Duckworks Magazine

Skin on Frame

By Ross Miller - West Mystic, Connecticut - USA

On The Virtues of the Fuselage-Frame Skin Boat

Full disclosure: The plans for Egret, a fuselage-style skin-on-frame kayak of my own design, are available from Duckworks. One might therefore be inclined to think that this article is entirely self-promotional, and that I’m just singing the praises of the fuselage frame because I design kayaks this way, but that is not accurate. The article is only partly self-promotional, and I really believe what I say about fuselage frames, otherwise I wouldn’t design them this way.

The word “fuselage” is from the French for “spindle-shaped” and is an aircraft term. Its use to describe a method of skin kayak construction may be more recent than the method itself, but it’s helpful in that it differentiates the type from boats built in the traditional arctic style. The similarities between boat and aircraft construction are apparent, and we know which came first. Boats had frames and longitudinal timbers (and were covered in skins) long before aircraft were a gleam in Leonardo DaVinci’s eyes, and even the earliest non-log boats mimicked the spine, ribs and skins of endoskeletal animals. The basic methods are old.

Modern fuselage-style skin kayak construction came into being with the availability of sheet plywood, which made the getting out of frames a much easier matter. Rather than construct a five- or six-sided frame out of as many pieces of wood, each could be cut out of the plywood in one piece, simplifying matters immensely. Percy Blandford’s designs were early examples, and the method had its heyday in the 1950s and 60s, when my dad and many others ordered plans and kits from Popular Mechanics.

Percy Blandford’s designs were early examples of modern fuselage-style skin kayak construction.

Somehow the method has languished in the intervening decades. A couple of venerable plans catalogs still stock vintage skin kayaks, but there are only two contemporary designs other than my own that I know of. This is unfortunate in the large view of things, but on the other hand it affords me the opportunity (full disclosure again) to scuttle, like an opportunistic hermit crab, into this unoccupied niche and wave my flag.

I do not exaggerate when I say that a fuselage-frame skin boat is the cheapest and easiest way to build your own kayak. Materials for a basic Egret are less than $300, much less expensive than plywood or strip-built kayaks. All wood can be purchased at a lumberyard, and even if the builder elects to use okoume ply for the frames, the cost remains within this parameter. Heat-shrink Dacron is less than $4/yard. Even the addition of Xynole polyester fabric and epoxy, if one prefers a laminated skin, does not send the bill through the roof.

I do not exaggerate when I say that a fuselage-frame skin boat is the cheapest and easiest way to build your own kayak.

Building a fuselage-style frame is about as easy as boatbuilding gets. The building jig can be as simple as a straight 2x6, although the instruction book included with Egret’s plans shows how to make a plywood box-beam strongback. The keel is a length of 3/4” x 1” wood, slotted at either end for the stem and stern pieces. The frames and bulkheads are easily cut out using the full-size patterns, then are positioned on simple uprights and glued to the keel. Stringers are bent around the frames, glued and screwed to the stem and stern and also glued to the frames. The bends are gentle and do not require steaming. Not much to it, is there? After that, there is the cockpit opening. Two thin laminates are bent into an oval for the cockpit carlins. Some steaming is best here, but that can be accomplished by wrapping the wood in towels and saturating with boiling water. No need to build any elaborate steam-box contraption.

For the cockpit opening, two thin laminates are bent into an oval for the cockpit carlins.

Egret is not just a rerun of mid-20th-century fuselage-style kayaks, though. The filleted epoxy joints at the intersection of every frame and longitudinal permit the use of thinner plywood and stringers than are found on older skin boats.

The filleted epoxy joints at the intersection of every frame and longitudinal permit the use of thinner plywood and stringers than are found on older skin boats.

1/2 inch ply was the standard in the 50s and 60s, but Egret does just fine with 1/4 inch (6mm). That’s a significant saving of weight, and thinner frames permit some flexing while retaining the box-like strength of the glued joints. One can wiggle the end of a naked Egret frame as it sits on sawhorses and wonder if it’s too flexible, but once the skin is attached and shrunk taut, everything is brought into balance.

Once the skin is attached and shrunk taut, everything is brought into balance.

Heat-shrink Dacron is a modern miracle. Anyone who has wrestled with #10 duck canvas and copper tacks will appreciate how easily Dacron attaches to the frame. The fabric is draped over the frame, then pinned and slit at the ends. The appropriate contact cement is applied to the stem, stern and to the sheer stringers, and the fabric is attached. There is none of the hassle of chasing wrinkles by pulling and repositioning tacks, as is the case with a canvas skin. Dacron is a lighter and more pliable fabric, and any minor wrinkles flatten out when it is shrunk with a common household iron. Neither canvas nor other synthetic fabrics have the shrinking capacity of aircraft Dacron, and they are much harder to work with.

Anyone who has wrestled with #10 duck canvas and copper tacks will appreciate how easily Dacron attaches to the frame.

The addition of a layer of Xynole polyester and epoxy over the Dacron skin is yet another example of how modern materials improve the genre. An outer layer of Xynole adds a bit of weight, but increases the strength of the skin considerably and provides a high degree of finish. Sometimes it’s hard to tell it’s a skin boat because of the smooth, faired surface. Xynole is known for its abrasion resistance, and I suspect it would be hard to rip this composite skin with anything short of a sharpened narwhal tusk. Hypalon, used to coat inflatables and river rafts, is another high-strength way to augment the already tough Dacron.

Put all these innovations together and the fuselage-frame skin kayak becomes a new creature. I’d call it a kayak for the 21st century, but that would be trite. I’d call it a young athlete compared to an old sack of bones, but that would be unfair to your father’s skin boat, which, after all, was a lot of fun. Let’s just say that we have new ways of doing a fine old thing.