turbo1889

Just wondering if anyone out there has experimented with building models with "wet wings" that is wings that were filled with fuel tanks just like the real thing. I was thinking using very thin wall aluminum tubing in the wings running the length with diameters to fit the air-foil profile would work and you could just skip the whole spar in the wing and punch holes in the wing ribs and the tubes would do double-duty as structrual but can't figure out how to keep the fuel from all sloshing to the lower wing when banked and resulting in an unrecoverable death roll. Everything I've though of so far that would keep the fuel from sloshing would either extremely complicate tank design or make it very difficult to draw fuel out of the tanks wondering about filling the tubes with sponge chunks like the inside of a ink-jet cartridge. Wonder if there is any spongy material that wouldn't get messed up by fuel and/or wouldn't mess up the fuel though and if you could draw from such a tank without getting bubbles in the fuel line.

Anyone else already done this and worked out the kinks ??? How do they do it on real (non-model) planes ???

beepee

Interesting thought. You might be able to address the sloshing problem with mutiple baffles. The next problem is where to you place your fuel pick up so that it is going to be consistently in it. A long narrow tank of any orientation is going to have both problems: a fight over balance and a clunk that can't bend to the low point.

Hope you can solve the challenges.

Bedford

cslota

If you had both wing tanks feed into a small main tank located in the fuselage, then you could put the fuel clunk in the small main tank. This type of set up should keep the main tank full of fuel.

Let us know how it works!

Calvin

Props4ever

Nice thought, i had thought in recent past to add fuel tanks in the wings and wing tip tanks on my Connie model for long flight duration but again how to control fuel flow from one tank to another and keep the airplane balanced at all times in flight. Well that is why real airplanes have cross feed valves, pressure fuel pumps on board and fight engineer keeps transferring fuel from one side to another side and from one tank to another through out the flight to keep aircraft fully balanced at all times, now days it's all done by computers. It would be very interesting to see what you come up with. I'll be watching this thread for sure.

WALKERS210-RCU

My Feedback: (36)

A thought I had some years back but abandon the idea because of the many factors that would come into play. Rather than using an aluminum tube as a spar it would be possible to use two bays in each wing half and go back to thin sheet copper or tin to fab tanks that would fit into the wing. It would require cross over lines between both tanks feeding to a header tank, unless you intend to build a twin engine plane. As for moving the fuel a PERRY Pump that operates from engine crank case pressure. I don't remember all the points that was given me on why it was not practical I still remember thinking why not. Go for it some of the best ideas have come under constant belittlement and negative input. It will not be easy but this is what is great about the hobby a good challenge is good for the mind.

Rodney

My memory is a little hazy on this (it was back in the early 50"s) I believe Burt Rutanthe renown designer of real aircraftwas attempting a long distance RC flight. I believe he said he made a D leading edge (the space between the spar and leading edge) coated internally with carpenters glue which is fuel proof. He then filled this cavity with fuel and since this was a high wing craft with a fair amount of dihedral, just used gravity feed to keep the small tank near the engine full. That particular attempt('s) for a record failed but not due to fuel problems. I do not know how many of you knew this but Burt was an avid modeler in his younger days.

CrateCruncher

My Feedback: (1)

I've always been attracted to designs that utilize otherwise unused or redundent spaces for storage. Several motorcycle designs over the years have used frame tubes to store oil and fuel. I also recall Colin Chapman (Lotus) making use of monocoque spaces to store fuel. In the latter case the system always used a rubber bladder inside to prevent leaks in the event of a crash. Thinking out loud, I wonder if a bladder system inside a pressurized space might work - probably too complex. The tank trailer manufacturers have some pretty sophisticated baffle designs - you might find some info in their sales literature.

ByLoudDesign

I have come up with this for the wing of the Do-24T, put two 16 oz. tanks behind each engine nacelle. I've been looking at the hardware store for a thinner can or something loke that!

turbo1889

Okay, so I know they use computers and pumps in modern airplanes to control fuel in the tanks but how did they do it on the old birds like pre-WWII. The Spirit of Saint Louis had "wet wings" and shurly didn't have fancy pumps and computers how did they keep the slosh factor down then surely there must me some dirt simple ingenious method used in these early "wet wing" planes that was simple and affective.

Props4ever

You got a valid point, i didn't even thought about those golden day birds!
Yeah these has to be a way to do it and if it was done on real birds then rc models could be worked the same or relative close though!...

Props4ever

Turbo,

I might be able to help you out with this project, we have a DC4 left that is about to get chopped up, still intact as yet. I know the owners very well, i can certainly go out there and see what i can find information from service and maintenance manuals as it's a manual aircraft for most part. Let me know if DC4 will help so i can go there on coming Tuesday. I can take bunch of pictures also if it helps...

TFF

Full size planes have a flapper valves and every couple ribs are solid with this valve so the fuel can not run out to the tip. In car racing, they have foam that is used to prevent fuel slosh and explosion if the tank is ruptured. The two advantages that fuel in the wings have in full scale is one safety, fuel is away from passengers incase of a rupture, and the structure does not have to be as strong at the wing center as the fuel is actually flying instead of being carried. High wing planes like Cessnas and planes that have the fuel tank right behind the engine dont usualy have pumps as the gravity feed is there; even many old aerobatic planes did not have pumps unless modified as they did not spend much time inverted; just following through the roll or loop. Low wing planes are required to have two pumps a primary and backup as gravity does not help out.

BMatthews

Yep, flapper valves or baffles to slow down the movement.

But for our models you'll have a whole other issue. By remoting the fuel supply you would require pumps to move the fuel to a holding tank that is similar to a carbeurator's float bowl that our basic suction carbs can then pull the fuel from. Also a tip to tip tube would be a lot more fuel than we require for our usual needs. Between the need for pumps and developing baffles to contol the sloshing aspect it's just way too much trouble to do something like this for normal model requirements.

Now duration models are a whole other issue. Something like the Atlantic crossing model project led by Maynard Hill a couple of years back likely used complex fuel delivery systems to get the required duration.

turbo1889

Props4ever, unless that DC4 uses some other method beside baffles and flapper valves don't wast any time on my account. Basically with as small as scale as I'm looking at baffles and flappers arn't practical. However, the foam thing might be. The problem with foam is that once it soaks something up it really doesn't want to let it go. I think those green scratchy scrubbing pads that they sell in the cleaning supplies section of the local box store might be the best thing to use. They hold liquid yet when you hold them by one corner they drain themselves dry out the lower corner at a steady drizzle. I'm going to put one of them in a jar full of fuel and just let it sit for a week or more and then check to see if both the pad and the fuel are still good or if they don't get along. Provided they do get along I'm thinking of making myself a circle puncher and start punching out disks and then packing tubes full of them and make a gravity fed system that flows into a conventional tank with a pickup for the engine. Provided the plane stays upright most of the time it should work.

Baldeagle

My Feedback: (7)

Years ago I talked to Kent Walters about his big B17 and the fuel tanks. He used IVbags as tanks in the wing. Just a though. Rich

turbo1889

Excellent suggestion those would make very good bladder tanks. I wonder if they come in multiple sizes or only just one.

Baldeagle

My Feedback: (7)

I just ask my wife and she said they come in different sizes. Rich

maxvertical

I think the scuff pad used in the kitchen would work good for keeping fuel from moving around too much. Can even be a loose metal or the plastic stuff, I tight steel wool wouldn't let the fuel go very quick and would have a higher ratio of filter issues to deal with. The nice part of the scuff pad is it won't absorb the fuel and will "let go" pretty quick. I.V. bag is a good idea but makes routing around wing bays difficult, transitions between bays around ribs would be difficult at best. Ive often thought of making a wet wing using a resin to coat the wing assembly before sheeting the top, having holes forward and aft in the ribs for draining between bays, then coating the top sheeting to seal the sheeting, then once this is done making up a thin resin to slosh in the newly created tank once the top skin was bonded. Might have to put a small aquarium pump on the thing to pump fresh air in until it cures. Just another idea. Love the idea of wet wings and sometimes wonder why you never hear much about scale projects having them.

andrew66

what if u were to cut "lightening holes" in the ribs just big enough for the bag to fit in the ribs. you could sheet the area with balsa to make a "tube" for the bladder to sit in. and wouldnt the fuel tank only have to be about 1/4 the wingspan. having a tank the whole span would be way more fuel than needed, unless like previously mentioned, u were wanting duration

Props4ever

Turbo,

I wondering wouldn't bladder tanks defy the purpose of wet wing tanks we started to discuss here?, i know a friend who can supply you with kavilar bladder tanks if that is what you want to do. I will DC4 owner tomorrow to find out if it has same tanks configuration as you are after.

Props4ever

Hi Turbo,

I called the owner of the DC4 to ask about your question, he said DC4s have 6 wet tanks from tip to tip but all of them have submerged fuel pumps in them to feed fuel to the engine for initial starts. Once engines start vacuum pressure feeds the fuel to the engines. Engines also have there own pumps that feed fuel to the carburetors.. So i guess this is not you are looking for.

turbo1889

Props4ever, if bladder bags work for wing tanks then that will work for my needs. I was thinking of getting the smallest size available and then spacing the ribs nice and wide with wing sheeting and/or stringers to carry the load between the ribs and putting individual bladders in each bay in-between the ribs all hooked up to one common feeder line with little pin-hole flow restrictors on each tank so that a little bit gets drawn from each of the tanks and flow between them is minimized this sounds like sort of what the DC4 does when you say it has six separate tanks arranged from tip to tip. Provided I can figure out what material to use for bladders that won't react with the fuel that should work. Sounds like IV bags have already been used with success.

On a side note it looks like the fuel and the plastic scratchy pad in the jar might not get along the fuel is starting to change color to a light green like some of the green scratchy bad is dissolving into it. To early to tell for sure though could be just some light dye leaching action.

dsquire

I wonder if some of the foam that is used in NASCAR cars fuel tanks would work. It absorbs the fuel and does not allow it to slosh but yet it drains out right to the last drop. Just my 2 cents worth.

Cheers

Don

turbo1889

My worry is that such foam may be a little hard to come by, green scrub pads are sold in every box store, super market, and grocery store.

IV bags might be a little harder to find and get but usually ever town at least has a doctors office or better yet vet shop I'm figuring I can probably get them from a vet easier and they might even have heavy duty tough ones considering we are talking animals that chew on stuff.

WALKERS210-RCU

My Feedback: (36)

A few years back, my wife required IV treatments several times a day. Local pharmacy provided the IV in a container that was a hard plastic container with a rubber bladder, when the solution was pumped in the rubber acted as a pressure system and required a crimp type regulator to slow the flow. At the time the biggest plane I had would not accept them but never know they might be just the ticket. Don't know just what all sized they come in but thought I'd throw it in for discussion.