bpattonsoa
Well Known Member
Drywall mud. Don't laugh, I took a RV-10 cabin and doors from the raw contoured fiberglass to a finished primer coating in about 14 hours. There is one pinhole.
The first thing to understand is that the pinhole fillers are all some sort of liquid that holds talc (or calcite, mica, gypsum) in suspension and will hopefully flow into a pinhole to fill it. This method puts the talc in the hole and then turns it into a hard solid.
First is the contouring stage where the shape is formed. It includes filling with micro around and on the doors to get a good fit with the cabin top and the glass around the windows (if you do it). It is not included in my 14 hours.
Next is to sand the entire thing with #36 or so paper to open up all the pinholes and expose the weave of the glass. Clean the dust well, blow it out of all the crevices, pinholes and weave. You can see it, especially if you have a pink cabin. I used a small wire brush to scrub the white spots while blowing with an air gun.
Next take drywall mud and thin it out slightly, about 5-10% water, you want it loose but not soupy. Put it on with a hard squeegee, pushing hard to rub it in until it goes into all the holes. Sometimes it takes several passes until you see the mud filling the pinholes and weave. You don't want to leave a lot of extra mud on the surface. Ridges are easy to sand off later. This process is easier to do than explain.
After the mud is dry sand it with a block and #180 or so paper. I use a medium hard foam block. Remove all the surface drywall mud until all that is left is the dots and lines that are filling the pinholes and weave. If you over sand, add more mud and do it again.
Clean off the dust. Do not blow it with an air gun!! You can blow the talc out of the weave at this stage. I did it with a large brush and duster.
Now it is time to turn the talc into a hard filler. Mix some epoxy primer. You don't need as much as you would think, I used about 6 oz to do the complete cabin top and doors. Put it on with a squeegee. The talc will adsorb the primer and turn the color of the primer. Try to avoid leaving lines or drops of primer on the surface. I recommend a soft squeegee, window washing type, about 3-4" wide if you can find one.
When it is cured, sand with a soft block and #320 wet/dry used wet. Just sand enough to make it smooth, don't sand down into the original fiberglass. This is very rewarding because you can see the perfect surface, free of weave of pinholes. If there are any, you can go back and put in more drywall mud and repeat. I must have missed my one pinhole at this stage.
Prime with an epoxy primer and it is ready for paint.
This will work for any fiberglass surface. I got the idea from our local fiberglass expert who turns out some amazing paint jobs on his aircraft in a very short period of time. I did not include any discussion of masking or protection of other surfaces, but the time required is included in my 14 hours.
The first thing to understand is that the pinhole fillers are all some sort of liquid that holds talc (or calcite, mica, gypsum) in suspension and will hopefully flow into a pinhole to fill it. This method puts the talc in the hole and then turns it into a hard solid.
First is the contouring stage where the shape is formed. It includes filling with micro around and on the doors to get a good fit with the cabin top and the glass around the windows (if you do it). It is not included in my 14 hours.
Next is to sand the entire thing with #36 or so paper to open up all the pinholes and expose the weave of the glass. Clean the dust well, blow it out of all the crevices, pinholes and weave. You can see it, especially if you have a pink cabin. I used a small wire brush to scrub the white spots while blowing with an air gun.
Next take drywall mud and thin it out slightly, about 5-10% water, you want it loose but not soupy. Put it on with a hard squeegee, pushing hard to rub it in until it goes into all the holes. Sometimes it takes several passes until you see the mud filling the pinholes and weave. You don't want to leave a lot of extra mud on the surface. Ridges are easy to sand off later. This process is easier to do than explain.
After the mud is dry sand it with a block and #180 or so paper. I use a medium hard foam block. Remove all the surface drywall mud until all that is left is the dots and lines that are filling the pinholes and weave. If you over sand, add more mud and do it again.
Clean off the dust. Do not blow it with an air gun!! You can blow the talc out of the weave at this stage. I did it with a large brush and duster.
Now it is time to turn the talc into a hard filler. Mix some epoxy primer. You don't need as much as you would think, I used about 6 oz to do the complete cabin top and doors. Put it on with a squeegee. The talc will adsorb the primer and turn the color of the primer. Try to avoid leaving lines or drops of primer on the surface. I recommend a soft squeegee, window washing type, about 3-4" wide if you can find one.
When it is cured, sand with a soft block and #320 wet/dry used wet. Just sand enough to make it smooth, don't sand down into the original fiberglass. This is very rewarding because you can see the perfect surface, free of weave of pinholes. If there are any, you can go back and put in more drywall mud and repeat. I must have missed my one pinhole at this stage.
Prime with an epoxy primer and it is ready for paint.
This will work for any fiberglass surface. I got the idea from our local fiberglass expert who turns out some amazing paint jobs on his aircraft in a very short period of time. I did not include any discussion of masking or protection of other surfaces, but the time required is included in my 14 hours.
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