You want to know that as long as the lexan body is on, rain water does not hurt. What kills your electronics is the water on the ground. Unless your bottom chassis is fully sealed, it is unavoidable for some water to get in.
Your car will likely lose control when water gets into the receiver. Refer to the photo below, the one on the left has the receiver mounted on the upper deck, making it much safer (less likely to get wet).
RC motorbike also runs fine on wet track…
Bath tub body can be bad when water gets in … the bathtub actually holds the water from draining away…
If unfortunately water hits your electronics, stop the car immediately and having a hair dryer blowing at the electronics for several minutes. This should be able to fix the problem.
