Dezincification

Dezincification can be recognized by the metal colour, shine and texture. In the image below, for example, the section of a bronze propeller blade with distinctly dezincified areas, recognizable by their pinkish colour, can be noticed. Black areas are rests of antifouling paint. White residues are housings of tubular worms and barnacles.

Dezincification can be limited to the surface or may well extend into the metal body.

The marks on one of the dezincified areas on this prop blade have been inflicted by the surveyor’s pocket knife tip. Blows by the pocket knife in the sound areas, in contrast,  have left no marks whatsoever! Dezincification compromises the bronze metal’s mechanical properties significantly and will lead to failure of submerged metals and, if left undetected, to heavy, subsequent damages. Usually, dezincification will slowly develop over time, but this is not a firm rule: A short circuit somewhere on board may lead to a quick failure of one fitting over short time, say few days.

For example, a short in a recently replaced deck light on one spreader may lead to power the mast, which, over the forestay may put the bowsprit’s waterstay under voltage. As a result the waterstay fitting starts to dezincify. This example is a real case and it required a lot of effort and wit to narrow down and eventually find the shortened deck light.

If one dezincified metal appurtenance is identified in the submerged hull, one should inspect the vessel for further damages, including damages to metal bonding and undesired galvanic shorts to one or the other metal fitting. A galvanic corrosion survey with a reference electrode may be required.

The author of these lines distinctly remembers the failed skin fitting on his own boat, which he plugged with his finger until somebody around heard him shouting for help….

Fair winds.

The Shackle Revisited

During our yacht surveys we rarely see shackles that have been moused. We remark that regularly in our reports, but I am not sure whether our clients all appreciate the importance of this.

Mousing is a simple and good practice to secure the bolt of a shackle to prevent it from getting unscrewed unintentionally. I was reminded of this in a marina in Croatia where the pontoons had been shackled to the quay and all shackles had been moused.

Galvanized shackles tend to unscrew when they are under a pulsating load. Even if you tighten them carefully they eventually get unscrewed because the micro-stalactites of the zinc coating eventually get faired under the strain. Stainless steel shackles are also prone to unscrewing as the bolt’s thread usually is seated and rather slippery in comparison to galvanized hardware.

Using rope or galvanized wire is good for mousing, monel wire is even better, but even a cable tie will do as long as it is inspected regularly.

And by the way, the safe working load of shackles is determined by the diameter of the thread root, which is often smaller than the diameter of the shackle body.

Inspect your hardware, in particular the shackles, regularly. This way you can avoid losing your ground tackle. Losing ground tackle happens – usually at a time when it is least expected and most inconvenient, thus maximizing damages.

Yacht Ownership

As marine surveyors we are offered a myriad of “stamped papers” which are served as a proof of yacht registration, or documentation or flag certificates – basically as proof of yacht ownership, or support thereof. Often a quick but careful initial assessment of documents received is required in order to decide whether they are legitimate. Sometimes we deal with poor scans, photostats, or whatever happens to be at hand. …

My Family and other Animals

“Dear Naci, further to our conversation, please could you contact our client to assist him in arranging to get his vessel fumigated to eradicate some scorpions that have been found on board.” The instruction by the insurers’ claim handler was brief and somewhat frightening. My first thought was “Is there an infant on board?”, as, albeit very rarely, the local scorpions have been known to poison kids to death. …

Sogged Rudderblade

Surveyor’s Opinion to Strapped Full Rudderblade on a Taiwan built Force 50 Ketch: “At my inspection the GRP rudder blade had been dismantled for a while and was placed under the vessel. About 10 bores of about 40 mm diameter had been drilled into the blades sides/ cheeks with a punch drill. Most of the bores had reached the foamcore of the rudder blade, some had reached the opposite laminate. At the time of my inspection I could confirm the uniform and very high moisture readings reported before. The foam core was partially darkened (as it happens with moisture ingress) but looked mostly in honey colour. From the one core sample I could inspect, I concluded that the adhesion between the core and the GRP cheeks of the rudder was not bad. …

Surveyor’s Comments – Fatigue Crack on a Shaft

“Surveyor’s Comments: According to my analysis of the fracture surface and observations on board, the shaft is broken due to fatigue and not by striking a submerged object or catching a rope etc.

The fatigue fracture surface is characterized by its smooth appearance with almost no plastic strain. Beach marks[1], indicating the position of the crack front at various stages during propagation, have a typical semi-elliptical shape. The final rupture (low in the image of the fracture surfaces) is ductile[2]. The final fracture surface is very small in comparison to the area of fatigue cracking. …

Surveyors’ Experience with Crafts of the Ferretti Group

All three surveyors of the marineSOLUTIONS team, Cem Baykent, Capt. Naci Arıcı and Dr. Yusuf Civelekoğlu, have been at some stage part of a Ferretti Master Service. Formed on 31.3.2009, this was at that time the first and only Ferretti Master Service outside Italy. The Ferretti Group appoints few of their service points as Master Service, and only if a service point has proven, in a consistent manner, to be able to carry out complex repairs to a good standard.

As the Ferretti Service and later the Master Service, we have experienced thousands of issues of the group yachts and thus covered almost all aspects of the vessels. One incident, namely, the grounding of a Ferretti 881, is of particular importance to us. …