Scoping out slope sites

Model Airplane News, Nov 1997 by Garwood, Dave

Where and how to find them

SLOPE SOARERS ARE SEARCHERS. They peer incessantly out the window when traveling by car, scrutinize topographic maps to find hills that aren't visible from the main roads and ask their outdoorsman friends where flyable hills might be.

The perfect slope-soaring hill would be 100 feet high, 500 feet long, rise at a 45-degree angle from the valley floor and be covered with grass (cut by somebody else, of course). Devoid of trees and bushes, it would run arrow straight, perpendicular to the prevailing wind direction, and have a paved road to the top with a sign reading, "RlC sailplane flyers welcome." And, ideally, it would be 15 minutes from your house.

That mythical hill hasn't yet been found. but there are plenty of hills that have enough of these characteristics to be quite flyable. The important properties are described in the following section.

You've heard, "There aren't any hills around here." Please put aside this concern until you've finished this article. Try to be open to the fact that there are myriad possibilities for flyable sites on landfills, floodcontrol dams, gravel pits, strip mines, dikes, levies and ramps built for highway overpasses. Are there any states that don't have landfills, highway cloverleaves or gravel mines?

I've flown from garbage dumps and highway overpasses in four states. Simply by staring out the car window, I found a soarable inland site in Elmira, NY, that had been overlooked by members of the Harris Hill LID Club. Although it wasn't a great site, it was soarable.

I found a soarable coastal site that the DownEast Soaring club in Portland, ME, hadn't discovered when I got lost trying to find one of their five known slope sites. Again, it's not a training site, but we flew there for three hours in November during the New England RIC Soaring Convention.

Oh, you live in the Great Plains, and it's flat there? Born in Ohio, I know that Buckeyes fly at strip mines and dam sites. On my way to the Russell County, KS, slope race, I saw more flyable slope sites within walking distance of I-70 between Topeka and Abilene than I've found in five years of searching in New York State and New England. When I got to the Lake Wilson reservoir, I had the privilege of flying with slope pilots who had flown that site for 20 years.

SLOPE SITE CHARACTERISTICS

Let's review the ingredients of good slope-soaring hills, and then we'll talk about how to find them.

Height. The practical minimum should be high enough to generate lift, and that may be as little as a 30-foot-high, abandoned highway overpass. The maximum is limited only by your ability to get to the top. The launch site at Mt. Greylock, MA, is 1,400 feet above the valley floor and, luckily, Notch Road leads to the top.

The l00x500-foot hill was suggested because it was likely to produce sufficient lift to fly in a variety of wind speeds, and it was long enough to fly straight for a while before having to turn around and come back. There are usually more small flyable hills around than large hills.

Steepness. Generally, the steeper the better, but a true cliff isn't needed. Many hours of productive slope lift can be found on hills with only a 20- to 30-percent slope. One advantage of gentler hills is that they're easier to walk up and down. You must actually fly a hill to find if it's flyable or not. Bring a hand-launcher or EPP-foam bouncer for this exploratory task.

Shape. Not many hills are ruler-straight. As viewed from above, a concave ridge line collects and concentrates the wind, increasing the lift. Concave ridge lines, or bowl-shaped hills, are more sensitive to ideal wind direction, but they concentrate the wind and multiply the lift when they're "working." Convex hills, on the other hand, dissipate wind and reduce lift but are less sensitive to wind direction. You'll probably have more flyable days on a straight ridge line.

Ground cover. Grass is great for walking, landing and finding lost airplanes. Bushes reduce the number of places you can land, and trees interfere with both landing and flying. Cleared land is preferable.

Upwind turbulence makers. What's out in front of the hill is as important as the shape and size of the hill itself. If trees, buildings and other hills are upwind of your hill, the turbulence they produce will disturb the lift at the hill. Upwind obstructions don't automatically make a hill "unflyable," they just make it more turbulent. Some well-known slope sites are on the coast, and this helps because they're free of upwind obstructions, but hills with unobstructed upwind terrain also exist at inland flying locations.

Access and landowner permission. You've got to get to the top to launch and be there legally to fly. Sometimes, governmentowned land is allocated for recreational purposes, but it may come with restrictions. Keep your site accessible; get permission to fly and follow the rules. Often, the land is privately owned and may be cultivated for crop production. You can, however, get approval to fly on farmland by talking to the landowner in advance. Some sites are flyable for years by working around crop schedules and respecting livestock. Don't trespass; ask first.