Building an Experimental Airplane, The Vans RV-7A | EP2.2 Main Spar and Tie Downs - Ryan Flys Watch in HD on YouTube! Share on Facebook! Riveting nutplates to attach fuel tanks, access hatches, and other items continues. Then, I create the tie down brackets that hold the eye-bolts that hold the plane to the ground. This requires some precision machine work to make spacers and get the pieces mounted correctly. The parts are made and assembled, the hole for the tie down eye-bolt is tapped with a 3/8" - 16 tap, and then everything goes into the booth for priming.