Dick Bellchambers writes:- Now that the welding of the new wrapper plates on the fire box is complete [Dec 05] we are starting to make progress with the other fixings. The picture shows the use of patch screws. The two top ones go into the corner of the foundation ring. Because of the tight corner the geometry does not allow for the use of rivets. The other three in a vertical line are in place of rivets and are required to fix side plate to the back plate. Originally rivets would have been used but because the inner firebox is still in place it is not possible to get at the other face of the outer firebox to enable a rivet to be formed. The hexagon heads are used to tighten the screws and are then removed (this has been done on the bottom one in the picture). The heads are then tooled to form a watertight seal.
Credit: Dick Bellchambers, 9 December 2005