A long time ago I recoated a kite using silicone rubber diluted in turpentine. The intention was to improve the rather dismal waterproof state of the kite. The silicone rubber achieved that quite well and in addition made the kite hydrophobic!, dirt repellent and much more air tight. From memory I think it added about 200 grams to a 17m kite. Silicone is not a particularly strong material. I postulated that Shoe Goo, which is actually Styrene Butadiene Rubber, a much stronger and flexible rubber than silicone would be a better coating. Someone on foilzone picked up on a bit of this and actually threw silicone rubber and Shoe Goo, with some other coatings as well like PU foam into a grand test. His testing methodology was quite thorough, involving weathering and durability tests and also scientific with a home made porosity meter. What surprised me was silicone rubber got eliminated quite early, as I had already found it quite good. Then also PU foam got eliminated as it developed cracks that leaked, somewhat surprising as it was touted as being very good on various french forums, but even in my own tests I could see a cracking problem and of course the PU coatings on flysurfers are horrible, with peeling and flaking. He narrowed it down to 2 candidates at the end, Shoe Goo and an unnamed product. Yet to reach his final conclusions he was already quite impressed with both, but then foilzone fell into a black hole.
I already knew about Shoe Goo, but he enlightened me how to thin it, easy enough if you read it's sds I guess, the solvent is toluene. Reading on the net you will quickly discover many people are thinning Shoe Goo or it's derivatives for the purposes of gluing or waterproofing. It is actually sold under many different names with merely different concentrations for the uses of sealing seams to gluing shoes and everything in between. Recently I discover E6000 a thinner 30% solids formula of Shoe Goo, and it is great for gluing patches on kites and fixing wetsuits and many other things. I started a thread about it viewtopic.php?f=1&t=2392220&p=925144
. Though I think I will make my own lighter dilution from shoe goo for glueing patches now.
Anyway I have a 8m kite, very used and quite old ,porosity of the fabric can only explain its bad behavior. So I decide to coat it with Shoe Goo. I clean, rinse, fly, dry the kite to get as much sand as possible out of it. I inflate the kite with a fan on a plastic tarpaulin and hide the bar and what ever bridles I can under the kite. One tube of shoe goo is 109.4ml with a specific gravity of 0.898 so 98grams. I squeeze about 45 grams out into 100ml of toluene and its already about half the tube so I stop. I mix it well then add a further 350mls toluene for a 1 to 10 ratio. I coat with a spray gun one side of the kite recoating a few times on the tips which I know the coating is peeling everywhere inside and any trouble spots like repairs etc. Preparing the next mix for the other side I was only just able to squeeze 46grams out of the tube :-/ The toluene evaporates within a minute so I just let the kite dry while I mixed the next lot and while I packed up.
The kite has quite a shiny metallic appearance with it much more so on the tips where I applied more coats. The fabric has a plastic feel to it and is quite crunchy like new kite fabric or even more so. Which I didn't expect because the silicon coating is not like that. It may be something to do with the PU inside bonding to the shoe goo. I haven't fully tested the waterproofing as that is not my main focus, but if it is thick enough It will prevent the fabric absorbing water obviously. Flying the kite I already notice it intakes air much easier setting up and the general behavior seems much improved. Oh and it smells like a new pair of shoes lol
I did some tests before and after. Pegging the tips shut I inflated the kite and let it deflate taking some very rough estimates at different times about it's inflation level
before I got
12min 50% deflated , 30min 80% deflated , 40min 90% deflated
after I got
10mins 20% deflated , 25mins 50% deflated , 50mins 70% deflated
I also weighed the kite with bar and bag before 3.67kg and after 3.66kg. Which I guess the kite dried and lost more sand in the weeks between measurements and when preparing just before spraying, oh well. Shoe goo is 46% solid by weight so 91grams wet becomes 41.8g and I wasted anywhere from 10to50% ,air spraying has a lot of bounce and the droplets don't stick, so the added weight could be anywhere from 21g to 38g. Not much considering the results. I wish I had weighed it just before spraying though to know exactly. I think when and if I do it again I will double the application rate to 2 tubes per 8m of kite and drop the dilution to probably 8 or 7 to 1. I will probably get an airless sprayer to use as well. But so far I am quite impressed and I can always coat again, but removing would be tricky