Bilge Cover Repair

So, the large hole in the center of the Belle’s cabin floor has a fiberglass cover. It was originally a balsa wood core panel, typical of the boat’s topsides and cutting edge at the time. At some point, probably to make it easier to remove, someone drilled a hole or two in it. This is the Achilles Heel of balsa core construction. Once the waterproof enclosure is compromised, i.e. the fiberglass cut or cracked and not sealed back up, the delicate balsa wood rapidly deteriorates and the panel loses most of its structure. (These folks like to use the term “compost“). The backside of the bilge cover had already split open when we got it and someone drilled another hole through from top to bottom and put a machine screw with nut through the panel to hold it together. It was altogether unsatisfactory and safer to leave the bilge open than use this panel as-is. So, a bilge cover repair was necessary.


Scraping out old balsa from bilge cover
Scraping out old balsa remains

Step one was to remove what was left of the old balsa core. Most of what was still in there simply fell out. The rest was easily scraped off with a chisel. Now that the core was empty, I needed something to add rigidity back into the panel. Ordering and cutting the end-grain balsa just like was original would have cost:

  • A. Money
  • B. Time
Gluing in dowels into the bilge cover
Gluing dowels in place

Without much of either available, I took some wooden dowels I had and cut them to the width of the bilge cover cavity with some wiggle room and glued them in place with hot-glue temporarily. The bigle cover was not flat, the stresses in the fiberglass now relieved because it is no longer bonded to anything. I needed to hold the bilge cover flat while I hot-glued the dowels in place (so they would not move while laying the fiberglass over them). To do this, I used a piece of aluminum angle stock and a stick of 3/4″ PVC pipe I had in the garage. I made a “bow” with the PVC pipe by bending it in the middle and putting one end on the ceiling and the other on the aluminum. With two more sections of aluminum angle underneath the bilge cover, I was able to get the bilge cover quite flat and stable.

Cutting Glass Cloth for the bilge cover
Cutting Glass Cloth

I then cut fiberglass cloth to size so as to make 3 layers over most of the panel. Assuming that the folds in the cloth would make little pseudo-triangles across the panel as the rose and fell over the dowels and create significant rigidity for low weight.

Bilge Cover Assembly

applying epoxy resin to the bilge cover
Applying epoxy resin
Applying spray foam
Applying spray foam
Replacing back on the bilge cover
Replacing back cover and gluing in place

With the glass cut, I mixed up some epoxy resin in small batches so as not to get a flash in the cup and waste the expensive resin. Getting the glass cloth to lay down nicely proved far more difficult with all the “sharp” bends than I had anticipated. It took far too much time and effort. I should have ordered balsa wood online. I’ve since seen a sheet of 3/8″ 2’X4′ end-grain would have cost me about $20.

I ran glass down both sides of the bilge cover, to each side of the aluminum brace. Once this first layer had set, I removed the PVC pipe and the aluminum. I was then able to lay two full-width sheets of glass cloth over the whole bilge cover and leave to set.

Letting foam cure
Letting foam cure

After the epoxy had set, I trimmed the edges and high spots with a flap disk on my angle grinder until the original bottom fit well on the bigle cover panel. I then used a can of spray foam to fill the voids and glue the bottom back on thinking it would be much like the original balsa core. I used “gap and crack” foam as that is what I had in the garage. It worked well enough, but “Door and Window” foam would have been a far better choice as the high expansion rate foam lifted even the big pile of steel and wood I left on top.

Final Product

Bilge Cover Repair
A bit grubby looking still, but it works.

The results are adequate. It certainly doesn’t look “like new”. The screw holes are still visible. But then again, it isn’t new at all, is it? It needs a good scrubbing, as does the rest of the boat. Despite being slightly thicker than the original (foam lift), the repaired panel still sits slightly lower than the surrounding floor. It seems sturdy enough and we walk on it without it creaking or cracking. And, even if the dowels rot away, the primary structure is from all the folds in the fiberglass I laid down.

All-in-all a successful bilge cover repair job.

On to the next project!

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