1930 Dodge Runabout True 5200 Bottom Progress Update

Installing the Minnow’s True 5200 Bottom is progressing nicely. Three-quarters of the bottom planks have been fabricated, which has turned into a near-Herculean task. Why? None of the planks has parallel sides, and the degree to which each plank tapers from chine to keel differs from board to board.

And using the boards from one side as patterns for the other? Well, they are close, but close does not deliver perfect mating with the two boards on either side of the one being fabricated.

John has patiently sanded every plank in using our 36” horizontal, stationary belt sander.

As you see, we lay all the planks out, placing one positioning fastener in each, and then laying out a grid for all the fasteners, and drilling all of the countersink holes, so that the planks end up screwed down where we want them to be.

We test as we go, choosing between #6 and #8 silicon bronze, Frierson wood screws ranging from ¾” to 1-1/2” long.

Why not stainless? Read Danenberg’s article in the Sept-Oct 2014 issue of Classic Boating magazine to find the clearest, science-based, and most objective explanation I have read yet. Each plank is literally buttered with a 1/8” thick layer of white 3M 5200. Why not mahogany? It costs about 50% more because of the color alone. Since it will end up hidden by five coats of Interlux 2000E Epoxy Barrier Coat Primer, selecting mahogany just wastes money.

As you see, John drives the screws in with an impact gun, and then pounds and pounds the edge of the plank with a large rubber hammer. Doing so drives the 5200 all the way out and beyond the plank’s edge.

What we did not show was the next, not-so-fun step, cleaning the excess 5200 from the plank’s face, edge and surrounding area. Pay special attention to cleaning the trailing edge so that the next plank fits snuggly in place.

Interlux will happily sell you 202 or 216, or some other more exotic solvent. Acetone is our go-to solvent throughout the shop. Unlike the expensive thinners, it flashes off almost immediately, and leaves no residue behind, oily or otherwise.

As John remarks in the clip, “There is nothing clean about installing planks as part of a true 5200 bottom!