The CAP 231 EX is one of the most popular aerobatic flyers, and it has been faithfully reproduced in this very nice looking and solid aerobatic park flying model.
Last year Great Planes entered into the world of park flying electric flight. Among their growing list of electric kits and ARF planes, is one of the most widely recognized aerobatic models, the French CAP 231 EX. The EX variant has an aerobatic wing designed by Walter Extra. This CAP, decorated with its Breitling timepiece insignia is a real eye catcher. The Great Planes version is imported from Simprop. I had built two other Simprop models and they were all well designed models that were enjoyable to build. This one would be no different.
The Great Planes CAP 231 EX is constructed mostly of foam, with a small amount of balsa and plywood used throughout. The instructions are well written in a numbered step-by-step process. Each and every step has well-drawn figure to accompany it. In fact, the diagrams are so good that it is hard to follow along with the instructions. I kept finding myself ahead of the written part because I was following the pictures. When reviewing a plane, it is important to follow the instructions in case there is an error or an adjustment that could or should be made. As it turns out, the written instructions are as good as the figures. The instructions for this plane are excellent and get an A+ in my book.
This is everything that is included in the kit except for the decals.
Putting it together
This plane has much of the work already done for you. The tailfin is attached and the rudder and ailerons are pre-hinged. The instructions call for the use of epoxy throughout, but I used Cyanoacrylate (CA) wherever I could to save both time and weight. The construction begins with the attachment of the motor mount. There are two different mount designs to use. It depends upon which motor you choose as to how you install the mount. I built mine with the Acro Drive 350+ drive system. For this, all that was done was to cut two notches in the nose of the fuselage and then epoxy the mount in place.
Fuselage ready for mount... Use sandpaper to lightly roughen and remove paint from contact points.
The next steps are to build the undercarriage for the landing gear and the battery box. These are glued together to be inserted into the fuselage as one piece. Once installed, the battery will be held in the box by a removable hatch cover. The hatch is held in place by a small plywood strip that acts as a spring. The plywood spring will push a tap on the hatch forward to retain it in a notch in the box. The accompanying picture below will better explain how this is supposed to work.
On the last Simprop plane that I built, which had the same type of battery box, I had a problem getting it to work after the plane was constructed. The problem was that the plywood spring was getting caught in the foam fuselage. This prevented it from returning, so I needed to use tape to hold the hatch in place. I did not want this to happen again, so I made a few changes to this one. First, I removed the 1/8 inch spacer and second I cut the end of the plywood spring round so that the corners would not get caught. Lastly, I moved it up away from the bottom, so that just enough of the spring retainer could touch the tab on the hatch to work. When gluing these parts together, be extra careful not to get epoxy on the spring.
The servo tray needs to be assembled and glued into the fuselage. The metric conversion is 12 9/16 of an inch from the tail. The ailerons are controlled in an interesting way. The torque rods are inserted through the trailing edge of the wing into the ailerons. They are each placed between a channel of two pieces 1/8 inch balsa and then held in place by gluing in a cap strip. I secured the ends in each aileron with hot melt glue. I needed to be very careful not melt the foam, but it worked great. The servo side of the torque rod is connected directly to the servo, and no pushrod is used. The kit includes the parts to build an aileron actuator that the torque rods ride in. Be sure to get everything centered before you glue anything here. The actuator rods are just long enough to work. I ended up with my servo a little off center and one of the torque rods kept popping out. I fixed it with a wire tab. I also used medium CA to glue the actuator rods to where they were sandwiched by the plywood.
I used hot glue to mount the aileron servo in place.
The bottom of the fuselage needed to be cut off and glued back on after the wing was glued in place. Getting the wing in the proper position is a bit tricky. I recommend marking the wing as a guide before you apply the epoxy. Having a third or fourth hand here would be a big help. Alcohol can be used to clean up any epoxy that you smear on the wing but be very careful, as the alcohol will also remove the paint if you rub it too much.
A section of the aft turtle deck also needs to be cut off to install horizontal stabilizer. The seam is barely noticeable when the turtle deck piece is glued back on. My stabilizer was parallel to my main wing without any adjustments. At this time, small plywood control-horns were epoxied in place in the rudder and elevator control surfaces.
If you cut the aft part of the turtle deck at an angle, it will help to conceal the seam.
The CAP 231 EX has wheel pants attached to the landing gear. The wheel pants were not easy to assemble, and I didn't see them as being long lived, but they really made the plane look nice. The landing gear is slid into the undercarriage with epoxy and set with a V shape plug that aligns them and helps to hold them in place. The tail wheel is made of two plastic halves that are glued together. The tail wheel gear is pre-bent out of wire. A piece of balsa is glued into this wire to create a larger gluing surface, and is then epoxied into the tail of the plane. I recommend using thread to tie the balsa to the wire, as mine broke off and came loose.
I epoxied the pushrod sleeves at their rear exits and then used CA to secure them near the servo tray. Let them cross each other in the fuselage and pull them tight before you CA them in place. This puts some tension on them to keep them from flexing when the servos move the control surfaces. I really like the way Simprop installs the servos in their kits. Each servo is placed into a small wooden block that can be slid forward or backward in the servo tray. When they are in the right position, just wick some thin CA in to set them in place.
This is one of the easiest ways to adjust a servo that I have seen.
Power system
I used the AcroDrive 350+ power system in my CAP 231. This is the second best power system that Great Planes offers. I would have used the best, which is the Acrodrive 350 + BB, but it was not in stock when I placed my order. This system has everything that the 350+ BB has, except for a ball-bearing gear drive.
The power system comes as a package and includes a ball-bearing speed 280 motor with replaceable brushes, a 5:1 gearbox, an APC 9X6 slowflyer prop, a screw on spinner, and capacitors. The Acro Drive ran the 9X6 prop at 5.8 amps, 47 watts, and 4700 RPMs static.
The Electronic Speed Control
I used a Great Planes C-10 electronic speed control (ESC). This is a nice little unit. It includes a safe start that won't let the motor start until the throttle has been at full for a few seconds. It switches at 3 KHz, has auto cut-off, and a continuous current rating of 12 amps.
Motor installation
The motor and gearbox are screwed into the motor mount. I removed the screws after I had threaded them, and then wicked a small amount of thin CA into the holes that I made in the mount. This hardens the threads and keeps them from stripping. The spinner also needed to be built. I glued the two plywood spinner back-plates together with the grain in opposite directions. A little bit of sanding was needed to get it to fit on the gearbox. I glued it in place and placed the vacuum formed spinner in it. I ran the motor on a single cell and adjusted the spinner until it ran true. This was not easy, and it took a bunch of tries to get it right. As soon as I almost had it, I would knock it out of whack again. Once it was set, I drilled hole to screw in the four retaining screws. I think that truing it may have been easier if had put one screw in before I started. Once set up in the correct position, I cut the holes for the propeller. I recommend using a very sharp knife to do this, otherwise there is a risk of tearing the lightweight plastic.
Be careful if you use accelerator on the CA that you use to attach the spinner. I got some on the foam fuselage and it created indentations where I touched it.
Finishing it up
The cowl needed the plastic cheeks glued to it. I was dreading doing this until I figured out a great way to do it without getting epoxy on the nose of the plane. After cutting out each cheek and checking to be sure that they each fit well, I smeared epoxy on the inside of one. I put the epoxy all around the rim, but kept it back from the edge a little. I then held the cheek in place on the cowl in a position that would allow the epoxy to drip into place, but not escape onto the cowl. Because the cheek was held tightly, this sealed the glue inside of the cheek. When the glue was dry, I did the other cheek in the same manner.
One of the final parts of construction was the decals. I love decals! They are so forgiving and easy to apply. They sure did make this little model look sweet too. After I applied the decals, I installed the cockpit floor and canopy. I did not use glue; instead, I used the recommended tape method. I laid pieces of clear photo tape along the sides of the plane. These are to be used as an underlayment, which will prevent the paint and decals from tearing if the tape that holds the cockpit floor and canopy needs to be removed. I then used more clear tape to hold the canopy and floor in place. This concluded the construction and she was ready for flight.
Off to the field
The first time I took my new CAP out to fly, I knew right away that it was very flight condition sensitive. The day had started out calm, but when I got to the field the wind had already picked up. By the time I was ready to take off, the wind was blowing. I tossed the CAP into the air anyway. It was extremely difficult to control, so I brought it down, packed up, and went home.
The next time I took it out, the day was perfect! I usually hand launch most of my planes, so I tossed the CAP to the wind and let it climb out above the treetops. I was glad to see that I need only a touch of elevator trim before it was flying perfectly level. The sound from the gearbox made a purring noise that imitated a gas motor. It was loader than I expected, but there was something pleasing about it. I guess it was that it had a realistic sound.
Aerobatics
The climb rate was very acceptable, although there was no vertical performance. The roll rate was nice, and after I got a little used to the plane, I had no problem doing quick rolls close to the ground. Inverted was also no problem. A touch of down elevator held it nice and steady. Both inside and outside loops required a running start. There was not enough reserve power to pull it up and over the top without some speed behind it. Short runs of knife-edge were within its capabilities. That rudder definitely has a lot of potential with its large control surface. I spent some time practicing stall turns and nailed a few awesome looking snap rolls. I had a blast playing around with this little scale model. The effects of the two different colored top and bottom were a big help in keeping track of the plane's orientation. With the 350-mAh NiCD battery, I was able to get about four minutes of playful flight.
Slow flight
I was really surprised at how well the CAP slowed down. I spent quite a bit of time with it just crawling around at about ten feet above the ground. It maneuvers well in tight places. I have not yet been able to get a true slow flight timed duration, because I kept getting the irresistible urge to rev it up and fool around. It is probably not important anyway, because most people won't spend an entire flight just lethargically floating around the field with this plane. I just felt is was important the express that it does have excellent slow flying characteristics
Summing it up
Building and flying the Great Planes CAP 231 EX was a great experience. Overall, I felt the quality of the kit was first class. The only changes I would like to see are the addition of touch-up paint to the kit, and a little variability with the CG adjustment. My plane came out a touch on the tail-heavy side. Using the lightest servos available would cure this. Another great thing about this plane is the scale appearance. Few ARF park flyers look this good. It is one of the most attractive planes in my hangar. I couldn't see flying this plane with anything less than the highest-powered recommended Acro drive system. As with most true park flyers, it is limited to calm conditions for its highest performance and highest fun level. I can't wait for my next opportunity run some more electrons though it!
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