This page is an explanation of how to Fair the surface of a boat, car or whatever prior to painting.
 

The basic concept for fairing is to build up multiple layers of various primers, "Block sanding" between each application with a long board that will bridge the low spots and only remove material from the high spots.  I switch colors of primer and repeat this process until I see most of that color disappearing one high spots. There is a technique for doing this effectively. I do what is called a "cross hatch pattern". I choose an area that is easy to work from where ever I am standing or sitting. Lets say I choose a part of the hull that my arms can reach and I am still comfortable. I envision a square area and I start sanding with the board at 45 degree angles until I have sanded the entire selected area. I then switch to the opposite 45 degree angle and repeat what I did in the first step, going right over the previously sanded area.

I watch carefully to see if any of the previous surface starts to show thru. If so, that indicates a high spot and if I am threw to that surface I can then see the low spots around that the sandpaper never touch. This is the first sanding on that coat of primer.
If I still have enough primer in my little square, I turn the board up and into a vertical position and sand the entire area with vertical strokes. Next I turn the board back to horizontal and I sand at a 90 degree angle to the previous direction.
The purpose for changing all of these directions, is to prevent my sanding from doing exactly what caused the dimples in the first place. They are generally caused by someone sanding the surface before with a round sander and tipping the edge of the pad up at about 45 degrees. Ultimately digging a hole in the surface.

As a rule when I have this much thickness to sand, I start with 89 grit. This makes the work go a lot faster and doesn't require so much labor.
I'll continue this coating and sanding with 80 grit until I feel I have created a surface that will work for me.

On my last coats of white 545 I sand it with 180 grit to eliminate the 80 grit marks that may still be visible.
Sometimes when I finish with the 180 grit I may need to spray one more, thin coat just to fill-in the 180 grit marks.
Now on this last coat I spray white (if I am painting the boat something close to white) and then I sand by hand careful not to sand thru to one of the other colors.

Now the surface is ready to paint.

With Awlgrip I spray the first coat with a fair amount of reducer. This first coat is so thin that it hardly puts a shine over the primer. I wait 45 minutes and spray another coat that isn't reduced as much as the first coat. Wait 45 minutes and spray another coat that is mixed exactly like number two coat.
Now after 45 minutes I need to inspect the surface carefully and decide whether I want to add a fourth coat.

Usually, the third coat is enough.

TIP: If you are good at spray painting you can substitute the Spray Converter with the Brush Converter. It slows the initial cure process a little and allows the paint to flow out better.

Over the next 15 to 20 days you will notice that the finish changes during this cure time.

 

CLICK ON ANY PHOTO BELOW TO VIEW A LARGER PHOTO

 

This photo shows Teri applying a single coat of 545 primer just to protect the sanded gelcoat from more UV damage until we can find time to start on the actual paint work.
 

Once you sand the gelcoat or fiberglass it is vulnerable to more damage if left exposed for very long.


Here we have sanded the protective coat of 545 and applied two more coats in preparation for paint.

 


After sanding the white 545 primer, I spray red High Build primer. Five coats are applied and allowed to cure for one week.

This is how I sanded the entire boat. I used a couple different sanding boards. One was 2 3/4 inch by
17 inch. Another was the same size but was made
of some sort of plastic that allowed it to conform
to the hull. These tools are available at Auto Body
Shop suppliers.

Here is a section showing the different directions I use the board. Note that the red and gray spots that remain, are areas that all three primers have slowly filled in. This may or may not be enough fill.
in fact I had to repeat this process many times until I could sand one coat down and not sand thru to a previous color.

 

Here you can see the size of the areas I worked with. Also note the yellow sanding block that curves to fit the hull. Note the various angles that I have used in this section.

 

All the block sanding and fairing have been completed. Next step is to apply three coats of white 545 primer.

At this point it is time to install any hardware or anything that will be bolted down. Here the rub rail is installed right on to the primed surface. The reason for this is that if you bolt something down on top of the Awlgrip finish, the paint will squeeze out around the pressure point and eventually crack

 

The last coat of white 545 primer has been sprayed, the port lights and rub rail installed and the primer has been sanded with 220 grit.

Always wear the best protection you can get your hands on when working with any of the paints. Be it sanding or application, these things are deadly.

A mask is not what I consider enough protection. You need to protect your skin, eyes, hair, everything.

In this photo I am wearing overalls, full face mask, hood over my head and gloves.

   
   
 
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