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Putting the O in Omega

In the last trail building post (In Search of the Perfect Turn), I came to the realization that the best turns for my trail would generally be “omega” style turns, or insloped (bermed) turns with grade reversals both before and after each turn. Unfortunately, when I initially marked and raked my trail, I didn’t incorporate grade reversals into the turns (at least not many of them) and I made the radius of many of the turns too tight. However, in addition to improving drainage and therefore making for a more sustainable trail, grade reversals also bring the legs of the omega (i.e., the entrance and exit of the turn) closer together. Or, flipping the perspective around, the grade reversals allow keeping the entrance and exit of the turn closer together while expanding the overall radius of the turn. Coincidentally, that’s exactly what I needed to do.

But I still had a couple of big questions:

  1. What is the best way to take the turns that I initially marked and raked and modify them to be the kind of turns I want?
  2. How do I ensure that the grade reversals enter and exit the turn at the optimal points for good flow?

As I stood beside one of the turns that I would need to modify, I just couldn’t visualize where the new line should be. I was somewhat limited on the uphill side by another turn, and on the downhill side I really wanted the turn to basically end at a very specific place in order to incorporate some rocks into the trail. Since I knew that I needed to expand the radius of the turn, I figured I’d start there. I measured the existing radius, added several feet, and tried to flag out a larger but consistent turn that ended in the right place. I set the center of the turn by putting several of my small irrigation-style marking flags through the eyelet at the end of a non-sprung tape measure and into the ground. I then walked back and forth along the tentative trail, setting flags at a constant distance from the center. Through trial and error I was able to move the center to the optimal location, while adjusting the radius through trial and error too.

That got me to the point where I had a 180 degree turn flagged out, or perhaps just a little more than 180 degrees to begin incorporating the grade reversals at the entrance and exit of the turn. But, after all of that effort, I still couldn’t visualize the locations for the entrance and exit of the turn. So I added a couple more flags on each end of the turn, again maintaining a consistent distance from the center. At this point I was probably approach having 3/4 of a circle flagged out, or 270 degrees but I still couldn’t quite see the line. I’m not quite sure why, perhaps in desperation, I decided to add the remaining flags to complete the circle.

BOOM! I could see it! I could see where the entrance and exit needed to be. By starting my omega with a full circle (putting the O in omega), I was able to quickly visualize the optimal entrance and exit for my modified turns. Since this discovery, I just flag the full circle every time so that I can visualize the optimal legs for the omega. Below are some pictures of two of several turns that I’ve now modified with this method. The first picture shows the classic omega shape and the second shows a different turn with the full circled flagged but the entrance and exit not raked yet. In both cases the trail has just been raked, not benched or insloped yet. The grade is about 22%.

Omega turn

Omega turn with 17′ radius

flagged turn

flagged turn with 14′ radius (tape measure is still attached to flag at center and is visible at about 4 o’clock)

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