Gents/Ladies -- A final word (from me) on spiral easements.
You can really go off the deep end with the mathematics, calculating and plotting equally-spaced offsets from the end of your tangent in order to plot points that define the easement curve. (I used to do this in surveying class, calculating and laying out spirals on the main Cornell quad.) So don't do that. Any stiff, springy, straight item (a spline) intrinsically conforms to a least-energy curve when bent and held in place, provided that you don't over-bend it so as to kink it. One of the best items to use is a metal rail, the stouter the better. Plot your straight-track centerline and your curved centerine of a particular radius. Make your radius about 3/8" smaller, but from the same center point, such that the curve misses the straight by 3/8". Then take a yard- or meter-length of .148 or .172 rail, spike the first six inches along the end of the straight centerline in three places, so that one edge of the rail base is against the centerline. Then flex the rail (spline) by hand until the rail matches your curve, making sure that you allow enough free length to avoid a reverse curve in your spline. Spike the rail to the curve in three places over about six inches of length. Now draw your pencil along the rail base to create your easement centerline. Be careful not to move the rail as you do this --You may need to hold it down with your other hand as you draw. Resist the urge to spike the rail along the eased curve, as this can introduce unpleasant lateral centerline excursions. For curves less than 33", use a 1/2" offset. For curves greater than 45", use a 1/4" offset. Close enough for government work, as they say... Dick Karnes
