refactor ripple_stencil into separate module

handlebar_grip.scad

@@ -47,10 +47,7 @@ module handle_shape(l=0) {
    }
 }
 
-module handle() {
+module ripple_stencil() {
-    difference() {
-        handle_shape();
-
     translate([0,0,-1]) {
         for( z = [0:10] ) {
             translate([0,0,z*(LEN-5)/10]) {
@@ -71,6 +68,13 @@ module handle() {
         translate([0,0,-8])
         cylinder(h=10, d=DIAM-8, $fn=64);
     } 
+}
+
+module handle() {
+    difference()
+    {
+        handle_shape();
+        ripple_stencil();
     }
 }