The Naiad Voyages

Mark Austen

2015.10.03 - Bad news

Not good news today.

I decided to cut out part of the starboard thwart to see what the damage to the hull really was. I’ve given up on the softly, softly technique and much as it pains me to be taking a power saw to a boat in such a fashion, I hacked out the thwart from midships to the afterdeck and revealed a huge amount of rotten wood. The inner veneer has gone in most places and most of the second veneer in others.

The bad news is that I suspect that this rot has extended most, if not all, of the way to the front part of the hull covered by the thwart. There are no drain holes in the thwarts to let out any water so any that was trapped in there 20 years ago, stayed in there. Also any wood eating products produced by the slow decay of the foam over that period were similarly trapped.

So, my repair job just became a whole lot harder. Well not harder, really, but there’s a lot more of it.

To repair all this I will need to scrub out the rotting section with a wire brush and then use a vacuum cleaner to get out the dust. The inner veneer will then be trimmed so that it is a regular shape with straight edges. A new veneer will then be put in place in small sections, probably no more that 4” or 10cm wide with a lot of epoxy glue thickened with microfibres to fill the gap between the remaining veneers and the new inner. I shall try to match the grain direction of the veneer. Once set this will restore the rigidity and strength to the hull. Once the entire damaged hull has been treated in this way, on both sides of the boat assuming the the port side is similarly afflicted, I will drill small holes right through the hull to mark the extent of the new inner veneer and then turn the boat over.

This will also require me to construct something fairly solid to rest the boat on that will firstly raise the boat up to working height and secondly allow me to crawl under her should I need to do something on the inside.

Then the really heart-in-the-mouth bit. I will remove the outer two of the three veneers using a router and a jig to constrain the router to the section of the hull I want removed. Again this will be done in strips, probably no wider than the original veneer and certainly no wider than the base of my router! This will also remove most, if not all of the thickened epoxy put on when glueing in the innermost veneer but since that was only there to be able to get to this point, it doesn’t matter. What does matter is that all of the damaged wood is removed.

So, having removed the two outer veneers and to a point about 1/2” or 1.3 cm beyond the edges of the new inner veneer, I will then glue in place a new middle veneer using thickened epoxy and using staples to hold the veneer down while the epoxy is setting. Again, this will be done in the same direction as the rest of the middle veneer. The staples will be moved before the outer veneer is glued in place.

The router will then be used to remove the outer veneer around the repair for another 1/2” or so and the outer veneer then replaced with a new veneer glued as before. Finally I will have to sand the whole thing so that the repair is flush with the original hull.

Then repeat for the other side if that is damaged.

Tedious?

You bet!

But not difficult.

I don’t think I will be getting her back in the water by next year.

The epoxy is on order and I have made up a cutting list of wood that I need and will be making a trip over to Robbins Timber in Bristol next Friday. Right now all I need in the Agba veneers but there’s no point in going all that way without getting as much as I can. It’s a ten hour round trip and I don’t want to do that more than once if I can help it. So I’ll be getting the wood for the decks, cabin, spars and wot-not even though I’ll not need them until later.

Thinking about it, it does give me something else to do when I get tired of routing, glueing, stapling and sanding the new veneers. The spars will not be difficult to make and it will feel like real progress to get the mast made or the bowsprit.

I’m quite looking forward to all this. Just as well really!

The damage to the wood is not rot as I have encountered it before. It is almost as though the lignin holding the wood fibres together has dissolved.

The rot revealed. The wood has turned to a dry, almost powdery consistency.

You can see just how extensive the damage is here, all of the inner veneer has gone and a lot of the middle one as well.

A closer look at the worst part of the damage in this section where all three of the veneers have been damaged.

Wikipedia has this to say about lignin amongst other things:

“Lignin was first mentioned in 1813 by the Swiss botanist A. P. de Candolle, who described it as a fibrous, tasteless material, insoluble in water and alcohol but soluble in weak alkaline solutions, and which can be precipitated from solution using acid.”

I wonder if the foam is alkaline or has an alkaline by-product or degrades over time producing an alkaline compound.