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30 minute epoxy & alcohol?

Old 12-21-2016, 12:59 PM
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Mikie 1
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Default 30 minute epoxy & alcohol?

Hi Guys,

I am building a Lanier Shrike 40 and am told by the plans to glass the top and bottom wings to the fuse section, at the joint, to add strength and help keep the wings from falling off.
I thought I remembered how to mix 30 minute epoxy with alcohol, to thin the mix, to make application of the same easier... But, so I mixed the two halves of epoxy and then added some rubbing alcohol but they seemed to not want to mix. It became a swirling mix of goop - with the epoxy not mixing with the alcohol. It was a mess!

Any suggestions? I thought I remembered doing this in the past, but NOT today!!
Old 12-21-2016, 02:00 PM
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foodstick
 
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There is a wide view of what to mix and not mix on epoxy glue. However when I do this to brush on a firewall I typically mix the two glue parts well, and then add in the alcohol. I add VERY little alcohol, and it is not quick to mix in.. you have to really stir it good.. it does seem to fight mixing at first like oil and water. I have never done this in a big batch so I don't know what your work time will be. If the mix is too thin I am not even sure how strong the cloth would be afterwards?

Anyhow many know more about this than me, hopefully someone will give you a better answer.
Old 12-21-2016, 03:37 PM
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RBACONS
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Acetone will work better than alcohol. It flashes off faster and disturbs the curing process less than alcohol does and there is no risk of introducing water (which rubbing alcohol has in it) which causes it to cure gummy. Don't add much. Maybe 10% at most. At first it looks like it doesn't want to mix but after a few seconds, it will go perfectly liquid.
Old 12-21-2016, 03:38 PM
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J330
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I go to Ace Hardware and use finish resin, it's cheaper, thin, and works. Tower too http://www3.towerhobbies.com/cgi-bin...?&I=LXCX58&P=7

Last edited by J330; 12-21-2016 at 03:52 PM.
Old 12-21-2016, 04:01 PM
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RBACONS
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No doubt finishing resin is as good or better if you have it laying around. Just takes much longer to cure (24 hrs or so).
Old 12-21-2016, 04:42 PM
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Go to hardware store and buy a quart of denatured alcohol, rubbing alcohol has a high percent of water which probably effects the ability to mix.
Old 12-22-2016, 05:50 AM
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I use the plastic lid of a discarded peanut can to mix epoxy. I add a capful of rubbing alcohol and it looks like everyone describes above. But if you keep mixing, it will become a homogeneous mixture that can be brushed with an epoxy brush
Old 12-22-2016, 08:32 AM
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You can heat it up with a hair dryer to get it to flow better too. Be quick, as it cures quicker. Some of the dollar store rubbing alcohol is mixed with a lot of water for more profit, so it is not useable for our purposes.
Old 12-22-2016, 11:44 AM
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Originally Posted by culver
Go to hardware store and buy a quart of denatured alcohol, rubbing alcohol has a high percent of water which probably effects the ability to mix.
If you're going to spend $10 on that, may as well get the finishing resin found one isle over? These chemistry experiments with unmeasured cocktails, doesn't sound like stuff I want screwing up my plane after all that build time. Make sure if you want to play chemist games, log the amounts you're using(wasting) and practice on a scrap piece first to see if it ever cures properly (more waste).
Old 12-22-2016, 12:17 PM
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I have used MEK to reduce epoxy for same purpose that you described in your original post. It works OK. Like J330, I worry about these unknown cocktails, but for laminating glass to the center section of a wing - at least it's easily inspected and not hidden inside structure.
Old 12-22-2016, 03:47 PM
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Thinning epoxy slightly with MEK or acetone is not a problem for non-structural purposes like fuel-proofing a firewall. I don't think any of the posters suggested for structural applications. I don't know why you would need a Masters in Chemistry to do this without extensive testing/wasting of product. Add a few drops, mix it in, if its thin enough to brush on, have at it. If not, add a few more drops.
Old 12-23-2016, 03:20 AM
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Originally Posted by culver
Go to hardware store and buy a quart of denatured alcohol, rubbing alcohol has a high percent of water which probably effects the ability to mix.
Exactly
Old 12-23-2016, 04:32 AM
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Originally Posted by jcrider
Exactly
+1^
Old 12-23-2016, 02:52 PM
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Any time you thin epoxy with alchohol, mek, acetone or ??? you wind up with a weaker final product. Best bet is to just use slow (30 minute or slower) cure epoxy direct. Then heat the area that you have the epoxy on and it will quickly thin out and magically be absorbed into the weave of the cloth. Do not overheat, i.e. not so hot it bubbles. Now lay a layer of Saran Wrap (what your wife uses in the kitchen) and smooth it out with your fingers. Leave set for 12 hours or so then remove the Saran Wrap. You will find a surface so smooth and slick you will be amazed; no sanding required and the edges will be perfectly flared out so no detectable edge to the fiber glassed area.
Old 12-23-2016, 04:26 PM
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I've used regular alcohol many times for many different applications of epoxy however I use the 91% rather than the 70% sold right next to it.
Old 12-23-2016, 05:05 PM
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Originally Posted by culver
Go to hardware store and buy a quart of denatured alcohol, rubbing alcohol has a high percent of water which probably effects the ability to mix.
+1. Rubbing alcohol has too much water -- any is too much.
Old 12-24-2016, 04:23 AM
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91% rubbing alcohol will work due to its lower water content, however denatured alcohol is the best option.
Old 12-24-2016, 09:30 AM
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Thanks to all of you that replied to my question!!
I didn't realize a bottle of alcohol was mixed with water. So, I went back to the bottle I've been using and, sure enough it listed it as 50% alcohol!! Wow!
OK, so anyway, I mixed up a batch of 30 minute epoxy and mixed in acetone and it took a little bit of sturring, but it became easy to "paint" on the balsa. Then I applied the 2 oz. fiberglass (1 X 2 inch pieces). Then went back and "painted" on more epoxy mix and I believe things will dry beautifully and very strong.
Again, THANK YOU ALL!! Merry Christmas!! (Remember the reason for the season!!) Mike
Old 12-24-2016, 02:35 PM
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If you must thin epoxy what works best is 99% Isopropyl Alcohol and then should be limited to 10%. Using an epoxy glue in any shape or form for wetting out glass cloth is just the wrong tool for the job. For glass work you really want a laminating epoxy resin. Z Poxy is most likely the easiest to obtain and can be bought in small quantities. Polyester resin could also be used but is heavier, weaker, more toxic and iron on covering does not like to stick to it. The term " finishing resin " is pretty much a farce, it is usually laminating resin renamed for marketing reasons.
Old 12-24-2016, 03:59 PM
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It is amazing how little epoxy is needed to attach glass cloth to wood.

The rule I use is; If the surface of the cloth looks shiney like it is wet then you have too much epoxy on the surface. It the cloth still looks white or dry, then you need a little more to wet it out. If too wet you can use paper towels to soak up the excess or squeegee some of the excess off completely or onto a dry spot.

Any cloth that has a wet look to it does not make the cloth epoxy stronger, it only adds more unneeded weight.

Another readily available laminating epoxy is the Bob Smith brand. Many hobby shops will have their name on the label but the bottle state it's from Bob Smith. If you order from Amazon, System Three epoxy is available in a reasonably small quantity for somewhere in the $30 range.

Ken
Old 12-24-2016, 06:13 PM
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For me, I'd be using West Systems with the 105 base resin and 207 hardener. Here's the write up from their website on the hardener:
[TABLE="class: techSpecTable, width: 100%, align: center"]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Mix Ratio, Resin:Hardener [/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]3:1 by volume (3.5:1 by weight) [/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Pot life at 72 F (22 C) [/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]22 to 27 minutes [/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Cure to a solid state [/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]9 to 12 hours [/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Cure to maximum strength [/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]4 to 7 days [/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Minimum recommended temperature [/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]60 F (16 C) [/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Pumps required [/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]300, 306-23 or 309-3 [/TD]
[/TR]
[/TABLE]


  • Excellent long-term clarity due to improved chemistry and stabilization with UV filters
  • Superior blush resistance
  • Extended recoating time
  • Excellent fiberglass wet out characteristics
  • Ideal viscosity for buildup coats
  • Excellent paint and varnish compatibility
  • Excellent physical properties for bonding


207 Special Clear Hardener was especially developed for use with West System 105 resin in coating applications where an exceptionally clear moisture-resistant natural wood finish is desired.Improved formula chemistry allows for true clear cure with same UV stability without amber tint. An ultraviolet inhibiting additive improves the resistance of a West System 105/207 mixture to sunlight but the cured epoxy surface will still require the additional protection of a quality UV-filtering varnish.
207 is designed to self level for smooth finishes and to wet-out and bond fabrics. Although it provides good physical properties for general bonding applications, it is more difficult to thicken and less cost effective for this purpose than 205 or 206 hardeners. It's also used for laminating veneers where bleed through at joints may be exposed to sunlight.
Old 12-28-2016, 01:53 PM
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Steve Collins
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Yes, if you want a surefire excellent result, spend a little cash and use the West Systems epoxy as suggested above.

I have used just about every method described here in this thread. Started using West Systems and will never go back to any other. Superior results every time.
Old 12-30-2016, 04:44 AM
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scale only 4 me
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Originally Posted by Hydro Junkie
For me, I'd be using West Systems with the 105 base resin and 207 hardener. Here's the write up from their website on the hardener:
[TABLE="class: techSpecTable, width: 100%, align: center"]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Mix Ratio, Resin:Hardener[/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]3:1 by volume (3.5:1 by weight)[/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Pot life at 72 F (22 C)[/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]22 to 27 minutes[/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Cure to a solid state[/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]9 to 12 hours[/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Cure to maximum strength[/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]4 to 7 days[/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Minimum recommended temperature[/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]60 F (16 C)[/TD]
[/TR]
[TR]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]Pumps required[/TD]
[TD="class: techSpecCell, bgcolor: #D4DCE7"]300, 306-23 or 309-3[/TD]
[/TR]
[/TABLE]


  • Excellent long-term clarity due to improved chemistry and stabilization with UV filters
  • Superior blush resistance
  • Extended recoating time
  • Excellent fiberglass wet out characteristics
  • Ideal viscosity for buildup coats
  • Excellent paint and varnish compatibility
  • Excellent physical properties for bonding


207 Special Clear Hardener was especially developed for use with West System 105 resin in coating applications where an exceptionally clear moisture-resistant natural wood finish is desired.Improved formula chemistry allows for true clear cure with same UV stability without amber tint. An ultraviolet inhibiting additive improves the resistance of a West System 105/207 mixture to sunlight but the cured epoxy surface will still require the additional protection of a quality UV-filtering varnish.
207 is designed to self level for smooth finishes and to wet-out and bond fabrics. Although it provides good physical properties for general bonding applications, it is more difficult to thicken and less cost effective for this purpose than 205 or 206 hardeners. It's also used for laminating veneers where bleed through at joints may be exposed to sunlight.
Originally Posted by Steve Collins
Yes, if you want a surefire excellent result, spend a little cash and use the West Systems epoxy as suggested above.

I have used just about every method described here in this thread. Started using West Systems and will never go back to any other. Superior results every time.
Another vote for West System, I bought a gallon set up about 15 years ago,, finaily had to buy more hardener this year,, Great stuff
Old 12-30-2016, 02:31 PM
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Have not used West Systems but as per someone elses comment have used Z-Poxy Finishing Resin for all my glass work for years. Nothing fancy, might on ocassion this with a tiny bit of 91% Iso then use old playing cards to squeegee it out till just the fibers are wet but no standing resin. Have never had a failure or any de-lamination using this system.

Epoxy glue "can" be used for application of fiberglass but as someone has pointed out it's not the correct tool for the job, does not sand well, does not take paint well and certainly does not hold up to UV rays if left exposed (will yellow VERY quickly and become brittle almost as fast)
Old 01-01-2017, 08:58 PM
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Originally Posted by Catalinaflyer
Have not used West Systems but as per someone elses comment have used Z-Poxy Finishing Resin for all my glass work for years. Nothing fancy, might on ocassion this with a tiny bit of 91% Iso then use old playing cards to squeegee it out till just the fibers are wet but no standing resin. Have never had a failure or any de-lamination using this system.

Epoxy glue "can" be used for application of fiberglass but as someone has pointed out it's not the correct tool for the job, does not sand well, does not take paint well and certainly does not hold up to UV rays if left exposed (will yellow VERY quickly and become brittle almost as fast)
That may be true for many epoxies, but not all. This is from the West Systems C&P above:
207 Special Clear Hardener was especially developed for use with West System 105 resin in coating applications where an exceptionally clear moisture-resistant natural wood finish is desired.Improved formula chemistry allows for true clear cure with same UV stability without amber tint. An ultraviolet inhibiting additive improves the resistance of a West System 105/207 mixture to sunlight but the cured epoxy surface will still require the additional protection of a quality UV-filtering varnish.

I know, the last line says to use a a UV filtering varnish for better protection but, in the 30+ years I've been involved with racing scale hydroplanes, I've never heard anyone say they had issues with West Systems epoxy. In fact, the only one I can say I've had issues with was Z-Poxy. I found it to be very brittle when used to coat a boat hull as opposed to WS. I also found WS to be easy to sand with an electric DA as well as sanding bars



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