Fairing Deck

Rick · Post by **Rick** » Wed Jun 11, 2008 2:01 pm

I've begun fairing the deck with West System epoxy and a blend of their 407 & 406 fillers. I've got 2 questions about the process. First, do I need to scrub and rinse the applied fairing once it dries to remove amine blush before I sand it? Second, how long do I have to wait before sanding and applying a second coat of fairing? Thanks.

Rachel · Post by **Rachel** » Wed Jun 11, 2008 2:31 pm

1) I would wash off the amine blush, myself (it's not always there, but I just make it a regular habit). You don't need to scrub too hard, I don't think.

2) You just have to wait long enough for the epoxy/fairing to cure enough so that you can sand. If you sand too soon you'll get gummy little epoxy bits clogging up the sandpaper instead of dust. You can do an initial check with your fingernail or etc. -- you should no longer be able to dent it. If you do start sanding too soon, no big harm; just stop and wait for it to cure further. The actual time varies depending on your epoxy mix, the temp. and humidity, etc.

Quetzalsailor · Post by **Quetzalsailor** » Wed Jun 11, 2008 4:09 pm

I don't know how much of a mess you're making with the first application of fairing goo; I'm pretty slapdash. You can stiffen the fillers such that you have a little better control. Anyway, I use a Surform for my first pass. It takes my excesses down pretty quickly and it doesn't fill when carving still-not-rock-hard epoxy. The shiny places show where you need more filler and where you need to remove the amine blush. I then sand with a palm sander, including the shiny dips. Then refill; it will be much easier to hit the desired finish level since you're working to an established shape.

I've found that the second application effectively 'wets out' the first and that film of neat epoxy is a harder sand than the filler. I use a large mill bastard (no, really) file and knock the whole surface into uniform before sanding.

What I haven't got at hand is the epoxy equivalent of the lacquer-based 'glazing putty' that you use for minor blemishes between lacquer primer coats and under the lacquer top coats on car bodies. I think I've seen polyester-friendly glazing putties. I'm chary of mixing too many kinds of fillers and paints; something will object.

I recently finished rebuilding my rudder. An exhaustive collection of pics of the work in progress, which include fairing, can be seen at: http://s278.photobucket.com/albums/kk90 ... %20Repair/

Hirilondë · Post by **Hirilondë** » Wed Jun 11, 2008 6:28 pm

Rick wrote: First, do I need to scrub and rinse the applied fairing once it dries to remove amine blush before I sand it?

No, but it will make sanding easier, and you will load a lot less sandpaper. And you should definitely clean with water before appling the next coat if you let the epoxy cure. Before sanding is surely preferable.

Rick wrote:Second, how long do I have to wait before sanding and applying a second coat of fairing? Thanks.

You don't have to wait at all. As a matter of fact, the less you wait the greater your chance of some primary bonding.

Post by **Tim** » Thu Jun 12, 2008 6:11 am

It's safest to always assume that amine blush has formed, and treat the surface accordingly.

I always wash all epoxy before any sanding, period.

feetup · Post by **feetup** » Thu Jun 12, 2008 10:02 am

If you have the time to watch the epoxy fairing material cure, possibly while working on another area of the boat you can save yourself quite a bit of work by removing the worst of the high points while the filler is is in the green state, ie not sticky, but not completely hard either. Use a sharp surform or a body file. When completely cured, either wet sand, or scrub/dry and then dry sand. For me, wet sanding seems to go faster, and certainly clogs less if you used good paper. I have modified a double insulated 1/3 sheet sander, and a 1/4 sheet palm sander with rubber platens for use wet. I don't know if I would use them if the boat was in the water, but with a gfi breaker in the line and my feet off the ground I feel comfortable sanding on the flat, or vertical. I just keep the water on the surface.

Tim J

Rick · Post by **Rick** » Thu Jun 12, 2008 1:25 pm

Thanks for the info. I'll wash the blush before I start sanding. In this heat, the fairing is hardening quickly and it's good to know I don't have to wait to sand and recoat. I hadn't thought of using a file (I've got a surform, that I'll use on the high spots). I've segmented the deck and toe rail areas so I can fair, wash the amine blush and sand different spots as suggested. My project time is limited, so I had been quickly hitting numerous areas and returning later to refair. I finally realized that I'm creating extra work by not being more careful with the initial fairing.