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Roger1950 Roger1950's icon
 2008-01-31 22:20:46
I see from videos and photographs some helis use header tanks what is the reason for this, is it any advantage in any way.
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Alvin Alvin's icon
 2008-01-31 23:23:55
several reasons really,one is to prevent an engine cut due to the clunk coming out of the fuel when the main tank is low during 3d,and another would be to allow the pilot to run the main tank empty,allowing a full flight.some 90 engines are very gutsy on fuel,7 min flights are all some folk get at high head speeds.
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Sbrown5925 Sbrown5925's icon
 2008-02-01 07:19:10
Hi.
As Alvin mentioned, I use a header because I do aerobatics and when the heli is being thrown around, the clunk in the tank can come out of the fuel. Thus sucks up air and whoops, engine coughs.
I have only found one heli that I could chuck around with no header and that was the Robbe Moskitos. Something about that tank design sorted it.
I have tried other helis with no header and always had engine cuts when doing aerobatics.
Some helis have their tanks in the canopy. These are getting slightly fewer as new helis come out, but still, if the main tank is in the canopy and you can't see it, a header on the back can give you a safer situation. In that you watch for the header to slightly go down and then stop because you can always see it clearly.

There is something called a "fuel magnet" which is a different style of clunk in the main tank that is covered in a foam. This is to eliminate the need for a header as it soaks up loads of fuel and can bridge that gap when the clunk is temp out of the fuel.
I have never used one and many no doubt do. Only one guy in our club has used one and he had bad results, in that it broke apart in the tank, sticking small bits of foam into the carb, causing all sorts of problems. And this was only after a couple of weeks use. He reverted to the header tank and has never looked back.

I have had one other use for a header. I have found that in some helis like my old Robbe Millenniums, that when I come out of a loop and the nose of the heli is down, the engine flooded rich. The full main tank is behind the engine so at this point the fuel is above the engine. Also I found that inverted the engine would run at a slightly different mixture due to the vertical position of the main tank in relation to the engine.
So if I placed the header tank in front of the engine and slightly above the carb line, I could remove these tendancies totally.

This theory was also proved in a more extreme situation. That being Russ Deakin when he flew his 3dnt and rdnt. (russ's modified / improved design)
With this heli the engine is right at the nose and when he did fast pirouetting flips and loops, the fuel would be slung out to the engine, flooding it rich big time. He placed the header right at the formost front position inside the canopy. Instant cure.
So much so that he was enjoying the result so much that he ran out of fuel and broke the heli. He was so used to it changing through out the tank aswell, that he missed these tell tale signs and whoops.

Alot of helis don't show tendancies that require the header to be used to compensate for main tank position and many will continue to dissagree with this theory. But I know it makes a big difference and all those out there who might have their heli going a bit richer inverted or when nose down, try moving your header. You will be surprised how you can fine tune it for a better result.

Si smilie