Is that why the Windsor Rapids don't have flys???
We thought we'd go buy a stack of waterproofing spray for ours after we season it ......To help stop leaks.
Not sure about the canvas on the new van, but on our 2009 Expanda the canvas was 100% waterproof, very effective, and probably 10oz. I "Seasoned" it and sealed the seems where they tampered with it by cutting and sewing. It never leaked a drop in 5 years with some testing weather during that time. The new canvas is definitely not as heavy .... but Im hoping Jayco hasn't cheapened that up, and the new one is a similar quality and type.
Jayco dont do themselves any favours by not actively informing people of the limitations and requirements of canvas. The canvas on our 2009 was high quality, fantastic, 99% waterproof and Jayco did a great good with it .... but thats where it falls apart. There was a lot of people complaining the Expanda's leak because Jayco never bothered to learn them up.
Tents, even good ones (including Expanda ends) all leak when new. A tent that never leaked or leaks is as common as a Unicorn. The process of sewing creates a hole by a thick needle, left filled by a much thinner thread. The thread is generally not water proof and will wick the water by drawing it through the looses holes creating by the larger needle. The wet thread will then quickly soak any zipper material, other material and anything else touching it.
Canvas "Seasoning" isn't about the canvas, its the process of closing the needles holes around the thread by the intentionally, artificially and repeated soaking and drying, soaking and drying etc etc new canvas seams over a short period. The repeated soaking and drying shrinks the sewing holes in the canvas around the thread and reduces the wicking, more often than not to nothing. The newer the canvas and the more repeated and effective the soaking and drying ..... the better the "Seasoning".
Take out the vans mattress, and get that damn hose and soak that canvas as much as possible, especially the seams and stitching. If your not getting some moisture through to the inside of the van, your not trying hard enough.
A warm day is the best time to do it, because the cycles are more effective and shorter. "Seasoning" is most effective on new canvas; trying to "Season" older canvas thats already seen some weather will not be as effective. Wetting the canvas during the "Seasoning" is not like replicating rain ..... its more like trying to drown it.
After you've Seasoned the canvas, get a pump pack of NikWax UV Proof (NikWax is the best waterproofer in the cosmos ... according to me). Pour the UV proof into the container, throw the pump pack in the bin. Using a small paint brush, work the UV Proof onto the all the seems, paying particular attention to the zipper material. NikWax UV Proof looks like milk and you can't put too much on. If it starts to run just wipe the excess with a rag. You don't need to paint or treat he canvas itself.
STOP THE PRESS .... The UV Proof isn't on the NikWax website, I need to find out what the replacement product is for my new Expanda, and Ill post that later.
This is a pretty graphic pic of a so called typical "Sh*t built, pox, leaking, Jayco Expanda" ......... the 100% water proof Jayco canvas is happily and clearly holding its own, and you can clearly see the stitching wicking the water and soaking everything ........ everything, except for the actual canvas. Damn sh*t leaking Expanda's .......... never really leaked at all (well, at least the older ones. I about to find out if the new ones are the same)
That spray-on water proofing needs to be constantly re-applied to be effective. Quality manufacturer proofed canvas, will retain it water proofing for many years without any additional attention. Ive never used the spray-on stuff myself; Id be a bit concerned that the components of spray-on stuff might kill the manufacturers proofing in the process .... and you'll end up having to water proof it all the time.
All that said ....... Ill have to wait to see if the new Expanda canvas is as good as the old
Hope this helps