When it comes to painting your boat there are two main types of materials involved with this process; Primer and Paint. When going over the specific items and their purpose I am strictly going to focus on Roll Application and NOT spraying. Afterall the focus for my channel and this website is towards the DIY crowd. The reality is that most DIY folks are not setup for spraying, so rolling it is :-)!
When talking about Primer there are a few different options available and each of them has their purpose. There’s primer designed specifically for working with metals such as aluminum, High Build primers that are used as part of the fine tuning process to help get a surface free of minor defects such as pin holes and slight low spots, then finally there are Finish Primers which are typically the last layer of material before the actual paint is applied.
Throughout this write up I will focusing only on the Alexseal 442 Finish Primer mainly because it’s a material that rolls out beautifully. The other primers are really best suited for spray application so not something that I consider to be a DIY option.
Using a primer does a couple things for the overall finish. It provides a uniformly colored surface for the paint to be applied to which greatly helps in getting a consistent appearance with the paint (aka it eliminates blotchy-ness). Also it provides an ideal base for the paint allowing for much better adhesion. Technically can you apply paint without a primer? Yes but I would not recommend it, could end up being a fairly expensive experiment 😉
Primer generally is available in 2 different colors; white and grey. White primer should be used as a base for light / white paint colors as well as the bright vibrant colors. The grey primer should be used as a base for dark colors such as blues, greens, blacks, etc.
When trying to determine how much material is needed for a project we need to look at the Technical Data Sheet to see how much coverage can be anticipated per mixed gallon when rolling it out. I always found this info a bit confusing so here’s the simple explanation. The Data Sheet states that you can get 225 SqFt of coverage per mixed gallon of material. This would be for 2 quarts of the 442 base as well as 2 quarts of the C4427 converter (4 quarts = 1 gallon).
** Reducer or thinner is not taken into consideration for this coverage, it’s just the base material and the converter.
The 225 SqFt of coverage is for being able to apply 2-3 coats depending on how thick / thin the material is rolled out. I’ve always just figured 2 coats as there’s always going to be a little waste left over in the mix bucket or paint tray. Another way of looking at this would be to say that you can get 450 SqFt of coverage in a SINGLE mixed gallon coat (4 quarts of material).
Using a 30′ boat as an example lets say that there’s an average of 4 feet of hull from the waterline up to the rub rail. 4 x 30 = 120 square feet per side of the hull (240 SqFt when looking at both port and starboard sides of the hull). Figure in the size of the transom and lets just say we’re at 250 SqFt total.
So presuming that we can get 225 SqFt of coverage per mixed gallon of 442 primer (2 Qts Base and 2 Qts Converter) we would need just a bit more material to apply 2 full coats of primer to the hull.
3 Qts each of the 442 base and converter would be enough (yielding 1.5 mixed gallons) HOWEVER cost wise purchasing in that volume doesn’t really make sense. The cost of purchasing that volume of material in single quarts is more expensive than just buying it by the gallon and you get more material which would allow being able to apply 3 full coats of primer.
I generally recommend applying 3 coats of primer anyway so that there’s enough film thickness to be able to sand it smooth without accidentally sanding through.
The coverage for Alexseal 501 paints can be determined in the same way as the primer. Looking at the Data Sheet it states that you can get 244 SqFt of coverage per mixed gallon of material. This should be looked at the same way as the 442 primer in that is for 2-3 coats depending on the thickness of each coat.
So using the above 30′ boat as an example what would I recommend buying for painting the hull??
- (1) Gallon 442 Primer (white or grey depending on paint color)
- (1) Gallon C4427 Converter
- (1) Gallon R5015 Brush Reducer
- (1) Gallon 501 Topside Paint
- (1) Half Gallon C5012 Converter
- (1) Gallon R5015 Brush Reducer
Notice that I have R5015 listed twice? When rolling, both the paint and primer use the SAME reducer 😉 This would not be the case however if the material were being sprayed. So why double up on the reducer? Well it’s also good for cleaning brushes and any drips of paint / primer that may have landed where it shouldn’t have.
In addition to the above materials, one other thing I’d strongly recommend would be Alexseal’s 5018 Rolling Additive . This is an additive that’s mixed in with the 501 paint and allows being able to get a near spray quality finish strictly by rolling (no tipping with a brush). Pretty amazing stuff!
Hope this helps :-)!