Boatbuilding Blog

September 17, 2014

Minor Hull Patch

Filed under: Building - Painting — tomlarkin @ 1:57 pm

I pulled the Coot out last month to wash the bottom and touch up the bottom paint. Right at the waterline, back about four feet from the bow there was a half-inch divot gouged out, with bare plywood showing, and a crack a few inches long running aft of the hole. It looks like I hit something hard, maybe a bolt head mounted on something heavy. Water oozed out of the crack when I pressed on it.

While the boat was out, I took the dinghy home for sanding and varnishing.

Here’s the damage – hand for scale.

The plywood was very wet. To see the extent of the water intrusion, I figured the plywood would have swelled where it was wet, so I sanded the whole area with a longboard. The sanding took off the bottom paint wherever the wood was swelled. I’m kind of proud of this idea.

So I cut back the glass to the edges of the swelled area and dug down a few plys to see if there was damage below that level. It was damp but undamaged – no cracks or rot.

I sanded the paint off in a larger area, then mounted a heat lamp for a couple days. I kept it pretty hot, during some very hot dry days.
WP_20140826_15_57_53_Pro WP_20140826_16_01_02_Pro

When I decided the wood was dry, I soaked the bare wood with warm neat epoxy until it wouldn’t soak up any more, then laminated small pieces of 6 ounce fiberglass cloth to fill the depressed area flush. When that was firm, I smoothed the area with QuickFair, then sanded that nice and flat.

Finally, I laid a larger layer of glass over the whole area, smoothed with peel-ply to make it smooth and flat.WP_20140828_17_10_43_Pro

A little sanding, more QuickFair, and some bottom paint, and she’s done. Back in the water in time for the Port Townsend boat show.  The boat was out of the water for five days.

My only concern with this fix is that water may have leaked past the area I cleaned and dried, and now it’s locked inside, brewing dry rot. I kind of wished I’d soaked some penetrating epoxy in the area before filling it. I guess I’ll know in a few years if I should have done that. By the way, there’s a watertight compartment behind this area. I would not have sunk even if I’d been holed through.