We used 400 grit sandpaper pads and ScotchBrite pads to rough up the areas to be primed. Then we cleaned all the surfaces well with Acetone. The prep included the HS skins and the hardstock aluminum spars. The spars were already primed but we sanded and recoated. Used the same PTI Zinc Chromate spray cans of primer. In total, 3 cans of primer were used to prime the under structure and the skins of the HS. We estimate that this added about 39 ounces of weight (in primer alone) to the HS.
