There's no need to trap the cat unless you want to give it to your local rescue group or something. Just make your rv an undesirable nest so the cat will find another home.
First thing to try: noise. Go in the rv and jump up and down, bash some pots and pans, turn on the water, etc. Make sure there is nothing OUTSIDE the rv that would make the cat hesitant to exit. No humans watching, no dogs, etc. Dawn or dusk would be the best time, because that's when cats are awake.
Then make it unappealing to come back. Cats don't like strong plant smells. Anything menthol, mint, lemon, eucalyptus, lavender etc., scented repels them. I used some mint-based wasp spray just today as a repellant. Lemon Pledge might also be good.
Of course, if there are kittens that's different. If you scare the mom too badly she will abandon them. If you scare or annoy her just a little bit, for several days in a row, she might move them. That would be ideal. Jump on the floors twice a day for 3-4 days. Noon is a good time because that is bedtime for cats.
If you end up with a litter of kittens and no mom, keep them very warm and call cat rescue. They will find someone to bottle feed them and find good homes for them. The kittens will be tame if raised by humans.
3/4 timing in a DIY van conversion. Backroads, mountains, boondocking, sometimes big cities for a change of pace.
