Alum. header tank question. KF IV

[beeryboats]

I thought of that too John. But as this fabric is already finished I was worried about the possible lack of adhesion between the flange and painted fabric. As I've seen how much the fabric can flex in flight so I'm worried it may pull loose. I was thinking about only clamping the hose to the flange and not the header tank to allow some movement. As far as a leaky sump drain, that's what condition inspections, pre-flights, and a good inflight panel (and fuel level) scan is for. IMO. Unlike a missing fuel cap, a cracked sump o-ring would be a minor leak. To be honest, nothing scares me like the thought of flying behind a two stroke. I know, they've been around and flying for decades, but I can't shake that feeling...

[kitfoxrk]

Maybe this is off topic, but, I could use some enlightenment. It seems like the header tank, particularly the plastic one, is a problem area for a number of reasons. Can anyone provide the history of why the header tank is used, and what the pros and cons would be for keeping it versus just eliminating it. Since the kitfox is a high wing gravity flow system, why is it needed?

[beeryboats]

As a fairly new owner, the first thing I noticed is that there was no low point sump drain in my aircraft. But then again my poly tank was not placed in the correct place. Now that I've installed the aluminum tank in the proper place, it is the low point sump drain for water and general crap that can get in the fuel. Then again mine is a tail dragger and the low point may be very different for a nose wheel aircraft.

[Av8r3400]

Header tank, one major reason.

The fuel pickup in the main tanks is located such that they drain from the rear of the tank to facilitate pluming during the wing fold.

During low angle of attack or decent with lower levels of fuel in the tanks, these pickups can become un-ported, sucking air instead of fuel.

The header tank gives a reserve of fuel in this instance to keep the pilot cooling fan running.

[Paul Z]

Here is where my 7 Super Sport has the header tank behind the passenger.

[PapuaPilot]

There are several reasons that planes have header tank(s). Some of them have been mentioned. Let me list what I understand about them.

1. The header tank is the low point in the plane. It is there to collect water, dirt, sediment, etc. so you can drain it. Note that the fuel outlet to the engine is slightly above the bottom of the header tank to leave some room to collect stuff and still allow clean fuel to go to your engine.

NOTE: You should drain the header tank on preflight, after every flight and after refueling. If you get too much stuff in the bottom then it will go into your engine.

2. It is there to provide some usable fuel in case the fuel tanks become unported. This happens especially when you have low fuel in the main tanks and pitch or yaw (slips or poor coordination). When you do any of these things the fuel in the tank(s) can move away from the pickup hose. The header tank will have enough fuel for the engine to keep running for several minutes if you are unported.

Example: If the header tank holds a half gallon of fuel and your fuel burn is 8 GPH at full power then you have about 3.75 minutes of fuel in the header tank at takeoff power that you can fly unported before the engine quits. If you are at a lower power settings then you have more time.

3. It functions as a place to separate air from the fuel. If you have fuel returning from you engine/fuel pump notice that this line goes into the top of the header tank. This allows the air to separate at the top and go back to the fuel tank(s). The fuel stays in the header tank and goes back to the engine.

Don't remove the header tank! That would be a recipe for disaster. Hopefully this makes it clear that you want, no need, a header tank.

If you have the poly header tank don't even bother using it. Bite the bullet and buy an aluminum one. I just threw my "new" poly tank in the trash recently after buying the aluminum one.

[Paul Z]

I agree with Phil Nelson. This is why I wouldn't use the Poly Tanks
Original Tank that came with the plane. I couldn't get it to stop leaking.
IMG_0761.jpg

Replacement tank after replacing the 1st Tank. I was surprised how much fuel that had leaked. Definitely a safety issue!
IMG_0709.JPG

[nonstop99]

I agree. I was thinking the same thing as John.

I thought of that too John. But as this fabric is already finished I was worried about the possible lack of adhesion between the flange and painted fabric. As I've seen how much the fabric can flex in flight so I'm worried it may pull loose. I was thinking about only clamping the hose to the flange and not the header tank to allow some movement. As far as a leaky sump drain, that's what condition inspections, pre-flights, and a good inflight panel (and fuel level) scan is for. IMO and KF vacuum Flange Unlike a missing fuel cap, a cracked sump o-ring would be a minor leak. To be honest, nothing scares me like the thought of flying behind a two stroke. I know, they've been around and flying for decades, but I can't shake that feeling...

[perssonj]

Hi!
I am converting my front tank to 13 gal wing tanks on my KF IV.
I have decided to build the header tank myself. To save some time I kindly ask if some one could give me the measures of an aluminium tank for the KF IV?
Best regards
Johan

[Av8r_Sed]

Hi Johan,
If you're doing your own tank, you can design whatever you want. I'm in the process of making one that uses most of the space behind the seat. I of course used CAD (Cardboard Assisted Design). Here are a couple of pics of mine and some dimensions.