AUX FUEL TANKS IN WINGS

Hello everyone!

At present I have a pair of standard tanks installed in the wings. I am giving
consideration to adding several smaller tanks( one on each side)
about 3 feet outboard of the standard tanks and connecting them together with air line on top and flow line on the bottom( probably a half inch line). It looks like the 14 inch bay would be space for about 7 gallons a side which would give me about 50 gallons total. The engine is 180 horses. Has anyone done this? It would be fairly simple to do at this point. Maybe there is a better way. Also have room way outboard on these extended wings but it would require lots of line and most likely pumps as well. The wings are uncovered at this point. I'm looking for some opinions so please type away!


MNSC360

Smith and TCOW kits had an option on the twin 10 gallon tanks. They use a transfer pump to the mains. The tanks are in the next bay over from the mains. A look would be helpful to see how to handle the compression cable or struts.

Fortysix12 said:

Smith and TCOW kits had an option on the twin 10 gallon tanks. They use a transfer pump to the mains. The tanks are in the next bay over from the mains. A look would be helpful to see how to handle the compression cable or struts.

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Transfer pumps....

weight and more electro-mechanical stuff to break.

Just put in the Atlee tanks and be done with it.

Tim,

The question was specific to installing auxiliary tanks 3 and 4 and not to be "done with it". By any chance have you weighed atlee tanks and compared that to the combination set forth in the question. I suspect that the weight compromise is superficial. As to the reliability of transfer pumps I do not recall them to be notoriously unreliable. A common practice with belly tanks.

Fortysix12 said:

Tim,

The question was specific to installing auxiliary tanks 3 and 4 and not to be "done with it". By any chance have you weighed atlee tanks and compared that to the combination set forth in the question. I suspect that the weight compromise is superficial. As to the reliability of transfer pumps I do not recall them to be notoriously unreliable. A common practice with belly tanks.

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Jeff-

It all comes down to the KISS methodology.

If the Atlee tanks weigh one more pound for each side I would still go with them. That being said, how much does the second tank, wiring, pump, fuel lines, and breakers weigh? I
m sure I can call up atlee and see what a 31 gallon tank weighs.

I don't see how you can throw two tanks and all of the extra wiring and plumbing on a scale and have it weigh less than an atlee tank.

Tim

There is nothing simple about the installation of Dodge tanks. I like mine, but my wings were disassembled, my old tanks were junk, and available options were very limited. That changes a guy's perspective.

SB

StewartB said:

There is nothing simple about the installation of Dodge tanks. I like mine, but my wings were disassembled, my old tanks were junk, and available options were very limited. That changes a guy's perspective.

SB

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Stewart-

Would you put in two 18 gallon tanks with a pump or one Atlee tank?

If I had a Cub with assembled wings I'd investigate all my options. I think the original poster may be doing just that. As for Atlee's tanks, I stated my thoughts.

SB

I have a set of Flint 13 gallon tanks in my 185. I know it is not a Cub but we are talking about fuel tanks. They are just inboard of the wing tips with a Facet pulse pump for transfer and a quantity gage on the panel. They have been in the plane for 33 years and have been trouble free. The only thing that I notice is that when full, the plane becomes a little less stable. If I were doing this in a Cub I would mount them inboard between the strut attachment and the original tanks for stability purposes. If you are on floats with them at the wing tips on rough water you will find the wing bouncing up and down a lot when full.

First, are you talking about certified or experimental?

Is there a certified option for a smaller tank outboard of the main? I dunno, but someone here probably does.

I've seen a number of Cubs with an additional set of 18 gallon tanks outboard of the mains, but that requires new tank ribs, etc.

There are smaller wing tanks available for the J-3, which should fit between the ribs, but what about the compression fittings, etc inside the wing?

Why not Dakota tanks, which would give you the same 50 gallons, with less muss and fuss? Maybe.....

MTV

I've messed with the Smith Cub aux tank set-up and the so-called "Stoddards" aux tank set up.

Assuming experimental:

The Smith set up is heavy. Don't forget that an extra tank "lid" is used and adds a surprising amount of weight. The transfer pump adds weight. High quality fuel tanks, for sure.

The Stoddards setup adds 13 gallons per side and is pure gravity feed with an additional fuel selector plumbed. It is fabriced-over, so you don't add weight of a lid. The negative...........soldered galvanized sheet metal, i.e., will eventually become leakers like stock PA-12 or -14 soldered/glavanized tanks.

Lately I like the idea of a Firmin/AlaskaBushPOD size cargo/fuel pod, or cargo pod and fuel bladders.

Landes fuel pod is nice.......32 extra gallons you can BOLT ON.

MTV,

I presumed it we were talking Experimental because off the thread index.

Auxillary fuel tanks in wings

Aux tanks in the wings keeps the C.G. pretty much in the envelope. A belly pod tank may appeal to a lot of folks, but it ruins the classic look of the Cub and in my opinion is UGLY !! Ugly !!

I've had a Cub with one 30.5 gallon Dodge tank in the left wing and an 18 gallon stock tank in the right wing (48 gallons).

I've had a Cub with a 30.5 gallon Dodge tank in each wing (61 gallons).

I currently own a Cub with a 24 gallon Dakota Cub tank in each wing (48 gallons).

I've flown Cubs with stock 18 gallon tanks (36 gallons).

My observations......

The best flying Cubs with the easiest to manage fuel system are stock 18 gallon tanks with the stock fuel valves ("left", "right", "off", "off").

You can see all of the fuel on board and none "accidentally" transfers between the tanks. Stock is also the lightest with not a lot of weight up high trying to put you on your nose when landing short / braking hard.

Dakota 24 gallon tanks are real nice if you do a LOT of long distance flying where fuel is hard to come by and $$. They are heavier and harder to tell how much fuel is in them. More weight WAY up high just where you don't want it when landing short.

The Cub with the two 30.5 gallon Dodge tanks felt like a whale when the tanks were full. You could pour 12 gallons into them (three point) before the ball ever moved off the bottom of the gauge. Even in level fight it was hard to tell how much fuel was in them because it was spread out over the large area of the tank bottom. I would not go this route unless the plane was being used for REAL long trips without fuel being available.

At this point in my experience (having done it several ways), if I had a good stock Cub, I would leave the stock fuel tank / system alone. Changing it effects too many other things in a negative way IMHO.

Throw a couple of fives in the belly pod for the occasional long trip and call it a day.

Take care,

Crash

It would be fun to experiment with added fuel weight in a pod versus in the wings. When MCS Mike and I were marking my sight gauges in 5 gallon increments we started by lifting an fuel-empty tail up to find level flight. Once that prop height was established we let it down and added 5 gallons a side, marked the 3-point level, then I lifted it up to mark the level flight fuel mark. Repeat that a few times with 10 gallons more fuel each time and you'll be shocked how heavy the tail gets with the addition of fuel in wing tanks. I wonder how that same fuel load would feel at the tail using a pod.

SB

Crash,
It seams I'v made the correct choice about my decision to stay with stock fuel on my EX project.

If you do install tanks in the wings, do NOT control them with just an on-off valve. If you do, the fuel will only seek the same level as the fuel in the main tank. This means that unless you run that main tank dry you will always have some surplus unusable fuel in the aux tank. There will be times when you do not want this fuel on board. Either use a transfer pump or a valve to directly feed the engine.

fuel

I agree with Crash on wing fuel. The stock tanks/system is best and if you need more go with a cargo pod or a combo pod. The pod's may not be pretty but they come off in 10 min. when you don't need them and they keep the fuel low where is isn't trying to upset you. A pod also works great as a 3rd ski in really deep snow to keep you from getting stuck.

Dave

Thanks for all your inputs!
I will be using the stock tanks and building a belly pod tank at my
convenience. That way I can get-r done, keeping it simple and be light and boost my range later if necessary. This is the greatest website ever.


THANKS
MNSC360

MNSC360 said:

Thanks for all your inputs!
I will be using the stock tanks and building a belly pod tank at my
convenience. That way I can get-r done, keeping it simple and be light and boost my range later if necessary. This is the greatest website ever.


THANKS
MNSC360

Click to expand...

I'm glad you see it that way.

Jcrowles' statement about ugly cracks me up. "..ruining the classic look of the Cub.."

Dodge tanks and a JP Fuel Flow. You can't have enough fuel going up the trench on a weather day! Belly pods make a CUB look useful.

aux fuel

We have 61 gallon Dodge tanks in our 180 PA-12, and used to fly Mexico City to Monterrey non-stop. Otherwise it meant a stop of at least 2 - 3 hours while you argued about getting the fuel, flight plans and other BS like bribing the fueler to actually come - and to have a funnel with a fuel hose designed for a DC-4.

Dodge tanks made it possible to fly 500 miles non-stop in 5 hours rather than making it into a 2 day extravaganza with the risk of strangling someone from frustration. Not to mention hotels, taxis and so on. We are about to install a Landis 32 gallon on our PA-18, and I am darn glad to have it; but if I had my druthers I would always go with Atlee's tanks. No need to transfer fuel, and we have a complicated valve! You have to choose between ON and OFF!

I note that as soon as Landis finishes up the approval on the belly tank for the Husky, I will be in line to buy one.

Crash said:

I've had a Cub with one 30.5 gallon Dodge tank in the left wing and an 18 gallon stock tank in the right wing (48 gallons).

I've had a Cub with a 30.5 gallon Dodge tank in each wing (61 gallons).

I currently own a Cub with a 24 gallon Dakota Cub tank in each wing (48 gallons).

I've flown Cubs with stock 18 gallon tanks (36 gallons).

My observations......

The best flying Cubs with the easiest to manage fuel system are stock 18 gallon tanks with the stock fuel valves ("left", "right", "off", "off").

You can see all of the fuel on board and none "accidentally" transfers between the tanks. Stock is also the lightest with not a lot of weight up high trying to put you on your nose when landing short / braking hard.

Dakota 24 gallon tanks are real nice if you do a LOT of long distance flying where fuel is hard to come by and $$. They are heavier and harder to tell how much fuel is in them. More weight WAY up high just where you don't want it when landing short.

The Cub with the two 30.5 gallon Dodge tanks felt like a whale when the tanks were full. You could pour 12 gallons into them (three point) before the ball ever moved off the bottom of the gauge. Even in level fight it was hard to tell how much fuel was in them because it was spread out over the large area of the tank bottom. I would not go this route unless the plane was being used for REAL long trips without fuel being available.

At this point in my experience (having done it several ways), if I had a good stock Cub, I would leave the stock fuel tank / system alone. Changing it effects too many other things in a negative way IMHO.

Throw a couple of fives in the belly pod for the occasional long trip and call it a day.

Take care,

Crash

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I am turning to the dark side and purchasing a 1958 PA-18A 150. The plane is newly recovered and has stock tanks. Crash has written a great response as I have researched my question; like a good boy; in the data base. For the type of flying I want to do, having more fuel is really important. I would be happy with one Atlee Tank and one stock tank for the additional 1.5 hrs give or take. Is this feasible and what would this do or require for the plumbing/fuel valve? How disruptive would adding a new atlee tank be to a new fabric job? My other question is in reference to Borer Props. I see 80/82/and 84" props listed as Borer props. This particular cub has a borer prop but unknown what length. Is the 2" between an 80 and 82 as significant as say comparing the pitch at 41 to 44?? Many Thanks, eric

belly pods are much easier to install. One hole in fabric, remove left tank and have a fitting installed, replace, hook up and go. Takes a guy a few days, but that is to fuss with getting the pump mounted and tank in and out.

Atlee tanks mean a bunch of cutting of ribs in the wing.

You can remove a pod fairly easily, and go without it. or have a combi pod and enjoy. five hours legs suck worse than sitting in UTAH waiting for Spruce or Univair to send the correct cable.

An Alaska Bush pod with three bushwheel bags of fuel will get you the distance, and a time to relax and breath while you fuel.

WiskeyMike, your mission is different than most. I agree that at times one can not have enough fuel, but most of us fly 3 hours at a time and want a stop.

I have the Smith set-up with transfer pumps on my experimental PA-12. Great to have the extra range, but how often do you need to go 700-miles between fuel stops? The transfer pumps work okay but you are never really sure when you have pumped the outboard tanks completely empty. I would prefer a system where both the inboards and outboards are plumbed to selector switches. That would save the weight and complexity of the pump, would allow all the available fuel to be used from each tank but would not eliminate the weight of the tank cover.

NunavutPA-12 said:

The transfer pumps work okay but you are never really sure when you have pumped the outboard tanks completely empty.

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This problem can be solved by wiring a sensitive ammeter in the aux fuel pump circuit. When the pump stops pumping fuel the electrical load will go down and reflect on the ammeter. OR you can time the transfer on the ground by listening to the pump. It will increase the pulse speed when it runs dry. Then just run the pump for that amount of time. I use 20 minutes in my 185 for 13 gallons.

My 1956 PA-18A has a 150hp narrow deck and a 82-41 Borer prop on it. After a little experimenting this seemed the best for my cub set up. I also agree with George and Crash, stock fuel tanks and fuel system along with a belly pod. When you need to have only 1 hour of fuel in the airplane, it is nice to know that is what you have!

These guys make a transfer pump that turns off automatically:

http://www.onaircraft.com/Products/Auxiliary-Fuel-Tanks.aspx

Don