Thwart

A thwart is a part of an undecked boat that provides seats for the crew and structural rigidity for the hull.

A thwart is a part of a boat that usually has two functions: as a seat, and as a structural member that provides some rigidity to the hull.

Firstly, with a rearward facing oarsman,[a] the thwart has to be nearer the front of the boat than the pivot point for the oar (which acts as a fulcrum).

The oarsman has to be positioned so that during the recovery part of the stroke, the oar is above the surface of the water, allowing for the height of waves which the boat might encounter.

Since the oarsman is seated, the inner end of the oar cannot go any lower than the top of their thighs – and some clearance is needed for comfort.

This usually translates into the top of the thwart needing to be 10–12 inches (250–300 mm) below the point on the gunwale where the oar is pivoted.

As the power of the stroke is delivered, the force applied by the oarsman is reversed in direction by the fulcrum of the oar pivot.

In a traditional wooden construction it usually sits upon, and is fastened to, a longitudinal stringer which is sometimes called a shelf.

[5] In a canoe, a thwart is simply a strut placed crosswise (left/right) in a ship or boat, serving only as a structural member or to help with carrying.

The thwarts in this wooden dinghy are the three seats that go from one side of the hull to the other. The U-shaped arrangement of seats at the stern of the boat are the sternsheets
A Cornish pilot gig , a single banked boat
Clinker built dinghy showing some of the basic structural details. The single rowing thwart supports the aft end of the centre-board case. The pairs of knees at each end of the thwart can be seen; also the longitudinal stringer on which the thwart rests. A mast thwart, nearer the bows, is set at a higher level and has a hole through which the mast is placed,
Drawing of a canoe showing thwarts. The centre thwart, shaped like a yoke , serves as a carrying pole .