Fiberglassing canopy fairing

Can anybody give me some hints on this part of my project? I read all of Vans writeup but I usually find that I wish I had the thoughts of an experianced person as I move along.

I am using West systems.

One thing that is on my mind is when you place a fairly dry slurry under the front of the plexi, what keeps it from becoming a mess on the inside of the dash?

I am sure I will have more questions as I proceed and learn more. Starting tomorrow.

Thick is good

Carl,

The first bit of epoxy/resin work you do there is to "seal the gap" between the canopy plexi and the foward top skin with a resin/flox mix. Mix this thick like peanut butter or slightly thinner, and it won't run under the plexi and out onto the dash. Once that sets up, you're good to start the normal epoxy resin / fiberglass routine.

I mix black dye into the slurry and the first few layers of glass. You won't have to try and paint the inside of the windscreen to get rid of the ugly white.

Norman,
What did you use for the black dye?

Alan RV-4

why no polyester resin?

A little off the subject here but can someone tell me why you shouldn't use polyester resin? Will it eventually work it's way loose? I ended up getting polyester and now need to order epoxy but was just curious as to why it won't work.

I painted a 1.5" flat black strip on the in side, for bllackening I used PPG black tint from my paint mixing store, worked good with the epoxy (tested first) got a whole pint of the stuff, used it for tinting white to match Van's grey.

TAP Plastics

TAP Plastics carry the pigment. I've used the black stuff and it doesn't take much. I think I bought it through Aircraft Spruce but it's a TAP product. For a small batch of epoxy/ slurry, it only takes about as much as can fit on the end of a popsicle stick.

Jim

ditch said:

A little off the subject here but can someone tell me why you shouldn't use polyester resin? Will it eventually work it's way loose? I ended up getting polyester and now need to order epoxy but was just curious as to why it won't work.

Click to expand...

Catalyzed polyester resin will attack the plexiglass, leading to crazing and structural weakness. Do not get it anywhere near plexiglass, even the fumes will attack it.

You'll need to invest in epoxy resin and measuring pumps. Expensive, but you will use it a lot in your project.


V

It's worse than that.

vlittle said:

Catalyzed polyester resin will attack the plexiglass, leading to crazing and structural weakness. Do not get it anywhere near plexiglass, even the fumes will attack it.

You'll need to invest in epoxy resin and measuring pumps. Expensive, but you will use it a lot in your project.


V

Click to expand...

Yup. In addition:

1) Polyester resin doesn't harden fully at the surface, which means it sands like cr*p.
2) It doesn't laminate in thin layers as well as epoxy, partially due to the above, and partially because it's not as good an adhesive.
3) It shrinks up to 7% in volume, and does this slowly over time.
4) The adhesion to metals is poor because the shrinkage causes interface stress, leading to cracks and separation.
5) The post cure shrinkage causes what you thought was an attractive finish sanded surface to shrink down below the glass weave and look like cr*p.
6) It's more brittle, and so doesn't handle impact or vibration as well as epoxy.
7) It stinks!

On the plus side, it's cheap.

Thats what I needed to hear. Thanks for all the info. I will be tossing what I have left out. I used it on one elevator end cover and thats it. Hopefully it holds up enough to get by with.

Carl,
I did what the plans said and started with a ?? strip of fibreglass and made each successive strip ?? wider. If I was doing it again, I would consider doing the lay-ups the other way around, with the widest strip first and make each successive strip narrower. I found that with each successive strip wider than the one below, air sometimes got trapped where the wider strip transitioned over the edge of the narrower one below. Subsequent sanding/contouring the lay-up sometimes broke through into these pockets of trapped air complicating the finishing process. I suspect that doing it the other way around could produce a stronger lay-up as there would be no risk of sanding through and weakening the widest lay-up.
Thoughts anyone???

Fin 9A Tip-up

Carl, in my previous life................I built a plastic airplane so I actually learned a few lessons in this area by trial and error Anyway, here is how I did it and it worked out quite nicely. Close the canopy and apply shipping tape across the joint separating the windscreen and slider. Add successive tape strips for and aft then mask off the rest of your plexi to keep any drips from finding your canopy. Mix your resin up and add a little colorant so you won't see the raw resin/glass from the inside. Measure out the length of glass needed to make your run. Draw this out on a thick piece of plastic with a sharpie. Cut your strips of glass and lay them out on the plastic. Apply moderate pressure as you lay each strip to get all the air bubbles out. I ended up laying 6 layers, little thin but I'll expound later. Now all you do is pick up the plastic and lay it, glass side down over the joint and peel the plastic "backing" off. Makes for a nice, non messy application. The packing tape serves two purposes: Keeps the resin from dripping inside and when the resin cures, you just pop the strip off for final shaping. Your strip should be a little wide when you pop it off so this leaves you with the opportunity to now go at those edges with a sanding block to get a nice smooth edge off the airplane without risking scratching your canopy. Peel the tape off and clean the glass very well and scuff up the canopy/windscreen where the strip will adhere and do the same with the strip. Mix you up some more resin and glue the strip onto the windscreen. As a final fix for mine, I mixed up flox and applied a thin layer to give the strip more rigidity then added a micro/peel ply to give me a good final surface to polish prior to painting. This sounds much more difficult than it really is and gives you a good finish.

Best of luck,

I used this for the micro/epoxy gap filler: (one ounce was WAY more than necessary) http://aircraftspruce.com/catalog/cmpages/epoxyPigments.php

I didn't use any pigment for the glass layups and have no regrets- after painting (primer gray, ala Chino Power Squadron colors!) it looks essentially black from the inside.

I followed Van's instructions and also referenced Dan C's site. I did all the glass layups in one session, but I think it took 2 or 3 mixes of epoxy. Maybe I'm not as quick as some, but it took me a while to get all the layers saturated and properly positioned even with the strips pre-cut. I used 10 or 12 layers, I think. When the batch I was using started to gel, I just mixed up another one and kept going. I applied the glass strips from narrowest to widest, not sure why the other way wouldn't work too.

Then it all comes down to sanding. My BEST advice is to make one of these:





It's a 5" by 2.5" piece of 6" PVC pipe (6.5" O.D.) with a piece of wood screwed to it. It made a fabulous sanding block (use long, even strokes!). A quarter sheet fits perfectly, wrapping around the sides where it can be held against the wood. With patience it can make a perfect contour. I also used 1" wide piece of PVC (no wood) around the sides where it transitions from curved to flat. An eighth sheet fits well on that.

Sorry I don't have any pictures of the process. Good luck!