first vacuum bagging experience
First off thanks to all the other builders who provided useful
guidance before I started this work. Today myself and couple of teenage helpers laminated up a small test piece (1/2 m2) that will also form part of my new cabin structure. Took 1 hour from start of laminating to having it under vacuum. Partly because neither my helpers had ever touched fiberglass before. Lessons learned, both positive and negative: - believe in my software. When it indicates that a layer of 666 gm/m2 triaxial will only be 0.7mm thick, don't make the rebate in the core 1.5mm "just to be safe" where layers overlap. I'd rather fill the little rebate with bog later than have to fair out a hill, but still I need to be a little less aggressive with the router. - a dry test run of my vacuum set up was highly useful. We found that the bag wouldn't seal well with any folds along the sealant tape - a digital scale was useful to measure resin/hardener easily. No mixing cups for this lad any more. - Corecell is harder than it looks. I made a nailing board (2x4 with a bunch of nails in it) to puncture the core. Had to really hammer it down into the core. I thought I would just be able to press it in... - Olfa rotary fabric cutters are amazing. If you're cutting any quantity of glass get one. - A resin with a slow gel time (90-120 min at @ 77F) makes things very relaxed. Cure time is 5-6 hours at 75F for my particular resin - pouring on the resin, spreading thinly with plastic spreaders, and then just working it in worked very well. The particular triaxial fabric (V2) and resin (Jeffco) wetted out very easily compared to others I've used. - yes, it's easy to get a 50/50 resin/hardener ratio. I measured out the same weight of resin + 10% for bleed. With my complete novice helpers we wet out 2 layers of cloth with lots left in the bucket, indicating that we were probably already at 50/50 before vacuum was applied. - overall a bit of careful planning made it all go very smoothly. One hiccup: The vacuum pump I'm using is a 6 CFM refrigeration tech. type. It draws a deep vacuum (27-29 in Hg) very fast (like 1 minute). But it is an oil lubricated type and exhausts an oily mist. We didn't notice it today with the garage door open, but when I came back after several hours the garage had a misty oily cloud in it. I figure the best solution might be to (a) vent the exhaust to a plastic bucket with some sort of breather material bunched in to capture the mist or (b) just exhaust it outdoors. Any suggestions?? Thanks all, Evan Gatehouse |
Exhausting the pump into a bucket of rags might be a fire hazard. Better to
exhaust it outdoors. A side-benefit will be that the pump will be quieter and it'll be easier to find bag leaks. My hearing is such that I need all the help i can get. "Evan Gatehouse" wrote in message ... First off thanks to all the other builders who provided useful guidance before I started this work. Today myself and couple of teenage helpers laminated up a small test piece (1/2 m2) that will also form part of my new cabin structure. Took 1 hour from start of laminating to having it under vacuum. Partly because neither my helpers had ever touched fiberglass before. Lessons learned, both positive and negative: - believe in my software. When it indicates that a layer of 666 gm/m2 triaxial will only be 0.7mm thick, don't make the rebate in the core 1.5mm "just to be safe" where layers overlap. I'd rather fill the little rebate with bog later than have to fair out a hill, but still I need to be a little less aggressive with the router. - a dry test run of my vacuum set up was highly useful. We found that the bag wouldn't seal well with any folds along the sealant tape - a digital scale was useful to measure resin/hardener easily. No mixing cups for this lad any more. - Corecell is harder than it looks. I made a nailing board (2x4 with a bunch of nails in it) to puncture the core. Had to really hammer it down into the core. I thought I would just be able to press it in... - Olfa rotary fabric cutters are amazing. If you're cutting any quantity of glass get one. - A resin with a slow gel time (90-120 min at @ 77F) makes things very relaxed. Cure time is 5-6 hours at 75F for my particular resin - pouring on the resin, spreading thinly with plastic spreaders, and then just working it in worked very well. The particular triaxial fabric (V2) and resin (Jeffco) wetted out very easily compared to others I've used. - yes, it's easy to get a 50/50 resin/hardener ratio. I measured out the same weight of resin + 10% for bleed. With my complete novice helpers we wet out 2 layers of cloth with lots left in the bucket, indicating that we were probably already at 50/50 before vacuum was applied. - overall a bit of careful planning made it all go very smoothly. One hiccup: The vacuum pump I'm using is a 6 CFM refrigeration tech. type. It draws a deep vacuum (27-29 in Hg) very fast (like 1 minute). But it is an oil lubricated type and exhausts an oily mist. We didn't notice it today with the garage door open, but when I came back after several hours the garage had a misty oily cloud in it. I figure the best solution might be to (a) vent the exhaust to a plastic bucket with some sort of breather material bunched in to capture the mist or (b) just exhaust it outdoors. Any suggestions?? Thanks all, Evan Gatehouse |
The bucket of rags, MIGHT be a fire hazard, but, I wonder if maybe that oil
mist might not be as explosive as the grain dust clouds that regularly blow up silos in the Midwest. Roger http://derbyrm.mystarband.net/default.htm "Jim Conlin" wrote in message ... Exhausting the pump into a bucket of rags might be a fire hazard. Better to exhaust it outdoors. A side-benefit will be that the pump will be quieter and it'll be easier to find bag leaks. My hearing is such that I need all the help i can get. "Evan Gatehouse" wrote in message ... First off thanks to all the other builders who provided useful guidance before I started this work. Today myself and couple of teenage helpers laminated up a small test piece (1/2 m2) that will also form part of my new cabin structure. Took 1 hour from start of laminating to having it under vacuum. Partly because neither my helpers had ever touched fiberglass before. Lessons learned, both positive and negative: - believe in my software. When it indicates that a layer of 666 gm/m2 triaxial will only be 0.7mm thick, don't make the rebate in the core 1.5mm "just to be safe" where layers overlap. I'd rather fill the little rebate with bog later than have to fair out a hill, but still I need to be a little less aggressive with the router. - a dry test run of my vacuum set up was highly useful. We found that the bag wouldn't seal well with any folds along the sealant tape - a digital scale was useful to measure resin/hardener easily. No mixing cups for this lad any more. - Corecell is harder than it looks. I made a nailing board (2x4 with a bunch of nails in it) to puncture the core. Had to really hammer it down into the core. I thought I would just be able to press it in... - Olfa rotary fabric cutters are amazing. If you're cutting any quantity of glass get one. - A resin with a slow gel time (90-120 min at @ 77F) makes things very relaxed. Cure time is 5-6 hours at 75F for my particular resin - pouring on the resin, spreading thinly with plastic spreaders, and then just working it in worked very well. The particular triaxial fabric (V2) and resin (Jeffco) wetted out very easily compared to others I've used. - yes, it's easy to get a 50/50 resin/hardener ratio. I measured out the same weight of resin + 10% for bleed. With my complete novice helpers we wet out 2 layers of cloth with lots left in the bucket, indicating that we were probably already at 50/50 before vacuum was applied. - overall a bit of careful planning made it all go very smoothly. One hiccup: The vacuum pump I'm using is a 6 CFM refrigeration tech. type. It draws a deep vacuum (27-29 in Hg) very fast (like 1 minute). But it is an oil lubricated type and exhausts an oily mist. We didn't notice it today with the garage door open, but when I came back after several hours the garage had a misty oily cloud in it. I figure the best solution might be to (a) vent the exhaust to a plastic bucket with some sort of breather material bunched in to capture the mist or (b) just exhaust it outdoors. Any suggestions?? Thanks all, Evan Gatehouse |
A cheap stethescope (sp?) truly helps here, especially if the pump is in
a different room (or outside) from the bagging room...and, yes, I can attest to Jim's poor hearing, as well mine, as we once worked together on several significant bagging projects ;-) - paul Jim Conlin wrote: My hearing is such that I need all the help i can get. |
I believe I would find a different vacuum pump. HVAC pumps are designed to
run a long time with almost no flow. With the constant flow from even a well sealed bag you run the risk of blowing all the oil out and burning up the pump before the epoxy kicks. You also don't need that high a vacuum. When you get much above about 15" Hg you run a risk of squeezing to much resin out of the layup. A pump rated at 24" Hg will give you plenty of headroom. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com " |
Glenn Ashmore wrote:
I believe I would find a different vacuum pump. HVAC pumps are designed to run a long time with almost no flow. With the constant flow from even a well sealed bag you run the risk of blowing all the oil out and burning up the pump before the epoxy kicks. You also don't need that high a vacuum. When you get much above about 15" Hg you run a risk of squeezing to much resin out of the layup. A pump rated at 24" Hg will give you plenty of headroom. I know but this pump is quite quiet (quieter than a vacuum cleaner). The first thing I did was check the oil level in the window on the pump when I went it and it hadn't budged. I suspect that a little oil goes a long way when it comes to making a mist. I did keep the vacuum level at 10-15" during the time the pump was running but thanks for the thought. Evan Gatehouse |
Vent the pump into a bucket 1/2 full of water. Put a couple of drops of
dishwasher detergent in the water to aid cleanup. You should test for foaming, but machine detergents shouldn't foam. John "Evan Gatehouse" wrote in message ... Glenn Ashmore wrote: I believe I would find a different vacuum pump. HVAC pumps are designed to run a long time with almost no flow. With the constant flow from even a well sealed bag you run the risk of blowing all the oil out and burning up the pump before the epoxy kicks. You also don't need that high a vacuum. When you get much above about 15" Hg you run a risk of squeezing to much resin out of the layup. A pump rated at 24" Hg will give you plenty of headroom. I know but this pump is quite quiet (quieter than a vacuum cleaner). The first thing I did was check the oil level in the window on the pump when I went it and it hadn't budged. I suspect that a little oil goes a long way when it comes to making a mist. I did keep the vacuum level at 10-15" during the time the pump was running but thanks for the thought. Evan Gatehouse |
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