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The underwater ship


This is how you get your yacht ready for a successful season on board!

As long as our ship is still on land, it makes sense that we take a closer look at the underwater ship. After all, this is basically the foundation of the boat.

From the condition of the hull below the waterline, one can deduce the general maintenance condition with a fair degree of accuracy without even having looked on deck. If many old layers of paint are “stacking” one on top of the other, perhaps with clearly visible areas where once whole slabs have fallen off and which have simply been painted over, then it doesn’t look good – neither down here nor, presumably, above the water line. Because if you take good care of your ship, you will, with good reason, start down here.

Even if it may be tedious: The old paint has to go down! At least most of the layers of it, depending on the condition, although it doesn’t do any harm to completely rebuild the paint structure including the primer every few years. Only then can you really inspect the fuselage and only then will the coating really hold up.

Scurrying across the ship with a high-pressure cleaner in autumn and then applying a new layer of underwater paint in spring is in any case not sufficient in most cases. Since we are dealing with an anti-fouling paint, which for this purpose also contains less health-promoting substances, you should use a machine with a suction device and bag and wear complete protective clothing, including protective goggles and a breathing mask.


Step by step to the goal

Don’t panic

If, on a GRP ship, there are a few bubbles in the waterline, you don’t necessarily have to panic, because that doesn’t necessarily mean that the feared osmosis disease has devoured the entire ship. However, you can then take a closer look at other areas of the underwater hull and if you have any doubts, you can also consult a specialist, i.e. a boat builder or appraiser, with their moisture measuring devices to determine the actual condition. The small bubbles mentioned, which can be found every now and then, especially in the area of ​​the waterline, can be simply scraped out and filled with GRP or epoxy putty, provided that no bad-smelling liquid runs out after opening them (that would be a sign of osmosis).

Keel, rudder & propeller

Then you can also take a look at the keel and rudder on sailing yachts. Are there rust noses running out of the area where the hull and keel join? Then you should probably inspect the keel bolts from the inside in the bilge. Pulling keel bolts and replacing them is, however, a job for a shipyard. You can also bravely wiggle the rudder blade to check whether the rudder bearings are worn out. Take on the propeller, free it from growth and smallpox and maybe protect it with a special propeller paint. Folding propellers can sometimes fail if they are used too seldom and are occupied by smallpox in the course of a season at the berth, with fixed propellers, on the other hand, you lose at least a good bit of performance. The Dutch paint manufacturer Epifanes or Hempel and International, for example, offer a brushable silicone coating specifically to protect propellers.

Smallpox in the through hulls

Smallpox also like to settle in the through-hulls, i.e. in the inlet and outlet of cooling water or toilet. They should of course be free, so you have to scrape them out thoroughly. In the worst case, the smallpox sit so close together that too little cooling water runs through or that the sea valve at the inner end of the passage no longer closes properly.

Timely replacement of the sacrificial anodes

The zinc or sacrificial anodes, which protect various metal parts from electrolytic damage under water, should not only be replaced when they have already been completely eaten away, but rather when only about half of the original size is left. Electrolytic reactions can turn out very differently, depending on where you are at the moment or what is so “going on” in this respect in the immediate vicinity.

Biocide-free underwater paints

Finally we are ready and can apply the new underwater paint. This is done with a roller, not too thick, on a smooth, dry and clean surface. All underwater paints with anti-fouling properties must be registered within Europe and bear a corresponding number. Theoretically, you can get the list of the substances contained under this number, but in most cases you can already do this on the manufacturer’s product sheet.

Some paint manufacturers have biocide-free underwater paints in their range that meet today’s regulations. On some inland waters, however, special rules may also apply with regard to underwater paints, which you have to find out about from district to district.

Innovations based on silicone

The coating of the underwater hull with an anti-fouling film, which also meets all environmental requirements, is brand new.

The main component of the film is silicone, the film should reliably protect boats from fouling for several years. If the ship is in port, a layer of slime forms, which is washed off when the boat is in motion. An additional plus: The friction resistance in the water should be significantly reduced by the film: According to the manufacturer, more speed for sailing boats, less consumption for motor boats are the positive consequences. They also rely on silicone with the brushable Silic Seal, which complements the new Silic One series and has similar properties to the film solution.

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