I'll make you a deal: you teach me how to rivet and I'll educate you on glass work
Send me an e-mail or call and I can talk you off the ledge...
Dick
310 seven three nine 988 four
From your photo, it looks like you coated the fairing with clear epoxy. It's about the hardest product to sand. I find that your hand is about the best thing to find if your product is smooth, without bumps. Get the dust off and slide your hand over the piece, not too fast but not too slow. If there are any bumps or holes you will feel then (not the pin holes).
I think I spent an hour total on that part. No show plane here.
Just venting and looking to see if anyone shares my frustration, here is 30 hours on a piece of stupid fiberglass, and going to be another 20 to get it ready for paint, am I doing something wrong here. I miss riveting
Wayne,
We've never met, but your posts always strike me as though you are a person who's pride is inversely proportional to quality D
I use the sanding belts because they cut better and last longer than regular sand paper. I am not saying that is the only way. just the way I have done it for many years building glass boats to a Glasair 1TD.So why sanding belts?
Bret, you're working on the most difficult RV part in terms of surface contour, as it's all concave or convex faired into concave. Still, it's just sanding. You wouldn't bitch this much if it was a block of wood.
Shape is something you do in the layup and fairing steps. The shape of the raw layup is controlled by mold or form shape. Time spent on the mold or form before starting the actual part pays a large dividend later, in the fairing stage.
Fairing is where we correct surface contour. I am absolutely amazed at the variety of filler material so often seen slapped on the same part. Ask about it and you always get a variation on the same answer; they were looking for the magical easy product. What they didn't realize is that different fillers sand at different rates. It makes it more difficult to flatten the surface profile, as the harder fillers become highs and the soft fillers become lows. In general, stick with one filler mixed at the same ratio every time.
Let's assume you are very close to the desired surface profile. The epoxy is there to seal the surface, nothing more. All you need to do is scuff it smooth while leaving a bit of tooth for adhesion. It's only a few 0.001's thick; about the only mistake you can make is to sand it too much, cutting back into the underlying glass fiber.
Is it hard to sand? Depends on what you're sanding with. First, sandpaper is a shop consumable. Don't be a cheapskate; buy the best and change it often (I mostly buy 3M gold Stickit disks and Green Corps 3x18's). Second, although it might not help you much on this particular part, an air orbital is a required shop tool. Third, think about grit size; what is the largest grit scratch you can cover? Attacking the epoxy coat with 300-600 grit paper is pretty dumb when a subsequent coat will be a thick primer-surfacer. Use a new sheet of 120; no problem covering a 120 scratch.
I visited a major aerospace composite contractor plant a few weeks ago. Know what they were using to seal raw glass? Epoxy mixed with cabosil.
Fast, cheap, good...pick any two.
Hey Bret, I must admit that I AMA power tools guy when it comes to finishing glass parts - I'd be using a little mouse sander for that part, at least with the hard candy coating - at least until I got all the high points off. If we weren't so swamped at the house project, I'd pop over the hill. Are you building at KMEV, or at home?
Ok, nice to meet you, but, did you just say one hour For the EMP fairing? or to make a flat area on a flat piece of material flat? I started this thread just to vent my frustrations of not being a skilled fiberglass manipulator, and to survey the crowd for similar frustration. Misery likes company. I like the polyester stuff, I am using Metal Bite glazing putty, it works but as Dan mentioned, it is softer and sands down faster than epoxy. Hence, inadvertently adding complexity to my messed up project. As you can tell, I am done for the day, having a beer and reflecting on another day of aircraft buildingIn a former life I worked with Bondo (polyester resin). It can be applied up to 1/8" and forms easy with a cheese grater and 80 grit sand paper. This job shouldn't take more than an hour. The vinylester resin and epoxy are both very hard to achieve final form but are superior in strength?
Standing by for incoming!!
Ug I should have left it alone, just shot black epoxy primer and of course it shows everything, what looks good unprimed is very deceiving. I'm glad I am building an aluminum plane. Tempting to throw it out and start over, the only good part is the wrap around the HS glove fit. Going to wait a day or two and start blocking. Apparently 60 grit is only good for?????? What is that saying. Build on?
Here is what I would do.
1: Sand smooth with 180 grit paper.
2: Eyeball for pinholes.
3: Fill any you see. I use Evercoat "Glaze Coat" P/n 417
4: Sand the filler
5: Prime with PPG K36 primer. It's easy to get, dries fast, and sands real nice.
6: back to step 2.
7: After 2 or 3 applications of primer sand with 320 sand paper if ready to paint or just leave it for your painter to do it.
... if I was not a poor blue color worker I could probably hire a painter, but, I am the painter, by the pic you can see why I am spending more than one hr on the EMP fairing
- I'd be using a little mouse sander for that part, at least with the hard candy coating - at least until I got all the high points off.
#7 (or just leave it for your painter) well if I was not a poor blue color worker I could probably hire a painter, but, I am the painter, by the pic you can see why I am spending more than onehr on the EMP fairing
I gave up working on my doors and canopy when it got to last winter and too cold for fiberglass work. Just stopped again for this winter..............
I could NEVER build a glass aircraft - hate it!