Specifications: Motor: speed 400, 6 V Wingspan: 692 mm Length: 540 mm. Number of cells: 7-8 600AE/500AR Prop: Graupner 6x4 Weight: around 500-520 gr. Main sources: Books: Hasse Wind, Hävittäjälentäjä, Börje Sjögren, Suomen ilmavoimien historia 1, Brewster B-239 ja Humu, Kalevi Keskinen, 1970 Tampere Magazines: Pienoismalli, 2/89, Pentti Manninen Top : By Subject : Construction The Brewster Model 239 -------------------------------------------------------------------------------- Author: Marko Terava Browse articles by Marko Terava Hits: 1713 Rating: 8.53 Votes: 15 ---12345678910 (10 is best) Specifications: Motor: speed 400, 6 V Wingspan: 692 mm Length: 540 mm. Number of cells: 7-8 600AE/500AR Prop: Graupner 6x4 Weight: around 500-520 gr. Main sources: Books: Hasse Wind, Hävittäjälentäjä, Börje Sjögren, Suomen ilmavoimien historia 1, Brewster B-239 ja Humu, Kalevi Keskinen, 1970 Tampere Magazines: Pienoismalli, 2/89, Pentti Manninen Internet: http://www.airspacemag.com/ASM/Mag/Index/1996/JJ/ssbb.html http://www.danford.net/aahs.html http://www.danford.net/faf..html "[T]here were a small number of pilots who achieved notable success with the Buffalo and who might argue that the Buffalo was, in reality, a revolutionary aircraft which narrowly missed an opportunity for greatness." Background Brewster's little fighter is a controversial aircraft. The Brewster remains largely unknown to general aviation public. This is probably caused primarily by the lack of success in countries other than Finland. The Brewster was even voted by a group of Internet aviation fans for the worst fighter of World War II. It is also mentioned in two books that are titled The World's Worst Aircraft. The Buffalo is the only fighter from any era to have a chapter in both of them. As is often the case, the truth isn’t so straightforward. Finnish pilots were able to achieve good results with the Brewster. Coupled with mature tactics and well trained Finnish pilots, the results were convincing. Over 490 air-to-air victories were credited to Finnish Brewster pilots. This is a lot considering that there were only 44 planes to begin with. With one particular plane (BW-393), an amazing 41 aerial victories were achieved! Of course, the Brewster wasn’t the only factor here, but it was a significant one. The guys who flew the Brewster Model 239 here in Finland liked their ride. One of them was former squadron leader Joppe Karhunen: "The more we played with it, the more we liked it". He and other wartime pilots felt that it was indeed a very good plane. The Brewster could turn on a dime, and in the early days of the war it was also considered to be pretty fast against the Russian fighters. It had no nasty stall characteristics, it behaved nicely during landing, and the takeoff was easy with its wide landing gear. After all, this plane was designed for aircraft carrier use. It had a reliable engine which, when properly maintained, never let its pilot down. The Brewster also had exceptionally good range – it could remain airborne up to four hours. It had heavy armament, which was effective against the enemy aircraft. All in all, it was a good and reliable war machine and the pilots felt good about it. Development and production There is a lot of documented information available about the Brewster fighters. Some of this information is contradictory. I have tried to filter out the faulty information and include only what is true. Making a good fighter, or any airplane for that matter, has always been difficult. Many excellent planes were not successful with the first attempt. More tests and more prototypes were required before the engineers "got it right". Many airplanes have had numerous versions during the entire history of the model. Sometimes the last production model was very different from the first one. The Brewster fighter was not an exception. There were three main variants of Brewster. These were Models 139, 239, and 339. Only the last variant was called the Brewster Buffalo. All these Brewsters looked pretty much the same. However, there were real differences between these three variations. This partly explains the varying success when Brewster fighters entered frontline service during the war in various parts of the globe. In the mid 1930's the U.S. Navy presented a design request for a new carrier-based plane. Around that time the Brewster factory had finished the XSBA-1 divebomber, which saw its maiden flight in 1936. This plane has a lot of similarity to later Brewsters. This was natural because Brewster had already started building the Model 139 before the Navy presented its request. Brewster's planes had all-metal structure, a mid-wing, retracting undercarriage, hydraulic systems, and so on. This was all very new to the U.S Navy. Because the airplane functioned well enough, the Naval Aircraft Factory built 30 more of those divebombers. For the fighter competition the Navy received responses from Grumman, Seversky, and Brewster. Brewster's design was chosen. The Navy gave this project the name XF2A-1. F=fighter, A=factory=Brewster, 2=second fighter from the factory in series A, -1=first modification from basic model F2A. Brewster called the planes:Brewster Models 139, 239 and 339, whereas the Navy called these planes F2A-1, F2A-2, and F2A-3 respectively. The Brewster Model 139 saw its maiden flight on December 2nd, 1937 with Melvin Gough at the sticks. This handmade prototype was delivered to the Navy for test flights in January, 1938. During these tests a few deficiencies were revealed. The biggest problem was the considerably lower than promised top speed. Modifications were required to the cowling and to the rivets, which were changed. With these modifications Brewster now had a top speed of 480 km/hr. Test flights continued on with this newly-built prototype, and the Navy accepted Brewster Model 139 into production with the designation X2A-1. In June the Navy placed an order for 54 planes. At this point the Model 139 was still a significantly different plane than the one which came off the production line in 1939. It was this part of the production batch which later became the Finnish Brewster. The most visible difference was the lower cockpit canopy. So much so that normal-sized pilots had difficulty sitting comfortably and still seeing well in all directions. The Brewster factory was not well suited for mass production, and production began at slow pace. Nevertheless, the first 11 planes (139’s) coming off the production line were ready for the Navy by December, 1939. The official date for the F2A-1 entering service was December 8th, 1939. The U.S Navy VF-3 got it's first plane then, and by mid December the aircraft carrier USS Saratoga had 9 planes. This had historical significance as these Brewsters were the U.S Navy's first carrier-based monoplanes in operational service. These 11 planes were the only Model 139's that the U.S Navy got. The remaining 43 planes (not yet ready) were left to Brewster Aeronautical. There were many reasons for this, but mostly because the planes were delayed and were already seen as out-dated. Brewster had also already offered the Navy a new, improved Model 339. So the Finnish government got a chance to buy the remaining planes. The remaining planes were modified. All Navy equipment was removed: carrier equipment, guns and aiming devices, and all gauges. Engines had to be switched to an export model which was approved for selling abroad. Wright Cyclone nine cylinder radial engines (1820G-5) were installed (the 1820 is the same engine that powered, among other things, DC-3’s and B-17 bombers). It’s worth noting that these stripped-down planes were now labeled as Brewster Model 239’s. Finnish Brewsters were very close to the first 11 Model 139’s that the Navy got. Here in Finland the planes saw some alterations as well. Most visible: the small tailwheel was replaced with a bigger one (more suitable for dirt strips), armor plate was added behind the pilot, and engines received filters because dust was wearing engines out prematurely. Missed opportunity In the mean time the U.S navy received quite a few Brewsters. The Navy primarily received Model 339’s, which later earned a very bad reputation among pilots in the Pacific theater. The Model 339 was significantly heavier than the version that saw service here in Finland. Heavy weight resulted from the more powerful Wright Cyclone engine, bigger fuel tanks, and other changes which were made to the plane. Though the added horsepower did result in a slightly faster top speed, the plane's overall performance was greatly reduced. Most importantly, the Brewster’s strong side - agility - wasn’t there anymore. The Brewster had lost its strength. What had been a very enjoyable plane to fly became a sitting duck when compared to the very agile Japanese Zeros. Had the U.S Navy received the planes that Finland got, the Brewster might very well have had a different tune in wartime pilot stories. There were small number of U.S pilots who got to enjoy of the original Model 139’s flying qualities. Those that did fly the Model 139 thought it was a great plane, just like Finnish pilots. But the new "improved" version (339) pretty much seemed to get their undivided dislike. You might want to see how Pappy Boyington described the differences between these two versions. He doesn’t sugarcoat it! http://www.danford.net/pappy.htm Building sp400 Brewster I can still remember when I first wanted to build a model Brewster. I was about 14 at the time, a rather long time ago. There was a library in my school which had the memoirs of Hasse Wind. He was one of the top aces in the FAF during the W.W.II. I took the book home and learned how Finnish W.W.II pilots used this strange looking plane nicknamed Butt-Walter. It’s imposing shape was the reason behind this nickname, and indeed the plane looked a little awkward. To me it looked really fascinating, and I could almost feel myself behind the stick. But at that time the Brewster didn’t seem like an easy plane to model and fly. It had short moments and a draggy fuselage, so I kept away from it. But it was confusing to think that a model Brewster wouldn’t fly well when its real life counterpart was such a success. But then Jim Ryan’s Speed 400 fighter designs began to appear. Many of these were short, stubby fighters which were equipped with big, fat radial engines. This electric approach to such planes seemed to offer a very low-risk opportunity to make a flyable Brewster. I took a long,hard look on Jim’s designs and thought it would be relatively simple matter to merely give these designs new clothing: Brewster shapes! This line of thinking proved to be correct: it turned out to be a simple task. As an aviation-oriented person from Finland, I would like to think that I was doing a Brewster Model 239. But if you have a warm spot for Brewster Buffalo Model 339, this plane is practically no different than that. Construction Just like Jim’s planes - this plane is not for beginners; instead, it requires intermediate skills in both building and flying. If you have these skills, you will be able to figure out the steps that aren’t described here. I’ve tried to describe things that might be otherwise difficult to figure out. Previously I have had some twisted fuselages, and I knew that if I weren’t careful that could easily happen here too. So you need to make a crutch. Once that is done, the rest is easy. I ended up with a straight fuselage right away. Crutch The crutch is simply a straight, smooth piece of wood. It needs to be long enough and wide enough so that your fuselage will fit entirely on top of it. Take a straightedge and draw a centerline on the crutch, and then draw the markings for the fuselage formers at a 90 degree angle on that centerline. After that you need some scrap pieces of rather thick balsa. Something like 10mm x 10mm will do nicely. Make sure that those pieces are square. The idea is to make tight slots for your fuselage formers. The slots must not be too wide, as you need to be able to have your fuselage sides pressed against the formers. You will get the distance between each slot from the side view of the fuselage. First glue the other side of the slot and then place some 1.6 mm balsa against it (to imitate the former) and press the other slot side against the fuselage former tightly. Then apply a little CA under your slot wood and your slot is ready. Make the rest of the slots similarly, and make sure the slots are tight, straight, and with correct spacing with each other. Be careful and do not glue that 1.6 mm balsa there. Wood selection Wood selection in a plane like this is important. Take your time when you pick the balsa for this plane, it will be worth it. You should only use soft or medium balsa. There are only few spots in the plane where you need any extra strength – so save weight. Fuselage formers The idea is to build the upper and lower parts of the fuselage separately and then join them. For this reason the formers have a split line shown. This way your fuselage sides will fit exactly when you are joining them. Be sure to cut your formers first as a whole and then shape them to final form. Now you can cut them in half. Formers are made of 1.6 mm balsa. Make sure your grain direction is correct, otherwise those formers will not have the needed strength and will just break under pressure. The grain direction is marked on the plans. After all the slots are ready, they should be pretty tight. You should be able to have your formers placed between them with only friction. But if you made some loose slots, you can pin your fuselage former down, with the pin going through the slots and the former. Remember to remove your pins before your fuselage is completely covered with balsa! The upper and lower part of the fuselage are constructed similarly. Fuselage sides are from 1.6 mm balsa. Here it is important to choose balsa sheet which bends easily. Once you have placed your formers in the crutch, you can start attaching your fuselage sides to the formers. Hold the sides with your hand in place while you apply small amounts of CA to the joints. The supplied templates for the fuselage sides provide most of the sheeting for the fuselage. You will need to cut more of your own strips to fully sheet the fuselage. If you have a problem bending your sheeting, try using narrower strips. Start gluing your fuselage sides from the bottom up. Once again, make sure your center line markings on the crutch and formers are aligned. If they are not, your life will be difficult when it’s time to join the upper and lower parts. Once you have made the upper and lower parts of the fuselage, you can join them. Upper and lower parts should have a pretty good fit with each other from the start. But if you have some small cracks between the parts, you can make it better with some sandpaper. Place some smooth sandpaper on a flat surface. Carefully and slowly sand your fuselage halves on top of it. This way you can make the fit better. I only needed CA for joining upper and lower parts together. Cowling You can make your cowling two ways. You could use a suitable block of balsa, with a big round hole bored into it. You would then just glue the engine former in place and then shape the cowling accordingly. But for me the problem was that I didn’t either have a suitable chunk of balsa or a suitably large drill. So I had to resort to a different method. I used tunafish can, but any suitably-sized round object will do. I had some scrap balsa sheets of 1.6 mm thickness. These were leftovers from previous projects and were no good for anything else. I took a straightedge and cut about 6 cm wide strips from those sheets. It’s good to have some excess width so that you can later sand the cowling straight. It’s very important that you cut your strips so that the wood grain is in the right direction. You need strips that curve well. The idea is to laminate layers of balsa with CA on top of that round object. So you need to cut them in almost a 90 degree angle to the grain. It is important to get the wood grains to cross each other between layers. So cut your balsa strips with a slight angle against the grains. A 10-15 degree angle is fine. With that the strips will still curve well enough and you can make the grains cross each other between different layers. After you have cut a bunch of strips, start laying them against can. It’s good to have some thin plastic around the can to prevent the wood from sticking to the can. You can wet the balsa if it’s too tough, but you probably won’t need that. Use your hands and rubber bands to keep the balsa rolled over. After you have added the first roll of balsa, use CA to glue the sheet edges together. Use something plastic around your can – it will prevent the wood from being glued to it. You might get frustrated here a bit, because the first rounds of balsa likes to break and fall out of place, but be patient. Add a second layer and now try to make the wood grains gross each other. If you have your wood grains crossing each other they will form a sort of "balsa veneer". Use your hands and rubber bands to keep that fledgling cowling from exploding apart. After you’ve got about two layers of balsa the cowling starts to keep itself together. But if you take it off the mold, it probably won’t keep its form, so add a third layer. After that you will probably be able to add more layers, while holding the round cowling in your hand. I also added some layers inside the cowling as the tuna can diameter was a little too big . At least one layer is needed inside for the engine former. The inner layer will make a suitable ridge for that former. After some 4-6 layers the cowling is really strong. Now you can tape some rough sandpaper on your building board and sand that cowling to the right size. Your cowling will be almost as light as if it were made from a solid block. My finished cowling weighed somewhere between 5-10 grams. This approach will help you if you don’t happen to have a suitable block of balsa with a round hole in it. The downside is that you will have to go through some extra trouble. It took me about 1 hour to make it this way. You will also have to go through some extra trouble later in the building process when you shape your motor former. The hole inside the cowling isn’t exactly round. Tail cone Take a piece of balsa and carve it to the approximate shape. Before you glue it in place hollow it out as much as you can. After you have glued it in place, you can take a file or sandpaper and follow the curvature of the fuselage and shape the rest of it. The Brewster's tail cone was very blunt. Wing This is a typical foam wing, with 0.8 mm balsa sheeting. Nothing unusual about it. The wing uses about a 9.5% thick SD 5060 airfoil both in the root and in the tip. I used 1% washout. I was very satisfied with the Brewster's stall qualities. Using excess washout will not benefit you – it will only create more drag and increase your landing speeds. When you join the wing panels add some fiberglass to the center. Add your choice of torque rods for the ailerons. I made mine using 1.5 mm music wire. I used some old Sullivan pushrods to have some tubes for it. I used CA-joints for the ailerons. The formers shown in the plans for the bellypan are meant to be as accurate as possible. However, you will have to adjust them a little when you make your belly pan. It’s best to have your wing bolted to the fuselage when you make final adjustments to those formers. This way your belly ban will follow correctly the rest of the fuselage. Notice the reinforcement around the bolt. It’s made from 0.8 mm plywood. Wing tips are formed as follows. When you sheet your wings, make sure you don’t sheet the wing all the way to the tip. Instead, leave the bottom bare from where it’s supposed to start rounding. After you have your partially sheeted wing, cut your wingtips in their round shapes. Then use either your hotwire or a sharp knife to remove excess foam from the bottom wingtip. After you have beveled your wingtip, add your 0.8 mm balsa there. In the event of a crash, the wing is strengthened around the critical area of the wingbolt. The wing hold-down plate in the fuselage is pretty small. It’s like that for a reason. It will carry flight loads, but if you crash your wing will break loose from the fuselage, saving you some extra work. It’s easier to glue back the wing-hold-down plate than it is to fix a wing. Any plane of this size is too brittle to break the nylon bolt anyway. In the picture you can see radio installation and the plywood plate that holds the wing in place. Elevator and rudder The stabilizer, elevator, vertical fin, and rudder are simply cut from sheet stock. Canopy No Brewster looks like a Brewster without the "glasshouse". Form your plug by using the guides shown in the plans. I won’t cover this more thoroughly. You need to know how to either vacuum form canopies, or how to stretch form them. I did mine by stretching. Instead of painting the canopy lines, I used iron on covering. CG The CG is marked on the plans. I haven’t made any testing with other CG locations as I’ve been perfectly satisfied with it as is. Elevator pushrod The elevator pushrod is made of 1 mm music wire. Sharpen one end of the wire and punch it through the finished fuselage, then make a Z-bend on the end. Surface throws I used pretty large movements. These figures are conservative: Elevator: 5-7 mm up/down Ailerons: 5-7 mm up/down With these settings your Brewster will maneuver, but it won’t be overly aggressive. I suggest you use some exponential on the elevator. It’s pretty touchy around the center. Ailerons are effective and they remain like that through the entire speed envelope. Flying the Brewster The first launch was easy. My club friend from Tampere RC flyers (Tampereen RC-Lentäjät) lent me his arm and off it went. After the Brewster cleared his hand, it hardly lost any altitude. I only needed some minor trim changes. Flying the Brewster is interesting. It’s a plane that needs to be flown. It’s a pilots plane. You can’t make mistakes and then fix it with huge power reserves or reservoirs of wing area. You need to be alert and watch your momentum. If you lose your airspeed it will take a couple of seconds before that S400 will rescue you. On turns don’t use too much up elevator. The Brewster can start flying at a nose high attitude before you know it. It will then become a slightly disoriented bee if that happens. If you keep the nose down on turns you will notice that it will still maintain altitude quite nicely. The Brewster is short coupled. This is especially evident with elevator usage. If you try to loop the Brewster by applying full up elevator, it will not do it. Remember this is no trainer - it requires flying! Instead it will start flying uphill and when it get’s its nose up, the speed dies and it will just fall downwards. Making good looking loops requires couple things: a pretty fresh charge (on 7-cells), a little dive, and careful elevator usage - first a little, and when the nose is up, then the rest. Watch out when you try your first loops: be sure you have plenty of altitude, at least a couple of tree heights. The first loop I tried on the first flight was very l-shaped, and I found myself on the deck with about half a meter to spare before I got it straightened out. I haven’t had problems since then. You just need to know what to expect! My club friend Simo made a Brewster too. Simo is on the left and I’m on the right. Formation flying with these two Brewsters is not too easy, but it is rewarding. High speed The Brewster moves briskly with full throttle. The calculated pitch speed on the prop is around 50 mph / 80 km/h, with 7 cells. However I found myself flying most of the time at reduced throttle. There isn’t a big difference between partial and full throttle, so I prefer to fly longer. At ½ throttle the Brewster still covers ground easily. One other thing - I have been amazed at how well the Brewster can handle wind. I have flown it in winds that have grounded much bigger planes. I guess the weight / size ratio of this plane is the reason for that. With a little breeze it is especially nice to launch and land this little Brewster. Low speed The Brewster is very predictable in landing. It has never stalled on its wing when I have been making steady straight approaches. I did spin it one time, but I had the throttle cut and I was banking steep and feeding it with plenty of up elevator. I don’t blame the plane for stalling then. Aerobatics The Brewster is capable of flying moderate aerobatics. Loops and rolls come easily. Inverted flight is easy, although it takes quite a lot of down elevator. I have had much enjoyment of one particular "stunt". I make a high speed run towards myself and when I get it around somewhere on top of me, I bank it hard and give it full up elevator. It’s fun to look how little space this little Brewster requires to make a full turn. No wonder the pilots liked it’s ability to turn tightly. Sometimes I can also see a funny fishtail movement while I do it. This might be due to elevator stalling. I hope you enjoy building a Brewster. It’s a plane that seems to turn heads at the field and it’s fun to fly. It would be nice to hear about other Brewsters flying out there. Let me know how your Brewster flies! You can E-mail me at marko.terava@analyste.fi . Miscellaneous pictures: Prototype and second edition Wood ready A little trick from my friend. A round of lathe treatment to an old s400 and voila: you have a tool to do some neat engine holes!