Saturday, 27 September 2014

LIGHTSHIP CORMORANT / LADY DIXON - Chapter 58



Holidays over, it is time to get serious about the deck. I did some experiments (on the garage floor) with plywood and 4x4 timbers. To avoid excess movement/bounce/sag, the plywood covering has to be of reasonable thickness and well supported. Less of one means more of the other and somewhere in the equation will be the minimum cost point!  But let’s be practical.
    Our first plan was to use short lengths of scaffolding plank jammed between the deckhouse and the first part of the gunwale at intervals of 4ft (Photo). That is supposed to represent bitumen between the planks, not water! The insulation would fit between the planks and the whole lot covered with plywood from deckhouse to the main part of the gunwale. The plywood would be supported by and fixed to the planks and to the gunwale.  

     However, my experiments showed that on the deckhouse side, supported every 4ft, there would be definite sag unless the plywood was quite substantial (expensive). This would crush the insulation boards beneath and allow bounce. The other problem with the plank idea was that they would have to be doubled up to provide the 4 inch height needed to match the gunwale step. It would also degrade the insulation every 4ft for 9 inches, albeit slightly. (Photo)

    The second thought was to run a 4x4 along the side of the deckhouse and use that to support the plywood throughout its run along the sides (Photo). The unsupported distance would be across the width and be only about 20 inches. There would be little or no sag and no break in the insulation.

    The other practical point concerns the problem of rain interrupting the process. The ship (deck) is slightly banana-shaped so that water gathers amidships and drains through the holes you can see in the photos. If we have the side decks raised with timber and insulation and it rains, there will be large puddles at the bow and stern, which will have to be drained somehow before we can begin in those areas. So we will do them first. The stern is fairly straightforward and a simple grid of 4x4 will be fashioned to support the plywood. The bow is more complicated due to the companionway and the hawspipes (nostrils). Necessity is the mother of invention! (Photo)

    The numbers indicate how many 2.1m x 1.2m insulation panels are going to be needed (roughly!). There will be off-cuts aplenty to fill in the awkward bits.
David.