You got dope

You could've asked that question 20 years ago and probably received the same response. Since 1985-86 there's been a serious reduction in high voc paints. They've been phased out because these products dry by solvent evaporation. Prior to Sig no longer providing products, I had to pay $40 for a qt delivered to my door. Absolutely ridiculous. the 4 oz. jars were nearing $12 without shipping. It's not cost effective to use the products. Even if you go to a major supplier which I have done, a gallon of comparable thinner was over $100.

If fuel resistance and color are your concerns, it's much easier to use two part auto paint. Nowadays, you can even purchase 2 parts auto urethane in a spray can. It has a plunger you pop on the bottom, shake and spray. A can costs $24 and it's 100% fuel proof and will stand up years ahead of dope.

I understand what you mean, Ken. For example, turpentine or ordinary paint thinner was a petroleum product for your oil based paints sold in hardware stores. Then about 15 years ago, they started substituting a plant based product. It would only stay good for less that 6 months. If you didn't use it by then, it congealed and had to be tossed out. Standard paint thinner, I could keep the can for years, was still good. However, with each passing year, it is getting harder to find. I am on my last can.

George you want have problem find it here in US https://www.google.com/search?q=Standard+paint+thinner&sourceid=chrome&ie=UTF-8  Still demands a good amount of $$$ I need some poly spar and that crap has gone through the ceiling lately ! https://www.google.com/search?sca_esv=569833926&sxsrf=AM9HkKn9x8SW_T3f2cR1BohdjRKsqBWJUQ:1696155948267&q=spar+urethane+vs+nitromethane&tbm=shop&source=lnms&sa=X&ved=2ahUKEwiAuZ6m0dSBAxWml2oFHeVfDD8Q0pQJegQIDhAB&biw=1792&bih=921&dpr=0.94

Ken Cook wrote:.................
            If fuel resistance and color are your concerns, it's much easier to use two part auto paint. Nowadays, you can even purchase 2 parts auto urethane in a spray can. It has a plunger you pop on the bottom, shake and spray. A can costs $24 and it's 100% fuel proof and will stand up years ahead of dope.

How does it compare weight wise and does it shrink covering over the open areas?

I have just a little Sig Lite Coat left so haven’t tried this experiment yet…. I’ve thought about using thinned down Duco cement as a dope just for try…. It thins easily in acetone and maybe a few drops of castor oil could be added to keep the acetone from gassing off so fast….Might be OK on sheet surfaces on small models…..Could probably get two or three ounces from the one oz tube of glue….. It may or may not have the solids content that dope has to provide strength….Just a thought…

Used as a glue works great on balsa…. In a way kind of like the old Ambroid cements, Double gluing the joint works best…. Joints need to be tight, It’s not a good gap filler…. I found out it about doing a few indoor free flight models….. Besides being very light, you can flood a joint with acetone to get it apart, Very handy in some situations to replace or reposition a part…..I’ve since used it in a few places on gas power in areas I may want to take apart….So far so good with fuel and oil resistance

Virtually no one in here covers open bays with silkspan on 1/2A's that I've seen. Doing so on a 1/2A is a waste of time and materials. Were not talking tissue. It's not needed, it rips constantly and it's a virtual maintenance nightmare. If one chooses to do so. I would highly recommend applying silkspan wet using thinned white glue or Mod Podge. After it dries, one could use clear furniture lacquer either brush quality or spray prior to top coat to shrink remaining wrinkles and offer a base. Nitrocellulose base works with essentially every paint we use in modelling as long as it goes on first.

        Two part urethane cures like epoxy through exothermic reaction. Unlike dope, what you spray on or brush on isn't going to change in weight, nothing evaporates. You don't hammer on colors to build it up. A light spray enough to cover the model is all that's needed. The clear is what offers the shine. This isn't a car, there's no need to build up clear coats to provide enough material to cut and buff. You spray it on just enough to cover the model. If one is to do a traditional dope model and buff it out, you will find that you will have 6-8 clear coat, two sanding sealer or primer coats, one white or silver coat followed by 6-7 clear top coats. That's a butt load of weight if you ask me.

         To answer the question, no it doesn't shrink with any appreciable amount. Unlike dope which will. And, in my opinion if applied correctly, it will be no heavier than a traditional paint job. Unlike a dope finish which is absolutely not fuel proof, it won't be harmed by glow fuel no matter how much nitro you spill on it. Dope today is so bad in terms of fuel resistance, even a splash on it will mar it or remove it.

akjgardner wrote:Went in hobby town USA Today and said where’s your dope ? He looked at me funny and said “ I don’t know what that is “ I said it’s airplane paint . We don’t have any !!!!! Sad day

I had a similar experience about ten years ago when I went into a hobby-shop and asked for glow fuel with with castor oil.

These days we don't even have a local hobby-shop, only web-shops...

rdw777 wrote:I have just a little Sig Lite Coat left so haven’t tried this experiment yet…. I’ve thought about using thinned down Duco cement as a dope just for try…. It thins easily in acetone and maybe a few drops of castor oil could be added to keep the acetone from gassing off so fast….Might be OK on sheet surfaces on small models…..Could probably get two or three ounces from the one oz tube of glue….. It may or may not have the solids content that dope has to provide strength….Just a thought…

Used as a glue works great on balsa…. In a way kind of like the old Ambroid cements, Double gluing the joint works best…. Joints need to be tight, It’s not a good gap filler…. I found out it about doing a few indoor free flight models….. Besides being very light, you can flood a joint with acetone to get it apart, Very handy in some situations to replace or reposition a part…..I’ve since used it in a few places on gas power in areas I may want to take apart….So far so good with fuel and oil resistance

Duco cement is OK, nitrate based

rdw777 wrote:I have just a little Sig Lite Coat left so haven’t tried this experiment yet…. I’ve thought about using thinned down Duco cement as a dope just for try…. It thins easily in acetone and maybe a few drops of castor oil could be added to keep the acetone from gassing off so fast….

RDW,

I'm not trying to be a smarta$$, so please be patient with me.
I'm also quick to experiment...especially when I don't have access to the appropriate materials.
How much is a tube or Duco going for these days? Even if it thins and works as you hope, Ken provides a known good and repeatable answer. That is, buy clear wood lacquer...a few key words will help narrow down your nitrocellulose (that is, NOT fuel proof) lacquer: "CLEAR, BRUSH, 30 minute dry time and LACQUER" may be in the name or description. I'll give examples in a minute. I did check each MDS sheets and found their chemical make-up to look remarkably similar. I'll know more about Fred's selection in a couple of weeks. I did open the can, and it smells like my first option.

I came back into the hobby using Sig nitrate (nitrocellulose) dope as my sealer/tissue adhesive, because like you, I was quickly running out of clear butyrate dope. Nitrate dope still needs a fuel-proofer, so I economized initially by using nitrate for wood fill, tissue adhesion, and initial tissue prep/seal. Then I fuel-proofer with butyrate dope.

Once I ran out of nitrate dope, I began looking for alternatives. FF guys mentioned a particular brand, so I tried and stuck with the brand. It is no longer as inexpensive as it was to have my local Mom/Pop hardware store source it in. Then I began researching comparable products from other manufacturer lines. Once again, FredV4 came to my aid (he knows all the skinny on this stuff).

I hope the following helps.

My original solution (I bought in quarts):
https://www.paintsupply.com/product/interior-wood-stains-conditioners-finishes-one/lacquers-two/clear-lacquers-three/1-gal-deft-dft010-clear-clear-wood-finish-brushing-lacquer-gloss/?utm_source=google&utm_medium=surfaces&gad=1&gclid=Cj0KCQjw1OmoBhDXARIsAAAYGSFrrwbGFRybrC1wq-ywDLcdJ1bIb_d5Ed31uTVyUJHfTbuYuhDF80caAgCnEALw_wcB

Alternate solution is:
https://www.amazon.com/Watco-63041-Lacquer-Clear-Finish/dp/B000BZZ5C2/ref=asc_df_B000BZZ5C2/?tag=hyprod-20&linkCode=df0&hvadid=198091577722&hvpos=&hvnetw=g&hvrand=3036511685085716978&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9014091&hvtargid=pla-323291405892&psc=1

And Fred's solution (paid $22 last week at Lowe's):
https://www.lowes.com/pd/Minwax-Gloss-Oil-based-Lacquer-Actual-Net-Contents-32-fl-oz/999913791

Hi Jim, No worries friend, Always looking to learn something new   … I didn’t know the Duco was nitrate based until Levent posted the data on it (Thanks for doing that Levent, appreciated ) …. I suppose I could try it as you explained, To use it as base coats and apply tissue trim, Then top coat with Lite Coat to make it last a little longer… I’d want to test a piece on the engine stand, Blast it with exhaust and raw fuel to see how well it stood up…. As far as cost of Duco, It would be more expensive per oz but I only build small stuff these days anyway….

Lacquer sounds like a good alternative…. I’m guessing to trim with tissue on sheet surfaces it would handle like dope?…. Use thinner to wick thru and tack the pieces down on base coats?…. I’ll have to look into it more as I run low….

I’ve tried Helmsman spar varnish on a couple of things and seems sorta OK…. Holding up alright on my wooden engine test stand….  The Zoomslot Saucer I recently made is covered with silver tissue, Trim is gold Rustoleum spray paint, Top coated with spar varnish…, Holding up OK except close to exhaust where it is burning off and thru the paint a little…. I would only use this system where not having a top notch finish would be OK… The varnish will yellow over time as well….

Interesting subject, Thanks for sharing….

Mixing Duco with dope or thinning it with acetone is a common practice when using silk. It's needed for under cambered wings or problematic compound curves such as wing tips. You thinned the Duco to use as a adhesive over the silk and pressed in place with a fingertip. The one trait dope has that virtually no other paints have is it's ability to retain tautness and remain flexible.