CL Scale
Bill Boss, 77-06 269th St., New Hyde Park NY 11040
THE BOEING B-29 Superfortress had various assignments during its life span and is the main subject of this month's column.
The B-29 was based on an improved version of the B-17, with special pressurized sections for the airplane's crew. It played a major role in the Pacific theater of operations, was used for bombing raids, served as a refueling tanker and as air-sea rescue, and was used for photo and weather reconnaissance. It was even used in the early tests of rocket-powered aircraft that were dropped from the belly of the airplane.
The Superfortress will probably be best remembered as the airplane that dropped the atomic bombs on Japan during World War II. The B-29 known as Enola Gay dropped the first atomic bomb, "Little Boy," on the city of Hiroshima on August 6, 1945. A second, lesser-known B-29, Bock's Car, dropped a bomb on the city of Nagasaki on August 9, 1945.
The B-29 featured this month is the work of Dennis Slater (Chicago IL) and has been painted in the color-and-markings used on the airplane "Thumper," of the 870th Bomb Squadron, 497th Bomber Group.
Dennis's B-29 was built using a vintage Aristo-Craft® kit, which was later produced by Kyosho® with no noticeable changes. Many of the old-timers in Scale will probably remember that the frame of the airplane was made entirely from die-cut plywood and hardwood parts.
Dennis covered the frame with sheet and strip balsa, then covered the airplane with .75-ounce fiberglass cloth and Z-Foxy®. He used auto primer for paint and 21st Century® products with graphics-tape panel lines and glue-dot rivets for surface detailing. The "Thumper" nose art was hand painted.
The entire crew of the model—manning the nose, cockpit, navigator/radio stations, gunner, waist blisters, and tail assembly—are modified and repainted full-body action figures, courtesy of the local Kmart® toy department. The action figures add a great deal of realism to the model.
The model has an 82-inch wingspan and is powered with four O.S. Max .30 engines turning four-blade APC propellers that are used for static appearance and model flying. The engine throttles are controlled by a standard three-line control system.
The features of dual bomb-bay-door operation and the dropping of bombs one at a time from the two bays is controlled via electric (not electronic) servo operation.
Dennis explained that he prefers the standard three-line throttle control over the electronic systems. Although the electronic systems provide control regardless of line tension, he said he prefers the feel of the three-line system.
Another operational feature of the model is a nose-wheel brake (from Du-Bro) that is operated by full down of the elevator. The brake greatly helps control the model while it’s on the ground and bring it to a full stop during the execution of the taxi lap.
Dennis removed the electronics from standard servos (he has used several different types), leaving the servo motor and gear train. The idea for this setup was taken from the January 1998 "Control Line Scale" column that featured an electric servo setup used by Joe Scrozyk (Philadelphia PA).
Dennis has modified the setup by using standard double-pole/double-throw switches (DPDT) rather than the momentary operating type discussed in that column. He has also added momentary push-button (PB) switches for a more positive control of the servo circuits.
The momentary DPDT switches always come back to the center off position, which may be confusing if you don’t remember the last operation. The standard DPDT switch stays in its operated position until thrown again, and the circuit is controlled with the momentary PB switch.
Some modelers did not see the January 1998 column or might be new to the idea of sending battery juice up the flying lines, so I am repeating the diagram in this column to show the addition of the momentary on PB switches.
Operation of the system is rather simple. A battery supply of 36 volts (four nine-volt batteries in series) is applied to the center terminals of the DPDT switches. As the diagram shows, the outer terminals of the DPDT switches are cross-wired, allowing the battery polarity applied to the servos to be reversed, operating the servo in opposite directions.
Dennis learned that the 36-volt supply was necessary to overcome the resistance of the nylon-covered .027 stainless-steel fishing line used as insulated flying lines.
The flying-line resistance dropped the voltage at the servos to approximately six volts—more than adequate for good operation of most standard-type servos.
If you use heavy-duty or very light servos, you might want to experiment with the level of the battery-supply voltage.
The bomb-bay-door servo is set so its operation covers the full 180° of throw for opening and closing the doors. Dennis noted that it’s a good idea to put some spring-strain relief on the doors in the closed position so you don’t overpull them shut.
The bomb-drop servo is set so that the throw starts from the center of the servo travel, allowing the bombs in each bay to be dropped one at a time.
All of the linkage to accomplish the bomb-bay-door and bomb-drop operation is made as simple as possible. Most of it is light, flexible Sullivan golden cable and control horns.
The 1998 column showed a picture of a small aluminum utility box containing the switches that were attached to the three-line handle.
With this electric servo system, all connections between the battery supply, flying lines, handle, and the airplane’s three-line bellcrank and leadouts must be insulated from each other.
Deans-type connectors can be used for connecting the battery supply to the insulated flying lines, and the flying lines to the servos in the model. You can find the batteries, utility box, and switches at your local electronics-supply store.
I will be more than happy to supply anyone with more information about making the insulated line connections; just send a self-addressed, stamped envelope to me.
Fred Cronenwett (18375 Ventura Blvd. #173, Tarzana CA 91356) has written a book titled Control Line Scale Modeling, which covers line-connector makeup and the use of electronic systems, as well as much more worthwhile information about Control Line (CL) Scale modeling.
Workshop Hint: This idea came from the Bay Area Airplane Club (Bay City TX) and was found in the Indy Sportliners newsletter.
The writer’s favorite material for replacing Lite Ply is doorskin. You can purchase this at your local home-building-supply store for approximately $5. The sheets are 36 inches wide, 80 inches high, and 1/8-inch thick.
The writer notes that he has used this in place of Lite Ply in fuselage sides, hatches, and servo mounts, and he has never had a failure.
Please send ideas, notice of upcoming CL Scale events, contest reports, and photos of CL Scale activity to me at the address at the top of this column. MA
Transcribed from original scans by AI. Minor OCR errors may remain.
