RETROSPECT
String Theory
High-tensile fastenings stand the test of time.
Lashing and sewing, among the oldest of technologies, remain competitive with the best. String was not invented — it was discovered: as vines hanging in the tropical jungle, sinews exposed when carcasses were scavenged in the savannah, tendons and baleen fibers appropriated by arctic hunters who took sea mammals apart. Net making is even older: witness the highly evolved spider’s web.
The puzzle is not why did human beings start lashing things together, but why did they stop? We still sew our clothing, sails, and tents, and our surgeons still sew us, but we no longer sew or lash much else. The few exceptions — like the carbonfiber skeleton of the Gossamer Albatross, Paul MacCready’s human-powered aircraft that crossed the English Channel in 1979 — are rare. Ironworkers still assemble the steel backbone of our reinforcedconcrete-based civilization with tie-wire, but these temporary lashings are quickly covered by cement. Anything that is lashed together is dismissed as jury-rigged or haywire, makeshift at best. We only tie things together after they break. Lashing survives on the front line of emergency repairs, not because it is primitive, but because it handles loads — especially the sudden loads that break things — so well.
“In pure strength, apart from their flexibility, the lashings, sewings, and bindings used by primitive peoples, and by seamen down to recent times, are more efficient than metal fastenings,” argued James E. Gordon in The New Science of Strong Materials, the best study ever written on why some things hold together and why other things fall apart.
When Thor Heyerdahl built the Kon-Tiki for a voyage across the Pacific, its structure was lashed together, not only to prove a historical point, but because this was the only method of fastening that held any hope of keeping the soft Peruvian balsa logs from falling apart. When Fridjtof Nansen and Hjalmar Johansen left their ship, the Fram, frozen in the polar ice at 84°N in March of 1895, to see if they could reach the pole on their own, they took lashed-together sledges and bamboo kayaks, and made it back to Franz Josef Land — 15 months later — alive. Their survival hung by a thread. “When, for instance, a rib had to be re-lashed,” explained Nansen, “we could not rip up the old lashing, but had to unwind it carefully in order not to destroy the line.”
When I built a treehouse 95 feet up in a Douglas fir on the coast of British Columbia (see MAKE, Volume 05, page 190), I used #15 tarred nylon seine twine to tie the framework to 14 different branches, not because I had any objections to pounding nails or driving lag bolts into living wood (working around logging camps had cured me of that), but because I wanted to be sure that house and tree remained attached. The entire structure had to be able to flex wildly in 60-knot winds, and no mechanical fasteners were flexible enough.
The puzzle is not why did human beings start lashing things together, but why did they stop?
Photograph by Beverly Dobbs, ca. 1906, courtesy Baidarka Historical Society
I adopted lashings when I began constructing aluminum-skeleton kayaks, not for historical authenticity — or I would not have used aluminum — but because tensile fasteners made practical sense. When two pieces of high-tempered, thin-wall aluminum tubing are attached with eight turns of 60-pound test twine, you can be sure that it will take something close to 8×4×60, or 1,800 lbs., to pull them apart. There is no risk of metal fatigue, and the joint will flex elastically (and repeatedly) long before it breaks. Shock absorption is built into every joint.
If you sew two pieces of tempered aluminum plate together, there is no loss of temper as in a weld, and none of the corrosion that affects metal fasteners
Left: Siberian trading party in Nome, Alaska, after crossing Bering Strait in their skin boat.
Right: Joe Ziner and Lou Kelly in the author’s kayak-building workshop at Belcarra Park, British Columbia, March 1977. In four months, using miles of braided nylon twine, we lashed together six 28-foot, 3-hatch baidarkas (kayaks), and launched them on a voyage north. The frameworks are 6061-T6 aluminum tubing, 6061-T6 aluminum sheet (from salvaged road signs), and Sitka spruce.
Below: The author lashing the bow assembly for a one-hatch baidarka, 1981, using 60-lb. test nylon twine. The holes in the aluminum are carefully countersunk. If the twine breaks frequently you are applying too much tension; if it never breaks you are not applying enough.
Photograph by George Dyson (above); photograph by Ann E. Yow (below)
RETROSPECT
in the presence of salt. You can safely predict the ultimate strength of the resulting assembly, since the lashings will bear the load equally, and there are no hard stress points to form a weakest link or to propagate cracks. When you sew a seam on a thick nylon kayak skin with four 40 lb. test stitches every centimeter, you can count on the seam taking a load of 200 lbs. per inch without tearing apart.
Not only are lashed fastenings unusually robust and structurally sound, they are pleasant to work with, are forgiving of sloppy craftsmanship, and celebrate the abilities of human hands. If you complete a seam or a lashing and decide it could have been done better, you just undo it and try again. You can stop work at a moment’s notice, and resume at any time. You can strive for perfection, but a haphazardlooking lashing will be almost as strong.
Traveling through heavy seas in a loaded and lashed-together kayak, there is a reassuring creak in the vessel’s joints, similar to the old days of loosely fastened wooden sailing ships, designed to work in a seaway for months and years on end. In a modern welded or composite vessel (or aircraft), any sounds emanating from the structure are cause for alarm.
With a load-bearing structure that is sewn or lashed together, what you see is what you get. Finite element analysis (FEA) is now used, in association with computer-assisted design, to predict stress, requisite materials, and required fasteners in a given structure under a given load. The empirical design of lashed structures is the ancestor of FEA. Lashings (and the elements they join together) are finite elements, and can be used to handle stress (and predict strength) in a directly analogous way.
If we examine how nature joins high-strength, high-stress materials — mending a broken bone, joining the plates in a baby’s skull, healing a cut in an animal’s skin, or attaching a mussel to a rock in the surf — we see lashings at work, on a microscopic scale. In designing and building our own structures, we can do no better than to emulate nature. We have, and we will again.
Approximately 35,000 years ago, a small band of human beings launched into the open Pacific Ocean from Malaysia in lashed-together vehicles. The experiment was a success. Why stop?
George Dyson, a kayak designer and historian of technology, is the author of Baidarka, Project Orion, and Darwin Among the Machines.
Baidarka (kayak) construction, circa 1986. The completed 5-meter (16.4-foot) skeleton, made of 1/16" aluminum sheet and ½" o.d. 6061-T6 aluminum tubing (.049" wall) weighs 18 lbs. The skin material shown here is a 26 oz., (per square yard) double-weave heat-shrinking nylon. The twine is a phenolic-coated nylon obtained at very low cost as remaindered tire cord.
Photography by Ann E. Yow