Centerboard, Construction, Part 7: Sanding and Fairing

Centerboard, fully glassed, yet in need of sanding
Part seven of this nine-part article on my construction of a new centerboard for my Ericson 25 concerns the sanding and the fairing that I accomplished after having applied two layers of 10 ounce fiberglass to each side of the board. This was not a difficult task, just one that was somewhat time-consuming.

I started on the starboard side of the board. This was the side that I had most recently glassed. For this reason, it had a high-gloss finish to it. This I needed to remove, so that any subsequent coats of epoxy that I might need to apply would achieve a good mechanical bond. I used a random orbital sander with 40 grit paper. Even with this robust paper, it took a lot of sanding to achieve the dull white finish I was looking for.
I then flipped the board over and began working on the port side. I had already sanded the body of the board after I had applied the cloth on that side. The main thing I needed to work on was the area around the leading edge of the board. This was where I had lapped the cloth over from the starboard side.
I started out using the random orbital sander, but I couldn't make enough headway on account of the motion of the sander. Therefore, I grabbed the 1/4 sheet sander and hit this area with 40 grit paper. I could have used the grinder, as I did on the other side (in Part 6), but at this point I was afraid of putting divots in the board, and I didn't want to push my luck.
Eventually, the overlapped cloth blended almost imperceptibly into the existing cloth.
I still had some unfinished business on the starboard side, so I flipped the board over again, and started working on those little areas that were still glossy.

One of these areas was to be found along the trailing edge of the board. It was imperative that I sand this side of the board in a consistent fashion in order to eliminate the unevenness in this area that was causing the gloss to remain.
Eventually, the board gave up the fight, and I achieve a nice, fair surface simply by sanding.
Not fully satisfied with the port side, I turned the board over yet again, and began to do more sanding.
One area that continued to give me trouble was the trailing edge of the board. This was where I had attempted to wed the layers of cloth on the starboard side to the layers of cloth on the port side.
To make sure that the trailing edge was nice and straight I would turn the board up and look along the trailing edge. Then I would lay the board back down and do some more sanding on that trailing edge.
Despite all my work, there were still some small imperfections here and there, not just on the trailing edge, but also on other parts of the board. Therefore, I wiped it down with acetone and got to work filling these small areas with epoxy thickened with colloidal silica.
It's hard to tell from the picture below, but you can get a glimpse of some of the pock marks along the trailing edge. The wedding of the cloth from the starboard and port sides had not gone so well, and now I was trying to patch things up for this unhappy couple.

Below you can see some of the other areas of the board that received some attention.

The biggest problem area of them all was on the trailing edge, at the foot of the board. Notice the foam that is unprotected by any cloth. This really bothered me. Remember that I could not lap the cloth over the trailing edge, because fiberglass cloth is not cooperative when it comes to making sharp turns.
Nevertheless, I pressed forward and gave the port side another coat of epoxy, hoping that I could seal up the foot of the board and make things better.

The next day, I sanded the board again, not only to scuff it up, but also to make it as fair as possible.
Then I flipped the board over and sanded the other side.
By the time I had finished working both sides with that random orbital sander (pictured in the background), I thought the board was looking pretty good.
Even the difficult area around the tang was looking good. I had wrapped the tang several times with cloth, and every time I applied another coat of epoxy to the board, I made sure to coat this area around the tang. Eventually, it took on a well-curved and well-sealed appearance.
Yes, the board looked pretty good, and I had almost convinced myself that this project was finished. I covered the board back up for the night and went inside. It was then, though, that those nagging doubts started getting to me. I knew that there were portions of the trailing edge of the board that were not protected by cloth. The only thing that protected the foam in these areas was a few coats of epoxy. This is not to say that epoxy itself would not have sealed the foam indefinitely. It was the thought that any nick or abrasion might allow water to intrude. If that happened, the board could end up looking just like the old board. Therefore, I reluctantly decided the next day that I needed to do some more work on this board. I needed to apply some of that high-tech cloth I had ordered long ago for another purpose but had never used. This high-tech cloth, called Xynole, was tough, yet supple. Yes, this was what I needed to wrap over the trailing edge of the board.

This was my thinking, and this was what I did, and how I did it is the subject of the eighth part of this nine-part article on how I constructed a new centerboard for my Ericson 25.

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