>...heat generated by the epoxy, it kicked off like a chain reaction and >produced a very hot, softball sized but mostly air filled ball above the hole.
AKA a exothermic reaction. The worst exothermic reaction I was involved with was back in the 70's when I incorrectly set a warming oven to 250F instead of 100F. I had two gallons of a two part polyurethane potting compound turn into a smoken' basketball size fire hazard. I ran it into the parking lot and dumped into some gravel. After it cooled we painted it up a little and named it. To avoid that type of exothermic reaction when mixing large (250 ml typical) batches of West Systems epoxy I have used several techniques. If it is cool outside (<60F) I use their 205 hardener. Don't add your body heat to the mixing container by holding it tightly in your hand. To add fillers, mix the resin/hardener quickly then start adding the fillers. The fillers absorb some of the chemical reaction's heat. Glass fibers or milled glass (powder) absorb more than microballons. If it is warmer to hot in the work space I used West Systems 206 hardener which is formulated for longer pot life in warm weather. In hot conditions with larger batches I have resorted to cooling the resin and hardener containers in ice water prior to mixing. When spreading / poring the mixed epoxy, quickly get some of the mixture out of the middle of the container and onto some part of the repair area that will absorb the heat. This is to help avoid the "smoken' hot ball" of epoxy. A wider / larger mixing container is also helpful to stay below the exothermic start point. If you are poring to fill a large void, poring in stages or adding some layers of glass cloth or mat to break up the large mass of resin is a good technique. The glass will absorb some heat and help prevent shrinkage and cracking. To date, we have used approx. 6 gallons of West Systems 105 resin and a mix of the equivalent 205 or 206 hardener on Calypso's deck rebuild. the typical batch is 2 to 3 "pumps" of the metering pumps. The biggest batches were up in the 10 to 12 pumps. For the big batches we had all the cloth laid out and ready to have resin poured on. We quickly got the resin out of the mixing container to avoid the exothermic reaction. With 3 to 4 layers of cloth and all that resin the heat could be felt on the skin a close to a foot away. Some of the fillers we use are: milled glass powder glass fibers / strands (approx. 1"long) West 405, 407, 410 branded fillers CaboSil (flamed silica) as an anti-slumping agent Most of our filler mixes get to the "peanut butter" thickness. For pouring into a void we go lighter on the fillers and work it to a "honey" consistency. We have used syringes to push epoxy into tight places. We have used vacuum bagging supplies and techniques to remove air and reduce the number of voids. If you pour resin into a hole it will likely "bubble" until it cures. We have sat around popping bubbles and re-filling. We have tried using a vacuum chamber to reduce bubbles from mixing. After +-300 holes filled we now just accept that some holes/voids will bubble enough to require a two step process. Martin Calypso 1971 C&C 43 Seattle ________________________________ From: CnC-List [cnc-list-boun...@cnc-list.com] on behalf of Charlie Nelson via CnC-List [cnc-list@cnc-list.com] Sent: Wednesday, April 13, 2016 2:56 PM To: cnc-list@cnc-list.com Cc: cenel...@aol.com Subject: Re: Stus-List C&C 29 Mk II Bulkhead Repair Be careful that whatever you do with the epoxy including adding fillers, etc. that what you are using it on, in or about has sufficient area to absorb the heat produced as the epoxy 'kicks off'. I build a wooden sailing dinghy using the 'stitch and glue (epoxy) and got pretty good with the stuff--so I thought! When I began an epoxy plus filler repair on a 1.5" x 4" x 1.5" hole in my deck, I learned quickly and fortunately without a fire, that one cannot fill such a whole in 'one go'! Without enough surface to absorb the heat generated by the epoxy, it kicked off like a chain reaction and produced a very hot, softball sized but mostly air filled ball above the hole. Had this repair been done similarly in a place where I could not easily reach it, there likely would have been a fire! Charlie Nelson Water Phantom cenel...@aol.com
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