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Thinning Epoxy Resin

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Old 10-17-2005, 01:29 AM
  #51  
TGoodwin
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Default RE: Thinning Epoxy Resin

Wow. All this over thinning epoxy. This is why I do not post much in this forum. Why not just state your opinions and leave it at that? There are many ways to do many things. My way is not always the correct way but it works for me. To thin or not to thin? That is the question.

T
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Old 10-17-2005, 08:16 AM
  #52  
chelapa
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Default RE: Thinning Epoxy Resin

yeah i didnt think by posting i would cause all this. Why cant we just all get along! come on its the damn internet. Gosh. haha. well i made GREAT success WITHOUT THINING! =). its all in the hands. Really it is. its in the technic of when, how you apply each layer of fabric with resin. THe final output of my stuff came out GReAT! strong, no pin holes. atleast maybe 1 or 2 small ones. nothing major, AND the resin level kept to a min. thanx guys! i am still looking for great epoxy thou.
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Old 10-17-2005, 11:25 AM
  #53  
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Default RE: Thinning Epoxy Resin

The primary purpose of glassing a model is not structural strength but rather to create a smooth substrate by which to paint. No more, no less.


I cannot understand either why such a simple subject turned hostile. It takes only one person to do this with statements like the above. There are many reasons and methods for glassing aircraft. The above statement is simply wrong. It shows a lack of experience about the subject.

Ed S
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Old 10-17-2005, 07:30 PM
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Default RE: Thinning Epoxy Resin

ORIGINAL: Ed Smith

The primary purpose of glassing a model is not structural strength but rather to create a smooth substrate by which to paint. No more, no less.


I cannot understand either why such a simple subject turned hostile. It takes only one person to do this with statements like the above. There are many reasons and methods for glassing aircraft. The above statement is simply wrong. It shows a lack of experience about the subject.

Ed S

West System 105 Resin throughly mixed with 209 hardener using the supplied pumps can have Denatured Alcohol added for purposes of reducing the viscosity of the mixture.

This is a "tried and proven" method of thinning epoxy. It has been for more than twenty years.

It's not hard, it's easy........
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Old 10-17-2005, 10:28 PM
  #55  
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Default RE: Thinning Epoxy Resin

You can thin epoxy with alcohol but you will have a stronger resin if it is not thinned in this manner. Solvents used to cut epoxy paint flash off very fast and would not give the working time for laminating.
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Old 10-18-2005, 08:20 AM
  #56  
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Default RE: Thinning Epoxy Resin

I just cleaned up a few comments.

Its ok to dissagree, lets just keep things civil.
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Old 10-18-2005, 10:09 AM
  #57  
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Default RE: Thinning Epoxy Resin


ORIGINAL: RAPPTOR

[X(]STUFF IN THE HOUSE ???..LIKE GUNS!!!!! SORRY ,ITS ,YOUR JOB, NOT TO HURT YOURSELF, NOT THE REST OF THE WORLD...HOW ABOUT KITCHEN KNIVES?? OH MY.. NOT---- RD

finaly.... thank you
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Old 10-19-2005, 09:01 PM
  #58  
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Default RE: Thinning Epoxy Resin

Wow, I don't read for 3 days and look what I am left with. I don't want to throw a lot more fuel on the fire, but let me just say a few things.

1. I am not the most experienced model builder here by any stretch.
2. I am likely the most experienced person here with respect to epoxy chemistry and structural aerospace composites (that is my day job).

I will certainly yield that I did not make my point perfectly clear earlier. In the case of using glass to make a nice smooth aero surface, the addition of solvent to an epoxy mixture is acceptable. This is true because the porosity created doesn't affect the unneeded structural strength. However, if the solvent cannot make its way out of the epoxy before the gel point of the resin, it will end up in a rubbery epoxy.

My point was that most modellers don't take advantage of the fact that their glass skins have considerable structural value. If you don't take advantage, it is wasted weight! Except for the fact that it provides a smooth surface.

Branded, I would take some issue with your claim. The epoxy system that you use may work very well for you, but you have also worked with it for some time and have gotten used to its performance and processing characteristics. The proper solution to this problem is to fundamentally change the chemistry of the epoxy. By changing the reactivity of the curing agent and the preparatory adduction of that curing agent on to the epoxy, you can really tweak the viscosity and gel profiles of the material. In this manner, you can make an epoxy resin that processes very similarly to a polyester or vinylester, but has the higher strength and greater sag resistance of epoxies (if you don't believe me, reference Gilbert, Hayes and Seferis in the International SAMPE Symposium from ~2000).

The bottom line here is that for non-structural applications, the right thing to do is trial and error. Those of you who are using high-performance epoxies, good to you. However, you aren't taking advantage of their enhanced strength properties, believe me. If you don't maybe we can start another thread.

Matt
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Old 10-19-2005, 09:38 PM
  #59  
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Default RE: Thinning Epoxy Resin

Matt (gluedoc),
I believe you that most of us aren't using our materials to the best of their abilities, so I'll ask you to go ahead and start that other thread. Please be as technical as you like... several of us are comfortable with (and interested in) the gory details. We don't all have FEA at our disposal for design optimization, but general principles are easy enough to apply.

thanks,
-David
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Old 10-19-2005, 09:52 PM
  #60  
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Default RE: Thinning Epoxy Resin

Matt,

I would like to echo David's comments in that I think it would be great to hear from someone in the industry as to exactly what our epoxy and other glue systems are actually doing. What does increase strength? What are you looking for in finding the "lightest" epoxy product to do the job? I am VERY interested in any technical info that can make my kits better/lighter/stronger. That will take another thread and I will look forward to reading it.

Dan

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Old 11-27-2005, 11:34 PM
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Default RE: Thinning Epoxy Resin

Interesting comments,
maybe someone can answer this, I have been using the cheapest isopropyl alcohol I can find at the drug store to thin down Devcon epoxy for fuel proofing and NEVER in over 30 years have I had any problems with it not curing hard. By what has been said here, how can this be? And another question, why would you want to thin down a finishing epoxy in the first place? I have been using West Systems for years and have had excellent results. To glass my models, I lay down 3/4 glass cloth, spread West Systems epoxy on evenly with a foam brush, use a playing card from a deck of cards to scrape off as much epoxy as I can, then go over that with a roll of toilet paper to get what is left. After I leave the part sit overnight, I'll sand the part down to the weave of the cloth. Then I'll paint a light coat of primmer and sand that for a smooth finish. If necessary, I may have to spray two coats of primmer, but I'll sand each coat down as much as I can without going into the glass cloth or wood. Sounds complicated, but actually this is easy for me to do.
I'm no expert on mixing this and that, I just know what works for me. I build in a shop in my basement that has the furnace and water heater in it so it's warm all the time. Also, if I were to use some of the chemicals mentioned here, I blow up the whole neighborhood. The only time I did have a problem is when I mixed 50% of part A to 50% of part A. Opps......been there, did that.
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