I’ve made a major blunder whilst hot coating the deck of my first timber hollow board. I’m using epoxy. I brushed it on to the deck and it looked ok, but an hour later it had gone all pitted and wavey. It hasnt delaminated, but there are areas which are still sticky (toffee like) even after 4 days. I did the bottom of the board and its perfectly smooth. Any suggestions as to how I rectify the problem? I want to sand it back and start again but the sticky patches are the problem. Silly question, but could I put some hardner onto these area? Any thoughts on this?
I’m sure that there is an easier way, but I’ll pass on my disaster correction. I used a hair dryer and a scraper. After I got most of the non set up epoxy off, I went through a BUNCH of sand paper. FYI, It was MY board that I didn’t mix up well enough! http://www.hdxsurfboards.com
Jeff has it exactly right. Always be sure to THOROUGHLY mix epoxy. It is not a catalytic reaction like polyester so each part (resin and hardener) has molecules that must react with the other part. It’s called an addition reaction. If they don’t get together they won’t kick. Thorough mixing is the solution and an easy one at that. We use big paint stir sticks, they do a better job than tongue depressors. One good thing about having this problem… you won’t ever do it again.
thanks guys. I wont that mistake again. I’m off to the shed to scrape and sand.
some other possibilities…temperature,most epoxies dont respond well under cold conditions …humidity epoxy hates any kind of moisture, if its moisture youll get milky patches …also the timber itself ,some woods have oils in them that stop the resin setting properly especially around knots in the timber .the fact that the job pitted and went wavy also indicates some reaction to impurities like wax or oil so maybe ,dirty working conditions as in wax on your stands off secondhand boards …or the oily timber …but either way the remedy is the same, sanding ,scraping ,swearing and more sanding …then off for more sandpaper… BERT…
Bert, These problems were (or are) more indicitive of older straight chain amine systems. Newer cycloaliphatic amines generally don’t have these problems. They also have lower vapor pressure, better finish and much lower toxicity. They are more expensive to produce but, in my estimation, are worth the cost. Also, Additive F which is produced by Resin Research elimiates nearly all climate related problems and increases Barcol hardness which dramatically improves bond between layers and sanding. Sorry about the spam guys.
Bert, Greg This is a pig of a job. I’ve been sanding, scraping and hairdrying for a day or so with slow results. To add to the pain I’m being attacked by a plague of mosquitos! My shaping environment is not the most sterile! I am punishing myself for this mistake. I’m taking it back to the bare plywood, its the only way and then reglass the deck. I have made a spiritual date to ride this baby on some beautiful waves in Margaret River in Western Australia, so I have 2 weeks to solve my problem.
i had to laugh …sorry gray ,i do know that pain to well, if your in west oz look me up im just up the road from margrets …also greg sounds like you know your stuff …im interested in the resins you speak of ?when you said something about straight chained amines .was that anything to do with how the polymers cross link as they set??? and do your resins cross link better or something???because i presume they would have to if they have better barcol hardness …can i get some data sheets from you ?? ok hope something happens … regards BERT
I know your pain…Welcome to the club… http://www.hollowsurfboards.com
Hi Bert, It happened that after reading Greg’s bit featuring cycloaliphatic amines ( god, I love it when he talks chemistry ) I was curious and did a little research. http://www.epoxyproducts.com/chemistry.html has some descriptions, http://sunilbhangale.tripod.com/epoxy.html has some descriptions with rather badly scanned diagrams, http://www.epon.com/resins/am/pdf/SC2357.pdf somewhat better diagrams, very technical, mostly concerning low temp (
Straight chain aliphatics don’t contain certain chemical characteristics that cycloaliphatics do. They are less stable and generally more reactive which leads to the higher toxcicity and reactivity with airborne moisture which causes amine blush. The amine reacting with this moisture causes a bicarbonate that forms on the resin surface during cure cycle. This blush reduces Barcol and also makes washing nessesary before recoating. Our cycloaliphatic hardeners reduce this as well as does some of the other formulating processes we use. Additive F eliminates what’s left of the blush by creating a moisture barrier on the resin surface. We are presently negotiating with an Austrailian distributor. We hope to have something in place in a couple months.
Bert, send me your e-mail address and I’ll send yopu some info. I’m .
Greg, Is there any strength advantage with the newer epoxy? I’m not making wooden boards. I use a very generic epoxy over EPS, prime and paint them. I’ve found this to be very durable. I don’t worry too much about the cosmetic properties of the epoxy. Any reason for me to use the newer stuff? Thanks for sharing your knowledge. I’ve learned heaps from reading your posts.
Bert, If you see a guy with a wooden board either at Yallingup, Grace Town or Margies on the long weekend, thats me. I secretly hoping for a relatively small for the maiden voyage of my first home made board.