Prüfen des Altanstrichs
Where a repeat coating is being applied it is important to determine whether the existing coating is still properly bonded to the subsurface.
The degree of bonding can be tested easily using a highly adhesive strip. Press the adhesive strip onto various points on the surface to be coated, and then pull it off with a sharp jerk. If old coating material sticks to the adhesive strip, the coating should definitely be removed – otherwise successful bonding of the new coating is impossible. Former coatings can be removed by sanding or chemical stripper – the latter only for 1-component products. Please note that old antifouling coatings should be removed with wet abrasive paper.
Basic Rules for Re-coating
If the existing coating is in tact there are some important rules which should be followed:
- Where the composition or structure of a coating is unknown it is recommended that the coating be re-constructed from scratch. The chances of saving time and money by experimenting are slim, and the results usually unsatisfactory
- Only apply a suitable new system to an existing coating.
Rule of thumb:
- Do not apply 2-component products to 1-component underlayers – unless this is specifically endorsed by the manufacturer.
- Selfpolishing or teflon- (PTFE) based antifouling coatings can only be re-coated with the same material.
- When in doubt, contact the manufacturer directly.
All surfaces to which a fresh coating is to be applied must be thoroughly cleaned beforehand. In particular dirt, oil, grease, wax, silicon, stripper or similar material must be thoroughly removed before commencement of sanding. Failure to due this will result in a spreading of the surface contaminants across the whole surface area through sanding dust. This applies equally to first coatings as to repeat coatings.
Use special yacht cleaner, warm water and a brush, or a „Scotchbrite“ sponge. It can be seen when the surface has been thoroughly cleaned as the water will run from the surface uniformly, without forming droplets.
In order to ensure optimal bonding of the new coating the surface should be well sanded, so that it appears uniformly dull.
As dry sanding is usually a dusty business, wet sanding is recommended. This is also more economical as, providing it is keep sufficiently wet, the abrasive paper maintains its abrasiveness for longer. If dry sanding is favoured nevertheless, it is advantageous to use a sander with vacuum exhaust attachment.
Important: always wear a dust and respiratory mask when dry sanding.
Coating Thickness and Coverage
All Wilckens Yachtline products can be applied either with brush or roller. The surface area covered, as detailed in our product information is per coat, in the stated dry film thickness.
However, a reduction of approx. 10 % should be expected when painting or rolling, or 30 % when spraying. Where thinner is used a greater surface area can be covered, however the film thickness of the coating once dry will be thinner accordingly.
Due to the variety of different types of yachts and boats there is no generally applicable formula for the calculation of the surface area below the water line. The following formula however provides a rough indication:
Length of water line x (width + draught)
The surface area above the water line can be estimated with the formula:
2 x (overall length x middle freeboard)
0.6 x (overall length x width) less area of cabin, cockpit etc.
and for masts and spars:
Diameter x 3.14 x length