Question about painting fine lines

MikeV wrote:

Triarius wrote: First thing: take off the air cap guard, reverse it, and put it back on. This allows you to get closer and changes the air flow pattern at the tip. Reversing the tip guard doesn't affect the air flow at all, it just allows you better access to the needle to clean it with your fingernails as T-shirt artists do. It also allows you to get even closer as mentioned. Mike

Mike, while I would normally defer completely to your vast knowledge and experience of airbrushes, I must partially disagree, largely because I did not speak as precisely as my wont.

The air cap guard has nothing to do with internal air flow. What I should have said is that reversing the tip affects the external pattern of airflow—the way the stream of air from the airbrush itself interacts with the standing air in its path. There was an article in the March, 2001 FSM "Airbrush Aerodynamics" that briefly discussed this (page 48, sidebar). At longer distances, the air cap guard actually serves as a secondary nozzle, reducing turbulence at the oriface. At close distances, this is not necessary—the air cap guard may even produce more turbulence.

Do you really clean your tip with your fingernails?

I've had an opotunity to use the Omni brush and I did a "head-to-head" with my Iwata HP-CR years ago.  The Omni performed great, especially at spraying fine lines.  I'd agree with others here that, while reversing the tip-guard doesn't affect the airflow, it did allow me to get in close as needed to maintain the tight line pattern.  Also metioned, that I would ehco is, (and it's an important one) is, paint-to thinner ratio combined with an effective air pressure setting.  My set up consists of thinned paint mixed 1:1, with the compressor set to, between 10 to 15 psi for fine lines with T/MM enamel and Tamiya acrylics.  My Iwata, and similarly (if not identical) the Omni sprays very tight fine lines with their reletively large tip/ needle size of approx. .5mm.  We've talking camo outlining on 1/72nd scale in my case!  I've also had similar/ identical experience with the Badger 150 as well, I just like a gravity feed airbrush for ease of use.  So I think you're got all the right ingredients for shooting some nice lines for camo and or detail if you make some minor adgustments in set up.  Hope this helps!  

Take a gander at this 1/72nd scale MiG-23 Flogger I did with an Omini airbrush years ago, all free-hand:

 

Triarius wrote:

First thing: take off the air cap guard, reverse it, and put it back on. This allows you to get closer and changes the air flow pattern at the tip.

Reversing the tip guard doesn't affect the air flow at all, it just allows you better access to the needle to clean it with your fingernails as T-shirt artists do. It also allows you to get even closer as mentioned.
 

Mike

TryintoModel wrote:

Ahhh, I see.  I got home and checked it out.  I guess it would help if I read instructions, but what fun would that be?   I'll have to practice some more and see what results I can get.  Thanks for the help.

LOL,

I have an Omni 4000 and I LOVE it. You should be able to do the fine lines with np at all with this, just do what Triarius says and you should do fine, lol no pun there

Have a GREAT day

Bud

I always RTFM—some of the things I've played with, it helps them not to go "BOOM!" unexpectedly… It also keeps me from breaking things that really don't need to be broken, as I also occasionally subscribe to the philosophy "If it doesn't fit, force it. If it still doesn't fit, get a bigger hammer. If it breaks, it needed fixing, anyway!"

I think I know why modelers, in particular, tend not to read instructions: so often, the ones that come with the kit are wrong, misleading, or inadequate. And then there are the translation problems: "Farb now the glimrod," and "Craunch along the stantion at the mashing together place." (Quoted from the comic strip "Shoe" by Jeff McNelly. IIRC, he was quoting from a set of instructions.)

Ahhh, I see.  I got home and checked it out.  I guess it would help if I read instructions, but what fun would that be?   I'll have to practice some more and see what results I can get.  Thanks for the help.

The air cap guard is part no. T8131G. This is just the cone. When the air brush is fully assembled, it resembles a rocket nozzle on the front of the airbrush. It has a knurled rim. Unscrew, reverse, screw on finger tight only. On the second page of the instructions, this procedure is listed under the heading "FINE DETAIL."

Thinning might be a big part of the problem.  I tried thinning a bit more than normal, but maybe it needs to be more.

What is the air cap guard?  I'm trying to picture it, but I'm coming up blank trying to think of any of the pieces that could be reversed.

You should be able to get finer than 1 mm with the Omni 4000. I just started using mine, and had little trouble getting that fine. This airbrush has a dual taper needle, allowing for both coarse and fairly fine work with the same brush.

First thing: take off the air cap guard, reverse it, and put it back on. This allows you to get closer and changes the air flow pattern at the tip.

What follows works for me:

Make sure your paint is adequately reduced (thinned). For fine lines, thinner is better.

Reduce your air pressure to 8 to 10 psi.

Practice, practice, practice!

A final tip: I've discovered that you can adjust the trigger resistance to suit your fingers by adjusting the spring adjuster—helps a lot with control.