The Naiad Voyages

Mark Austen

2017.09.29 - Bottom Boards Revisited

I had hoped to go sailing today, when I put the mainsail back on yesterday afternoon, the wind was light and the weather very nice indeed. The forecast for the morning was force 2 gusting 3-4 with light rain until 9am (ish). Well, the forecast was wrong. Sort of, you see they changed it late last night to windy and wet most of the day and that is what we have.

Disappointing, however the forecast for tomorrow morning is force 2 gusting 3 becoming 3 gusting 4 so I may yet get a sail early tomorrow. We shall see.

In the meantime, I have some repair work to do and it is all the fault of that nice new canvas cockpit cover I made a couple of months ago. The problem is that it doesn't completely work. It keeps most of the rain out but not all and there has been some water in the bilge. I didn't notice this until I got into the boat two weeks ago and when I stood on the port side bottom board there was a loud crack as it split.

I had put 5 coats of varnish on the upper surfaces of all the boards but because the undersides were not going to be seen I only put one coat on each bottom board. That is not enough to seal it and the water in the bilge has made the bottom boards warp to the point that standing on them breaks them. Two of them are so warped that I cannot get them out. I have sponged out the water and I hope that this will allow them to dry out a bit so that I can get them out otherwise I'll have to break them in two and then glue then back together again.

In the meantime, I brought the other boards home yesterday after bending on the sail and put them over the Rayburn with the expanded, non-varnished side down and this morning they had returned to their intended flattened state.

Currently four are having another four coats of varnish applied to the bottom surface and one is being repaired first.


This is the one being repaired. The wood is Oak so I have to use resorcinol glue rather than epoxy. The cramps keep the crack closed whilst the glue cures and the metal box is just a weight on the wood beside the crack to stop the crack opening upwards under the pressure of the cramps.


The other four have the first of four coats of varnish applied.

Now, whilst this will probably stop the boards from warping in the future, I still have the problem of the not totally waterproof cockpit cover. Reading up on making canvas waterproof gives three possible solutions. The first is to throw the existing cover away and make a new one from a heavier gauge canvas such as is used for our medieval tents. This is certainly waterproof as we can attest, however, this is quite an expensive solution.

The second method is to wash the canvas to ensure that it is clean and free from grease and then to use a wash-in waterproofing compound such as Nikwax Cotton Proof. You wash the canvas again only using the compound instead of detergent and this coats the canvas fibres with a water resistant film. The third method is to wash the canvas as before to get it clean and then apply a mixture of equal parts of beeswax and paraffin wax with a brush. You have to heat up the waxes as they are solid at room temperature. Once the canvas has been sufficiently covered, using a hair dryer or heat gun on low you heat up the wax that has been applied to the canvas so that the canvas fibres absorb the wax and become waterproof. Essentially you now have a waxed cotton cloth much the same as the waxed cotton jackets that you can buy for a lot of money.

The problem, with the last method is that not only does this make the canvas heavier and sticky but treating a large piece of canvas will take some time. It will, however, make the canvas totally waterproof. It would probably need to be re-waxed every season where rubbing the boat has worn through the wax.

So I'm going to try the second method first and see how that goes. I'm not entirely sure that this is going to work since the canvas is light and even though the fibres will become quite water resistant, there may be enough gap between the fibres to allow the water through. It is, after all, advertised as a breathable waterproofing system.

Come to think of it, I should really try both methods on some of the canvas I have left over from making the cover as a test. There is also the question that having treated the canvas with the Nikwax Cotton Proof, will I then be able to wax it afterwards should the Nikwax method prove to be insufficient.

I have the day off, some beeswax and some white candles for the paraffin wax, I think I'll have a go at the waxed cotton method as see how easy or not it really is.

Watch this space...