Aluminium Tacht Surveys
Hamble Marine Surveys have recently undertaken a Pre-Purchase Survey on a 43ft Aluminium built sailing yacht. Being a specialist survey firm and experienced in Aluminium as a construction material, we were able to assist the prospective purchaser.
The vessel built by a Alubat in France is a well known production model called an Ovni 43. They are well regarded and offer a niche market normally suited to long distance blue water cruising or expedition sailing.
The vessel is surveyed much the same as any 43ft yacht, however the hull and deck need to be inspected very differently taking into consideration the manner in which they are built and problems they may experience.
Aluminium is an alloy and well suited for use as a marine construction material being light, strong and resistant to corrosion. Like any metal problems can exist whether due to poor construction or damage sustained.
Aluminium built vessels normally start with an extensive frame and grid welded together onto which the plates are welded over the frames to create the hull. The deck is constructed in much the same way and eventually the two welded together.
Aluminium is resistant to corrosion primarily due to the production of a protective oxide layer which forms when in contact with air. The presence of a paint coating above the waterline on an Aluminium vessel is purely cosmetic due to the slightly dull appearance of Aluminium due to the above mentioned oxide layer. Regrettably even with suitable pre-coating primers and preparation paint coatings are difficult to achieve a long lasting adhesion to the Aluminium surface. Regular re-coating is necessary.
As with any metal over time, wastage and corrosion can occur especially where stray electrical currents may exist. Cathodic protection on any metal built vessel is critical and the use of suitable compatible metals in fittings to the hull.
Apart from the sounding hammer, another very useful tool for the surveyor is the Ultrasonic Thickness Gauge. Julian Smith of Hamble Marine Surveys is trained in the use of a Cygnus 4 Thickness Gauge which allows the thickness of the hull plating to be accurately determined, and when cross-referenced to the build data the degree of plate wastage or localized corrosion can be determined.
Hull thickness surveys may be a requirement of insurers as well as purchasers.
For more information on Pre-Purchase Surveys whether GRP, Steel, Aluminium or other please contact Julian at Hamble Marine Surveys.