Today, after fettling the Big Top we began assessing a repair strategy for the deck of the monkey island which has been leaking rainwater, damaging the internal fabric of the ship.
We began by developing a method of removing the planking without damaging the aluminium structure. Some of the wood is rotten and crumbles but in fact the sound wood is looking like it will be easy to remove. Firstly we removed the nuts on the retaining studs, these are aluminium and not overly robust. Most screwed off, but the occasional one sheared. We then ran a buzzsaw down the caulking line and then across the plank at suitable intervals and prised the planks off. This seems to work well and we are confident that we can quickly strip the deck without further damage.
What did we find? Well so far it is quite encouraging. In the area stripped in the above photo we found two or three perforations of various sizes and a fair bit of pitting which would eventually perforate.
The white material in the photo above is aluminium oxide, or corroded aluminium if you like. On a positive note the orange areas are the original coating and these areas are original thickness alloy.
The likely plan for repairing then is initially to remove all the wooden decking. After that we can survey the deck and assess the damage. We will then have to mechanically remove the corrosion with wire brushes etc. We will probably prime and plate over the perforations and severe pitting with aluminium plate and Sikoflex sealant to keep it watertight. We will then prime the entire deck with a suitable aluminium primer. Zinc chromate appears to be no longer fashionable as it contains carcinogens. A coat of protective paint will follow. Further down the road of course we hope to replace the wooden deck. This is particularly desirable as the surrounding aluminium angle that retains the wood will act as a cofferdam and prevent rainwater from draining. It is encouraging that most of the deck in this section is sound and we hope that this will continue to be the case. Watch this space for future developments.