fuel tank epoxy ?

[Ratdog]

I just bought a long eze project and the strakes are completed and supposedly the fuel tanks pressure tested.  It was an early build how do i know if they used the right epoxy in 

the fuel tank area?

[Marc Zeitlin]

53 minutes ago, Ratdog said:

... how do i know if they used the right epoxy in the fuel tank area?

What's the "right" epoxy?

Do you have the build logs?

Can you see inside the tank, and see the color of the epoxy?

If you don't put alcohol containing gas in the tank, it pretty much doesn't matter which epoxy was used, as long as you post-cure the tanks.

[Ratdog]

I dont actually have the project at my house yet . It was sort of a deal i couldnt refuse so once its transported here i can look at that .  I was just looking through the long eze build online and it was talking about using the right epoxy for the fuel tank or it would decay .  Thanks for the input i will know more in a few weeks . 

[Ratdog]

From my research ez poxy is fuel resistant where aero poxy is not and will start to dissolve if used in the fuel tank.  So i dont know how you tell what epoxy was used .  there are no build logs. 

[Marc Zeitlin]

3 hours ago, Ratdog said:

From my research ez poxy is fuel resistant where aero poxy is not and will start to dissolve if used in the fuel tank.

Do you have a pointer to the "research" that indicates that AeroPoxy is problematic in fuel tanks?

[Ratdog]

This is a quote from Aryiglantz extensive long eze build website .  "  I decided to use Aeropoxy (PR2032 & PH3660). Note however that Aeropoxy is NOT fuel resistant; therefore, Aeropoxy should NOT be used with any surface that comes in contact with fuel. This includes portions of the aft fuselage, center section spar and obviously - the strakes which contain the fuel tanks.

It's been said that EZ-poxy is fuel resistant; however, the manufacturer (Endurance Technologies) does not claim that it is. Instead, they publish charts that show how much weight change of a test article occurs overtime while it is submerged in various types of fuels. In short, one can expect approximately 0.4% weight reduction over a one month period. Does the fuel continue to dissolve the composite after that 30-day period? They wouldn't comment. I haven't done enough homework to conclude what the best course of action is - I will update this section as I get closer to building the fuel tanks.

EZ-poxy comes with a huge health warning label on the container ("DANGER - contains MDA - contains materials which may cause cancer liver toxin"). Aeropoxy does not. For this reason, I am building most of my parts with Aeropoxy and only using EZ-poxy when I have to (i.e., parts that will come in contact with fuel)."

if mine was an early build they probably used RAE? epoxy which is what Rutan specified in the plans .  That must have been something Rutan was selling if you know anything about that please let me know. 

[Ratdog]

Looking for more info on the internet it sounds like in general fuel does attack the bonds in epoxy substrates.  Lots of automotive oriented sites say to not use epoxy for fuel tanks .  Obviously in a practical sense there are thousands of homebuilt aircraft flying around with epoxy fuel tanks .   I looked on the Aeropoxy website and they dont mention anything about fuel tanks.   Im not sure how Ary Glantz found this information.   

[Marc Zeitlin]

The links regarding epoxy and fuel resistance on the internet are generally referring to auto fuel, which has Cthulhu knows what in it, that also varies with the time of year. Mostly, alcohol, which will attack some epoxies.

If you don't know what epoxy was used for the fuel tank, just make sure that you post cure the tanks to get the best chemical resistance you can. Assuming you don't use automotive fuel (either 100LL or the 94/100 octane no lead replacements that are coming), you should be fine. Fuel tanks have been fabricated with all the various laminating epoxies that have been used to build canards. In only a very few cases (and never linked directly to the epoxy used) have there been issues.

[Ratdog]

Thanks Marc