Fiberglass Resin Without the Fiberglass?

[FoxtrotHotel]

I'm preparing to seal up the exterior hull for a wooden kit that I'm building as an RC model.

 

I've heard some people coat the exterior hull in Bondo's fiberglass resin, which despite the name isn't resin mixed with fiberglass, but resin applied to a fiberglass mat that's then afixed to a surface. I bought some, but the fiberglass mat is 0.2mm thick, which is far too bulky. Does anyone just apply the resin without the fiberglass? My hull is only about 16 inches long, so it's fairly small, and probably doesn't need the extra reinforcement that the fiberglass provides. Is the plain resin too brittle and weak or will it work just fine without the fiberglass?

[CDW]

I've done it successfully many times in the past using epoxy resin. Not sure of any reason a polyester resin would not also serve the purpose of sealing the hull.

[lmagna]

I have done it also. CDW is right that using epoxy or polyester is about the same over time. Some people say that you have to use the cloth for strength and to prevent the finish, (fiberglass) from cracking but I have never had the finish fail. It is pretty much like any other hull coating, you can even add color to it if you want.

Thee only time I ever took any damage to a fiberglass covered hull, (With or without cloth) was when I played ice breaker one day. Ice is HARD and sharp. 

I don't know about epoxy but you can thin down polyester resin with Acetone, (Use care) and it will soak into the wood pretty well making the hull much more resistant and strong.

[CDW]

31 minutes ago, lmagna said:

I don't know about epoxy but you can thin down polyester resin with Acetone, (Use care) and it will soak into the wood pretty well making the hull much more resistant and strong.

For reducing epoxy resin, I use denatured alcohol. 

[Bob Cleek]

There is an excellent epoxy product specifically formulated for sealing wood. It penetrates the wood surface and when it cures the wood is fully sealed and hardened by the flexible epoxy that has soaked into it. I would use it on any model hull I intended to put into the water. It's extensively used by the professional wooden boat trade. It was originally invented for use in restoring rotted and damaged architectural details on old Victorian "gingerbread" buildings and later as a wood preservative for use in the tropics. From there, it found its way into the wooden boat trade. It's been around now going on 50 years. It can be painted over without further preparation, unlike many other resin coatings which develop an "amine blush" that must be removed before further painting.

 

Smith's "Clear Penetrating Epoxy Sealer (tm)" or just "CPES(tm)."

 

http://www.smithandcompany.org/

[shipman]

'denatured alcohol'

What is this stuff called in the UK and where to buy it?

[bruce d]

27 minutes ago, shipman said:

'denatured alcohol'

What is this stuff called in the UK and where to buy it?

We know it as 'methylated spirit'.

HTH

Bruce

Edited November 28, 2019 by bruce d
finger trouble

[No Idea]

I use 49g fibre cloth and finishing epoxy resin. The cloth really does make all the difference for a smooth long lasting finish. It takes 3 coats of resin to get an immaculate finish. The first just coats the hull. The second is used to apply the cloth and the third fills the weave of the cloth. Here’s a few pictures of what I’m working on at the moment. It hasn’t had its last coat yet but it’s coming out ok. The best results I’ve had is applying the resin using a 1” roller and using thin coats.  The last two pictures are of the second coat dried and the excess cloth removed. I hope this helps you

[No Idea]

11 minutes ago, bruce d said:

We know it as 'methylated spirit'.

HTH

Bruce

It’s called IPA in the UK and is very cheap on eBay. 

[No Idea]

Just realised I should have included a picture of the cloth with the resin applied before it was trimmed otherwise it doesn’t make sense - sorry. The resin has just been applied and is wet. 

[bruce d]

28 minutes ago, No Idea said:

It’s called IPA in the UK

Pretty sure IPA is not the one. IPA = rubbing alcohol, meths is a different beast and I believe it is the 'denatured' product. I will be interested if it turns out to be IPA.

 

Edited November 28, 2019 by bruce d

[No Idea]

Your right it is rubbing alcohol and this is what I use to thin my epoxy resin and also clean my tools with. I’ve been using it for years but anything more than a 10% dilution just doesn’t seem to work well for me. I buy a litre of IPA which is 99% pure if that’s the correct term for about £5

[vaddoc]

Small tip: vinegar removes uncured epoxy. Best thing to clean your hands.

[bruce d]

14 minutes ago, vaddoc said:

Small tip: vinegar removes uncured epoxy. Best thing to clean your hands.

!!!!!!!

I learn something every day on this forum.

[shipman]

Ah! Meths. Thanks for that.

And vinegar for cleaning epoxy off your hands. Is that the 'non-brewed 'condiment' variety? Or the posh wine vinegar?

Either Meths or vinegar on the fingers will stop your kids picking their noses!

[vaddoc]

Indeed, epoxy is alkaline and vinegar being acid destroys it immediately if uncured. 

But: Slowly (or less slowly) hypersensitivity will settle with epoxy so best to always wear gloves

 

 

[Mike Conway]

Be  careful using epoxy resin.  Use gloves.  You can become sensitized to epoxy resin -- maybe not the first time or two but after repeated exposure.   Then you can do what I did and break out in giant hives as big as dinner plates.   I don't think breathing it is a hazard -- or not that I've ever heard and it doesn't bother me.

[Mike Conway]

The term "fiberglass".  That's the name Owens Corning gave it -  they made the glass reinforcing.  In most countries it's called GRP -- glass reinforced plastic.  Polyester resin is the plastic part and the glass is the reinforcing.  Like steel rebar in concrete.  And yes, you can set glass cloth in epoxy resin but that's not the same as "fiberglass' -- as the term is used in the U.S.  Also polyester resin normally doesn't sand, only specially waxed polyester resins do.  Stick with epoxy is my recommendation.  And do what others have already done like the beautiful wood tug hull that was shown several entries back and that was done in epoxy and very light weight cloth.  Epoxy is also resistant to water vapor.  That's not the case with fiberglass (which is polyester resin and glass.)