Adding Kevlar to the Underside of the Dinghy
The scratches and holes in the gel coat were filled with Bondo, the entire surface covered in multiple coats of clear epoxy. Sanding it down with 32 grit sandpaper, we prepared the hull for the new cover. We opted to use Kevlar felt instead of copper to act as a wear strip. I purchased the felt from RAKA, an excellent outfit, along with some slow hardening resin.
The Kevlar felt was very simple to lay up and draped surprisingly easy for a 1/8" thick strip. Unfortunately, RAKA had accidentally omitted the special Kevlar shears we had ordered (which they shipped to us later), so we had to use regular scissors and razor knives.
Bondo'ed and sealed. The bottom surface is ready for the pre-cut Kevlar felt once an initial epoxy coat has been applied to hold it in place.
Now with Kevlar felt. Note the split in the front where we chose to overlap. Cutting Kevlar is pretty challenging. We roughed the starboard side using razor knives and some good scissors. Once the entire mat had been saturated (and this took in excess of one gallon of resin), we waited a few hours for the resin to start hardening before trimming the Kevlar to shape. While it makes life much easier to properly trim beforehand, cutting Kevlar is much less challenging when it is thick with hardening resin (but very messy).
Kevlar in place, trimmed. After sanding down the Kevlar felt, we elected to add another coat of epoxy (~ 24 liquid oz) because the mat did not seem completely saturated (!!!) Since the excellent RAKA product had run out, we substituted a slow WEST System epoxy instead. Once we had covered the main mat surfaces, we thickened the leftover epoxy with filler and used it to fair uneven trim.
Some of the finished details. Note the overlap near the front, the reinforced drain hole in the rear. This is going to be pretty water/bombproof!
The finished Kevlar, with a second coat of epoxy. Note how the WEST system epoxy has given the Kevlar mat some red undertones... There are some weaving ripples left, so we will use more epoxy with filler to completely fair out the Kevlar. A few layers of water barrier and ACP-50 later, and the boat should be ready for launch.
After applying several layers of extra thickened epoxy (each followed by a hand and machine sanding) we painted on the barrier coats. Now only the wear strip and the anti-fouling remains.
The dinghy now features anti-fouling and is almost ready for water trials. We didn't get the Hypalon material until 2002 so the Hypalon wear couldn't be addressed immediately. However, the anti-fouling was a huge hit as the severe fouling we used to experience in the Marina no longer affects the dinghy like it used to.
Instead of having a virtual Sushi table of saltwater delights attached to the bottom, we now only foul a little on the Hypalon. I guess if we were really desperate we could have put a rubberized coating on the Hypalon as well. Ultimately, only changes in the Marina infrastructure will reduce fouling altogether (i.e. the reduction of Nitrates).
After a few more leak checks and other minor re-assembly, we were finally ready to re-launch the new and improved Dinghy.