logo - Replicating s curve lines where gap between is exactly the same and top and bottom lines match replicated curved lines. (Illustrator)

I am trying to create a downward sloping curve for an 'R' and repeat it downwards while maintaining the same width and gap between the lines. So far I have only been able to get really close. When I replicate the top curve and try to align it below I can never get my desired result. The height or width is always slightly off and the curve isn't flowing with the above curve.

I tried again using the pen tool and a bunch of guides to try and get as precise as possible but still ended up with this:

I found Adobe illustrator perfect curve between two grids and replicated it in several ways but they are 90 arcs and I want a sound shape that has a more gentle flow to it like the first picture linked.

I also want to be able to match the gaps between each line. I was wondering how to set this up so that it would be mathematically sound; not just eyeballing it.