I'll use to refer to the first production block of the B-26B, of which 308 were built. Again the same problem as the B-26-MA necessitates adopting unofficial terminology.
-B-26B1 Quick Fix (QF): Martin's term for the long wing B models fitted with the same manual turret as the short wing models (B-26B-10-MA & B-15-MA). Despite changes to the Aft Fuselage assembly to accommodate the new fin and waist gun positions, the most parts of the B-26B's tail section and its overall contours were maintained. I'll describe the long wing modifications in more detail in the Skeleton section.
-B-26C Quick Fix (QF): Martin's term for B-26Cs fitted with the same manual turret as the short wing models, effectively making this term interchangeable with "B-26C-5-MO" since that is the only production block it applies to. This production block was also the only one to retain the waist gun position from the B-26-MA and is often seen with the waist gun position of the "B-26B-1".
-B-26B1 Permanent Fix (PF): The tail section was once again redesigned to accommodate a Bell M-6 tail turret, as was the rudder for better streamlining with the turret's canopy. Stabilizer, Elevator and Fuselage Aft Section stayed the same. These modifications reduced the B-26's length from 698.5" (58' 2.5") to approximately 675" (56' 6"). Includes blocks B-26B-20 through B-55)
-B-26B1: Martin's term for all long wing B blocks. USAAF Tech Orders sometimes refer to this model as the B-26B-1, which is very confusing because of the...
-"B-26B-1": A term often used to describe B-26B-MAs bound for the MTO that were modified by Martin's Omaha Modification Center to be more combat capable. I'm not sure this term was contemporary nor who it was used by.
-B-26C Permanent Fix (PF): To the B-26C as the B-26B1 PF is to the B-26B1. Includes blocks B-26C-10 through C-45.
-B-26C, B-26F, B-26G: Pretty straightforward, Martin's terms for all C, F, and G production blocks. F and G models are also called "Twisted Wing" or "Drooped Fuselage", because the wing and everything attached to it (nacelle and landing gear) was rotated 3.5 degrees to increase takeoff performance. I don't know what point they were rotated around, but suspect either the center or bottom of the Center Wing's Rear Spar. I'm not very knowledgeable on the F and G models. Sharp-nose (not shark-nose, as sometimes stated, sometimes called Revised Leading Edge) ailerons
Fuselage Group
-Nose Cone: Martin uses both this term and Nose Turret to refer to the Plexiglas nose cone, I prefer the former.
-Forward (Fwd) Fuselage: Martin's term for the forward fuselage assembly, which extends from station 33 to station 230.75. Contains the nose gear and the bombardier, pilot, co-pilot, navigator and radio operator's stations.
-Pilot's Enclosure: Martin's term for the cockpit canopy.
-Center Fuselage: Martin's term for the center fuselage assembly, which extends from station 230.75 to station 434.25. Contains the wing center section, the forward bomb bay and the aft bomb bay.
-Rear Fuselage: Term I'll use for the entire aft fuselage assembly, itself made of two large assemblies, which includes the entire fuselage from station 434.5 onwards and the tail turret.
-Deck Turret: Martin uses this term, Dorsal Turret and Upper Rear Turret to refer to the Martin 250CE electric turret located at station 460.25.
-Tunnel Gun: Martin's term for the ventral gunner's position. The gunner fires a .30 cal (sometimes replaced with a .50 cal) out of the camera hatch which extends from station 512.25 to station 548.375. This gun position as well as the camera hatch were deleted from the B-26B-10-MA onward.
-Waist Guns: Also called Side Guns in early Martin drawings & documents, there were three or four main configurations:
Most if not all B-26-MA through B-26B-MA were modified with fittings for 2x .30 cal machine guns at station 499 1/4, firing through the camera side windows (which was located between stations 486 1/4 and 512 1/4), one on each side. B-26-MA crews were only provided with one gun to attach to either of these positions in the tunnel position, something the 22nd BG quickly remedied on their aircraft. These mounts were frequently upgraded to hold .50 cals in the field, with additional rectangular sighting windows and sometimes wind deflectors added. B-26Bs may have already come with waist guns, it's not 100% clear to me, or what caliber they were if they did.
The "B-26B-1" configuration was similar, with changes to the windows that allowed them to close with the guns in place, and with the now .50 cals being mounted slightly aft at station 500 11/16 on a new platform. The additional windows were now circular. There may have been another configuration with the old camera windows, it's hard to tell from photos. It's also hard to tell if the windows were enlarged or not. Sometimes it looks like the old windows were kept but are now part of a bigger removable hatch? This configuration can be seen on this 50 Hour Inspection instructional video using a B-26C-5-MO.
From the B-26B-10-MA & B-26C-10-MO onward the waist gun windows were moved aft (to between stations 512 1/4 and 548 3/8) and significantly enlarged, with new hatches that slid upwards on tracks. There was also a single circular sighting window above the waist gun hatches. I do not know the exact location of the gun mounts.
-Aft Fuselage: Martin's term for the assembly that extends from station 434.25 to station 581.375. Contains the deck turret and waist and/or tunnel gunner's compartment (depending on the model). The fin attaches to the top of this section.From the B-26B-10-MA & B-26C-10-MO onward the waist gun windows were moved aft (to between stations 512 1/4 and 548 3/8) and significantly enlarged, with new hatches that slid upwards on tracks. There was also a single circular sighting window above the waist gun hatches. I do not know the exact location of the gun mounts.
-Tail Section: Term I'll use for the assembly that extends from station 581.375 onwards. Contains the stabilizer's center section and the tail gunner's station.
-Fuselage Tail Cone: Removable endcap for the tail. Extends from station 693 to station 698.5 on B-26-MA & B-26A, or station 670.75 to station 698 on the B-26B. B-26B1s, Cs, Fs and Gs did not need tail cones.
Wing Group
-Center Wing: The section of the wing located inside the fuselage. The spars in this section are connected to station 230.75 and station 346.25 by shear webs and are straight and of constant section, perpendicular to the direction of flight when viewed from above. This section extends 46" from the fuselage centerline, to wing station 46.
-Outer Wing: The panel that makes up most of the wing. This section extends from station 46 to station 364 and can be divided into Nose Section, Main Wing Section and Trailing Section. The Nacelle and Wing Tip attach to this section.
-Wing Main Section: The section of the Outer Wing between the two wing spars, that the nose and trailing sections attach to. To this section attach the nose section, trailing section and landing gear.
-Wing Nose Section: The section of the Outer Wing forward of the forward spar, which is itself built of several smaller sections. Contains the landing lights, running light and deice boots (if fitted).
-Wing Trailing Section: The section of the Outer Wing aft of the rear spar, which is itself made of two sections. The inboard section contains the wing flaps, while the outboard holds the ailerons.
-Wing Tip: The section of the wing extending from station 364 onwards. It contains navigation lights and the pitot tube, as well as one of the aileron hinge brackets in the long wing models. Deice boots are also be attached to this section if installed.
Engine/Nacelle Group
-Nacelle: the term Martin uses to describe the entire nacelle assembly, including the engine hood. Stations are measured along the thrust line, with station 0 being the intersection of the centerline for the propeller blades.
-Engine Hood: the term Martin uses to describe the engine cowling. It is split into five (5) components: two (2) upper panels (which include the carburetor ducts), two (2) side panels and one (1) lower panel (which contains the oil cooler duct). Extends from station 6.6 to station 53.59 (for the upper panels) or station 54 (for the lower panel). These panels are attached to the engine via two mounting rings.
-Desert Cowlings: the term the B-26B manual uses for the engine hood upper panels fitted with enlarged air intakes to allow for installation of air filters. These were fitted to "B-26B-1s" and all production models from the B-3 to the G-25-MA.
-Venturi Cowl: the term Martin uses to describe the section of the nacelle aft of the engine hood and forward of the firewall (station 104.25), with holds the engine's accessories including the oil tank and oil cooler. It is split into five (6) panels: two (2) upper panels, two (2) center panels and two (2) lower panels. The two (2) fairings for the tailpipes are also a part of this unit and are located between the center panels and the lower panels. The upper panels extend from station 53.59 to station 103.65, the center panels from station 54 to station 114.74, and the lower panels from station 54 to station 103.65.
-Tailpipe: Martin's term for the exhaust stacks.
-Rear Nacelle: the term Martin uses to describe the assembly that extends from station 103.65 onwards. This section attaches to the wing outer panels and contains the landing gear doors.
-Nacelle Tail Cone: Martin's term for the removable endcap for the nacelles that extends from station 229.25 to station 262.16 on short wing models and from station 218.13 to station 262.16 on long wing models.
Skeleton
A WIP version of this is available here: B-26 Skeletons. See reply #12 for notes and instructions on it.
So, with that out of the way, what the hell is a B-26 Skeleton? Simple, it's what you get when you combine the smallest amount of information required to describe the airplane's geometry. For scale modeling, it's useful to figure out lengths and distances when modifying kits. For 3D modeling, it's a very helpful tool in order to accurately place all the subassemblies. These are still WIP but I plan on sharing the blender files for them once they are complete. Currently missing are the main landing gear, the nose gear doors and all other doors, the tail turrets, the wing flaps and the ailerons. I also have yet to add the arcs for the tips of the wings, stabilizer and fin. I also have yet to make a skeleton for the non-Quick Fix B1 & C or the B-26F & G, the latter two because I have very little information on then.
I will now use the skeletons as a visual aid to explain how the B-26's wings and empennage were enlarged. Black represents the B-26 and B-26B, while orange represents the B1/C Quick Fix. It's important to remember that Martin's priority was reusing as many components as possible, and keeping the attachment points the same.
First off, the wings. Martin kept the center wing and the wing main section's geometry the same, though the parts themselves were not kept. The nose and trailing sections were replaced with ones with longer chord at station 364. The new trailing section was significantly larger and responsible for the most noticeable change in the wing's shape. Since Martin had to redesign this section anyway, they switched from split flaps to slotted flaps as recommended by NACA. The old wing tip was replaced by a new unusually long unit which extended from station 364 to station 426. This made each wing 36" longer, for a total increase in span of 72" or 6'. Keeping the main section's contours meant the nacelles needed much less extensive redesign.
For the empennage, Martin had less constraints. As such, they essentially just extended the old units at the bottom. The fin and rudder grew 20", while each stabilizer and elevator grew 24.25".
While the old fin was held in place only by two bolts at the spar and a row of screws attaching its lowest rib directly to the skin of the upper fuselage, the new fin's lowest rib was now recessed and a new hinge bracket & bolt was attached to a bracket near the leading edge. As such, the fin now had three attachment points, wish the resulting skirt receiving a rubber strip at the interface with the fuselage. The lower section of the rudder was redesigned to still fit in the old fairing at the top of the tail section (note that the orange and black lines intersect at the bottom of the rudder trim tab's trailing edge). The main priority for Martin was keeping the rudder's attachment points the same, particularly the torque tube contained in the aft fuselage.
The theoretical rudder hinge's centerline was thus kept, while the fin spar and nose of the rudder gained a distinct break/angle in their lines. It's worth noting that with this change Martin also changed the datum for the fin's stations from a line tangent to the fuselage centerline to the theoretical base of the fin, which used to be station 34 (which was also the same between all models). So while the fin gained 20", one must subtract 14" from the short-wing B-26s' stations to find the corresponding stations and ribs on the long wing models. Most of the fin's ribs were reused.
The Stabilizer was trickier to modify because three mounting points had to be kept: the front spar, the rear spar and the elevator torque tube. Martin also wanted to avoid reshaping the fuselage frames entirely if possible. The solution was an extension that had constant section between the two spars, with only the nose ribs tapering. The elevator was a much easier affair, with Martin extending its bottom and then simply "cutting" (reshaping) the ends of the trim tabs so that they lined up with the pre-existing fillet from the B-26B. A new fillet and the two bulkheads that held the stabilizer's spars were some of the very few changes made to this section.
B-26B Tail (note that the angled/cut section ends at the elevator):
B-26B1 "Quick Fix" Tail (angled/cut section continues into the elevator, rounding off into the trailing edge with an arc of radius 5"):
Hope y'all find this informative!
-Matt
Edit: Revised 5 December 2024 to correct information on sharp nose ailerons, as per post #18.
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