Oh boy - another Saturn V!
Actually, I'm building two Apogee Saturn Vs for a customer.
In quality and size, this Saturn is a big step up from the Estes kit.
Recently, I've been using the seam filling technique suggested by George Gassaway where you direct the primer/filler into a narrow strip directly on the recessed seam. You can read about the technique HERE.
When I tried this technique before, I used Carpenter's Wood Filler and sanded smooth. I then masked, as shown below, and used a spray primer. This time I'm using just the spray primer.
The seams on the Apogee Saturn V tubes were a little wider than normal but not deep enough to hold the Carpenter's Wood Filler. The CWF would chip and fall out of the seam when sanding.
This would be the perfect test model for George's method.
This is a big model, over five feet tall and 5.66" in diameter. Normally it would take a lot of primer and sanding.
I masked off 1/16" to the side of the seams with masking tape. In between the masking tape, long paper strips were taped down.
I've been using Dupli-Coat automotive filler primer after reading a recommendation on TRF. It's got one of those fancy nozzles. You can turn the tip for a wide spray or a thinner line. I turned the nozzle tip 90 degrees for the thin line spray. This way I could direct the spray right at the seams.
It was sprayed on two coats, fairly thick. I didn't sand it down between coats. I wanted to build up the primer before sanding. I didn't want to take the time to spray, remove the tape, sand then reapply another mask to spray again.
After the two thick coats, here's what it looked like once the entire mask was removed. You can really feel the raised primer "stepped" over seam.
Here's the tube area after sanding.
It took much less primer, sandpaper and time to get the seam filled by not spraying primer over the entire surface.
One of the purposes of the primer is to show imperfections such as glue and rough spots. These can be then cleaned up before the final color coats. Primer seals the surface and gives the final colors a better grab on the surface.
Granted, I'll spray a lighter coat of primer overall before the white base.