Thursday, March 17, 2016

Fabricating batten pocket protectors of epoxy and fiberglass

When I bought my boat, I heard that the mainsail might last me a year or so and, when I had managed to install the mainsail and slid the battens into place, found that there seemed to be missing pieces in the hardware to keep the battens in place... and the remaining bits of plastic were falling apart. Parts for the existing hardware seemed to be unavailable and the after-market updated stuff would cost about $1000 for my sail! So... I tried to make do with what I had, I tried following the advice of some experts, I tried buying some simpler hardware... but none of this worked well. I thought of making something of glass and resin and machining it... then wondered: could one create super strong and effective parts without a mold or much machining?

The key to making a glass/resin part as strong as possible is to completely soak the glass cloth with resin so no air remains while using as little resin as possible. So.... I took enough glass to make a pad a quarter-inch thick and six inches long. This took twelve feet of cloth! Then I laid it out on blue tape
 and soaked it with slow-setting epoxy. I left it unfolded at 3" x 12" as I didn't think I could massage the epoxy through the full thickness, then folded it into 3" x 6".

I found a piece of stainless steel that nearly matched the dimensions of a batten and taped it into the right position on one of these packages, then taped the other on top. This whole thing goes in a plastic garbage bag to contain any resin drippings.

Now, how to squeeze the remaining air out of the packages, to squeeze the excess epoxy from the parts, to form the parts around the batten form? Well, I had some scrap foam and used a piece above and below, figuring they would give good and even pressure. The whole sandwich is compressed under a press created from a drawer, one of the companionway hatch boards, and a bucket of water for a couple hours until the resin has set.

This worked pretty well,

and with a bit of work with the belt sander and a drill I had impressively strong and (I think) attractive pocket protectors that have been working well for a few weeks in seriously harsh conditions.

Normally, the parts at the ends of the battens were failing every ten or twenty hours, but we've had no breakage in over a hundred hours. This is very good!

Making this part right took two failures before the first perfect part. Too little glass resulted in a thin piece...although it probably would work. Another attempt had the batten form knocked askew, but extra tape and care eliminated that problem in future tries.

And I don't think these nice new parts had anything to do with my first major sail disaster earlier this week... I think THAT was due to a weakness I tried to get fixed by a pro last year, then spent time on this year... but I only fixed one of the two weak spots and... well, more on that later.


  1. You do amazing work. I could never have imagined you'd be out at sea fabricating essential parts. You did a great job keeping that sail going.

    1. Too bad it had such trouble a couple weeks later, but that was a separate issue. Alas!
      Just bought a sailrite sewing machine today, as well as a used sail. Together, these should allow me to handle ANYTHING.