Glossary of Boatbuilding Terms

This is a work in progress and will be updated from time to time.

Apex: The inside corner of the Rabbet.

Backing Out: Scooping out wood from the inside of a plank to give it a little hollow. This allows the plank to sit tight up against a curved frame. The degree of backing out changes along the plank’s length as the curve of the frames it rests on changes.

Batten: A long, thin strip of wood used to create a fair curve.

Bearding Line: The line formed by the inboard edge of the Rabbet.

Binder Plank: The plank just below the sheer in a combination lapstrake / carvel planked boat such as a Whitehall. The binder attaches to the sheer via lapstrake planking, but butts up to the plank below it via carvel planking.

Broads: The planks next to the garboard.

Bung: a wooden plug that goes into a bung hole to seal up a screw and protect it from water infiltration.

Bung Hole: The countersink above a screw head that allows a screw to seat below the surface of the wood. After the screw is sunk, a bung is driven into the hole to seal it.

Buttocks: Slices of a boat made lengthwise, and top to bottom. Like slicing a banana the long way for a banana split. The buttock lines help to describe how the boat shape changes from center to edge.

Carlin: A longitudinal deck framing member (i.e., one that runs fore and aft).

Carvel Planking: Planking where the boards butt against each other edge to edge. The seam between the planks is sealed with caulking (cotton or oakum) and putty.

Ceiling: The floorboards that rise up along the inside edge of a boat. They really are more like sloped floorboards or walls, but hey, this is boat talk.

Chain Plate: A metal strap (sometimes a metal sheet) that spreads the load from the rigging out along a wide surface. Rigging puts a huge amount of strain on a boat, and these parts help to distribute the load so that no single fastener has to carry it all.

Construction Drawing: A drawing of the boat showing details one will need to actually build a boat, such as how the stem attaches to the keel, location and number of frames, etc.

Deadwood: Wood that serves primarily as filler between other structural members. A common place to find deadwood is between the keel and the upper keel or rabbet.

Despiling: The process of copying the information off of your spiling batten onto a plank.

Double Planked Hull: A hull that is made up of two layers of planking. Usually the inner layer is a softer, lighter wood such as cedar. The outer planking is often mahogany. Builder often put a coat of thickened shellac between the plank layers, which acts as a sealer. The plank seams are staggered so that the inner and outer seams don’t line up. The outer planking is usually not caulked, so the seams must be made very precisely. This type of hull is light and quite strong.

Drift:  Essentially a long rod that is used much like a giant nail.  Often a drift will be used to hold boards that are edge glued together so that they stay fastened and aligned even if the glue fails.  Sometimes they are used to pin parts down that can’t easily be fastened with bolts.  One such place might be fastening floors to the sternpost of a boat, where through bolting would lead to bolts heads going through thin or tapered sections of wood.  In these cases, a pilot hole is drilled and the drift is roughed up blows from a cold chisel to make sure that it has lots of holding power in the wood.

Edge Set: The process of using force to push the edge of a plank up against it’s neighbor so that their edges mate. It’s the difference between forcing jigsaw pieces to fit into each other using muscle and sliding well-fitting peices together. The problem with too much edge setting is that the opposite edge of your plank will become wavey where it was pushed to make the other side fit into the mating plank.

Fair: Oh don’t even bother asking me to explain this. It means “good looking.” Sometimes it’s curved, sometimes not, but it’s one of those things that after you see it you realize you always knew it.

Feather: – A thin spline put into a wide caulking bevel to close it up prior to caulking.
- A smooth transition from one thing to another, e.g., a feathered edge.

Frame: A structural member that goes from side to side in a boat and supports the planks (and other structures too). They curve up from the keel to the sheer.

Garboard: The plank next to the keel.

Graving Piece: A piece of wood that is “let in” to a board in order to patch it. Usually once carves or routs a slope or constant-radius curve into the damaged section of board, and then glues in a matching patch of the same species of wood.

Hood End: The end of a plank that butts up against the stem of the boat.

Hounds: Wooden protrusions glued to the mast. The forestay, sidestays & other rigging rest on these wooden parts. On many boats, the hounds are made of metal and the rigging attaches directly to them. When the hounds are made of wood, they form a small shelf that keeps the loop of rigging from sliding down the mast.

Keel: The center part of a boat’s spine. Usually solid wood, it runs down the middle of the bottom of the boat.

Keel Batten: A board that goes on top of the keel along its length. It joins the Keel at the Apex of the Rabbet. The Keel Batten makes construction easier by splitting the rabbet in half, allowing the builder to cut each part of the rabbet on a table saw or with a hand plane, rather than laboriously carving out a groove in a solid keel.

Kerfing: A means of making a joint tight by sawing lightly at the juncture of the 2 parts. The saw blade takes off the high spots in the joint, and when it’s removed, you should be able to slide the 2 parts perfectly flush to each other. The name comes from the saw kerf, or width of the cut made by the saw.

Knee: A curved piece of wood or metal used to support and brace where 2 parts of a boat join together. There are many kinds of knees and they are named according to their use. A Quarter Knee attaches the transom to the sides of the boat. A Hanging Knee holds the roof of the cabin down to the rest of the boat. Often knees are used to stiffen the joint where a Thwart or Seat attaches to the side of the boat.

Lapstrake Planking: Planking where the boards overlap each other as they go down the hull from top to bottom. The seams are made watertight by the fasteners pulling the planks together, and particularly by the accuracy of the plank-to-plank fit.

Limber Holes: Holes in framing members that allow water to collect in the lowest part of the bilge. Without limber holes, water would be trapped in the little bilge spaces between frames or floors and just sit there. Removing the water from the boat would then require siphoning or bailing out between each frame. The limber holes allow water to freely flow down to the lowest point in the boat where it can be collected in one place.

Lines Plan: A drawing of a boat showing the curves of the hull as represented by Waterlines, Buttocks, Diagonals, and profile views of the boat. The three profiles are the Plan View (looking down on the boat), Body Plan (looking at the boat from the front), and the Profile (looking at the boat from the side).

Margin: The floorboard(s) that transition from the Sole to the Ceiling boards.

Mast Partner: Part of the deck and forms the upper support for the mast. The partner works with the lower support, the Mast Step, to hold the mast vertically.

Mast Step: The lowest support for the mast. A tenon projecting from the base of the mast sits in a mortise in the mast step.

Nibbed Scarf: A scarf joint that has a small return at the ends instead of tapering to a feather edge. This allows you to put a fastener in the end of the scarf.

Plan View: A drawing of the boat from the top down. Usually only one half of the boat is shown (or one side showing the boat from the top and the other from the bottom). In this view, lines are drawn much like contour lines to show how the boat curves from bottom to top.

Plank: A board that makes up the outside hull of a boat. Planks are named depending on their location (garboards, broads, sheers) or order of installation (i.e., the Whisky Plank, also called the Shutter Plank is the plank that finishes off the planking of a boat).

Rabbet: A groove cut in the keel and stem of the boat. Planks butt up into the rabbet. The rabbet is cut so that the planks fit as perfectly as possible in order to keep water out.

Ribband: A long piece of wood that stretches from the front to the back of the boat, usually temporarily added to the boat during building to help the hull keep its shape.

Riser: A long strip of wood attached to the frames on the inside of the boat that forms a shelf to support the Seats, Thwarts, and Sheets.

Rove: A special type of copper washer that fits over the end of a copper nail when riveting. The nail is clipped close to the rove, and then peened over to lock the rove onto the nail, essentially making the nail a 2-headed nail with the attached planking in between.

Rub rail: A strip of wood along the top outside edge of the sheer plank. Often covered by rope, rubber, or something else tough to keep your boat from getting banged up as it bumps up against pilings and other things.

Running Backstay: A part of the rigging that holds up the mast from the rear of the boat.  Running backstays are installed in pairs, one on either side of the boat.  A simple backstay is a singe line of rigging that attaches above the transom, and leads down from the top of the mast.  The boom of a boat with this type of backstay has to be short enough to swing from side to side inside the backstay.  In other words, it has to be shorter than the distance between the mast and transom.  With running backstays, the boom can overhang the transom.  When the boom swings to leward (the downwind side), the running backstays on that side of the boat are loosened and the backstays on the upwind side are tightened.

Scarf: A long, tapered joint used to connect 2 boards together while retaining much of the strength of a solid board.

Sheer: The top plank on the boat.

Sheer Clamp: A long board that runs along the inside of the boat along the sheer line. The Sheer attaches to the outside face of the frames and the Sheer Clamp attaches to the inside face of the frames. Also called the Inwale.

Sheet: a) a line that controls a sail (e.g., the main sheet or jib sheet), b) the seat at the aft end of a dinghy.

Sole: The floorboard(s) of a boat closest to the center of the boat.

Spiling: The process of copying the shape of a plank very exactly to a thin batten so that you can make a new plank of the proper shape.

Spine: The core structural members of the boat, consisting primarily of the Stem, Keel, and Transom. Some boats have more parts, but that’s all you need to know for a Beetle Cat.

Stem: The front part of the boat’s spine. It’s the solid, usually curved piece of wood that the planks merge into at the front of the boat.

Stern Post: A wooden piece that supports the Transom and attaches it to the Keel.

Stringer: A long wooden member that goes fore and aft along the frames of a boat. It serves to stiffen the frame. Stringers may be named for their location (e.g., the Bilge Stringer is near the turn of the bilge).

Strongback: 1) a stiff, solid support used to attach molds to when building a boat. The strongback keeps all your molds in line and solid. 2) a Beetle Cat boat part that connects the aft end of the yoke to the centerboard trunk. Along the way, it provides a support for the deck beams that pass over it.

Swallowtail: A metal support that acts like a chain plate. It is used to spread the load of a piece of deck hardware down from the deck to the frames and other structural members of the boat.

Thwart: A cross-member in a boat that helps hold the hull’s shape. Usually a thwart doubles as a seat in smaller boats. Normal people call it a seat.

Tight Seamed Planking: Planking that relies on the tightness of the plank-to-plank fit, rather than caulking, to keep the water out. Doing this takes much patience and skill.

Transom: The rear part of the boat’s spine. It’s usually a flat surface that the planks join to at the rear of the boat.

Whiskey Plank (aka Shutter Plank): The last plank put on the boat, and cause for celebration.