Fastest Models Flying; DS Sailplanes Nearing The 400 MPH Mark
Posted on October 22, 2009 by aaronredbaron
With all of the fancy technology available today in the hobby of RC flying, one might assume the fastest models flying are turbine jets, pylon racers, or something with a motor on it, but that is not the case. Only in the last decade has a new form of RC flying captured all the (unofficial) speed records. DS, short for Dynamic Soaring, has been in many bird’s bag of tricks for eons, but it was only in the late 1990’s that sailplane legend Joe Wurts discovered it could be done with a model.
What is Dynamic Soaring?
According to Wikipedia, “Dynamic soaring is a flying technique used to gain kinetic energy by repeatedly crossing the boundary between air masses of significantly different velocity.” (click here to see Wikipedia’s article about Dyanmic Soaring) What does this mean? With birds, the most common example is the Albatross, and understanding how they Dynamic Soar helps describe how models can do it. Albatross are able to travel thousands of miles across the open ocean without flapping their wings. Close to the ocean, the air is moving slower than it at a slight altitude. A shear layer is where the air masses are traveling at different velocities. Albatross are able to glide in the desired direction close to the water where the air is stagnant, and before they loose all their airspeed they swoop up through the shear layer, exposing their wings to the oncoming wind, producing lift and causing the bird to climb. The Albatross will then turn back into the slower air and trade the altitude it has it has built up for airspeed to glide further in its desired direction. By swooping in and out of the the shear layer again and again, the Albatross can harness the wind’s energy to fly vast distances without flapping.
How Can A Model DS?
In the case of radio control sailplanes, we begin with slope soaring. Most flyers are familiar with conventional slope soaring, where a slope, optimally with a concave shape facing into the wind, causes the oncomming mass of air (wind) to move up and over the hill. We can ride this updraft indefinitely on the front side of the hill, but the back side of the hill has always been considered a danger zone where you would never fly. No longer. Armed with the knowledge of how Albatross can DS, modelers began looking for slope soaring spots with a clean ridge along the top. They also needed a clean backside that dropped away from the ridge. These ridges produce a predicable shear layer that can be flown with an RC glider. To start, the pilot flies the glider high up on the front side to build altitude. Turning the glider with the wind, the pilot guides the glider through the shear layer, and dives down behind the ridge into the back side. The glider builds speed and the pilot uses this airspeed to bring it back up through the shear layer. As the model enters the shear layer it encounters significant headwind; this is where the pilot rolls to expose the wings to the oncoming wind and pulls back on the elevator. Done correctly, passing in and out of the shear layer launches the glider back down into the back side with more speed than before, and the cycle can then be repeated. Without a body to break, such as a bird or a manned glider, our models are only limited by the strength of the airframe and hardware, and the skill of the pilot. At first flying into the backside was sort of novel, but the tremendous speed potential soon became apparent, and gliders were being pushed to the limit to explore the envelope, and blowing wings apart left and right.
Breaking Speed Records
Breaking the 200 mph barrier proved this type of flying was meant for speed, it was a goal many flyers sought and many sailplanes crashed trying to reach. According to Dave Reese of ReeseProductions, the 200 mph barrier was broken on May 24, 2003 with a 15 lb purpose built model called the MoFo. It wasn’t long after until more and more flyers were breaking the 200 mph barrier with more stout models built to handle the incredible demands of DS. Developing incredibly strong composite airframes purpose built for DSing was critical to breaking speed records. It wasn’t until December 2, 2006 that the 300 MPH barrier was broken by Kyle Paulson. ReeseProductions offers DVD videos of Sailplane action, and the LiftTicket video features film of the 200 and 300 MPH barriers being broken. Its only been three years since the 300 MPH mark was passed, and now we are creeping up on the 400 MPH mark. On March 9, 2009, Spencer Lisenby set the current record of 392 MPH, as seen in the video below. Flying a 400 MPH sailplane is not for everybody, but for those who feel the need for speed, you can leave your powered model airplanes at home.
Click here for the complete list of DS speed records
Click here for the RCGroups DS forum
Click here for an article about getting into DSing
Click here to see Soaring USA’s listing of composite DS gliders
