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  1. #1
    Corsair2013's Avatar
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    Question Is West System a Polyester Epoxy?

    Guys, I am not an expert with Fiberglass and epoxy resins so I need some help.

    Is there a difference between Polyester Epoxy and West System Epoxy? I thought I read that Polyester is the "stinky" stuff and West System-that I use, has very little odor so it is different.

    What is the Epoxy - 5 minute and 30 minute sold at the LHS or stores?

    My main question is - if my fuselage was constructed with Polyester Epoxy will the "regular" LHS 5 and 30 minute Epoxy and West System Epoxy and fiberglass work okay or do I need to use a special epoxy?

    Thanks for your help

    Keith
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    Keith

  2. #2
    invertmast's Avatar
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    Polyester is just that. Polyester.
    Epoxy is a different chemical makeup than polyester resin.

    LHS and west epoxy will stick to a polyester glass fuse, just make sure the surface is cleaned and roughed up.
    Thomas W.
    Euro-sport Evo, Scratch built 1/7 F-14D Tomcat, 26.5% Gee Bee R2

  3. #3
    Corsair2013's Avatar
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    Okay I think I have it.

    Resins are used with fiberglass or other materials to build.

    Epoxy is used as a glue.

    I got them confused there for a moment as I thought I read somewhere that you could use Epoxy with fiberglass instead of resin.

    Thanks!

    Keith
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  4. #4

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    No you do not quite have it. Epoxy is one type of resin. Polyester is another type of resin. Both are two part catalyzed resins. Both can be and are used with fiberglass. Not used together but one or the other. Resin is a generic term/word that refers to a thick syrupy liquid. Anyone else care to jump in and add anything for clarification?
    obsessed Stuka D3 nut

  5. #5
    invertmast's Avatar
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    Quote Originally Posted by Corsair2013 View Post
    Okay I think I have it.

    Resins are used with fiberglass or other materials to build.

    Epoxy is used as a glue.

    I got them confused there for a moment as I thought I read somewhere that you could use Epoxy with fiberglass instead of resin.

    Thanks!

    Keith

    Ok,
    lets dig deeper since google isnt getting used, and there is a WHOLE LOT of information to be read and learned about composites on the interweb

    you have:

    Polyester resin: this is a polyester resin that is typically catalized using MEK as a hardener. The "Bondo" brand fiberglass kits you see at walmart and auto parts store, that is polyester resin.

    Then you have:

    epoxy resin: This also is a two part chemical. Depending on its intended use and manufacturer, its consistency could be anywhere from water thin, to "thixotropic" which means it doesnt run or sag when placed on a vertical surface.
    Its mixing ratio's also vary greatly.

    The epoxy you see in a hobby shop is what i would call a syrup consistency and is used to bond parts together when a glue joint needs to be stronger than what a CA adhesive can provide, and are typically mixed in equal parts A and B.

    The problem with the thicker consistency epoxies at the hobby store is they have short work times and are very difficult if not impossible to use in "wetting out" fiberglass cloth.

    That is where "laminating epoxies" come into place. Brand names include: West systems, adtech, resin research, and many more. These epoxies are typically Not mixed in equal parts. They can also have different types of hardeners to change the working time and the physical cured properties of the cured resin. These resins are also much thinner in consistency. This thinness of consistency allows the resin to work into and "wet out" the fiberglass cloth more quickly and with more ease. These resins are typically not used as structural "bonding" resins due to them being thin and running away from the glue joint. To use them as a structural bonding resin, filler materials must be used to change the properties of the resin.

    When it comes to fiberglassing something like a balsa structure, making a fiberglass mold, or laying up a fiberglass fuselage/cowl/etc, a "laminating resin" is used. When you want to bond parts to a fiberglass molded parts, you want to use a structural resin, such as Hysol or a quality hobby grade epoxy resin.
    Thomas W.
    Euro-sport Evo, Scratch built 1/7 F-14D Tomcat, 26.5% Gee Bee R2

  6. #6
    Corsair2013's Avatar
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    Thanks that info really helps
    P-40 Brotherhood # 82
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  7. #7
    speedracerntrixie's Avatar
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    Corsair, if we knew exactly what task you are performing we would be able to suggest the correct product. In my case I keep a gallon of laminating epoxy around. I use it in its original form for glassing wood parts, laying up fiberglass parts and such. When I need some epoxy (glue) I mix up some laminating resin and add some milled fiber and cabosil until I get the consistency I want. Polyester resins never make it into my shop.

  8. #8
    Corsair2013's Avatar
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    I have a Skyshark P-40 Fiberglass Fuselage. I don't know what type of resin was used to construct and one of the guys said he called Skyshark and they said the fuselage was made with Polyester Resin.

    I was trying to figure out if the 5 minute and 30 minute LHS epoxy was okay to use on the fiberglass since I am almost finished. I did sand the fiberglass prior to application of any epoxy. I also used hot glue in some areas but didn't sand.

    I was going to lay up a little more fiberglass inside to strengthen some areas using the WEST SYSTEM so again will this be okay to us as long as I sand/rough up the area first?

    Thanks again

    Keith
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  9. #9
    invertmast's Avatar
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    Hot Glue!!!!!!

    That's for crafts and foamies, not a heavy flying RC model!

    The hobby store epoxy will be fine on the fuse as long as the surface was roughened and them cleaned well with acetone.
    Thomas W.
    Euro-sport Evo, Scratch built 1/7 F-14D Tomcat, 26.5% Gee Bee R2

  10. #10
    speedracerntrixie's Avatar
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    If you are laying up additional fiberglass cloth I would suggest using some laminating resin such as West Systems or even Z-Poxy would work well. 30 min epoxy works well for installing formers and such but not for wetting out cloth.

  11. #11
    Corsair2013's Avatar
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    I use the West System and it has worked really good for me making my hatch and adding a little strength to some areas.

    Thanks

    Keith


    Quote Originally Posted by speedracerntrixie View Post
    If you are laying up additional fiberglass cloth I would suggest using some laminating resin such as West Systems or even Z-Poxy would work well. 30 min epoxy works well for installing formers and such but not for wetting out cloth.
    P-40 Brotherhood # 82
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  12. #12
    ezbrit's Avatar
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    Since its a polyester resin fuselage, you should really use a polyester resin to apply extra layers as this will provide the best results.

  13. #13

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    Get rid of Polyester Resin. Polyester should not be allowed in a domestic environment. The hardener, MEKP, is extremely dangerous. MEKP is Methyl Ethyl Ketone Peroxide. One minute drop in the eye and the sight in that eye WILL detoriate. I trust you wear safety glasses in all resin work.

    The best epoxy resin I have used is MGS, epoxy resin. It has two hardeners, a fast, about 45 minutes and a slow, about five hours. The hardeners can be mixed to provide a cure time of choice. Some experimenting is required. MGS is available from Aircraft Spruce & Specialty.

    Ed S
    Last edited by Ed Smith; 03-12-2014 at 07:39 AM.

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    ezbrit's Avatar
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    Hi Ed, I'm in complete agreement with you with the health and environmental issues of polyester and vinylester resins. The problem of laying up an expoxy laminate over a polyester one is two fold. Firstly,its very hard to achieve a good bond as expoxy doesn't adhere well to polyester and secondly, polyester is a very unstable material and is prone to shrinkage and warpage. Epoxy on the other hand is quite stable, especially the higher quality ones. When you mix the two systems you will end up with the polyester shrinking around the epoxy patch and that will show on the fuselage surface at the very least. It will probably lead to delamination over time too.Regards,Ian

  15. #15
    sensei's Avatar
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    I wouldn't worry much about the epoxy not bonding well to the cured poly surface because it will bond just fine. Really!

    Bob
    Last edited by sensei; 03-13-2014 at 04:50 AM.
    Fly It Like You Stole It!!!

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    Epoxy will stick to polyester better than polyester sticks to polyester

  17. #17
    ezbrit's Avatar
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    Within the composite industry, putting a epoxy layup over a polyester layup is a definite no no for the reasons I have stated above. Even when we have to bond two polyester parts together, we use polyester resin with cotton flock and fumed silica rather than high performance adhesives like Hysol 9360.

  18. #18
    sensei's Avatar
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    Quote Originally Posted by ezbrit View Post
    Within the composite industry, putting a epoxy layup over a polyester layup is a definite no no for the reasons I have stated above. Even when we have to bond two polyester parts together, we use polyester resin with cotton flock and fumed silica rather than high performance adhesives like Hysol 9360.
    Sounds like your building boats utilizing old school methods, those old methods work alright but there are much stronger ways of getting it done these days with epoxy or acrylic structural adhesives either one ...

    Bob
    Fly It Like You Stole It!!!

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    So that it can be seen I have some knowledge of composite use I attach some pictures. The fuselages were molded with MGS epoxy. The foam wings were skinned with balsa and covered with 3/4 oz glass squeegeed down with MGS epoxy. The propellers were molded with carbon fibre and MGS epoxy. GET RID OF POLYESTER!

    Ed SClick image for larger version. 

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  20. #20
    ezbrit's Avatar
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    Hi Bob and Ed,

    Bob, your are correct in your assumption that I'm using 'old school boat building methods' and that is because the subject fuselage we are discussing has been produced using 'old school boat building methods' and until a company develops a temperature sensitive, highly unstable, flexible epoxy resin to match the characteristics of polyester resins, there will always be a performance mismatch between the two resin systems. I whole heartedly agree that almost any epoxy adhesives will out perform the polyester/cotton flock/fumed silica method I suggested, but the reason that I made that suggestion is because I know that the polyester adhesive will exhibit exactly the same characteristics of the polyester laminate. I'm sure you are well aware of the low temperature sensitivity(T of G) of polyester, normally around 110 degrees. As the temperature increases past this point, the polyester softens and weakens considerably and becomes unstable. Now lets say that the formers have been bonded into the polyester fuselage using a normal off the shelf 30 minute epoxy and a reinforcing laminate using finishing resin, both with a 160 degree T of G which is pretty normal. Because this is a warbird, we are of course, going to paint it in dark, flat camouflage colors and when finished we will take it to a warbird fly in where it will sit in the sun with surface temperatures reaching 140 degrees. At that temperature, the polyester is going to become highly unstable and flexible, yet the epoxy adhesive will remain unaffected which will result in surface distortions around where we have used epoxy to bond and reinforce areas. This is the reason I gave the advice I did, because I didn't want to see Keith spend countless hours building a show stopping warbird, only to discover that it has a 'starved horse' appearance after it's first outing.


    Ed, As I stated before, I'm no fan of polyester and hate using it and there are far better alternatives with epoxies. When the model manufacturers quit using polyester to build models, then we can quit using polyester to repair them and I'm fine with that. I never questioned your ability and obviously you are skilled evidenced by the work in your photos. My background is that I'm a composite fabricator/fitter with 16 years of experience in racing, aircraft, marine, musical, military, medical and space exploration fields as well as this composite field. I'm just trying to pass on my hard learned experiences and I'm happy to help out anyone who wants it.

    Hope you both have a great weekend,
    Ian

  21. #21
    sensei's Avatar
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    Quote Originally Posted by ezbrit View Post
    Hi Bob and Ed,

    Bob, your are correct in your assumption that I'm using 'old school boat building methods' and that is because the subject fuselage we are discussing has been produced using 'old school boat building methods' and until a company develops a temperature sensitive, highly unstable, flexible epoxy resin to match the characteristics of polyester resins, there will always be a performance mismatch between the two resin systems. I whole heartedly agree that almost any epoxy adhesives will out perform the polyester/cotton flock/fumed silica method I suggested, but the reason that I made that suggestion is because I know that the polyester adhesive will exhibit exactly the same characteristics of the polyester laminate. I'm sure you are well aware of the low temperature sensitivity(T of G) of polyester, normally around 110 degrees. As the temperature increases past this point, the polyester softens and weakens considerably and becomes unstable. Now lets say that the formers have been bonded into the polyester fuselage using a normal off the shelf 30 minute epoxy and a reinforcing laminate using finishing resin, both with a 160 degree T of G which is pretty normal. Because this is a warbird, we are of course, going to paint it in dark, flat camouflage colors and when finished we will take it to a warbird fly in where it will sit in the sun with surface temperatures reaching 140 degrees. At that temperature, the polyester is going to become highly unstable and flexible, yet the epoxy adhesive will remain unaffected which will result in surface distortions around where we have used epoxy to bond and reinforce areas. This is the reason I gave the advice I did, because I didn't want to see Keith spend countless hours building a show stopping warbird, only to discover that it has a 'starved horse' appearance after it's first outing.


    Ed, As I stated before, I'm no fan of polyester and hate using it and there are far better alternatives with epoxies. When the model manufacturers quit using polyester to build models, then we can quit using polyester to repair them and I'm fine with that. I never questioned your ability and obviously you are skilled evidenced by the work in your photos. My background is that I'm a composite fabricator/fitter with 16 years of experience in racing, aircraft, marine, musical, military, medical and space exploration fields as well as this composite field. I'm just trying to pass on my hard learned experiences and I'm happy to help out anyone who wants it.

    Hope you both have a great weekend,
    Ian
    Ian,

    You mean the (CTE) coefficient of thermal expansion, yes I am well aware of it's effects, I use the CTE almost on a daily basis in my calculations of machining metal layup blocks; carbon steel or 6061 T6 aluminum for use of manufacturing high temperature composite aerospace components.

    Your statement of the polyester resin weakening and turning to rubber at roughly 12 degrees higher then our body temperature (98.6 F./110 F. is in fact only fiction, I have seen much higher heat yields from polyester resin systems, ISO or Ortho either one. Like you I have also been in the game for a minute and know that the heat distortion of polyester is considerably higher then you stated, so at 140 F. their fuselage is not going to turn to rubber. By the way a dark surfaces like carbon black sitting in the sun can and does reach much higher temperatures than 140 F. More like of around 240-280 F. Hot enough to fry an egg in the Mojave desert, but that is another story. If you are seeing distortion around formers in any fuselage it's generally caused from wood being used as the former's inside of a relatively thin skin layup with no core as seen in most all old school stuff, using dissimilar materials edge bonded inside a thin skinned no core fuselage made from an epoxy layup will show rib transfer after a couple of outing in the sun, especially if painted dark. There are many reasons the unknowing have these kind of issues, but having a fuselage that begins to turn to rubber around 110 F. from the use of polyester is not one of them, don't get me wrong, I too stopped using poly nearly 30 years ago, but am well aware of what you can, or cannot do with the stuff.

    Have a nice day!!!

    Bob
    Last edited by sensei; 03-17-2014 at 05:03 AM.
    Fly It Like You Stole It!!!

  22. #22
    ezbrit's Avatar
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    Hi Bob,
    Tg and CTE are not related. CTE measures the expansion of a material as the temperature increases. Tof G or Tg (Glass Transition) is the measurement of strength as the temperature increases. Two completely different things and in the composite industry we have to take both into account. The Tg of polyester is around 110 degrees and this is the point where the resin matrix begins to soften and becomes unstable, I never implied that turns to rubber. Of course you can increase the Tg of a composite laminate by post curing, but in general, the Tg of polyester will never exceed much above 140 even with post curing. A high temperature polyester is available but only to industry as far as I know and even that stuff is only good to 160 with post curing.
    We have done plenty of testing of surface temperatures on carbon fiber and we have never seen temperatures even close to 240 degrees and our tests were conducted in the Middle East for a military application. The maximum temperature that was recorded was 197 degrees and I believe the ambient was around 120 degrees and we were fairly close to the Equator.
    I feel that this has started to become case of 'one-upmanship' and I don't believe Keith would appreciate it on his Thread, so let's just leave it as you can go do your thing and I'll do mine.

    Regards,
    Ian

  23. #23
    sensei's Avatar
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    Ian,

    For the record, I just wasn't sure you knew what your were talking about because as far back as I recall I have used the term or have heard it referred to as simply the TG, not the (T of G). Anyway to be honest I think your more of a book worm from your ramblings without much practical behind you, and my reasoning for your rib transfer is still holds true. By the way, I stated carbon black in the sun reaching those temperatures, you know the stuff we use as an UV barrier over composites prior to topcoat, not carbon fiber cloth. I also think Kieth would appreciate getting an honest educated opinion from those with some credibility, a track record, and something they can show to the unknowing if need be.

    Bob
    Fly It Like You Stole It!!!

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    ezbrit's Avatar
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    Wow, Really Bob? This is what I was trying to avoid by saying that you go do what you do and I'll go do what I do. Obviously we weren't going to see eye to eye on this, but for you to question my credentials and to make assertions about my abilities and experience when your ego feels threatened is a bit much. It's quite clear that you didn't have a clue what Tg, T of g or T sub g was, until you Googled it after my last post, otherwise you wouldn't had made the comment about the fuselage turning to rubber at 110 degrees and when you thought it was CTE just confirmed that fact to me. Carbon black is still carbon (we use paint with a UV blocker in it), if you are experiencing temperatures of 240 to 280 degrees, then I'm surprised that the World Energy Committee isn't on your doorstep asking you about you new self perpetuating heat source because the radiant heat from the sun isn't going to produce those kind of temperatures. If that was the case, we wouldn't need a kitchen stove as you would be able to cook food and boil water outside. As stated, we have done extensive research on the sun's radiant heating on composite parts and even on the Equator you would be pushed to exceed 200 degrees and at our latitude is considerably less. Also at those temperatures you stated, you would be on the Tg point of most medium temperature prepregs and way beyond laminating resins, so you had better inform Burt at Scaled Composites that all his composite aircraft are structurally compromised.
    As you stated, you are employed as a machinist. My employment is as a highly experienced composite laminator / fitter and our customers include major manufacturers in Aerospace, Automotive, Racing, Marine and I have been an advisor on the Gravity movie in regards to composite structures. I have been involved in projects of some well known R/C scale pilots and I certainly don't think that x number of post reflects credibility. I noticed by your previous posts that you like to butt heads with other members on this forum site, probably for the same reasons that you are butting heads with me. I think what you wrote about your impressions of me is more of a reflection of your abilities. Go down to your local boat repair yard and ask them to do an epoxy repair on a polyester part. I'll guarantee you'll get some strange looks. Oh, and there is a simple way to bond plywood formers into an uncored, thin laminate skinned fuselage without it deforming the outer surface and I'm surprised you don't know this with all your years of 'expertise'.

    Well, I wish I could say it has been fun.......
    Ian


    BTW. the boys in the shop send their thanks for the entertainment you have provided them with today with your comments and ideas on this thread.

  25. #25
    sensei's Avatar
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    I never stated that I am a machinist.

    I stated that I use the CTE on almost a daily basis for calculating dimensional criteria for the machining of metal LUBs when utilizing high temp pre-pregs in the manufacturing of aerospace components, my shop techs perform the work through the processes I write.


    So you're a combo layup/trim tech, that's fine, I still employ many guys and girls just like you, but none of them have been called to advise Sandra and George with their movie voyage in space...


    For the record there wasn’t a Google search, or internet back when I/we were building boats with polyester resin and a chop gun nearly 40 years ago, most of what many of us learned back then was through the school of hard knocks, but you are right, I don't why I was thinking 240-280 F, 180 F. is about it with a flat carbon black surface in direct sun on a 108 degree day, I had to go back and look at what we did on a wing twist problem we had, many years ago. My family owned a hanger at Mojave airport, one of the guys out there (Ernie Tailor) built A Rutan Vary Easy, the problem he had was during his build he created a 3 degree twist in one wing. Now he could trim the roll out while flying but it was speed sensitive so the trim was a constant PITA if you know what I mean. Anyway with a couple of weeks prior planning and on a summer early morning in front of our hanger we set the airplane up with a fitted and clamped wingtip saddle that extended aft the aircraft about 10' it was padded and placed just inside the winglet, we also placed a 4" x 4" from the ground to the bottom of the saddle as a fulcrum point. Now with all this in place we hung around 80 pounds of lead at the end of the 10' beam placing roughly 800 lbs. of anti twist load to the wing until we actually had 1 degree of twist in the opposite direction, we painted the top and bottom of the wing with flat black carbon paint and placed mirrors laying on the ground under the wing as well, we then just waited as the day went on got hotter, while checking the surface temp and twist throughout the day until evening as things cooled down. (This is what I remembered wrong but there it is in our own notes...) In the end the wing twist yielded to a new set and with a little spring back the wings were the same. The wing did have to be removed and the outer 3 plies of glass ground off, re laid up, and refinished because we literally blistered the first 2 plies and the paint from the surface, but we saved the wing and the airplane is still flying today. We went that route way back then because we didn't have a process oven back in those days and the airplane made a great holding fixture for twisting against...


    Bob
    Last edited by sensei; 03-19-2014 at 09:52 AM.
    Fly It Like You Stole It!!!


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