Picking a Prototype to Model

Picking a Prototype to Model

Picking a Prototype to Model

Control Line Navy Carrier

By Dick Perry | [email protected]

As seen in the June 2024 issue of Model Aviation.

ONE OF THE THINGS that appeals to me most in Control Line (CL) Navy Carrier modeling is the variety of prototypes that are available to model. Many of the models seen in Carrier competition are Martin MO-1s. The MO-1 design performs well with good handling qualities and is easy to build with a square fuselage cross section, but it is not an optimum design for Carrier, in my opinion.

Are there enough MO-1s yet? Class I and II MO-1s were flown at the 2014 CL Navy Carrier Nats by Pete Mazur, Dick Perry, Eric Conley, and Burt Brokaw. This month, the author talks about alternatives to the MO-1.

Are there enough MO-1s yet? Class I and II MO-1s were flown at the 2014 CL Navy Carrier Nats by Pete Mazur, Dick Perry, Eric Conley, and Burt Brokaw. This month, the author talks about alternatives to the MO-1.

Many who fly the MO-1 will cite its small fuselage cross section as an advantage because of the lower drag. I don’t believe in the lower drag argument, even though I’ve built many MO-1s for competition. The small cross section is still a non-aerodynamic box, which is only a small disadvantage (offset by the ease of construction), but the drag of the fuselage is quite small compared with the drag of the engine cylinder that is highly exposed on an internal-combustion MO-1.

The other disadvantage of the small cross section is the lack of internal space for a fuel tank that is large enough to complete a good low-speed flight. Although the engine-cylinder drag doesn’t exist on an electric Carrier model, the batteries need access and space.

What makes a good Carrier model? First, it should be one that you enjoy flying and that gives you a feeling of pride. A design that you like goes a long way toward making Carrier flying fun! Good aerodynamic performance is also important for enjoying Carrier competition.

I wrote about going fast in my last column. It’s basically a matter of power. The engine and lines produce the most drag, but model aerodynamics is still important. For internal-combustion models, covering the engine will make a noticeable improvement.

As an MO-1 alternative, Jo and Everett Shoemaker have a matched set of Fairey Fulmar models for Class II. This one was flown by Jo at the 2014 Nats.

As an MO-1 alternative, Jo and Everett Shoemaker have a matched set of Fairey Fulmar models for Class II. This one was flown by Jo at the 2014 Nats.

My Short SB.6 Seamew and Terry Herron’s Yokosuka D4Y Judy were very fast, with the engines well faired into the nose contours. With electrics, a sleek nose looks good and has an aerodynamic advantage, but a larger radial-engine cowling can do a better job of reducing the drag of an exposed engine cylinder on an internal-combustion model. Biplane aerodynamics pretty much eliminated them from CL Navy Carrier competition, just as they were eliminated from the full-scale aviation world—no matter how high their "cool factor" might be!

For good low-speed flight, two things are important. The model must have a large tail or a long aft fuselage to place a smaller tail farther aft for greater effectiveness. An effective horizontal stabilizer and elevator enhance control during slow flight and the stability of high speed. You can’t do without good low-speed control. For optimum slow-flight potential, once good control is ensured, the model must have a low wing loading. That means that it has a large wing area and a light weight.

A large or long tail is not hard to find in World War II-era propeller designs. Big engines needed effective tails to control the power of those engines. More power means less stability in real airplanes, as well as models. With jets, tails became smaller and noses became longer, making it a challenge to convert a jet prototype to a good-performing propeller Carrier model.

Ted Kraver is shown with his 44-inch wingspan Short Seamew Class I model at the 2014 Southwest Regionals in Tucson AZ.

Ted Kraver is shown with his 44-inch wingspan Short Seamew Class I model at the 2014 Southwest Regionals in Tucson AZ.

For the largest wing area, our Class I and II models need to be close to the 44-inch wingspan limit. I started with a collection of prototype three-views and specifications and computed the wing area for a scale model with a wingspan of 44 inches. I was not surprised to find that the majority of prototypes of fighter aircraft produced scale models with wing areas between 345 sq. in. and 375 sq. in. Structural reality dictates a consistent wing geometry among prototypes with similar missions. I was surprised to find that the smallest wing area in that range was on the MO-1. Although it wasn’t a fighter aircraft (fighters were all biplanes in 1923), the MO-1 ends up falling into the same geometric characteristics as WW II fighter aircraft.

As aircraft grew larger to accommodate attack missions with high payloads, the wing areas that would fit a 44-inch wingspan model grew smaller; thus, models of the Douglas TBD Devastator and A-1 Skyraider, Curtiss SB2C Helldiver, Grumman AF Guardian, Blackburn Firebrand, and Fairey Barracuda end up having quite small wing areas—some even less than 300 sq. in. The same was true of the de Havilland Sea Hornet and Sea Mosquito designs and the twin-engine Grumman F7F Tigercat. The Douglas SBD Dauntless was more than 360 sq. in. because of its stubby wing—it didn’t fold. The Martin AM Mauler is also 360 sq. in., with its greater area and same wingspan as the Skyraider.

The prototypes that resulted in the largest wing areas included some surprises. The Short Seamew wasn’t a surprise to me because I picked it as a Class I model in 1973 and am quite familiar with its characteristics, even though the original was a smaller model than what would be appropriate today. The Short Seamew, at 44 inches, has a scale wing area of 380 sq. in. The Curtiss SO3C Seamew, an observation aircraft, would have a wing area of 393 sq. in. Another observation aircraft of WW II, the Vought OS2U Kingfisher, would have a wing area of 410 sq. in.

The real surprise for me was the Supermarine Seafire derivative of the Spitfire. The standard Seafire falls right in with the other fighters at 350 sq. in. The low-altitude version with its clipped wingtips would produce a wing area of 432 sq. in.! I’m building one for electric power.

Either of the Seamew models can completely enclose a Class I engine, although the Curtiss Seamew would, like the Judy, require an inverted engine installation with some accompanying inconveniences in engine operation. The Kingfisher cowling can cover all but the head of a Class I engine with a 4.5-inch diameter.

The MO-1 has a very small fuselage cross section, as we know. At a 44-inch wingspan, the area is a mere 11.5 sq. in., if the radiator and windscreen aren’t included, as is the current practice. The Short Seamew, however, with its very narrow fuselage, is less than 14 sq. in. It’s the smallest cross section after the MO-1, with much better engine streamlining. With its wing through the middle of the fuselage and the small cross section aft of the cockpit, it still presents as a challenge to fit in fuel or batteries.

The fighters generally have larger fuselages to accommodate their relatively large engines (especially the air-cooled radial engines of US designs). They share a fuselage cross section of somewhere around 25 sq. in. No one will deny the sleek aerodynamics of the Spitfire/Seafire fuselage, and it has a very small cockpit behind a liquid-cooled engine. Its fuselage cross section is only a little more than 15 sq. in. With a clipped wing, that number jumps to nearly 20 sq. in., but that’s still very good compared to the round-engine fighters, and there’s plenty of room for batteries or fuel.

Future columns will discuss conversions of RC models to CL Navy Carrier use. It’s a popular practice in Fun Scale, although competition Navy Carrier requires higher strength in the control systems and the pull test is more demanding. The leadout guide introduces forces that the wing was not originally designed for, so a little more ingenuity is required, but Carrier modelers have plenty of that! If any of you are doing conversions, let me know so that I can incorporate your insights into the article.

Meanwhile, keep your tailhook dry!

SOURCES:

Navy Carrier Society (NCS)

navycarriersociety.org

Facebook Twitter Share

Add new comment