Glossary of Terminology found in and around Folding Skin-on-Frame Boats
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2. We include the equivalent German terminology (enclosed in square brackets, the definite article follows each term to designate the appropriate gender) because there is a lot of material on folding boats written in the German language since this concept was most popular during the early portion of the 20th century in the German speaking countries.
The term baidarka is derived from usage in Russian language meaning "small
boat", the diminutive of "baidara". In the context of arctic skin-on-frame
boats it describes a long narrow hunting boat propelled by single or double
paddles. There are a variety of spellings including bidarka et al. The
term baidarka has been most closely associated with boat designs deriving
from indigenous northern Pacific types found both on the north American
and the Asian shores. One to three paddlers using single or double bladed
paddles propel "Baidarka" type kayaks.
Beam: [Breite, die] Strictly speaking in the terminology of the formal designer, the beam of a boat is its half breadth. This definition has come about because lines drawings of a particular boat design most often only show one half of the boat, the other being its mirror image. For small craft such as canoes and kayaks the term beam is often applied to the widest breadth, measured from the outside of one gunwale to the outside of the other.
Brace: [Stütze, die] During a brace the paddle is forced downwards into the water to produce a resulting righting moment on the boat and paddler, in order to counter the boat's roll. We distinguish between a high and a low brace. During the former the power face of the paddle faces downwards, the paddler pulls downwards on it. During the latter, the power face of the blade faces upwards and the paddler pushes downwards on the paddle.
Lines: If we imagine cutting the hull vertically
parallel to the fore and aft line, the resulting cut surfaces are referred
to as buttock lines. In lines drawings of boat designs they are depicted
in the profile view. In practice, lines drawings of folding boats often
substitute the actual lines of the outer edge of the longitudinal frame
members as seen from the side. This facilitates the development of construction
drawings from the lines drawing.
Canoe: [Kanu, das] A canoe usually describes a double ended boat of slender beam and is most often associated with native inland inhabitants of the north American continent. In the German language the term "Kanu" is used to describe the entire group of boats propelled by paddles, the subdivision "Kajak" referring to arctic boats (most often Greenland types and propelled by double bladed paddles) and the subdivision "Kanadier" referring to open boats (most often inland boats propelled by single bladed paddles).
[Kenterung, die] Turning upside down.
[Unterzug, der] A carling, sometimes also written as carlin, is a longitudinal
frame member. It is usually of much heavier construction than a deck stringer
because it is often used where it must withstand considerable bending
forces from the side. Carlings increase the stiffness of the hull and
can double as hip, thigh and knee braces as well. Thus carlings often
run on the inside of the frames, they may even be used to bridge roofless
frames in open cockpit boats.
of Lateral Area: [Zentrum der Seitenfläche,
das] The center of lateral area is the point, which coincides with the
centroid of the area of the boat in profile view. We distinguish between
the submerged center of lateral area, which applies to the area of the
boat below the water line and on which hydraulic forces act and the center
of the lateral area above the water line, on which the wind may act.
[Knick, der] The line of intersection between two longitudinal sections
of the hull. Folding boats inevitably are chine boats since the hull material
stretches from stringer to stringer in a straight line. Of course, the
larger the number of stringers, the closer the hull cross section approaches
a truly round shape.
[Süllrand, der] Rim of the cockpit. This rim is often reinforced by a
frame member and may be underlayed by a carling.
Commercial folding boat builders tend to use materials for the hull and
deck, which are already coated. Amateur builders may sew the skin to fit
their frame and then coat it. Modern builders of traditional skin-on-frame
boats use a variety of substances to make their boats water proof. Some
are more suitable for folding boat construction, some less, the main concern
being sufficient flexibility to withstand repeated folding of the skin
when the boat is disassembled.
Some builders have used the concept of "waxed cotton" with some success, by which (bees) wax is dissolved in various oils and applied to canvas. Traditional sailors' oilskins and some foul weather motorcycle clothing is made in the same way. The advantage of this approach is in the low cost and some possible weight savings, the disadvantage lies in the need to re-proof regularly.
[Cockpit, das] Place in the boat where the paddler sits.
Section: [Querschnitt, der] If we imagine
cutting the hull vertically at right angles to the fore and aft axis,
the resulting cut surfaces are referred to as cross sections. Lines drawings
of boat designs depict the cross sections in the so-called body plan.
It is useful to note that usually the cross-sections forward of the greatest
beam are drawn on one side only of the vertical centerline of the body
plan, while those aft of the greatest beam are drawn on the other. This
means that only one side of each cross-section is actually depicted, the
other half being its exact mirror image, of course.
The part of the stem, which parts the water during forward motion. Some
traditional northern Pacific kayaks display a very distinctive cutwater
as the lower half of a bifid bow.
[Deck, das] The top portion of the boat's skin, usually defined as bordered
by the gunwales.
Fit: Traditional skin-on-frame boats are custom built to the specific personal dimensions of their intended user. The paddler will "wear" such a boat with a tight, body conforming fit. Factory standard commercial folding boats are normally built to one set design. It might therefore prove beneficial if a paddler were to undertake a certain amount of outfitting of the cockpit to achieve an optimal fit, before exploring the full potential of performance of such a boat. Achieving the perfect fit is a highly personal thing and is largely independent of the factory standard configuration of the cockpit. Persons who build their own folding boats are of course able to adjust the basic design to their requirement.
Fitting: [Beschlag, der] Any angle, band, bolt, bracket, clasp, clip, fastener, hinge, nut, peg, tongue, strap, wing nut etc. used to connect frame members. Usually these will be made of metal, hopefully of stainless steel, brass, bronze or copper and thus highly corrosion resistant. Some commercial builders use proprietary fittings, sometimes patented; others have ingeniously adapted off-the-shelf hardware. Amateur builders often make their own fittings from flat and bar stock of the appropriate material and dimensions.
This term has a double use.
A hard chined boat [Knickspanter, der] has only one pair of stringers.
Looking at the cross sections of the boat, the angle that the skin makes
as it passes over the stringer at the chine is "hard".
[Rumpf, der] Can be used to refer to the entire envelope of a boat (excluding
any superstructure) or merely to the portion below the sheer line.
Hypalon is a synthetic rubber used to waterproof a fabric substrate for
The term kayak is derived from usage in arctic languages where it describes
a long narrow hunting boat propelled by single or double paddles. There
are a variety of spellings including kajak, qayaq, qajaq
et al. The term kayak has been most closely associated with boat designs
deriving from indigenous Greenland types. Greenland type kayaks are almost
invariably propelled by a single paddler using a double bladed paddle.
[Kiel, der] The keel is the bottom most line of the profile of a boat.
[Länge, die] We usually differentiate Length Over All (LOA) and
Length at Water Line, or Load Water Line (LWL).
Overhangs: [Überhang, der; Ausladung, die - often followed by "des Stevens"] On most folding boats the stem is raked forward so that the furthest tip of the bow is located further forward than the intersection of the stem with the waterline. The horizontal distance between these two points is the overhang. The same is true for the stern in reverse analogy.
[Paddel, das] Most folding boats are propelled by double bladed paddles,
with each blade being used in alternation. However, as proven by centuries
of practice by arctic peoples, single bladed paddles can be used to good
advantage. Paddles can have short, wide (low aspect ratio) blades, encouraging
a paddling technique, which emphasizes the effects of drag to produce
thrust. Longer, narrower (high aspect ratio) blades tend to be used in
paddling techniques emphasizing lift to produce thrust.
Technique: [Paddeltechnik, die] There
exists a variety of methods of producing thrust with a paddle through
the principles of lift, drag or a combination thereof.
PVC: Poly-Vinyl-Chloride comes in a variety of forms. A soft version can be used to waterproof a fabric substrate for hull material. It also protects the fabric against abrasion and is a first barrier against piercing. PVC hull material is highly abrasion resistant, does not age, is virtually impervious to degradation by such chemicals as may be found as pollutants in water and does not deteriorate under ultra violet radiation. PVC hull skins need no maintenance other than cleaning to remove any accumulated dirt. There is an ongoing debate regarding the pros and cons of the use of PVC as compared to Hypalon.
[Rippe, die] Term used in traditional skin-on-frame kayak building, where
it describes a transverse frame member running from gunwale to gunwale
and supporting the keelson. The term is sometimes applied to the transverse
frame members of folding boats.
Ring Frame: see Frame
[Sprung, der] The rocker is the term applied to the curvature of the keel
line of the boat.
[rollen] Turning of the boat about its longitudinal axis.
Rubber: Natural rubber was traditionally used in the construction of folding boat skins. Despite its relatively high specific weight it was most often used in five-ply construction, consisting of three layers of rubber, interspersed with two layers of fabric. This type of construction continued to provide abrasion resistance even after the outer layers of rubber started to become brittle as they perished, while the more protected central layer of rubber continued to ensure a watertight hull. Its synthetic cousin Hypalon, as well as soft PVC, replaced natural rubber.
[Schäften, das] Joining two lengths of wood. Most usually long mirror
image bevels (at least in the ration of 8:1) are cut into the ends to
be joined. Some builders rely on adhesives, others prefer to add mechanical
fasteners (nails, screws or dowels). Some go as far as to cut hooks into
the scarph faces to provide complete security against longitudinal separation.
Sculling: [Scullen, das] The paddle can be used to move the boat sideways (near vertical position of the paddle) or to support it against rolling (near horizontal position of the paddle) by sweeping its blade back and forth repeatedly edge on. The leading edge is slightly raised during each sweep so that the blade produces lift and thus the desired force.
[Scheer, der] The intersection between the deck and the hull of a boat.
It is considered positive if the ends are higher than the mid-sections
and vice versa.
[Haut, die] Collectively the entire outer envelope of the boat. In traditional
skin-on-frame boat building this envelope was made of walrus or seal skin,
sometimes of caribou hide, and water proofed with animal grease.
[Sente, die] Used to describe any longitudinal frame member not otherwise
exclusively named. "Deck stringer" and "chine stringer" are two possible
examples of uses.
Trim: [Trimm, der] A boat is designed to float on a given waterline in neutral trim. As long as the center of gravity of the load (including the passenger) is directly above the designed center of buoyancy (CB) of the boat, trim will remain neutral. If more weight is added before or abaft the CB, the boat is said to be trimmed by the bow or stern respectively. If more load is added off to one sided of the CB, then the boat will heel in response.
Washboard: [Waschbrett, das] A narrow plank that runs along each side of the edge of the cockpit, connecting the tops of the open roofed frames. To some extent it stops water from washing into the cockpit, serves to hold the deck fabric and reinforces the structure of the frame.
Line: [Wasserlinie, die] The water line is
defined by the interface between air and water along the length of the
boat. On flat calm water it will vary with the trim and the load of the
boat. When the surface of the water is disturbed, the cross sectional
shape of the waves at the surface of the water will also have to be taken
Lines: [Wasserlinie, die] If we imagine cutting
the hull horizontally, the resulting cut surfaces are referred to as water
lines. In the lines drawings of boat designs these are depicted in the
plan view. In practice, lines drawings of folding boats often substitute
the actual lines of the outer edge of the longitudinal frame members as
seen from above. This facilitates the development of construction drawings
from the lines drawing.
Weathercocking: [luvgierig sein] A boat is said to weathercock when it has a tendency to turn into the wind. For this to happen there must be an imbalance between the wind forces acting on the forward and the aft part of the boat sufficient to turn the boat.
[Holz, das] Wooden frames usually use ash for the longitudinal members
for its resilience and flexibility, sometime spruce, where light weight
is more important than strength. Transverse frame members can be made
of a variety of woods or plywood. In the case of the latter commercial
builders favor many layered birch plywood for its strength to weight ratio
and ability to withstand shock loads.
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