I Just finished building a Fly Fisher, mostly to do something fun during the pandemic shutdown and, secondarily, to have a lightweight rowboat that my wife and I (and our grandkids) can load onto a homemade cart and wheel a few blocks down the street to the Long Island Sound. I’d like to share a few tips and insights with the Forum on what I learned building this small SOF boat. Launching photos will need to wait until the Spring, however.
There is a lot of contentious discussion in SOF on-line communities on whether it’s better to skin the boat in nylon or dacron fabric, or whether you should use exterior or marine ply for the frames, stem and transom. In the past, I’ve used Okoume or Sapele marine plywood for all my boatbuilding. Fuselage-frame boats, however, use so little plywood that it just wasn’t cost-effective to use the “good stuff,” simply because buying a single sheet of marine ply from Boston or NY would either cost more than the ply itself in having it shipped to me or involve a five-or six-hour round trip if I were to pick it up myself. The only locally available marine ply was fir, which eventually always checks unless laboriously covered with fiberglass set in multiple layers of epoxy and then painted with multiple layers some UV-resistant coating, with lots of sanding between each coat. I bought a sheet of MDO from my local lumberyard instead.
What I discovered is that MDO initially seems like a decent boatbuilding material, because it has a waterproof surface (which was also pre-primed in the brand I purchased) and weighs far less than Sapele or fir marine plywood, which is also a significant benefit in building a lightweight SOF rowboat. Prepping MDO is also a lot easier, cheaper and quicker then with marine plywood, since only its edges needed to be epoxy sealed, sanded and coated. On the other hand, its softwood core had a few interior voids that had to be filled and was only three layers thick. This means that it’s far less strong than marine ply, which would typically have five to seven plies, even though it costs about the same per sheet. For example, I had one of the MDO frames crack after flipping and moving the boat around during assembly. To counter its relative fragility, MDO does not require the tedious application of multiple coats of expensive epoxy, high-tech fabrics and UV-resistant paint or varnish to protect its surfaces against water infiltration, rot, checking, and delamination, thus saving a lot of time, sandpaper, and money. You can build faster with MDO, but maybe not have the longevity that a stronger, higher-grade marine plywood would provide.
A few more points about building Fly Fisher’s frame:
· In response to an earlier entry in this forum about Fly Fisher lofting errors, the frame 12 offsets are accurate, and the bottom of the frame is actually slightly concave when lofted (as you can clearly see from the line drawing on the bottom of page 53 of “More Fuselage Frame Boats”). This frame concavity, however, requires a lot of finicky fitting and rasping to get the bottom stringers to lie properly against the keel batten for lashing to the bow stem. Also epoxied a few small pieces of plywood to the upper part of frame 12 for reinforcement and drilled the frame out for two short ½-inch dowels driven through the frame to serve as built-in cleats for an anchor or dock line (though you can always tie off any lines to the inwale in the spaces between the gunnel blocks).
· George Putz, in his book “Wood and Canvas Kayak Building” is pretty adamant about the need for an external wood keel batten to strengthen his kayak’s internal keel batten and help protect its bottom, even though Horton’s plans call for a flat-bottomed boat. Given the relative weakness of the MDO frames, I thought adding this external keel was a good idea and installed a ½-inch by ¾-inch batten caulked and screwed through the boat’s bottom into the inner keel batten after the boat was skinned.
· I also thought the structure would be greatly strengthened by building an inset breasthook and adding two wood transom knees to terminate the inwales and outwales in order to supplement the transom knee brace lashed to the internal keel batten and the side and bottom battens lashed to the stem. Like the knee brace, the transom knees were screwed to the transom and wales and the breasthook screwed to the outwales using stainless deck screws (whose flush heads are hidden by the skin and outer transom). Both make the boat look very “Old School” and traditional and are highly recommended for aesthetic reasons as well as structural ones.
Even though the Fuselage-Frame Boat books recommend nylon and dacron skins, I bought six yards of 72-inch wide 10 oz. canvas for the skin of my boat. I chose this covering over the more modern materials simply because I had read George Putz’s insightful book, “Wood and Canvas Kayak Building (1990),” and became curious about using a “traditional” 19th Century SOF skin instead of the “high tech” skins that are used for SOF boatbuilding today. I figured the painted canvas skin should last 5-10 years with care, annual upkeep and indoor storage and the boat could always be easily reskinned with more exotic fabrics if it rotted out before then.
In order to expedite needed future reskinning or canvas repair, the boat’s exterior components (outer transom, rubbing strips and keel) were all screwed to the frame after being bedded with caulk. A quick pass with a utility knife would separate the caulk line and a screwdriver would easily remove the components to give quick access to the stainless staples holding the painted canvas to the frame. So, following Putz’s advice, I built the boat to be as easily deconstructed as it is constructed.
A few points about skinning with canvas:
· Skinning is a two-person job. You may be able to do it yourself, using a lot of clamps to hold the skin while you are constantly running from one side of the boat to the other as you stretch and fasten, but it’s a lot easier with one person stretching the skin and another person fastening. It took me about two hours to skin Fly Fisher with the help of a pal. It’s also a lot easier using 72-inch wide fabric (this will cost you less than $5 per yard and will drape about 4-inches either side of the gunnel at the boat’s widest beam).
· Buy a power stapler and use monel or stainless steel staples. You will be driving hundreds of staples through the skin and a T-50 manual staple gun will soon become very, very, very, tiresome to use. So use a pneumatic stapler (if you have a compressor) or buy a $30 or $40 electric staple gun for skinning the boat.
· It’s a lot easier to trim the fabric at the gunnels with a sharp knife or razor blade after it is primed. Otherwise the edge starts fraying. This is exactly the same technique used to trim fiberglass after it’s epoxied, for exactly the same reason. Using more high-tech fabrics might require using an electric knife to melt the fabric edges to prevent fraying, but I don’t have the experience (nor the tools) to know much about this technique.
· “Filling the weave” of the 10 oz. canvas duck for Fly Fisher needed a full gallon of oil-based Petit EZpoxy marine primer to waterproof the fabric, in the form of three thin coats of primer. It also needed a full quart for the two thin coats of oil-based topsides paint. This amount of marine paint is both expensive and heavy (adding 8-10 pounds to the boat’s weight). I’d guess that maybe 20% of Fly Fisher’s total weight is in its coatings, and that the marine coatings account for maybe 25% of the boat’s total cost
· Cotton canvas stretches and shrinks based on its relative humidity. Some days the skin is tight as a drum and on other days you can see some ripples. This has implications for the longer-term integrity of the surface paint (although the thick primer layer seems to accommodate all the fabric’s movement). I used a hard-surfaced acrylic marine topcoat paint for Fly Fisher, but might want to consider a more flexible paint alternative (inflatable boat paint? Latex house paint?) if I should ever need to repaint the boat.
All in all, I enjoyed building this SOF boat and am quite happy with its design, even though I won’t be launching it until next Spring. It’s a looker and its lines also suggest good rowing performance. I will be installing buoyancy bags under the seats for safety and will report back to the forum next year, after it’s in the water.