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.

Episode 34 Diesel Engine Part 5 - Construction of the Floor Plate

The construction of the floor plate has to be the most geometrically challenging project I have ever undertaken. It has consumed countless hours over the past two months, and I have been working on it more than the engine. If I were doing this at work, I might use 3D laser-scanning to create digital twins that I could play with, tossing them around weightlessly, cutting holes and filling gaps with ease on the computer screen. But, I am doing this at home, which means using the analogue prototypes of hull and engine, and slowly figuring out how to join the one to the other.

The floor plate’s first function is to provide a strong platform, glued securely to the hull with epoxy resin, onto which I can bolt the engine beds. The hull is curved, and the engine beds will be made of wedges, cut to the right angle between the axis of the engine and the hull. The second function of the floor plate is less obvious, but just as important, which is to provide the reference surfaces and planes from which I can take the measurements for the engine beds.

The construction of the floor plate used 20 pieces of spotted gum 19mm floor planking, assembled in four layers, joined with birch dowels and epoxy. I also made up several jigs to measure things and to act as guides to the cutting operations.

I chose spotted gum because it of its density, strength and durability, or resistance to rot, according to the New South Wales Technical Publication Series 5 Timbers in Boat Building. Another reason is that it is available as machined flooring planks. Given that I would be assembling the floor plate in my own garage, I thought it would be better to start with something sawn to machine-grade tolerances. The floor planks also meant I could build up the layers with the grain criss-crossed, like plywood, increasing the strength of the composite construction in all planes.

I used Norglass Epoxy with Norcells as a filler or extender. The slow hardener gave me more time to get things positioned, and allowed the epoxy to run into all the cracks and voids it could find, reducing the opportunities for water to get into the timber. I had also tested International Epiglass, but it cured faster and gave off considerable heat, which might have stressed the composite construction. Before gluing I wiped down the surfaces with Methylated Spirits and then MEK paint thinner. Fun fact; MEK dissolves some types of plastic gloves.

Another aspect of this approach was that it built up my experience of working with epoxy resin before the Big One, which would be pouring the epoxy into the join between the floor plate and hull; a daunting point of no return and something that had to go right the first time.

Typically, I mixed the hardener, epoxy and Norcells in the ratio 1:3:4 by volume. This yielded a white paste with the consistency of runny custard. Liquid epoxy has no surface tension, unlike water, and if it finds the tiniest crack, it will find a way through. It does not run fast, but it does run far. I found a friend in clear packing tape, which would stick to the timber, but deny any adhesion to the cured epoxy. I became adept at constructing packing-tape dams around my assemblies to stop the liquid epoxy dribbling down the sides. 

My experience with the runny-ness of liquid epoxy portended a potential problem with the gluing of the floor plate to the hull. If the hull were horizontal, life would be easy, but it is not. It is at an angle of about 6 degrees to the horizontal, meaning that any epoxy I pour into the join would simply run out of the downhill side, forming an immovable puddle of useless gunk in the bilge, forever fixing whatever it touched permanently in place, except, of course, the floor plate. I built a dam around the outside of the floor plate with extruded aluminium angle, sealing the remaining gaps with Parfix gap filler. The addition of packing tape should keep the liquid epoxy in place until it has set. I will report back on this operation, when it is done.

The assembly of the spotted gum planks took several weeks, including an afternoon with my mate, Naman, and his tools to get the sides trimmed and squared up. He is a furniture-builder, and went to town on getting the angles right. It was interesting watching him work. Like other craftsmen, he would take perhaps 15 to 30 minutes setting up a cut, the cut itself being quite brief. No wonder Leo has spent the last four years restoring and rebuilding the classic sailing yacht Tally Ho (I watch his YouTube episodes religiously).  The last thing I asked Naman to do was to route a scoreline along the centre for reference. I told him not to fuss too much about the bottom surface, because it was about to get hacked. When I got the plate home, I shaped the curved base with the wanton use of a belt sander, checking it with a jig to mimic the curved hull.

Having got the base of the floor plate to mate with the hull, I measured the dimensions for the top surface. This is where I needed my measuring-jigs. There are no published dimensions for the engine or its mounts, so it was a case of measuring what was there and transferring the dimensions to the floor plate and my measuring jigs and guides. 

However, one cannot simply measure the dimensions between the bearings on one side to the other. The engine is in the way. Also, it is impossible to measure the height of the engine sump from the floor, because the underside of the engine has an irregular shape, and the whole thing is at an angle. My most recent jigs include a positive template of the underside of the engine cut into a piece of pine (the negative came from a breakfast cereal box), and sawing guides, cut at the right angle (hopefully) to the floor plate. With these two jigs with the shaft flange as a reference, I estimated the clearances under the engine, and hence the angle and dimensions of the slot cut into the top of the floor plate. 

I might have overthought it a little, but in anticipation of this slot, I glued the lower layers of the spotted gum sideways, to reduce the exposure of end-grain to a potential source of water from the shaft seal. These sideways-on pieces provided extra strength to the longways-on pieces, as I cut through the upper layers. The last dry-fitting on the boat showed me that I had got the angle wrong, and I needed to cut the slot deeper to ensure sufficient clearance to the underside of the engine, allowing for its biggest vibrations. I don’t know exactly what clearance is sufficient, but I reckon that if I can get the tips of my fingers into the gap (about 10mm), it should be enough, even allowing for the inaccuracies in my measurements. Deepening the slot with my circular saw left a couple of accidental gouge marks that might need to be filled. The filling is mainly cosmetic, but I worry about the opportunities that the water might take to get into the grain of the timber.

The photos show the completed floor plate. The handles are temporary, allowing me to lift the 16.5kg thing and jiggle it into place on my work bench and in the bowels of my boat. What remains are some final checks, some coats of epoxy or varnish to seal the surface, and a thorough clean of the hull. Finally there is the scary job of gluing it in place with only one chance to get it right. Once it is in there, it is never coming out.

 

Underside of floor plate. The jig at the back mimics the curvature of the hull.

Topside of floor plate following its squaring up by Naman.

Perimeter dam around hole in floor, made from aluminium angle, to stop the liquid epoxy running  away.

Negative of underside of engine, made from a breakfast cereal box.

Transferring the negative onto a positive template of the underside of the engine.

Saw guides, used to cut the slot into the top of the floor plate.

Chiselling out the slot. The chisel set originally belonged to my great-grandfather, who was a merchant mariner, probably used for his apprenticeship.

Dry-fitting the floor plate with the engine template.  This shows that there is insufficient clearance, meaning that the slot needs to be made bigger.

Using new cutting guides and the engine template to test the larger slot for  clearances. This time, it looks OK.

The finished floor plate, looking at the rear. When the floor plate is in the boat, we would be looking forward. The slot accommodates the gearbox and flange, so that the flange can be fitted to the prop shaft. The handles are temporary, but are jolly useful in moving this thing around.

Episode 33 Diesel Engine Part 4 - Paint, Acid, Limescale, Thermostats and Anodes

The good thing about paint is that it covers everything in a nice glossy coat. The bad thing about paint is exactly the same - it covers everything, including the parts you might want to see. This seems to me to be something of a disadvantage when, for example, you are trying to figure out what lies beneath. In this case, I needed to take the thermostat assembly apart to fit the new thermostat that had finally arrived from The Engine Room. 

It took longer than the 2 to 6 working days, that I had paid for, to ship the new parts from the Auckland to Brisbane. The Engine Room had placed the order on 30 Dec 2021 and the parts arrived on 19 Jan 2022, which, by my reckoning, is  at least 12 business days, depending on how you count public holidays. Yes, I know it was Christmas, and COVID etc. but of all people who should know how these things affect their business, it is the couriers, and they should advise accordingly. I don’t blame the Engine Room, but I am miffed about not getting what I paid for, in terms of delivery time.

When I took delivery of the rebuilt engine from Diesel Works, it had come in its shiny new coat of paint, but with the thermostat removed. You can see the old and new thermostat and engine elbow in the photo below. It is obvious that the old thermostat was cactus, and had been so for a while.

I needed to take the newly re-assembled housing apart, so I could insert the new thermostat. This is where I got to the problem of paint. Bukh, along with other engine manufacturers, uses many different metals in the construction of its engines. Some parts are softer than others, which makes them more vulnerable to spanner-wielding amateurs, like me, than other parts. The problem with paint is you don’t know which part is made of what until you take it apart. Also, when a part of one type of metal is screwed into a part of a different type of metal, you get the corrosion caused by dissimilar metals, which is especially problematic in a marine environment. I found a good example of this when attempting to remove the old brass barb from the old stainless steel exhaust elbow. There was so much corrosion product in the joint, that I practically destroyed the old barb trying to unscrew it, hence, the hasty addition of a new barb to my shopping list from the Engine Room (the old and new barbs are included in the photo below).

With softer metals, such as brass, you can easily round off the nuts or strip the threads when taking components apart. Some of the parts for the thermostat housing took some persuasion to shift, hindered by the awkward arrangement (what my mate rightly calls “awkwardosity”) of the corrosion-welded components. I resorted to ingenious and unrepeatable combinations of the bench vice and adjustable spanners to grip the part and a large shifter to turn the housing.

Further problems arose from the accumulation of lime-scale inside the assembly, which contributed to the melding of parts that should not have been melded. The Bukh DV10 LME, like the others in its family, is cooled by seawater. It sucks water from the ocean, pumps it around the cylinder block, and pushes it into the exhaust elbow from which it gets blown back into the sea via the muffler and exhaust pipes. The rate of circulation around the cylinder block is controlled by the thermostat. When you heat or boil seawater you are left with a number of residues, including limescale, which is the same stuff that goes into making cement. Limescale, being alkaline, can be removed by an acid.

Being rather fussy about cleaning things before putting them back together, and also needing a clean seat for the new thermostat, I decided to clean the parts in an acid bath. Initially, I was concerned that the acid would eat not just the limescale, but also the parts themselves. After some tentative trials and research, I settled on a concrete cleaner from the local hardware store, because it was mainly Hydrochloric Acid, was relatively cheap and came in a 5 litre bottle. I reckoned on quantity rather than quality, as I did not know how my parts would react. I found that the acid ate the limescale, leaving the metal and paint in tact, so I put the parts in for a soak over a couple of nights to shift the limescale cement and other gunk. The acid might have eaten some of the parent metal, but it was difficult to tell. I thought the loss of any parent metal a fair price for a clean seat for the thermostat, and a general clean out of the tubes.

The acid bath and cleaning revealed that the connectors were brass, the thermostat housing body was copper, and the top piece, which connected them together seemed to be a composite construction with a copper skin and an alloy body. I say “seemed” because it is not clear whether the surface I was cleaning was residual limescale cement, or parent metal. Or something else.

In the disassembly process, the paint to the connections took a bashing. Rather than repaint them, I decided to clean off the paint completely. I like the look of the brass. I know it will not stay this clean and shiny but, in future, it should be obvious that it is a brass fitting, deserving of more care than, say, cast iron.

I reassembled the thermostat housing with new gaskets and replaced the old, crimped water lines. A new set of gaskets from Bukh costs and eye-watering $700, which is way too much to consider every time you need to take off the thermostat housing, or something else. I would only consider a new gasket set if I were to disassemble the cylinder head, which is unlikely. I bought some gasket paper and Permatex Ultra Blue (gasket goo) from the local Auto Shop, and cut out some new gaskets for the thermostat housing with a sharp knife and nail scissors. The fellow in the shop assured me that the paper and goo was good for water, as well as oil.

I also found that the metal used to crimp the water and fuel lines was quite soft, possibly lead or alloy. I needed to remove the crimping and the old lines from the banjo bolts so I could re-use the latter. The crimping yielded to some attention from a wire cutter, leaving the banjo bolts mostly unmarked.

The ambiguous interface between parent metal and limescale resurfaced when I poked around with the engine anode. The anode is, or should be, a removable bolt with a sacrificial zinc body screwed into the end. Provided the zinc is electrically connected to the engine, the seawater cooling water will eat the zinc in preference to the engine. Because of its sacrificial nature, the anode needs to be replaced regularly. Unfortunately, a previous owner appears to have foregone the replacement of the zinc anode, electing instead to screw in a plain mild steel bolt with no visible zinc. The mild steel bolt is 14mm diameter with a 22mm nut on the end and it had been shorted by the addition of a nut as a washer on the outer surface. It also has a copper washer. 

When I removed it, I could see how far the bolt protruded into the coolant gallery around the cylinder head, but was unsure whether the far end of the hole was parent metal or an accumulation of limescale cement. The replacement pencil anode that I had bought was a cylinder with a diameter of 12mm and a length of 37mm, specifically marketed for Bukh engines, but I could only insert it 25mm into the hole, which was the length of the old steel bolt. The question remained about whether I had reached the end of the “real” hole, or if the end had been blocked up with limescale cement. There was no way of telling, without drilling it out. However, if I drilled it, I risked drilling all the way through the wall of the cylinder block, which would kill the engine with certain death and write off the money I had spent on it. 

With the help of a mate, Bill and his pillar drill, I cut off the end of the old bolt, drilled and threaded a hole into the end, screwed the new pencil anode onto the bolt and sawed off the excess length. It was galling to reduce the zinc cylinder from about 37mm to 12mm to get the assembly to fit into the hole. At least I had an engine anode, where none existed previously. Further, I now the means to replace it frequent intervals.

I am now seeking some advice, from anyone who knows, about how deep the anode hole should actually go. My cut-down anode will work, but may need replacing at frequent intervals. It would be nice to be able to insert a full length anode, and leave it longer.

(CORRECTION - I had previously referred to this engine as a Bukh DV10 LSME, but it is, in fact, a Bukh DV10 LME. The "S" is the sail drive version, which this is not).

Old and new replacement thermostat, exhaust barb, exhaust elbow and exhaust gasket.

Old and new replacement thermostat, exhaust barb, exhaust elbow and exhaust gasket. The jagged hole in the old exhaust elbow occurred from previous attempts to fix it.

Example of old water line with crimping. The banjo bolt housing, to the right, needs to be saved for re-use.

Thermostat housing at start of disassembly, showing the gaskets. I'm holding the housing upside-down, by mistake.

Reassembled thermostat housing with new water lines. The blue is excess gasket goo.

Reassembled thermostat housing with new water lines. The blue is excess gasket goo.

Old bolt from the anode socket.

Modified bolt with shortened pencil anode screwed onto the end