# Aircraft Epoxy, Marine Epoxy what's the difference?

Discussion in 'Composites' started by aeroknot, Jun 17, 2018.

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1. Jun 17, 2018

### aeroknot

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Aircraft Epoxy, Marine Epoxy what's the difference?
I am starting the research for building a LongEZ or Cozy Mk IV. The groups and instructions all talk about "Aircraft Rated Epoxy".

What's the difference between aircraft and marine epoxies?

I understand the stresses are somewhat different, flex and stress vs pounding a 2 - 3,000+ lb boat into crashing waves.

I can buy marine epoxy wholesale for $40 per gallon, vs paying retail (from spruce) for aircraft epoxy. Could sure use some help here. 2. Jun 17, 2018 ### Kyle Boatright ### Kyle Boatright #### Well-Known Member Joined: Nov 12, 2012 Messages: 737 Likes Received: 371 Location: Marietta, GA Your best bet is to compare the specs on the recommended epoxy with any alternatives you are considering. That'll tell the tale. Remember - homebuilders and plans sellers are thrifty. They are probably already using/specifying the least expensive materials that produce the desired results. 3. Jun 17, 2018 ### Aerowerx ### Aerowerx #### Well-Known Member Joined: Dec 1, 2011 Messages: 4,794 Likes Received: 1,279 Location: Marion, Ohio Not an expert, but the two main contenders are West System and System Three (T88). I have seen both for sale on both aircraft and boat-building web sites. IMHO, if your$40 per gallon is one of these, go for it.

4. Jun 17, 2018

### TFF

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Strength and heat resistance. The racing boat people use the airplane stuff. You could always use the "Goop" from that Elvis boat movie.

5. Jun 17, 2018

### Turd Ferguson

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and you'll probably get the same thing. Not sure there is any room temp curing "aircraft epoxy" other than the label.

6. Jun 17, 2018

### Marc Zeitlin

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Nothing, because there's no such thing as "Aircraft" epoxy or "Marine" epoxy. There are epoxies that designers have chosen based on their properties to ensure that the specifications of the device in question (aircraft or boat) will be met. If you use an epoxy that was not approved by the designer, then maybe those specifications won't be met, and you may either fall into the water or out of the sky.

Since you're interested in LE's or COZY's, there is a clear list of approved epoxies that can/should be used, and you should pay attention to it, particularly to the fact that the best epoxy for the strakes/fuel tanks is the EZ10/87 due to its fuel resistance capabilities. There are reasons NOT to use particular epoxies as well - the West 105/205/206 are NOT approved due to the low pot life and high exotherm probability on structural (read thick) layups.

In the grand scheme of things, the cost of the epoxy is a tiny percentage of the total cost of the aircraft - don't skimp here.

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7. Jun 18, 2018

### Vision_2012

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I just calculated, epoxy was 6% of my build.

8. Aug 15, 2018

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West System 105/206 is not a bad all-around resin system. I would advise to look into the PTM&W (Aeropoxy) PR2032 & associated hardeners. They are known products intended for aerospace composite applications. I did a healthy bit of research into the EcoPoxy systems. Even went as far as fabricating a couple load test beams and used it to fabricate a 1/4-scale RC test model for my design. Loved it. No nasty smell, and completely non-toxic. It even seemed to satisfy our design requirements. However, EcoPoxy was unable to produce any documentation for me regarding mechanical properties; of which not knowing them could not allow us to adequately validate our test results, which is unfortunate. I also have not tested it for fuel resistance or UV exposure, so I cannot openly recommend EcoPoxy. I would also recommend looking at the EZ-Poxy products from Endurance Technologies. EZ-Poxy effectively replaced Safe-T-Poxy from the old RAF days.

As an engineer, I cannot stress it enough- follow the plans verbatim as if your life depends on it. Kudos to you for getting on the net and at least asking the question!!

9. Aug 15, 2018

### BJC

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My understanding is that the “non-toxic” description means “for most people” but not necessarily for all people, and that direct exposure to the resin should be minimized, as should exposure to the fumes.

Did your research show that my understanding is not accurate?

Thanks,

BJC

10. Aug 15, 2018

### wsimpso1

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West System is used a bunch for composites, but it is intended for wooden boats reinforced with fiberglass. It does have a tendency to exotherm in thicker laminations...

I played with Aeropoxy and found that in my fairly high humidity environment, it makes a bunch of amine blush upon cure. Why bother when other stuff does not.

All epoxies I know about are sensitizers. Get enough exposure and you will be sensitized to it - that means become allergic to it! Some are better than others, but you have to protect yourself from all epoxies. Gloves, chemical masks, immediate cleanup of any on skin or clothing. etc. Prudent builders will do the same thing with polyesters and vinylesters too.

Absolutely on both points!

Billski

Last edited by a moderator: Aug 15, 2018
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11. Oct 21, 2018

### rsrguy3

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I haven't been in the threads for a while, so please forgive my ignorance. Where does the MGS line stack up on the cozy long ez approved list?

12. Oct 21, 2018

### don january

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I found the best thing to do with glue is make that one extra part first and use your hands and shoulders to feel to decide if your going farther with that batch. also gives a good chance to check the wood. And on fiberglass say a root rib nothing saying you can't put a false rib a few inches out to see how it holds usually wing walk area. Each tube is different and you go as far as you can with a good batch.

13. Oct 21, 2018

### lr27

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I think stuff like West is general purpose. Might not get the same mechanical properties, but can be used as glue if you thicken it. I have some epoxy from a boatbuilder that's meant for wetting out composites. It's great for that, but makes lousy glue. It would probably be great for airplanes, but I don't have any documentation for it and wouldn't count on it.

Anyway, the best epoxy to use depends on what you're using it for. If you're not going to use what's recommended in the plans, you'd better do your homework. It could be that someone already HAS, but you have to find their info and decide if it's reliable.

As expected, I find Marc Zeitlin has some info on his site.
http://www.cozybuilders.org/ref_info/

14. Oct 21, 2018

### lr27

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BTW, I've had good luck with the vanilla flavor of RAKA for boats, and I wouldn't hesitate to use it for non-structural purposes. I'd paint it white if it was going to be in the sun. Comparable to West, I think. They have some other flavors. But I'd do some homework before I'd use any of them on anything requiring high performance for safety. I'd want to know more about quality control, for one thing, though my own experience with it has been fine. Might be good for practice pieces, etc.

15. Oct 22, 2018

### proppastie

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16. Oct 22, 2018

### dcstrng

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This may be taking this discussion beyond the ordained confines of the original parameters (discussion creep), but I’m wondering about epoxies/adhesives and wood… I’m pretty familiar with WEST and have used it for about everything over many years (zero experience with System Three/ T88), but I’m looking closely at a 50-60s design of Kaminskas’ that instructs the builder to use Aerolite 300 (which seems nearly impossible to find).

I’m okay with the urea-formaldehyde stuff if it can be used in cooler weather as my shop cools to 45-55 degrees F which makes epoxies problematical (I don’t mind using fast set techniques for marine, but am not at all sure about it for aviation’s). Thoughts??? Where to get aviation grade Aerolite 300 ??? Is the ACS resorcinol formaldehyde adhesive similar??? Weldwood… ???

Ideas, notions? Thanks… (this is what happens when you take someone who is familiar with acetylene and turn him loose in a woodshop...)

17. Oct 22, 2018

### lr27

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T-88 is supposed to work at low temps. Better paint your airplane white, though.

18. Oct 22, 2018

### TFF

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I think the big rule is if it's cold, don't glue period. If you want to test the limits of the temp glue range, you will loose and so will the glue. Minimum of 10 deg warmer than the package says but really needs to be at least 75F in the real world. Tons of stories "well it said 55" and the parts don't stay together. Small parts you can build a hot box. Spars, smack in the middle of the living room if I had to do it in the winter or wait for the thaw. Weldwood's bad rap is from cold application and no one dare with recorcinol.

19. Oct 22, 2018

### dcstrng

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Hmmm… well I guess I sorta sensed all along that acetylene (tube and fabric) was user friendly (especially in cooler weather), just didn’t realize how much… I’ve usually curtailed my boat WEST system stuff when the hull gets below 65-deg, but nearly everyone in the aviation community raves about T88 and their literature talks about working into the 40sF, so I thought they must be the holy grail… no magic bullet, eh…

20. Oct 22, 2018

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