Okay, instead of guessing and saying "I think that'd be okay"... I decided to do about 15 minutes of research and take some measurements. Here's what I've found....
"Chicken Wire" on FT's , F-2's and F-3's is called that because it IS chicken wire...or "poultry cloth" and can be found in various gauges of wire with different sized "mesh" or sized HOLES. Most comes in either 1" mesh or 2" mesh.
However I didn't want to just assume the chicken wire used on early F's was 1" or 2", so I took a measurement off of one of my Kato F-3's and the height of the vent that is covered by chicken wire is exactly 24".
All I needed to do was find a sharp prototype photo and count the "holes" from top to bottom over a length of 24" to see what size mesh EMD chicken wire was.
12 holes.
So, they used 2" mesh poultry cloth to cover the vents.
That means I need to find a stainless steel mesh that has a .32mm (.0125") aperture or mesh.
Since Small Parts is no longer a valid place to look for small stuff, I just did a Google search for "fine stainless steel mesh" and a lot of places came up. I chose
http://www.ssmesh.org/stainless-steel-wire-mesh-weaving/ultrathinssmesh.html because they were in the USA, but there's an interesting British company also if you want to order from overseas here:
http://www.themeshcompany.com/products/Fine-Mesh---0.5mm---0.025mm-Hole-Size.htmlThere are a lot of other places too, and since this post isn't designed to tell you who to buy from...I'll continue on with WHAT I would buy if I were you.
Wire mesh that has 80 openings per inch is logically called "80 mesh"...this is what corresponds most correctly to the prototype's "cloth openings" of 2 inches.
Although it's unrealistic to hope for a wire size that corresponds to 20 ga wire in the full-sized world (two ten-thousandths of an inch... .0002"), it's a good thing to look for wire size that's pretty small. I'd say that wire size between .002" ( .050mm) and .001" ( .025mm) is realistic enough and surprisingly doesn't seem to be that difficult to come by.
The opening area percentage should be over 50% which means that mesh with finer wire will have more open area...which will look better to represent "chicken wire" on N-scale EMD FT's and F-3's. An 80 mesh screen with .050mm wire has an opening percentage of 71%, which is pretty good.
Sooooo...not be be redundant, but what you want to get to represent scale sized chicken wire is 80 mesh SS made from .050mm wire (.002").Looking at photos of F3's, it looks as if the chicken wire's "cloth openings" have the same height as width, so mesh with square holes is what you want...then tip it 45 deg.
Sometimes, scale sized stuff doesn't look the best, as it becomes virtually invisible. I've found that wire and thread remains easily visible down to .001". Paint on it will add to the diameter very quickly, so apply only a very thin, even coat. However, let's take a look at one example of a commonly accepted well-detailed N-scale F-3 to see what looks "good"....
Photo (1) - Here's a photo of a pure stock Kato F-3 showing the cast-on chicken wire:
I measured the Kato chicken wire, and it works out to a little less than 53 mesh (53 holes per inch). I noticed that the holes are not the same width as height, which is incorrect...so I measured their vertical dimension, and disregarded their horizontal measurement.
If you like the way this mesh looks, you can make it look even better by finding a slightly smaller mesh size, with a better opening area percentage...meaning "finer wire" than what this well-accepted model has. Going to the chart at the Boegger site, I see they've got 56 mesh (56 openings per inch) built with .040mm (.0016") wire, for an excellent opening percentage of 83%.
If the price isn't too steep, I'd buy a square foot of both the 80 mesh and the 56 mesh and see which one gives you a better look. I have a hunch that the 56 mesh with its noticeably better opening percentage is going to look the best...but that's just a hunch.
I went to my materials drawer and found some screen that I've used for various things in the past, and it's 100 mesh screen with .040mm (.0016") wire. This looks great when lightly painted, but its openings are way too small for an accurate representation of EMD chicken wire in N-scale and would probably block viewing what's underneath it if painted body color, losing that characteristic and prototype "airy" look.
I cut my 100 mesh stainless screening on a cutting mat, with a metal straightedge, using a new, sharp #11 X-Acto blade, and I can get very accurate results doing this. I assume you would be able to get equally exact results with either the 80 mesh and/or the 53 mesh SS screen, although the 80 mesh screen with its .002" wire may be more difficult than the screen with the .0016" wire. The wire is very stiff, and although it's .0016" when I measure its diameter, when I measure the thickness of the screen, it's .008" thick.
Although I like the Intermountain F-3's (UP had no FT's)...I really (REALLY) dislike the etched "chicken wire" on these models...so much that I haven't bought any because of that negative feature. Maybe I should get an ABB set and see what replacing the etched parts with cut SS 80 mesh or 53 mesh screening will do for 'em. I have another hunch it would drastically improve their looks with not a lot of effort.
Hmmmmmm....
Hope this assists the OP in finding the "right" sized screen for that ten-year long F-2 job. I'm gonna order some of this screen in the next few days to have on hand when I decide to see how it looks on that IMR F-3 I haven't got yet!
Cheerio!
Bob Gilmore
