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#1
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Polyester or Epoxy?
I would be real interested inknowing how you would apply 1/4 oz of MEKP
to 6 or 8 square feet of cloth. ;-) I use polyester for molds and things like shower basins and grey water tanks but compared to epoxy it is a PITA. A quart of resin requires something between 5 to 10 ml of MEKP depending on the temperature, the hunidity and the phase of the moon. A ml to much and it turns to gum before you can get the glass laid tight. If you don't mix it extremely well it forms jelly beans in the pot. If you are an ounce short you still have to mix a pint because it is almost impossible to measure that small amount of MEKP. With epoxy you just get a squirt of resin and a squirt of hardner and you have about half an ounce. If it is hot you use a slow hardner. If it is nice out you use a normal harnder. If it is cold you use a fast hardner. But it is always a squirt of each. IF you need a lot the hardware store sell graduated mixing pots for about $.75 that are good for several sessions. IF you don't glas very often, epoxy has a shelf life measured in years. I have never had a can of polyester make it past 9 months after it is opened. William R. Watt wrote: Backyard Renegade ) writes: Let me take a minute for anyone who is not clear about mixing the two products. Epoxy is risky to work with because the proportions have to be exact and the mix has to be thorough. If it isn't done correctly the mistake cannot be corrected once is it on the hull. Polyester proportions do not have to be as exact or the mixing as thorough. If the polyester doesn't cure on the hull you can brush on more catalyst. I have spread uncatalysed resin onto a small plywood hull and let it soak into the wood for 24 hours before brushing on second catalysed coat. After allowing another 24 (acutally 18) hours to cure it was thorougly cured with a good bond into the wood. Uncatalysed polyester thickened with whatever can be used for filleting which allows unlimited time to shape and smooth the fillets. Then fibreglass cloth soaked in catalysed resin can be put over the fillet and the whole thing will cure. In my opinion polyester is both easier and safer to work with. For some reason the last polyester I bought doesn't even smell as it cures. It may be an environmental thing. In some jurisdictions licenced boatbuilders are not allowed to let gases from curing resins escape into the atmosphere which has lead to fans and filters being installed and to a technique which looks like a dry vacuum bagging setup with injected resin. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-freenet email must have "notspam" in subject or it's returned -- 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 |
#2
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Polyester or Epoxy?
Glenn Ashmore wrote:
I would be real interested inknowing how you would apply 1/4 oz of MEKP to 6 or 8 square feet of cloth. ;-) I use polyester for molds and things like shower basins and grey water tanks but compared to epoxy it is a PITA. A quart of resin requires something between 5 to 10 ml of MEKP depending on the temperature, the hunidity and the phase of the moon. A ml to much and it turns to gum before you can get the glass laid tight. If you don't mix it extremely well it forms jelly beans in the pot. If you are an ounce short you still have to mix a pint because it is almost impossible to measure that small amount of MEKP. With epoxy you just get a squirt of resin and a squirt of hardner and you have about half an ounce. If it is hot you use a slow hardner. If it is nice out you use a normal harnder. If it is cold you use a fast hardner. But it is always a squirt of each. IF you need a lot the hardware store sell graduated mixing pots for about $.75 that are good for several sessions. IF you don't glas very often, epoxy has a shelf life measured in years. I have never had a can of polyester make it past 9 months after it is opened. Absolutely. I've done a bit of aircraft fiberglass work, but I've bever built a glass hull. http://home.flash.net/~lamb01/cowl.htm I use large syringes from the vet for mixing. My resin mix is 6:1 by volumn. 60cc of resin in the big shot. 10 cc of hardner in the little one. Its easy to double that with two shots of each. But that's about as much resin as I mix in one cup. For large layups, I premix 140cc in baggies and put them in the fridge. I don't mean to step on any toes, but since this is a boat building forum... West is a commonly recognized epoxy but imho West is NOT a sutable laminating resin for making fiberglass parts. It's fabulous with wood. But the mechanical properties are low and glass parts tend to be brittle. I've used Dow 330 for years, but can't get it any more. Now I mostly use AeroPoxy. There are several inexpensive laminating resins listed in Aircraft Spruce. There are some expensive resins listed too! Glassing wood? West is best. But for glass or carbon parts, there are much better resins. Richard Just my opinion, I could be wrong. |
#3
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Polyester or Epoxy?
Richard Lamb wrote: I don't mean to step on any toes, but since this is a boat building forum... West is a commonly recognized epoxy but imho West is NOT a sutable laminating resin for making fiberglass parts. It's fabulous with wood. But the mechanical properties are low and glass parts tend to be brittle. I've used Dow 330 for years, but can't get it any more. Now I mostly use AeroPoxy. There are several inexpensive laminating resins listed in Aircraft Spruce. There are some expensive resins listed too! Glassing wood? West is best. But for glass or carbon parts, there are much better resins. That is correct. That is also why West has a sister line called Pro-Set which is a laminating epoxy. -- 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 |
#4
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Polyester or Epoxy?
Glenn Ashmore wrote:
Richard Lamb wrote: I don't mean to step on any toes, but since this is a boat building forum... West is a commonly recognized epoxy but imho West is NOT a sutable laminating resin for making fiberglass parts. It's fabulous with wood. But the mechanical properties are low and glass parts tend to be brittle. I've used Dow 330 for years, but can't get it any more. Now I mostly use AeroPoxy. There are several inexpensive laminating resins listed in Aircraft Spruce. There are some expensive resins listed too! Glassing wood? West is best. But for glass or carbon parts, there are much better resins. That is correct. That is also why West has a sister line called Pro-Set which is a laminating epoxy. -- 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 Thanks. Haven't seen that one on the shelves tho. Mostly just West 105. |
#5
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Polyester or Epoxy?
Hey Richard, just out of curiosity for the polyester crowd, how many
aircraft builders, hobby and commercial do you know of that ust polyester? regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. |
#6
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Polyester or Epoxy?
Ron Thornton wrote:
Hey Richard, just out of curiosity for the polyester crowd, how many aircraft builders, hobby and commercial do you know of that ust polyester? regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. Not a single one anymore... Even most of the kit manufacturers have changed over to epoxy. OTOH, there is a growing use of vinyl ester resin. It is catalized and works a lot like polyester, but with better chemical resistance and much better physical properties. Richard |
#7
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Polyester or Epoxy?
It should be recognized that compared to boat builders, the airplane crowd
really throws money at a project. (Yeah, I know it is hard to believe there is an easier way to dispose of excess funds than boating.) The cost of epoxy over polyester is really not a major factor. While a Sevtec surface effect vehicle (or sev) may cost the builder about $4000 minus for a 4 place, 30mph over water 25hp garden tractor engined machine, the airplane builders spend maybe $40,000 and way up, more than half of that sometimes just on the engine. Also, skins on aircraft are very light, you cannot walk on them. Boats must have a much more substantial build, due to this and vastly higher point and overall loading, so the quantity of resin is far more significant. (Sevtec does use vinyl ester resin on a manufactured craft, though, primarily as it is claimed (though maybe not proven) that moisture penetration is less than cheaper resins. Of course, boats use epoxy for the same reason, maybe a single coat near at and below the waterline. Subject: Polyester or Epoxy? From: Richard Lamb Date: Sat, Jan 17, 2004 11:10 AM Message-id: Ron Thornton wrote: Hey Richard, just out of curiosity for the polyester crowd, how many aircraft builders, hobby and commercial do you know of that ust polyester? regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. Not a single one anymore... Even most of the kit manufacturers have changed over to epoxy. OTOH, there is a growing use of vinyl ester resin. It is catalized and works a lot like polyester, but with better chemical resistance and much better physical properties. Richard BRBR Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A |
#8
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Polyester or Epoxy?
Dunno aboput that, Barry.
My new plane cost me about $6k US. But then I made most all of the parts rather than buying parts. Makes a difference. Richard Barry Palmer wrote: It should be recognized that compared to boat builders, the airplane crowd really throws money at a project. (Yeah, I know it is hard to believe there is an easier way to dispose of excess funds than boating.) The cost of epoxy over polyester is really not a major factor. While a Sevtec surface effect vehicle (or sev) may cost the builder about $4000 minus for a 4 place, 30mph over water 25hp garden tractor engined machine, the airplane builders spend maybe $40,000 and way up, more than half of that sometimes just on the engine. Also, skins on aircraft are very light, you cannot walk on them. Boats must have a much more substantial build, due to this and vastly higher point and overall loading, so the quantity of resin is far more significant. (Sevtec does use vinyl ester resin on a manufactured craft, though, primarily as it is claimed (though maybe not proven) that moisture penetration is less than cheaper resins. Of course, boats use epoxy for the same reason, maybe a single coat near at and below the waterline. Subject: Polyester or Epoxy? From: Richard Lamb Date: Sat, Jan 17, 2004 11:10 AM Message-id: Ron Thornton wrote: Hey Richard, just out of curiosity for the polyester crowd, how many aircraft builders, hobby and commercial do you know of that ust polyester? regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. Not a single one anymore... Even most of the kit manufacturers have changed over to epoxy. OTOH, there is a growing use of vinyl ester resin. It is catalized and works a lot like polyester, but with better chemical resistance and much better physical properties. Richard BRBR Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A |
#9
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Polyester or Epoxy?
This is an epoxy plane? My first "plane" cost me $10.98, 1960 prices, it would
be much higher in 2004 dollars. Look at the Sevtec website and follow the links. No epoxy or polyester was in ght, and I used a free engine, gravity. Subject: Polyester or Epoxy? From: Richard Lamb Date: Sat, Jan 17, 2004 4:27 PM Message-id: Dunno aboput that, Barry. My new plane cost me about $6k US. But then I made most all of the parts rather than buying parts. Makes a difference. Richard BRBR Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A |
#10
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Polyester or Epoxy?
Well we all hear quite a bit about the evils and wonders of both
polyester and epoxy. But what about vinylester? Any one ever use that? I'm curious because I saw a vinylester/kevlar canoe prototype by Mad River Canoes that was 20 years old, light as a feather and showed hardly a scratch though it had been dragged through gravel for years SteveJ Richard Lamb wrote in message ... Ron Thornton wrote: Hey Richard, just out of curiosity for the polyester crowd, how many aircraft builders, hobby and commercial do you know of that ust polyester? regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. Not a single one anymore... Even most of the kit manufacturers have changed over to epoxy. OTOH, there is a growing use of vinyl ester resin. It is catalized and works a lot like polyester, but with better chemical resistance and much better physical properties. Richard |
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