Tried glassing my first aircraft. Did NOT go as expected. Trying to figure out what went wrong.

[Ducky84]

So I wanted to fiberglass an Explorer adding 1oz glass to the high impact areas to add some strength to the wing.

I did some research online, and picked up some Epoxy, and Fiberglass from my local hobby store.

When I went to apply the epoxy is where things went wrong. From the videos I've found online, some folks made it seem like the viscosity of the epoxy solution they were using was very thin. In one video I saw someone pour it over their fiberglass on the wing.

Well that was not the case for me. When I mixed my epoxy solution, it was very thick. When I applied my brush to the fiberglass, everything started to stick and shift around, parts of the glass started freying. It was very hard to spread and I ended up putting way more on than I anticipated, and in some areas it didn't soak in. I got lots of bubbling and it just didn't go as expected.

I suspect the epoxy solution I'm using is where the problem lies, but I don't know for sure.

This is the epoxy I used: https://www.hobbytown.com/bob-smith...30-minute-epoxy-9oz-bsi206/p-xtychdgawqsbg4yz

I'm sure I'm doing something stupid, but help me out here. What did I do wrong?

 

[FlamingRCAirplanes]

Sounds like it was dried up. Try going to Hobby Lobby and picking up some 5 minute gorilla glue epoxy.

 

[cyclone3350]

I am guessing that U R were given the wrong epoxy. This is what I use. Note that is is labeled Finish Cure. This is usually mixes to a thin solution. Any structural epoxy will be too thick. https://www.amazon.com/dp/B001NI8MP8/?tag=lstir-20

 

[Ducky84]

I am guessing that U R were given the wrong epoxy. This is what I use. Note that is is labeled Finish Cure. This is usually mixes to a thin solution. Any structural epoxy will be too thick. https://www.amazon.com/dp/B001NI8MP8/?tag=lstir-20

Maybe that's where I went wrong. So theres a difference between "slow cure" and "finish cure"? Is this stuff you used a lot thinner and easier to spread?

My local hobby shop has this stuff you linked so I can pick that up.

 

[cyclone3350]

Maybe that's where I went wrong. So theres a difference between "slow cure" and "finish cure"? Is this stuff you used a lot thinner and easier to spread?

My local hobby shop has this stuff you linked so I can pick that up.

Yes. Finish Cure is strictly for fiber glassing or sealing wood for painting. Should work out.

 

[Merv]

I use a clear, oil based, polyurethane, the stuff used for wood. Much easier to use than epoxy.

 

[Ducky84]

I use a clear, oil based, polyurethane, the stuff used for wood. Much easier to use than epoxy.

I have some of that lying around, but my understanding is the epoxy would provide more strength against mild incidents, scuffs, bumps, things like that.

Is that not the case?

 

[leaded50]

you forgot to check viscosity and if necessary thin it. Can be done by heat, specialepoxy thinner, paint/ lacquer thinners, denatured alcohol, or acetone.

 

[PsyBorg]

Probably shouldn't be using resin based fiber glassing on foam planes. That's more for marines work and tends to be super heavy. Water based polyurethane over fiberglass mat is much better. You can thin it to meet your needs. Its much lighter and then for finishing you can do the WBPU + baby powder trick.

 

[Merv]

....my understanding is the epoxy would provide more strength against mild incidents, scuffs, bumps, things like that.....

Epoxy is likely to be stronger, but is marginally stronger. Fiberglass and polyurethane is plenty strong.

The majority of the strength (my guess 80%) comes from the fiberglass. Even if the epoxy is twice as strong, it only makes up maybe 20% of the total. So you’re taking the difference of 100% for epoxy and fiberglass vs 90% for polyurethane and fiberglass.

 

[Merv]

I have some of that lying around....

If you have some polyurethane on had. Fiberglass & poly a small scrap. Test the strength for yourself.

 

[Piotrsko]

And you're not using fiberglass in compression, is doesn't work well that way. Basically all the resin does is act like a glue to hold the fibers attached and rigidly in place so it really doesn't matter what the glue is. As I have said before, I like acrylic cloth covered in titebond.

 

[tamuct01]

I'm looking to glass an FT Sea Angel, and from the videos I've been watching, the epoxy should be thinned with Denatured Alcohol 1:1 with the resin to make it near the consistency of water. Sounds like you may have skipped this step.

 

[Ducky84]

Thanks for the feedback guys, I really appreciate it. I've learned some things and I'm going to try some new things.

On the bright side, while my first glassing job didn't go as expected, the wing is still pretty solid. I should be able to still fly with it.

 

[Merv]

I agree with @Piotrsko, normal wood glue and white glue (Titebond & Elmer's) works well for fiberglass.
I have also used hot glue on small projects.

 

[Tench745]

You were using 30-minute epoxy. This is intended to be used as a glue, not a finish. You want a finishing epoxy. If you're looking at hobby specific things, Bob Smith has their 20minute "Finish Cure" epoxy, and ZAP has their Zpoxy finishing resin. These are much thinner epoxies and are made to wet-out fiberglass cloth.
If you're doing a big job you could get into the marine brand epoxies, West System is the big name, but Total Boat has good epoxies as well.
I have not used any of the new resins they sell for various craft projects now, so I can't speak to that.

If you decide to use polyester resin, be very careful. It has strong odors, can cause allergic reactions in many people. But maybe more importantly, it will melt exposed foam.

 

[foamboardflyer]

If you decide to use polyester resin, be very careful. It has strong odors, can cause allergic reactions in many people. But maybe more importantly, it will melt exposed foam.

I agree, your model that you spent 8 hours on is more important than you going into anaphylactic shock

 

[Tench745]

I agree, your model that you spent 8 hours on is more important than you going into anaphylactic shock

Safety third!
I guess I should have said "more to the point" or "more on topic." I haven't seen or heard of respiratory reactions to polyester resins, though I'm sure it happens. Skin irritation and rashes tend to dominate.

On that note, epoxy can also cause both respiratory and topical allergic reactions. It's a little insidious, because epoxy has very little in the way of smell and doesn't usually cause any reaction on the skin But, it builds up in your system, and given enough exposure anyone will become sensitive or allergic to it. So be safe, work in well ventilated areas, and wear gloves!