Flying on a Budget

2 min read

Still saving for your PPL? No worries, you can apply insufficient right rudder in a first person view RC plane too!

I've recently been into flying FPV. My best design to date is a converted balsa and monokote 16" Guillows FW-190. I am not the first to do this RC conversion, but mine is possibly the coolest for its unique features and manufacturing techniques. "Wolfbat" uses several neodynium magnets to mount the wings and nose. These serve as break points in a crash to protect the balsa frame. In addition, the nose is an ultra thin single-perimeter 3D printed part, which acts as a crumple zone during bad crashes. This has saved my frame countless times, which is easily the most laborious part to repair or rebuild. I will highlight some of the unique manufacturing processes here.

//Structure

Wolfbat's frame is a die-cut, balsa wood, semi-monocoque scale model of a WWII fighter. Building these frames is less challenging than you would think. It's recommended to use a foamboard, sewing pins, and wax paper or some transparent non-stick material to layup and glue the parts together directly on the plans.

The frame was finished with clear Monokote from Top Flite, a scratch and puncture resistant plastic wrap. Monokote has a heat-activated adhesive side. Oversized pieces are cut, tacked in spot, then sealed around the perimeter. After applying the wrap, a heat gun was used to shrink and stress the skin taut. The stressed skin strengthens the balsa wood frame for a stronger, stiffer plane.

//Vacuum Forming the Canopy

The Guillow's kit comes with a canopy, but I made my own to act as a closeout for uncovered parts of the fuselage used to access electronics. To fabricate the canopy, I built a vacuum forming table and used .02" polyethylene (PET) plastic. After heating the PET sheet in the oven, I pressed it onto a scaled 3D printed positive of the canopy. The result is removed with an X-acto knife.

//Flight Surfaces

Wolfbat's ailerons and elevators were 3D printed with natural PLA, consisting of just two 0.15mm cross-hatched bottom layers supported by ribs. This was done to minimize weight.

//Tail

The tail is 3D printed and 1 perimeter thick. It must be extremely light as the FW-190's tail boom is very long compared to its stubby nose and radial engine, so tail mass has an especially strong pull on the center of gravity. The Center of Gravity needs to be close to the nose and well forward of the wing center for stable flight. The tail is attached without glue to allow replacements.

//Crumple Cowl

The cowl is printed 1 perimeter thick, making it quite delicate to remove and process, however this makes it perfect for absorbing steep crashes. The cowl is mounted with 0.25" neodynium magnets to allow it to break up for landings and less violent crashes. I have flown Wolfbat vertically into the ground and had it back up flying in a few minutes after replacing the nose with a spare.

The crash ^ The result v

Frame was fully intact!

Instructions to build your own: