TOP FLITE GIANT CORSAIR
By George Jenkins
Name F4U CORSAIR (Giant Scale)
Aircraft Type Sport Scale
Mfg. By Top Flite Models/Great Planes Model Dist., P.O. Box 9021, Champaign, Illinois 61826-9021, www.top-flite.com
Mfg. Sug. Retail Price $429.99
Available From Retail Outlets
Wingspan 86.5 Inches
Wing Chord 17.25 Inches (Avg.)
Total Wing Area 1344.5 Sq. In.
Fuselage Length 67 Inches
Stabilizer Span 34.3 Inches
Total Stab Area 234.3 Sq. In.
Mfg. Rec. Engine Range 2.5 Cu. In.-4.25 Cu. In.(41-70 cc)
Rec. Fuel Tank Size 16-24 Oz.
Rec. No. of Channels 6
Rec. Control Functions Rud., Elev., Throt., Ail., Flaps, Retract Gear
Basic Materials Used In Construction
Fuselage Balsa & Ply
Wing Balsa & Ply
Tail Surfaces Balsa & Ply
Building Instructions on Plan Sheets Yes
Instruction Manual Yes (59 pages)
Construction Photos Yes
Radio Used JR 10IIS w/JR #4721 & 4131 Servos, 2000 mAh Battery
Engine Make & Disp. Zenoah G62 w/22 x 10 Zinger Prop
Tank Size Used 24 Oz. Du-Bro (Gas Conversion)
Weight, Ready to Fly 484 Oz. (30 Lbs., 4 Oz.)
Wing Loading 44.5 Oz./Sq. Ft.
WE LIKED THE:
Fit and alignment of parts, detailed instruction manual and plans, general layout of R/C compo-nents, and flight performance.
WE DIDN'T LIKE THE:
Typical fuselage construction with 3/32" balsa sheeting. You can easily see the right thrust built into the firewall. Fuselage is built with the upper half constructed over the full-size plan.
Typical fuselage construction with 3/32" balsa sheeting. You can easily see the right thrust built into the firewall. Fuselage is built with the upper half constructed over the full-size plan.
I first approached the manufacturer at the '98 Toledo Show and asked if anyone was slated to do a kit review. I received the kit on November 2, 1998 and flew it on February 20, 1999. The colorfully labeled box was 49" x 16" x 6" and, boy, was it heavy! This is a blown-up version of Top Flight's popular .60-.90 size Gold Edition of the Corsair. I grabbed the instruction book first and then glanced at the kit. I had already been alerted by Richard Seltzer, the manager at the Hobby Warehouse, to check if the canopy was crushed during shipping since they all were in the kits he had stocked. Sure enough, it was smashed to one end of the box and unusable. A simple phone call produced a bright shiny new one by UPS in three days. Also, a part was missing (the nose ring of the firewall) out of the first production run. (Note: The packaging has since been corrected.) This is the first in a series to answer the demand for easy-to-build Warbirds as the craze continues and IMAA legal size airplanes are being flown. I was familiar with the Corsair since I had built and flown one from an old Royal kit some 20 years ago and since Corvin Miller, my test pilot, had just completed and then competed with a slightly larger Ziroli Corsair at the 1998 Scalemasters in Columbus, Ohio. Knowing Corvin would fly this plane for the first flight photo shoot, I was going to be interested in his impressions of its flight characteristics. I found the plans and pictures very helpful, along with the reduced set of plans included in the 59-page instruction manual supplied.
Here the additional plywood plates are installed on either side of the spars where the bent wing center section joins the outer panels. The lead brick holds it down until the epoxy cures a full 24 hours.
The parts were easy to find using the die-cut layout chart also included in the booklet. The lite ply was of good quality and very well die-cut. The parts were bundled together or in a plastic bag. However, remember to measure the wood before you assume that you have the correct piece of wood in hand by the old eyeball method. There are some weird size pieces, so measure twice and cut once. After saying all this, this is definitely not a beginner's kit.
Modification of adding 3/32" plywood to the top and bottom of the wing along with a hardwood block to prevent compression by the 1/4-20 mounting bolt.
You need to know up front that this kit is designed for a set of 180° rotating Robart retracts and retractable tail wheel, as well as a US41 or G-62 engine for power. There are no alternate plans for a fixed landing gear arrangement.
One JR 4721 for each elevator, one for rudder, a separate servo for tail wheel steering, and a retract servo for the Robart retracting tail wheel. Only standard 407 servos were used for the Ultra Precision air valve and the throttle servo but never on the flying surfaces. Note all plugs are held together with clips for maximum safety, and wires are bundled out of the way.
I started with the fuselage first and went back and built the tail feathers as they suggested and then on to the wing. I used CA on most of the construction or 5-minute epoxy in high strength areas. I also did some strengthening in some areas that I felt were inherently weak. I will mention these as I go along with the construction. The fuselage is built top half/bottom half right over the plans covered by the new plan protector film; I love this stuff, nothing sticks to it. Make sure you read and look before gluing since there are some new construction techniques during assembly. The first thing I noticed was that the tail wheel mount was over-built and added unnecessary weight to the rear of the C.G.
It took 3 lbs. of lead screwed to the firewall, as they suggest in the instructions, to balance this model slightly nose down with the wheels retracted. You need to decide at this stage too, while the fuselage is in the bones, if you are going to use fiberglass pushrods or the solid metal 4-40 rods and tubes supplied by the manufacturer. Also, if you are going to have a full cockpit and pilot, just tack-glue the cockpit floor in place since it has to be removed later.
This is also the time to make sure your tail wheel retracts and the steering cables work by mounting all the servos for a dry run test before the outer skins go on. I had to remove the rear cross bracing as it was in the way. I fuelproofed the tank mounting area by closing off the area between F2A and F3A and painting it with alcohol-thinned 5-minute epoxy where fuel leaks can occur.
The instructions for the Isolated Engine mount #GPMG2000 on the plans were not real clear, so make sure to take measurements for the thrust line off the plans. The plane has right thrust built into the kit. I used the plastic engine standoff mount supplied with the US41 engine as a template for drilling the engine mounting holes but I also added three pieces of 3/4" spruce triangle to the engine mount to give it some added strength instead of the balsa suggested. I also used glass cloth and epoxied it in place. The construction is straightforward but care and attention should be paid to the stab and rudder steering arm to make sure it moves freely with no binding.
I did not use the plastic cowl supplied in the kit but rather sent it over to my good buddy Lenny Stenko of Take Flight Molds to make a beautiful fiberglass replacement cowl. It fit perfectly and will hold up longer than three plastic cowls. I also used the new Tethri Te Plastic Products cowl mounts using the 4-40 nylon screws supplied in the package.
I measured for the correct engine thrust and mounted the blocks on the cowl and then screwed the block to the firewall through the big opening in the cowl with the engine removed, then used the cardboard template method for the engine cutouts as shown on the plans.
Also, now is the time to silver-solder the rudder and elevator horns which are hidden and require a solder clevis for the split elevator and single rudder horn. I used the T-1 Rib as a template to cut the correct wing saddle on the wing skin sides. All the rest of the templates traced from the plans fit perfectly. I suggest using sandable white glue and not CA for the fuselage balsa covering, you'll thank me when you start sanding the fuse.
I now went back and built the tail feathers and added the balsa hinge blocks, to anchor my Robart hinge points into, on the elevator and fin. You will notice that the sheet for the rudder is 1/8" short of the plans; also, the factory did not include the 1/8" slot in the premilled leading edge. On my model, I added lead to the leading edge of the elevators as a mass balance to prevent any possibility of flutter. Use a Robart incidence meter to check the stabilizer and you should remember to measure-measure-measure to make sure the stabilizer is on squarely. Since the elevators were fabric-covered on the full-size Corsair, leave the trailing edge the same thickness so you can tack your fabric or film by painting the trailing edge with Balsa Rite film or fabric formula before covering. Tail feathers were a breeze to build.
I left this 'til last and you should too since this bent wing bird will bend your mind during construction. The gull is built up in the air and was made much easier with the aid of a magnetic building board. It is really important to hold this wing center section straight while building for proper alignment with the outer panels. The three laminated 1/8" plywood spars are plenty strong but I fail to understand why there is no plywood designed into the leading edge or trailing edge where it is needed the most. I have had a lot of failures with the hardwood rail mounts on retractable landing gear, so I was really surprised to see that the plywood ribs for the rail mounts were just butt-glued to the spar. I would have liked to have seen indexed notches into the spar for maximum strength of design.
I added two pieces of 3/4" spruce triangle to each side, a plywood reinforcement plate to the leading edge as well, and I made new rails for the retracts that went all the way to the leading edge rather than stopping short. These rails were epoxied in and then 1/8" dowel rod inserted in four places along each side into rails from the plywood mounting ribs. I have found out through experience that this area has to be strong to withstand the large G-force transferred into the area during landing. I also replaced the mounting dowels with longer 5/16" dia. ones and drilled into the spar 1/4" to locate the backside of the dowels. These are all personal choices.
I found that building the wing up in the air with no references or jig a little disconcerting. It would be easy to build a warp in the center section if you don't take the time to measure the TE rib tips to make sure they are in line. You may want to ask a buddy at this stage to help you hold while you glue. The rest of the parts were all cut accurately and fit well.
The wing panels attach to the wing center section while it is inverted on the building board to accommodate the gull wing design of this one-piece wing. I clamped and sandbagged the center section in place to ensure a correctly aligned wing. Here a balsa block is used for spacing height under the wing so you'll have to use sand bags or a lead brick to hold it in place. The panels have a plywood wing jig for the tip rib alignment that is temporarily installed at this time. This worked pretty well but much carving and sanding was needed for a perfect fit on the wing spars, trailing and leading edge. I added a plywood spline or biscuit in the balsa-to-balsa joint of the leading and trailing edges. I used a Du-Bro cutting wheel to cut a slot. Then a circular piece of 1/16" ply was cut using the same diameter as the cutting wheel that was then fitted and epoxied in the cut.
Since there were no plywood plates on either side of the wing spars to hold them in place, I added those too. The last area left out was shear webbing on the outer panels. There is just too much area to rely solely on the wing skins to hold the outer panels in line and to hope it holds the aileron as well. The final optional addition was to CA a piece of iron-on carbon-fiber tape on the top and bottom of the wing spars.
Sheeting the inside bend of the wing proved very interesting and requires a lot of time, patience, and fitting to make a smooth installation without breaking the balsa. Select the softer sheets for this and soak them good before you try it the first time. I used cardboard servo wire tubes from Chuck Gill's Aeroplane Works rather than rolled up paper tubes as shown in the instructions.
The trailing edge of the center section where the 1/4-20 wing bolts attach the wing consisted of one piece of hardwood butt-glued at 90 degrees to a balsa trailing edge. This was then attached with only 3/32" balsa. I added a square of 3/32" ply plate and another piece of hardwood stacked on the piece provided in the kit and tapered it to fit so the pressure of the 1/4-20 mounting bolts tightened directly to the fuselage wing mounting blocks. This area must be strong if you want your airplane to survive the everyday knocks of flying. The flaps on the Corsair take a lot of time to build and line up. Take your time when you get to building these babies. I replace the balsa blocks with hardwood and the 4-40 pushrod suggested in the plans with hard music wire. The inboard portion of the flap is the part driven by the servo and the other two pieces just follow. It is therefore important to get them in alignment, coming down at the same time and matched to the flaps on the other wing too. The aileron and flap servos are shown mounted to the servo hatch cover but I could not figure out why they were made of 1/16" plywood when the wing was covered in 3/32" balsa. (Note: This was to allow for the balsa to be sanded flush with the plywood.) I replaced the covers with 3/32", mounted the flap servo inside the wing on rails, but used the suggested method for the aileron servos again with 3/32" plywood.
I just didn't want another all Dark Blue Corsair; it's been done to death. I always start looking for a paint scheme before I even start building so I can visualize what the finished plane will look like. So—I was prowling in the plastic kits at my local hobby shop before the kit ever arrived and found the French Navy paint scheme you see on the plane now. I figured it would be easier to see with the black and yellow stripes and I was right. After judging at the Nats, Scalemasters, and Top Gun, I can tell you that a dark blue airplane's profile gets lost easier in flight.
I used the Century 21 film for the airframe and matching paint for the cowl. Use a primer and give it 5-6 coats, separated by a few minutes to get a true matching color.
I used the Balsa Rite film formula in key areas like on all hardwood, cowl, and cockpit edges, and the inside bend of the wing. I managed to cover this inside bent wing area with just one piece of film but I would not recommend it. It took me about 2-1/2 hours to do just this part of the wing! The fuselage was covered with just two pieces and was a piece of cake if you start in the center of the fuselage and work out.
I then noticed an ad for Scale Skins in the Southern Scale Warbird Association newsletter and called Frank Campbell about adding the panel line and rivets detail for my Corsair. I sent the plans to Frank and he used a CAD program and 3-view of panel lines and rivets of the F4U-7. He played with the color of the resin paint and found the medium gray looked the best when applied over the dark blue. The graphics and letters can be printed on the wing skins but the roundels and lettering were added later to my plane. I had never applied the Scale Skins before but, after watching the accompanying video and by using the Fast Tac application spray made by 3M, supplied, the four pieces went on easily. They really look great. For just 20 minutes of work per wing for a sport scale airplane, they'll knock your socks off. However, since the resin ink on the clear 3M skins is not fuelproof, I had to spray over the skins (make sure the skins were completely dry - 24 hours) with flat clear LustreKote. It dulled the finish to make it look more like a Warbird and fuelproofed it at the same time. I normally finish my competition airplanes with 3/4 oz. fiberglass cloth with resin and paint but this would have added another 2 to 3 lbs. to the overall weight.
Even though I was provided a US41 engine for the article, after weighing the Corsair I decided that the airplane would fly adequately, but it would not have the Warbird performance I was looking for. The Zenoah G-62 weighed 3/4 of a pound more, was the same length, and since I needed 3 lbs. of lead weight in the nose, I decided this was the only way to go. The bigger 22 x 10 Zinger prop also reached above the massive cowl, making the blade tips more effective. I am addicted to Bennett mufflers and used their standard 2-pipe muffler and then cut off the pipes to about 1", so if a belly landing was necessary, they would not be in harm's way. The mounting was the isolated mounts recommended in the kit that consisted of eight rubber grommets and eight washers that center in holes laser-cut into 1/4" plywood for the 1/4-20 bolts. Since the US41 and G-62 had the same bolt pattern and length, it was no trouble to swap out right before the initial flight. However, as Murphy's Law would dictate, the throttle was on the other side so I had to reverse the set-up and swap out the engine and the retract servo location. I used a 32 oz. Du-Bro tank with a gas stopper with three lines and medium-sized Tygon tubing. I had a chance to use my new tubing bender from Du-Bro and it worked great; finally, a solution for bending tubing without crimping the tube and that's easy to use. The Sullivan Filler Valve was installed in the cowl along with the kill switch on the other side. I always use a capture ball clevis from Sullivan, along with the ball provided for the throttle bellcrank to control the engine power. I always use a Du-Bro red and yellow rod with 2-56 studs to go to the servo so that there is no chance engine electrical noise will come back along the operating cable into the radio compartment.
I used JR 4721 for servos for all the flying surfaces with the heavy duty aftermarket Du-Bro servo arms and a standard JR servo for the engine and retract valve. Separate servos were used for tail wheel steering and rudder on an amplified Y-harness, as well as the two servos for flaps' operation. The ailerons are on two different channels for differential throw which is easy to set on the 10 IIS JR transmitter. A retract servo was installed for the tail wheel even though I used air retracts. The new 910 JR receiver was installed, along with eleven servos. Don't try to use those standard-size .40 to .60 servos in any large scale plane; you are asking for trouble.
Also, go for a minimum size 1200 mAh battery pack, or better - an 1800 mAh! I programmed in the throws for the surfaces as suggested but found that more throw was needed on all surfaces but mainly on the aileron. The roll rate was way too slow. I wound up with 1-1/2" up and 1" down on elevator, 3" on rudder throw, 1-1/2" on ailerons, and 2" on flaps. I normally fly coupled rudder (20%) aileron, but this bird doesn't need it since it doesn't slide around the corners. The instructions suggest the need for as much as 3 lbs. nose weight and I needed every bit of it. I balanced the model with a slightly nose down attitude with the retracts up. Remember, nose heavy airplanes fly forever, tail heavy airplanes fly only once.
After a run up of the engine to check idle and top rpms with a tack, and kill of the engine by throttle and kill switch, I did a long distance range-check with the engine running. My trusty JR has never failed me yet, but since electronics are always subject to Murphy's Law, it never hurts to check. I got my camera ready and handed the transmitter to my trusted buddy, Corvin Miller, for the first flight test and flight shots. Corvin has lots of years of flying a Corsair, so I had full confidence he could make a good first flight evaluation of this new bird. I was pleased when he said upon landing that it flew great. After several low passes for flight shots, we made some normal aerobatic tests. First was a roll which proved to be very slow and scale-like but requiring more elevator than usual to keep the nose up when inverted. We decided a lot more aileron throw was needed so I wrote down the need to go to the 3/4" Robart aileron horn from the 1" original ones installed. Corvin then did a 4-point roll and the Corsair came through with flying colors. I say flying colors because up against that beautiful Florida clear sky, the yellow stripes really made this Warbird easy to see. We then did some slow flight and stall testing. Even at slow speeds, the stall rate is very slow and broke to the left but Corvin reported that he could have held it with rudder. Back to full power and the G-62 pulled it quickly up to flying speed for a full stall recovery.
After a few more low passes over the field, Corvin did a military break and dropped the Robart retracts on the downwind side of the traffic pattern. Then, as he reduced power, he fed in the flaps until full flaps were achieved on the final approach. The wheels seemed to just reach out for the runway and a perfect wheel landing. Wow, it is always a great relief to get a plane up and down in one piece without any damage or flight problems. After that landing, we started talking and I started making notes. We decided that the C.G. was perfect but that I needed to add some up elevator to the bird since Corvin reported that the plane had a slight tendency to nose-over on the first take-off, so I used the Sub trim routine in the transmitter to correct the problem. Other than those three clicks of up, there was no other trim needed. After waiting for my buddy, Bill McCallie, to arrive at the field later that morning, I finally couldn't stand it any longer, so I refueled and put more air into the retracts for my maiden flight. After flying the Ziroli Skyraider at 39 lbs., I assumed that the Corsair would fly much the same. I was ready at take-off with a little right rudder and some up elevator to keep the nose from coming over. I added power just gradually and, in about four fuselage lengths, it was off the ground prematurely. Well, I was surprised to say the least, so I just went to full power, it climbed on out and I retracted the gear to clean her up. I was glad I had made the decision to use the G-62; there is just no substitute for power.
Boy, what a difference 9 lbs. makes in a plane's performance! Well, it flew great and smooth as I rounded the corner for my first low pass over the field; that bent wing looked great coming at me. It did everything I asked it to. A perfect loop; a really slow roll, that scared me; I saw what Corvin was saying about aileron throw. I later sealed the gap on the ailerons with clear film at the suggestion of Bill McCallie and the lack of effective aileron went away. An Immelmann turn and a split S and it was time for a landing, so with my past experience and with Corvin at my elbow (sure is nice to have a Mr. Top Gun by your side on your first flight), I remembered to keep the power on during the approach to landing and to chop the power all the way only after the wheels had touched the runway. Of course, it is easy to land at the Sarasota Radio Controls alternate field at Hunsader Farms with a 1600' x 800' grass runway. One tele tale flight characteristic of a Corsair is the little tail waggle while in level flight. Every Corsair that Corvin has had does the same thing. We have all surmised that it must be a turbulence problem caused by the lack of a fairing between the wing and fuselage. I've always wanted to ask a full-size Corsair fighter pilot if he had experienced the same tail wag.
We had no flutter, over-control, or violent tendencies; just a very predictable warbird. I have concluded that, as far as construction goes, there are some weaknesses in the wing-mounting process and need for shear webbing in the outer wing panels, but these are easily remedied. However, this is a kit for an advanced or experienced builder. The quality and fit of parts was excellent and you will be pleased with the overall construction. There are a few extra pieces to the construction design, but you can live with it. I found that I had to study a few of the instructions and stare at the pictures and plans a little longer in a few steps to figure out what they were asking me to do. I found the instructions and safety ideas in the back of the booklet very informative, accurate, and would be of benefit to any modeler who was just moving up to a scale warbird for the first time. If you're in love with the Corsair and want an easy-to-build great flying airplane that you will be proud of at the field, the Top Flight Giant Scale Corsair is the next project for you.
Addresses For Accessories Used:
Reprinted with permission.
Robart Mfg., Inc., P.O. Box 1247, St. Charles, IL 60174, (630) 584-7616.
Tethre Te Products, P.O. Box 57764, Webster, TX 77598-7764, (281) 488-3993.
Take Flight Molds, 5350 McIntosh Pt. Ste. #120, Sanford, FL 32773, (407) 328-8350.
Scale Skins, 210 Lorna Square, Ste. #132, Hoover, AL 35216, (205) 878-2964, Fax: (205) 824-5079, E-mail: Camp205@bellsouth.net; Web site: www.scaleskins.com
February, 2000 R/C Modeler Magazine
Editor: Dick Kidd