Brushing Urethane

Does anyone know of a good fuel proof brushable urethane? I tried Minwax, and its NOT fuel proof.

Thanks,

Randy Ryan <><
AMA 8500
SAM 36
BO all my own M's

Randy,
Nelson Hobbies markets polyurethane paints that are fuel proof if you use their cross-linker. Instructions include brushing with a foam brush. Check the info at:
http://www.nelsonhobby.com/paint.html

Steve

I imagine you could brush a catalyzed polyurethane like Omni. It would be interesting.

I have brushed catalyzed Urethane clear,, (automotive) I depends on what you are after, it would be difficult to get a really good finish with a brushed topcoat. the resins and reducers are formulated to flow out when sprayed. Laquer is such a low percentage of solids that when it dries a good deal fo the brushstrokes flatten out. Urethane is much higher solids so it would tend more towards what you put on is what y0ou end up with as for texture. and then the thought of polishing it after that, sanding all the brush strokes, ,nah, dont think I wanna try that one.

>Does anyone know of a good fuel proof brushable urethane? I
>tried Minwax, and its NOT fuel proof.
>
>Thanks,
>
>Randy Ryan <><


I've always found polyurethane to be quite fuel proof; however, it yellows. Are you sure you didn't try polycrylic, which is not fuel proof?

Paul

The Minwax gloss polyurethane applied to the white portions of this Zilch was not affected by 10% nitro fuel.

A month-or-so after application it did begin to "yellow" a bit, but since the poor thing bit the asphalt a short while later, I never had a chance to see further results.

Mike Keville

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Attachment #1, (jpg file)

Thanks so far guys,

Here's the issue, I am building some Free Flights and I will be running 30-40% nitro. I've used Minwax and I love the way you can brush it out forever and get a pretty fair finish. However finish is not the goal here, weight and fuel proofing are, finish is way down on the list of qualities.

I may have another look at the Nelson materials, if they will brush out well, that may be what I need.

Randy Ryan <><
AMA 8500
SAM 36
BO all my own M's

I will second this statement the Minwax gloss polyurethane brushed or sprayed from spray can is not fuel proof – even 5% nitro will destroy the finish.

Marek

Randy,
I tried 2 or 3 different urethanes out of a can, some of which were claimed to be fuel resistant. I tested them on propellers and the finish always got gummy. I suppose if you were a pro-stunter and never dripped fuel and kept your hands clean...heck, if you just hung the model from the ceiling, these brands would work fine. For props I switched to KlassKote. Not sure what the FF guys are using on covered structures.

Good Luck!

Dave Hull
LA_Flyer

Doug Ellis used to use Flecto Varathane, I used it on my C/L Biplane, and it was fuelproof...

I used Varathane 30 years ago or so. I guess it still exists. It takes awhile to dry, but it's fuel proof.

Howard Rush
Bellevue, WA

>......Minwax gloss polyurethane brushed or sprayed from spray can is not fuel proof – even 5% nitro will destroy the finish.
>
>Marek
============================================================

Wrong! (See post #5.)

Mike Keville

Mike,
I do not care what post # 5 said. I tried Minwax gloss polyurethane brushed and Minwax gloss polyurethane from spray can and based on my experience I am providing this advise to other people: don’t make the same mistake I did – if you do – then make sure you have some stripper on hand or sand paper later on to remove the clear coat because that what I have to do to fix the problem. I am using 5% to 7% nitro fuel, I am very careful when fueling but even exhaust from my tunepipe is destroying the finish.

Marek

Randy,

If your primary interest is fuel proofing, you might consider an epoxy based paint instead, like KlassKote. You could brush that on and it's pretty fuel resistent.

All of the 2 part marine polyu paints have brushing reducer available--they brush well--a good brush job is hard to tell from a sprayed app.

Try Interlux or Awlgrip.

The brushing reducer is setup to allow the paint to flow without flashing off.

C

>Does anyone know of a good fuel proof brushable urethane? I
>tried Minwax, and its NOT fuel proof.
>
>Thanks,
>
>Randy Ryan <><
>AMA 8500
>SAM 36
>BO all my own M's

Hi Randy,

I know from spraying all types of polyurethanes over the years both on full-scale airplanes and C/L Stunt models that to get a truly fuel-proof (not just fuel-resistant) finish you have to use a fully cross-linked polyurethane or a 1:1 ratio epoxy. Anything that is a one-part (not catalyzed) paint will not be fuel-proof or even very fuel-resistant.

On full-scale airplanes we have the problem of spilling gasoline occasionally on the finish and the dye in the fuel will stain all non cross-linked finishes.

The reason we don't use epoxies to finish full-scale airplanes is that while epoxies are tough and chemical resistant and can have a good gloss they do not stand up to weathering very well, whereas fully cross-linked polyurethanes do.

While I realize that you want to brush your finishes and this subject has been covered before, the health hazards of polyurethanes are mainly in atomizing the ready-to-spray paint. The really hazardous part is the catalyst which contains very toxic isocyanate esters and can lead to super serious health problems which can't be fixed. Health problems can also be caused by skin contact with the catalyzed paint or with just the catalyst. When I mix or spray polyurethanes I use vinyl gloves (not latex), a full body spray suit, eye protection, and a respirator - for models or full-scale airplanes.

Epoxies don't have the isocyanate esters, but the problem with spraying epoxy paints is that the particles lodge in your lungs where they cause "mechanical pneumonia" and can't be removed. Also, as is now pretty well known, some people tend to build up an allergic reaction to epoxies which can be pretty serious.

This is probably information that you were already aware of but it is so serious that it can't hurt to post it again.

Well, I've purchased soem Nelson gloss clear and crosslinker, I'll let you all know how it works out.

Randy Ryan <><
AMA 8500
SAM 36
BO all my own M's

While I've had no problem with Minwax gloss polyurethane and 10% fuel (though apparently Marek's experience wasn't quite so positive), perhaps some would be interested in an alternate clear coat: "Fullerplast"...a two-part finish for doped tissue and other coverings sometimes referred to as Fuller Plast.

An excellent product, Fullerplast (registered Trademark) is ideal for Old Time Stunt, where a delightful fuelproof---as opposed to a "20 point"---finish is the goal. I've used it successfully on numerous Free Flights with 30% nitro and no adverse effects. It's tough, fuel-resistant, quite glossy....and very expensive.

To my knowledge, there is but one current source: Van-Dee Decorating Center, 205 S. Federal Hwy., Stuart FL 33994, phone 800-749-8263. The product is featured on their web site (www.van-dee.com) as "Fullerplast Varnish" and is available in gloss or satin. The price may have changed by now, but at any rate be prepared for a significant weight reduction to your wallet.

Mike Keville