Neptune (oz6717)

About this Plan

Neptune. Free flight seaplane model.

Quote: "A semi-scale gas model flying boat ...original drawing by FC Tuxworth traced by Paul Plecan." Note this is a low resolution plan.

Direct submission to Outerzone.

Update 16/3/2025: Added article, thanks to RFJ.

Quote: "Hydro gas models that really work are scarce. This Class B job is engineered for foolproof water take-offs and consistent flying with minimum repairs. Neptune, by Fred Tuxworth.

ANY model builder who has built and flown or even witnessed the flight of a successful model seaplane will undoubtedly say that it is the most interesting form of model flying; yet apparently it is the opinion of most model builders that the chances of getting a model seaplane to fly are slim. This opinion may be founded upon observation, but it is not necessarily true. Most model seaplanes at present are converted land plane's, and these usually do not give very consistent performance even if successful. There are several reasons for this, the foremost of which is probably an inadequately protected ignition system.

After several only partially successful plans had been devised and tried, this model builder finally resorted to designing a model - a seaplane from the bottom up with a dry ignition system as the prime objective. Even then the dual-purpose idea was not forgotten, for a retractable landing gear was installed. Only a few flights were made with the model as a land plane when it was decided that it was a shame to waste a successful seaplane on land with the chance of scarring up the bottom ever present. The wheels from then on were used only to demonstrate that they would actually retract, and finally, about a year later, when the model was rebuilt, the landing gear was completely removed as undesirable weight and dummy balsa wheels were cemented in the wheel wells merely to plug the holes.

DESIGN FEATURES: The model as it stands at present is one that was originally designed after quite a bit of experimenting with model seaplanes, and it has since undergone several changes. The flying-boat type was adopted for several reasons, one of which is stability on the water. No matter how faulty the adjustment at the take-off or how hot the landing, the model has all but a very few times ended top side up. The position of the motor and the shape of the bottom were designed to eliminate all possibility of spray striking the engine and propeller. It is obviously desired to keep the engine as dry as possible, but it was surprising to discover that enough spray on the propeller disk would cause the rpm to drop just enough to keep the model from getting off.

The high aspect ratio (over 9) is used, because large boat designers have discovered it to be advantageous for the take-offs; and the large stabilizer (35 percent) with the inverted airfoil is used to offset any longitudinal instability which might be caused by the short tail moment arm. Twin rudders were decided upon to increase the effective size of the stabilizer and to help disguise its size. The ailerons are to aid in making lateral and directional adjustments, because washing in or out the heavily doped wing after completion is very difficult. The method of attaching the wing float was adopted as only a temporary measure, but it proved so successful that it was never changed. The first two flights of the model were made from a small pond, with both landings in a plowed field. No damage resulted. One float has even been knocked out of position on a take-off, but instead of interfering with the take-off it merely dropped completely free on the next impact with the water, and the model took off unhindered.

If you have never tried a model seaplane, you should. It isn't at all difficult. The take-off, though longer than that of a land plane, is much more interesting; and, like the landings, it is practically free of the danger of crack-ups. The flights can be as long as the body of water. Even should the model be forced to come down on land, it usually fares better than a land plane because of the turned-up nose and the lack of projecting landing gear.

CONSTRUCTION: The builder may at first be discouraged by a wood-covered hull. There is no cause for this, for it really isn't difficult. The hull is not planked, but merely covered with two-inch widths of 1/16 soft sheet balsa. This is made possible through the use of a large number of light formers. It is quite easy to form the covering, because they are close together. They also serve to make many water-tight compartments, almost any one of which would keep the entire model afloat if necessary. If in any place the hull curves are too sharp for wrapping a large sheet, short lengths of soft 1/8 sheet may be used between any two adjacent formers and sanded to shape later. This method is also used for repairs. Soaking the wood with water and pinning it on the hull to dry before cementing will also help on some of the sharper curves.

The hull is built in halves. The first half is completed, including the covering, before removing from the jig board. A small jig board just large enough to take the frame will make maneuvering easy while covering. The first half, because of the covering, will not become distorted when it is removed from the jig board, and the second half can be built directly upon the first half..."

Supplementary file notes

Article.

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