The factory nonskid used on our boat is integrated into the negative mold of the outer hull and produces a nice, uniform diamond pattern. Of course, I don't have a negative mold and I doubt the pattern material is inexpensive. I could create a mold from the existing surface of my boat, but that fails on the "relatively easy" test. A molded-in solution just wasn't likely to work.
Searching the internet (in addition to all the people who have used Awlgrip and Kiwigrip), I found someone who mentioned that a few production boat builders run a roller over a curing gelcoat layer to produce a nonskid pattern. This sounded like an interesting approach and, if we could figure out how, might be an easy solution. So we gave several variations on this theme a try.
The first attempt consisted of applying a layer of gelcoat, waiting for it to tack, and then using a fine nap roller to see what would happen. In the same coat, we also used a chip brush to stipple the gelcoat. At first it wasn't tacky enough, and the gelcoat would flow out relatively smooth. As it continued to cure, we were able to get a pattern from both the roller and the brush. The roller ended up producing what I would equate to a very fine orange peel type of texture, and the brush version was a little more pronounced version of the same. Not too bad, but we didn't think this would be nonskid enough.
Since we liked the brush stippling result better (but figured doing that by hand would prove far too tedious for a larger surface), we went back to the local big-box hardware store and looked at various brushes and rollers used for wall textures. We found a special texture roller from Wooster that we thought would provide a more brush-like stippling effect but with the speed of a roller. The roller has small, coarse plastic loops of material that should do the trick.
With our new weapon, we tried another test. This time I thickened some gel coat with fumed silica. It was thicker than normal but would still flow fairly well. Once it started to set up, we used the new roller as well as a brush for two new test cases. This time the pattern didn't flow out as much as created a more aggressive nonskid pattern. The brush was still more aggressive of a texture compared to the roller, but not by much. With the speed that we should be able to accomplish this texture, we think we found a winner. I sprayed a coat of PVA on the gel-coat so it would fully cure. Once cured, we broke out the hose and bare feet and tested the options. The thickened roller approach was the winner. It provided good traction while not feeling uncomfortable on bare feet (the brush stippled version we found to be a bit more "pokey").
|Nonskid tests. Thickened gelcoat on left, earlier attempts on right.|
(Purple hue is the PVA during cure)
The next morning, I did a little destructive testing of the test panel. We did the layups in about the worst conditions we figured we would encounter during the actual layup, and I wanted to know how well it did. After jumping up and down on the panel a bit more, I drilled and cut a hole in the panel with a jigsaw and it looked good. Since I left the raw edges of fiberglass on the panel, I then attempted to pull apart the layers with pliers. This is where things didn't go as well. I wasn't able to completely separate the plies, but I was able to pull a significant piece of one layer of the biaxial cloth apart. Despite the look of a pretty complete wet out, it seems that the layup was dry in the middle of one of the heavy layers of fiberglass cloth.
I know this #1708 fiberglass cloth can be difficult to wet out. I thought I had taken extra steps to help saturate it with resin, and it did look good when I laid it up (nice and clear), but I guess it wasn't good enough. I'll have to increase the amount of resin applied before I apply the cloth. Glad I found it now and not after building the whole top.
The day ended with final preparations to the mold (making sure things won't stick to anything it shouldn't) and my poking those holes in the foam. I ended up cutting down the size of the hole poking tool because the larger version was difficult to pull out of the foam panel, and then I bedded the nails in resin after finding they were pushing out the back of the board. Hopefully tomorrow we will start assembly of the actual top.