By eye

If this is a branchline, normally those are not laid with precision such as main lines. So if there is a little bit of not quite straight, I think that would look right. So my suggestion would be by eye. Just get it real close. Just my two cents.

"using N-scale roadbed to

  instead of N roadbed you could buy a roll of sheet cork then cut the roadbed out with scissors to the correct width and either straight or curved as needed. The cork comes in various thicknesses , for my N layout I used about .10 " thick which would be about 9 inches tall in HO scale.......DaveB 

spacer

We use a piece of 3/16" square styrene a couple of inches long to space apart the two halves of the cork roadbed. You can fill the gap with putty or spackle, but we usually use sifted builders sand, same as the rest of the ballast.

You Can Use

A third width of N cork less the bevel. But I left the gap per the above comment and filled it w/ drywall compound and then ballast over it. Filling the gap saves a lot of ballast unless you have a plentiful cheap supply such as the sand.

When I built my layout I felt that everything had to be on roadbed of some sort. Then when I went to scenic it, I discovered that is some places the track is nearly buried by the scenery. As a result you had to build up the scenery base to the edge of the roadbed to make it look right, a lot of extra work.

My point is to think about how it will look in the end, and do you even need a roadbed at all. I some locations, probably not.

Espee over Donner

I would lay it by eye and

I would lay it by eye and fill the middle with sand, caulk, or dry wall compound what ever is the most economical. Keep in mind you would want to glue the sand in position if it will be a while before everything gets ballasted. I can not remember who did something similar but he had a fairly large C&O layout 2 levels and topped HO cork with N for the main, HO for the sidings, and n for the spurs and industrial tracks. His layout looked very nice and you could really appreciate the high iron.

Narrow roadbed

Dear John,

As long as the roadbed is at least as wide as the gauge, let the tie ends overhang...
I know a number of modellers who have done this deliberately so as to mode the truly down-at-the-heels unkempt branch or NG operation with eroded/undermined ballast profile...

Happy Modelling,
Aim to Improve,
Prof Klyzlr

What I've Done

I used quite a bit of N scale cork on my HO layout for secondary tracks, making it three strips wide.  The center strip was installed upside down so the bevel was hidden, while the two outer strips were installed normally with the bevel toward the ballast slope.  After using acrylic latex caulk to glue down the track, there were no major gaps to fill.

To align the roadbed against the center line, I simply marked an additional line for the edge of the center strip.  marking it as a dashed line prevented any confusion as to which was the actual center and which represented the edge of the cork strip when I glued it down.  If you use something like a compass or dividers to mark the extra line it can go pretty fast, so there's not too much more work involved.

It will work.

I use N-scale cork on my Ho scale railroad to represent yard or secondary track.  I separate the N-scale cork road bed but I keep the beveled sides towards the center line with both bevels facing each other making a "V".  This way it is easy to lay it against the centerline and then the width is just a little wider then HO ties.  I glue the track down so this gap just fills up with glue.

Wouldn't the ballast hide the center strip?

Wouldn't the ballast hide the center strip?

Thanks for the ideas guys! I

Thanks for the ideas guys! I never would have come up with all those possibilities. Until after everything was glued down, of course.

John

Rather than sanding down HO

Rather than sanding down HO cork which is way too thick for my tastes, I use three strips of N-scale cork.  Doesn't matter much if you put the inner bevel up or down - track hides it pretty well if you leave it up.