: I'm building a completely composite kayak, and I layed the first couple
: layers of fiberglass on it on sunday. I'm working in my garage, the
: temperature was a little chilly, about 50 degrees. Sunday night it rained
: pretty hard, and got a bit colder. It's been between 30 and 45 degrees
: since then. I used about 1.5% catalyst in the (polyester) resin mix, an
: amount that should have caused the stuff to cure in about an hour, if the
: book I have is right. Now, 2 days later, the resin still isn't hard, but
: it's not very tacky either.

: Will it fully harden if I let it sit?

No, it probably won't. But that is OK. Polyester resin stays tacky if it is exposed to air. You need to seal the final surface with some air-blocking material. In the mean time, if you are planning to add layers of lass, go right ahead. that slightly tacky surface will bond nicely withn the next coats of resin you apply.

Some types of polyester resins have waxes dissolved in them. As the polyester "hardens" its molecules link and cross link during the polymerization process. this forces out the wax, which is squeezed out onto the surface of the resin, where it forms an airtight barrier under which the resin can harden. It might take a day or so for this to happen, so if you apply a second coat soon the waxes just float up a bit higher. If you wait more than a day, though, you'll hae to sand the surface before you apply the next coat of resin.

If your resin is still tacky on the surface I suspect you have a variety which does not have wax in it.

:Is there anything I can do to speed the process up? add more catalyst. There should be a chart showing how much catalyst to add based on your working temperature and the desired potlife. Generally, the colder your ambient temperature, or the faster you want the resin to kick, the more catalyst you add. There is not a very large range, though. You'll typically be in the area of 1/2 % to 3 % mixtures.

: I was thinking of maybe : spraying some extra hardener on the surface, but
: that seems pretty drastic.

Don't do that. Not only is the catalyst (hardener as you call it) a really nasty chemical, but the amount normally used is so small (about 1%)that spraying it on would be a potential disaster. I doubt you could spray it on thin enough, and the overspray would make you sick.

:Since I dont have any way of controlling the
: humidity/temperature, what can I do for my future layers so that they'll
: harden faster? Do you have to use more catalyst in cold temperatures or
: when the air has high moisture content?

Either that or warm up the shop. You can just heat the area around the boat by hanging a plastic tarp over it and heating the enclosed area with to 100 watt lightbulbs (1000 watts of radiant heating) or use an electric hairdryer to move heated air under the plastic tent. You want to try to get the temperature as close to the range of 65 to 75 degrees as you can for best results.

: One other thing, A guy at a local fiberglass repair shop said to just put the
: layers on one right after the other, that it's not necessary to wait for
: them to cure. Could that be my problem?

You might want to try his idea.

Here is another stroy on using polyester resin you might want to read:
http://www.capndsboatshed.com/fiberglassmaterials.htm

Hope this helps

PGJ

http://www.capndsboatshed.com/fiberglassmaterials.htm