Well, we have had to build this extensive hidden yard out of many pieces of 3 foot long track sections on a curve. So, how do we avoid getting kinks in the numerous joints?
Here is the process I followed. Frst, I lay the new section on the end of the track. In the first picture, you can see the pencil line drawn on the roadbbed that the bottom section of track is following. I do not spike down the last 6 inches so it can form a tangent to the curve. I can then see how much rail has to be pulled out of the tie strip to match the track ending.
Next, I place the new section into a fixture that I made out of homasote and strip wood that hold the tie strip in place as I draw out the rail. In the third picture you can see how much rail I had to pull out.
I then thread the tie strip onto the existing track to get the rail in place to put on the joiners. I cut away the tie plates so the joiner sits flat under the two rail sections. The new piece of track is left in a straight alignment when I put the joiner on so there is no lateral force on the rail. You can see this in the fourth picture.
I flux the rails and the joiner and then solder the pieces together. Once it cools I pull the rail to be sure I have a good joint. If all is okay, I then bend the new section along the pencil line as you can see in the last picture. The soldered joint is strong enough to ensure there is no kink and good conductivity.
I will leave a slip joint at the end of each siding to allow for expansion and contraction.