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Glossary of Terminology found in and around Folding Skin-on-Frame Boats

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1. This glossary continues to grow. Use Ctrl+F to activate your browser's on-screen search function for this page. The entire glossary so far compiled is contained on this page; therefore if you do not find a particular term, please send us an email at so that we may add it. Thank you!

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.


Baidarka: 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.
See also: Kayak

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.

Buttock 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.
See also: Cross Section, Water Lines

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).

Capsize: [Kenterung, die] Turning upside down.
See also: Roll

Carling: [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.
See also: Frame, Stringer

Center of Buoyancy: [Auftriebszentrum, das] The center of buoyancy is the point that coincides with the centroid of the volume of water displaced by the boat.

Center 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.
See also: Weathercocking

Center of Mass: [Massezentrum, das] The center of mass is the point which coincides with the centroid of all the things aboard the boat, including the boat itself, weighted by their mass.

Chine Log: The stringer at the chine. This term is rarely used in folding boat construction and then only in hard-chined boats in analogy to its use in wooden boat construction.

Chine: [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.
See also: Hard-Chined

Coaming: [Süllrand, der] Rim of the cockpit. This rim is often reinforced by a frame member and may be underlayed by a carling.
See also: Washboard

Coating: 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.
Examples of coatings (which can be obtained in liquid form) are Neoprene, Hypalon, various polyurethanes etc.

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: [Cockpit, das] Place in the boat where the paddler sits.
See also: Coaming

Cross Frame: see Frame

Cross Rib: see Frame

Cross 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.
See also: Buttock
Lines, Water Lines

Cutwater: 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.
See also: Baidarka, Kayak

Deck Beam: [Deckbalken, der] In traditional Kayak construction the deck beams are transverse frame members, which spread the gunwales.
See also: Frame, Rib

Deck: [Deck, das] The top portion of the boat's skin, usually defined as bordered by the gunwales.
The deck of folding boats was traditionally made of untreated or proofed canvas to ensure light weight (at least when dry!) and "breathability". Canvas fibers swell as they absorb water, thereby effectively closing the gaps between the fibers in the weave and rendering the deck watertight. Points of wear are usually reinforced with additional layers of deck material or even with hull material.
Advances in material development have brought about the use of synthetic fibers like nylon and polyester, which need to be waterproofed before they can be used however. Lightweight PVC impregnated fabrics also see use as deck material.
See also: Hull, Coating

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.

Frame: This term has a double use.
1 - On the one hand it refers to the entire skeleton of the boat [Gerüst, das; Gestell, das].
2 - On the other it refers to the individual transverse members of the frame in loose analogy to the term's use in traditional occidental boat building [Spant].
Folding boat frames are usually executed as ring frames, i.e., as one continuous unit consisting of sides, bottom and roof (combining the functions of frames, floors and deck beams in wooden boat construction). Some folding boats, especially double and triple seaters, may have long open cockpits. In this case the frames in way of the cockpit are sometimes executed as so-called U- or C-frames, i.e., they lack the roof.
Frames were traditionally made of wood and corrosion resistant metal fittings, but nowadays incorporate a variety of materials, including aluminium and several types of plastics.
See also: Carling, Cross-Frame, Cross-Rib, Rib,

Gunwale: [Bordwand, die; Bordleiste, die] In folding boat terminology the gunwale is the longitudinal frame member, which coincides with the sheer line of the boat.

Hard-Chined: 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".
See also: Chine Log

Heave: [Hub, der] Vertical component of motion of the boat; also as a verb meaning "to pull".

Heel: [Krängung, die] Turning motion about the longitudinal axis of the boat.

Hog: [Sprung, der] The term hog refers to negative rocker in American terminology, but to the keelson in British terminology.

Hull: [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.
Hull materials are usually of multi-layered construction (traditionally five-ply, nowadays more usually three-ply) consisting of outer layers of a waterproof substance on a fabric substrate. The fabric substrate may either be flexible (of advantage when the hull material needs to conform to complicated hull shapes) or inflexible (of advantage when the hull is built very accurately from a number of panels).
See also: PVC, Hypalon, Rubber, Coating

Hypalon: Hypalon is a synthetic rubber used to waterproof a fabric substrate for hull material.
It was developed for this use to overcome the problems associated with perishing of hull skins waterproofed with natural rubbers. The manufacturers of Hypalon skins recommend regular treatment with various compounds to combat degradation resulting from exposure to ultra violet radiation. Hypalon is softer and more pliable than PVC, especially at low temperatures. It is abrasion resistant and acts as a tough first barrier against piercing. There is an ongoing debate regarding the pros and cons of the use of Hypalon as compared to PVC.

Kayak: 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.
See also: Baidarka

Keel: [Kiel, der] The keel is the bottom most line of the profile of a boat.
It runs into the stem and the stern. In Greenland style boats there is often a very distinct hard angled transition between the keel and the stem and stern, in other designs the line of the keel may run fluidly into the latter two.

Keelson: The keelson is the internal frame member at the bottom of the hull, which defines the line of the keel. Folding boats can have single or double keelsons.
See also: Keel, Scarphing

Length: [Länge, die] We usually differentiate Length Over All (LOA) and Length at Water Line, or Load Water Line (LWL).
The numerical difference between LOA and LWL equals the sum of bow and stern overhangs. A particular boat will be designed for a certain load and the length of the actual loaded waterline will differ from the designed water line in proportion to the overhang at stem and stern, as well as to the fullness of the overhangs' belly in profile.
See also: Water Line

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.

Paddle: [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.
See also: Baidarka, Canoe, Kayak, Paddling Technique

Paddling 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.
Longer paddles require greater force, a long stroke and a slower cadence to fulfill their potential for efficiency. Shorter paddles encourage a faster cadence, a shorter stroke and thus allow an efficient energy transfer with less force. There is an ongoing debate as to the respective merits of various styles and techniques. Persons new to the sport, as well as old hands do well to approach this issue with an open mind and to experiment for pure enjoyment!
See also: Paddle

Pitch: [Stampfen, das] Turning motion of the boat about a horizontal axis at right angles to the longitudinal axis.

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.

Rib: [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.
See also: Deck Beam, Frame

Ring Frame: see Frame

Rocker: [Sprung, der] The rocker is the term applied to the curvature of the keel line of the boat.
See also: Hog

Roll: [rollen] Turning of the boat about its longitudinal axis.
Rolling can be induced by wind or wave action, or by deliverate action on the part of the paddler. In the latter case the term can be used to refer to a technique for recovery from capsize. Edi Hans Pawlata introduced the roll to European paddlers in 1927, after intensively studying paddlers in Greenland. His technique is called the Pawlata roll to this day, although it was referred to as the "Eskimo Roll" shortly after its introduction and for decades thereafter. There is a great variety of rolling techniques with and without paddles or other aids.

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.

Scarphing: [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.
See also: Keelson, Stringer

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.

Sheer: [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.
See also: Gunwale

Skin: [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.
See also: Deck, Hull

Stem: [Steven, der] The frame member, which defines the shape of the bow.
NB: the German term can refer to the bow [Vordersteven, der] or the stern [Achtersteven, der].

Stringer: [Sente, die] Used to describe any longitudinal frame member not otherwise exclusively named. "Deck stringer" and "chine stringer" are two possible examples of uses.
See also: Scarphing

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.

Water 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 into account.
See also: Length, Trim

Water 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.
See also: Buttock Lines, Cross Section

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.

Wood: [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.
See also: Frame

Yaw: [Gieren, das] Turning motion about the vertical axis of the boat.


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