Guppy Trailer, Part 3: fabricating the components

I have been cranking away on the trailer as fast as I can, so I am inserting this blog post after-the fact. This page describes the fabrication of the components.


Here is the left sidewall, under construction in our living-room. A few things visible in this image:
1) On my dad’s advice I sanded the first layer of varnish with 400# sandpaper, cleaned off the dust, and applied a second coat. My goodness! what a glassy sheen!
2) The unvarnished white stripe in the foreground is where the rear bulkhead will be attached. I left it bare for better glue-adhesion.
3) Wall studs have been glued and screwed to the outside of the wall-panel. Two un-trimmed studs are visible at right, and a regular grid of screws across the face of the wall panel are faintly visible.
4) The inside-rib along the top of the wall-panel will be a guide-rail for the thin ply that I will bend in to make the ceiling.


Here is the same left-side wall panel, with the varnished inside face laid down on the new flatbed trailer. Rick Storrs made a great suggestion for windows which saved me time: rather than figure out operable windows, I would build simple, fixed windows and install vents to provide for ventilation. I placed five vents in the left wall: three low, and two high. I needed a rigid, cylindrical spacer to run the vent through the wall-insulation. What you see in the picture above is 3″ internal-diameter pipe, cut into 1.5″ segments, to provide a rigid passage between the outer and inner layers of the wall.


Here I am correcting a major mistake. I thought I had bought 1/2″ ply, in which case 3 layers would add up to 1.5″, the same thickness as the wall-stud depth and insulation thickness. However it was 3/8″ ply, so 3 layers added up to 1.15″ (with glue), not 1.5.” To make it work, I had to peel back the topmost layer of ply lamination, then add one more 3/8″ to flush it up to 1.5″.


And here is my biggest mistake: I used aluminium L-brackets at the base of the wall, to be fastened with stainless-steel screws. When exposed to moisture, the electrolytic reaction between these two metals would disintegrate the aluminium.

My solution was to coat the bolt-ends with Lexel, which is like silicone sealer but even stickier. My hope is that by entombing the connection, I will minimize the chances that water will be able to trigger the electrolytic reaction.


After many days of cutting, laminating, and grinding the ribs until I had full-length composites that matched, I began joining them together using cross-blocking. The easiest way to attach the blocking was to hold it against the rib using a “Pony” 90-degree vise. A dab of glue, a pre-drill and an end-screw, and the connection was done and strong. End-screw construction meant that the blocking could not line up across the rib-cage, but I did not worry about this because the ribcage would be covered, inside and out, with layers of thin bent plywood.


What I had not anticipated was that the overall pattern would be so beautiful! I’m glad I photographed it; I’m sorry now that it will disappear under a smooth layer of plywood.


Now, the key components are fabricated. Foreground: you can see the L-brackets, epoxied onto the blocking of the rib-cage. Background: on the far left is an old futon frame [not part of this project]; the plain rectangle of plywood next to that is the rear bulkhead; on the right are the two side-walls. I still haven’t cut the window-holes in that lovely glossy surface, but time-pressures will compel me to do that soon enough.


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