Thread: Heron deck replacement

The Heron is one of the legacy classes from the great growth of dinghy sailing after World War 2. Naturally, it was originally built in plywood. The class's original name was the Yachting World Car Top Dinghy, Heron is simpler, and this one is the Australian variation.

The class is often built completely in FRP today, and a new glass boat could easily set you back $10,000. Some are still built in wood, but many in the current fleet come from the transitional period when the low maintenance of a glass hull was matched to the stiffness of a wooden deck. Such was the case with my friend's boat. Significantly, the gunwales and inwales are Western Red Cedar, so changing the deck is exactly the same task as it would be with a wooden boat.

The old deck looked beautiful, until you realised that the mast step moved several mm under load and was in imminent danger of failure. It had been secured with only two screws, one of which was well forward of the king post. As a result, the king plank had broken. Surgery was required.

Dismantling the deck introduced a whole list of defects:

1. King plank fractured, with soft blackened timber at the break.
2. King post with numerous unfilled holes from previous fittings, wood soft where varnish not applied to hidden (forward) surface.
3. Deck beams at stations 1(B) and 2 (front of cockpit) broken from inwale on port side and floating. In addition, deck beam 2 was not attached to the king post.
4. Fibreglass bonds on all port side knees (supporting the side decks) and one starboard knee had failed. This was probably due to "enthusiastic" assistance by several people to lift the boat up from the beach.
5. Much of the timber structure under the deck showed no evidence of waterproof treatment. Water had penetrated the inwale near the chainplate fittings and there was a significant amount of rot.
6. Removing the inwale rot showed that at some stage, damage had occurred to the top of the starboard moulding. New three hole chainplates had been bolted through the hull and a pad of plywood. This strengthening pad appeared to provide the principal strength for the shrouds but the glue joints to the moulding had failed and the support was achieved by the mechanical abutment of these 6mm plywood pads against the rotting inwales.
7. Close inspection of the starboard gunwale disclosed water penetration where the chainplate passes through the gunwale and probable further rot.

Fortunately, the season does not resume until 1 September! Sounds like an interesting project and one which, with variations, many readers of the forum might identify with. Some of you are far more knowledgeable than me and input would be greatly appreciated.

Finally, the owner wants his new deck to accommodate narrower sheeting angles, so it is not a case of replacing the old deck with one of the exact same dimensions.

Some photos: