Hi! I’m Stefano Pisano, an Italian marine surveyor. Today I will go through the appraisal of a steel boat.
The appraiser called to do an appraisal for a metal alloy boat will obviously have a different approach to the hull than for other materials.
Steel hulls first of all can be of varying workmanship e.g. round hull or edge hull, stucco coated or not and of different construction, there are hulls designed by expert designers and built by shipyards specializing in nautical construction and hulls produced in a handcrafted manner from designs perhaps copied here and there.
This in the approach to appraisal makes a lot of difference since the nautical expert in the case of a hull designed and built by expert hands will have some design material to refer to in order to verify thicknesses and construction conformity.
Vice versa, in the empirical construction spread in the 70s/80s we find many hulls made with unique thicknesses and construction techniques that ignored some iron defects such as water stagnation in the bilges or coupling between different ferrous materials.
Personally, when I survey a steel hull, I use a few simple tools including a peg or “male e peggio” in Italian – I use the peg to blow off any rust buildup and check the good iron underneath, then an iron brush for the simplest parts, an ultrasonic thickness gauge of extreme precision to find the thicknesses of the sheet metal and match them with the construction plans or with other areas of the hull intact.
It is essential not to leave any portion of the hull unexplored internally because it is there, in the intersections between longitudinal and transverse beams that water can stagnate and create rust, which if in the case of the deck can lead to easily detectable waterways from above, from below can lead to the worst.
Another sore point of steel hulls is often the ballast i.e., the material placed in the fin to counterbalance the wind thrust on the sails; There are steel hulls with lead ballast, cast iron, concrete, sand, all then perhaps coated in resin.
In short you can find everything but, since the fin is often the lowest part of the hull or the actual bilge of the boat, there is a risk that there the accumulation of all the water coming from inside will occur so it will be necessary to carefully inspect the state of the material and avert the possibility that there are unexplored gaps where water can nest.
It’s also important for the marine surveyor to be able to assess how the sacrificial anodes are installed and how well they function.