Remove header tank with uniflow setup? - RCCanada - Canada Radio Controlled Hobby Forum
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Old 01-11-2007, 04:52 PM   #1
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Remove header tank with uniflow setup?

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I've recently read on the net (so it must be true!) that a header tank is just added weight if you have the main tank set up as a uniflow system.

I'm using.....
-Dubro sintered bronze filter/clunk in the main tank, and muffler pressure line is on a clunk also.
-OS50 Hyper
-Dynamite Big Daddy filter just before the motor.

Any insight here? I have noticed that a lot of top guys aren't using header tanks, but don't know if they're using pumped motors.


Edit - Forgot to mention that it's a R50-v2. Main tank is lower than the carb.
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Old 01-11-2007, 07:38 PM   #2
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Header Tanks

Hi Dan,

The only helicopter that doesn't require a header tank that I know of is the Vibe/Vigor CS. This is due to it's square tank shape, and the fact that the clunk can reach all corners of the tank. If you use the OMI fuel magnet (a foam clunk) you can get away without a header tank. The foam acts as a sponge and holds fuel while the clunk is exposed to air. With that said, the fuel magnet will only survive a few gallons of fuel when used with an engine that provides muffler pressure to the tank, as the gases break the foam down fairly quick. If you run an engine that provides crank case pressure to the tank then the magnet will last 8-10 cases of fuel, in my experience. Unfortunately the only two engines with this type of fuel delivery system are the YS's and OMI modified OS engines.

A pumped motor will still push air into the carb when it enters through the clunk line. I've recently switched back to header tanks after running a stock OS.91 SZ-H motor (which uses muffler pressure). I ran a YS.91 and an OMI modded OS.91 all of last year and got away with using the fuel magnet.

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Old 01-12-2007, 08:05 PM   #3
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I have a uniflow set-up on mine, and love it. The advantage of the uniflow set-up, is that is provides a constant fuel delivery, and does not generally tend to change as the tank gets lower. The purpose of the header tank is to act as a bubble trap, so that when you go from right side up to inverted, the fuel clunk is momentarily exposed, and sucks in air. This air bubble can work it's way to the carb, and possibly cause a flame-out. The header tank will trap this bubble, and the motor will continue to see an uninterrupted fuel flow. I think the benefits of the header tank far outweigh the weight penalty.
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Old 01-13-2007, 12:53 AM   #4
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Thanks Jester

I fully understand the hows and whys of a header tank, and also the uniflow system. I was just wondering if they're both necessary in my particular setup.

The Dubro sintered bronze filter/clunk works much like the fuel magnet in that it stays saturated with fuel through capilary action, which addresses the bubbles in the fuel line issue. How well it does this is an unknown to me. I really only have Dubro's advertising to go by, and that's not enough for me to remove my header tank.

Maybe I should have asked if anyone is using this filter without a header tank, that's a more accurate way of asking what I was curious about. Either way, the more I think about it the less comfortable I am with ditching the header. I mean, just how much weight are we talking about? Not enough to notice in the air for sure.

With the header I'm fine with running the main tank dry, without the header I wouldn't dream of it. I guess I've answered my own question

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Old 01-13-2007, 04:07 AM   #5
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If the header tank has any air in it after a flight while the main tank still has a reasonable amount of fuel will demonstrate a specific need or risk. Keep in mind that if you are flying easy like say learning to hover and fly circuits then the header tank might not be needed as the clunk follows the fuel properly. When one moves up to an aggressive flybar setup, it's probably time for a header tank. I like the header as it also extends range and gives a good visual reference for those buried fuel tank installations nearing the end of the flight.

Edit - Forgot to mention that it's a R50-v2. Main tank is lower than the carb.
You want a header tank on a raptor, here is why:

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Old 01-28-2007, 06:57 PM   #6
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Hi Stephen,

I see your point about a Raptor tank in vertical attitude, but.....

Unlike a plank, a heli never sees forward or backward thrust. Your pic shows a half tank of fuel in a heli tank that is being held static. In use, the fuel in a heli tank can never sit like that, it'll always be pooled in the top or the bottom of the tank. If it's pooled like that, you've run into something or have just started or stopped pitch cyclic movement. In either case its momentary.

Anyway, decided to keep the header tank. If for no other reason than being able to run the main tank dry with no worries.

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