Thought this might be of interest…maybe others have encountered this same dilemma…
I recently replaced my car, but the keys that came with the new car were quite different to the old one. The old one was recent enought to have an engine immobiliser and a transponder key, but the key was separate to the remote keyless entry thingy, and it was a waterproof molded block of plastic. I had been stashing this key in my wetsuit for the past 10 years, and never had a problem with the car not starting, with the transponder electronics safely enclosed in their plastic housing.
However, the new car came with keys that looked like this:
[img_assist|nid=1066076|title=A modern transponder key for a new vehicle|desc=|link=none|align=left|width=632|height=640]
An all in one unit that is probably barely splashproof, let alone waterproof. So I needed to find a surf key that was just like the old car had, but it turns out that there is nothing like what I was after. Yes, I could get a key cut that would open the door, but I wanted one with a transponder chip that could also start the car. The closest thing I could find was this key on eBay.
[img_assist|nid=1066077|title=Almost a surf key, but not waterproof|desc=|link=none|align=left|width=640|height=640]
So I bought it for $25 and had it cut for another $45 (still much cheaper than what the dealer wanted for the same thing!). Then I programmed the transponder chip so it could start the car (my car manual had steps for how to do this, I know other brands try to force you back to the dealer for them to do this for you for $$$). So now I had a key that could open my doors and start my car, but as it consisted of two clipped together halves, it was far from waterproof.
So I made a basic mold out of an old matchbox that I had lined with sticky tape and sealed as best I could. I then cast the key into the block of epoxy resin (Kinetix surfboard laminating epoxy to be precise!). When it had cured, it looked like this:
[img_assist|nid=1066078|title=Casting the key into a block of epoxy|desc=|link=none|align=left|width=480|height=640]
As I said before, the key wasn’t waterproof, and it certainly wasn’t resin proof. Over the first hour or so of having the key in the mold, the resin level dropped noticibly as resin seaped into the key, so I had to keep topping up the mold. As for resin getting inside the key, that’s no problem because electronics are often made water/dust/tamper-proof by casting them in epoxy.
I then got out the belt sander and rough cut the block to slightly larger than the key. Yes there are lots of micro air bubbles 'cos I whipped the epoxy too much. But I’ll deal with that later.
[img_assist|nid=1066079|title=Rough shaping with the belt sander|desc=|link=none|align=left|width=640|height=480]
Then I finished grinding it back to the final shape with a hand sanding block, and used a Dremel to buzz out the hole for the key loop in my wetsuit.
[img_assist|nid=1066080|title=The shaped surf key|desc=|link=none|align=left|width=640|height=480]
I wasn’t altogether happy with the final finish, mostly due to some air bubbles, so I filled a few little divets with 5-minute epoxy, then sprayed the key with a black vinyl paint (quality 3M Vinyl paint, if Resinhead is reading!), and gloss coated (WTF, who gloss coats a car key?!)
[img_assist|nid=1066081|title=Gloss coated|desc=|link=none|align=left|width=480|height=640]
So there you have it, a non-waterproof transponder key made into a waterproof surf key. And it works perfectly, starting the car every time!
Cheers
Paul
