I write seeking some advice on Aluminum boats. I have a 50 foot Ferru Pilothouse cutter. This French boat is constructed in Al but has epoxy fairing compound in varying thickness over the entire hull and deck (damn those Frenchies). The vessel was neglected for a couple of years so blisters formed over a large surface area. We’ve been chipping away at these blisters to allow air at the Al to prevent further surface deterioration and now the boat looks like it has leprosy. Inspired by your lithe bare-metal “Beowulf”, I want to remove the rest of the fairing compound to lighten the vessel and avoid the sisyphean task of regular paint and epoxy maintenance. The remaining coating, however are tenaciously adherent to the metal surface. These are some of the questions I have… 1. Is it advisable to strip the boat bare? 2. What is the best way to deal with the tiny areas of pitting corrosion that have occurred where water was trapped between the epoxy and the metal? 3. What is the best way to strip the epoxy from aluminum without damaging the hull and deck? 4. Does sandblasting have to be done with aluminum oxide grit or could another material be used? 5. Do you know anything about the French boatbuilder, Ferru? We love to sail our boat and we intend to keep her for many years. We are currently living aboard in New York. I would greatly appreciate any assistance.
Hi Edward: Without seeing your boat and the condition of the hull/paint system I can only give you a few generalized answers. Hope these help.
1. Since you have already had a problem with blisters and are finding corrosion under the paint/filler system, stripping the hull to bare metal will give you a chance to evaluate what you have, and correct any ongoing problems. However, it may be that the problem exists above the waterline, and not below. If that is the case, i.e. you are OK below the waterline, you might consider leaving the paint system intact below.
When you strip off the topsides and deck you are going to expose a certain amount of unfairness in the metal–the amount will depend on the structural system and how well the metalwork is executed.
2. I don’t have any direct experience stripping paint I am happy to report! However, I called a friend who has done this with a 68-footer he is rebuilding. Richard used the following procedure: First, paint/fairing was removed using up to a 20 grit, silica sand. The sand must be clean (no iron contamination). 20 grit is really harsh, and your blasting subcontractor can experiment with finer grits. But 20 was required to get the fairing off Richard’s hull.
The crevice corrosion will need to be welded. The welding is easy, however, you must clean the welds. Small areas can be dealt with by using a die grinder with CARBIDE tipped tools. Really small areas can be cleaned with a sharp drill bit (again, carbide tipped). If you have welded seams, a 40-tooth carbide skill saw blade, set at a very shallow depth, works well.
Once you are through with the carbide tipped work, then use a stainless steel wire brush in a high speed grinder (like a 4″ Makita) to clean out the rest of the surrounding area.
3. I have no data on Ferru.
Good luck with your project!
Posted by Steve Dashew (November 30, 1999)
