spaceworm

Which polyurethane finishes are glow fuel proof,. Please note Minwax, Varthane, Zar and Rustoleum paints in particular. No need to include catalyzed or multi-component specialty type finishes.

Thank you very much.
Sincerely, Richard

1QwkSport2.5r

Regular oil based polyurethane is pretty much fuel proof. The water based stuff does get softened by the alcohol, but it usually hardens back up after its dry for awhile. I have read that guys have used Minwax with good results. As far as paint goes - the oil based paints and automotive type paints are usually fuel resistant as well. I cannot speak for lacquer in any medium as I have never used it. I do believe many car paints are lacquer based and seem to hold up, so perhaps clear lacquer is resistant as well.

blw

My Feedback: (3)

I'm thinking of going back to fuel proof dope.

spaceworm

Since butyrate is used on FS gas AC, I am thinking it is ok for gas RC as well as glow? Do you have a good source?

Thanks

Sport_Pilot

Polyurethane is only fuel proof if you wipe it down right away. For better fuel proof paint go to the auto parts store and buy the Plastikote acrylic lacquer touch up paints. Make sure it is lacquer it should say on the back if not on the front. They make enamels as well but they are not fuel proof.

1QwkSport2.5r

I've never had a problem with oil based polyurethane staining from fuel providing it's cured and several coats applied. Water based polyurethane on the other hand will need to be wiped down quickly so it doesn't soften the finish and stain it. Epoxy is pretty tough against fuel too, but raw fuel will soften it a bit as well if not wiped off quickly. Exhaust oil doesn't do any damage - only raw fuel can be problematic.

Sport_Pilot

I used oil based poly on my field box which holds a gallon jug of fuel, and the paint under and around the jug did not last long. The rest was OK as long as I wiped it off right away. Most paints will be ruined with even a brief exposure. Acrylic lacquer is good to about 20% nitro.

1QwkSport2.5r

Are you talking about clear polyurethane or polyurethane paint?

Sport_Pilot

Clear.

TomCrump

Most paints, fuel proof dope included, will not hold up to being saturated with glow fuel, such as around a fuel jug, or in an engine compartment.. Polyurethane holds up well to normal usage on glow and gas powered models.

Polycryllic is not a suitable finish for glow.

Sport_Pilot

I suppose so, but pretty sure that an epoxy varnish is fuel proof no matter how long the fuel stands. The lacquer may be the same but sure seems it came off easily. Maybe I mistook polycryllic for polyurethane, They do advertise it as equal.

TomCrump

[QUOTE=Sport_Pilot;12259690. Maybe I mistook polycryllic for polyurethane, They do advertise it as equal.[/QUOTE]

For our purposes, they are not equal.

I do use both polyurethane, and polycryllic, for glassing, though.

1QwkSport2.5r

FWIW, I do hardwood floors by trade. I've worked with a plethora of finishes over the years (almost 17 now) and I can say with the utmost certainty that Minwax Polycrylic waterbased finish is absolute garbage. Typical oil based polyurethane is quite resistant to fuel, but waterborne finishes aren't as much. Most waterborne finishes that are single component (no catalyst) tend to be more susceptible to staining and softening when exposed to methanol whereas two component (isocyanite catalyst) finishes tend to be more resistant to methanol. However there are limits to what a finish can handle. Epoxy is fairly resistant to fuel, but if left for extended periods of time, the epoxy can soften and cloud up some after wiping it off. It's usually best regardless of finish to wipe it off quickly.

aspeed

I have heard rumours that good quality hardware store enamels can be fuelproof with the addition of an automotive hardener. Not sure about the clear polyurethanes. I try to keep away from clears on planes because of weight. Experimentation is the key I guess. Maybe someone will chime in. Airports may be able to source butyrate dope. I am still collecting different automotive two part colours for my stuff.

Sport_Pilot

If you paint a lot of models you can by buterate dope from most aircraft suppliers such as Aircraft Spruce and Speciality.

http://www.aircraftspruce.com/menus/...hcoatings.html

They sell at least one other brand, Certified Coatings.

spaceworm

Can water-based clear polyurethane or polycryllic be used for filler coats after heat shrinking polyester fabric covering (like Koverall)
? Is satin, or gloss better for this? Any restrictions for the top coat paints after using either of these?

Thank you very much.

TomCrump

I'm a Solartex guy, so I have no direct experience with Koverall. I have read that some do use Polycryllic to seal the weave.

aspeed: I have used hardeners in Rustoleum, and in Minwax Polyurethane. They work well, as they increase gloss and decrease drying time, along with increasing chemical resistancce.

The hardeners contain some components that may be best left to professionals, though. I had it explained to me as beeing similar to spraying CA. Proper breathing equipment must be used.

Sport_Pilot

If using polyester fabric, I would suggest using the polyester aircraft paints such as sold by Spruce Speciality.

TomCrump

If you are using polycryllic to seal the weave, most paints will are compatible. The builder must decide if aircraft certified paints, or automotive finishes, are worth the $$$ on a model.

1QwkSport2.5r

What catalyst (hardener) did you use in the Minwax product? I didn't know they sold a catalyst for their polyurethane. In fact, I've never seen a catalyst used in an oil modified urethane (oil based polyurethane). Conversion varnish (Swedish finish) and commercial waterbornes use a catalyst typically.

Sport_Pilot

Those dopes are cheaper than say Sig or Brodak dope. A quart of clear dope from Broadak is $33 bucks. Sig Supercoat is $25. About $19 from Aircraft Spruce. I don't think there is a premium for the aircraft paints, it is about the same or even less than most automotive paints. Their price for acrylic lacquer clear is $53 dollars and automotive is about $100. Certified dope is a brand name. I do not think it is actually certified.

DaveP

I've found two water-based polyurethanes that are fuelproof, as near as I can tell.

15 years ago or so I built a universal engine test stand of red oak and finished it with water-based Varathane Diamond Floor Finish (originally owned by Flecto, now by Rustoleum) I had left over from building cabinets and it has been totally impervious to glow fuels, up to the 15% I've used on it. I also use it in engine compartments over epoxy and 2 coats of color Rustoleum to protect the Rustoleum, which can take a loooong time to cure, if ever.

I've also had good luck with Cabot Water-Borne Polyurethane, but haven't as much experience as with the Varathane.

As noted previously, Minwax Polycrylic has no place near a glow engine. As the name suggests, it is not a poluyrethane.

-Dave Plumpe

TomCrump

I used an automotive hardener. It wasn't a product marketed by Minwax.

1QwkSport2.5r

Minwax Polycrylic is AFAIK a Polyurethane Acrylic hybrid if you will. It has both resins in it I believe. One of the commercial floor finishes my company sells is based on the same resin technology, but incorporates an Isocyanite catalyst/crosslinker/hardener. It's one of the hardest floor finishes on the market.

1QwkSport2.5r

Yikes... That's risky business adding a crosslinker to a finish not designed for it. I'd not recommend anyone try doing that for fear of a possible chemical reaction or undesirable finish behavior (peeling, poor leveling, etc.).

We haven't used it in several years, but Swedish finish (conversion varnish) might be reasonable alternative to typical aircraft dopes. It is harder than any urethane and had crazy chemical and abrasion resistance, but they're alcohol based.

Maybe be if I get around to it, I'll use some of my floor finishes on a board and soak it with finish and see what happens.

My test stand is made from Wenge, Cherry, White oak, and birch and is sealed with 3 coats of Epoxy finishing resin. Once cured, fuel doesn't affect it. Epoxy would be the only finish I'd use with fiber cloth. If I'm using cloth, I want the finish to penetrate the substrate and be strong so as to create a good bond.