Lamma IV seats fixed to plastic foam

The seats on the upper deck of the Lamma IV ferry carrying the 39 passengers who died in the National Day ferry disaster were not securely fastened, the commission of inquiry into the disaster heard yesterday.

The flooring on the deck was made up of three layers of fibreglass - a 25mm-thick core of plastic foam sandwiched between two layers of woven roving, each 2.1mm thick - according to an expert report.

Each seat support was secured with two 25mm-long screws, but 20.9mm of each screw was embedded in the foam core, the commission heard.

"Only the woven roving makes a structural connection with the screws, the plastic foam having no strength to resist 'pull out'," commission-appointed naval architect Dr Anthony Armstrong said in his report.

The Lamma IV collided with the Sea Smooth on October 1, killing 39. Most of the upper deck seats became detached, trapping some passengers, it was heard earlier. Armstrong's report said seats on the main deck did not come loose because they were secured to an aluminium structure.

The report cited an engineering rule of thumb: woven roving - fibreglass fabric made by loosely weaving large strands of fibre - should secure about 21/2 screw threads, or be at least 5mm thick in this case - in order for seats to be fastened firmly. With the current thickness, not even one full screw thread could be secured.