Need some help with fairing, etc.

[Lenny]

I started a new post as I got no replies on my 1st. I am going to be finishing up my casting platform and floor. Should I be using 407 and epoxy or Quickfair? How thick should it be put on? And has anyone ever put it on with a tile trowel and let harden then go back and fill the grooves?

[Blue_Heron]

...has anyone ever put it on with a tile trowel and let harden then go back and fill the grooves?

I don't have much experience with fairing compounds, yet, but I expect to in the coming weeks. I've seen and tried the technique you're talking about. I used a serrated trowel to apply fairing compound to my fuel tank hatch and then used a sanding board to sand it to a flat plane. The advantage is that you're sanding less surface area because of the grooves. And you also have the flat tops of the trowel ridges to guide your flat trowel when you apply the next coat, so it should be very flat. The potential downside is that you could get cracking along those grooves later. I'm thinking I'll lay up a single layer of glass veil over it when I'm done to prevent cracking. If you're going to try it, make sure to use a trowel with notches or serrations no deeper than the maximum depth of your fairing compound. Otherwise, you'll be sanding just as much as if you'd used a flat trowel.
Dave

[Cheg]

Quickfair is a good product.I am currently involved in what is often referred to as an intimate relationship(love hate I might add) with it. In warm temps keep the batches small. When doing initial coats, where it goes on fast, the most I mix up is 16 oz. I mix up half that much when fixing a lot of small divits that take more time. I read with interest the trowel idea. The surface of the cured QF needs to be sanded between coats. The resulting grooves that would remain after the initial coat would need to be wire brushed very well. The one time I just wire brushed the first coat, the next coat didn't adhere well enough(the leading edge would flake off in places)so I sanded it all off and did it again. Also mix it very well. The two parts when fully mixed don't look that different from unmixed part A. When scraping the sides to get every last drop out the batch I've had some unmixed streaks. It's made me obsessive about scraping the sides while mixing. Just some basic advice from a rookie. Hope it helps someone.

[strick]

I would not use quick fair for areas that require a lot of putty due to it's sensitivity as far as proper mixing ratios and temperatures. Better to make your own fairing compound out of cabosil and micro balloons and then put a layer or two of glass over these areas that require a lot of putty. When I use quick fair it's usually small amounts at a time teaspoon and tablespoon amounts. It's good stuff and it's all I use for finish detail fairing. It's good stuff as long as you dont screw up.

strick

[Blue_Heron]

...Better to make your own fairing compound out of cabosil and micro balloons and then put a layer or two of glass over these areas that require a lot of putty.

Chuck,
I've never used cabosil, but I have used microbaloons. Does the cabosil make the cured putty brittle or hard to sand? I recently picked up another product I'm going to try, 3M Glass Bubbles. Here's the description from U.S. Composites web site:

"These hollow glass microspheres can be added to any epoxy and polyester resin. These bubbles will make a lightweight, easy sanding putty for minor surface filling of cracks, holes, etc. (Color: White)"

I like that it will make a white putty instead of dark brown like the microballons. I'll post results on my Resto thread after I've tried it out.
Dave

[KenB]

I never really understood why you would use the microballons over fibers or cellulose.

Cellulose is super strong, much easier to work with (i.e. it doesn't go too airborne when mixed) and also is a super handy clean up tool... if you have epoxy on your hand just stick your hand in the cellulose bag and do the "hand washing" move and you should be all set. Plus cellulose (for example bought from progressive epoxy) is super cheap. Like 10% the cost of either quick fair or mircoballons...

So what am I missing? Harder to sand? Gums up sand paper more?

[Lenny]

So it looks like epoxy and 407 to cover the entire area and get that as smooth as possible then touch up with fairing compound? How do you guys keep from getting hills and valleys ? And how thick of a layer should be put down? By the way thank you for all the input.

[strick]

I never really understood why you would use the microballons over fibers or cellulose.

I dont know maybe it's heavier then the microballoons/cabosil and in boats folks are always trying to keep the weight down.

Dave yes the cabosil makes it hard to sand and brittle....you just have to keep the ratio just right...more microballoons then cabosil. Glass bubbles and microballoons mean the same thing to me. They may be slightly different between manufactures but to me they are one and the same. Keep in mind I am not talking about finish fairing just areas that need to be built up with a lot of putty. Cant beat quick fair for finish fairing.

strick

[DonV]

I'm long, long way from an expert on this, however fairing has to be looked at a multi-step process. No matter how great you think you have spread compound you will need another couple of applications to get it just right. I learned my lesson...get used to the idea it will take three our four layers and did I mention lots of sanding??

[ggreeby]

You should buy plasticaters ( plastic applicaters)to apply fairing compound. The nicer- smother you apply = less sanding. Remember you are creating a continuation of form . Multi. light coats are better = no air bubles. George