So this is the fan we removed from our 5th wheel RV when we bought it 5 years ago (we upgraded it to a fantastic fan with wind and rain sensor). Husband was sure the fantastic fan (without upgrades) would come in handy. He installed it in my GH (in the vent) - just has to connect it now to the transformer on order from Amazon ($16, "plug-style). The fan is 12 volt. And there is a trim piece to put around the fan. He cut and painted a piece of wood and inserted that in the window vent - and mounted the fan in the center.
Once connected to electric, I can simply turn the knob to open it electrically. For now I am using the hand crank - but the transformer will be here Wed and then the fan can actually run too. On a cold rainy day like today it is great to let in some fresh air, but the outer cover keeps rain from getting in . It is also screened - so cuts down on the bugs.
We are going to the local RV to see if they have any used cheap/free. People take these out of their RVs all the time to upgrade to the fancier models. It's not all that heavy, and with a little care, I can still actually open the entire window vent (as usual) and prop it open with the black "stick prop" that came on it). But why would I want to -- when I can just turn the fan on !