Ken Bryant

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Now that we can use bladder tanks where can we buy them?

AEROSHELDON

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You can get http://www.hobbyexclusiv.de/ to ship to you and also CM Jets will ship them. I think there is another guy that Aeropanda was using as well but I don't know his name.

Bob_B

My Feedback: (11)

Herbert Theil is the guy In Austria and very responsive he is on Facebook. VSpeak sell the Autofiller which works for both fuel bags and Fuel Tanks be sure to order the over flow line.

Bob_B

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1.5 liter tank installed in my Mini Ares

jvaliensi

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How do bladder tanks work? Are they vented? Or do you fill a completely collapsed bladder? Is the fuel under pressure?

rhklenke

My Feedback: (24)

As you can see from Bob's pictures, bag-tanks (aka fuel bags, bladder tanks, etc.) are collapsible, soft bags that can hold fuel. When they are empty, they are completely collapsed with no air in them. As fuel is added, they regain their shape. They don't "expand" per se as the materials that they are made from do not "stretch." This means that the fuel is NOT under pressure. If it were, then the turbine software would have to be modified to account for the higher fuel flow per a given pump voltage because of the pressure, so that is not how the bag tanks work. As the fuel is drawn out of them by the fuel pump, the tank collapses again until it is completely empty of fuel.

Their main benefit is that, since they are fueled with no air in the system, no UAT or header tank is needed and virtually all of the fuel in the tank is usable and can be drawn out in any aircraft orientation - i.e., the fuel pickup is ALWAYS in the fuel." Also, because no UAT is needed, they can be lighter than an equivalent hard tank system.

Their downsides include the fact that they have to be specially mounted so that they can expand to their full shape when full, and so that they do not touch any part of the airframe besides the mounting rods (see Bob's pictures). In addition, they can be more expensive than hard tanks and they need a special fueling system to make sure that all of the air is out of the tank when its full. Also, they generally need to be mounted in front of the turbine to keep them away from heat, and in an area where they can be seen, to verify that there is no air in the tank once it is full.

They are really only appropriate for specific types of jet that can best utilize their advantages - meaning acrobatic/3D jets or multi-engine jets.

Bob Klenke
JPO President

BarracudaHockey

My Feedback: (11)

Also since there's no air in the tank there's very VERY little chance of flaming out because of air getting into the turbine.

And, while not fool proof, they also tend to fare better in crashes than kevlar or glass hard tanks.

Bob_B

My Feedback: (11)

In addition to what Bob Klenke posted the model weighs over 1/2 lb lighter when empty. .5L of fuel weighs 400 grams so my T/O weight is 1.6 lbs less.
As posted a pressure sensing fueler is used. This same fueler fill hard tanks too.
It does require a hand data terminal for programming and read out. I use a Xicoy unit.

Bob_B

My Feedback: (11)

I neglected to say the fuel bag I installed in my Ares is made by a company you can find online.
www.fuelbag.de
The owner Jens developed the fuel bag in cooperation with the Elster jet team. I have seen these pilots fly at Joe Nall. I understand Jen’s will be with them this year.
If you’re considering fuel bag, I highly suggest you visit his website he has a lot of information.

jlorenco

My Feedback: (11)

I also wish to convert my Krill Mini Ares to the fuel bag. I contacted Jens at fuelbag.de and he is on the road and will not be back until June.

My hard tank is from CMJets and they have fuel bags also. Does anyone have any experience with their bags?

Bob_B

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Cm jets tank is 2L which is bigger than you might need. I have experience with Jens tank and it works great! I would be curious to know which dimension cmjets adds the extra .5L What motor do you have in your Ares?
Jens will be at Joe Nall in May.

Bob_B

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jlorenco

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I need a larger tank because I'm running a large turbine with thrust vector (Xicoy X85). The hard tank in it now is a 2L with integrated UAT, so there should be room for a 2L bag. Although, I'm not comfortable using the last 1/4 of the tank doing TV aerobatics with the clunk setup in it now, so I carry around dead fuel weight. With a bag I could likely go smaller and use more of the fuel since I have fuel gage telemetry. Weight is everything with these small jets so trying to reduce every gram I can.

Jens isn't making any new bags until he returns in June. I could wait, but want to explore other options to see if I can get something sooner.

jlorenco

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Deleted

AEROSHELDON

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Herbert Theil if you are on Face---Book makes totally custom sizes. They come with the rods too but are pricey.

These guys also have smaller tanks like 1 and 1.5L https://www.hobbyexclusiv.de/epages/...37/Beuteltanks

jlorenco

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Thank you for the information and link.