I was reading about wood veneer laminating (research on vac bagging) and came across something that I thought was an interresting idea for cold weather glassing. They talked about putting a heating blanket over the vac bag to help with the curring process (in their case the glue).
Would there be any reason why this would be a bad idea if vac bagging a surfboard?
over night temps at my house are near freezing; current day time temps mid-60’s. Not ideal for epoxy.
good idea…
ever seen a mould with a heat blanket built in ???
can be sanding a resin within 2 hours , that normally has a pot life of 5 hours at room temperature…
regards
BERT
The only thing you have to watch out for is if your are starting with cold materials, when you heat up foam, the air in it expands and tries to get out. Wood can be a problem too but to a lesser extent.
trent !!! its in a vacumn…
regards
BERT
Hey 4est,
I once worked for a company that made electric heating blankets like you could find at Wal-mart. Here’s some handy info…if you drape it over the bag you’ll lose most of the heat generated rising above the blanket. You could use two blankets (one underneath) and use a much lower setting…or drape another less breathable cloth over it but it could overheat…or one underneath with a passive blanket on top to retain heat. You can buy a cheap digital thermometer and monitor what youre doing. I would not do it in an unsafe place (inside your house) as it can cause a fire. With normal use they are designed to heat safely into the mid 80s F but can get hotter on high settings…there’s some real advanced blankets that go for well over $100-200 but thats mostly the quality of the blanket (mtl, weave) and not the electronics.
How about an electric blanket below and a “space” blanket on top to reflect the heat? Prop up the edges to ventilate and control your heat levels. Gil
Bert, when bagging laminates and heating them to 100F I had problems with air forming bubbles in the resin. Sometimes fairly large bubbles, sometimes just a haze in clear laminates.
Now I just wait for the epoxy to gel before I do any heating.
that’ll work…
…if youre not making a huge board you can also use a king size blanket and use it to blanket both sides folding it over like a quesadilla
trent!! those bubbles add bulk to your laminate without losing strength …
in fact you get more strength through the thickness for the same weight …
if that foamy look or haze is hidden under a sandwich it wont matter …
regards
BERT
Epoxy laminates are adaquate at 30% resin ratios so a bit of air is not a problem unless it’s cosmetic. Polyesters resins, because or there poor adhesion qualities, have to run resin ratios at 55%, minimum. Under vacuum the resin does boil at a lower temperature so that’s probably some of what your seeing.
As for blankets, we did a project with the Navy on icebreakers that had to be repaired. They don’t bring those things to the tropics for repair and you can’t put them indoors. The solution we came up with was to sew magnets into the blankets that held them in place on the hull. They had to heat the area first for up to 24 hours before doing the repair and then after put the blanket over until the resin cured. Worked great.
Find yourself an electric fan heater or greenhouse heater (cheap), make a tent over the job from bubble wrap and seal the tent around the outlet of the heater, leaving the Inlet clear. Monitor the temp until you have a level that you are happy with, by opening up or closing the far end of the tent. We do this all the time at work for kicking off composite parts large and small. Heat your resin in the tent before you laminate too. Wouldn’t leave it unattended for too long, but at elevated temperature you job won’t take too long to go off anyway. Good luck.