Alum. header tank question. KF IV

[beeryboats]

My new header tank is here! Ok, now what the heck is this part for?

My replacement aluminum header tank has a couple extra holes that my poly tank did not have. I've figured out all that, but two parts have me puzzled. What is the 3" piece of 1-1/4" radiator hose and flange adapter for? My first guess is for the new sump drain, but my tank is nowhere near the bottom fabric where the 3" hose would reach. And I guess the alum flange would glue to the fabric?

[Dick B in KY]

If your tank is not close enough to the fabric to use the 3" hose, you don't have the tank installed correctly. It should very low down behind the right side seat.

Dick B

[beeryboats]

Thanks Dick,
I'm not the original builder and I'm converting from the poly tank to the aluminum. The poly tank was mounted fairly high in my KF, about a foot above the belly skin. I feel a little bit limited by the aluminum outlet line coming out of the tank as to where I can place the new tank.
Jay

[Paul Z]

Attached are some photos of the aluminum header tank I have. I had 2 of the plastic POS header tanks both leaked badly.
Here is a photo of the top of the aluminum tank. The two top hoses left & right go to the wing tanks. The center hose and clear tubing goes to the fuel warning switch in the round canister above.
I will need to do 4 post to get the 4 pictures that may help you.

[Paul Z]

Here is the front of the header tank. See the tubing line, just under the hose, it feeds up to the fuel filter to the engine. Also look in the next posting to see the tubing, and hose routing. The hose feeds to the right top of the tank and is a fuel return line.

[Paul Z]

This is a picture of the POS plastic header tank but it shows where the return fuel line goes into the tank. Just below the return line there is a drain fitting, just pluged. In the bottom of the header tank there is one drain, that a fuel check valve is installed. I hope this helps, I know you have a IV, and mine is a seven, but I would imagine the design concept is similar.

[Paul Z]

Here is my other plastic tank, as you can see both had leaks! :(

[Paul Z]

If you need more photos please feel free to ask.

[Eric]

Hello
I have also a plastic headertank and it looks good.
Where are they leaking ,at te fittings or is the plastic not fuelproof and will it sweat?
Eric

[Paul Z]

Both of mine leaked at the fittings. They would not tighten up and the sealant didn't seal adequately. See above two pictures to see where they leaked, The Header tank that is leaking from the top ( the picture posted Yesterday, 10:57 PM) is the one that was in my plane when I purchased it. I went to go flying with my wife the first time, and we opened the door, and the plane reeked of Gas Fumes. I replaced it with the second tank, (the picture posted at Yesterday, 10:59 PM) which leaked from the side fitting. I finally replaced it with the aluminum tank. Since then my wife has never been willing to go flying in the plane!

[beeryboats]

Thanks for all the photos Paul. My IV is plumbed WAY different than your aircraft. A retrofit of that magnitude is out of the question. I saw no signs of leaks but the outlet was plugged solid. My IV has been setting for 10 years! So I opted for the aluminum tank upgrade based on stories like yours. Little did I know that it was designed for the four stroke engine and mounted lower in the airframe. I think I can make it work mounted where the old poly tank was hanging. I'm still toying around with the idea of installing the sump drain in the tank even though access would be tough. It might be useful in the future.

I'm still thinking about how to put a real low point drain where it should be. Right next to the pilot's seat. Not the easiest place, but it is the low point configured as a tail dragger.
Jay

[Wheels]

Here is a pic of my mod IV aluminum header tank install. the drain is way easy. I use the tank at the low point to drain fuel if doing a wing fold or major work like I am today on the engine mount replacement. John Mcbean was the lead agent on info here and I do what he says. The tank is flawless and the routing simple. It's a plane not a toy so the plastic fuel tank had to go.

[DanB]

Jay,
If the production header tank does not have fittings where you need them or is not the right size, contact me and I will work with you to make one to your specs. I'm a welding instructor at a high school and I specialize in TIG welding aluminum parts as a side gig. I'm sure I can come in quite close to the price of the stock units.
Dan

[beeryboats]

Jay,
If the production header tank does not have fittings where you need them or is not the right size, contact me and I will work with you to make one to your specs. I'm a welding instructor at a high school and I specialize in TIG welding aluminum parts as a side gig. I'm sure I can come in quite close to the price of the stock units.
Dan

Thanks for the offer Dan, but I think it's going to work out ok.

[beeryboats]

Thanks Wheels! Wow, does a photo say a thousand words! The tank is in a totally different place on your a/c. Mine is mounted behind the rear baggage compartment of all places. I'm handicapped by not having the original build info. I have no idea of what he's done is correct per the plans or not. But where your tank is located, and the shape of the tank make sense. Obviously the seat fits in front of the tank. Has everyone else placed their tank in the same place? I guess it wouldn't be that tough a job to bend a new fuel line from the outlet to the fuel valve.

[PapuaPilot]

Jay,

That is where I put the header tank on my model 5. It shouldn't be hard to put in some new fuel lines. You want to put the tank as far down as possible so that you can use the aluminum flange and hose to seal the drain to the fabric. You will obviously need to make a hole in your fabric at the new location too. Like others have mentioned, this will become your low point in the fuel system which is a great plan.

Mine plane came with a plastic header tank and I decided to replace it during the build.

[Wheels]

Hey Beeryboats,
Wheels here, My first name is Jay too so I think I'll stick to the handle to avoid confusion. That aluminum header tank works great and I really like the location in my plane. (right behind the passenger seat.) I did have to shave a little fiberglass from a high point on the seat pan to keep it from chafing on the tank. I don't have any contact with the seat and tank now. My normal passenger weights less than 110 lbs but if I put a hog over there it could distort the seat enough to make contact with the header tank. My original build manual shows the tank mounted here. The CD is available and I got mine from John Mcbean. Do you have that yet? You can read up on various processes and save a lot of headache. I'm not the builder and I don't have that much experience with A/C building so I needed the build manual and CD which I have.
When you take out your interior during inspection, the tank and connections for lights and ELT are all very accessible. the tank is robust so even if there is a hog in the right seat, I am not worried about cracking a line fitting or anything. Hope that helps.
Jay White
Kitfox IV classic
912 Rotax

[Paul Z]

You might consider posting some photos of what you have so we can better discuss your problem.

[beeryboats]

Sorry Paul, I've removed it all. It was hanging off the top rear of the baggage compartment, facing rearwards. And it was reversed front to back. So if you took your tank from behind the passenger seat, then leaned wayyy back behind the baggage compartment, flipped it front to back, and installed it, that's what I had. I'm beginning to wonder if he did it for weight and balance. No worries. If everyone is in agreement that it belongs behind the passenger seat, that's where its new home is going to be! It sure makes it easier to get to.
Jay

[beeryboats]

Great strides were made in aviation today. I mounted the new header tank today and installed all the fittings in both the wing tanks and header tank. I marked the fabric for the flange fitting and removed the tank again. I need to mount the flange now. The old fuel line was cut out of the wire bundle on the pilot side and disposed of. It was plugged solid like the fitting in the header tank was. The new fuel valve and rebuilt gascolator were installed. Now I wait for more parts to arrive....

[beeryboats]

Parts and supplies are arriving daily. I have a question on gluing the aluminum flange to the belly fabric. I assume you glue the flange to the fabric from the inside and glue a patch around it with at least a 1" overlap? Or would you cut a hole for the neck of the flange and glue from the underside? Gluing on the inside makes more sense to me.

[PapuaPilot]

The flange goes on the inside with a fabric patch like you said. I haven't done mine yet, but gluing it to the inside makes sense.

For my drain I fabricated an aluminum piece that will go on the outside of the plane. It is like a large washer and I will screw or rivet it to the flange through the fabric. Part of my thinking was that I don't want any fuel smell getting back into the cockpit after draining the header tank. It would also keep the fabric from rubbing on the flange if the glue doesn't hold. I will cut the hole in the fabric and install it after painting.

Another thing I did was drill a 1/4" hole through the flange and washer where the drain line from my fuel pump will pass through.

[beeryboats]

Thanks Phil. You're talking about a reinforcing ring on the outside?

[PapuaPilot]

Correct, I will be reinforcing the flange with a ring outside.

[Wheels]

that's not the way I did it. This was done with John Mcbean watching ever so closely. there is sealant under the flange also. Remember, when you sump the drain, you are putting upward pressure on the flange. I think you can do it the way your talking about as well, but there you are, ... experimental.

[rosslr]

I have just attached this on our K7 build and the instructions are very clear about gluing it to the inside with Poly Tac and then covering with a doily on the outside. it also says to cut a cross slit to open it up and glue the 'ears back inside the flange. It takes a little careful trimming to get the supporting radiator hose the right shape to fit neatly with the tank and the flange.

cheers

Ross
Mt Beauty
Vic

[beeryboats]

Thanks guys.

[jtpitkin06]

I used the "what if" approach. What if the drain valve does not seal and starts to drip? Do I want the fuel to wick down the tube and possibly work its way inside the aft fuselage; or, is it better to dribble down the tube and vent fuel to the outside?

With that in mind I put the tube in from the outside of the fabric.

John P

[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.
8085

Replacement tank after replacing the 1st Tank. I was surprised how much fuel that had leaked. Definitely a safety issue!
8084

[kitfoxrk]

Thanks to all for the great comments. I am enlightened. It is greatly appreciated.

[PapuaPilot]

Paul Z,

Wow, your pictures really drive the point home of why you shouldn't use the poly tank!

What did you use to attempt to seal the threads on the poly tanks? What did you use on the aluminum tank?

[Dave S]

Phil,

I think Kitfox uses Permatex 80938 in their kits (formerly Permatex 9AR) It is a white sealant that is fuel proof and does not harden.

Same stuff recommended for poly and aluminum tanks and wing tanks & any other screw in fuel fitting....... now the poly tanks?....what can I say......:mad: .....

Used it to seal all fuel fittings....6 years....no leaks.


Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

St Paul, MN

[Paul Z]

I used the Permatex 80938 that comes in their kits. I believe the treads are tapped to deep. I removed, reinstalled just to watch it happen again. The treads are so weak you have to worry about stripping the threads out. For me it's the aluminum tank or a funeral, pick one. If you look at the Poly tank that leaked on the sides, you can see the treads are not stripped. I wouldnt waist the time or risk my life putting in one of those crappy plastic ploy tanks.

[jiott]

Here's my 2 cent opinion on why the threads leak on the poly tanks even when sealed with the 9AR which is really good stuff. I think it is because the poly threads are so soft that they conform perfectly to the fitting threads and thereby essentially wipe off most of the 9AR sealant as you are screwing in the fitting, along with the fact that the threads are tapped deep and you can't tighten the fitting very much. The same 9AR sealent works very well when the mating part is aluminum (header tank) or fiberglass (wing tanks) because those are harder materials. Just a thought.

[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 (http://www.accuvac.com/product-category/kf-flanges/) 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.

[perssonj]

Hi Paul!
That sure looks like a big one. Thank you for sharing.
Are you going with 6061-T6? What thickness do you use?
/Johan

[Av8r_Sed]

1/16" 3003 I believe. It's what I had on hand. I incorporated a low fuel sensor and a low point belly drain. Outlet of header feeds into an existing backup Facet electric pump.