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Systems:  Diesel Engine:  Engine Foundation

Engine Base Template

In February 2004, I built a plywood engine template so that I could visualize the engine shape and position.  At the time, the template was important in assisting me to determine the eventual height of the cockpit deck so that I could make some cuts in the newly-installed bulkheads.

To build the template, I simply followed a measured drawing of my planned engine that I found online.  The drawing provided the necessary dimensions and shaft center offsets to construct an accurate template. 

Now, in March 2005, it was time to actually begin constructing my engine foundations. My Vetus M2.06 diesel engine had arrived, and after confirming that the actual measurements gibed with those in the drawings (from which I had built the template), I proceeded with the preliminary work required to build the foundations.  First, though, I installed the supplied Vetus flexible engine mounts onto the platform, carefully locating each hole in the appropriate place.

Next, I prepared to install an alignment string through the shaft log, which represented the exact centerline of the propeller shaft.  Since I had removed the old stern tube earlier, slated for replacement, I cut a length of the new fiberglass tubing longer than required, and cut two temporary plugs for the ends to help center the string in the opening.  To make each plug fit tightly, I wrapped the edges in black electrical tape for a snug fit inside the fiberglass tubing.  I couldn't help thinking that my arrangement resembled a pipe bomb.  I secured the bitter end of the string with tape on the outside.

I continued by installing the length of fiberglass tube in the oversized hole in the keel deadwood.  I pinned it in place with some wooden stir sticks (tongue depressors) and roughly aligned the tube by eye.  While I wanted my initial engine template alignment and foundation construction to be as accurate as possible, I had some leeway, since I planned to actually delay installing the stern tube until the engine was bolted in place.  Then, with a length of shafting, I could actually align the stern tube perfectly to the engine, rather than the other way around.  But that's for later.

To secure the forward end of the string, I borrowed a metal door handle from a fixture in the shop and temporarily screwed it to the bulkhead at the forward end of the engine room, after eyeballing the proper height.  The handle gave me some side-to-side adjustment leeway for the string.  Then, I secured the string in place, ensuring that it ran through the dead center of the temporary shaft log.

Next, I prepared to install the engine template over the string.  The template included holes that represented the centerline of the shaft, so by running the string through these holes (which contained slots at the bottom to allow the string to be slipped easily in and out) I ensured proper alignment and placement.  To help hold the template in place, I rigged up a pair of simple slings, made of string, from the deck beams above--a most convenient arrangement in this case.  By adjusting the strings, it was quite straightforward to position the template properly, with the alignment string running through the center of each hole in the template.

By now, it was nearly the end of the day.  Before leaving, however, I prepared my engine foundation blanks.  I had decided to build them from laminated Meranti plywood, which I had an abundant supply of in the shop and which I felt would be very suitable for use in this instance.  I cut eight pieces of Meranti, each 12" wide by 24" long, and glued up two blanks of four pieces each for a total thickness of three inches, stacking them and securing them with thickened epoxy resin.  I clamped up the blanks and left them to cure overnight.

Fabricating the Engine Foundations

In the morning, I unclamped the blanks and cleaned up one of the edges with a belt sander; then, I ran the pieces through my tablesaw for a consistent size and for straight edges all around.   When the two blanks were cleaned up and free from excess resin, I was ready to continue with installation procedures.

To make it easier to visualize and measure the distance beneath the mounts, which equated to the height of the foundations required, I fabricated a pair of simple pine brackets, consisting of a flat horizontal piece (which would fit beneath the mounts on the template) and a pair of vertical supports that I could clamp or screw to the deck beams.  With these, and quite a bit of fussing around to ensure that the alignment remained proper, I could support the engine template in place and remove the strings. 


Then, by measuring the distance from the top of the new pine supports (equal to the bottom of the flexible mounts) to the hull beneath at both bow and stern, and at a predetermined width at each end from the centerline of the flexible mounts' boltholes (3", or 1-1/2" either side--the same as the thickness of my built-up engine foundation blanks), I could determine the rough dimensions of the foundations needed.  To aid in measuring, I secured a thin strip of scrap over the top of the pine supports, and measured to the bottom of the scrap as seen here.

After marking the cut lines on the blanks, I cut off the waste section with a circular saw, making two passes (one from each side) to complete the cut.  Then, I fine-tuned the cuts with a belt sander.  Test fitting was made easier since the blanks should have fit directly and tightly beneath the pine supports that were still in place.  My first test fit showed that I had to remove material, and so it continued through several test fittings on both sides. I carefully removed material with the belt sander as needed, until the foundation blanks fit properly in the space beneath the pine supports.


With each blank properly sized, I used a router and two different bits to ease the various edges for ease of later glasswork:  a 1/2" radius on the vertical edges, and a 1/4" radius (to avoid removing too much of the flat top surface where the engine mounts would rest) on the upper two edges.  After some minor sanding, the foundations were ready for installation.

I set the foundations in a bed of thickened epoxy against the hull, applying a thick amount that I knew would fill all voids beneath the mounts.  It was convenient to use the pine supports to hold the foundations in place during gluing; I drove two screws through the pine and into the foundations, holding them securely.  I created fillets as needed on the edges of the intersections, which would make later glasswork easier.  Then, I left the foundations to cure overnight before proceeding.



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