TOP FLITE GIANT CORSAIR
PRODUCT TEST REPORT
By Dick Pettit
The Vought Corsair is widely considered to be the finest carrier based fighter of WWII. Its huge power plant, coupled to the largest propeller ever used on a fighter, necessitated the design of the characteristic inverted gull wing. Top Flite Models has been very active in releasing Gold Edition versions of their popular warbirds, with several done in giant scale. The first in the series was the Gold Edition Giant Mustang, which I reviewed several months ago. The Mustang was a great kit and a great flyer, and has had more than 60 very successful flights so far. It always receives rave reviews at all the events where it appears.
Then the time seemed right for another Gold Edition giant kit, and this time Top Flite chose to release a giant stand-off scale version of the popular F4U Corsair, done in 1:5.75 scale, with an 86" wing span, provisions for rotating Robart retracts, and working six-piece split flaps. The Corsair kit has recently been made available, so we hastened to get one for review.
When the huge kit box arrived, I was amazed at the weight! I opened the box to find many sheets of well done die-cut lite-ply and aircraft ply parts, die-cut balsa parts, and many sheets and sticks of balsa. The huge plan sheets need to be spliced together because of their large size, and the plastic cowl and canopy were also appropriately large. The 60-page instruction manual, with a multitude of illustrations and photographs, provides all the construction details, a list of additional parts and materials the builder has to provide, flying instructions, and even several "handy hints" to help put all those parts together. So, what are we waiting for?
I began by inventorying all the parts, and there are a lot, in the box. All of the sheets, sticks, and die-cuttings were there, except one die-cut sheet was listed as "Quantity 2" on the die-cut sheet layout page in the book, and "Quantity 1" on the inventory list. Well, only one was provided in the kit, but two are necessary to complete the kit. Also, one small plywood part was missing, along with a fender washer to hold the stab in place. I'll contact Top Flite when construction is complete to tell them that these parts are missing.
Next I labeled all the ribs, formers, and other die-cut parts, and separated them from their beds, placing the parts in storage bags for future use. I was. accumulating a large number of scrap sheets, but I decided to save them to see what part of this kit was supposed to be thrown away. To my amazement, I accumulated more than 6 lbs. of scrap wood from the die-cut sheets alone. One could almost build another small plane from that wood! But, considering that the kit box weighed more than 22 lbs. before I started building, the Corsair will still be a heavy plane.
All construction on the Top Flite Corsair will be done using Zap brand adhesives, along with some yellow carpenter's glue. I have been using a painting mask during construction of the more recent review projects, and have found only minor discomfort while using any form of CA. I have also refrained from the use of any type of CA accelerator, which causes me to experience cold and flu-like symptoms, even with the mask.
It seems to be common practice these days for kit manufacturers to have the builder start with the tail surfaces, and I have to admit, it's as good a place as any to start. Balsa sheets are edge glued for the covering, and the stab and fin are built from balsa sticks. Sheeting is then added to the top and bottom, and after a little shaping and sanding, the stab and fin are done. The elevator halves and rudder use a balsa center core to which balsa ribs are attached, simulating the open structure on the full size Corsair. The covering material will show this realistic detail quite well. Once the leading edges of the movable surfaces are beveled and drilled for hinges, the tail surfaces are about complete.
We next move to the wing, starting with the hefty center section. No less than three laminations of aircraft plywood are used to build up the massive center spar assembly. To this is added front and rear rib sections, followed by a laminated leading and trailing edge. It is all built flat on the board, practically speaking, and any warps in the structure would have to be almost planned. When the center section is complete, it is as strong as the Brooklyn Bridge. Be sure to dry fit all the die-cut parts before gluing them into position, because several of the notches need to be made a bit larger for a perfect fit.
Next the wing outer panels are built using traditional hardwood spars, balsa ribs, and full sheeting to be added later. Servo hatches are fabricated in place and the wing panels are just about ready to attach to the center section. Yes, Virginia, this is a one-piece wing when done! The outer panels are aligned to the center spar joiners, and epoxied in place. When the epoxy cures, the large wing is ready for some rough sanding to allow the sheeting to sit firmly on the structure. Good quality 3/32" balsa sheeting is trued up and edge glued using yellow carpenter's glue to make the wing sheeting. The outer panels are sheeted with an upper and lower section, while the curved center section use several different shaped sections to conform to all those curves. One section is actually sheeted with the grain at a 45' angle to the wing! This allows the sheet to be formed over one of the complex parts of the framework Use a little caution when pressing these sheets into place, because it is easy to poke a finger through the balsa (Well, it was easy for me!) . I used hot water with a small amount of rubbing alcohol to soften the balsa. I used Slo-Zap to stick the sheeting to the framework to allow a little time to adjust the final placement. When the upper sheeting is in place, a set of plywood fixtures are Zap'd to the wing tip sheeting, and the wing is set on the building board' with the fixtures setting the correct amount of washout. Then the lower sheeting is installed, which locks the washout permanently. After adding and shaping the balsa block wing tips, the wing is ready to be. sanded. Retract, servo, and control surface installation will be done later.
The upper fuselage half is now built using a balsa perimeter frame to which formers and stringers are added. There is a very strong engine box structure built into the top of the fuselage also, and I saw there was going to be a lower box added to the finished structure when the rest of the fuselage is built. Balsa sheeting is then edge glued as per the manual, and applied to the framework. It requires the use of some warm water to which I added some rubbing alcohol to allow the 1/8" balsa to bend easier.
Most of the construction so far has been put together using Slo-Zap, a product that takes a while to set up, but seems to penetrate the wood surface well. I even use it in place of epoxy for laminating plywood pieces, with clamps and rubber bands holding the pieces together. It allows for the parts to be adjusted prior to final placement, and once set it holds forever.
The balsa sheeting is cut to the correct shape using the "chalk line" technique. One edge of the sheeting is placed in position and pressed into a dark chalk line rubbed onto the stringer to which the sheet is to be attached. The sheet is then removed, trimmed to size using the chalk line, checked once again for proper fit and then Zap'd into its final position. Keep this in mind for use on other projects.
To complete the upper fuselage, a balsa block is Zap'd to the top of the structure, trimmed to approximate shape, and planed using your trusty Master Airscrew Razor Plane, what I consider to be one of the greatest tools used in modeling.
There were a couple of problems in the assembly manual concerning the order in which parts are added. The "torque rod braces" are easy to find and are shown on the plan sheet, but are next to impossible to put into position by the time the book says to do it! The same holds true for the missing hardwood block on the underside of the stab mount. It should have been added before the stab plate was Zap'd into place. I contacted Top Flite via their web site email and received a timely and accurate reply. The manual will be changed, and the missing die-cut sheet will be sent.
With the top of the fuselage completed, it is turned over and placed on one of those Robart Super Stand II's to keep it from rolling off the table. The bottom part of the engine box is then laminated and installed into the slots in the top engine box sides. Everything fit perfectly, and some Slo-Zap secured the parts forever. More formers were added, along with more stringers and the rest of the retractable tailwheel mounting structure. A plywood firewall is then installed, and I added dowel pegs around the perimeter. The wing mounting block was added, along with reinforcement blocks. I'll add some dowel pegs to this joint later, too. More 1/8" balsa sheeting is edge glued with yellow carpenter's glue and added to the formers and stringers, again using the "chalk line" method. The sheeting operation takes some time and patience, but the results are well worth it. The fin and stab are mounted, and blocks are glued into place and shaped to match the rudder. The fuselage actually extends quite a ways behind the rudder. Final shaping and sanding on the fuselage makes it look a lot closer to being finished.
It's time to fit the wing to the fuselage, and it isn't all that difficult to figure out. The wing saddle is covered with some wax paper, the wing dowels are inserted into the fuselage former holes, and the wing mount block is drilled and tapped' for nylon bolts. A rear section is built onto the wing, and a belly pan is constructed on the bottom of the wing. Then the radiator air intakes on the leading edge of the wing panels are cut from molded plastic and inset into the balsa leading edge. They're Zap'd into final position, and a little Model Magic is used to fill the slight gaps.
Next the ailerons are constructed from leading edge material, a center balsa plate, and balsa ribs. After planing and sanding, they're ready to install using Robart large point hinges. I'm really getting to like these hinges quite a bit. Do you suppose it has anything to do with my finally learning how to install them correctly! The aileron control linkages were fabricated from 4-40 rods, clevises, and a pair of Hitec HS-545 five-pole servos. These should provide plenty of power to move the ailerons during hard maneuvers.
I started to build the outer flaps (there are actually six flap sections), but found another error in the plans and materials. A 15/16" stick for the flap leading edge was supplied as a 5/16" stick, and I had to make a trip to the hobby store to get a replacement. Again I sent Top Flite an email, and they promise to fix this problem too. An addendum to the instructions and the missing or incorrect parts will be provided to builders at no charge.
Once I located some replacement materials, the flaps were fabricated over the plans. The center curved sections are built on the wing between the outer and inner sections. They are keyed together using music wires between the sections. Only the inner sections are driven directly by a servo.
There didn't seem to be much in the way of balsa or plywood parts left in the box, so I determined that construction was just about complete. Then I had a long wait for the retracts to become available before I cut out the mounting holes in the wing and fuselage.
Engine mounting was simple. I used the powerful Supertigre 4500 glow engine on the Corsair, using a Bisson muffler and a J'TEC motor mount. The engine mount supplied with the Supertigre engine is quite a bit longer than necessary, and modifications would be necessary to bring the prop hub back to where it belongs. The J'Tec mount allows proper mounting while still keeping the carburetor adjustments accessible. I mounted the ST4500 upright for good operation, and installed an extension wire from the needle valve to the edge of the cowl. The Bisson muffler uses two exhaust pipes that aim directly down and out of the cowl. I'll have to fabricate some sort of extension pipe to get these tubes out of the cowl. A baffle plate was fabricated from plywood to block off most of the inlet opening, except for that which allows airflow directly over the engine.. An optional dummy engine and a plastic molding was placed in front of the baffle to simulate the Corsair's huge radial engine. This assembly was painted, but will not be installed until after the cowl is completed.
I ordered an aftermarket cowl from Fiberglass Specialties, and it arrived in a week. It fit perfectly, requiring only a mounting ring to be installed to the fuselage. I cut a disk from lite plywood that would fit inside the cowl at approximately the correct location. Several hardwood blocks were fastened securely to the firewall, and the disk was mounted to them using small socket head wood screws threaded into plastic tubes. The disk was then cut out in the shape of a 1/2" wide ring to clear the engine and muffler. The engine was installed and the cowl was placed over the ring, making sure the prop hub was centered and spaced correctly. I then mixed up some Z-Poxy with milled fiberglass, and applied it to both the ring and the cowl. The cowl was reinstalled and allowed to cure completely, and was removed for final trimming. A cutout was made for the muffler tubes, a hole drilled for the needle valve access, and the cowl was ready to paint. There is a space between the cowl and the fuselage front measuring at least 1/4" all the way around, which when combined with the exhaust cutout, should provide adequate exhaust airflow.
After waiting for almost a month, the retracts finally arrived, and I was able to continue work on the Corsair. I cut out the wing panel for the retracts and installed them with minimal effort. They fit correctly, and the rotating mechanism worked flawlessly. I still couldn't complete the installation, though, because the air support system was still under construction at the manufacturer, along with the retracting tailwheel assembly. I did cover the wing panels and add the flaps and ailerons along with the servos and linkages.
I had decided early on to use Goldberg UltraCote to cover the Corsair. A simple color scheme in deep blue was chosen, and the plan was to use the included self stick decals to decorate the model in a scale-like manner. It may not be a true scale model of a plane that actually existed... but it could have! Gordon has told me all about his "Could Be Scale" classification, to now I have one!
The wing panels were easy to cover, with the most difficulty occurring when I applied the top piece at the gull shaped section. It took a lot of heating and tugging, but once it was in place it looked quite presentable. Facing another undetermined wait for the rest of the landing gear equipment so I could finish covering the fuselage, I caved. I had waited long enough, so I decided to cover the fuselage now and cut out the required clearance hole later for the tailwheel assembly. I applied Ultra-Cote to the stab and fin, and used only two pieces of covering to finish the entire fuselage! Yes, this required a lot of heating and but the results were well worth the effort!
Finally, just a week before Christmas, the tailwheel and air system arrived. The clearance hole was cut and adjusted for the installation and all the air lines were installed, complete with fittings, valves, and air tank. I pumped up the system and used a few drops of dish soap on each connection to check for air bubbles which would indicate an air leak. None were found, so I adjusted the control valve for a realistic up and down travel rate. The Robart adjustable control valve does a fine job, and has never been a problem in any of the retract systems I have used.
With final details like canopy mounting, fuel system finalization, and setting up the control throws completed, I took the Corsair outside to run the engine in the model. After priming the ST4500 ran really well, turning the 22x10 Master Airscrew wood prop at about 6000 RPM. This may not sound like very high RPM, but I loved it because there are no more winter leaves in my back yard!
The engine idles well at under 2000 RPM, and it transitions quickly to higher speeds. There was more than sufficient power to pull the Corsair briskly through the rather tall grass in my backyard (Hey! I mowed it a couple of times last year!) With most of the testing complete, it was time to head out to the flying field and fly the new Top Flite Giant F4U Corsair.
I took off from work on a really beautiful January afternoon, planning to have the flying site to myself. When I arrived, however, I found that several other fliers had had the very same "good weather" idea. They should be ashamed!
After taking a roll of ground photos of the Corsair, I prepared for the first flight. Radio range checking proved that all controls were rock solid, a thorough inspection revealed no problems anywhere, and I rechecked the balance point (CG) before filling the fuel tank. I was also careful to check the CG with the retracts pulled up. This is very important with the Corsair, and any model with landing gear that retracts to the rear. The model must be balanced with the gear retracted! The gear struts and wheels weigh more than a full pound, and they do have an affect on CG, which changes as much as 1/2" between extended (forward location) and retracted (rearward location). With the model properly balanced with the gear retracted, the plane will be a little nose heavy with the gear extended, which I consider an added benefit, while taking off and landing.
It takes a while to fill the Corsair's 32 oz. fuel tank. Then, using a rope restraint to hold the model in place, I started the ST4500 on the first flip after priming. When all seemed to be in proper order (i.e., I could think of no more excuses to put it off), a few passes back and forth on the grass runway showed that its ground handling was fine. With my photographer in place, the power was slowly increased, a little right rudder was added, the tail lifted, and the wheels left the ground (along with the rest of the plane, I might add, of which I was reeeeeeal glad). A moderate rate of climb was possible at less than full power, and the gear were still down, which added to the drag factor. A couple clicks of aileron trim and a little up elevator was all that was necessary to trim the Corsair for hands off straight and level flight. During my next pass over the field, I flipped the gear switch and the retracts disappeared (gasp). The CG shift to the rear did make it necessary to add a little down elevator trim, but I expected that and was ready for it.
Soon I added full power and climbed to a comfortable altitude to check the low speed characteristics. On the way, though, I did a roll or two, just to show off. Pulling the power back to high idle; the Corsair slowed to a crawl, the nose dropped, and it noticeably fell off to the right, but not severely. I took this as a good indication that landing wouldn't present any problems or surprises.
Adding power and gently diving for the runway, the Corsair looked and sounded really great... according to the spectators. Strangely enough, I don't remember many details about most of the maiden flights I've made... except for the ones that had spectacular (usually bad) results. Luckily, these have been few and far between.
Back at altitude, I directed the Corsair to fly a big loop, and it responded quite nicely, without a hint of snapping or falling off at the top. The sound of the wind whistling through the cowl sounded wonderful, and just added to the excitement. Rolls are scale-like, but could be made almost axial with some elevator added at the proper moments. Stall turns and Immelmanns are easy to complete, and inverted flight needs only a small amount of down elevator.
I feel that the ST4500 engine is a good choice for powering the Corsair. It makes plenty of power to pull the plane at scale-like speeds at less than full throttle. The relatively low RPM with the big prop produced some noise, but it certainly wasn't objectionable. I think it would be a good combination for those of you who desire a glow engine on the nose of your Corsair.
Quite a few of you prefer a gas ignition engine on models like this, and the US-41 is another 'acceptable' choice, but a bit more power is always nice to have in reserve. Personally, I'd consider an engine in the 50-62 cc range.
I flew the Corsair longer than normal for a first flight, but I was having a good time, it was a confidence builder, and there was plenty of fuel in the tank. But it eventually came time to set up for the first landing. First, let's see those wheels come down (please!). Check (Whew!). Head downwind, reduce power to half, turn right to base, come back on the power a bit, and add a little flap and down trim. Check. Turn on final, add a little more flap, add a little power now, and keep it lined up with the runway. Check. Oops, we're a little high... reduce power, let the nose drop a bit... now level off... add a touch of power... let it settle down... the wheels are just about to... touch down! First flight complete... Oh yeah... kill the engine.
First flight completed! It was great fun, but still... Whew!
After checking the Corsair for loose parts, and adding almost 24 oz. of fuel to the tank, the subsequent test flight just reinforced my original opinion. The Top Flite Giant Corsair is impressive, spectacular, realistic, and above all, fun to fly! What a great model!
In summary (or did I just do that?), the Top Flite Gold Edition Giant Corsair kit is well worth the investment of time and money, even when the retracts and engine are added. The kit goes together quite nicely, and all the parts and materials are top quality. The plans and instructions are well done, and there are plenty of helpful hints and tips that can be used on other planes as well. The Corsair flies wonderfully, and is easy to take off and land. Without reservation, I highly recommend this kit to the modeler who wants a great flying model that really attracts attention wherever presented and flown. The Top Flite Giant Corsair is destined to be an extremely popular model, and of that I am certain! This Corsair is going to be a common sight at giant scale fly-ins around the country, and mine will be just one.
Good quality kit materials; excellent plans; several novel construction details; looks great, and flies even better! This is fantastic flier!
Reprinted with permission.
One die-cut sheet was missing; several small errors in instructions; kit was released long before the required accessories were available.
April, 1999 R/C Report
Editor: Gordon Banks