Centerboard, Construction, Part 5: Kevlar, Biax, and Cloth

The new centerboard draped with 10 ounce cloth
Having described the traditional methods by which I shaped the foam exterior of the centerboard in Part 4, I will now, in Part 5, explain how I applied Kevlar and biaxial cloth to the leading edge of the board, and how I applied two layers of 10 ounce fiberglass cloth to the port side of the board. These applications of Kevlar, biaxial cloth, and 10 ounce cloth can, and should, be made at the same time, so that the epoxy that is used to saturate them will form a chemical bond rather than a mechanical one. For this reason, I have focused exclusively on these steps in this part - Part 5 - of my nine-part article on how I constructed a new centerboard for my Ericson 25.

The first thing I needed to do was to pull out the Shop-Vac, in order to remove all of the dust that had been generated by the sanding and shaping of the board. Below you see my buddy taking care of this job.
You'll notice that there were many cavities here and there in the surface of the board. These were the result of the foam not fully expanding within the mold during the pouring process.
You'll also notice the large chunk of foam that was missing from the head of the board. This was the result of an error I made with the electric handheld planer during the shaping process.
When you look closer at the board, you'll see even more imperfections. There were, for example, holes in the foam from the stainless steel screws that had been used inside of the mold to support the steel spine.
There were also millions of tiny pores in the surface of the board. These gave it a sponge-like appearance. I received two different pieces of advice on how to deal with these imperfections. One of my neighbors, the surfboard maker (the fellow who helped me shape the board in Part 4), suggested that I fair the surface with an epoxy compound and then sand it until it was uniformly smooth. My other neighbor, the cold-molded boatbuilder and marine surveyor I've mentioned before, suggested that I simply saturate the surface of the foam with epoxy and colloidal silica. He said that I could, at the same time, fill any of the larger holes with the same epoxy mixture after I had thickened it up a little more by adding additional colloidal silica. He said the benefit of doing it this way was that the epoxy and the cloth that I laid  on top of it would tenaciously grip the board in a mechanical bond. Moreover, the cloth itself and the epoxy within it and on top of it would form one solid chemical bond. I liked this advice from my boatbuilder neighbor, so I went with it.
Before I could do any of this work, I needed to create a good work area. I remembered that my surfboard-making neighbor had a special stand in his shop that allowed him to work on the top side of a surfboard and the bottom-side edges at the same time. In an effort to replicate this surfboard stand in an easy and inexpensive way, I laid two scrap pieces of a 6 x 6 across three sawhorses. These provided just enough room for me to have access to the edges of the board.
Adjacent to the trailing edge of the board, I set up two more pieces of scrap 6 x 6. On top of these I laid a piece of plywood. The reason? My surfboard-making neighbor had suggested that this would be a good way to create a solid fiberglass edge that would encapsulate the foam edge of the board. He said that he had used this technique during his boatyard-working days. The idea is that you allow a little bit of the cloth to extend beyond the foam. The board is there to keep it from drooping. After the epoxy cures, you have a nice, hard piece of fiberglass on one side. Then, you flip the board over and lay the cloth down on the other side, again allowing a little bit to extend beyond the trailing edge.This little bit joins with the other little bit from the other side, and this is how you end up with a solid piece of fiberglass protecting the trailing edge. The thinking behind this, of course, is that it is impossible to make fiberglass cloth lap over any sharp edge. In other words, it's impossible to encapsulate the edge by lapping a piece of cloth over it.
I'll say right now that this technique did not work for me. Maybe it was because I placed the plywood too low. I was worried about excess epoxy causing the board to adhere to the foam, so I made sure that there was clearance between the centerboard and the plywood. This resulted in the cloth drooping downward, instead of sticking straight out (on the same plane as the trailing edge). This, of course, caused problems when I turned the board over and tried to do the same thing to the other side. As you will see, by the time I had sanded down the excess fiberglass enough to make the edge nice and straight, there was no fiberglass remaining in some places along the edge that would protect the foam from water intrusion. For this reason, I ended up applying two layers of Xynole cloth on the trailing edge. This stuff really did the trick, for reasons I will provide when the time comes. For now, though, I can say that if you attempt to replicate my approach, I would not apply the Xynole at this this time. I would wait until you have applied the 10 ounce cloth to the board (on both sides).
Having gotten everything set up, my buddy and I got to work on cutting the cloth. I decided to begin with Kevlar tape. I had purchased this from RAKA, Inc. specifically for the purpose of protecting the leading edge of the board. This is an area of much abuse, and I figured that the more I protected it from abrasion, the more years of loyal service I would get from the board without experiencing the problems found in the original boards. Below you see my buddy cutting through the Kevlar with a razor knife. It was not easy to slice.
I wanted it to protect the leading edge, all the way from the pin hole to the foot of the board. The trick would be to get this somewhat unwieldy Kevlar to cooperate and lay down like I wanted it to.
Next, we cut a strip of 12 ounce biaxial cloth. This would be used as an overlay on the Kevlar. It would provide additional protection against abrasion, and it would help the Kevlar to lay down and conform to the edge of the board. I did this upon the advice of my neighbor who is the cold-molded boat builder and marine surveyor.

We then cut the first of two layers of 10 ounce fiberglass cloth. This I also did on the advice of my boat-building neighbor. In opposition to my surfboard-building neighbor's advice that I lay up four layers of 6 ounce cloth, my other neighbor urged me to do two layers of 10. That was faster and easier, and considering his advice to be sound, I followed it.
We then trimmed the cloth to make sure that it would fit just right when the time came to lay it down with epoxy.

To save time, we simply transferred the pattern we had just created out of the first layer of 10 ounce cloth to the second layer, and then we starting cutting.
Now it was time to begin the lay-up. The first thing I did was to soak the leading edge of the board with epoxy and colloidal silica. This would help to fill the cavities in the foam, and it would also help with the wetting-out of the Kevlar.
The foam soaked up the epoxy almost like a sponge.
I made sure to get it on both sides of the leading edge.

There were some large cavities on the underside that needed serious attention.
I gave them an initial dousing with the epoxy-silica mixture that I had been using.
Then, I mixed up some more epoxy and added quite a bit of silica to make it especially thick.

This is what these cavities and the others ones I found here and there really needed.

Now it was time it move on to the Kevlar and biaxial cloth.
This pot of epoxy I mixed up neat, i.e., without any silica. It needed to be as thin as possible in order to wet out this tightly-woven Kevlar.
The fact that I had slathered lots of epoxy and silica on the leading edge of the board prior to the application of the Kevlar really helped the Kevlar adhere. Nevertheless, it was definitely a two person job getting the Kevlar to fully adhere and conform to the curvature of the board. I had to apply generous portions of neat epoxy before I could get the Kevlar to lay down and behave the way I wanted it to. It was absolutely necessary to have that buddy of mine there to keep the Kevlar under control. The wind that day wasn't helping matters at all.
Even after I had gotten the Kevlar under control, I continued to apply the epoxy, just to make sure that I had fully saturated it. My boat-building neighbor warned me that there would be trouble if I didn't. He said that Kevlar was the last thing in the world I'd want to sand.
Next, my buddy and I applied the biaxial cloth. This was not as tough a job as the Kevlar, but it still required two sets of hands to get it under control. Need I say that it also required lots of epoxy? Biax is an epoxy hog.
We had to snip the biax to get it to round the corner at the foot of the board.

Once it was fully wetted-out, the biax gave the leading edge of the board a nice, clean appearance. Better yet, I knew this would make this new board far more durable that the old one.

The red marks on the biax are from a red Sharpie marker. We had used the red mark as a reference for the cut we needed to make to accommodate the curvature of the board.
We also had placed a red dot at the mid-point on the biax before the wet-out. This helped us align it on the mid-line of the curve. We also placed other red dots at other mid-points. These really helped us when we first placed the biax on the board. They also helped during the wet-out, as the cloth had a tendency to move around with each stroke of the brush.

In the picture below you can see another one of the red reference dots that I was just talking about.
Just to make sure that the epoxy had fully saturated both the Kevlar and the biax, I pushed an epoxy-loaded roller back and forth along the leading edge.

That was just a precursor, however, to the more serious work that I did with the roller on the body of the board. Pouring out globs of epoxy and silica, I tried to fill every nook and cranny that I could see. This required a lot of epoxy.

With the body of the board fully saturated, it was time to put the 10 ounce cloth down. It certainly helped that we had pre-cut this cloth.
Do you see that gallon of RAKA 127 resin and that half gallon of 350 hardener? I was just opening these up when my buddy took this picture. By the time I finished with this board, I had used almost all of this stuff up. If you take into account the epoxy that I used prior to opening this up, I would say that this was the total amount used to create this new centerboard. In other words, if you were to do this yourself, you'd need this 6-quart kit from RAKA, or you'd need some equivalent amount from MAS Epoxy or one of the others.
It took plenty of epoxy to begin to wet out this first layer of 10 ounce cloth.
I continued to put more epoxy on the first layer.
I just kept on applying the epoxy to the first layer until I was convinced that the weave was fully saturated.
Then I dropped the second layer of cloth in place.By this point, the Admiral was giving me a hand, since my buddy had already left town. This continued to be a two person job, thus my seeking of help from my other half. If she'd not come out there to help me, I believe this cloth would have gotten hopelessly wrinkled when I first tried to lay it down.
Just as was the case with the first layer of 10 ounce cloth, with this one, I continued to apply the epoxy, allowing the cloth to absorb as much of it as possible. When it started wanting to run and drip, I stopped.
About an hour and fifteen minutes later, after the epoxy and become sufficiently tacky, I came back and applied another coat of epoxy to the body of the board. Notice how some parts of the cloth, near the edges, were still not fully covered with epoxy.

I then waited an hour and a half and came back and applied another coat of epoxy. Now all of the weave was starting to disappear.
Two hours later, near the end of the day, I returned for yet another coat of epoxy. By this point, the board had a nice, glossy appearance, which told me that all of the cloth was fully covered with epoxy.

The day was over and I had successfully glassed one whole side of the board. Now, I would need to let this epoxy cure, and then I would need to sand it and clean it all up in preparation for the glassing of the other side. There was still plenty of work to do, but at least I felt like I was making some progress. I couldn't have done it without the expert advice I received from my boatbuilding neighbor and without the help I received from my good buddy who was visiting from out of town, and from my wife who valiantly jumped in there to help, despite the fact that she has no fondness for epoxy work.
This ends the fifth part of my nine-part article on how I constructed a new centerboard for my Ericson 25.

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