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Guillows Series 800 - Bell P 39D Airacobra Blown to 70"
This is a DISCONTINUED Kit.

[IMAGE The Bell P-39 Airacobra was one of the principal American fighter aircraft in service at the start of World War II. Although its mid-engine placement was innovative, the P-39 design was handicapped by the lack of an efficient turbo-supercharger, limiting it to low-altitude work. The P-39 was used with great success by the Soviet Air Force, who scored the highest number of individual kills attributed to any U.S. fighter type. Other important users were the Free French and co-belligerent Italian air forces.[3] Together with the derivative P-63 Kingcobra, these aircraft became the most successful mass-produced fixed-wing aircraft manufactured by Bell.[4]

The main purpose of this configuration was to free up space for the heavy main armament, a 37 mm (1.46 in) Oldsmobile T9 cannon firing through the center of the propeller hub for optimum accuracy and stability when firing. In fact, the entire design was made to accommodate this gun in the aircraft.[10] This happened because H.M. Poyer, designer for project leader Robert Woods, was impressed by the power of this weapon and he pressed for its incorporation though the original concept had been a 20–25 mm (.79–98 in) cannon mounted in a conventional manner in the nose. This was unusual, because fighters had previously been designed around an engine, not a weapon system. Although devastating when it worked, the T9 had very limited ammunition, a low rate of fire, and was prone to jamming.[11]

As originally designed, the XP-39 had a turbocharger with a scoop on the left side of the fuselage;[12] both were deleted for production.[13] The production P-39 retained a single-stage, single-speed supercharger with a critical altitude (above which performance declined) of about 12,000 ft (3,658 m).[14]

After completing service trials, and originally designated P-45, a first order for 80 aircraft was placed 10 August 1939; the designation would revert before deliveries began.[15]

The Airacobra was one of the first production fighters to be conceived as a "weapons system"; in this case the aircraft (known originally as the Bell Model 4) was designed around the 37mm T9 cannon.[19] This weapon, which was designed in 1934 by the American Armament Corporation, a division of Oldsmobile, fired a 1.3 lb (610 g) projectile capable of piercing .8 in (2 cm) of armor at 500 yd (450 m) with armor piercing rounds. The 200 lb, 90 inch long weapon had to be rigidly mounted and fire parallel to and close to the centerline of the new fighter; however, it would be impossible to mount the weapon in the fuselage, firing through the propeller shaft as could be done with smaller 20mm cannon. Weight, balance and visibility problems meant that the cockpit could not be placed farther back in the fuselage, behind the engine and cannon.[19] The solution adopted was to mount the cannon in the forward fuselage and the engine in the center fuselage, directly behind the pilot's seat. The tractor propeller was driven via a 10 foot long drive shaft which was made in two sections, incorporating a self-aligning bearing to accommodate fuselage deflection during violent maneuvers. This shaft ran through a tunnel in the cockpit floor and was connected to a gearbox in the nose of the fuselage which, in turn, drove the three or (later) four bladed propeller via a short central shaft. The gearbox was provided with its own lubrication system, separate from the engine; in later versions of the Airacobra the gearbox was provided with some armor protection.[19] The glycol cooled radiator was fitted in the wing center-section, immediately beneath the engine; this was flanked on either side by a single drum shaped oil cooler. Air for the radiator and oil coolers was drawn in through intakes formed in both wing-root leading edges and was directed via four ducts to the radiator faces. The air was then exhausted through three controllable hinged flaps near the trailing edge of the center section. Air for the carburettor was drawn in via a raised oval intake immediately aft of the rear canopy.[20][21]

Because the pilot was riding above the extension shaft he was placed higher in the fuselage than most contemporary fighters, which, in turn, allowed Bell to use a raised cockpit enclosure, giving the pilot a good field of view.[19] Access to the cockpit was via sideways opening "car doors", one on either side. Both had wind-down windows; because only the right hand door had a handle both inside and outside this was used as the normal means of access. The left hand door could only be opened from the outside and was only for emergency use, although both doors could be jettisoned. In operational service, however the cockpit was difficult to escape from in an emergency because the roof was fixed.[25]

Because of the unconventional layout, there was no space in the fuselage to place a fuel tank. Although drop tanks were implemented to extend its range, the standard fuel load was carried in the wings, with the result that the P-39 was limited to short range tactical strikes.[26]

[IMAGE In September 1940, Britain ordered 386 P-39Ds (Model 14), with a 20 mm (.79 in) Hispano-Suiza HS.404 and six .303 in (7.7 mm), instead of a 37 mm (1.46 in) cannon and six 0.30 in (7.62 in) guns. The RAF eventually ordered a total of 675 P-39s. However, after the first Airacobras arrived at 601 Squadron RAF in September 1941, they were promptly recognized as having an inadequate rate of climb and performance at altitude for Western European conditions. Only 80 were adopted, all of them with 601 Squadron. Britain transferred about 200 P-39s to the Soviet Union.

A heavy structure, and around 265 lb (120 kg) of armor were characteristic of this aircraft as well. The production P-39's heavier weight combined with the Allison engine having only a single-stage, single-speed supercharger, limited the high-altitude capabilities of the fighter. The P-39's altitude performance was markedly inferior to the contemporary European fighters and, as a result, the first USAAF fighter units in the European Theater were equipped with the Spitfire V. However, the P-39D's roll rate was 75°/s at 235 mph (378 km/h)– better than the A6M2, F4F, F6F, or P-38 up to 265 mph (426 km/h). (see NACA chart).[28]

The weight distribution of the P-39 was supposedly the reason for its tendency to enter a dangerous flat spin, a characteristic Soviet test pilots were able to demonstrate to the skeptical manufacturer who had been unable to reproduce the effect. After extensive tests, it was determined the spin could only be induced if the aircraft was improperly loaded, with no ammunition in the front compartment. The flight manual specifically noted a need to ballast the front ammunition compartment with the appropriate weight of shell casings to achieve a reasonable center of gravity. High speed controls were light, consequently, high speed turns and pull-outs were possible. However, the P-39 had to be held in a dive since it tended to level out, reminiscent of the Spitfire. Recommended dive speed limit (Vne) was 475 mph (764 km/h) for the P-39.[29]

By the time of the Pearl Harbor attack, nearly 600 had been built.

Trials of a laminar flow wing (in the XP-39E) and Continental IV-1430 engine (the P-76) were unsuccessful.[15] The mid-engine, gun-through-hub concept was developed further in the Bell P-63 Kingcobra.

The Airacobra saw combat throughout the world, particularly in the Southwest Pacific, Mediterranean and Russian theaters. Because its engine was not equipped with a supercharger, the P-39 performed best below 17,000 feet (5,200 m) altitude. It often was used at lower altitudes for such missions as ground strafing. Russian pilots appreciated the cannon-armed P-39 primarily for its air-to-air attack capability.

The British export models were renamed "Airacobra" in 1941. A further 150 were specified for delivery under Lend-lease in 1941 but these were not supplied. The Royal Air Force (RAF) took delivery in mid 1941 and found that actual performance of the non-turbo-supercharged production aircraft differed markedly from what they were expecting.[32] In some areas, the Airacobra was inferior to existing aircraft such as the Hawker Hurricane and Supermarine Spitfire and its performance at altitude suffered drastically. On the other hand it was considered effective for low level fighter and ground attack work. Problems with gun and exhaust flash suppression and compass were fixable.

[IMAGE No. 601 Squadron RAF was the only British unit to use the Airacobra operationally, receiving their first two examples on 6 August 1941. On 9 October, four Airacobras attacked enemy barges near Dunkirk, in the type's only operational action with the RAF. The squadron continued to train with the Airacobra during the winter, but a combination of poor serviceability and deep distrust of this unfamiliar fighter resulted in the RAF rejecting the type after one combat mission.[3] In March 1942, the unit re-equipped with Spitfires.

The United States requisitioned 200 of the next part of the order as the P-400. The P-400 designation came from advertised top speed of 400 mph (644 km/h). After Pearl Harbor, the P-400 was deployed to training units, but some saw combat in the Southwest Pacific including with the Cactus Air Force in the Battle of Guadalcanal.[35] Though outclassed by Japanese fighter planes, it performed well in strafing and bombing runs, often proving deadly in ground attacks on Japanese forces trying to retake Henderson Field. Guns salvaged from P-39s were sometimes fitted to Navy PT boats to increase firepower.[36]

In North Africa, the Tuskegee Airmen were assigned P-39s in February 1944. They successfully transitioned and carried out their duties including supporting Operation Shingle over Anzio as well as missions over the Gulf of Naples in the Airacobra but achieved few aerial victories.[37] By June they had transitioned to P-47 Thunderbolts and then P-51 Mustangs in July 1944.

The most successful use of the P-39 was in the hands of the Soviet Air Force (VVS). The tactical environment of the Eastern Front did not demand the extreme high-altitude operations that the RAF and United States Army Air Forces (USAAF) employed with their big bombers. The low-speed, low-altitude turning nature of most air combat on the Russian Front suited the P-39's strengths: sturdy construction, reliable radio gear, and adequate firepower. The usual nickname for the well-loved Airacobra in the VVS was Kobrushka, "little cobra", or Kobrastochka, a portmanteau of Kobra and Lastochka (swallow), "dear little cobra".[39][40] Soviet pilot Nikolai G. Golodnikov, in an interview with Andrei Sukhrukov, recalled:

The first “Soviet” Cobras had a 20 mm Hispano-Suiza cannon and two heavy Browning machine guns, synchronized and mounted in the nose. Later, Cobras arrived with the M-4 37 mm cannon and four machine guns, two synchronized and two wing-mounted. "We immediately removed the wing machine guns, leaving one cannon and two machine guns," Golodnikov recalled later.[41] That modification improved roll rate by reducing rotational inertia. Soviet airmen appreciated the M-4 cannon with its powerful rounds and the reliable action but complained about the low rate of fire (three rounds per second) and inadequate ammunition storage (only 30 rounds).[41] The Soviets used the Airacobra primarily for air-to-air combat[42] against a variety of German aircraft, including Messerschmitt Bf 109s, Focke-Wulf Fw 190s, Junkers Ju 87s, and Ju 88s.

Grigori Rechkalov, second Soviet top-scoring ace (56 individual air victories plus 5 shared) occasionally his wingman while both in 16.Gv.IAP [45], scored 44 victories flying Airacobras. The majority of his kills were achieved on P-39N-0 number 42-8747 and P-39Q-15 number 44-2547. During the Great Patriotic War he was awarded with the Order of Lenin, the Order of the Red Banner (four times), the Order of Alexandr Nievskii, the Order of Patriotic War 1st Class and the Order of the Red Star (twice). [46] This is the highest score ever gained by any pilot with any U.S.-made aircraft.

A total of 4,719 P-39s were sent to the Soviet Union, accounting for more than one-third of all U.S. and UK-supplied fighter aircraft in the VVS, and nearly half of all P-39 production.[48]

The Build: CLICK IMAGES TO ENLARGE...

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First, you have to get your plans blown.

Cut your plan (download is 12.8 meg, and is print ready for 1:1 plan 28" wingspan) into 8.5 by 11 inch sections, and scan each section front and back at 216 dpi. (any larger is ridiculous) Then, using The Castle's Split Image Software cut each scan 3 by 3 or into 9 sections. Then the images will need to be printed, then the individual printed copies will be re-assembled, much like a jigsaw puzzle. Be sure to have plenty of clear tape on hand. I've found that a paper cutter comes in very handy, but a pair of scissors will get the job done for trimming the individual images as needed to make them fit your puzzle/plan. HINT: Cut each printed image on the top and left sde only.

Actual wingspan is 68 1/2 inches, and will be slightly shorter once the wing dihedral is added. The horizontal tail feather will come in at 26 inches.

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The vertical tailfeather will be 14 inches long, and about the same height. Note that not all the scanned images need to be split, and printed. Many portions of the plan are not relevant to the project. For example, all the U-Control parts installations information can be ommitted, as it'd take a Chevy small block motor with a 3/4 race cam shaft to get this thing in the air. The fuselage will come in a 60 inches in length.

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On the Guillow's plans, you'll find virtually every part you'll need, but you'd better study the plan for a while and make sure. The scariest part of blowing these planes up is the lack of the plastic parts that come with the kit. You get to make all of these parts by whatever means you think of. The way we do it, is to make all the nose cowl, and canopy parts be part of the fuselage, and cover them with fabric as you would a normal kit with tissue.

From the full sized side view of the plan, you'll be able to trace off all the parts that are not templated. On this kit originally, many parts are card stock, which won't do at all on this large plane, so they'll all be made in 1/4" plywood. Gear doors are an example. The canopy out line, as well as the nose cowl, are traced so that they can be transferred to the fuselage plan layout.

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Cut out your traced nose, and carefully tape it to the fuse layout. Do the same with your canopy. The former parts detail has also been drafted onto the canopy tracing, so as to help with parts placement. The new portions of the plan hide some details so I don't want to be hunting around for answers during the build. A quick note: I don't build and utilaze the Guillow's side keel on the lage planes. It's complicated to make great big long skinny two piece parts that come out anywhere near straight. It's also hard to cut the deep slots in the fuse formers to fit the side keel. I simply use a longeron instead. As the longerons are screwed down and glued, there's planty of structural integrity to hold it all together.

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The checklist is your best friend. Nuff said. The checklist comes in handy in describing parts modifications like B4, B5, and B6. All three of these fuse formers will have a great deal to do with how your canopy turns out. You get to be creative, and decide what your canopy cross section looks like. I'm pulling for you! Once you're good, you'll want to laminate all your parts templates with clear packing tape, then cut all the parts out with scissors. I like to mark all the templates with number required, part number, what material to cut them out of, etc...

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Once finished cutting out all of your templates, lay them out on your plans layout to take inventory of what you may have missed. THIS AIN'T A KIT... PAY ATTENTION TO DETAILS... Next, start laying out your parts on the plywood. I'm using 1/4 for all formers, wing trailing edge, and for all fuselage keel parts. 1/4 for vertical and horizontal stab parts, and used 1/2 quarter round molding for the wing leading edge. You could use balsa, but when we built the F6F we used balsa and spent a gruntload of money.

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Pictured here is about $9 worth of plywood. About 5% the cost of balsa. Pick out your plywood carefully down at the Loews Handy Depot, as you can get some plywood that's real pretty on one side and fug bugly on the other side. Careful choices will get you good and decent if you take the time. I use a Skil Saw and a Ryobi Dagger Saw to get the parts out of the large sheets. Then, the Ryobi Scroll Saw helps with the finer detail work.

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A Ryobi Table Top Sander is probably the most important tool we have. Couldn't do the project without her... I use a Sears Band Saw to cut out the parts. Works good. Once you have all the parts roughed out, you can actually begin the project.

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Fuse formers before.... And after blue printing... Wing formers before....

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And after... And, the rest of the parts. Next, we'll start laying out the fuse, and wing, and begin cutting former notches...

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This will be the first oportunity to see if the parts fit the plan. I've recently replaced my old bench sander with a new Ryobi model, and it seems that it's going to work just fine. It doesn't sound like a threshing machine either. A definate plus. When you're building with balsa, you get to stick pins thru your parts into your workboard and hold everything down nice and tight. This ain't an option with plywood. So, why not get rid of the workboard as well? I'm lucky to have some old folding tables around, and nobody cares if I get glue on them, so I can work diectly onto the table's surface. Put the plan down, tape it with blue tape, put down waxed paper, tape that down too. Then I actually glue the parts to the waxed paper to keep them from sliding around.The waxed paper peels off real nice when you're done.

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I hold the parts down flat as possible with anything I can find. Yes, that's a rock. Yes, that's a 2 pound hammer. I'll have evry pair of pliers in the garage on the table shortly. I used to always put the bottom stringers for the wing down on the plan first. Why? Because that's the way I was taught to do it when new at this 45+ years ago... I read the destructions recently that came with one of the kits, and it said to do em after you build the wing. Gusess what? It works better. Oddly enough, the parts are all fitting better than ever. Either I'm getting better at it, or that new sander is something to behold...

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Pliers, pipe wrench. hammer. rock, clamps.... Hold her down anyway you can, till the glue dries.

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Once you can get the leading edges on the wing, the L1 parts and side keels on the fuse, you're getting closer to picking your parts up off the plan, and getting rid of the waxed paper.

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Put a little dihedral in that wing, young man! A little.... 5 1/4 inches...

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Start putting some formers on the other sde of the fuse, and we'll be well on our way to watching some glue dry!

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Or we could start working on the tail feathers... And do the first mock-up...

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One of my favorite inovations. Hardpoints. Okay so you have your plane hung up on the ceiling out of everybuddy's way... You take her down to fly her, and all goes well. So you bring her back and leave her sitting on the bench because it's a pain to hang her back up on the ceiling. No wait! You installed hardpoints top and bottom on your bird! Good for you! Now it takes seconds to re-hang the plane. Ain't you smart? When we're dealing with these big boys, it's good to have something to hook up to when hanging the plane. Your rope or chain will leave marks on the plane after some time has passed, and we don't want that. The front landing gear strut took three 1/4" nut bolt combos to keep it stiff. Wish I could have used 10. This plane is going to be tail heavy so any weight I can get in the nose will help it sit on it's landing gear properly. Remeber this is a static, non-flying plane, so balancing it for flight is not what I'm looking for. Just want it to sit on all three tires properly...

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Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws...

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Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws... Stringers and screws...

And... after two days... The fuse is ready for the tail parts...

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Tail feathers... check! Main Gear... check!

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Tail parts... check! Cosmetic parts for top of fuse next to air scoop... check!

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Wing... check! Second mock up... check!

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This one has gone together as straight as any we've done.

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Let's get us a propellor built....

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And start covering...

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NEXT:

still thinking on it... stand by......

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