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Background
Many will know the feeling: You paddle a few boats, learn to appreciate their strengths, to ignore their weaknesses and you get used to them. But then a nagging feeling begins to intrude, shyly at first, but then with increasing insistence. The desire grows for a particular, special boat, designed and built to your own specifications.
Beware! That initial innocent inkling all too quickly can turn into an all-consuming obsession! Watch out for symptoms like the incessant need to devour boat building literature, sleepless nights spent brooding over sketches, endless discussions with other, similarly afflicted victims – that is if one is lucky enough to find them and is not forced to torture one’s heretofore sane fellow human beings with the endless complications of the subject.
[Nowadays there’s the FoldingBoats Mailing List, of course -- sometimes referred to as “FBBA”, or “Folding Boat Builders Anonymous” -- and “non-victims” are safer once again. Ed.Tr.]
Sometimes the thought is turned into action. The following text tells the story of such a project, full of wrong turns, dead ends, but also of deeply satisfying, if painfully achieved successes.
It all began in perfect harmlessness when I was looking for an elegant, fast “Eskimo” kayak. That was fifteen years ago. I had little money and the choice of commercial boats, especially used ones I could actually have afforded, was rather limited.
First Failure
Chance and my father’s passion for collecting things led me to a set of lines drawings of an adapted west Greenland type boat in “Das Kajak” [“The Kayak”] (1928) by one Hugo Schmidt. Full of enthusiasm I built this boat in the dimensions 550 x 58 cm [18 foot 1/2 inch] with a 1.5 mm [1/16 inch] aircraft plywood skin on a very fragile skeleton of pine longitudinal members (both in rectangular and round cross sections) and plywood transverse frames. Bulkheads and hatches were part of the plan, but after I had covered the hull with a thin layer of glass mat, sanded and varnished the whole thing, set out on my first test paddle ... I never finished the boat.
All that effort and money had been wasted: The design was not very good and I had cut too many significant corners during construction.
Second Failure
A few years
later I had suppressed the lingering disappointment sufficiently to allow
a new project to start demanding serious attention: I was going to build
a folding “Eskimo” kayak. I have been using a model 450 S by “Pionier”
(a now regrettably defunct folding boat manufacturer, which used to build
excellent boats) for vacations and extended trips. The single glides nicely
and swallows up incredible amounts of baggage, but it is relatively voluminous
and slower than narrow, more modern boats.
Christian Altenhofer’s book “Der Hadernkahn” and the folding kayaks depicted
therein, some of them home-built, were probably the deciding factor. So
I started to study all available lines drawings and began to develop design
of my own to meet my high flying expectations. This phase stretched over
two years of constant changes.
In the end it was a Klepper Aerius double, which determined the construction plan. I cannibalized an old specimen because I liked the fittings and did not feel confident of my own abilities to produce something equally effective. Furthermore, I was able to recycle the gunwale assemblies after some slight modifications, like shortening them and moving the frame attachments. The kayak was 5 m [16 foot 4-27/32 inch] long by 55 cm [21-21/32 inch] wide. It has a volume of about 260 liters (plus frame and skin). The stem and stern are dead straight and have long overhangs, leaving a waterline length of perhaps 4.40 m [14 foot 5-7/32 inch].
Volker and
Marian at a folding kayaker meeting
A
deck stringer raises the centerline sufficiently to shed water without
producing so much lateral area that the boat would be greatly susceptible
to cross winds. I laminated a wooden coaming, which attaches to the boat
in the same way as the Aerius. The skin also attaches in an analogous
manner. The cockpit itself is about 70 cm [27-1/2 inch] long, rounded
in the rear and pointed at the front (so as to adapt to the shape of the
foredeck better). I built it like those found on Pionier white water folding
kayaks.
Since I was already in recycling mode, I used the ladder type double keelson
from the Klepper to build one for my boat. The result was, however, that
the cross section of the boat became rather rounded and that there was
little rocker to the keel ... which led to my replacing it with a single
keelson together with all the frames immediately after the first test
paddle so that in the end not much remained of the original boat therefore.
Why did I do that? Because before the reconstruction the boat was very long, had a lot of freeboard, would not turn easily (at least not without aggressive edging) and had a strong tendency to weathercock.
Damage Control
To counteract all this I gave the single keelson well developed rocker and added a “fin” at the stern. The Hartl-Kayak [“with the fin”] provided the inspiration for the latter. To facilitate insertion of the frame into the skin the stern (as well as the stem) plate is built in two sections, one of which remains in the skin permanently. This has the great advantage of allowing a metal strip to be screwed to the exterior of the vulnerable stem and stern, which affords optimal protection. Once again I copied this idea from the Pionier boats.
one can see
the two stem plates
The reduced volume low down in the hull, caused by the reduction in width of the keelson assembly together with the fact that the run of the stringers remained unaltered, in the final consequence caused a significant increase in initial stability.
I saw building the skin as a big problem. Since I had had negative experience with PVC tarp material for the first skin, I decided to try Hypalon. The first difficulties arose in procurement. In the end I received some second choice leftovers from the manufacturer, sufficient to build several boats. It’s lack of flexibility made it necessary to assemble the hull from three strips to achieve good fit and to eliminate creases. I joined the strips with a 3 cm [a generous inch] overlap with glue and two rows of stitching. To ensure a watertight seal and to prevent abrasion of the skin material itself [as well as the stitching] I glued further strips over the seams.
I made the
deck from blue canvas (450 g/m² [13.24 oz/sq-yard]) and added a
piece of Hypalon forward of the cockpit to protect the knees from water
that might seep through the deck material.
In this constellation the boat finally deserves being called a kayak.
It looks reasonably elegant and has adequate performance characteristics
on the water. The size of the fin (by coincidence rather than calculation)
is just right and ensures a complete absence of any weather cocking with
the help of some trim adjustments. I decided to forego a rudder even though
I would not want to miss the one on my Pionier; the reason is that I could
not solve to my satisfaction the problem of where and how to attach it
securely and effectively. Regrettably the same applies to attaching a
skeg. It is unfortunate that I have to seek out land every time I need
to trim the boat to suit the prevailing wind conditions by moving baggage.
Tracking in waves is good, maneuverability adequate. On the whole I feel significantly more comfortable in waves in this boat than in the Pionier 450 S and judge this boat to be successful despite its small shortcomings.
One more time ...
new Greenland
style single on top, re-skinned classic "Pionier" double at bottom
Perhaps I am difficult to satisfy or perhaps I’m just obsessed with building things. Pretty soon some detail or other ceased to be to my liking any more. Parts of the frame seemed too plump or heavy, the sheer might show a little more curve ...
I dreamed up new designs only to discard them again, invented detail solutions and pondered different concepts.
Then I received the incalculably valuable book by Lorenz Mayr and found instant solutions to many problems. I would like to take this opportunity to express my thanks to Lorenz once again and to declare my admiration for his exhaustive building manual, which also happens to be a pleasure to read.
[Ralph Hoehn is currently engaged in the translation into English and expansion of this book. This account of building experiences will be included in that edition.]
However, since I tend to find it difficult to subdue my own strong headedness I decided to push on with some of my own solutions. I especially wanted to retain the execution of the stem and stern plates in two pieces. I also prefer to stiffen the boat by using deep [plank as opposed to stringer type] gunwales rather than installing diagonal bracing and carlings. And I chose to install my wooden coaming once again.
I ripped ash logs, turned aluminium profiles into fittings and over time the new frame began to take shape. On the whole I followed the suggestions of the book, so I will restrict the following account to mentioning those details, which differ.
The dimensions
of the available aluminium profiles largely dictated the dimensions of
the wooden parts of the frame. I kept both on the light side to keep the
weight low. The keelson measures 24 x 24 mm [15/16 inch square],
the gunwales 12 x 15 mm [15/32 x 19/32 inch] and all stringers
are 15 x 15 mm [19/32 inch square]. I cut the frames from 12 mm
[15/32 inch] 9-ply birch plywood (“Birkenmultiplex” waterproof
to AW 100) using a saber saw. I doubled up the top sections of the frames
forward and aft of the cockpit, which might not have been strictly necessary,
but makes for a comfortable surface under which to lock the knees.
I
decided upon using 8 frames to ensure sufficient form stability [stiffness]
given the light longitudinal frame members. I would use even more frames
next time to prevent deformation of the gunwales: When the skin gets wet,
it contracts, exerts considerable force on the longitudinals and can buckle
them inward, which produces somewhat unsightly knuckles at the frame locations.
Adding further frames to offset this would not make stowing baggage any
easier, but one could decrease their cross-section to compensate.
Some of the frames are secured with Klepper fittings, others have metal angle brackets, which hook under a cross piece, which is in turn screwed to the top of the keelson. I engage [the frames with the keelson] at an angle and then push them upright. A turn-button on the keelson on the other side of the frame from the crosspiece locks them. Pegs in the frames fit into bushings in the gunwales and hold them very securely in place. Due to restricted space, the first and last frames cannot be attached in this way and are locked in place using Klepper fittings instead.
[Before anyone starts removing fittings from venerable old Kleppers, consider the simple, robust strap solution employed by Nautiraid, as well as quarter turn fasteners (made by Southco and fitted on Pouch boats) as potential alternatives. There are also simple fittings consisting of slotted metal angles that engage screw heads, which the prolific Percy Blandford favored. But we digress ...]
There are notches in the frames for the stringers, which have so far not been fastened. However, I will change that soon because I have experienced problems with stringers coming out of the notches during assembly. The stringers do not run all the way to the stem and stern plates, but end at the respective last frames. Hooks attached to their ends fit into holes in angle brackets on the frames.
Again I laminated the cockpit coaming of wood in the appropriate shape (66 X 42 cm). It has a groove on the inside face, into which I push the doubled edge of the deck material, analogous to older Klepper models. The coaming is not fastened to the frame since its only purpose is to provide a means of attaching the spray skirt. Consequently, the paddler finds the main-frame [forward of the cockpit] to be the main point of contact with the boat in.
Since
that is not quite enough, I have installed carlings at hip height. At
their forward end angle brackets with a hole in them fit over pegs in
the forward face of the main-frame. At the aft end slotted angle brackets
slide outward to engage screws in the aft face of the frame behind the
cockpit.
I cut down and installed a Klepper backrest, largely because of its quick and easy fittings, which make loading and unloading the aft section of the boat much more pleasant. The backrest also stops the carlings from sliding inward and disengaging. For the seat I appropriated an ancient, form-laminated plywood seat from a rowing skiff. Ask around in boathouses, sometimes they have things like that lying around.
Unfortunately I soon found that my feet went to sleep when sitting in the boat despite the fact that my toes push against one of the frames. I installed a heel rest to solve this. It consists of a wooden board affixed to an aluminium track and attached to the keelson with a bolt and wing nut. The board sits at an angle and its longitudinal position can be adjusted for different leg lengths (or positions) by fitting it into any of several holes in the track.
The kayak is 5,2 m long by 55 cm wide.
Once again
the skin consists of several strips. For the hull skin I used three strips
Hypalon-coated polyester, which I butted together and connected with a
zigzag stitch.
Waterproof cloth tape on the inside and a reinforcing strip of hull material
on the outside seal the seam and protect it from abrasion. To sew the
ends, I folded the skin “inside out” longitudinally, laid one end flap
on top of the other and merely stitched them together. The resulting seam
forms a ridge, which fits exactly into a groove in the parts of the respective
stem and stern plates, which remain in the skin permanently. The seam
is held in place by means of a brass strip on the outside, which attaches
to these plates with screws.
This concept has the great advantage that the considerable forces, which expanding the keelson during assembly produces, are transferred to the skin along the entire length of this seam at the stem and stern plates, rather than merely at the very tips.
I built
the deck of thick, tightly woven cotton canvas (450 g/m² [13 oz/sq-yd]).
If one wanted to avoid the high price that Klepper and Sport-Zimmermann
charge, then tent makers are an example of alternative sources for similar,
but cheaper material. However, they do not [appear to] carry the
classic [folding boat] blue. After pondering the alternatives I
decided to go with an off-white in the end. It is already pretty stained,
but you can always brush it off if required. Above all it is light inside
the boat! Gone are the days when I had to use a flash light to look for
small pieces of equipment or for signs of damage in the ends of the boat.
I reinforced the deck with lighter gauge hull skin material, mainly for
aesthetic reasons.
I sewed the
deck and the hull together inside out. To add a little color accent to
the otherwise grayish drab appearance of the skin, I tacked cotton seam
tape to the deck edge before sewing. I similarly tacked fabric loops holding
D-rings to the deck edge before stitching everything together. I was loath
to sew these onto the deck itself, fearing that there they might at best
potentially tear off and at worst do more or less severe damage to the
deck itself just at the most inconvenient moments.
The very low-cut hull glides easily. However, at high speeds it tends to bury the stern and appear to get sucked down. Apart from that though, and bearing in mind its purpose, which was not racing, I am very happy with this boat so far. In fact, I’m so satisfied with it that I have yet to begin planning the next one! Although it would be a challenge to redraw this kayak to become more suitable for longer trips: Perhaps a little higher and a touch beamier ...
The perfect
boat ...until I start the next one ...
Conclusion
It is quite possible to construct very useful folding kayaks with the simplest of means at home. A little handiness is required and a lot of patience, the latter to allow the builder to weather the inevitable set backs without allowing discouragement to creep in.
I advise anyone who has ever toyed with the remote possibility of building a kayak to start immediately. I say immediately because such a project will take time, which could otherwise be spent on the water, but also because there is no such thing as the perfect boat. The search for that elusive perfection can take you in many different directions. It is worth while to follow as many of them as possible, in order to see if one or the other may not show a path that approaches such perfection very closely after all.
[more pictures? Two Greenlandic Folding Kayaks on river Schwentine]
[Translation by Ralph C. Hoehn, who will gladly pass on any comments to Volker after the requisite linguistic transfiguration.]
Disclaimer: All material is copyright by the original author.