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#1
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Polyester or Epoxy?
"Meindert Sprang" ) writes:
Pleeeze guys, can someone explain to me what is so difficult about givin the resin pump and the hardener pump an equal number of pushes and stirring a mixture firmly for two minutes???? If one cannot perform such a simple task, I think building a complete boat is out of the question....... I tried buying a small quantity of epoxy packaged in twin pumps and had all sorts of difficulty with it. It never worked smoothly. It was messy. A lot was wasted. For the small jobs I use epoxy for I only buy it in the twin squeeze tubes now. I find it a lot easier counting drops of polyester catalyst than trying to measure out equal volumes of epoxy resin and hardener. Only one container is used for measuring with polyester. Overall easier to work with in my opinion. -- ------------------------------------------------------------------------------ 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 |
#2
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Polyester or Epoxy?
"William R. Watt"writes: I tried buying a small quantity of epoxy packaged in twin pumps and had all sorts of difficulty with it. It never worked smoothly. It was messy. A lot was wasted. For the small jobs I use epoxy for I only buy it in the twin squeeze tubes now. snip Stop by your handy dandy restaurant supply house and buy some plastic and/or paper cups. I use, 1 oz, 2 oz & 4 oz to mix small quantities of epoxy. It's simply NBD. -- Lew S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland) Visit: http://home.earthlink.net/~lewhodgett for Pictures |
#3
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Polyester or Epoxy?
"William R. Watt" wrote in message
... I tried buying a small quantity of epoxy packaged in twin pumps and had all sorts of difficulty with it. It never worked smoothly. It was messy. A lot was wasted. For the small jobs I use epoxy for I only buy it in the twin squeeze tubes now. I use the pump set from West. The easiest way to mix. One push on each pump and you have a smal dose of the perfect mix. I find it a lot easier counting drops of polyester catalyst than trying to measure out equal volumes of epoxy resin and hardener. Only one container is used for measuring with polyester. Overall easier to work with in my opinion. You can also mix by weight. I have used a digital scale for that. You pour, for instance, 100 grams of epoxy, followed by 20 grams of hardener. Easy. I would think that counting drops is a very unreliable method. the drop size would be very dependant on the viscosity of the calalyst, right? Meindert |
#4
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Polyester or Epoxy?
A number of years ago WEST printed a small article in their 'How To . . .'
magazine. {subscriptions are free, just call them}. It was on just this subject and included a couple of dimensioned drawings. The crux of the story/drawings was a method of employing 'stops' or 'steps' on the pump shafts. By cutting the shapes from some 1/4inch material and placing the proper 'end' between the pump 'head' and 'base', you can get a REPEATABLE '50 percent' or '25percent' pump. I used Hardboard and painted them each a different color and marked them. With the a 'full pump' discharging approximately 1 ounce of 'mix', I have the ability to also get 1/2 ounce and 1/4 ounce {approximately} quantities for those small projects/uses. I use the 5 to 1 formulation . . . and the set-up works just as well with my 'standard' RAKA epoxy. Regards & Good Luck Ron Magen Backyard Boatshop "Meindert Sprang" wrote in message ... SNIP I use the pump set from West. The easiest way to mix. One push on each pump and you have a smal dose of the perfect mix. SNIP |
#5
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Polyester or Epoxy?
"Meindert Sprang" ) writes:
I would think that counting drops is a very unreliable method. the drop size would be very dependant on the viscosity of the calalyst, right? not so it's noticeable. one drop of catalyst for every 1/2 teaspoon of resin. the drop squeezes out of a pinhole in a plastic container with a bit of thumb pressure. works every time for me. I'd be more suspect of the size of the pinhole but I've had no problems with it. -- ------------------------------------------------------------------------------ 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 |
#6
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Polyester or Epoxy?
I have mixed both epoxy and polyester for 35 years and have never had a
batch go bad. It ain't brain surgery. All you have to do is follow exactly the manufactures directions. I have to agree with Meindert, if you can't do that, you might want to think about whether you need to be building a boat with two part resins! Only an amateur would extrapolate to broad use the brushing on of catalyst over polyester resin already applied to glass as described by Johns for one boat. There is not a poly resin supplier in the word that would suggest such a thing because there is no way to predict what the final properties would be. As to epoxy, I have mixed batches from 1 gal. down to 6 drops. Yes 6 drops (5:1 West) off of popsicle sticks for RC model aircraft building. For larger batches I use any container of suitable size thats at hand and mark off the ratio with a rule. Gee I'm glad I passed 7th grade math. Allan, the bottom line is that it is historically well established thru industry testing, both lab and field, that epoxy is superior to polyester in most ways except price. No amount of anecdotal evidence or backyard observations as put forth by the polyester crowd will change that. Regards, Ron PS. Meindert, I learned to measure epoxy in the lab at GE a long time ago and was doing it on a balance scale until a couple of years ago I was corrected by Kern of System Three and several other chemist here. They all said that now the published ratios for the formulated resins are for volume only as the weight ratio can be different. I never had any trouble that I could detect but I do by volume ever since to assure max mech properties. I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. |
#7
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Polyester or Epoxy?
Ron Thornton ) writes:
Allan, the bottom line is that it is historically well established thru industry testing, both lab and field, that epoxy is superior to polyester in most ways except price. No amount of anecdotal evidence or backyard observations as put forth by the polyester crowd will change that. no argument there. the question is when do you NEED the superior qualities of epoxy? there are other questions about toxicity and so forth but the question that most interests me is when epoxy is NEEDED. I've used it as an adhesive in small quantities and to seal seams in some cases. If I used it instead of polyester and polyurethane on the small boats I've made it would double the price with no benefit I can imagine. everything has its place. I don't consider epoxy to be the only product to use. No amount of anecdotal evidence or backyard observations as put forward by the epoxy crowd will change that. -- ------------------------------------------------------------------------------ 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 |
#8
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Polyester or Epoxy?
No William, the question is are you qualified to make an informed
decision as to whether poly is good enough. I think not because I like many others here, none of use having any interest in selling epoxy that I know of, have worked with this stuff professionally for years at a technical and engineering level and I doubt that any of us would be willing to just look at all but the most obvious applications and know whether epoxy was needed instead of polyester. You can say poly is good enough all you want but the truth is that you don't really know. All we are saying is that with todays price difference it is more affordable than ever to go with epoxy and add an additional margin to a repair or build. Regards, Ron PS for the hovercraft guy. Build one correctly out of epoxy and see how long its service life is compared to the poly craft. I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. |
#9
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Polyester or Epoxy?
Longest is still in service after 18 Years, with no problems caused by use of
polyester resin glass skins over 4.5 lb "Clark Foam". These surface skimmers have been built with epoxy, and appear to be little different from the polyester, but possibly the elasticity of the panels is a little greater, (possibly due to inaccurate mixing) bad news when a lot of the structure is not governed by strength, but by stiffness. PS for the hovercraft guy. Build one correctly out of epoxy and see how long its service life is compared to the poly craft. I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. BRBR Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A |
#10
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Polyester or Epoxy?
*you* can say epoxy is necessary all you want but *you* just don't know.
you might think you are qualified but you don't have any application data to support your preference. what you have is material characteristics data and anecdotal application tales. before this question can be settled someone will have to do application testing. I doubt anyone would be interested. let me give you an example. the material characterisitcs of different paints are known, but the performance of different paints under different conditons are not. that is why the Post Office has to paint test mail boxes with the different paints and leave them outside for years to see how they perform. as an engineer with knowledge of the design and analysis of experiments you'll appreciate its more complicated than just painting and putting them outside. its not just the materials characteristics that matter. it is the combination of materials under varying conditions. polyester lives. long live polyester. Ron Thornton ) writes: No William, the question is are you qualified to make an informed decision as to whether poly is good enough. I think not because I like many others here, none of use having any interest in selling epoxy that I know of, have worked with this stuff professionally for years at a technical and engineering level and I doubt that any of us would be willing to just look at all but the most obvious applications and know whether epoxy was needed instead of polyester. You can say poly is good enough all you want but the truth is that you don't really know. All we are saying is that with todays price difference it is more affordable than ever to go with epoxy and add an additional margin to a repair or build. please go back and re-read what I wrote. epxoy doubles the cost of a small boat. epoxy has been so overpromoted that people use it to sheath boats that would be fine just painted. -- ------------------------------------------------------------------------------ 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 |
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