Polyester or Epoxy?
"BruceM" wrote in message ...
As one who has need for some poly glassing I have often thought there should be another news group for "ordinary" people. My whole boat is poly so why do some alterations in epoxy? BruceM No reason at all! But I still say for new construction, epoxy is just easier to use, guess I am just lazy and want the boat to come out right the first time without the unaviodable waste of material, sanding off early cured material, scraping off material that did not "like" the ambient temp, humidity, or mixing ratio you have chosen to address the same. I did build several boats in poly in the beginning, when I finally broke down and used epoxy, it was a life altering experience, kinda like going from a tricycle to a Porche... "Terry Spragg" wrote in message ... Michael O'Dell wrote: In article , "Allan" wrote: Hi. I'll probably get some thoughts on this. I built a 20' Osprey Triple kayak using epoxy resin. Nice boat. Now I'm building an 18' Trident Power Cat ( johnsboatstuff.com ). He's recommending epoxy for structural work and polyester (either orthothalic or the other one, I can't remember right now, would have to look at my plans) for glassing up. Anyway it's the "better" polyester. I like the price of the polyester, but.................. Anybody have any thoughts on why I should go all epoxy or use the epoxy/polyester combo??? Thanks for any comments, thoughts. Amateur 2nd boat builder in the Great White Frozen North, Allan build in epoxy - period. polyester has no secondary bond strength and not a lot of primary bond strength. epoxy is not that much more expensive and could well save your boat. epoxy actually sticks to the glass where polyester does not; it merely hardens *around* the glass fibers. that's why a polyester laminate peels apart along the surface of the reinforcement when it goes into failure. -mo I guess that's why all my 30 year old poly boats just collapsed into piles of hairy dust in my backyard, eh? Zero strength, eh? How do you calculate the cost benefit from this supposed longer life for epoxy, given that the life span is still generally indeterminate for both types under reasonable stresses? I have heard of very few poly boats disintegrating in any remarkably shorter time than epoxy, even in contests involving rocks and stuff. Such extremeist statements suggest you must be a berserker stock market manipulator with interests and positions in the epoxy chemicals market bordering so extremely on the insane as to suggest you sell epoxy mainly to be able to continue to dispose of toxic chemicals added in small amounts to the resins, just like some shampoo vendors I suspected of doing just that until your arguement was so strongly stated and foolishly revealed ;-) Now, as far as skin irritation and developed allergies and consequent lifetime sensitivities and costs associated with respirators, deformed babies, etc, I would favour poly quite strongly for a hobby builder, especially a relatively inexperienced one, especially for a first build. Commercially, the evidence is overwhelming. I cannot imagine anyone smart enough to be able to afford the costs of epoxy being insensitive to those cost benefit analyses so evidently performed and adhered to by professional builders. You just try to get an informed professional to build in epoxy and then count the costs. -- Terry K - My email address is MY PROPERTY, and is protected by copyright legislation. Permission to reproduce it is specifically denied for mass mailing and unrequested solicitations. Spamspoof salad by spamchock TM - SofDevCo ® |
Polyester or Epoxy?
Bruce,
The "ordinary" people are the ones that can best justify epoxy because the quantity they typically us is small compared to the production user. To answer your question about why to use epoxy instead of poly is, that it makes a better repair. Regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. |
Polyester or Epoxy?
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Polyester or Epoxy?
I have had hundreds of my customers using polyester resins on my Sevtec surface
skimmer hulls without difficulty, and a few using epoxy, against my advice, with difficulty. In one case, amine blush of the epoxy caused the failure of tabbing that held some hull panels together and the result of using a brake, Yes, a brake on a surface skimmer, at about 35mph, caused the hull bottom to peel off, fortunately with no significant injuries, even though one person of three aboard went through the hole in the bottom and came up treading water behind the craft. Epoxy is very critical in mix ratio, and that is why scales or proportional pumps are used, while polyester catalysis is easily done with a small graduate cylinder, and variations of mix ratio of 20%, which would certainly spell disaster with epoxy, are of no concern with polyester. Some structures do benefit from epoxy, but if the structure strength or stiffness is governed by the glass, not the resin, epoxy may be a waste, except in long term exposure to warm climate salt water. Subject: Polyester or Epoxy? From: (Backyard Renegade) Date: Thu, Jan 15, 2004 3:00 PM Message-id: (Ron Thornton) wrote in message ... Bruce, The "ordinary" people are the ones that can best justify epoxy because the quantity they typically us is small compared to the production user. To answer your question about why to use epoxy instead of poly is, that it makes a better repair. Regards, Ron I don't recieve e-mail at this address because of spam. E-mail me at crtsrATmsnDOTcom. But that is really not even much of a factor anymore. To build a 12 foot skiff with flotation and proper materials, it is going to cost you $250.00 on materials and hardware alone (assuming exterior plywood hull), and just for ha ha's, say $25 for a set of plans. If you use poly instead of epoxy, you might save $25 to $30 bucks max on the whole build and more times than not, I have seen first time builders end up using 2-3 times more poly than the plan would call for. The learning curve for mixing poly is treacherous, (bring a good scale and a calculator too) especially to the home builder that may be building outdoors, or in a non conditioned barn, tent, etc. Let me take a minute for anyone who is not clear about mixing the two products. With polyester, you must first calculate your catalyst ratio. So many ounces of resin, to so many drops of catalyst. This mixture is not only very delicate, but it changes depending on ambient temp, humidity, how fast you want things to cure and the required differences in the catalyst mixtures is very minute, and are based on the starting formula plus the users best guess or experience of how to alter that formula to suit the conditions at the time. Any very slight miscalculation in the mix or even how many clouds will pass over during the application can cause total havoc resulting in a slimy hot slop all over your boat that is extremely difficult to remove (think half hardened plastic mixed with cold roofing tar), that is to hard to scrape, and to soft to sand, or a fast kick which catches you with only half of your glass saturated, or just gobs up thicker and thicker as you try to catch up and save something. In both cases the only solution is a lot of elbow grease and lot's of wasted time and sand paper, scrapers, and then a re-application. With Epoxy, the cure rate is also dependant on the temp and humidity of the work area, but not nearly as fast or as radical. Mixing is done with calibrated pumps, something like one pump of resin to one pump of hardener. If you want a faster cure, substitute a "fast" hardener, if slower is your style or a bigger area to do in warmer weather, use a slower hardener, no calculators, no precision scales, no guesswork at all. If your pumps are working properly, and you don't get lazy mixing, even mistakes will harden nicely to be ground or sanded off. One extreme case (admittedly the most extreme I am aware of) was a couple of years ago when I came in very late by e-mail on a build of "Diablo", a 15 foot Bolger type skiff. The plan calls for 2 1/2 gallons of resin. This guy had a terrible summer of heat and cold, never really got the mixtures down in his one build. He spent literally dozens of hours scraping and sanding and just throwing out resin that either kicked to fast, or not at all. He ended up using 11 gallons of poly on the build at a total cost of over $200 for resin alone. Not to mention lost thickeners, thinners, brushes, sand paper, scrapers, time, time, time, time, time... I will stop now, but he has since built another boat, but this time he used epoxy, no problems. Now I don't expect any first timer to build Diablo with 2 1/2 gallons of resin, but certainly 3-3 1/2 should be the max. One final comment. I do not know what the original poster should do, I have no experience there, I don't do restores ;-) I also do realize that poly has it's place in composite shops where big lay-up is done or for molded parts, but somehow this thread seemed to get hijacked to my area so I thought I would chime in here. So this has been my advice, take if for what you paid. Scotty from SmallBoats.com BRBR Barry Palmer, for A HREF="http://members.aol.com/sevtec/sev/skmr.html"Sevtec/A |
Polyester or Epoxy?
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 |
Polyester or Epoxy?
William,
If what you say in true, why not soak all the laminating schedule in uncatalysed resin lay it up and then spray or brush on a light coat of catalyst? The manufacture's published mix ratio's do not seem to be all that open. If proximity to catalyst is enough the get the polyester material to cure, then how is it that I have found uncured resin imbeded in structures a decade or more after the build date? Back when we used polyester exclusively, never-cure mixes did seem to a real possibility as well as the heat up while mixing version. In our shops we have done eperiments with the procedures you have outlined and did not have the success that you seen to have had. Infact we were able to show some remarkable failures on test assemblies. Matt Colie www.southpointechandler.com 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 |
Polyester or Epoxy?
"William R. Watt" wrote in message
... Epoxy is risky to work with because the proportions have to be exact and the mix has to be thorough. 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....... Meindert |
Polyester or Epoxy?
Matt Colie ) writes:
In our shops we have done eperiments with the procedures you have outlined and did not have the success that you seen to have had. Infact we were able to show some remarkable failures on test assemblies. Jaques Mertens wrote much the same in an earlier thread on this never-ending topic. From the sound of it you are both working on big boats with large cross sectional areas, eg solid keels, which may explain the differences. I've only built small plywood boats I can pick up and put on top of the car, under 50 lb. TF Jones describes using uncatalysed thickened poylester resin for filleting on a Dobler 16 made out of polyester/fibreglass panels substituted for the usual plywood panels. The design being discussed in this thread is also small. -- ------------------------------------------------------------------------------ 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 |
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 |
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