Originalmente inviato da RCTRIKE 1980  On a Rogallo wing you should be able to get the proper CG by using an online calculator for MAC, CG depending on the type of wing you have. Deltas, Rogallos mainly are super easy. Google "Finding MAC/CG of a delta wing. You want to balance your model ahead of the CG, so that your model does not do the famous flip backwards, a sign of inproper CG balance and or a heavy wing. It is also best to design the frame so that the main weight is concentrated very close to the center of mass and this be aligned vertically with the Wing CG, you don't want a model that pendulums crazy, with moment arms or weights at the far ends. The model should hang solid close to the CG and preferably without the assistance of adding weight to compensate for unbalanced CG.
For a trainer first time DIY Trike, it is best to have the wing sit heigher but not to high as this affects stability. Servo control at the rear, typical weight shift control, will place a demand on the servos, use Metal Gear ones, and place them below the Trust line to aid in dynamic stability. Placing servos too high will throw off the lateral and more importantly for/aft balance, especially if your wing is a heavy Rogallo style.
Ideally you want to balance the trike center of mass with the wing's CG. Both of these CG points should align vertically. Set the motor thrustline level with the airframe and adjust the wing angle of attack to about 10 degrees to start off, if the trike does not want to take off easily, make gradual adjustments to the wing angle of attack. until you get consistent lift.
On Rogallo, kite like sails or tunnels, it normally takes more runway to get the loose sail to fill with air before lift off, These are not very efficient wings but they work, and it should give you an indication of where to make adjustments. Do not try to fly the model on the first test hops, not flights!, if required, make gradual adjustments to the the CG balance by shifting, hopefully slightly, the battery whcih should be originally and ideally directly below the CG of the wing, hence being the heaviest item in the model.
Excusa, no parla Italiano molto. |