Desirable characteristics for a Slope Soaring flying site

Written by Dave Garwood RC Slope Soaring Column As seen in the October 2018 issue of Model Aviation.

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Desirable characteristics

A common question I am frequently asked is, “Where is a good Slope Soaring site around here?” Sometimes a favorable flying site is close by, but often there is a need to find new sites—maybe some that face different wind directions, that have flatter landing spots, or that are a little closer to home. Slope Soaring pilots are seekers—ever searching for more, better, and closer flying sites. In my February 2016 column, I wrote about flying over small hills. In June 2017, I discussed getting permission to fly on government land. In my June 2018 column, Joe Chovan described the lift characteristics of different hill shapes. Here is a checklist of features that are desirable in a Slope Soaring hill for those who search.

Slope or Grade

A hill forces the wind upward and provides the lift for glider flight. Some are steeper, and some are shallower, but we fly from hills with gentle enough grades to grow crops, to hills too steep to climb without ropes. The steepness of a sand dune—30° to 40°—works well. Shallower hills often require longer-wingspan sailplanes but might offer flatter landing areas. The steeper the hill, the more lift produced by a given windspeed. We generally want the steepest hill we can find, but one that allows access to the bottom in case we need to retrieve a downed sailplane.

Todd Herbinger launches a Dream-Flight Weasel over a gentle inland hill. It’s not a great hill, but it’s close to home and fine for practicing and learning.

Hill Height

Taller hills generate more lift than shorter hills for a given windspeed. Hill heights depend on geology, but taller is better. There are limits to this principle—mainly ease of access to the flying site at the top or on the face, and access to the recovery area below. Hills as small as a 15-foot sand dune can be delightfully flyable, while mountains such as the 6,000-foot Francis Peak overlooking Great Salt Lake in Utah are especially memorable flying locations.

Hill-Facing Direction

We want a new hill to face into a prevailing wind direction. Few things are sadder to an RC Slope Soaring pilot than living close to a perfect hill that faces an uncommon wind direction. The tools of our trade for hill facing direction assessment are a wind rose and a compass. Wikipedia states that a wind rose is a “graphic tool used by meteorologists to give a succinct view of how windspeed and direction are typically distributed at a particular location.” Search the internet for a wind rose at an airport near you, and you’ll have an idea of your primary and secondary prevailing wind directions.

A simple baseplate or orienteering-type compass can help the author determine the direction that hills face. Other pilots use a military-type compass.

Water Out Front

The fewer upwind obstructions there are to create turbulence, the smoother the air in which we fly will be. Having water in front of our hills is best. This can be a lake, a river, or an ocean. After you experience the smooth lift that is generated by wind crossing water before it reaches your hill, it’s hard to go back to bumpier inland air.

Water out front, park benches, a drive to the top, and being able to park close are benefits of a good Slope Soaring site. To avoid crowds, go early or late in the day, or even early or late in the season.

Landing Area

Here’s a Slope Soaring flying site explorer professional trick: Before you launch, figure out where you’re going to land. We want an accessible spot—preferably flat—that doesn’t beat up the sailplane and is safe for spectators and other fliers. Mowed grass is ideal, but it’s not often available at locations other than municipal parks. There are some sites where there’s no place to land except in the bushes, and then we try to hit the younger, smaller, more flexible bushes.

Here is some mountainous, wooded terrain in the eastern US. Over a hill this size, the lift would be stellar, but landing would be tricky and a lost sailplane is a lost sailplane.

Landlord Permission

It’s no fun getting kicked out of a flying area because you failed to ask for permission before you started flying. Find the landlord and ask permission to be on the land and to fly there before you take to the air. Some are concerned about people getting injured and, perhaps, suing. Explaining AMA’s liability insurance and the AMA Safety Code might go a long way to reduce those fears. It could help to have a lightweight foam sailplane to show, and to let people see for themselves that our model aircraft have no motors, propellers, or sharp edges. A Dream-Flight Alula is perfect for this and can be tip-launched for a flight demonstration, even if the wind direction is not suitable for Slope flying on a given day. A foam Slope glider is no more hazardous to bystanders than a Frisbee or a softball.

Stairs up and down the hill? Mowed grass? These are commonly found in municipal parks. Make sure you know the rules for RC flying before you launch.

Amenities

Other worthwhile amenities include park benches, nearby parking, and the ability to drive to and park at the top of the hill. You might not find all of these desirable characteristics in a single flying site, but these are the things we look for. -Dave Garwood [email protected]

Sources:

Aloft Hobbies [email protected] www.alofthobbies.com Dream-Flight (805) 845-1803 www.dream-flight.com League of Silent Flight (LSF) www.silentflight.org Wind rose https://en.wikipedia.org/wiki/Wind_rose