Repairing Rot, Gouges and Sprung Seams

Lookin' ugly in mid-refit.

Lookin’ ugly in mid-refit.

One of the things I love about our plywood pram is that it endlessly repairable. Not so with a hypalon inflatable. There comes a point in every inflatable’s life when the only thing left to do is pitch it in the dumpster. 10 years? Is that the average life span of an inflatable? I don’t really know.

I think we built this little pram in the winter of ’98, so it’s 17 years old, and on it’s third or fourth refit. Were I to build it now, I would certainly do things a bit differently, but as it is, it has held up extremely well, especially considering that it’s lived the bulk of it’s life outside. I have about $800 dollars in materials in it, and it’s been a tremendous value and a hard working yacht tender.

Today I fixed two corner joints that had opened up. I think this damage occurred because of how I sometimes maneuver it – pivoting on the transoms – and hauling it on board the yacht by the bow ring with a halyard. For repair, I mixed some epoxy and added filler, thickening to a soupy consistency. I drew up the soup into a large syringe and squirted it into the opening joints. I used liberal amounts of soup and refilled the syringe several times. There was lots of drippage, which I wiped up. Then I used a band clamp on the stern section to hold the joint together, and a pipe clamp on the bow transom. These two areas will also receive several layers of glass fabric inside and out.

Band clamp on the stern transom.  I had to figure out the clamp position before applying the epoxy.

Band clamp on the stern transom. I had to figure out the clamp position before applying the epoxy.

Pipe-clamped bow transom.  I love pipe clamps!

Pipe-clamped bow transom. I love pipe clamps!

I thickened the remaining epoxy soup into peanut butter, and applied it to various gouges and voids I’d opened up while chasing small areas of rot.  In fact, I had to mix up several batches of peanut butter, as I found a fairly large area (not surprisingly) underneath the repaired stern corner.

Here's the rough fill.  There is a hole through to the inside, which I backed with a small piece of plywood covered with plastic so it wouldn't stick.

Here’s the rough fill. There is a hole through to the inside, which I backed with a small piece of plywood covered with plastic so it wouldn’t stick.

Here is the same place as above (inverted - dinghy is now upside-down).  I pared down the excess with a rasp, then smoothed with an orbital sander.  The darker bit at the bottom is fresh filler - 2nd round of repair.

Here is the same place as above (inverted – dinghy is now upside-down). I pared down the excess with a rasp, then smoothed with an orbital sander. The darker bit at the bottom is fresh filler – 2nd round of repair.

Wood rasp is another favorite tool.  For rough-shaping epoxy repairs, it can't be beat.  It is the fastest, most accurate way to get the basic shape.  It requires a light touch because it's so coarse and removes material so quickly.

Wood rasp is another favorite tool. For rough-shaping epoxy repairs, it can’t be beat. It is the fastest, most accurate way to get the basic shape. It requires a light touch because it’s so coarse and removes material so quickly.

Finally, I bleached the thwarts with oxalic acid, but it only seemed to lighten the dark lines. I could use a stronger solution, but I think I’ll just live with it. I don’t like using the chemicals, and it’s a several-step process anyway: you apply the solution on the wood several times; allow to dry, then rinse thoroughly with baking soda solution to neutralize the acid; clear water rinses follow, then allow to dry; re-sanding is needed because the water raises the grain.

Here's the midship thwart. It will look okay under varnish.  Not perfect, but serviceable.

Here’s the midship thwart. It will look okay under varnish. Not perfect, but serviceable and protected from the weather.

Tomorrow is supposed to be rainy, so I may need to wait a day or two for clear weather to continue.

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6 comments
  1. I only just discovered the epoxy and syringe method. I used it on my last repair. I prefer hard dinghies as well, but with limited space and a family of four I needed the capacity of an inflatable. The dinghy will look great with a little TLC.

    • Adam, I find the syringe to be invaluable especially for potting fastener holes in the deck. Tape the bottom side of the hole, fill it with resin, then draw the resin out again (now the inside of the hole is coated with resin), then fill it again with thickened epoxy. Drill through the cured epoxy for the fastener. It doesn’t compress and the core is completely sealed. Any place you can’t brush resin, the syringe is likely to work well.

      The hard dink has pluses and minuses, which I’ve outlined here:

      https://middlebaysailing.wordpress.com/2012/05/10/simple-conveniences-simple-systems/

      Which works for you all depends on your circumstances, preferences, and application.

      The dink (aka “Sea Minor”) always cleans up really well, then looks pretty good for a long time.

  2. Duh, I hadn’t thought about using a wood rasp to knock the big stuff down. Thanks for that tip. I’ve been grinding away with sand paper. It just amazes me how stiff and tough fiberglass covered plywood is. Really like your pram.

    • Greg, the most effective way to use the rasp is to catch the resin when it’s still “green” – that is, still a bit soft, but not soft enough to dent it with your finger nail. After that, it becomes hard as a rock, as you know, and the *most* effective way to shape it then is with a grinder. But a grinder removes material at nearly an uncontrollable rate. I’ve also used my random orbital sander to shape cured glass and resin. 36-60 grit disc. Slower than a grinder, and that’s a more manageable pace. I always wear a respirator anytime I grind this stuff with a machine.

  3. the stories your dinghy could tell. There is just nothing like a well worn and trusted friend to get you from dock to boat time and time again.

    • So true! Actually, I’m glad it’s mute. Saves me embarrassment over the times I’ve fallen into the water moving from dinghy to pier/yacht or vice versa. Or the looks on my wife’s face as water splashed over the bow transom where she was sitting – priceless expression!

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