... I used to do that. There were kites that needed a crane to relaunch. The logic is correct but I think the only measurable benefit, I felt, is that it helped keep the kite cleaner. We get some muddy crud on our kites when going bayside.
A cheaper/easier version is the tent spray at Walmart - about $5 aerosol can .. or 303 Fabric Guard .. or IOSSO Water Repellent. Don't expect much longevity from these. The best ones are 'heat set', like NIKWAX. Their resins fuse/bind with the fabric, mineral oils, not so much. Do not try heat setting in a big commercial dryer. I did that. The kite ended up nice and crispy, but 30% smaller ..in spots.
I don't do any of that anymore, but you should. Maybe there are some new results to be had. Good luck with it.
Okay, the issue I have is crashing my kite on the water then returning to the beach shortly thereafter.
After landing the kite on the beach the LE is covered with sand 'cause it's wet. I don't want to leave my kite baking in the sun while waiting for it to dry and don't want to deflate and roll-up while still covered with sand. What to do? In my case I carry the still inflated kite off the beach to a spot where I have a large tarp nailed to the ground. I then either let it dry (in the shade) or spray with water from a garden hose to remove sand and then dry.
Anyway, the issue is it's takes a long time for the LE to sufficiently dry where the sand will no longer "stick" to the surface.
Why can't kite manufacturers use a quick-drying fabric or coating on the LE?
Meantime, has anyone used any of the products previously mentioned on this thread or something else that can be sprayed on the LE to enable quick-drying?
I've used neverwet on an e-z up 12x12. I would say that the square footage of this canopy would be similar to 8/9m kite?! Anyway. I needed 2 cans to cover the canopy. It dries up a bit hazy/milky, definitively not clear, and it feels a bit sticky. Yes, water pearls off nicely, but exposure to UV destroys its magic fast; I would say within 14 days. So, overall, would I use it on a kite? Naw. I think one would need 2 to 3 cans to cover it, befriend the haze and do it all over after a month for ~$60. I agree, water launch is a bitch. So, curse at your kite. It gets afraid and may turn over easier ...