• Wing Span: 64 in (163 cm)
• Wing Area: 612 sq in (3948 cm²)
• Length: 53.5 in (136 cm)
• Weight: 6.5 lbs (3.0 kg)
• Engine: .40 - .51 2 - cycle
  (6.6 cc - 8.4 cc 2 - cycle)
  .70 - .91 4 - cycle
  (11.5 cc - 14.9 cc 4 - cycle)
• 5 Servos required

Even though the Great Planes Cap 231EX can be completed quickly, it is difficult to tell it's an ARF. The superior construction of this sport-scale R/C model rivals that of any built-up kit. It's engineered for exceptional maneuverability, low-speed stability and precise response. It comes finished in MonoKote. Great Planes hardware comes with the kit to make assembly of the kit quicker and easier. The prepainted ABS cowl is large enough to conceal the engine almost entirely.

The Cap 231EX goes together easily. An experienced builder can accomplish the building task in about 10 hours. The instructions are clear and well written, with good illustrations in the form of photographs. The Cap 231EX comes finished in MonoKote, which is a vast improvement to the covering used in most ARF's. The base color is white and the accents are blue and teal green. The fuselage is blue and teal with two white stripes running longitudinally. The wing is white with a blue and teal sunburst pattern both on the top and bottom of the wing.

As is the case with most Great Planes kits, the hardware is mostly first rate. The kit comes with pin type hinges, nylon control horns and clevises that appear to be the same quality as those sold as accessories by Great Planes. The control rods are hardwood dowels with steel pushrods on each end. The only weak hardware is a rather flimsy aluminum main gear and some undersized wheels.

The ailerons on this aircraft span nearly all of the trailing edge of the wing. No option is included for flaps unless the buyer uses aileron/flap mixing on a computer radio. The kit comes set up for dual aileron servos and torque rods are not an option on this kit.

The cowl comes in three pieces and once trimmed properly with a sharp pair of scissors, it goes together quickly. The cowl is white PVC plastic with the top painted blue. The design of the cowl on the Cap 231 provides for a fully-enclosed engine. The only non-scale holes needed are an access hole for the needle valve extension, glow plug/cylinder head, hot air ducts and exhaust. A Pitts-style muffler was used and it is completely enclosed except for the last 1/4 inch of the tail pipes. The wheel pants are made of two pieces of PVC plastic that must be cut, trimmed and glued together. Great care should be taken to maintain the proper width of the completed wheel pants. If they are not assembled according to the instructions the wheel opening will be much too wide for the wheels. There is also a clear canopy which must be trimmed then glued to the fuselage.

The instructions aren't very clear on the cowl cut-outs. Both main air intakes and the other two scale intakes on the front of the cowl were cut out. Two 1" by 1" air exit slots were also cut in the bottom rear of the cowl to help airflow. Finally, a circular cut-out over the cylinder head and an access hole for the needle-valve extension were made. Due to the shape of the Cap 231's cowl, just about any engine will fit entirely inside the cowl. While this looks great, steps should be taken to assure adequate airflow exists in order to avoid overheating.

As with many ARF's, the kit is lacking in some areas. The firewall, for instance, is lite-ply and will pull loose without too much effort. It should be replaced it with high-quality 5/16" plywood. The fuselage floor is also quite weak. Reinforcement with a square of 5/16" plywood is recommended. Failure to do so can result in the main gear pulling the fuselage floor out on a hard landing.

The wing mounting design from the factory needs an upgrade to make the aircraft both safer and more robust. The mount consists of a block of wood on the front that overlaps another block and a single nylon bolt through the trailing edge. It is strongly recommended that two nylon bolts be used with one on each side of the centerline of the aircraft to ensure that a failure of one bolt will not cost the pilot an aircraft. Use standard nylon bolts mounted into steel blind nuts using the same mounting technique called for in the plans of the single nylon bolt.

The landing gear is made of a pretty weak piece of aluminum. If the aircraft is operated off a grass field, the pilot can expect to spend a lot of time straightening it. It is recommended that the gear be replaced with a fiberglass type gear. This is not only more durable but can be painted to complement the color of the aircraft. The wheels were replaced with DuBro Low-Bounce 2.75" wheels. The stock wheels are a little small for the aircraft and are also very soft. The sidewalls of the DuBro wheels are stiffer and allow better ground handling.

The instructions are very clear about the recommended control throws for both high and low rate settings. Pilots who use radio that do not have dual rates should start with the control throws limited to the low rate settings until familiarity with the aircraft is gained. The Cap 231 is pleasingly stable in the air but is no trainer and is certainly not a suitable aircraft for the beginner.

An OS .61 engine with a 12x6 prop was used. This combination exceeds the recommended arrangement but provides for much better vertical performance than would be possible within the recommended range of engines.

The roll rate on the low rate setting is about 2 1/2 rolls per second. On high rate it's closer to 4 rolls per second depending of course on airspeed and amount of control input provided. Caution must be used to avoid elevator induced snap rolls which can occur even on the low rate setting. Until the pilot is familiar with the aircraft, radical elevator input should be avoided. In the beginning, loops should be large and round and tightened gradually until the aircraft snap rolls. This technique will help the pilot learn when to expect snap rolls.

This aircraft will not flat spin on low rate and high rate flat spins are not a problem. This may be due to the larger, heavier engine used and may not be true in all aircraft. Flat spin recovery is straightforward and happens quite quickly. Inverted flight requires only a minimal amount of down elevator input to maintain level flight. Overall the aircraft is very responsive in the air.

Landings need to be pretty "hot" due to the long, tapered wing. There has been no noticable tendency to tip stall on either takeoff or landing. The length of the wing combined with the high landing speed does tend to make the aircraft float down the runway on landing and should be a consideration depending on the configuration of the field where the aircraft is operated.

The wing covering, while very pretty, can be misleading in the air. Since there is a high-contrast sunburst both on top and below the wing, it can be difficult to tell whether the aircraft is right-side up or not. This can be particularly disorienting following an elevator induced snap. Although this aircraft is quite easy to fly under normal circumstances, one definitely does not want to get "behind the plane".

The CAP 231EX ARF kit from Great Planes is a very high quality kit. Big pluses are the fact that the covering is "real" MonoKote, and the GP hardware is of high quality. Weak points are the fuselage floor, servo tray and firewall. All are likely to fail over time due to the low grade of material used in their construction. In high rate trim, the aircraft can do just about any maneuver yet is still easy to take off, fly and land. This model is highly recommended.