Fuel tank controversy

[FoxBob]

I am building a Sky Star Series 5 Vixen. I have read enough on Team Kitfox about problems with trying to coat early fuel tanks that I won't go that route. I can buy new alcohol-proof ones for (only!) about $1200 and wait 8 months for them, or I can use the ones I have and never use fuel containing alcohol. I have first-hand experience with TCP (tri-cresyl phosphate, found in Decalin Run-up) and it does do an excellent job of keeping lead deposits out of the cylinders of a VW-based aero engine in a friend's Cygnet, and it appears to be compatible with the early fiberglass tanks. What I have never seen on Team Kitfox is whether anyone has made aluminum tanks for the Series 5-7. Seems doable within the $1200 price range, or am I being naive? It would certainly solve any fuel compatibility problems.

[109JB]

Too much flex in kitfox wings for the way they are mounted. Aluminum tanks cracked and then leaked. Early avids and kitfoxes had aluminum and then went to fiberglass.

https://kitfoxaircraft.com/images/se...tins/SB-10.pdf

[Monocock]

As ethanol inclusion percentages gradually increase here in the UK, I decided a few months ago to religiously only use UL91 Avgas. Yes, it costs a bit more, and it means buying 193 litre barrels, but at least I can relax knowing I won’t go to the hangar one day and find I’ve got empty tanks, and a pool of fuel on the floor.

[Shadowrider]

Interesting that AL tanks had issues. Highlander uses aluminum tanks and they are very similar aircraft. Wonder what the difference is?

[109JB]

Not sure how the original aluminum fuel tanks for the kitfox were installed, but maybe glued to the spars like the composite ones. The highlander doesn't use that method. In this video, you can see how the highlander tanks are installed.

https://youtu.be/RCec4VFpuuw

[patrick.hvac]

There is lots of discussion on this in previous posts and in some FB group stuff.
The difference is the drag tube. Highlanders have a drag tube running under the fuel tank to deal with the flex.
On FB in 2020 Brandon mentions the additional weight, complication, and capacity loss of installing drag tubes to allow the change to justify the decision of this change not being worth it.
It can be done and there are a few KF with aluminum tanks however this is not an easy or approved change.
Also to note - The highlander tanks are not a drop in fit for the KF SS wing profile.

[Shadowrider]

One regret I have is I wish I had more fuel. Flying in the back country I wish I had 10 more gallons.

[patrick.hvac]

Lots of options for that though. Put a belly pod on it and pump it up or split the difference with a 5Gal header tank.
What's your endurance currently?

[Shadowrider]

The dilemma is I want more fuel capability but don’t want the added weight. So, I use two VP cans and pack 10 extra gallons. This is very few times though so 95 percent of the time I don’t need more fuel. I have contemplated putting a marine tank in the cargo, with a fuel pump and connect it to the fuel vent line and pump it up once the fuel has burned down. That way I can remove it when I am not using it. I don’t really want more endurance I just want more fuel for back country operations. Fuel bags are probably the best option. Don’t add weight and they are compact once you use the fuel. Building again I would consider bigger fuel tanks in the wings though.