Fiberglass Finishing

[f14rio]

Alright guys I have been reading and reading and reading about fiberglass and the various techniques but I can't seem to find anything in regards to finishing.

I am currently working on the canopy rear skirt and have done the layups but now it is time to fill the lows and finish it off. What do I use? I have glass bubbles (is that micro balloons?), flocked cotton (is that flox?), West Systems epoxy and Superfil.

From what I have read I think I need to mix up a batch of epoxy and glass bubbles and fill, sand repeat as necessary. But where does the Superfil come in at? What consistency should the bubble mix be? What grit sandpaper do I use?

After filling the lows, do I add another layer or two of 'glass?

Thanks!

[apkp777]

There are 3 things to consider when finishing fiberglass layups. Strength, weight and flexibility. Ideally you want something strong, lightweight and very flexible. Epoxy alone is brittle, heavy and inflexible. So we mix it with other stuff to give it what we need. Some stuff weakens it, some strengthens.

Microballoons are NOT the same as glass bubbles. They are epoxy coated with Phenolic. Very nasty to inhale. Try to avoid them. The are reddish in color. Very easy to sand however.

Glass bubbles are used as a sand-able filler, Supefill is used as a substitute.

Flock is a mixture of cotton (or milled fiber works too) and epoxy. Flock is structural where bubbles are not. Difficult to sand. Use it sparingly.

The fiberglass procedure is pretty simple

1. Wet layup - of cloth and epoxy. This will leave a very uneven surface in most cases. There are some tricks to make it relatively smooth however. Sandwich the wet cloth in between saran wrap and squeegee out the air bubbles and excess epoxy. Use a "peel ply" release cloth also will help.
2. Filler - Fill large voids and gaps with Flox
3. Finishing - Small voids, contours and dents use glass bubbles/epoxy mix or SuperFil.

Some people hate fiberglass, it is nasty. Try to be patient and don't expect that one or two applications of your filler will be enough. I have not done my glass work yet (not on my plane), but I plan to do all the parts at the same time. Everything will get the wet layup, then filled, then finished. Hopefully keep the mess to a minimum.

BTW- when sanding have a vacuum in one hand and the sander in the other, it won't be nearly as dirty (or toxic)

[apkp777]

I just read up on SuperFil. I think I am going to order some of this to use for the small divits on my sheetmetal (tooling marks) Probably will bond better than bubbles/epoxy. Should be a good filler and easily sand-able. Pretty $$ though. For the canopy skirt, bubbles will do the trick.

[Transporter]

For those new to epoxy, I'd recommend reading the West Systems guides at:
http://westsystem.com/ss/use-guides/

I'd also recommend "Devlin's Boat Building" by Samual Devlin (ISBN 0-07-157990-7) published by International Marine/McGraw-Hill (1996). Devlin provides finishing technique/tips in Chapter 24.

Good luck,
Mike

[rv9aviator]

Going on information from another post I bought West Systems 410 micro filler to mix with the West Systems epoxy resin and hardener. I used it on my elevator tips to fair the joint and fill low places. It is about like working with Bondo except much lighter. It sands like regular auto body filler. It is not structural but I only used it to smooth up the surface. Unless someone tells me different I am planning on using it to smooth up the canopy skirts as well since the fiberglass layups will have the strength necessary. The only downside is the time it takes to set up before you can sand. I wait overnight and then it is sandable. Go check out the West Systems user guides and videos. They are a big help as the previous post suggested.

[jferraro17]

West has a quick hardener that won't take overnight...can't remember the number right now.

Joe

[erich weaver]

Originally Posted by f14rio

What consistency should the bubble mix be?

The microballoon mix should be the consistency of cake frosting. Any thinner and it will run; any thicker and it doesnt spread/fill well.

If you are just using the balloons to build up small areas, there is no real need to put fiberglass over the top. In cases where a larger area is involved, encasulation of the area with one or two two thin layers is appropriate. I did this where the elevator meets up with outboard end of the horizontal stabilizer because of the mess of rivets in this area - I wanted a smoother look.

erich

[rv9aviator]

205 hardener sets up faster and is needed in cooler weather. I just don't have any right at the moment.

[David_Nelson]

When I purchased my West System kit (resin, both 205 and 206 hardener, and pumps), you are supplied with a single hardener pump. You can't purchase just an additional hardener pump. With the cooler wx, I wanted to switch over to the 205 (fast) hardener but was leary of just moving the pump over and contaminating the hardener. I called up West System back in December 2009 and inquired about this problem and they said 'no problem'. Just make a best effort to get most of the old hardener out then move the pump.

[f14rio]

Thanks for all the information fellas!