WTF-J

The WTF-J has a Bestop Bikini and it works great…

…except at highway speeds (>50 MPH) at which point the top oscillates at random rates and acts like a spastic sub-woofer.   The guess is that the rise between the top of the windshield and the rollbar and the concave shape of the top act like a foil to create a low pressure area that sucks up the top at speed.  Once in the "UP" position, concave becomes convex, the top loses lift and is blown down forcibly by the rushing air. 

At speed, the noise of the top rendered radio useless, but the good news based on NHTSA logic is that it also obviated cell phone usage.  Despite the safety benefit, the noise precipitated a quest to fix it.

1. Velcro
   
   Plan “A” was to add industrial strength Velcro to the top of the B-Pillar roll-bar.  The idea was to have tension across the entire width of the top and thus stop-the-flop.  No joy!
   
   
2. Middle Belt
   
   Added 6 ballistic cloth "belt loops" down the center and then ran a 1" belting strip that could be tightened front-to-back between a footman loop on the windshield frame and the rollbar.  Much better, but to the question; are we there yet?  Nope!
    
    
3. Batten
    
   Had a spare piece of 1/4”
   rod and wondered what would happen if it were threaded through the loops to act as a stiffener, or in sailing terms, a batten.  Voila, the noise vanished.  (OK, it didn’t go away entirely, but it was w-a-a-y better.)  The batten worked OK when simply passed through the "belt loops," but the addition of a fixed bracket to the windshield frame and threading the batten to screw into it made it even better.  Success!

   
   

The hypothesis is that the batten both stiffens the top and, by adding a rib, eliminates the concave curve causing lift and the convex bubble that made the thump.  I also think that the batten effectively splits the top into two sections that each have less force and may be within the range of all three countermeasures and act (oscillate) somewhat independently and thus often cancel each other out.

Whatever the reason, it works!

I flipped a note to Bestop, because it would be easy and cheap to fold/sew a batten pocket into the top during construction and provide a low cost product update/upgrade.