1930 Dodge 16′ Runabout 5200 Bottom Update 1 13 2015

We have been so busy making progress elsewhere that we have been unable to get back to the 1930 Dodge Runabout 5200 bottom project until yesterday.
As of this mid-afternoon yesterday, John, RJ and I have finished re-sawing and milling FAS grade mahogany planks – 6/4×18”x16.5’ – into a collection of 1/4×6-1/2”x48” bottom planking blanks.
John then began fabricating new bottom planks, one-by-one, since ever one is different from all the others. We find John now having fabricated all of the starboard planks, and, as the clip closes, beginning to seal each of them on all four sides with CPES.
We hope to begin screwing them down, heavily bedded in 3M 5200. In his recent article, “What is a True 5200 Bottom?” (Classic Boating, September/October, 2014), Don Danenberg is blunt about how skimping on 5200 simply translates into fool’s errand now, and troubles lurking on the horizon:
In communication with the two 3M scientists who invented and developed the 5200 product, I was told that one of their first, largest customers was Chris-Craft, who used it to replace the two-part Thiokol they were currently using in the plywood Cavalier and Sea-Skiff divisions. It was apparently tried in the main division of planked boats but added far too much in construction costs to be cost-effective. Higher-end boat builders, like Trumpy
Yacht Company, used it as their standard construction procedure after 1966.
The biggest problem I’ve seen here is inadequate amounts being used. Where I recommend 40 to 60 tubes just for the bottom plank installation, these troubled guys reported they had been billed for 24 tubes. This is simply not enough product to fill all voids. Okay, so you saved a few hundred bucks, but compromised the entire operation?” (p. 24.)
Also following Danenberg, five coats of Interlux 2000E Barrier Coat Primer will be applied once the bottom has been installed and the 5200 has cured, a process that takes 7 days.
Quoting Danenberg again from the same article:
“One of the biggest problems I have seen with short-cut 5200 bottoms is either a total lack of, or inadequate amounts of, Interlux 2000E Barrier Coat Primer. This two-part (thus epoxy) paint is a water barrier coats meant to keep the water from soaking into the bottom planks. It does that with minute platelets in the makeup that vastly slow the movement of water. Unlike hard epoxy laminating glues, it is flexible enough to move with the bottom.” (p. 25.)
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