MGS vs Aeropoxy

[jpolenek]

Rich (argoldman);

 

It’s good to see a familiar name on this forum, to which I am relatively new. I followed your progress on the Dragonfly for several years through that discussion group. It was a shame to hear of the loss of that plane. But it’s nice to see you’re back at it with the new project.

 

I'm trying to do my homework and determine which epoxy I’ll be using on my future Cozy. It seems that most Cozy builders are using MGS for one reason or another. If I am not mistaken, you are also using this product.

 

I'm leaning toward Aeropoxy since it is available locally and I'm already somewhat familiar with it, having gotten part way through my Dragonfly project.

 

Based on your experience with Aeropoxy on your Dragonfly, and now MGS on the Cozy, could you comment on how the two products compare, and why you didn’t just stay with Aeropoxy?

 

Joe

[argoldman]

Rich (argoldman);

 

It’s good to see a familiar name on this forum, to which I am relatively new. I followed your progress on the Dragonfly for several years through that discussion group. It was a shame to hear of the loss of that plane. But it’s nice to see you’re back at it with the new project.

 

I'm trying to do my homework and determine which epoxy I’ll be using on my future Cozy. It seems that most Cozy builders are using MGS for one reason or another. If I am not mistaken, you are also using this product.

 

I'm leaning toward Aeropoxy since it is available locally and I'm already somewhat familiar with it, having gotten part way through my Dragonfly project.

 

Based on your experience with Aeropoxy on your Dragonfly, and now MGS on the Cozy, could you comment on how the two products compare, and why you didn’t just stay with Aeropoxy?

 

Joe

 

Greetings Joe,

 

It's good to be able to physically be able to work on a new project. The remains of the dragonfly are in the hanger next to the new thing sprouting wings.

 

Now to epoxy. In my dragonfly I used a variety of epoxies starting with safe-t-poxy, and finishing up with Aeropoxy. I found aeropoxy to be a good product with the exception of its viscosity, which made the wetting out of the cloth more difficult (although I didn't see it as such since I had not used other easier to use products.) Because of it's viscosity, it was easy to incorporate tiny air bubbles into the mix, which, by the way, would disappear as it was being used. The color was great, and the smell acceptable (somewhat sweet, from what I remember.)

 

I started using MGS 285 system because it "seemed like the thing to do" with the cozy crowd. The material is virtually orderless (unless you directly smell the "hardener")

 

The material has very low viscosity, mixes well and is a dream to use. It wets out fabric very easily. I use a 50/50 mix of hard to slow "hardener" but you can adjust the cure time by adjusting the ratios.

 

I really like the stuff.

 

I went to the Arocanard factory to make my parts in their molds and we used EZ-poxy-- smelly, viscous, dark in color, and not nearly as easy to use as MGS. I couldn't wait to get back to my hanger and get back to MSG.

 

When MSG became unavailable, I switched to Pro-set. This material was probably the best wetter-outer of the group but the setting time was longest, about 24 hours or slightly more.

 

MSG as mixed above was ready to sand at 12 hrs.

 

I finished my one gallon of Pro-set, was then able to get MSG and that's what I will finish my plane with.

 

Being located in Canada, you will not have the kind of problems with shipping, etc., that we have.

 

I like the stuff. I suggest you use a pump for dispensing.

[jpolenek]

Thank you Rich! Your explanation has me re-thinking my inclination toward Aeropoxy.

 

Joe

[TMann]

I have a pump that will work for that for $100. I can't use it for my West System epoxy

[jpolenek]

One issue I had a few times with Aeropoxy is that it would kick off way early if I stopped mixing and just let the stuff sit without using it immediately. In the worst case, it would turn dark red, exotherm to the point of smoking, and immediately start to solidify. To avoid this, as soon as the mixing was complete, I had to split up the epoxy into smaller cups to keep the temperature down, or immediately dump some of it on whatever I was working on. Is this a unique characteristic of Aeropoxy or do all epoxies do this if you let them sit? If they all do this, how can the components be pre-heated, as some builders do, without the risk of inducing this runaway reaction.

 

Joe

[Phil Kriley]

I have a pump that will work for that for $100. I can't use it for my West System epoxy

But using a pump will not allow you to use both slow and fast hardener - right? I like to use about 3/4 slow and 1/4 fast - gives a good compromise of cure time and working time for my workshop. As the weather gets warmer, I can use less fast as desired. How could you do this with a pump?

[argoldman]

But using a pump will not allow you to use both slow and fast hardener - right? I like to use about 3/4 slow and 1/4 fast - gives a good compromise of cure time and working time for my workshop. As the weather gets warmer, I can use less fast as desired. How could you do this with a pump?

Yes,Phil there is an epoxy pumpaclaus.

 

you can adjust the ratios using a pump by the following method.

 

Keep a small amount of your desired "hardener" mixture in the reservoir of the pump. As you get more experience with the pump, you will know the amount to keep there. When you want to change the ratios just add more "hardener" in the ratio that you want using slightly more of one or the other to compensate for the small amount of improper ratio which still remains in the pump. Stir the new mixture with a chopstick or similar. You can fully load the clear resin (part A).

 

In actuality, you will settle on a specific ratio that you find works well for you for most parts and only in specific incidences will you want to change it.

 

Do not ever use only slow hardener. I understand this yields a more brittle cured epoxy

[TMann]

Do not ever use only slow hardener.

First I heard this one. Is this based on experience, forum feedback, MGS?

Is this true about 285, 335 or both?

I just switched to 335 and am using the slow hardener and would appreciate some info on the subject.

[Jerry Schneider]

Do not ever use only slow hardener. I understand this yields a more brittle cured epoxy

The way I read the specs, if you're operating your plane in the g-force realm where the difference in flexibility of the cured epoxy is a structural factor, you've probably already exceeded the operating limits of the human body.

IMO, the slow hardener epoxy is plenty flexible enough for our purposes. (Especially considering the designer gave his blessing to 335 without any caveats which I'm aware of.)

 

Just my opinion......

[argoldman]

First I heard this one. Is this based on experience, forum feedback, MGS?

Is this true about 285, 335 or both?

I just switched to 335 and am using the slow hardener and would appreciate some info on the subject.

 

It is with the 285, don't know about the 335.

 

I don't know where I read it, possibly the data sheets from MSG, but I remember not to do it, even though I hadn't planned on it.

 

Sorry I can't be more specific. A call to the MGS distributor will probably clear up that questioin

[Jon Matcho]

Do not ever use only slow hardener. I understand this yields a more brittle cured epoxy

I don't know where I read it, possibly the data sheets from MSG, but I remember not to do it, even though I hadn't planned on it.

Try this to see how brittle 285 mixed with 100% slow hardener is:

• Layup 1 or 2 plies of 1" x 6" using MGS 285 with 100% slow hardener.
• Let cure @ 65+ degrees F for 24 hours.
• Bend your layup into a circular tube.
• Repeat the bend so that the other surface is on the outside.
• Release and watch the layup return to its original form, with no signs of cracks or damage.

Sorry I can't be more specific. A call to the MGS distributor will probably clear up that questioin

Not necessary IMO. I'm going to continue using 285 w/slow without worry.

[jpolenek]

Here's some info I just received from Composites Canada, comparing MGS and Aeropoxy. I can't speak to any of the details of the testing, but the vendor supplying the info is fairly reputable. Apparently, both systems are equally good without post-cure, while MGS is better if post-curing.

 

Joe

Test_Data_MGS_vs_Aeropoxy.doc

[TMann]

MGS does not stink the place up (which comes in handy if you plan on moving your operation inside during the winter.)

[Ron Springer]

Here's some info I just received from Composites Canada, comparing MGS and Aeropoxy. I can't speak to any of the details of the testing, but the vendor supplying the info is fairly reputable. Apparently, both systems are equally good without post-cure, while MGS is better if post-curing.

 

Joe

If the numbers are correct, then they mixed the MGS incorrectly. The correct weight ratio is 100:40 (+/-2), so they were even outside the tolerance.

[jpolenek]

What factors determine which MGS epoxy to use, 285 or 335?

 

Joe

[Jon Matcho]

What factors determine which MGS epoxy to use, 285 or 335?

How much money you have in your wallet and whether you want the slightly improved properties of 285. Both are approved epoxy systems.

[Len Evansic]

Here's some info I just received from Composites Canada, comparing MGS and Aeropoxy. I can't speak to any of the details of the testing, but the vendor supplying the info is fairly reputable. Apparently, both systems are equally good without post-cure, while MGS is better if post-curing.

 

Joe

One thing to note with this particular test is that both MGS and Aeropoxy look absolutely equivalent when you add a reinforcement to either. This particular test is showing primarily the strength of the fiberglass, not the epoxies.

 

When you look at the data for the epoxies only, MGS 285 is "superior" to Aeropoxy in that it has higher numbers for just about every entry. When you add a reinforcement into the mix, the fiber dominates the test results, as its strength is much higher than the epoxy matrix, no matter which epoxy you use.

 

Two things to note in this test are the tensile strength and the elongation achieved. ~40 ksi is about four times higher than the strength of either of these epoxies, while ~1.5% elongation is about a third of what the epoxies will typically handle. What this is showing is that the glass used for this test has a ~40 ksi tensile strength and ~1.5% elongation when loaded at the fiber orientation used. When the glass breaks, the stress is already well above that of either epoxy, so they fail. In this case, both epoxies are equivalent.

 

Now, what this testing doesn't show, is which epoxy would be a better structural adhesive for our purposes. The structural epoxy has to do its work on its own, dealing with peeling and shear loadings where the epoxy itself is the dominant load carrier. For this type of information, lap shear testing is the best indicator. This is the type of testing that the epoxy manufacturers should put out for their products. Unfortunately, that information is hit and miss between the different formulators, and the easier to test consistently tensile strength is what is normally published. Tensile strength is somewhat related to the shear strength, but surface preparation, reinforcement material and weave, etc. all contribute to this type of testing being difficult to reproduce or quantify effectively.

 

-- Len

[jpolenek]

If the numbers are correct, then they mixed the MGS incorrectly. The correct weight ratio is 100:40 (+/-2), so they were even outside the tolerance.

The numbers shown were not correct. I brought this to the attention to the vendor. He called the lab to confirm that they did in fact use the correct ratio for the tests, so this was a typo. He walked me over to the display version of the chart that was posted in the store, and it had the correct numbers.

 

Joe Polenek

[jpolenek]

One thing to note with this particular test is that both MGS and Aeropoxy look absolutely equivalent when you add a reinforcement to either. This particular test is showing primarily the strength of the fiberglass, not the epoxies.

 

When you look at the data for the epoxies only, MGS 285 is "superior" to Aeropoxy in that it has higher numbers for just about every entry. When you add a reinforcement into the mix, the fiber dominates the test results, as its strength is much higher than the epoxy matrix, no matter which epoxy you use.

 

Given that we always use epoxy to reinforce something (mostly glass and sometimes fillers), the "superiority" of MGS on it's own is academic. It seems that the quality of the lay-up (correct epoxy content, fiber orientation & straightness) has a far bigger effect on the strength of the lay-up than which of these epoxies is used.

 

Joe Polenek

[Jon Matcho]

One thing to note with this particular test is that both MGS and Aeropoxy look absolutely equivalent when you add a reinforcement to either. This particular test is showing primarily the strength of the fiberglass, not the epoxies.

I wonder, then, if the epoxy analysis we do is just another case of us homebuilders obsessing over specs in areas of no real consequence. If the epoxy is "good enough", maybe we *should* be making our preference based on how well it wets out, its smell, etc.

 

There are many beautiful planes built with "other" APPROVED epoxy systems.

[jpolenek]

If the epoxy is "good enough", maybe we *should* be making our preference based on how well it wets out, its smell, etc.

... price, availability, whose economy you're supporting when you buy it, ...

 

Joe Polenek