I am getting ready to finish up my 1/4 scale Bucker Jungmeister with Cub yellow dope. Do you guys use aluminum dope under yellow or white, or just spray the yellow on with no undercoat. It is covered with Sig Koverall, and has about 10 light coats of Sig Lite Cote applied. In the past I have always just used the yellow all the way but thought maybe an undercoat might make it cover better and be lighter in the long run.

 I think Ty has the right idea, I'd stay away from the silver and go with a white basecoat.

 Along with this though, other than a grey primer what's the best thing to use under white to speed up the covering?

From my experience and others I know, using silver under yellow makes the finish look like a hard boiled egg yoke, a dark yellow green color.. Ugly in other words. Use white under yellow. FWIW.

Ty, you're overcooking your hard boiled eggs!  Put the eggs in cold water, bring everything up to a gentle boil, just above a simmer, let it go for five minutes, then immediately run cold water into the pot to stop the cooking.  Run the cold water for a minute or so, then put the eggs (they'll be warm) out on a rack to dry.

Ideally, the yolks will be the same shade of yellow all the way through, although if I get some that are a bit brighter in the middle while still being distinctly cooked, I'm happy.

Trust me -- your eggs will taste much better.

Jim

My experience has been that yellow covers much better over white then over clear doped silkspan. 

Too bad you, well not too bad that you want to stay with dope all the way thru.   I have used the automotive Yellow paint with good results.   But, the under coat  was the light gray primer.

I use to use K&B Superpoxy on my R/C pattern planes, and it worked OK, but never had the sheen of a dope finish that I really like. I have also tried auto acrylic lacquer on one or two planes, and it was OK, but very brittle. So since I have been using dope for the last 20 years and it looks so good on a scale model like the Bucker, that Is what I want to use. I am going to experiment some on other things before I start spraying on the Bucker, but looks like I will be going with the white undercoat and the the yellow. I will most likely wait till the weather warms up so that I can spray it in the garage. I just wanted to get you guys input before I order the dope for this project. This thing has been on the back burner for quite a while. I started scratch building it years ago, and I think it is time to get it finished. I have not decided whether it is going to be R/C as it was originally intended, or converted to control line with a 2.4 radio for throttle. Or maybe set it up to fly with either. Anyway, it has been a fun project. I have an OS 90 FS four stroke to go in it when done. Here is a picture of the fuse sitting on my work bench so you can get an idea of the size of this monster.

It depends on what you want to accomplish. If you want a bright, vibrant yellow, then white is the way to go for an undercoat. I used gold undercoat for a yellow finish I did and gave more of a chrome yellow look and made it a bit more reflective. You can use other stuff, depending on the effect you want. I tried pearl bright white under yellow and got sort of a yellowy gold color that was really warm and pretty cool with the dark red and blue trim. Just depnds on what you want. Yellow and red are very transparent colors so whatever is underneath is going to show through one way or another.

For an extremely high gloss on the final coat of butyrate dope, add to your previously thinned dope 20% retarder and 1-2 ounces per quart of butyrate rejuvenator. Spray in the same maner as previous coats. This procedure provides an extremely high gloss by improving leveling and flow of the butyrate dope.

A paint expert can correct me if I'm wrong, but I'm almost certain that this only applies if you're not going to color sand and buff out the finish.  If you are going to buff things out, then you could well start with a satin finish and end up with a high gloss.

Jim-
The Cub was done with about 3 coats of Randolph F-6285 Cub Yellow over clear doped silkspan. It covered really well, great stuff. With white undercoats it would be even better. Probably two coats of butyrate clear over the color, no further polishing.

 I hesitate greatly to second guess Don, but 20% retarder sounds like a lot to me.

 Using primarily Brodak dope for all my spraying, I'm fairly new to the dope spraying game. I typically shoot my final clearcoats starting with about a 50/50 mix. Maybe a little more thinner than that sometimes depending on how it's going. I have yet to ever try using retarder. I'm usually satisfied with my results other than occasionally wishing it would give me some more drying time. Could I get away with adding 20% retarder to my current program?

I merely copied what the Randolph manual says. How do you s[pray dope up in Minnesota in the summer when the humididty is 70+% I get real nervous when it is above 50%, I watch the reading on my meter and wait for good conditions.
Bill Byles, where are you when I need you??

No problem Warbird; I need all the input I can get. The humidity is one of the reasons that I do my brushing in the basement in the winter. Although I do have a dehumidifier and keep it fairly dry year round. I try to keep it around 40% most of the time and do not have any trouble with blushing. Spraying in my garage is another story, but we do get days where the humidity is 15% or so even in the spring. Fall is usually the best though.

I really appreciate all you guys input as I can always learn something new. I sometimes get in a rut in doing things, and learning what others do is a real help in getting out. One of the things I like about dope is that no matter how bad you mess up you can usually fix it. It is just so workable. It is also easy to patch and repair.

What I use to use is the same color dope I was going to spray with baby powder in it. Smells great when sanded.