My cats travel with me. One is fine and loves to look out the windows. The other is more timid and nervous in the vehicle.
It may take you a few trial and error attempts to determine if your cat is throwing up due to motion sickness or from the stress of being in a moving vehicle. Some cats just really don't like being in a moving vehicle.
Here are a few tips:
If he hunkers down, get a "cat cave" - a soft sided bed that he can hide in. He will still hunker, but he will feel safer.
Many cats really don't like seeing the scenery passing by at speed. Covering the crate with a blanket can help prevent that.
Don't put him on the floor of the RV - the engine vibrations are stronger there and upsetting. Put him on the bed so there's a mattress to dampen the vibrations. Also the back of the RV will have less vibrations than the front (unless it's a rear engine). That should help ease his sickness.
If he is not trying to get out of the crate, then I would keep him in it with the cat cave and cover and see if that helps.
I have tried several pheromones (including feliway) and they did not work on any of my cats.
My vet suggested xylkene instead as an OTC calming treatment. I have used it on my fearful dog for stressful situations and it helps her stay calm. I used it on both cats for a 5+ hour drive and after the first 10 minutes or so, they just napped in the back of the suv for the rest of the trip. The dog acts like she was given a valium without the sedative effect. The cats got sleepier. Looney1 who enjoys going places usually moves from window to window looking out, with the zylkene, he just slept. When we arrived at the campground, he was ready to go explore, so it wasn't knocking him out, just relaxing him.
My nervous boy really likes to cuddle. As it's just me in the vehicle, I can't do that. If I traveled with someone, I would let him cuddle with me in the passenger seat. For cats, your touch can help them relax.
I have used cerenia on my dogs for a 4 hour whale watching cruise and it worked very well for actual motion sickness.
If they haven't spent time in the RV, bring them in it and let them explore. Let them nap in the RV. Make note of where they choose to hang out. My Looney1 prefers hanging out on the backs of the dinette seats - where he can see and be a part of everything. Looney2 prefers to be up in the cabover bunk - where he can hide when scared or look out and still be out of reach or get tummy rubs from me without having to come down. Knowing that helps me figure out what they want when traveling. Looney1 wants to see everything, Looney2 wants to be tucked away and hidden.
One thing I do for the safety of the cats: they both wear a harness from the time we leave home until we return. During the travel, at the campground - 24/7. On the harness I have attached an ID tag that includes my cell phone number and my vehicle/RV plate numbers. Most campgrounds I visit don't have cell service. If the cat gets out and someone finds them, they can locate me in the campground via the plate numbers. They are also microchipped. But the ID tags are the quickest way for them to get back to me if they get out in a campground.
I also always feed them canned food twice a day. Opening that can of cat food can convince a cat to come back to the RV. Most all my cats have come running for canned food and they know they get it in the morning and at night, so they will come around at those times in anticipation.
1975 American Clipper RV with Dodge 360 (photo in profile)
1998 American Clipper Fold n Roll Folding Trailer
Both born in Morgan Hill, CA to Irv Perch (Daddy of the Aristocrat trailers)
