Going Fast in Carrier

Control Line Navy Carrier By Dick Perry | [email protected] As seen in the December 2023 issue of Model Aviation. THE TWO COMPETING FACTORS in Control Line (CL) Navy Carrier, high speed and low speed, have a different emphasis now than when under the original scoring system. With a definite advantage to high-speed performance in our early years, models tended to be smaller with higher wing loadings, and they were roughly 10 to 20 mph faster than today’s Carrier models. When the scoring was changed to use a ratio of high speed to low speed, the advantage of extreme low speeds (less than 10 mph) moved models to larger sizes to reduce wing loading, although models increased in weight and high speeds were reduced as a result. All current Carrier models tend to approach the maximum wingspan of 44 inches for the Scale Class I and Class II models. That produces a wing area of approximately 350 to 370 sq. in. because of the prototypes we model and their individual design standards and requirements. With models of similar size, low speed is much more a matter of practice, model trim, and weather conditions than equipment. The better fliers will usually group closely together in low-speed performance if weather conditions are the same for all contestants. That leaves high speed as a differentiating factor after a modeler has developed low-speed skills and model trim to be able to fly consistently at less than 10 mph (with a 3-minute low-speed time). I’ve looked at high-speed performance in contest data that is available from this year. The best high speeds are slightly less than 100 mph for internal-combustion engines and a little more than 100 mph for electrics. The equipment being used to achieve those speeds with electric models is widely divergent but shares some common attributes. Breaking 100 mph with an electric model requires approximately 2,000 watts (3 hp). That means more than 100 amps with a 4S or 5S LiPo battery are used for the 18 seconds of high speed. There are many ESCs available with adequate characteristics, but Pete Mazur, from Illinois, and I both prefer those by Castle Creations—not because of performance, weight, or dimensions as much as the data-logging functions that they offer. Without that feature, Pete and I wouldn’t have the data to share with you. The data logger is a great way to troubleshoot electric- powered models. I’ll deal primarily with models that Pete and I fly because those are the models for which I have data. We have both used the 100-amp Edge Lite ESC, and Pete is currently using the 130-amp Phoenix Edge or Edge Lite. They can be programmed with current cutoff at 150% of rated power (which we need on takeoff). They can also be programmed to eliminate the overcurrent cutoff, but I don’t recommend doing that. Should the propeller stop with a bad bearing, the motor windings short out, or the model ends up in the grass with the throttle open, the cutoff will save the equipment. We both operate with Thunder Power batteries. I use ProLiteX 25C 5S 4,000 mAh or 4S 5,000 mAh batteries, depending on the motor. I use them because of their size. Other cell configurations and dimensions won’t fit in my model. Pete uses the same brand with a 6,000 mAh rating in Class II. For Profile and Class I, Pete uses the 4S Hyperion G8 high-voltage battery rated at 4,400 mAh in Class I and 5,200 mAh in Profile. The limitations are weight and space. Any reliable brand of battery should work if you have enough capacity. My flights consume approximately 3,700 mAh for 103 mph high and 10 mph low, and more for longer low speeds, of course.

Speed control for the K&B 40S is accomplished with an exhaust slide and a Harry Higley fuel meter with crankcase pressure. Throttle control is accomplished by twisting the solid control line. At the bellcrank, a threaded steel clevis allows the control line to rotate. The Scorpion HK-3226-1400 has been a popular motor, and it was still available as of summer 2023. Pete uses the Scorpion or another helicopter motor, the Hyperion HS-3026-1400 (no longer produced), both with an APC 10 × 8E propeller. I and others have used the BadAss 2826-1360 on 4S with 10 × 7E or 9 × 8E propellers. The APC 10 × 7E is available in a pusher configuration if you want that. With the 10 × 8E propeller and standard batteries, Pete starts at 145 amps and slightly more than 2,000 watts, ending high speed at 120 amps and approximately 1,600 watts. With the high-voltage battery, the numbers are 162 amps and 2,400 watts, ending at 140 amps and 2,000 watts. My preferred combination is the BadAss 2820-1820 on 5S with an APC 7 × 6 Sport propeller. It consistently gives me 103-plus mph high speeds. The larger propellers are more efficient at lower rpm on our large models, but the smaller propeller at 28,000 rpm produces excellent acceleration and a slightly better overall speed result for me. It also produces a distinctive sound, akin to that of an FAI Speed model. Initial power output is 2,300 watts at 125 amps, dropping rapidly as the model accelerates. The propeller unloads a bit and the voltage drops, ending at 110 amps and 2,000 watts. Obviously, with such a variety of propeller/rpm/power combinations getting similar results, there is still some room for experimentation and improvement. A helpful tool is available on the Innov8tive Designs (BadAss Power Systems) website that provides a list of equivalent motors in tabular form from a variety of manufacturers.

Mystery Model

This Class I Short Seamew is the product of an unknown—but quite innovative—modeler, likely from the 1970s. Can you help identify the modeler? CL Navy Carrier modelers are an amazingly innovative group of individuals. I recently received this model from Mike Potter in Washington State. It is a Class I Short Seamew about the same size as my 1973 Seamew with a 27-inch wingspan. The engine is a K&B 40S using an exhaust slide coupled to a Harry Higley fuel meter with the engine running on crankcase pressure. The model is built using a modified magnesium Harter’s Proto Pan as the bottom of the fuselage, with the custom-soldered fuel tank fitting into the pan aft of the engine and flush with the top of the pan. It has a solid balsa wing and the fuselage appears to have been carved from balsa as well. We do not know who built the model, but we are assuming it originated in the Pacific Northwest in the 1970s. If you have any thoughts about who might have designed and built the model, please let me know. We would very much like to give credit to the builder and learn something about the history of the model and the modeler. The most interesting part of the model, to me, is the control system. The elevation control is a common bellcrank arrangement using two lines. The uncommon part is the throttle control, which uses torque on the solid control lines—in this case, it is the "up" line—to move the throttle linkage. Just as with a monoline elevator control, there must be some resistance to the twisting to provide proportional control movement. In the standard monoline system, this resistance, as well as the retention of the unit in the airplane, is provided by multiple fine steel wires with which the combined spring constant is much less than the spring constant of the larger, solid control line. In this model, the resistance is provided by a small spring on the throttle arm. The control line can twist freely with very little resistance because it is attached to the bellcrank with a standard steel clevis with a 2-56 thread. The control line is terminated with a threaded rod that is threaded into the clevis, allowing the line to rotate. Fortunately, Navy Carrier fliers today have electronic throttle control capabilities through the use of radio control (as I discussed in my last column) but we can still marvel at the incredible ingenuity of our predecessors, who used their creativity to devise mechanical means to achieve throttle control.