Episode 37 Diesel Engine Part 8 - Glue Fail

My epoxy glue failed. 

I had cut my new beds in four pieces from 48mm Merbau timber, and glued them in pairs to form two beds, both 96mm wide, using Norglass Epoxy resin. I noticed that something was wrong a few hours after gluing because the excess epoxy resin still felt liquid-soft. After a week, it had lost its tackiness, but was still soft enough for me to indent it with a fingernail. Worse, I could scrape off the excess epoxy resin with a paint scraper, and roll the excess into a ball with my fingers. Finally, I cut of the end and found that the joint was not difficult to break, leaving the timber in tact. Whatever the breaking strain of the glue in the joint, the epoxy was weaker than the timber, which was unacceptable.

I tested a sample of the remaining resin and hardener, and found that it would not set. My best guess is that during the pour for the floor plate, I exposed the bottles of the resin and hardener to the sun, which had done something bad to the chemistry. Thankfully, the resin for the floor plate in the boat had set as solid as a rock, and it had consumed nearly all of the 6 litre pack that I had bought. I was using what was left, thinking that it was OK.

This was an inconvenient set-back, but not as inconvenient as, say, the beds disintegrating at sea. Rather than risk my newly constructed beds, or try to fix them up with bolts or screws, I decided to throw them out. I had lost about $120 for the timber, about a day’s work and a week of elapsed time.

The new, new beds would be constructed from a single piece of timber, but the only convenient source of suitably sized and priced timber was the Demolition Yard, nearby. I selected a 120mm x 120mm square post, 1.5m long, paid $30, and got to work. I don’t exactly know what timber it was, only that it had been classified as “hardwood”. I do know, however, that it had already had a lifetime of seasoning, unlike much of the new timber in the yards.

The first job was to scrape off the old paint by hand. Although this was physically demanding and slow, I could check all the surfaces for any remaining nails or screws (I found the remains of one nail). I could also get a feel for where the splits, knots and soft timber lay. 

My templates and failed Merbau beds were put to use to find the best orientation for the new beds, and the setting-out of the long cuts. My circular saw cuts to a depth of 63mm, so the long cuts were made by cutting in from both sides to the half-way mark. About half the cuts met in the middle, and half did not. I used my reciprocating saw to clean out the connected cuts, and to connect the unconnected cuts. Although the reciprocating saw can cut through thick timber (the thickness depends on the length of the removable saw-blade) it has almost no directional control, which is why I needed the circular saw-cuts as a guide. In hindsight, it would have been better to take the timber to someone with a band-saw. 

For the short cuts, I used my newly acquired Bahco tenon saw, which, at about $50, was the most expensive on the rack at the hardware store. My previous tenon saw was cheaper, but had a tendency to wander off line and bind.

The next step was to clean up the timber with a plane. I had previously bought a hand plane at a closing-down sale, but knew little about how to sharpen the blade or set it up. The YouTube channel Third Coast Craftsman was an education, which was followed by a lengthy on-line search to find a real bricks-and-mortar shop nearby that would sell me a sharpening jig. It took considerable effort to persuade Google that I was not in search of an expensive power plane, and eventually found the desired item in the Carbatec shop in Wakerley. I went in with the intent of buying a $20 sharpening jig, and came out with the sharpening jig, sharpening stones and a strop, all for about $130.

The sharpening gear made a huge difference to my hand-planing. I could not quite get to the consistent waxy-smooth finish, or the uninterrupted whooshing sound of a perfectly formed shaving being parted from the parent timber that is featured on so many on-line videos. I did, at least, get away from the juddering, ripping and gouging of my previous attempts, much to the relief of my wife, who had hitherto tolerated my house-shaking planing with remarkable fortitude. 

The steps in the timber beds complicated the working of the lower steps, and accounted for some of the skin on my knuckles. However, the “free” surfaces on the bottom, sides and top, came up nicely. I know that these are only engine beds, destined to lie hidden under the diesel engine, but I found immense satisfaction seeing the beautiful patterns of the grain emerge in a way that cannot be done through sanding.

My saw-cuts and consequent trimming were not as accurate as I would have liked. There are still small differences in angle and depth, but they amount to less than 3mm from one bed to another, or from one end to another, which is probably OK. The only remedies I can think of are to clamp the two beds together and work over them with an accurate bandsaw, or a table saw, or a router in a frame, none of which are available to me.

Further rough dry-fitting confirms that the beds are good to go, and I am back at the stage where I need to drill the holes for the coach-bolts to bolt the new beds to the floor plate. For this I will need a pillar drill, or drill press, which means further calls on my mates.

Failed epoxy resin glue joint - the glue should be stronger than the timber

Scraping old paint off the 120mm x 120mm recycled timber post

The hazards of recycled timber. In this case, the pointy end of a mild steel nail

New beds, rough cut. Clearly visible are the joins where the cuts from both sides had not met in the middle.

New beds after much planing. The mitre in the port side bed (the far side) is a cut-out for the water pump on the Diesel engine. The thick and thin ends of the wedges still need to be trimmed.

Preliminary dry fitting of port (larboard) bed. The thin piece of timber in the middle of the floor plate, stuck into one of the holes in the shaft flange, is a strut intended to keep some pressure on the drive shaft so that the seal does not leak as it did previously.

Preliminary dry-fitting of starboard bed