Thursday, May 14, 2009

My bad...

I have spent a few hours scraping off the layer of epoxy that was peeling from the side panels. Once I have scraped as much as possible I will do a sanding. The probable cause of the defective last coat was suggested to be one of two possibilities. John C. Harris, the Pocketship designer, explained it was either a bad mix of epoxy where the resin/hardener ratio was off or a result of surface contamination. Quoting him: "Surface contamination can result from wiping down with a rag that has fabric softener or grease in it, a microscopic rain of silicone lubricant from an overhead garage door; a heavy falling dew just before the last coat; or use of a solvent other than denatured alcohol or lacquer thinner". 
I don't think it was a bad mix because I would have had to do a bad mix 3 or 4 times. But it was drizzling out and the air was very damp. It was somewhat reassuring that I am not the first person it has happened to and these little setbacks are all part of the boatbuilding adventure.
It is ironic that the problem last coat was from me being extra careful and doing 4 coats instead of the normal 3. Once this mess is finished I have some fillets left to do and then I can move on to fiberglassing the inside of the hull. But NOT if there is even a hint of rain!

1 comment:

John C. Harris said...

Don't get hung up on the humidity thing! MAS epoxy is really very good with humidity, but there must have been actual moisture on the hull surface, if in fact that's the problem in the first place.

No problem if it's raining outside---just don't leave the garage door open if it's raining and you're doing surface-coating operations.