Covering Advice

[Rusty]

I ran across this information on RC Groups.  I'm not sure about it.  I figured I would let experts take a look.


"So..let's start with what I like to use product wise. Changing over to electrics 24yrs ago, really opened my eyes to alternatives other than true aircraft "dope". I often wonder why we ever felt the need for using "dope". But, it has been thought to be a requirement for generations. They only modeling intent dope that is really applicable to us is the old Aero-Gloss. And this is repackage automotive acrylic lacquer. It is low shrink and even more than nitrate dope, has superior adhesion.

My favorite "dope", is plain old hardware store brushing lacquer. This can be many different brands. Deft, Watco, Minwax, etc. The important thing is not to buy gloss. Get satin or matte. Some, like the Deft, have a very high white solid filler that usually is at the bottom of the can.(hopefully) I use a metal cup to take out the clearer lacquer and put in a working bottle. If you have a qt jar with metal top, just pour the clearer stuff into that. The filler at the bottom of the can is used for a balsa filler after thinning. I acquired much of this and congregate it in empty lacquer cans. This stuff really needs a lot of thinning, over 100%.

Speaking of thinning, using percentages is a very vague way of mixture control. Look for consistency of the thinning. It should be like water. Test by dipping the brush and watching the drip. No strings in the drip. Too thin is better than too thick. It just means an extra coat or two or more. The Watco seems to work well at a minimum of 60% thinner to obtain this consistency. The thinner dope dries faster, has higher penetration, sands easier, and does not form puddles under the covering surface. This giving a smoother consistent, uniform seal.

One very important tool, in our arsenal, is the brushes. These are called camel hair. But are actually squirrel. They must be seasoned to avoid loss of hair. Every so many years, I season a few new brushes. These are an investment. The most expensive brush I ever bought was a 4" camel at 42$ in 1980. Most brushes are 1/4"-1/2"W for our needs. Sometimes a 3/4" or 1" for large surfaces. Take that new brush, soak it in the thinned lacquer a few hours. remove and let harden a few hours. Put it back in the lacquer let it soak/let it harden. Do this as many times as it takes, so when wiping with a paper towel no hairs come out or maybe one or two. Now put it away for a week. It may still lose a hair or two till it is fully seasoned. Use the brush for wood sealing where sanding is required, till it is good for top sealing. NEVER clean your seasoned lacquer brush in thinner. Just wipe clean and harden. You can dry the brush after wiping by feathering over your fingers. Takes only a few minutes to soften for re-use."

[Dave_Trible]

I ran across this information on RC Groups.  I'm not sure about it.  I figured I would let experts take a look.


"So..let's start with what I like to use product wise. Changing over to electrics 24yrs ago, really opened my eyes to alternatives other than true aircraft "dope". I often wonder why we ever felt the need for using "dope". But, it has been thought to be a requirement for generations. They only modeling intent dope that is really applicable to us is the old Aero-Gloss. And this is repackage automotive acrylic lacquer. It is low shrink and even more than nitrate dope, has superior adhesion.

My favorite "dope", is plain old hardware store brushing lacquer. This can be many different brands. Deft, Watco, Minwax, etc. The important thing is not to buy gloss. Get satin or matte. Some, like the Deft, have a very high white solid filler that usually is at the bottom of the can.(hopefully) I use a metal cup to take out the clearer lacquer and put in a working bottle. If you have a qt jar with metal top, just pour the clearer stuff into that. The filler at the bottom of the can is used for a balsa filler after thinning. I acquired much of this and congregate it in empty lacquer cans. This stuff really needs a lot of thinning, over 100%.

Speaking of thinning, using percentages is a very vague way of mixture control. Look for consistency of the thinning. It should be like water. Test by dipping the brush and watching the drip. No strings in the drip. Too thin is better than too thick. It just means an extra coat or two or more. The Watco seems to work well at a minimum of 60% thinner to obtain this consistency. The thinner dope dries faster, has higher penetration, sands easier, and does not form puddles under the covering surface. This giving a smoother consistent, uniform seal.

One very important tool, in our arsenal, is the brushes. These are called camel hair. But are actually squirrel. They must be seasoned to avoid loss of hair. Every so many years, I season a few new brushes. These are an investment. The most expensive brush I ever bought was a 4" camel at 42$ in 1980. Most brushes are 1/4"-1/2"W for our needs. Sometimes a 3/4" or 1" for large surfaces. Take that new brush, soak it in the thinned lacquer a few hours. remove and let harden a few hours. Put it back in the lacquer let it soak/let it harden. Do this as many times as it takes, so when wiping with a paper towel no hairs come out or maybe one or two. Now put it away for a week. It may still lose a hair or two till it is fully seasoned. Use the brush for wood sealing where sanding is required, till it is good for top sealing. NEVER clean your seasoned lacquer brush in thinner. Just wipe clean and harden. You can dry the brush after wiping by feathering over your fingers. Takes only a few minutes to soften for re-use."

I think the key to his discussion here is in the first couple sentences "Changing over to electrics".   That means he could use water colors.   We've used dope for generations because it's fuel resistant.   Also it has known and controllable shrink ability for open bay covering.   I do notice some dash for the exits with dope when they can.   My real question is WHY?   It works great on even electrics too.   The phase 'if it ain't broke don't fix it' seems applicable here to me anyway.   He mentioned Aero Gloss as something special.   It was OK but VERY thin.   It usually took many more coats to build up a meaningful finish which I'm sure the sales department appreciated so they just kept adding the thinner.   That was something I immediately liked Sig dope for- a jar or can would cover much better and go further.   Now I use Randolph and like it even better.   Actually Ambroid cement was similar.  It was thinned to extreme and while it soaked in well it very often required double gluing to make a good joint.   Testors dope covered well but was NOT fuel proof generally so you had to also buy 'fuel proofer' to brush on over.   To me, that makes as much sense as using nitrate dope then having to put butyrate on top to fuel proof it.  I know many still do this but......why not just start with butyrate and have it fuel proof all the way down?  While I don't really know,  I doubt the other furniture lacquers he talks about are fuel proof or resistant.   However your ions shouldn't eat through them...


Dave

[Rusty]

Dave, what do you think about his brush care advice?   I never let my brush dry full of dope. 

[Motorman]

Who knew all these years I was using a Squirrel brush.

[Dave_Trible]

Dave, what do you think about his brush care advice?   I never let my brush dry full of dope.

By accident or laziness I do about what he says-not by intention.   When I'm done using the brush I swish it out in some acetone then just stand it in an open jar bristles up.   Yeah they end up sort of solid when dry.   I just soak it in acetone a few minutes when ready to use it again.   I will admit they very seldom ever drop a hair.   One of my brushes here I'm sure i've used at least ten years.   It doesn't seem to hurt them any.   I prefer camel hair but my favorite right now is a 3/4" white bristle ( no idea what) I got at Hobby Lobby a couple years ago.   Never seen it throw a bristle onto an airplane.

Dave