Tuesday, September 1, 2009
When one hears the words interior painting you might be inclined to think of paint and how it relates to ones house. The interior painting system on the trawler is more about function than making her pretty. Most of the interior painting will never be seen again and it's sole purpose is to stop corrosion from occurring. The interior paint we will see will be down in the bilge area and again the paint serves as a corrosion barrier. Steel boats of the past have earned a not so favorable reputation due to rust corrosion. The steel boats of yesteryear rusted away from the inside out. I've seen quite a few older steel rusting hulks that had little or no paint on the inside sheathing and framing. These old boats got built, some paint slopped on them, then covered up with plywood...out of sight, out of mind. The materials and methods offered to us builders today will give steel boats the ability to outlive all of their builders without turning into rusting hulks.
I'm building my boat using wheel abraded and primed steel. Wheel abrading is a method of removing the mill scale from the steel utilizing a machine that throws steel shot or some other abrasive at the steel then the metal is primed as it exits the wheel abrading machine. Mill scale is the dark coating one sees on new steel and must be removed prior to painting. Since I'm building inside of my shop and I had the mill scale wheel abraded off I do not have to do any heavy sand blasting of the boat. Because I'm inside I've not had to worry about heavy rust forming during the build. The designer of the boat was also careful to not design corrosion trapping pockets in the framing where water could sit or accumulate and cause crevice corrosion to start. All the frames and longitudinal stringers have "mouse holes" cut in strategic areas to allow water to pass freely and collect in the bilge's.
To prepare the inside of the hull for painting the first step was to grind all the tacks, splatter, and garbage off of all the metal. Then I used my shop sand blaster and blasted all the welds and areas I had ground. I then used my sand blaster to give the interior a light blasting to "tooth" the existing primer so my primer would stick to the existing primer. I'm using epoxies for all the paint and for the primer I alternated between white and gray so I could see the coverage. I applied three coats of primer then three more coats of top coat. For the top coat of paint I used acrylic enamel.
The areas above the water line on my boat will get insulated with sprayed in polyurethane closed cell foam. The areas below the water line will have no foam. For the below the water line areas I added another coat of paint utilizing an insulating additive in the paint. This insulating additive is a NASA technology that gives an "R" value to the paint and prevents condensation. I used the "insul-add" in a primer coat and have no real complaints as to how it sprayed. The material was not that expensive and if it does half of what is claimed, I'll be extremely happy.
These pictures are of the forward bilge area. I'm showing these pictures because these shots also show the mounting brackets for the water tanks.