New wing tanks

[Vande17941]

Are the new tanks from kitfox compatible with unleaded fuels that may contain ethanol? (california😣). Any issues with new tanks that I need to be aware of?

[GuppyWN]

They are “ethanol resistant.” Kitfox recommendation is 100LL w/decalin. I run 91 ethanol free in my 912ULS.

[Vande17941]

What does this mean "resistant"? If that is the case, why are they recommending 100LL? Obviously I would like to use mogas because it's a 912. So what's the real truth of what the tanks can handle?

[GuppyWN]

You’d have to ask the factory but I think the answer is even they aren’t sure. If you have iOS you can download an app called Pure Gas and it will help you locate ethanol free gas. I quality control check by partially filling a small jar with gas and putting a single drop of food coloring in and shaking it. If it’s ethanol free the food coloring will remain solid and balled up. If it’s got ethanol in it the food coloring will look diluted.

[jiott]

The new tanks do fine with ethanol free Mogas; I have been running nearly 100% clear Mogas for 750+ hours with no problems at all. I can't speak to Mogas with ethanol because I have not run it.

My understanding of Kitfox factory recommending 100LL is not because of the tanks or fuel system compatibility, but is their belief that Mogas can be dirty, unknown additives, possible water, potential vapor lock, limited availability, and possibly other reasons. I usually run my Mogas thru a filtering funnel and have NEVER seen any water or dirt in my fuel samples. I personally (and Rotax factory seems to agree) believe the very small risks of using Mogas is not nearly as bad as the detrimental effects of lead sludge and deposits from 100LL, even with Decalin. I personally know several others, and there are many more on this forum, that run Mogas nearly exclusively for many years with no problems. Most of us do try to get Mogas without ethanol.

[jiott]

This is just an opinion, but I have a hunch that Kitfox Factory (and also Stick & Rudder) recommend 100LL because of the typical legal liability issue. They both deal with the general public and by going with the standard 100LL they eliminate any liability that MIGHT occur if someone has a serious problem with a bad batch of Mogas. No one is going to have a sudden engine failure due to 100LL, its more of a long term engine life issue. Each of us must weigh the issues and make our own decisions-end of my 2 cents worth.

[KitfoxSS]

Kitfox markets the tanks as being Ethanol "Resistant".
This is ethanol resistant, not ethanol proof.
If it was ethanol proof that would mean the fiberglass tanks would take ethanol all day everyday into the future for the life of the tanks with out issue.
This is not the case as ethanol is some corrosive stuff. The fiberglass tanks are treated to be resistant to ethanol. Meaning you can run it and it'll be ok but continued use over a long period of time and the ethanol will eventually start to effect the fiberglass.

[Vande17941]

How about using a sealer on the fiberglass tanks such as BILL Hirsch Fuel Tank sealer? It's supposed to he resistant to all the additives and ethanol.

I'm in Calif....no ethanol free gas here

[jmodguy]

How about using a sealer on the fiberglass tanks such as BILL Hirsch Fuel Tank sealer? It's supposed to he resistant to all the additives and ethanol.

I'm in Calif....no ethanol free gas here

Skystar lined their tanks with Kreem. It was not optimal. Newer resins that are more resistant are being used now. S&R uses 100LL with decalin and Paul told me it works just fine.

[KitfoxSS]

How about using a sealer on the fiberglass tanks such as BILL Hirsch Fuel Tank sealer? It's supposed to he resistant to all the additives and ethanol.

I'm in Calif....no ethanol free gas here


You can, in fact I had planned when I eventually get to building to use Caswell's Tank sealer. It's a two part epoxy instead of a one part like Kreem or Por15.
From everything I've read it's highly rated.

[HighWing]

I've been reading this and have a few thoughts. My first Model IV started flying in 1998 and I used mogas except on cross countries for nine years. California mandated all mogas have 10% ethanol in 2004. The original tanks were kreemed, and I re-Kreemed one tank bacause of some discoloration on the fabric below the tank. I then flew until late 2007 - three years with ethanol containing mogas primarily. My new Model IV has the Denney Aerocraft tanks with Kreem. I am using 100LL primarily because my flying is spotty and I have had serious issues with the mogas in infrequently used garden equipment and didn't want the same type issues in my Kitfox. I do use Decalin with the 100 LL. Then an article in the last issue of Sport Aviatrion - page 120 - talks about the pros and cons of mogas vs. avgas and in the article it mentions that the new Shell - Sport plus 4 has additives that keeps the tetra ethyl lead in suspension. It makes me wonder if the additive Shell uses would preclude the need for the Decalin. In other words, since Shell is adding an additive to the recommended oil that essentially does the same thing as the Decalin additive - is Decalin use still necessary.

[jiott]

Good question Lowell, my understanding of Decalin is that it actually alters the chemical composition of TEL when it is burned so that the residue (not 100% but a lot) is able to be blown out the exhaust rather than forming lead deposits on valves and piston rings. There are more in-depth discussions of this in the forum. Again, my opinion only, but the additive in Aeroshell Sport Plus 4 keeps the TEL in suspension in the oil that has been contaminated with UNburned fuel. All engines have a certain amount of unburned fuel that sneaks past the piston rings and into the crankcase oil. Therefore I would think that if you burn 100LL you would want to use both Decalin AND an oil with that additive. The Rotax gearboxes are very susceptible to lead deposits from the contaminated oil.

[jiott]

Regarding tank coatings, the older Kreem types or even newer stuff, I have seen way too many reports in these forums over the last 6 years I have participated of folks having serious problems with it flaking off and seriously plugging screens and filters. Mind you there are also many that swear by the stuff. To me it is too high of a risk of catastrophic engine starvation. If my uncoated new style ethanol "resistant" tanks SLOWLY over the years start to soften and even spring a slow leak, I think that would not be catastrophic and most likely would give plenty of prior warning-a much better risk situation in my mind. I would stay totally away from any kind of coatings in the newer tanks.

[JamesD]

I have a 2000 model skystar series 5. here in Australia they do not sell ethanol gas without stating. my tanks have been dry for 6-7 years due to being ground looped then i purchased it. they look very good and i am confident they with be fine and most likely would of had only 100LL over their 750hrs in use. should i be concerned as i am currently re bagging the wings but changing the tanks is one hell of a job for nothing.

[Maverick]

I am building a series 5 kit manufactured in 1994. The original tanks look fine but, because I haven't yet installed the tanks, I have ordered new ones. Because of the recent article about what fuel to use in a Rotax engine showing advantages and disadvantages of 100LL versus auto-fuel, I figure that with the newer tanks, it won't matter what I finally end up using. (see article in August 2019 Sport Aviation, page 120).

[jiott]

I would recommend calling the factory to find out when they started supplying the new tanks in the kits. If yours are the old ones, I personally would change them out to the new ones. Fuel system worries are one thing I don't want to have-its too critical. Just my 2 cents.

[Av8r_Sed]

My early 90’s vintage Denny Aerocraft tanks have only seen ethanol free and 100LL. They’re fine and I’ve had no trouble with them. Even the Kreem sloshing is in good shape. I wouldn’t be concerned with yours. Might want to check them for leaks though before you (re)cover the wings.

[markwalker]

I recently purchased an early 1990's kitfox 4 that has a little flaking around the tank necks. Will This continue if I only use only
non-ethanol or 100 low lead or is it too late and the tanks need to be resealed or replaced?

[bumsteer]

Mark

I'm by no means an expert on the fuel tanks, so I won't even try and answer whether or not the tanks are usable. Given that there is some flaking, I think would warrant further inspection. Unless you can get a camera or borescope inside you really don't know what is happening inside. Have you pulled the finger strainers to check for flakes. Others who have had this problem can probably provide more insight on what to look for. Good luck.

Rick

[markwalker]

Thanks for the information!!!! I will do my due diligence with the tank inspection and plan to use 91 octane ethanol free unleaded for regular use and 100 LL when on trips if ethanol free is unavailable.

[Auster]

I have a 2000 model skystar series 5. here in Australia they do not sell ethanol gas without stating. my tanks have been dry for 6-7 years due to being ground looped then i purchased it. they look very good and i am confident they with be fine and most likely would of had only 100LL over their 750hrs in use. should i be concerned as i am currently re bagging the wings but changing the tanks is one hell of a job for nothing.

James this is not a definitive answer, just a sharing of experience. My Skystar S5 is about the same vintage as yours, first flying in 2007. It now has nearly 500 hours, 90% of which has been on 95 or 98 octane Mogas. Much of that had 5% ethanol. The remaining hours were on 100 LL avgas, when I could not obtain mogas. I am in Europe and we have very good quality fuel delivered to our airfield. Only rarely, on trips, have I used fuel from a local garage.

After reading of issues with earlier model Kitfox fuel tanks I've decided to do an annual check on the tanks - which were treated with Kreem as part of the build process. At the last inspection we drained them completely, including removing the fuel drains. No dirt or contamination was found. We then used torches to visually check the security of the Kreem. It is in good condition except for some cracks where the baffles join the skin - that right angle join - a known problem area on early Kitfoxes. While a little concerned about the cracks we decided that this was not yet causing any issues e.g. no flaking of the Kreem or leaking. We also decided to continue this annual inspection.

In your case I would proceed but keep a close eye on the security of the Kreem at the baffle joints and, as far as possible, avoid ethanol, but keep in mind that fuel without ethanol might be difficult to obtain in the future.

[4Hummer]

This is what ethanol does to the original Kitfox IV tanks


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[Spook712]

Did you leave the Mogas in the tanks while the aircraft was not used?

I use Mogas here in Germany as well and after flying i drain the tanks to store the plane with empty tanks.


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