admin October 18, 2025 Sailing Previous Lesson Comments (0)
Photo Courtesy Don McDermott - this is the Tender from building Lady Garnet The first Trading Wherry since 1912
Link to Don's Channel well worth a visit
Thwart Knees: Triangular Braces Connecting the Thwart to the Hull
Definition:
Thwart knees are the triangular wooden or metal supports that connect a thwart (a crosswise seat or beam) to the hull or gunwale of a boat. They provide strength and rigidity, transferring loads from the thwart into the sides of the boat and helping maintain the hull’s shape under stress.
Understanding the Thwart Knees
In small boats such as dinghies and traditional wooden craft, thwarts are used for seating and to stiffen the hull. However, without additional bracing, the junction between the thwart and the hull could flex or even split under pressure. Thwart knees solve this problem by creating a solid triangular connection that distributes the forces acting on the thwart evenly into the boat’s structure.
They are particularly important in clinker-built boats or those with wide beams, where the crew’s weight or rowing loads can place considerable strain on the hull.
Applications in Sailing
Structural Support:
Thwart knees strengthen the joint between the thwart and the hull, preventing flexing or twisting.
Load Distribution:
When a sailor or rower sits on a thwart, the knees help distribute their weight and the resulting stress evenly along the hull.
Hull Integrity:
By reinforcing the hull-to-thwart connection, thwart knees help maintain the boat’s intended shape and stiffness, which is essential for proper handling and safety.
Examples of Usage
"Check the thwart knees for any movement before taking the boat out—loose ones can cause flexing."
"The old clinker dinghy needed new thwart knees after the originals rotted where they met the hull."
"The bronze knees were beautifully made and gave the boat a solid, traditional finish."
Visual Representation
Image Description:
Diagram of a small wooden boat viewed from above and to the side, showing a thwart running across the hull. At each end, a triangular brace (the thwart knee) connects the thwart securely to the gunwale and hull, forming a sturdy right-angle support. The knees are shown either as carved wooden pieces or as metal brackets.
Importance in Sailing
Thwart knees are vital to the overall strength and durability of a boat’s structure. They:
Prevent hull deformation when the boat is under load.
Support the thwarts used for seating or mounting equipment.
Reduce creaking and movement, giving the boat a more solid feel under sail or oar.
Without sound thwart knees, the hull can flex excessively, the thwarts may loosen, and the boat’s stability can be compromised — particularly in rough water or when rowing hard.
Related Terms
Thwart:
A crosswise seat or beam spanning the width of a boat.
Gunwale:
The upper edge of the boat’s side to which the thwart knees are attached.
Hull:
The main body of the boat.
Frame:
The ribs that form the hull’s internal structure.
Stringer:
A longitudinal reinforcing beam that adds strength along the hull.
Conclusion
Thwart knees may be small components, but they play an outsized role in a boat’s strength and longevity. By firmly anchoring the thwarts to the hull, they keep everything rigid, balanced, and seaworthy. Whether crafted from bronze, oak, or aluminium, well-fitted thwart knees are a sign of good workmanship — and a key reason why a boat feels solid beneath you when you take her out on the water.
