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Thursday, December 11, 2014

Kingfisher Drift Boat Build - Painting the Interior with Durabak

I've been preparing for painting the interior areas that will be painted with "Durabak" polyurethane truck bedliner. It is a do-it-yourself product that can be applied by brush, roller or sprayed. Because of all the detailing I will be doing most of it with a roller and cutting in the hard to reach spots with a brush. I'm using the Durabak 18 which is a UV resistant product.

Here's the finished product. Believe me it's a lot of work!

With the Kingfisher I'm painting the following areas with Durabak 18.
  • The floors
  • The inside and outside of the dry boxes
  • The inside and outside of the two pedestals for the seats
  • The two hoops for the rowers seats
  • The base of the rear casting brace
  • The sides up about 6" to 10" depending on the area

Preparing the surfaces

Once I installed the wood plugs for attachment of pulleys, foot braces and the 3 drain plugs I had to fair all of the surfaces to be painted with Durabak. I used an epoxy mixed with micro balloons. This is a fairing mixture for smoothing the surfaces. I used a fast set hardener with it's compatible resin. Micro balloons create a low density filler that is suited for fairing, smoothing out, large areas. It is approximately 30% easier to sand than epoxy thickened with wood flour. When you are doing large areas this really helps. 

I purchased the micro balloons at TAP Plastics of Sacramento, CA. I mixed up batches of 2 ounces of resin to 1 ounce of fast set hardener. This allowed me time to work the filler with a squeegee or a brush and not have it run and drip too much. I mixed the filler to a mayonnaise type consistency. On the more vertical surfaces slightly thicker. I used this filler on the bottom and on relatively vertical surfaces.

Once the filler had set, I sanded the surfaces with 80 grit discs with a 6" or 5" random orbital sander. Once sanded I vacuumed up the surface and reapplied the fairing mixture as necessary. I faired all the surfaces in two layers, sanding in between. Being the Durabak has rubber granules mixed in with it, the surface needs to be flat but not perfect.  This was the first time using the product and I think I probably did a better fairing job that I really needed to.

Once the fairing was completed to satisfaction I sanded all the areas that would be coated with Durabak one last time with 80 grit sandpaper. I hand sanded all the inside corners and areas I could not sand with the random orbital sander.

I vacuumed the surfaces and then used Xylene to clean and etch all the surfaces. The Durabak instructions were very clear to only use Xylene.  

Some of the areas, like the caster's knee brace, was difficult to fair and to mask. I think it came out pretty cool though!

Masking the Surfaces

The areas that were to be varnished and not coated with Durabak had to be masked completely. Durabak is sort of messy and I did not want to have to clean off any drips. I used 1/4" wide masking tape to establish the line to be painted to. I then applied a strip of 3/4" blue masking tape to that line.   Then I used a 3M masking machine with 12' paper and 3/4" blue tape to complete the masking job. I'd say it took me 3 to 4 hours to mask everything off.

This photo shows the inside of the dry boxes, the front pedestal and the line painted forward to the stem (bow). The mahogany deck that will be attached on top of the dry boxes will extend forward to the stem.

Applying the Durabak

It is important to get organized prior to any painting project and this is one of those. I had to gather up a number of items and get everything laid out and organized prior to starting painting. Things like:
  • Xylene to thin the Durabak if necessary and to clean up messes
  • 4" roller frame
  • Special 4' foam rollers provided by Durabak (2)
  • Disposable paint trays for a 4" roller frame
  • A soft Polyester brush
  • A metal mixer wand  - 1 gallon size
  • Wooden stir sticks
  • Rags
Durabak can be thinned up to 15% with Xylene. I opened the Durabak 18 can and used the metal mixer wand in a cordless drill to stir the material. The instructions are explicit about doing this. Durabak comes in a smooth or a textured type. I'm using the textured. Rubber particles are suspended in the polyurethane paint. The paint must be stirred on a regular basis to keep the particles in suspension. I decided to apply the Durabak straight out of the can. In retrospect, I believe I should have thinned it slightly as I had trouble having the rubber particles clump together. I had to really work the material to spread the rubber particles out evenly. 

The material was fairly easy to apply and I had the first coat done in about 1 1/2 hours. When the first coat was down I was a little disappointed in the way the rubber particles were spread around. The material is recommended to be applied in two coats so I was hoping that the second coat would even the finish out a bit. I waited for the material to be dry to the touch, about 1 hour, to start with the second coat.

I decided to thin the second coat by about 5%. I'm glad I did. I had purchased 1 gallon and had used about 60% of it on the first coat. Thinning it did the trick. It spread evenly and nicely and I had just enough to give everything a second coat. The rubber particles were spread fairly evenly. It's not perfect but it will be fine.

This is the rear Pedestal and the rounded transom. All the wood grain portions or the boat will receive many coats of marine varnish.

It is also important to pull all the masking after applying the second coat and before that Durabak sets up too much. All the photos were taken about 1 hour after the second coat was applied.

Up Next!

I can finally install the 1/4" mahogany decks. They have been fitted and have been flow coated twice with epoxy. They are sanded and ready to install. 

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Have any Questions or Comments? Let me know, Clay.