Seam construction

This page discusses seams as a construction detail. For other uses of the term see Seam (disambiguation page).

[edit] Strip built

Strip built construction sometimes refers to the hull line near the sheer line where the deck and the hull are joined. Applying a piece of fiberglass to this joint on the inside of a strip built boat is often difficult for a builder.

http://www.qsl.net/ws8g/kayimage039shearstrip.jpg

Several hints are often mentioned about this task:

• The builder may want to use a drop of hot glue every foot or so to tack the inside tape down to the hull or the deck before joining the halves. This keeps the tape in place so that epoxy can be spread on a stable piece of tape.
  • It has been noted that the tape seems to stretch as it gets wet, so there can be a tendency for the tape to bunch up at each drop of glue.
    • This can be partly avoided by glueing the tape with dots while the tape is under just a little stretch.
• On the exterior tape, many have had difficulty sanding the sewn edge of the tape.
  • One solution is to use strips of cloth cut at 45° to the threads. i.e. across the bias
  • This leaves the edges of the cloth without a seam and cutting across the bias
    • decreases the tendency of the threads to come loose in the wetting process and
    • is easier to fit around the complex curves at the edge of the deck

[edit] Composite Construction

In composite construction, there are many ways to create a seam.

Plastic extrusion

A plastic extrusion techique is used to make a plastic component to form a seam. Many of these extrusions are H-shaped. The H is filled with a seam sealer or adhesive and the deck and hull are placed inside. See illustration, below. On the inside of the kayak, fiberglass tape is used to provide a strong reinforcement for the seam (as in Strip Built, above).

Fiberglass tape

Some kayaks have the deck and hull connected with fiberglass tape on both the inside and the outside. The inside tape is usually wide and the outside can be decorative as well as functional. Boreal Designs uses such a decorative seam tape on many of their kayaks.

Gelcoat and fiberglass tape

Some kayaks come with a fiberglass tape on the inside (see Strip built, above) and a layer of contrasting gelcoat on the outside. This method is simple and cheap, but not as strong as a doubly taped seam.