A Riva in a Barn

By Bjorn Bakken, Bay State Classic Boat Club

While living overseas in my country of birth, Norway, from 2012 to 2014, a childhood friend told me: “I know of a rare wooden boat in a barn.” Many of us have heard of stories like this, but it’s like winning the Lotto when you see the recognizable shape of a Riva that an owner is interested in selling. Most of us in the classic boat community know that Rivas are rare and hold their value. The terms were agreed on and the boat came home with me.

This 1958 Riva Florida, the smallest of Carlo Riva’s inboards, had been with the same owner for over 25 years. It was original and complete but had been used hard. The boat had sunk in fresh water, then quickly raised and placed in the barn. The original Chris-Craft KFL engine was removed and preserved.

It sank because of its original bottom. These boats were built light, and the 9-millimeter (3/8-inch) plywood bottom was screwed to the frames with a linseed oil based sealant. The sealant had long since dried out, and the screw holes were well rounded after many years of fun on the water.

After documenting the boat with hundreds of pictures, all the hardware, interior pieces and engine were taken out. Reinforcements were screwed into the frames so the boat could be turned over. The old bottom was removed, which brought the broken and rotten frames to light. The 2 3/4-inch thick keel is intact but had a significant bend underneath the engine.

Next it was time to check each frame – wood with damage or rot must be replaced. If in doubt, it’s better to replace one too many. Here you must use the right materials. Riva used Sipo, an African mahogany, in all frame construction.

One by one, the bad frames were removed. New ones were cut and assembled the same way as the original construction. Riva used copper rivets in all transitions between bottom and side frames. One place where I took the liberty to change the original construction was the keel. It was a single piece of mahogany. Instead, I laminated three pieces of 7/8-inch boards together for a stronger construction.

Now with a new, straight, and strong foundation, it was time to lay a new bottom. Carlo Riva started using molded mahogany plywood bottoms in the early 1950s. He used 9-ply, 9-millimeter (3/8-inch) thick panels. When choosing plywood, there is only one choice for marine underwater use: those that are manufactured according to BS-1088 (British Standard). The difference between other WBP plywoods and marine BS-1088 plywood is the use of “A” grade mahogany veneers in all layers, i.e. no voids in-between the layers.

There are two common ways to lay a new Riva bottom. One is to use 3/8-inch flat sheets and, with force, press them onto the bottom frames. In my opinion this is not optimal as it is difficult to press and screw the 3/8-inch thick sheets all the way down to the frames, especially at the bow.

Personally, I find it best to epoxy laminate three layers of 3-ply, 3-millimeter plywood, a so called “West system bottom,” which is well described in the ACBS member video archive. You get a molded bottom that is incredibly strong. The important thing here is that you do not coat the inside with epoxy, thus encapsulating the frame and keel. This will cause rot in the coming years. Only two coats of good old fashioned oil based bilge paint in the gray-blue Riva bilge color are needed.

A good primer, hard racing or antifouling bottom paint completes the bottom. I used two component Polyurethane on this boat since it will only be in the water for a couple of weeks every summer and transported on a trailer. Riva had a deep green bottom color in the 1950s, with two 18-millimeter white water lines.

With the boat turned around again the time had come for the sides and decks. 1958 was the first year Riva used molded sides. The sides were made in a large press, with two layers of 3-millimeter thick mahogany veneer placed diagonal to each other and a 6-millimeter outer layer lengthwise. Riva used only full length boards on all their boats; there are no butt joints.

In the 1950s, Recorcinol was the adhesive of choice for marine use. The glue was brown/black in color, and the “trip” under water had colored the outer layer on the sides. The boat had the infamous zebra stripes, where one can see the joints from the underlying layers. The last – best option to get rid of these stripes is to bleach the wood. This takes some of the color away from the mahogany but can be corrected later with a slightly darker stain. First thing was to remove all of the old varnish. I find the best way is heat gun and scraper. This is the world’s most boring job!

Then came hours and hours of sanding by hand with long boards. One must remember that the outer layer was only 5-6-millimeter (less than 1/4-inch) when the boat was new, and one must assume that it has been sanded and revarnished before. It wouldn’t take much to sand through. I sanded with 16- and 36-inch long boards to get a smooth, fair surface. Diagonally, 45-degrees bidirectionally, and then along the grain at the end. Sanding only to 120 grit gives a good adhesion surface for stain and varnish. With the rather course finish sanding, a few extra coats of varnish are needed. But you get a finish that lasts much longer and you avoid potential problems with the varnish flaking off after a couple of seasons in use.

In Europe, the go-to stain for Riva is “Pasta Mogano” from Stoppani. It is a two component thick paste that must be diluted to a thick paint consistency. The stain is applied evenly by brush and rubbed into the wood with cloth rags. Riva decks are left natural blonde without bleaching or using a blonde stain.

Since this boat has a plywood construction and minimal wood movement, I used Epifanes two component polyurethane clear coat. Three coats were applied over three days, allowed to cure for a couple of days, then sanded with 320 grit and then the process was repeated. For the best result, the project is put away for eight weeks or more after 15-16 coats, to allow the finish to off-gas. The last four coats are done with sanding in between each. I applied the polyurethane with the roll and tip method. You must thin the polyurethane according to the ambient temperature and humidity so that it flows out. Some trial and error must be taken into account here.

The time had come for the reinstallation of hardware, engine and interior. There are sources in the US and Italy that specialize in Riva parts and reproduction fabric with the right color combinations. For my 1958 Florida it should be yellow with black/white gingham. I had the Chris-Craft instruments restored in the US. It feels good when everything comes together.

The first time in water is always exciting. Does everything work? Is something forgotten? With old engines there is always something. It started and ran but it was soon clear that the original Chris-Craft engine had to be completely overhauled. Parts were shipped from the US to Norway, where a local machine shop did a complete rebuild. 

Over the last six to seven years we’ve enjoyed the boat each summer while back in my motherland. We have also taken the boat, now named Rubia (Blondie), around Scandinavia and Europe for classic boat events. She has even been towed 3,500 miles roundtrip from Norway to Italy a couple times for Riva meets.

But the best of it all? Letting the next generation experience the joy of a classic wooden boat.