27 max airfoil thickness at about 30 of chord and lower profile secondary step on this kfm3 variant wing build. When the air stream flows over the ledge of the step some of it cascades down over the edge because of surface tension.
Also features tip plates.
Kfm airfoil flying wing. Overall dimensions chosen are to try to ensure the entire center plane can be cut from one sheet of foam board. Outboard chord has been tested until 70mm 100mm is more common. It was originally devised around 50 years ago for paper airplanes.
This begins a cycle where more air is forced down and back. 36 kfm3 variant shaped airfoil wing has flaps slats wing tip plates and airflow fences. The kline fogleman airfoil or kf airfoil is a simple airfoil design with single or multiple steps along the length of the wing.
In principle tailless model planes and flying wings can be equipped with any airfoil. Build log and maiden flight video all set to glorious music. A kfm wing uses laminated foam sheets to make a layered stepped wing.
The kfm4 airfoil gives it very stable slow flying capabilities. Powered by a 16g brushless outrunner. It is possible to use the same airfoils which are used on high performance f3b models if their torsion moment is compensated by the appropriate combination of wing sweep and twist.
Air is then eventually pushed to the front of the wing by the airstream that passed over the step. 42 scratch built foam flying wing. Yeah i just discovered windows movie maker.
There are a number of kf variations these use a combination of layers and positioning to produce a wing that can be made to emulate what are generaly considered normal wing airfoil profiles. In the 21st century the kf airfoil has found renewed interest among hobbyist builders of radio controlled aircraft due to its simplicity of construction. One of the most popular airfoils for swept wings due to low drag speed and very low re numbers you need.
The step on a kf airfoil works by trapping a vortex of air. This airfoil was designed for speed wings too but today you find even hlg tailless using this airfoil. However since the lift generated is not great it needs to fly at fast speeds not good as a trainer.
But if performance is an issue as it is the case in contest flying the airfoil should be carefully selected. The wing profile is based on a simplified kfm airfoil design kfm 2.