FLOAT DESIGN THEORY – RC Plane Float Design
Placing a set of floats on your current plane may prove to be quite an advantage by further extending your fight experience and potential. Flying off of water and landing back on it takes a few practice runs as there are some differences. Floats are quite easy to design and build yourself, however it is very important to get all the dimensions and theory correct. This will improve your float flying experience.
Float Mount Angle to Wing Center Chord line
The floats are mounted 2 to 3 degrees negative to the wing chord datum line. This insures lift during takeoff assisting in getting the plane on step.
The Float Step
The step is located on the bottom surface of the float. Its location is where the float changes in height. The step helps reduce drag on take off or landing. With a step and increasing angle after the step, the aircraft is able to rotate during takeoff.
The float set must be mounted with the step slightly behind the airplanes center of gravity. Never forward of the CofG. From the step forward the float is designed with an upward slope of 3 degrees. This is until the curved front section of the float. Behind the step, it is common to have another 3 degree slope up to the rear of the float.
Props and Thrust – RC Plane Float Design
Float planes require aggressive hauling power verse top speed. It is often required to prop up in diameter one size to achieve the required thrust for take off. In addition to increasing the diameter, it may be required to reduce the pitch one size for a reduction in load.
Never use wooden props when flying off water. They may break apart rather easily after ingesting water and become very dangerous.
Water rudders are important for taxiing on water. Without them it is very difficult to taxi with an air rudder only. It is in the best interest to install at least one water rudder on one of the floats. Two water rudders where one is mounted on each float would be the ideal setup.
It is quite common to use part of the tail dragger assembly for mounting the floats. More specifically the front wheel set. Generally, the front wheels may be removed and the remaining assembly is adapted for mounting to the floats.
The rear float mount location should approximately be one half of a chord width behind the main wings trailing edge.
Float Design Calculations – RC Plane Float Design
The calculations have been made easy by use of an online calculator. The Calculator will provide the dimensions as noted on the drawings below listed from letters A through G. The input values are the wingspan. This is from wing tip to wing tip. The prop to elevator hinge line. Lastly the prop to the center of gravity on the main wing. To use the calculator follow the link by clicking on the photo.