MOGAS in Fiberglass Fuel Tanks

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HomeBuilt101

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My airplane is fiberglass and the fuel tanks are coated with "JeffCo" and I was thinking of running MOGAS mixed with AVGAS 100LL.

The engine will be able to run on MOGAS and the Bendix has been converted to work with even alcohol blended fuel however my only concern is the fuel tank coating.

I called the company that bought the JeffCo coating and they said that lots of boats run auto fuel in their coated tanks so that sounded good however I wanted to ask the group (lot of EZ/ Cozi/ Velocity people here with decades of experience) if they had any direct knowledge with MOGAS in their fiberglass with JeffCo coated fuel tanks.
 

Marc Zeitlin

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My airplane is fiberglass and the fuel tanks are coated with "JeffCo" and I was thinking of running MOGAS mixed with AVGAS 100LL... The engine will be able to run on MOGAS and the Bendix has been converted to work with even alcohol blended fuel however my only concern is the fuel tank coating...
So "JeffCo" is not specific enough to say anything whatsoever. If you look at the Rhino Epoxy website, you can see that they make a LOT of different epoxies. Most likely, the epoxy Velocity used was the 1307-LV Resin with the 102B slow hardener (but these are only guesses).

There is no mention of alcohol resistance in any of the resin or hardener data sheets. Alcohol is the issue here - if the Mogas you're using has no alcohol, you're generally safe to use it. If it does have alcohol in it, the safest thing is NOT to use it unless the epoxy formulators can tell you that it's safe to do so. Many folks have had coupons of epoxy soaking in various fuels for upwards of 20 years now, and have measured how much weight loss there is in the coupon. Generally, EZ-Poxy 10/87 had the best results, but that doesn't mean that other epoxies are not acceptable - MGS generally performed well, as did a few others.

So if you ask me, if there's alcohol, don't use it. If there isn't, you're very likely to be OK.

And boats, well, don't really give a FF about weight like airplanes do, so they'll have much thicker tank linings (as well as thicker everything else, too) - lose 1% of the lining/year (handwaving) and the boat will still work fine in 20 years. Not so much in an airplane.
 
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Worth remembering that Jeffco is the name of an entire product line. They have a couple products that they sell specifically as fuel-resistant coatings, but they have a lot of other epoxies as well. So when you say "Jeffco" you could be referring to any number of products.

At a glance, the product you're probably referring to is Rhino 9700A/B, a gray sealant coating. The specs make it look like pretty good stuff. We just used it on a Reno racer project, but we have no plans to use anything but 100LL or smoke oil in those tanks.

 

Marc Zeitlin

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At a glance, the product you're probably referring to is Rhino 9700A/B, a gray sealant coating...
@BoKu is right here - that's probably the coating that was used, assuming you're talking about a coating, and not the laminating epoxy used for constructing the tanks.

HOWEVER, if you read the data sheet pointed to, you can see that in the chemical compatibility matrix, "Mogas" is listed as having a 0% weight loss in 3 weeks (which is a minuscule period of time to measure - not quite useless, but close. They should use a year. But whatever...) while "Ethyl Alcohol" shows a 6.9% weight loss in 3 weeks :fear::fear::fear:. So I'd still go back to my statement regarding alcohol - if there's any chance that the fuel you're using has alcohol in it, don't. If it doesn't, you're almost certainly OK.
 

Skippydiesel

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I flew an ATEC Zephyr, fiberglass fuselage with integrated fuel tank, for over 10 years. Fuel - mainly 98 RON, occasionally 95 RON, very rarely AvGas. Never knowingly used fuel with any Ethanol content. Never had a problem. Only minor issues was cockpit needed to be "aired" for a few minutes after being closed for a few days. I think this was due to the glass having a slight vapour porosity.
 

tspear

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I have a thread I started on here for composites and alcohol. A few leads for possible composite and alcohol compatibility. However, no definitive answer on how to make composites work with alcohol.
Based on that, I would avoid any fuel with ethanol and composite structures.

Tim
 

BJC

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I have a thread I started on here for composites and alcohol. A few leads for possible composite and alcohol compatibility. However, no definitive answer on how to make composites work with alcohol.
Based on that, I would avoid any fuel with ethanol and composite structures.
I enjoy both: slow building a Glasair, and, in the evenings, enjoying a neat Crown Royal. But, they don’t go together.


BJC
 

speedracer

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So "JeffCo" is not specific enough to say anything whatsoever. If you look at the Rhino Epoxy website, you can see that they make a LOT of different epoxies. Most likely, the epoxy Velocity used was the 1307-LV Resin with the 102B slow hardener (but these are only guesses).

There is no mention of alcohol resistance in any of the resin or hardener data sheets. Alcohol is the issue here - if the Mogas you're using has no alcohol, you're generally safe to use it. If it does have alcohol in it, the safest thing is NOT to use it unless the epoxy formulators can tell you that it's safe to do so. Many folks have had coupons of epoxy soaking in various fuels for upwards of 20 years now, and have measured how much weight loss there is in the coupon. Generally, EZ-Poxy 10/87 had the best results, but that doesn't mean that other epoxies are not acceptable - MGS generally performed well, as did a few others.

So if you ask me, if there's alcohol, don't use it. If there isn't, you're very likely to be OK.

And boats, well, don't really give a FF about weight like airplanes do, so they'll have much thicker tank linings (as well as thicker everything else, too) - lose 1% of the lining/year (handwaving) and the boat will still work fine in 20 years. Not so much in an airplane.
My hanger partner Dan built an aluminum back seat gas tank for his Varieze so he could run car gas + alcohol. When the cheapskates all get together they call Dan "The Boss." He did just buy a new Tesla. Paid cash.
 

TFF

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In the RC world, denatured alcohol has been used to thin epoxy, right or wrong. Clean tools from epoxy also. It can mix. We the airplane community take epoxy as non porous. The boat community considers it porous. They know modern epoxy is pretty darn good, but they still paint over and varnish over if the boats stay in the water. A dingy or canoe gets taken out and never has years of constant soaking.

Alcohol free fuel should not have the same issues except maybe purity questions at the pump.
 

Voidhawk9

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My understanding is that a good post-cure increases the chemical resistance of epoxy significantly.

From where I am looking today, I am moving ahead assuming that there will be ethanol and who-knows-what in the fuel going into the tank at some point. Given that this is likely to come down to the whims of some idiot politician, I must assume the worst.
 

Skippydiesel

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My understanding is that a good post-cure increases the chemical resistance of epoxy significantly.

From where I am looking today, I am moving ahead assuming that there will be ethanol and who-knows-what in the fuel going into the tank at some point. Given that this is likely to come down to the whims of some idiot politician, I must assume the worst.
Wise man - you can never be absolutely sure that the fuel you get from a petrol station does not have some "other" components. You just have to look at how its transported to surmise that contamination could occur (diesel, E10, H2O).
 

flyndude

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Good information and always THANKS.

How does one find non-alcohol fuel
Our state (Ohio) and many others require an alcohol blend for highway use. For several years the only place I could get fuel without it was at marinas. The last few years a few local stations have stated selling "recreational" fuel without alcohol for off road use only. I have a airplane that has fiberglass tanks that are supposed to be alcohol "resistant" but it still caused so many issues the manufacturer dropped them and went to aluminum.
 

Pops

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Wise man - you can never be absolutely sure that the fuel you get from a petrol station does not have some "other" components. You just have to look at how its transported to surmise that contamination could occur (diesel, E10, H2O).
I check all auto fuel I put in the airplane for ethanol. In this state ( by law) all pumps are to be labeled as having ethanol. One time I put some auto fuel in my C-172 from a pump that was not labeled as having ethanol and cost me a carb overhaul, new fuel hose to the carb and a fuel valve overhaul.
 

Bob H

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The Pulsar community has been concerned about ethanol affecting glass tanks for years. I have been flying mine for 18 yrs and we can not get any ethanol free mogas in Calif. You absolutely need a protective coating on the glass. The Rhino 9700 was the initial choice as it is a novolac and has high chemical resistance to fuels. But it is brittle and any flexure in structure causes cracking and exposure of fuel to glass. You want a polysulphide coating over the glass because it is flexible and immune to fuels and ethanol. Problem is getting it inside glass tank. I used a poly brushable coating from Spruce, Aerolife 2-part, successfully for last 6 yrs on integral glass wing tanks. There may be other brushable polysulphides that will work. Bare glass structure exposed to ethanol will degrade the epoxy in time and leak.
 

Daleandee

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