April 1999 Telltale page 7 - by Tom Winlow and Marcel Laroche.
Soon it will be time to clean and polish your hull again.
Begin by washing the deck. Washing the heavy dirt now will minimize the amount of washing required after launch and the associated soap streaks on the newly polished hull as well as pollution (phosphate) in the harbour.
Using lots of soap and water, thoroughly wash the hull. Now you have a decision to make. If last year it did not shine as well as in previous years and it seemed to have greasy streaks, it may have too much old wax. It is time to remove it. Automotive body shops use a dewaxer called "PREP SOL", (generic term) available at places like United Auto Parts and CTC, to remove all waxes before sanding and painting.
Once the hull is dewaxed, it may be a good idea to go over it with fine rubbing compound even though it does not look oxidized. This will remove any remaining dirt and a very small amount of gelcoat, thus restoring its original colour. Now, give it two coats of wax, polish each to a bright shine and add water.
For boats which are obviously oxidized, wash and remove the wax as per above. Find the most oxidized area, and using a medium grit rubbing compound, apply with a polisher/buffer. Using a spray bottle, spray some water in the area being polished. This prevents the rubbing compound from drying up too quickly and helps the cutting action of the compound. Do a small area at a time and wipe off the compound before it dries too hard. The rubbing compound contains a small amount of wax, and when you wipe it off the small area, it will shine and give you an indication of the finished product. Usually a second application is required in some areas. Keep the polisher/buffer moving at all times to get a more uniform colour restoration. Once you are satisfied with the results, wax it and add water.
On badly oxidized hulls, rubbing compound may not be adequate; sanding with 600 grit or finer wet and dry sandpaper is the last resort. Do not use a coarser grit, as it will be difficult to remove the sandpaper marks. Using a spray bottle (not a hose) and a palm sander, sand the area while spraying water on the area. Too much water is better than too little, as it washes away the sanding residues and keeps the sandpaper from clogging. Avoid spraying water directly on the palm sander. Keep it moving and apply only light pressure. Let the paper do the work. Remember that gelcoat is only about l/64 th of an inch thick. Once you have finished sanding a small area, wipe it clean. It will have a dull finish. Now apply rubbing compound and restore the shine.
I have rejuvenated the gelcoat of five hulls with good results using this method.
Clean and dewax as for gelcoat hulls. If paint is faded use fine grit rubbing compound, then wax with car wax. When using rubbing compound, remember that the coat of paint is very thin (paper thin), so go easy with the rubbing compound. If rubbing compound does not give good results, try an automotive colour restorer. Never use sandpaper because you may go through the top coat and into the primer, which may be of a different color than the top coat. When satisfied with the results, apply two coats of wax to the hull. It is not possible to make new out of old, but with care, patience and elbow grease, good results can be achieved.