What are your preferences regarding filler application? I'm assuming that since most of it is going to be sanded off there really would't be much of a practical difference, but my assumptions are often wrong (imagine that...). Maybe skip the traditional filler and go straight to primer? This is my first time using carbon, and it seems to be much smoother that silkspan at this stage, though Phil Granderson's method uses filler over carbon...

 

I'm looking to bump up my finishes, so any thoughts, opinions, ideas or admonishments would be most welcome!

Thanks!

Mike

I've done it both ways. I have an auto primer gun (cheap Harbor Freight job) and it works pretty well. I don't see an advantage either way except maybe a little easier to sand the spray on as there are no brush ridges to sand down.

words have meanings,,

surfacer= material typically sprayed on to reduce the magnitude of surface imperfections,, ( in our case to fill wood grain and such)
primer = typically sued to denote a material which is primarily used to promote adhesion between dissimilar materials,, ( balsa and silkspan)
sealer = a material that isolates the top coats from the bottom coats, intercoat barrier, in other words, keeps the surfacer from interacting with the base coats and causing them to swell up, or in my case, I use a catalized sealer to prevent the solvents in my color coats from infusing into the carefully sanded Primer coats and causing them to swell ( then shrink) leaving unpleasant grain showing through

so, filler, is surfacer,, and yes, it fills low spots,  the depth or surface area of those imperfections is what causes weight gain,, some cannot be avoided, like the grain in the wood, some can be avoided, like wavy sheeting, poor sanding of the balsa, or bad fit joints,, the "filler" or surfacer can be what is commonly called primer, ( normally grey with talc added like Kondar DZ-3) or it can be clear dope with talk or Zinc Stearate added, or it can be just plane old clear dope,, if its filling voids or imperfections it is surfacer

if you are putting a barrier coat on top of the surfacer, then its a sealer no matter what material it is,, some materials are obviouslyh better suited to this task than others,,

This is not unlike the ongoing debate about "power": and the misuse of the term or I should say, the misuse of its definition,,,

that said, in almost all cases, if you can spray it on, you will get less shrinkage, less dry time, and less added weight ( assuming you sand properly) when compared to brushing it on.
the One caveat to this, when you are building up the primer on bare wood,, ( the clear you put on before silkspan or carbon) Dope is such a low solids material, you would greatly add time to the project to spray these on , I maintain you will ultimately get a lighter better finish than brushing it
Now before anyone attacks this statement, YES you can get a spectacular finish using proper brushing technique,, in fact I personally brush on a lot of my build up layers of dope,, but,, BUT< if you sprayed it all, you would have less dry time, and less sanding ultimately,,

Mark, thank you for addressing one of my pet peeves, especially primer and surfacing.  You know, or at least I think you know that I break a lot of rules when it comes to painting in general, but substrate prep and adhesion doesn't get by me.

I'm in the process of finishing up a project now where I used no primer and my filler coats were all clear dope.  Voids were handled with clear dope and zinc stearate applied with an airbrush.  So I guess the answer is yes, in some cases a voids, or dents and other imperfections can be dealt with by spraying.

Actually, Robert covered this pretty well, I thought, in his video using his Napa spray stuff.  It builds quickly and sands easily.  A little pricey for my tastes and is impractical for a lot of my work.

I wish more your wisdom would be heeded on this forum.

There's got to be a compromise here someplace!  I think I'll use a roller next time.

There's got to be a compromise here someplace!  I think I'll use a roller next time.

Westcott, of all people,, just go back to your whisk broom to apply primer,, lol

as always, ( and you do the same thing in your field of expertise) I always default to the CORRECT answer, there is always an alternative, but ya takes your chances

words have meanings,,

surfacer= material typically sprayed on to reduce the magnitude of surface imperfections,, ( in our case to fill wood grain and such)
primer = typically sued to denote a material which is primarily used to promote adhesion between dissimilar materials,, ( balsa and silkspan)
sealer = a material that isolates the top coats from the bottom coats, intercoat barrier, in other words, keeps the surfacer from interacting with the base coats and causing them to swell up, or in my case, I use a catalized sealer to prevent the solvents in my color coats from infusing into the carefully sanded Primer coats and causing them to swell ( then shrink) leaving unpleasant grain showing so, filler, is surfacer,, and yes, it fills low spots,  the depth or surface area of those imperfections is what causes weight gain,, some cannot be avoided, like the grain in the wood, some can be avoided, like wavy sheeting, poor sanding of the balsa, or bad fit joints,, the "filler" or surfacer can be what is commonly called primer, ( normally grey with talc added like Kondar DZ-3) or it can be clear dope with talk or Zinc Stearate added, or it can be just plane old clear dope,, if its filling voids or imperfections it is surfacer

if you are putting a barrier coat on top of the surfacer, then its a sealer no matter what material it is,, some materials are obviouslyh better suited to this task than others,,

This is not unlike the ongoing debate about "power": and the misuse of the term or I should say, the misuse of its definition,,,

that said, in almost all cases, if you can spray it on, you will get less shrinkage, less dry time, and less added weight ( assuming you sand properly) when compared to brushing it on.
the One caveat to this, when you are building up the primer on bare wood,, ( the clear you put on before silkspan or carbon) Dope is such a low solids material, you would greatly add time to the project to spray these on , I maintain you will ultimately get a lighter better finish than brushing it
Now before anyone attacks this statement, YES you can get a spectacular finish using proper brushing technique,, in fact I personally brush on a lot of my build up layers of dope,, but,, BUT< if you sprayed it all, you would have less dry time, and less sanding ultimately,,

One of the best explanations of finish layers since college, thanks for posting ,

I'm constantly amazed at the depth of knowledge on this forum. I can't build as many airplanes as it would take to try everyone's individual methods, but I wish I could!

I've got the bird in question sanded and ready for filler and I think I'm going to brush on dope with zinc stearate this time. I know it probably means a bit more sanding to keep it light, but my wife has been complaining that there isn't enough dust coming out of the model room lately and I need to sand more...

Yeah right...

Of course as you sand these things you see everything, and it all looks like glaring warts all over the airplane until you step back and give it a more realistic assessment. In reality, the surface looks pretty good at this point and it probably won't take much to fill the voids.

Yeah right...

Thanks again guys. Awesome information!

Mike