Leaking wing tanks.

[Docspenc]

Hi all.. I have a kitfox 3 with 6 gallon aluminum wing tanks.. yes and they both leak. I've read some of the posts on hear but I'm still not sure how to proceed.. or where to buy replacements. Any thoughts? Thanks in advance..

[atosrider]

the RV homebuilts have owner made alu tanks, it's not impossible to take that project on .. I don't know if they have a suspension system to allow for the wing twist that the KF building technique imparts on the tanks ...
given the warning of no ethanol in the 'plastic' tanks that are available for the KF models, like why go ahead with that option, I find it odd that the KF homebuilders have avoided solving the suspension problem for going with alu tanks ...
I was lucky, a local RV builder (and so much more) lead me through building a new alu header tank, easier because it is all flat surfaces ... why not make 4 x 5gal tanks in alu, should provide lots of room for suspension ...

[Av8r3400]

"Suspending" the tanks is not possible because the tanks are structural to the wing in the Kitfox design. The tanks act as the drag tubes in the first rib bay of the wing.

To the original poster, there are or were until recently, at least a couple of people making ethanol resistant, fiberglass tanks for Avid Flyers, which would be "close enough" to use in the early model Kitfoxes. Maybe Avidflyer will chime in, this is more of his area of expertise.

[Docspenc]

What's the best way to remove the tanks? That bay is covered with 1/8 inch plywood, and I think that's what gives the wing strength. The tank is held in with rivets on the rear spar and silicon on the front spar. At least that's what the build book shows.
Also does anyone know who might make them? I don't think I want to make one myself.

[avidflyer]

I did see on the Kitfox facebook site that someone in Europe had a set of early 6 gallon Kitfox fiberglass tanks for sale. His name is Georgi Georgiev and he posted on December 9. One has a small crack, $300 for the pair. Shipping would kill, but may not be that bad considering his asking price. I sloshed aluminum tanks on an Avid Flyer once and they held for a while, but started leaking later. JImChuk

PS I've wondered if one was to fiberglass over the aluminum, kind of use it for a left in place mold if that would work. It might....

[atosrider]

pity that the early KF / Avid models placed so much emphasis on keeping the weight down, then combined with wanting the wing fold feature, the result is too much flexing in the first two bays - question, did the 13gal tank option only come out for the model 4 wing? is the 4 wing structure built stronger in this section?

adding some sleeving to the wing spars past this section might replace the cross bracing, in combination with heavier cross bracing mid-span .. oh, best I shut up, I'm not a structures guy .. tip tanks? oops, nice CoG positioning but different loading on the wing ...

some day I expect to be needing to replace the original model 4 tanks, not looking forward to that task, and hoping there will be a new replacement tank manufacturer willing to ignore the liability issues of this industry that has constrained progress for decades

BTW, what is the current tank solution in the newest kits? can it be used in early model 4 wings?

[Av8r_Sed]

My Model III has factory 13 gal fiberglass tanks (not Ethanol safe). They're still holding fine since I've always used non-Ethanol gas (thanks Wisconsin!).

[FoxbuilderWill]

Yes. Although rv wings being skinned in aluminum and of a much lower aspect ratio are obviously much more rigid than kitfox wings I'm sure they still flex to some degree and this method of construction seems to be well proven. With the proseal remaining somewhat flexible after curing and the rivets, yes I think this repair will last a good long while and if it becomes necessary in the future the interior of the tank can be accessed by drilling out the rivets and using heat to remove the proseal.

[DesertFox4]

My first Kitfox, a model 3, had one 13 gallon tank in the right wing and a 6 gallon tank in the left. Both fiberglass and neither ever leaked.

[avidflyer]

Kitfox service letter # 10 dealt with replacing aluminum tanks with fiberglass tanks. The first Kitfox 3 I considered buying had been built with aluminum tanks, and they had been replaced with fiberglass ones. One thing to consider is sometimes these planes were built many years after they were bought, and so sometimes the new and improved things show up in older models even though those improvements weren't available when the kit was first bought. My understanding is that all kitfoxes after the Kitfox 3 can use the same tanks, except for maybe the STI wing.