Episode 35 Diesel Engine Part 6 - Fixing the floor plate

One of the skills needed for epoxy work, which is hardly ever mentioned, is the skill to walk away. The temptation is to hover over the uncured epoxy resin like an expectant parent, waiting for it to do something, or, worse, to poke, prod, scrape or to try and shepherd it into the corners that might appear to have been missed.

One of the reasons for constructing the floor plate as a composite of spotted gum planks and epoxy, was to learn this noble skill. There comes a point, where you simply have to walk away, and come back again when the thing has solidified.

I reached that point last Saturday, 20th February, after pouring about 4 to 5 litres of liquid epoxy resin into the gap between the hull and the floor plate. Apart from a minor spill that resulted in a tongue-like glacier of whitish goo creeping into the bilge, it went well, so I gave the operation about 8 out of 10. The glacier was surprisingly easy to remove the next day (I ripped it out with my bare hands). I attribute the ease of its removal to it forming on a puddle in a bilge that had been regularly bathed in oil and diesel fuel for the last few years, thus denying it much of a purchase.

The glacier's lack of tenacity might have got me worried about the bond under the floor plate. However, this was an area that I had cleaned, cleaned, and cleaned again; first with boiling water and dishwashing detergent (which, I had been informed, was as good as any chemical degreaser), then rinsing and swabbing with methylated spirits and, finally, swabbing again with MEK. Also I had previously roughed the surface with a wire brush, to get rid of any loose flakes, and to provide a physical purchase for the epoxy, and followed up with a vacuum cleaner.

I taped over the top surface of the floor plate and sides with clear packing tape. The floor plate and hull were about 6 degrees from the horizontal, so that everything would flow down, forward, towards the bilge. Some of the liquid epoxy would be slightly pressurised under the floor plate, so I needed a good seal to keep it there.

I poured the epoxy into four 13mm holes drilled through the plate at its  higher end, towards the rear. Thinking about how I would get the epoxy into the holes, I hit upon the use of plastic, picnic wine-glasses, which were of just the right shape and size to act as funnels when they had had the bottoms of their hollow stems cut off. They were cheap, which always appeals. They also provided a reservoir to allow the epoxy to flow down and settle, in the way that it does. The four holes ensured that I would get the epoxy into all the places it needed to go.

Finally, I made some rough calculations on the volume needed. I thought I would need about 4 to 6 litres, and had a total of about 9 litres (mixed) to hand. This was based on multiplying the plan area of the plate, which I knew, by the thickness of the join, which I had to guess, based on eyeballing my curved jig and mentally estimating the number of millimetres between the bottom of the plate and the curved hull. Having determined that I would not run out of epoxy half way through the operation, I was set to go. I decided on a 1 to 3 to 2 mix of hardener, resin and nor cells, thinking that I would need a fairly runny mix to get it into all the available corners without leaving voids or bubbles.

When I started mixing and pouring into the picnic wine-glasses my first concern was that the liquid epoxy would reach the bottom end. It did, and I could start to see it filling up through the clear packing tape. Thankfully, to start with, there were no leaks, indicating that my aluminium angle-bracket and filler dams were working.

I worked as fast as possible, hoping to avoid the creation of voids by uneven solidification. When the liquid epoxy showed up at the top end of the floor plate, I knew I had poured enough. However, this was when I noticed the small glacier moving into the bilge. There was nothing I could do - I could not add any more packing tape, because it would not stick to anything touched by the liquid resin. I managed to get some more tape onto what I thought was the offending corner, but in the end I had to convince myself that it was a slow-moving glacier that just had to run its course until the resin had started to set. 

This was the point of walking away.

Returning the next day, I was relieved to see that the level of epoxy at the uphill end of the plate had reduce by no more than about 10mm. The resin was clearly visible in the holes previously occupied by the picnic wine-glasses, which meant that the space between the plate and hull had been filled. The upper, outer corners under the plate might not be completely filled but that would be a minor flaw.

The next steps will be to clean up, and then to start the difficult task of measuring up for the wedge-shaped engine beds. 

Floor plate coated liberally with clear epoxy resin top and bottom, before installation. I decided on a clear coat so that, if the plate were ever to rot, it would be visible. It also makes the construction material plain to see.

Exposed hull cleaned and ready for the fitting of the floor plate. I had made small dams out of filler either side of the flange plate to catch any water seeping into the area.

Last checks for clearances, using the model of the underside of the engine at, hopefully, the right angle. It looks good to go.

Picnic wind-glasses in place, jammed nicely into the holes drilled through the plate. Top and bottom lined up to the marks. This is the point of no return.

The end of the pour, showing the glacier of goo creeping into the bilge. The strings were a last-minute, ultimately successful, attempt to stop the mousing lines from sagging into the liquid resin. I am using the engine flywheel as a 17kg deadweight to weigh the floor down.