I know this has been discussed before but I wanted to show my version.
Made from 1 1/4 and 3/4 PVC pipe, it does a fine job.
The vertical spacing is 7 inches.
The padding is pipe insulation.
The first version had three tiers to fit in my Dodge Journey but when Harriet bought the new Chrysler Pacifica, I found that I could add another tier.
The elastic bands keep the planes from rocking during transport.
Of course, it can be tailored to fit any vehicle and it's quite inexpensive to build.
I hope this information helps someone.
Bob Z.