1947 CC U22 5200 Bottom Is The Only Way 1 29 2020 Snake Mountain Boatworks LLC

The thumbnail photo and subsequent footage illustrate how Chris-Craft constructed its bottoms, at least pre-1950.
• U22 Inner layer (skin): a series of eight-inch wide by about one-eighth inch thick rough mahogany planks laid in at a bit over forty-five degrees to the keel. These run full length from chine to keel.
• A layer of canvas that was soaked with a proprietary goop.
• Approximately six-inch wide by three-eighth inch thick planks running parallel to the keel.
• Thousands of tiny - #2 x ½”? – brass, Phillips screws driven from inside the bilge through the first two layers and into the exterior planks. These screws both compressed the goop-soaked canvas and transformed everything into a monolith …. well, sort of.
This combination presents real challenges to repairing just one section of a U22’s or other Chris’ bottom. Having been installed 70+ years ago, the goop is long gone and the canvas has become brittle and subject to tearing in face of minimal forces. The brass screws inevitably tear through the inner layer of planking unless every, and I mean every one of them is backed out – think of scores and scores of hours.
Bottom line: removing the planks inevitably tears the canvas and pulls a myriad little screw through the inner planking.
We hoped that, by removing only four planks – two aft garboard planks and two just outboard of the garboards, we could carefully lift these planks – after releasing all the little brass guys, of course – without destroying the canvas. Ha!
That is when reality kicked our butts. We were able to release the two garboard planks leaving the canvas largely intact. However, folding the canvas back revealed serious oil residue. The keel end of each of the inner planks is oil soaked and must be replaced.
Removing the second course of planks did provide us specific access to the damage. Then I heard, “Oh #$%^&!” Joe had just realized that both athwart bottom frames are broken in several places and must be completely replaced, which also revealed we are dealing with a house of cards.
Those frames land at the chine frames and are secured in part by long screws driven through those frames and into the ends of the athwart frames. Replacing these frames means exposing this entire area must on both port and starboard.
Doing so means releasing the outer planks, canvas and inner planks from the keel to the chine. However, the first two outer planks next to the chine run full length. The next two run almost full length. Exposing the damaged area, therefore, means removing all but four short planks that land ahead of the helm station. Since the canvas is full of screw holes and is tearing along each exterior seam between planks, it must go as well.
Our options: (The entire set of exterior planks must be released no matter which way we go.)
• A new traditional bottom. We could either try to save and reuse the inner planks, do some research and canvas the bottom soaking the material in some sort of sealer.
However, all of these thin planks from about the prop shaft log to ahead of the engine are oil soaked. The remainder are riddled with voids left by the infamous little brass guys.
Replacing all of them would be our only option.
• Install a 5200 bottom. Here we would simply admit that facts are facts. We cannot save this traditional bottom. Both feasibility and economics argue for stripping the bottom completely and installing a True 5200.
Benefits: Installing a True 5200 Bottom is significantly less expensive than is recreating a traditional bottom that must be soaked up. Her hull will be much stiffer, rider more smoothly, be safer and will never leak, and will perform for many decades to come if it is coated with bottom paint every couple of years.

We are hard at releasing the bottom now. Stay tuned …..