Balsa model finishing

Paint with whatever you want. Dope, spray paint, craft paint, etc. Let sit a couple days to dry well, then put a coat or two of this over top and fuelproof. Does not yellow either. Or can spray directly over the wood if you like it as well.
https://www.homedepot.com/p/Minwax-11-5-oz-Gloss-Fast-Drying-Polyurethane-Aerosol-Spray-33050/100376199

Forgot to add that this is what I use myself. Although, it is now hard to find up here. I have used on 20% nitro with no effect.

If you really insist on Dope finishes then Brodak or Aircraft Spruce can help you out. Brodak is pre-thinned (and I believe is a Randolph product), Aircraft spruce is going to offer Randolph Dope which will need thinned to your needs with the correct thinner.

Since you have a dope base on care will be needed when switching between products as dope does not always play nice with other paints. Fully dry dope will take enamel or polyurethane finishes without problems. I know enamel finishes such as rustoleum are not proof against strong solvents so over coating with something that can soften the underlying dope will cause immediate coating failure.

I do not know how polyurethane resists different solvents to give a solid answer.

Naturally the devil is in the details, so to speak, and the layer cake of finishes can prove problematic at times. I know the rustoleum will be fuel resistant all on its own with a 2 week cure time, and will cover dope that is done gassing off just fine. The polyurethane will be more fuel proof with an overnight cure time, and will also cover dope that is done gassing off just fine.

I do not know how wood/dope/rustoleum/polyurethane as a layer cake will perform

Wood/rustoleum/polyurethane is a safe layer cake as long as the rustoleum has had 2 weeks to cure. (I am unsure about shorter cure times) Enamel and polyurethane can be layered over each other without significant concerns beyond cure time too.

Phil

I also have run this dilemma recently when fuel-proofing my SIG Wonder...because unable to find any PUR-based varnish proposed by many CEF friends here, I have finally opted for a fuel-proof colorless varnish spray sold in car parts shops to cover the aluminum ring of wheels. I tested whether this resists nitro fuel too -it certainly does gasoline - and found it OK.

I made sure that the areas inside the fuselage exposed to occassional fuel spill from the tank, and the fuselage exterior near the engine firewall both were sprayed in at least 3 layers before I covered the plane with Oracover.

My initial experience near the engine bay area that typically soaks in castor the quickest are very positive: no signs of custor infusion into balsa.

Lets remember our audience as we recommend things

This young man by definition is on a strict budget

So I offer two schools of thought on initial balsa airplane building and finishing

1. Accept that it is not likely to avoid crash damage and do the very minimum to fuel proof...more on this in a bit

2. Start with first build and try to learn proper finishing techniques but very basic at first, and each subsequent build add more to your skill set. Almost always requires a lot of different techniques and products

Every body wants a pretty model....but the hours spent and the products consumed are wasted if the first grand figure Nine is done perfectly....

With that in mind, I recommend building a lot of the simple models two or three at a time...one beater...one with some smoothing and simple single color, and if inclined, one with a lot of prep, sanding, filling, and multi color

There are 100s of products that work but part of the trick is knowing which dissimilar products can work together and more importantly what ones absolutely do NOT work together....like Nitrate Dope can NEVER go over Butyrate dope...period

I offer not specific advice

Search here on CEF for Ken Cooks excellent advice
Search the building and finishing section of RG Groups, Stunt Hanger, and Stuka Stunt

Hint... fast easy and cheap... Walmart rustoleum spray can paints are real fuel proof if let dry for 10 to 14 days

Do NOT try to put on coat after coat trying o hide the wood grain...just makes a real heavy airplane

Hint...rustoleum Clears and Metallic are NOT AT ALL FUEL PROOF! In fact Black is not very good either but I do use it under a more fuel proof clear

fredvon4 wrote:...
Do NOT try to put on coat after coat trying o hide the wood grain...just makes a real heavy airplane
...

Oh my how true this is!

Ideally there should be only one coat of paint on the plane for 1/2A This is slightly impractical in practice but is best for weight.

Feel free to test the paint against fuel. Take a wood sample (skewer, stick, or scrap wood) paint it with the desired product(s) and allow to cure fully. Next apply fuel to the wood with a paper towel and plastic bag. Allow the fuel wet paper towel sit on the paint for an hour. Lightly rub the wet paper towel on the paint and then examine both the wood and the paper. Some color transfer is OK as is color change of the paint (the color usually returns to normal overnight in my testing). Wrinkles, peeling or other outright coating failure results are not allowed.

Don't forget the exhaust is in some ways harder on paint than the raw fuel. Clean up with automotive window washer fluid, or at least wipe down well with a clean dry rag.

Phil

Nice idea with the windshield cleaner for auto. Phil . here's a link to Sig Co. Dstradt.. http://www.sigmfg.com/cgi-bin/dpsmart.exe/IndexBuidlingMaterialsEquipmentF.html?E+Sig The Aero Dope is going to be hard to find and bee best to stay with something you can get . How is the model coming along and are U going to Tissue it ? Eric

Looking a bit closer at Dstradt's Free flight model my Figure Nine early arrival comment is not an issue

Looks like I can not recommend Lustercote any more...I have been watching Tower and TopFlite for about a year and now the only color is Jet White and all others are "unavailable"

That leaves SigMfg or Brodak for clear dopes in small qtys

That AeroGloss...even as balsa filler version is itself pretty fuel proof

for transparent color you could add a few drops of food color or Rit dye

Or lay out and dope down a layer of colored tissue

This model was finished with the same balsa filler you are using, that stuffs the best. It got 2 coats of DC540 primer (also the best) from napa, sanded almost completely off, and one coat of duplicolor white enamel. Reasonably fuel proof, cheap, and available.

https://outerzone.co.uk/more_pics.asp?ID=4380

Yes.. you need to keep the paint-weight down.. and paint can be heavy. I always kept a trigger-spray bottle of windshield-washer fluid (cheap/summer formula) in my field-box.. along with some rags and a remnant-roll of paper-towels. After you're done flying the model.. throw a cloth-rag over the engine.. and "spritz" the airframe with the washer-fluid.. and wipe it down. The washer-fluid will dilute the oil-residue.. and make it easier to wipe-off. Take your time.. and clean the model well. Doing this "will" preserve the finish "much longer" than if you don't. Make it part of your routine when leaving the field to go home. The engine can remain "oily". You don't want the spray-cleaner to contact the engine.. because any iron parts could "rust" if the oil is washed-off. You can and should "oil your engine" with air-tool oil before putting it away for the season.

Jim, I haven't tried the DC enamel yet. Do you find that it gases off and cures much(or any) sooner than Rustoleum... like if you wanted to spray some clear Lustrekote over the front end? I know DC's lacquer dries fast, a lot like dope.

Do you ever spray the enamel colors over clear butyrate on the solid wood parts, eg. a fuselage that's been sealed or silkspanned with dope. I know, mixing chemicals is not a good policy, but I'm just curious and hardheaded.

RknRusty wrote:Jim, I haven't tried the DC enamel yet. Do you find that it gases off and cures much(or any) sooner than Rustoleum... like if you wanted to spray some clear Lustrekote over the front end? I know DC's lacquer dries fast, a lot like dope.

Do you ever spray the enamel colors over clear butyrate on the solid wood parts, eg. a fuselage that's been sealed or silkspanned with dope. I know, mixing chemicals is not a good policy, but I'm just curious and hardheaded.

Rusty,

It takes a week to fully cure. The can says to apply additional coats within 2 hours or wait the seven days. I have masked and applied a second color after 24 hours but you must apply several (4-5) "mist coats" about 10-15 minutes apart to get full coverage and then lay a "wet" coat over that.
I have applied over butyrate no problem.

Make sure and test spray on a piece of cardboard when you start a new can. I've had two with defective nozzles that splattered warts all over the place. Other than that it's a great product, the only stuff I use.

Jim

The Balsa Filler Coat is dope with talcum powder.