SBD
The Dinky Davis - My Shiney Hiney
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on 07-14-2010 at 12:43 AM (1762 Views)
With all of the structural work done to the transom it was time to redo the gelcoat. I have never had great results with gelcoat in the past, and I was dreading this part of the job.
My initial efforts this time around also failed miserably. I tried rolling on straight white gelcoat and blending it in with a sander. The match and coverage were both horrible. This was not going to cut it...
I watched a few DVDs and searched the web looking for the "way". Finding the "way", or at least the way I used involved piecing together a bunch of different sources of info. Hopefully, I can make it easier for the next guy by putting it all in one place.
It became apparent that to cover an area of this size and get good results was going to requiring spraying the gelcoat. However spraying gelcoat comes with its own set of issues. Gelcoat is too thick to spray, so it needs to be thinned or "reduced" to be sprayed. Traditionally this was done with acetone, but that left it porous. Later people used styrene, but it eventually yellows.
In my research a number of folks had begun having great results using a product called Duratec. Duratec is really nothing more than really thin, clear resin. It allows it to spray almost like paint, yet still sand etc. just like regular gelcoat. In addition, you can over-thin it to blend in the repair etc. This little video really helped me get a handle on tinting gelcoat to match, as well as spraying and blending using Duratec...
With this new info I was inspired to go for it.
Tinting
I bought some pigment and Leah helped me get the color incredibly close using the simple system in video. If you decide to do this, I can't stress how little pigment it takes to alter the tint. We would add a tiny crumb to the gallon, stir, dab, and assess. It took ten tiny crumbs to tint the gallon. Another great tip is to pour off a small amount of the gelcoat and reserve it, so if it gets too dark, you can add some pure white back in to lighten it.
Spraying
To be spray the gelcoat requires a gun and a compressor. I bought a cheapo gravity feed HVLP gun designed for primer for $40.00. You want to find one with a 2.0 tip to handle the viscosity of gelcoat. Try and select a gun that also has a modest air demand, so you can get by with a moderate sized compressor. I bought a large 110 compressor from Home Cheapo for $380, and another $30 in hoses and fittings.
While this wasn't exactly cheap, it was significantly less than the estimates I got for doing the job, and I would get the the tools to keep. A good deal IF it worked!
Material and Mixology
This is the stuff to get...
For regular spraying mix these 1 to 1. On the edges where your trying to blend colors you can go 1:3. This will make your gelcoat translucent. This will allow the base color to show thru and make a seamless color transition.
Regardless of ratio you add 20cc's of catalyst per quart of blended material. Another great benefit of Duratec is it allows gelcoat to cure in air without adding a surfacing agent.
Prep and Application
I sanded the transom with 220, washed it, and then cleaned it with acetone. I then masked the areas I didn't want sprayed and went at it...
After the first coat it was all one color!!!
I did a total of 4 light coats. The final coat was pretty shiny and only had minimal orange peel. However the texture didn't match the texture of the rest of the boat so I decided to color sand it.
Sanding and buffing
Color sanding or wet sanding is simple but can be tedious depending of the quality of your starting point. To wet sand, wet the area, the sand paper, and go at it. Wet and rinse your work area and sand paper frequently. It is important to use a sanding block so you don't sand uneven areas into your work. I used a big Durablock to cover a lot of area.
Work your way from 400, to 600, to 800, to 1000, and then 1500. While this sounds like a big deal, it only took me about 2 hours.
After that I buffed it with 3m compound, and then 3m Finnesse it II...
Buffing only took about 45 minutes. The results of the whole process are awesome. The color matches great and the body work looks sweet...
The only down side is it makes the rest of my boat look like shit! Can you guess what I'm working on now?
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