Hey guys been doing some research on waterproofing for kites and have found sealnglide to probably be the best solution. I'm wanting to keep the salt and sand/dirt off my kite as much as possible when kiting and not have to wash my kite down after every session. I have noticed that if I wash my kite down after each session in fresh water and dry out it repels water and sand much better next session this is probably from the salt being washed off which next session will attract moisture and intern will attract sand and dirt too.....
I have an older kite over 1 year old and has had plenty of use - waterproofing should once again reduce salt/dirt or water from finding a home on the kite and will mean less washing after sessions. Other advantages are that sealnglide will seal the fabric rejuvenating cloth and also making the cloth hold air better improving performance. I use a foil so keeping salt and water off the kite has big weight and performance advantageous and should make pack up quicker and easier in salty/sandy places (e.g the beach!) 
This stuff retails for around $60 a bottle plus postage and can do approx 60m2 of kite area, I have a 10m and 4m foil which adds up to approx half the bottle used. If anyone would like to split the cost and use half the bottle it works out cheaper for both of us... anyone on the Gold Coast interested as I'm local to Goldie and would be ordering stuff from Briskites.
below is manufactures info on the product:
Holmenkol SEALnGLIDE Sail Coating
Item #: Homenkol_25200
Holmenkol SEALnGLIDE Homenkol-25200
SealnGlide is the ultimate performance lubricant finish, based on "nano" technology, for significantly reducing the friction of sail surfaces, resulting in tangible benefits such as:
# Faster sail setting - thanks to reduced friction
# Prevents sail snagging on rigs or fittings
# Increases cloth stability
# Use on bolt ropes for easy hoists
# Increases the sailcloth tear strength
# Resistant to sail washing detergents
# Reduced weight aloft - due to lower water absorption
# Non stick tell-tales - giving a clear advantage in competition
Used mainly on Sails, this unique system offers "nano" technology creating a slippery, water and dirt repellent surface glaze which also gives fungicidal and UV protection.
# Two Part Concentrate
# 100ML bottle
Have received the 2 bottles of sealNglide and used 1 litre of water with half of each bottle to coat 2 kites - a 10m pulse 2 foil and 4m windtools foil... I haven't been able to judge the result other than the kite feels slightly crisper and the colour of the kite looks shinier (less washed out) than before the treatment. The real test will come the next couple times I can get out on the water. Briskites use this product on all their school kites particularly their trainer kites.
I will update further as I get back on the water in the next week or 2 as the wind returns! If anyone wants the remaining half of the bottle leftover I will sell for $30 plus postage if you can't pickup, it's a small package that shouldn't cost much more than $5 to send locally.
