CMP F4U Corsair 120 - 75.5" Review by RCUniverse.com's Erick Royer

WING ASSEMBLY

The Corsair's wing is assembled from three separate pieces; the outer wing panels and the center section. The outer panels are foam core sheeted with balsa and covered in a cloth covering and painted The wing center section is constructed of molded fiberglass with plywood formers.

LEFT: Aileron Servo Hatches RIGHT: Servo Mounting Plate

LANDING GEAR

The last step in the wing assembly was to install the outer wing panels. The first thing that I did was to scuff the fiberglass on the ends of the center wing section to ensure a good bond. Each panel has a dihedral brace. Using a generous amount of 30 minute epoxy, I attached the wing panels to the wing center section and held them in place with masking tape. Lay the wing on a flat surface, face up, and measure to make sure that the distance from the surface to each wing tip is exactly the same.

Once cured I noticed that the joint was pretty noticeable for each outer wing panel so I went to the local Home Depot and with a sample of the blue paint. They were able to match me a quart of flat latex that was a perfect match. This paint will also come in handy in the event that the fiberglass ever gets dinged.

The final detail is to install the 2 oil cooler scoops on either side of the wing. These are held in place with 30 minute epoxy.

Now it is time to attach the wing to the fuselage. The first step is to drill our the two holes for the leading edge wing dowels. There are plus (+) signs molded into the fiberglass to indicate where the holes must be drilled. One really nice feature of the wing assembly is that the dowels are actually made from steel. Once the holes are drilled, I applied some 30 minute epoxy into the holes and pressed the pins in place.

In the fuselage there are 2 corresponding plus (+) signs that will also need to be drilled out to accept the wings pins. Once this step is done, fit the wing into the fuselage. On my model, everything lined up perfectly.

Next measure from each wingtip to the rear center of the fuselage to ensure that the wing is square. Tape the rear of the wing to the fuselage so it does not move. Drill 2 holes through the wing into the fuselage in the marked locations for the wing hold down bolts. Remove the wing and install 2 blind nuts in wing mount block in the fuselage. Reinstall the wing and fasten with the supplied 4-40 wing bolts.

LEFT: Use Thread Soaked with Thin CA to Attach Music Wire Pushrod to the Hardwood Dowel.

MOUNTING THE ENGINE

The next step is to mount the engine. I chose the RCV 90SP to power this aircraft. The two main reasons that I chose this engine are its ability to swing a larger more scale prop, and it compact design would not require any cutting of the cowl for head clearance.

The manual illustrates how to install a conventional 2 or 4 stroke engine to this model. The required hardware for those installations are included in the kit.

With the engine installed, the next step is to install the fuel tank. I use a 3 line setup on my planes with a supply line, vent line, and fill/drain line. The fuel tank fits through the firewall and locks in position on the front of the servo tray. I held it in place with tie straps.

Next I installed the cowl. This was probably my favorite part of the model's assembly process. Why? Because only 2 small openings were required in the cowl; one for the needle valve and one for the exhaust exit. These were easily done with a Dremel tool and a sanding drum. The RCV 90SP fits perfect inside the cowl even with the muffler attached. I did use some rubber tubing to extend the exhaust just out the bottom opening of the cowl.

The Cowl is held in place by a plywood ring that gets screwed to the firewall. The ring is about 1/2" larger than the diameter of the fuselage. This leaves the required gap around the cowl to give the model a very scale appearance. I was concerned about cooling the engine and creating an escape are for the air to pass over the engine. To accomplish this I cut the plywood ring in half and only used the top portion and a small block for the bottom screw. This left me an opening from 3 to 6 o'clock and 6 to 9 o'clock. I painted the plywood black and installed it to the firewall with 4 self tapping screws.

The kit also came with a really nice plastic radial engine to dress up the front of the plane. This was another pleasant surprise. With the RCV 90SP I was not required to remove any of the cylinder heads from the radial dummy engine. I did cut out the area between each cylinder with a hobby knife to allow air to enter the engine compartment. The radial engine fit perfectly over the front of the 90SP. I mounted the radial to the cowl and held it in place with some 5 minute epoxy. Then I slid the cowl onto the nose of the plane. I had to drill 4 holes through the cowl into the plywood ring mounting blocks and then I attached it with 4 screws. The finished result could not be any more scale like if I tried. This RCV 90SP is an awesome engine choice for anyone wishing to keep the scale appearance of a model.

The last finishing touch of the fuselage is to install the canopy. The canopy is molded plastic and has been painted to reflect the window frame. All that needed to be done was remove the extra plastic around the outside and install it on the plane with 4 screws. I also ran a bead of canopy glue just to ensure that it would not come off in flight.

RADIO INSTALLATION

I chose the Futaba 9CAP system for the GSP Corsair. There are several reasons for my selection. First off, the 9CAP is quite possibly the easiest computer radio in the world to program. It gives me a lot of freedom to setup the plane any way I want. Second, I like the 2 slider controls on either side of the transmitter. These are perfect for flap control because they do not require you to remove your thumbs from the sticks to operate the flaps.

Complete Corsair with Futaba 9C Radio.

By this point the servos for the ailerons, flaps, and retract control are already installed. The throttle, rudder, and elevator are all that were left. These three servos install in the openings on the servo tray in the fuselage. I connected the elevator and rudder pushrod to the servo horn using a Z bend. I used an EZ connector to install the throttle.

Throttle, Rudder, and Elevator Servos Installed with the Receiver.

 

I used a 600 MAH battery to power this plane. According to my calculations, this battery should give me about 6-7 flights before I need to recharge it.

I installed a Dubro Quick Switch Charge Jack in the side of the fuselage to control the receiver switch and have access to the charge jack.

I needed to use servo extensions on the ailerons (12"), flaps (12"), and the retract servo (12"). These were all secured to the servo leads with heat shrink tubing.

Finally I connected all the servo leads to the receiver and using double sided foam tape, I mounted it between the elevator and rudder servos on the servo tray.

At this time all that was left was to check the CG on the plane. I bolted the wing on and set the Corsair up on my Great Planes CG Machine with the CG set to 100mm per the manual. I made sure the retracts were up before I tried to adjust the CG. Note: When a plane has rotating retracts that fold up back into the wing, always check the CG with the them retracted in the wing. The CG will shift forward a bit when you lower them for landing. If you balance the plane with them down, the CG could shift too far back in flight making the plane uncontrollable. Much to my dismay, the plane was balancing tail heavy. The CG range in the manual is 95-105 mm from the leading edge. I readjusted the CG machine to 105mm and it was still tail heavy. I removed the receiver battery from under the fuel tank and placed in on the cowl in the same position as the engine mounting block. It was getting better but still tail heavy. I placed a second 600 Mah battery in the same position and it began to balance slightly nose heavy, just the way I like it.

Now I have a dilemma. I do not need 2 batteries in the plane and I hate to add lead to a model. So, I decided to add a McDaniel On-board Glow Driver. This system offers me a few benefits. With the glow plug being so close to the prop, it provides me some safety. It requires a 4.8 volt battery pack which helps me with the nose weight that I need. And it can be programmed to light the glow driver at a low throttle setting giving me a much lower reliable idle. The control unit only weighs 3 oz. and it fit perfectly under the fuel tank. I drilled a hole in the firewall to pass the glow plug and battery wires through. On the side of the fuselage, I installed the charge jack and LED for the system.

The day has finally come when to get this bird in the air. It is the beginning of December in Connecticut. Normally this time of year we do not have much, if any snow on the ground. This year was an exception. We received a snow storm a week ago that left 10 inches behind. They temperature has not risen above freezing all week so there is still a good layer of snow on our flying field. The hunt for a field begins. I contact a local small airport near my house and explained the situation. Because the airport is not that busy they were able to shut it down for a couple hours to allow us to use the 5000 foot paved and plowed runway for our test flights.

MAIDEN FLIGHT

Arriving at the field the temperature was very cold, approaching 25 degrees. There was a slight crosswind. We attached the wing to the plane and pumped the air tank up to 100 psi using a foot pump that I converted for this purpose.

The engine was sent to me already broken in. Otto Kudrna, was kind enough to make sure the engine had the required amount of break in to ensure me a successful first flight. There are no special break-in procedures for the RCV 90SP. They just require a couple gallons to be run through it before it starts "coming into its own".

As promised a couple quick flips of the prop and the engine was purring like a kitten. I make a couple adjustments to the needle valve and was happy to see a maximum RPM of about 4950 rpm with the Zinger 18x12 wood prop. Before taking off, I changed to the Zinger 20x10 and noticed a slight drop in RPM, 4850 to be exact. I did notice the plane seemed to be pulling harder. While the 20x10 prop will produce more thrust, the plane will lose some forward speed, so I decided to use the 18x12 for the initial test flight. These RPM numbers may seem low to you, but it is important to remember that the prop shaft is gear reduced 2:1 over the crankshaft speed. This is one of the reasons why this engine can swing such a large diameter and pitch prop. Using a larger pitch will make up for the slower RPM. I was surprised how easy this engine is to start. They do provide a hex starter on the crankshaft of the engine for the use of a starter wand, but it really was not needed. A simple electric hand starter will work, or in my case, just flipping it by hand.

One final check over all the controls and we lined the plane up into the wind. The throttle was slowly advanced and the tail quickly came off the ground. After about 125 feet the elevator was gently pulled back and the Corsair broke ground. At about 50 feet in altitude, the retracts were raised. The climb out was very scale like and graceful. The RCV 90SP was pulling this plane with authority.

A procedure turn was executed and some slight elevator and aileron trim changes were necessary to keep the plane straight and level. The Corsair was very stable in the air and experienced no bad tendencies during normal flight. We climbed a few mistakes high and chopped the throttle to idle and gently pulled up on the nose to see how she was going to stall. The plane started to get mushy and the nose fell. I was happy to see that it would not drop a wing and snap. To recover, simply hold the nose down and add power.

High speed flight was very scale. The plane did not rocket around like a 40 size pattern ship, but it grooved along at a pretty good pace. There were no trim changes required.

It was time for the infamous Corsair low pass and victory roll. The throttle was lowered and a pass was made down the runway at about 25 feet off the deck. Once past the center power was added, the nose was pulled up to a 30 degree angle and a full left aileron roll was executed. Beautiful! When on Lo Rate the rolls were pretty slow. The high rate setting was more acceptable.

The Corsair was not designed to be an aerobatic airplane so you should not expect it to perform like one. It will perform graceful large loops and semi-axial rolls. The Split-S was also not a problem. Other than those basic maneuvers no other aerobatic were performed. This quite possibly one of the most recognized warbirds in existence, and that is the way it was flown, very scale.

Now we need to test the flaps. Back up about 2 mistakes high and the the throttle was slowly reduced to about 1/3. Flaps were added in 10 degree increments. Each time the flaps were increased you had to hold more pressure on the down elevator stick to keep the plane from ballooning. This could be mixed out with the radio at a future date. The trick to keep it from ballooning is to find the correct flying speed for the amount of flaps that you have deployed. The Corsair will fly considerably slow with full flaps. Just be careful in the turns. You do not want to stall it.

Next, we tried a touch and go with and without flaps to see how well they worked for landing approaches. We setup for a normal landing and lowered the retracts on the downwind leg. As we approached final the power was lowered to 1/4. The braking effect that you get with the 18x12 is awesome, The plane slowed right down for a gentle main wheel landing. Power was brought back to full and the touch-and-go was complete. I was wondering how much flaps would be required if any due to the fact that the plane slowed down real well. On the next touch-and-go, the flaps were deployed to about 20 degrees on final. The plane slowed very well. So much so that the power had to be kept at just under half to prevent it from stalling. The final landing was very scale-like.

All in all the CMPs Corsair performed as I hoped it would. It flew with plenty of authority and displayed no bad tendencies. The RCV engine performed very well. I guess I had it in the back of my mind that this engine was not going to be powerful enough. I was wrong. I have a new favorite warbird engine now! The Robart retracts worked very well. During the test flights they were cycled 4 times and there was still some air reserved for a couple more cycles. The Oleo struts did a good job of absorbing the initial shock of the landing. We were spoiled having such a nice paved runway to fly off of. It will be hard going back to our grass field in the spring!

I am very impressed with the CMPs F4U Corsair. The finish on the model it excellent and they put a lot of effort into scale details. The flight performance is everything I hoped for from a corsair of this size - excellent! The assembly process could be completed in 4-5 nights if you build it as shown in the manual without retracts. Mine took quite a bit longer due to the modifications that I made. Rest-assured that even in its stock configuration, this aircraft is well worth the money. I recently noticed that GSP has some new warbirds coming out including a Hellcat, Spitfire, and Focke Wulf. If you are not into spending 100's of hours on constructing and finishing a warbird from a kit, then look to CMPs, you will not be disappointed!

The RCV 90SP impressed the heck out of me! For a power plant that is so small and lightweight, it really puts out a bunch of power. The compact design makes it easy to install in just about any warbird and the 2:1 gear reduction gives you the ability to swing that large 2, 3, or 4 blade scale propeller. Look to RCV for your next warbird project!

The Robart retracts are a beautiful addition to any scale model. The 615 Rotating Retracts, Oleo Struts, and Scale Tires really enhance the appearance of this Corsair. As long as they are properly installed, they are very reliable. Be sure to add a set of Robart Retracts to your next model!

An finally, the McDaniel On-board Glow Driver. This is the first time I have used a device like this. I am so used to attaching a glow driver to the plug, starting the engine, waiting for it to warm up, and then removing the driver. Not anymore! The McDaniel system is very reliable and makes starting the Corsair a real dream. It does not take up much room or ad a lot of weight. This product is a big hit in my book and I am sure I will have several more models using one of these in the near future!