Strake

A Strake is

1. part of a boat or ship. It is a strip of planking in a wooden vessel or of plating in a metal one, running longitudinally along the vessel's side, bilge or bottom.
2. a device for controlling aerodynamic flow over an aircraft.
3. a tool for tamping down and levelling semi-fluid materials into a mould.

1. Boatbuilding

A Strake is part of a boat or ship. It is a strip of planking in a wooden vessel or of plating in a metal one, running longitudinally along the vessel's side, bilge or bottom. That adjacent to the keel is the garboard strake and that at the top of the side is the sheer strake. A rubbing strake was built in just below a carvel sheer strake. It was much less broad but thicker than other strakes so that it projected and took any rubbing against piers or other boats when the boat was in use. In clinker boats, the rubbing strake was applied to the outside of the sheer strake. Others have no special name other than bottom strakes, bilge strakes and topside strakes. Where the transverse sections of the vessel's shape are fuller, the strakes are wider. They taper towards the ends. In many bigger vessels, two would there be converted to one. This one is known as a stealer or stealer strake. It is one of these which was also shaped to fit the concave line of the hull, under the counter at the sternpost. That had to be shaped by carving from an especially thick plank of wood known as a short strake or plank. When someone was looking for the epitome of thickness he thought of the metaphor, thick as two short planks.

Except in very small boats, strakes are made of more than one piece of wood or metal scarfed or butted together. In metal vessels, the modern practice is to butt-weld them.

Wooden planks can be scarfed into a strake by suitably tapering the thickness of the adjoining ends. Traditionally, the adjoining faces were coated with mixed white lead and grease then they were held together with copper rivets. It was important not to have the plank end as thin as a feather edge and to have the outboard thin edge at the after end of the joint. In later times, after adhesives had been developed by the aircraft industry, the joint might be made with resin glue and no rivets. In heavier carvel work, the joint would be a butt riveted to a butt strap. Even large clinker vessels had scarfed strakes.

In a riveted steel ship, the strakes were usually lapped and joggled but where a smoother finish was sought, they too might be riveted on a butt strap.

Maritime Construction Traditions

There are two sorts of wooden strake; carvel and clinker. In the former form of construction, one more traditional in the Mediterranean than in north Europe, the adjoining strakes butt onto each other. The resulting finish is relatively smooth but needs caulking to make it watertight and it is relatively heavy. Carvel boats are planked up onto pre-erected frames which become part of the boat.

The second method is clinker. It is traditional in the north and produced relatively light but strong boats. Normally, the boats are built from the garboard up so that the upper strake overlaps the lower on the outside. That overlap is known as the land and it is held together by copper rivets. In the twentieth century, the boat may have been built of plywood and the strakes glued together without clenched nails. Medieval boats are more likely to have been riveted with iron nails. To rivet the lands, the two strakes are pierced, a nail inserted from the outside and a rove or rove punched over the inside end of the nail. The latter is then cut off a little proud of the rove. The nail is then clenched over the rove while the nail is held up by a dolly, a small portable anvil.

When the shell of the boat is complete, the strakes are tied together by inserted steam-bent timbers. These too, are riveted to the planking through the lands. The timbers, which are sometimes miscalled ribs, spread the load on the strakes and tie them together so reducing the tendency of the strake to split. With glued ply clinker construction, the timbers are unnecessary.

At the ends of the strakes, the lands are faired into each other with geralds. in these, the lower strake is tapered in the land, to a feather edge at the end of the land where it is supported by the apron. The planking then meets the stem, flush.

Steel ships may be plated as clinker-built vessels but more usually, they are built with strakes alternately in and out. The modern method is to butt-weld the strakes to each other as well as end to end. This leaves a smoother finish and is lighter.

2. Aircraft

In aviation, a strake is an aerodynamic surface generally mounted on the fuselage of an aircraft to control airflow. The strake produces vortices by interacting with the airstream. Aircraft designers change the location, angle and shape of the strake to produce the desired interaction. The strake is commonly confused with a canard or a winglet.

The X-31 features forward canards and aft fuselage strakes

The aircraft industry expanded very rapidly at the time of World War I. The skills required both in woodwork and in designing were similar to those of boatbuilding. The aircraft firms like Sopwith, eagerly sought boat builders, especially those accustomed to work with such as rowing club best boats, Thames A class raters and the pre-war racing power boats. At that time, a good deal of boatbuilding thinking and terminology transferred with the men. It is therefore not surprising to find a longitudinal plate resembling a rubbing strake, though with a different purpose, being called a strake. Aircraft with strakes:

• A-10 Warthog: Two just ahead of the wing, on the lower portion of the fuselage
• F-14 Tomcat: Beneath each engine.
• Rockwell-MBB X-31: On either side of the aft fuselage
• McDonnel Douglas MD80: On either side of the forward fuselage
• Concorde: On either side of the forward fuselage

3. Straightedge

The word Strake also refers to a straightedge used for levelling a bed of sand, or striking poured concrete or plaster level with the edges of the formwork or mould into which it has been poured.