Weight of paints

[Chuck Feldman]

Tradition says we use buterate dope to finish our models. I have been doing this and at the same time I am trying to make my models appear better. So I have been spraying on Brodaks Buterate clear dope for the final shine. However I have found that a drop of fuel will make an ugly white spot and that destroys the shine and it does not come off unless I sand it and refinish it. So  Ive decided that the modern dopes are inferior to the dope we used in the old days because I never had that problem back in the day. So what to do? Use automotive clear coat? Yes!  I mentioned to a friend that now that he is flying electric he could use what ever paint he wanted and his responce surprised me. He said that the models come out the same weight no matter which way you finish them. Not quite sure how this could be? Well this got me to thinking about the automotive clear and what I think it can do for us weight wise. Here is what I think; Use nitrate dope to apply and seal your covering. Once this is done you can apply sealer, filler or what ever you want and you can skip the use of buterate dope and just apply clearcoat over the finish. This should equal a weight savings.  I am considering use acrylic art paints to finish over the nitrate doped model and work on the Details trimming ink etc and so on. Then shoot the clear on. Any one with any knowledge about the weight of various paints I would like to hear from. Thanks Chuck

[Roger Vizioli]

Chuck,
Use a "fade proof" ink (ie Higgins) for trimming.
Not familiar w/ the acrylics re. availabilty of fade proof paints.
Keep us posted.
Roger V.

[kenneth cook]

         Chuck, I've done a few models just like you stated using the nitrate dope. I also have wrecked some of those models and thats where I had a bit of a problem. The automotive clear holds up well to the fuels but, when I had to repair the finish I did get into a problem. Where I cut back the finish to repair the area it wrinkled when the nitrate got under it. I found it took a few light dry coats to seal the repair than I could paint and clear. I had a few areas where this just wouldn't stop. I'm not sure if this is with all the automotive clears but I do believe were trying to use 2 products that aren't really compatible. As explained to me by my body shop friends, the 2 part automotive clear doesn't really have the flexibility that our traditional dopes have. They can be prone to sheeting off on flexible surfaces. I have had this happen but nothing real bad. As for the weight, I would have to say the 2 part clear has to be heavier as dope gasses off and the majority of solvents evaporate. I would really have to weigh throughout the painting process to say for sure. Ken

[Jerry Leuty]

          Chuck you know that as a Intermediate pilot that I build planes that look good but do not hold up too long. After a few flights there are scratches and nicks. Here is what I do. I use rattle can Polyurethane clear and Rust-O-lem color. Pretty planes are great to look at and at this year's VSC there were several. But an ordinary nice finish plane that flies well in your hands will gather more points than any 20 pointer flown unsuccessfully in a pattern. I know that you want to move into the Advaced ranks and fly great looking planes. But this sport/hobby does not pay much so; build, fly, and have some fun......................Jerry

[billbyles]

Tradition says we use buterate dope to finish our models. I have been doing this and at the same time I am trying to make my models appear better. So I have been spraying on Brodaks Buterate clear dope for the final shine. However I have found that a drop of fuel will make an ugly white spot and that destroys the shine and it does not come off unless I sand it and refinish it. So  Ive decided that the modern dopes are inferior to the dope we used in the old days because I never had that problem back in the day. So what to do? Use automotive clear coat? Yes!  I mentioned to a friend that now that he is flying electric he could use what ever paint he wanted and his responce surprised me. He said that the models come out the same weight no matter which way you finish them. Not quite sure how this could be? Well this got me to thinking about the automotive clear and what I think it can do for us weight wise. Here is what I think; Use nitrate dope to apply and seal your covering. Once this is done you can apply sealer, filler or what ever you want and you can skip the use of buterate dope and just apply clearcoat over the finish. This should equal a weight savings.  I am considering use acrylic art paints to finish over the nitrate doped model and work on the Details trimming ink etc and so on. Then shoot the clear on. Any one with any knowledge about the weight of various paints I would like to hear from. Thanks Chuck

Hi Chuck,

Your problem is not due to the butyrate.  Nitrate dope can be used as a base coat on your airplanes but there is no advantage to doing so.  I use butyrate exclusively from the bare balsa through the final clear coats.  I typically use Randolph clear butyrate (tautening type) for the base coats on the bare balsa, then apply the silkspan with more of the same.  When the silkspan is dry (I apply it wet to get the initial tautening) I apply three coats of the tautening Randolph clear thinned about 50% to the open bay areas to get the silkspan taut on a permanent basis.  The rest of the clear buildup is Randolph non-tautening type butyrate dope, including the zinc stearate coats.  I use Randolph colored butyrate dope for all of the colors as Randolph has a huge selection of colors, and all of the colored dopes are non-tautening.

For the final clearcoats I have always used Sig Light-Coat, which is a non-tautening butyrate and it seems to be more fuel-resistant than any other clear dope I have used.  I have not ever found a truly fuel-proof dope, some are just more fuel-resistant than others and Sig is the most fuel-resistant of the others.  In my business (antique, classic, & warbird aircraft I also use the automotive series of polyurethanes, including the clears.  The two-part automotive clears are the only truly fuel-proof clear finish out there (Two-part meaning the base clear + the catalyst + plus the thinner as needed.)

[Peter Germann]

Here are the related numbers as found when finishing my last airplane:

Trivial Pursuit PA .75 Finish Weights in Grams per sq. dm. / oz. per sq. ft.

1.) Polyspan, attached dry with nitrate dope and heat shrinked: 0.25 Grams per sq. dm.  /  0.0819 oz. per sq. ft.

2.) Silkspan GM (Medium) attached wet with nitrate dope: 0.25 Grams per sq. dm.  /  0.0819 oz. per sq. ft.

3.) 6 coats of nitrate dope 50% thinned, brushed: 0.6 Grams per sq. dm. /  0.1966 oz. per sq. ft.

4.) 1 automotive base coat, red metallic, sprayed, plus trim color: 0.3 Grams per sq. dm.  /  0.0983 oz. per sq. ft.

5.) 1 ½  automotive 2-K clear coat, 10% thinned, sprayed: 0.5 Grams per sq. dm.  /  0.1638 oz. per sq. ft.


Total specific weight:  1.9 Grams per sq. dm.  /  0.6224 oz. per sq. ft.

Total airplane finish weight: 245 Grams /  8.6 oz.

Airplane empty weight: 1'753 Gr.  /  61.8 oz

[john e. holliday]

When trying to compete in F2C, Bill Wright put us onto model railroad paints.  Very small bottles of all kinds of colors.  Went on super thin coats, but were not transparent like dope was.  Had to be careful because if you didn't put a clear coat over it, it would rub off.  I mean we are talking finishes in grams not ounces when done.  Base coats were very light fiber glas and epoxy.  Rolled tissue to take off as much epoxy as we could.  The final coat after all the trims/graphics was a two part clear that came out super slick and shiny.  Made catching for pit stops a fun thing.   

[Randy Powell]

Couple of brief notes. Automotive clear (catalyzed polyurethane) is heavy. Not much solvents and very high in solids so what you shoot on is pretty much what you have. Dope is high in solvents and generally not very high in solids so of what you shoot on, more than half evaporates. One coat of automotive clear will equal 5 or 6 coats of butyrate clear. That's not necessarily a bad thing. You shoot one, even coat of catalyzed polyurethane and you're done. Probably add 2oz or so (for a 650 square inch plane). It would be the same for butyrate by the time you built up enough to rub out. You just have to go easy on the catalyzed products.

Weight of paints:

Keep in mind that butyrate colors have pigment, stabilizers and binders in them. As a consequence, they tend to be heavier. Also, weight will depend on the color you're using. White is quite heavy due to the amount of pigment. Black is relatively light since it doesn't take much pigment to cover. If you use automotive urethane based single stage colors, they tend to be very, very light. This is because there are no stabilizers in them. They depend on the clear topcoat to stabilize them. So what you get is mostly just pigment. On the other hand, they are very fragile until you get the topcoat on. I've wiped off a color with alcohol. It's a matter of what you want, I guess. Auto Air colors (water based urethane colors) are very light also and for much the same reason. The water evaporates and leaves just the toner (pigment). But again, they are very fragile. With both these urethane based colors, you have to us an intercoat between the color and top coat if you are going to do any inking or decals or whatever. They are also sensitive to taping, so an intercoat between base color and trim colors is advisable (and you start putting on weight). This is why I quite using automotive color coats. They ended up being as heavy or heavier than butyrate due to the intercoats.

Repair:

One of the things to note is repairing finishes that have possible incompatible layers is that it can be tricky. I generally use butyrate lacquer from wood up to topcoat the shoot catalyzed polyurethane. When repairing, you have to sand the top coat back past the repair and into the color coats of undisturbed paint. Do the repair and re-shoot the colors on the repaired area, then lightly sand the topcoat further back to rough it a bit. Then shoot new topcoat back onto the roughed up area. When done, empty the gun out and fill it with urethane reducer and shoot over the whole area lightly.  This allows the new finish to integrate with the underlying paint. But go easy. You don't want to melt it,

[billbyles]

<snip

Weight of paints:

Keep in mind that butyrate colors have pigment, stabilizers and binders in them. As a consequence, they tend to be heavier. Than clear.

Also, weight will depend on the color you're using. White is quite heavy due to the amount of pigment.  Also the pigment is titanium dioxide and is quite heavy.

Black is relatively light since it doesn't take much pigment to cover.  The black pigment is carbon black and is the lightest weight pigment.

If you use automotive urethane based single stage colors, they tend to be very, very light.  I think you meant basecoat/clearcoat system which is two stage, but I knew what you meant.

This is because there are no stabilizers in them. They depend on the clear topcoat to stabilize them. So what you get is mostly just pigment. On the other hand, they are very fragile until you get the topcoat on. I've wiped off a color with alcohol. It's a matter of what you want, I guess. Auto Air colors (water based urethane colors) are very light also and for much the same reason. The water evaporates and leaves just the toner (pigment). But again, they are very fragile. With both these urethane based colors, you have to us an intercoat between the color and top coat if you are going to do any inking or decals or whatever. They are also sensitive to taping, so an intercoat between base color and trim colors is advisable (and you start putting on weight). This is why I quite using automotive color coats. They ended up being as heavy or heavier than butyrate due to the intercoats.  Actually, one of the neat things about the Sikkens basecoat/clearcoat system I used in my full-scale airplane restoration shop is that you can apply the basecoat, go clean the gun, come back & tape off the first trim color & shoot it right away, unmask and do the next trim color, etc.  Sikkens recommended interval between shooting the base color and taping on it is 15 minutes; I was very skeptical on the first go-around but enthusiastic after I found that it worked like magic.  However, I agree that you can't handle the basecoat colors, wipe them with anything except a tack rag, or do ink lines without the clearcoat to protect it.

Repair:

One of the things to note is repairing finishes that have possible incompatible layers is that it can be tricky. I generally use butyrate lacquer from wood up to topcoat the shoot catalyzed polyurethane. When repairing, you have to sand the top coat back past the repair and into the color coats of undisturbed paint. Do the repair and re-shoot the colors on the repaired area, then lightly sand the topcoat further back to rough it a bit. Then shoot new topcoat back onto the roughed up area. When done, empty the gun out and fill it with urethane reducer and shoot over the whole area lightly.  This allows the new finish to integrate with the underlying paint. But go easy. You don't want to melt it,

A lot of good info here, Randy...obviously the voice of your experience - thanks!

[john e. holliday]

Thanks to both Randy and Bill,  a lot of info I did not know about.  Guess that is why the paint came off the Accenter when I did my numbers.

[Jim Pollock]

Gosh,

Did everyone forget that good ole Epoxy paint is also totally fuel prof as well?  At least the planes I painted with Epoxy were totally fuel prof!  Lets see, I painted my original Akromaster with K&B Epoxy, so I guess Klass Kote would do every bit as well?

Jim Pollock   

[Randy Powell]

>>As a consequence, they tend to be heavier. Than clear. <<

Well, yea. But butyrate is also a lot heavier that urethane automotive color that are mostly toner and carrier. I shot a plane a couple of years ago with urethane basecoat color. I couldn't believe how little weight the colors added. Maybe a 1/4oz for the entire base color and trim.

[Chuck Feldman]

K&B Epoxy;  How did I forget that??? used it back in 1978 and it was great!!!!!!!! When I came back to flying it was gone? Someone said the EPA outlawed it.  What a shame it was the answer!  Thanks guys for all this good discussion. Please continue. Does anyone know of a good epoxy paint system? Thanks

[Jim Pollock]

Chuck,

Yes the other epoxy I mentioned  "Kalss-Kote" I understand is nearly identical to K&B Epoxy.

It's availiable on a web site somewhere look around the suppliers and it may be listed there....

Jim Pollock,   

[Randy Powell]

Yep, KlassKote is very near K&B Superpoxy. I think Brett Buck uses it now. I've never tried it, but I may start.

[Mark Scarborough]

The biggest problem I see with using Klass Kote is that its a SINGLE STAGE product, that means that every single color and coat you apply has Pigment, binder, glossing agents, et al. This means that each coat is very heavy and backmasking would be imperitive to keep the weight in check. However for a simple scheme no big deal but I dont think you want to clear coat it unless you can really spray the colors light.
Another thing to consider is enviroment you spray in, as well as how long do you have before you are going to fly. with dope, you need to really let it cook for weeks before you try to get that really good gloss polished. My Avenger, while not a hand rubbed finish, is shinier, and has never been polished at all. Nor will it be. One of the benefits of using a very good spray gun, and getting the mixture right on the clear. With dope, you have a broader window of temp and time to apply than with a 2part clear. But then I can fly mine the next day without worrying about the clear either, so there are drawbacks and advantages both ways.