The Bush Beast 4 is my latest DIY bush plane. I have tried to take what I liked about my previous designs and tried to improve it. This plane has larger control surfaces and larger flaps than previous models. I also made a new landing gear design based on Mike Patey’s Scrappy plane. Of course, I still have all the features of my previous version, including reverse thrust, a DIY light system, and also a DIY gyro stabilization system to make it fly stable in high wind conditions.
The plane is built out of balsa wood and covered using iron-on plastic film. It has a wingspan of 1.3 meters and a total weight of 1850 grams including the battery. The wing chord is about 230 mm, resulting in a wing area of 30 dm^2 and a wing loading of 60 grams / dm^2. That is actually quite high for a plane designed to fly slow, but I still think it workes great, thanks to the large flaps.
I use 4 cell Li-ion batteries with 21700 cells. I currently use Samsung INR21700-40T and Molicel INR-21700-P42A cells. They perform very similarly. I get around 15-20 minutes of light time on a charge. That is when performing a bundh of takeoffs and landings, as well as some aerobatic flying.
The EMax GT-2820-06 motor with a 12×6 propeller pulls just over 30A with a fully charged battery while producing around 1600 grams of static force. The motor is driven by a BLheli32 ESC that allows reverse thrust. Reverse thrust is a fun feature that can be used for breaking after landing, and also ground maneuvering of the plane.
This plane is a totally improvised custom build by me. I don’t have any plans for it, and I will probably not make any. But feel free to be inspired by it and try to build something similar if you want!
This plane uses a custom DIY gyro stabilization system. It consists of a Teensy-board reading the SBUS-stream from the receiver and data from a MPU6000 IMU. It then mixes in some gyro with each of the signals and then creates all the servo signals. This is based on the same system I made for the BushBeast 3
The bush wheels I use are spare wheels for the Durafly Tundra from HobbyKing. They are made from a very soft foam material. I think they work very well, but unfortunately, they get worn fast and don’t keep the shiny look for very long. I made my own 3D printed hubs for them. The shock absorbers are 130 mm long, made for RC cars, from Banggood.
I don’t have any plans or building instructions for this plane. This plane is just a one-off build I made for myself. Mostly improvised. But I have a rough sketchUp CAD file of the plane as well as all the STL files for the landing gear here: Bush Beast 4 files
Here are some more detailed images. Click on them to make them larger.