I need to draw up a blueprint so to speak of a solar panel mount.?

The solar panel is used to heat swimming pools. I need something that will make it east to draw a moderately descriptive blueprint of the measurements and the proper embly order of treated lumber. Doesn't matter if it's freeware or if I have to purchase it. Just need some ideas of user friendly software. Any ideas would be greatly appreciated. Thank you in advance for your time!!!