fiberglassing

[The Hangar]

I'm planning on fiberglassing a pink foam build I'm working on and need to know if the stuff I'm looking at getting will work. Here's what I'm thinking:

Fiberglass cloth:
https://www.homedepot.com/p/3M-Bondo-8-sq-ft-Fiberglass-Cloth-20128/202077813

https://www.walmart.com/ip/Minwax-2...-Protective-Finishes-1-2-Pint-Gloss/840225387

Here's the video that states the difference between the zpoxy and polycrylic. I'm mainly going for a protective outer layer since I have enough strength already. I'm not overly worried about weight, but I hope to have to do only one coat.

Thanks!

 

[Quinnyperks]

The Bondo cloth is very heavy and coarse. I’d reccomend something finer.

 

[The Hangar]

Ok, that's what I had been told from Ryan as well. He suggested this stuff:
https://sigmfg.com/products/sig-glass-cloth?variant=427475763209

 

[Quinnyperks]

Def better.

 

[The Hangar]

Def better.

Do you think 1 coat will be strong enough?

 

[Quinnyperks]

Are you going for a skin or like structural?

 

[The Hangar]

Are you going for a skin or like structural?

It’ll just be a protective skin. However I think the fuse will need the support.

 

[Quinnyperks]

I’d then just do 2 layers on the body. What is the airplane?

 

[The Hangar]

I’d then just do 2 layers on the body. What is the airplane?

Ok. It’s a big ultra stick.

 

[Quinnyperks]

Ok. It’s a big ultra stick.

Cool!

 

[Bricks]

If you really wanted to make it nice and really easier then fiberglass sheet it with 1/32 balsa. If you are more worried about small dings and stuff cover it with 1.5 or 2 mm laminating film.

 

[Tench745]

For my latest build I used up the last of my roll of .5oz fiberglass cloth from Thayercraft. Usually do a coat of water based polyurethane to stick the glass down and when that dries, apply another coat of WBPU mixed with talc to make a light paste to fill the weave of the cloth.

It's still possible to dent the foam under glass this lightweight, but it definitely helps.

 

[speedbirdted]

I've tried using polycrilic on glass cloth and it's never really worked. The strength is pretty lacking, plus Polycrilic is pretty thin and doesn't soak into the glass weave terribly well. Polyester resin is my preferred material to use but it smells horribly and will destroy pink foam. I believe some epoxy resins are foam safe. Some say they all are but I tried to do something just like you're doing with pink foam and epoxy resin, and it destroyed the foam

You don't need heavy cloth. I have found that doing lots of layers of light cloth tends to turn out better than using heavier cloth, but my technique stems more from building things like cowlings which are self-supporting. With fuselage reinforcement you could probably get away still with light cloth, just not need as many layers.

 

[The Hangar]

If you really wanted to make it nice and really easier then fiberglass sheet it with 1/32 balsa. If you are more worried about small dings and stuff cover it with 1.5 or 2 mm laminating film.

Hmm, laminating film sounds interesting. Do you have a link to some?

 

[Tench745]

I've tried using polycrilic on glass cloth and it's never really worked. The strength is pretty lacking, plus Polycrilic is pretty thin and doesn't soak into the glass weave terribly well. Polyester resin is my preferred material to use but it smells horribly and will destroy pink foam. I believe some epoxy resins are foam safe. Some say they all are but I tried to do something just like you're doing with pink foam and epoxy resin, and it destroyed the foam

You don't need heavy cloth. I have found that doing lots of layers of light cloth tends to turn out better than using heavier cloth, but my technique stems more from building things like cowlings which are self-supporting. With fuselage reinforcement you could probably get away still with light cloth, just not need as many layers.

Yes, Polycrylic definitely is an aesthetic finish more than a structural one. Epoxies will give you a harder shell and fill the weave quicker. I believe epoxy is a bit heavier and definitely more expensive. Zpoxy, West Systems, and System 3 all make laminating epoxies that work for fiberglassing. Zpoxy has their finishing resin and it's available in as little as 4oz packages, West systems has their 105 resin and hardener of your choice, but the smallest quantity you can buy is a quart. System 3 has their general purpose epoxy which costs less per quart than West System, but the smalles size of resin you can buy is still a quart. I have heard that their T-88 epoxy can be warmed slightly which will thin it down enough to use for glass work, but I've never tried it.
That's very interesting that you had that happen; I have never had or heard of an epoxy that wasn't foam safe. Do you remember the brand?

 

[willsonman]

There are pros/cons to each "bonder" for this technique.

Polyester resins
First and foremost... I would NEVER use polyester resins of any kind in this hobby. The toxic effects are not worth the risk. It's not just during application but for the duration of the ENTIRE cure. There is a "pot" or working time for your respective hardner and the shorter that is yes, things will be sandable or able to be touched sooner but the cure is still around 24 hours. The chemical reaction is just manage on different time scales by varying the chemistry of the hardener. This is also true for...

Epoxy resins
They are hard, can be structural, foam-safe, not nearly as toxic. I use epoxy whenever I need strength and never when I don't.

Polyurethane
First and foremost... it is a safe material. It is water-soluble and therefore cleanup is a breeze. The other advantage is the cure time. You can haver dry to touch in as little as a minute if you speed things up with a hair dryer or heat gun. Mind you that will not be CURED fully for many hours but UV light like from sunshine does speed this up too. The main speed advantage here is that you can go from no covering to a covering WITH additional layers of poly to fill the glass weave in a very short amount of time. I recently did a wing with this and had the glass applied and two additional coats of poly applied and dried to the touch in about 2 hours of work. That would NEVER happen with epoxy or polyester resins. The other advantage is the softness. Because it is not structural you DO NOT want it hard. This way you can sand it smooth much faster, without gumming up your sanding agent in a more timely manner.

Being able to seal the glass entirely from pinholes is problematic with any medium as well as fully wetting them out. I highly recommend a plastic spreader used as a squeegee. the thing to note here is that proper layups take TIME. Never rush your layup as mistakes will cost you more time to fix after the initial layup. If you do it right the first time then you end up not having to redo anything.

Final thought. Go with polyurethane. By far the easiest approach to the first-time glasser and will teach you all of the same application principles for other mediums.

 

[Bricks]

Hmm, laminating film sounds interesting. Do you have a link to some?

What your looking for is Doculam here is a link but do some searching you can find it cheaper. We have talked about using this before.

https://www.ebay.com/itm/363088738323

 

[rockyboy]

What your looking for is Doculam here is a link but do some searching you can find it cheaper. We have talked about using this before.

https://www.ebay.com/itm/363088738323

There's a great thread on doculam covering over here....

https://forum.flitetest.com/index.php?threads/doculam-covering-pros-and-pitfalls.61962/

 

[Bricks]

Why and try to scare people about polyesters resins they are very use full in this hobby some ventilation and common sense goes along ways. I have used a lot of Polyester Resins in the hobby and my work. CA fumes are just as bad if not worse do we not use them, how about spray paint in cans those too they could all hurt you in some way or another..... A bit of Common sense when using these products goes along ways...

 

[The Hangar]

Thanks for all the input guys - lots of great info! I got fiberglass today, and I'll be using polyurethane like @willsonman recommended. I have the oil-based kind - I assume that'll work just as well, right? One benefit is that it is waterproof.