Contest Gas Model (oz15487)

About this Plan

Contest Gas Model. Free flight power model. Wingspan 96 in.

Note this is not a full size plan. This is a scan of the article and drawings as they were first published in the pages of Air Trails, September 1937.

Note the original article scan here is thanks to Mary from RCL pages at: https://rclibrary.co.uk/title_details.asp?ID=1864 and the plan file is from https://www.golden-era.cz/contest-gas-model-by-frank-ehling/ which is an excellent page and has the full text of the article along with some nice model pics. Highly recommended.

Quote: "Contest Gas Model. A proven design that has been a consistent winner at many meets. By Frank Ehling and Gordon Light.

A gas model must be fundamentally sound in design and construction to withstand the wear and tear of flying. The fact that this model is recommended by Frank Ehling, its designer and builder, is proof that it fulfills this foremost requirement. His many years of experience with gas models has taught him what features to incorporate in a successful design.

Other than simplicity and durability of construction, Ehling makes the following recommendations for gas models: The wheels of the model should be placed forward of the propeller, to prevent damage to the model in the event of bad landings resulting from poor adjustment or from hitting an obstacle and diving to the ground. A moderate-thick wing section should be used. It produces a slower flight under power and a better glide than excessively thin or thick airfoils. The ignition system should be carried in the bottom of the fuselage for a low center of gravity position and it should slide backward or forward on a track inside the bottom of the fuselage for easy balancing. The model should be finished with clear dope to give a transparent wing, with color dope used for the outline or scallops on the wing. This color combination will keep the model in sight the longest possible time.

Modelers in general agree that these are necessary features for a successful gas model. This ship has all these features. And as you proceed with the construction you’ll realize how thoroughly the design has been worked out.

Fuselage: The cross section of the fuselage is rectangular except at the nose, where the motor is faired into the fuselage. 1/4 x 1/4 inc hard balsa longerons and braces are used throughout the fuselage unless otherwise noted on the drawings.

The motor mount is cut from a piece of bass 3/8 x 3-1/4 x 14 in. This Motor mount is cemented to the inside of the upright members of the fuselage. It is reinforced with auxiliary cross braces and hardwood corner angles.

The front of the fuselage is faired by cutting 4 curved pieces from 1/4 in flat balsa and cementing them to the top and bottom of the longerons. 1/32 birch plywood covering is used to cover the bottom of the curved part of the nosing. The motor is cowled in with 2 pieces of aluminium cut to fit over the 1/4 in formers. These aluminium pieces are cut to fit the motor and should allow for minor adjustments to the motor. For “servicing” the motor the cowl can be removed.

An inspection door is made from 2-ply 1/16 sheet balsa. The location and size of this door is shown in the drawing. The door hinges are patches of adhesive tape and a small wire catch keeps it in position.

At the rear of the fuselage, 2 additional longerons are built into each side of the fuselage. These longerons extend back to the rear tip of the fuselage, where they are joined to the bottom longerons with a small block cut from 3/8 sheet balsa. The 2 top fuselage longerons are cut off at the front of the elevator. The tail surface itself is carried flat atop the fuselage on the half longerons which have just been added.

Motor Installation: The complete ignition system is carried in a balance tray, which is placed in the bottom of the front of the fuselage. This balance tray is built up from 1/8 flat balsa as shown. Hooks are cemented to the sides of the tray and rubber bands fit over the top of the tray to hold the batteries, coil, etc., in position.

The motor is mounted to the bass motor mount with small wood screws. The front of this bass motor mount is cut away to receive the motor and gas tank.

Propellor: A 16 inch medium-pitch propeller is shown in the drawing. It is cut from a block 1/2 x 1-1/2 x 16 in. Basswood is the easiest wood to carve. But any other variety mahogany, cherry, etc, may be substituted. The block is first cut to shape, using the full-size template of the blade shape. Next, it is tapered to 1/8 in at the tips from 1/2 in thickness at the hub. The propeller blades should be cut to an airfoil shape cross section... "

Supplementary file notes

Article.

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