The Floor – Construction

We lifted all the ballast blocks, cleaned up all the sawdust and sprayfoam dust (which would have held any water or damp down there, stopping it from evaporating off easily), then used a wire brush to clean up patches of rogue sprayfoam and rust. The base of the boat had been sprayed with a layer of bitumen, as is standard in the boatbuilding industry. We needed to top it up in places but we didn’t want to apply more fossil fuel, which is what led us to this amazing product: Lanoguard

Lanoguard is made from lanolin; the grease from sheep’s wool. It applies easily, you don’t need any protective equipment, you can apply it to surfaces that have already been treated with bitumen or paint and it dries to form a protective coating on the steel. There’s been a lot in the news lately about British farmers struggling to stay afloat, so I also like that we are supporting them too. Two of these bottles covered the entire internal bilge of our 65x10ft.

It was good get right down to the baseplate as we found one of the steel ribs (transverse bearers – thanks for the proper term JC) had only been tack-welded in place by the steel fabricator, Aquarius Boats, and had broken free on one side, presumably when the boatbuilder rammed too many ballast blocks between the bearers. This also isn’t helped by the fact our base plate is convex; the floor is higher in the centre. Anyway, our friendly welder to came and welded it down properly.

The ballast blocks were put back in place and it felt good to finally be building rather than demolishing!

To support the floor, I had designed a grid of 25x50mm recycled plastic lumber, which would criss-cross the transverse bearers to form a strong, level base for the floor. We went with recycled plastic lumber because it will be in the bilge and needs to last the lifetime of the boat.

Initial sketch of the floor grid.

The larger blocks are 96mm high, the smaller blocks are 100mm high and the transverse bearers are 75mm, every 2ft all the way down the boat. I placed a batten on each transverse bearer, bringing the base height of the grid to 100mm. 7 equally spaced longitudinal battens were then fixed to the transverse battens, supported in between by the smaller blocks. I used stainless steel Spax screws so they won’t rust or rot. Once screwed together, the grid was held securely by the shape of the boat, with leeway for expansion/contraction.

Bow end floor grid

This plastic lumber was like working with chocolate! It is really flexible; almost elastic, and you need to be careful cutting and drilling it as it melts easily. It needs more support than the equivalent sized wooden batten but will not snap, so curving them around the shape of the hull at the edges is really effective, providing support to the floor right to the edge.

Since the floor as being constructed in sections, starting from the bow, I didn’t realise that the small ballast blocks were only added to the bow third of the boat in order to counterbalance the batteries. Past this it was only the larger blocks so I needed to add 4mm shims (cut from the plastic lumber) to support the battens half way between each transverse beam. At the stern end of the boat the ballast had been removed completely, so I created a floating floor structure with more rigid 50x50mm lengths of lumber used transversely, supported by 50x50mm pillars cut from the same stuff.

Floating floor support grid construction

At this point the floor was a bit of a ninja warrior course as the Lanoguard beneath was still wet while the grid was under construction and not screwed down on the precarious little pillars… needless to say there were occasions when I slipped off the grid and put my foot in the grease! Thanks to the nature of the grease, the blackness came off in the wash, and my feet were super-soft afterwards!

Black, filthy Lanoguard foot!

Next was the insulation. The salvaged sheets of 25mm PIR insulation board were cut to fit within the grid, then aluminium taped to stop any draught.

Next was to put the floor down – these were sheets of stormboard; recycled mixed plastic core with a recycled plastic coating top and bottom. One thing I didn’t realise when working with plastic was all the microplastics you create when working with it; every time you cut it you create plastic dust which you can’t recycle (the tip wouldn’t take my bag of the stuff) so it has to go straight to landfill. I was also careful to cut everything inside the boat and vacuum up all the mess so there was no chance of it getting in the river and becoming part of the ocean plastic soup.

Again, interesting stuff to work with, and surprisingly responsive to temperature changes – it contracts and expands considerably. We put the boards in during the summer, and by November the gaps between them had opened up a good 3-5mm. I decided to apply sealant to stop any water spills getting into the bilge, and to help with the insulation, and also stop muck and dirt getting down there. However, that’s a considerable expansion difference for a sealant to cope with – the first sealant applied during the summer (Sikaflex EBT+) has made a valiant effort but has pulled away in many cases. I’ll reapply while it’s cold and the gaps are at their widest, and see how it holds up.

And finally… inspection hatches – I can’t stress how important these are in a boat, and even in an unfinished state, these have saved me a few times with checking where water has got to. I’ve cut an inspection hatch at the bow end because we have a stainless steel water tank in an alcove there and if it leaks I want to know about it. We’ve got an inspection hatch in the bathroom, mainly to access the bath waste and it will also catch any leaks from the rainwater tanks. There’s a panel in the passageway that we can lift if we need to, and I’ve made sure two large boards in the lounge area can be lifted, in case we need to adjust the ballast later in the build. The most important inspection hatch of all is the one at the stern end, beneath the steps. This is where water will go eventually if we have a major leak, and it’s also how I realised that the stern door was leaking.

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