Carlton's Cargo
Over coffee one morning, several members of the Skagit County (Washington) R/C Club (SCRC) were discussing the club's current activities. The regular club fun-flys were becoming a tad less exciting after several years of doing the same thing, and the members agreed that a new challenge was needed. After a number of "how-abouts," the discussion turned to popular equipment — notably the O.S. .40 FP engine that many of us use. It seemed there were more .40 FPs in our club than any other engine; everyone either had one or had access to one. They were being used to power fun-fly models, trainers, scale models, and a number of Kadet Seniors.
A discussion of this fine little two-stroke engine gradually turned to speculation about its ability to lift weight. Some of the older members remembered the great old Free Flight Clipper Cargo and PAA-Load events flown at the Navy Nats years ago. One thought led to another, and the result was the "Carlton's Cargo" competition.
Rules
- Contest period: January through the first of November (long-term project to allow time for building or modifying airplanes).
- Engine: Must be an O.S. .40 FP with no modifications to the engine. No restrictions on fuel, plugs, props, etc.
- Cargo: Three lead strips, each 1/4 inch and weighing one ounce (weights prepared and dispensed by the organizer).
- Official flight requirements:
- Take off from the runway.
- Fly for at least one minute.
- Make a successful landing within the confines of the field.
- Noise limit: Conform to the field's noise limit of 90 dB measured at ten feet on the muffler side.
Early Tests and Setup
At the outset we had no idea of the capabilities of our airplanes, so tests were in order. Testing began with a well-used Telemaster 40 fitted with two pods under the wings and a small container inside the fuselage. After a few tests, the same pods were used under the wings of a very light Kadet Senior originally built for electric power. These early flights immediately showed that the landing gear on these models was not able to support as much weight as the airplanes could lift.
Propeller and Pull Tests
We conducted pull tests using a digital fishing scale attached to a stake in the ground and to the tail of the airplane. Various makes and propeller sizes — 10 x 6, 12 x 4, and others — were tried. These simple tests were not very conclusive, probably because of the shapes of the airplanes used. However, a Graupner 11 x 6 emerged as the propeller chosen by most competitors.
Aircraft Used
The airplanes participating generally fell into two categories:
- Standard kit airplanes — quicker to build and to get into the air, even with modifications. Examples included:
- Telemaster 40
- Sig Kadet Senior
- Sig Kadet Mk II
- Special/custom airplanes:
- Atlas — a hybrid with 100-inch wings from a Sig Riser glider and a custom cargo fuselage and landing gear.
- A brand-new design created by a team of specialists.
- Freck's Futile Freak — the custom design that ultimately won (details below).
An unofficial trial was performed to get a feel for the field and how the airplanes would handle with cargo loaded. The Telemaster 40 (with the pods) had its landing gear reinforced; it gave us a starting point of approximately 5 pounds. From then on it was every man for himself, and the fun began.
The Field
All flights were performed at the SCRC field near Mount Vernon, Washington. The field has good grass runways: approximately 600 feet north/south and 400 feet east/west. There are wire fences at each boundary. The runways are more than adequate for the club's regular activities, including Giant Scale models.
Modifications and Handling Issues
When weight-lifting flights began, landing speeds of the cargo airplanes increased as weight increased, presenting a challenge on takeoff and landing. Fliers discovered several useful modifications:
- Reinforced landing gear.
- Larger wheels and brass bushings to improve acceleration for takeoff.
- Takeoff free-rolling wheels (which increased rollout distance).
- Shock-absorbing landing gear on some custom designs.
Despite modifications, several airplanes were stressed by the heavier loads. Increased landing speed meant more difficulty staying within field boundaries and avoiding the wire fences.
Competition Results and Incidents
- Two Kadet Seniors (built by Dick Snaer and Don Belisle) were early leaders. Weights began at about 5 lb 8 oz and proceeded upward through the contest; one of the Seniors crashed on a downwind turn with 10 lb 6 oz on board.
- The older Kadet Mk II belonging to Bud Peck couldn't get off the ground with a 6 lb cargo.
- The Atlas crashed in a too-close-to-the-ground downwind stall while carrying 7 lb.
- Standard O.S. mufflers met the 90 dB noise requirement; no exotic fuels were used and standard off-the-shelf props were installed on all airplanes.
The Winning Model: Freck's Futile Freak
- Designer: John Torrillo
- Builders: Jerry Freck and George Yewell
- Features:
- Three-piece 12-foot wing
- Shock-absorbing landing gear
- No ailerons (three servos and minimal other equipment)
- Wings covered with Micafilm; ribs capped with blue foam to form a Clark airfoil
- Wire bracing to prevent wing and tail sagging
- Dry weight: 6 lb 8 oz
- Performance: Very efficient and well-behaved in flight and landing. It sailed off effortlessly with 11 lb of cargo. Its largest recorded payload to date is 13 lb 15 oz, and many feel it could carry more.
Outcome and Future Interest
This project has been thoroughly enjoyable for the entire club. Several neighboring clubs have expressed interest in holding similar challenge meets in the coming year, so perhaps we have started something new in the R/C community. It sure has been loads of fun. Anyone who wants further information is welcome to contact me.
Carlton Molesworth Box 771 Mount Vernon, WA 98273
Transcribed from original scans by AI. Minor OCR errors may remain.
