Question from a Rookie...

Narrow masking tape perhaps?  You can lay out marks by using a laser level to cast a straight line, make reference marks in pencil on the model they lay the tape along those marks.

Instead of painting the white, cut white decal paper in the shape necessary and place on the model.

Several ways to do it, just need to think about it and plan which works best.

All you need is a length of masking tape (low tac painter's tape is the best for this).  Wrap it around the cylinder and if the edge wraps around on itself evenly, you've got a straight line.  Masking tape will definitely let you know if it's on straight or not.  On a simple cylinder, it will wrinkle if it's slightly crooked or start to spiral if it's really cockeyed.

-Fred

I'm with Hawkeye on this one.

But If you're not in the laser-level crowd, you could build up a "jig" with (insert your favourite flat items here!) standing beside your circular piece. Make sure the model & jig are level relative to each other. Then lay a pencil down flat on your jig, and slowly turn the model piece so the pencil leaves a light mark. You'll need to do some adjusting to get the line in the right place, but it should work.

Vance

Thanks for the prompt replys

All good ideas, I like the jig idea, that would be easy to build and suit lots of kits in the 1/144 scale. 

I have already painted the white on my current project so I will try the narrow masking tape method for the second colour, aluminum.

I had not thought of the decal sheet idea, I have never used decals by the sheet.  I have noticed in the past, when I use a white decal, that the underlying colour could be a problem, showing thru.  I assume the right primer colour would take care of that issue.

The decal technique actually gave me an idea.  If my masking does not create the kind of demarcation line I want, I could apply a narrow band of white decal to make a clean line. 

Thanks again,

Doug

P.S.   I have never used this forum before so I am not sure if my reply will be seen by all contributors or not, I am assuming so.

Hey Doug - yes, the whole gang gets to see the replies - even viewers that hadn't contributed. It's a great way to pick up information. to the forums & good luck with your project,

Vance

Just as a bit of additional help.  Keep in mind that the wider the tape is the easier it will be to make a straight mask line around the body.  If the tape is thin it will be a lot easier for it to "wander" up and down as you wrap the model.  In the past instead of using masking tape I have wrapped the model with a sheet of paper to reduce the possibility of twisting even further.