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Fuel breather pipes
Posted: Sun Apr 08, 2007 6:10 pm
by Bennie Vorster
Does any one know what the impact wil be when the fuel breather pipes is turned to face backwords on a Bush Babies fuel tank caps.
Just seems like on a humid day there might end up some water in the fuel tank.

Posted: Sun Apr 08, 2007 6:22 pm
by Mogas
Bennie
This has been talked about before.
Don't do it. You will create a low pressure in your tank which will evacuate some fuel if tanks are full and worse may get fuel on the fabric and soften the glue etc.
You need a slightly higher pressure in the tank than outside which you will get with the breathers forward.
Don't worry about picking up a little moisture (I have never seen water in my fuel even after flying through light rain) the water trap in your fuel system will collect it if it does occur.
Do you have a header tank fitted with the water drain on the bottom? if not you should get one from Kitplanes and put it in.
Hope this helps.
Mogas
Posted: Sun Apr 08, 2007 8:57 pm
by Bennie Vorster
Posted: Sun Apr 08, 2007 9:06 pm
by Rudix
Yes, it will work fine but don't try polystyrene

The fuel will melt it in a second :D Try cork or something else.
Regards,
Rudi
PS, the Rans has little transparent pipes in the wing root to see the level of fuel in the wing tanks.
Posted: Sun Apr 08, 2007 9:16 pm
by Bennie Vorster
Thank you Rudi good idea, I'll remember that.
Now please enlighten the less technical minded like myself.
I have two fuel tanks in the wings feeding to a header tank and on its turn feed to the fuel filter and then to the fuel pump into the motor.
Why not fitting a fuel filter inline from each wing tank, or will that cause an obstruction in the fuel flow. How will one go about fitting a backup fuel pump and filter?

Posted: Sun Apr 08, 2007 9:28 pm
by Rudix
Bennie Vorster wrote:Thank you Rudi good idea, I'll remember that.
Now please enlighten the less technical minded like myself.
I have two fuel tanks in the wings feeding to a header tank and on its turn feed to the fuel filter and then to the fuel pump into the motor.
Why not fitting a fuel filter inline from each wing tank, or will that cause an obstruction in the fuel flow. How will one go about fitting a backup fuel pump and filter?

A similar setup to the Rans, yes, you can fit filters inline with the wing tanks, should not restrict flow too much. A backup pump could be fitted in the normal way, I have an electric booster/backup pump before and inline with the normal pump, I am not sure if a second filter will be of much use, the first should catch all the junk leaving the second clean.
Posted: Tue Apr 10, 2007 1:44 pm
by Mogas
viewtopic.php?t=3587
Check this link for the fuel system on my bushbaby.
Posted: Tue Apr 10, 2007 3:21 pm
by Morph
Mogas wrote:Don't do it. You will create a low pressure in your tank which will evacuate some fuel if tanks are full and worse may get fuel on the fabric and soften the glue etc.
Bennie, this will be the least of your problems. Facing the intakes back will cause fuel starvation and you will have another engine out in DSR

The combination of the high tanks and forward facing tubes create a very effective gravity feed system that should continue feeding fuel even on a fuel pump failure.
As far as water getting into the tank I doubt it very much. Take a drinking straw and put it in your mouth. Now without sucking on the straw insert the tip into a glass of water. No water will run up the straw because the pressure inside your mouth is the same as that outside and no air is escaping from your mouth. It's only when you start sucking , that the water will enter the straw. Add to that the forward motion of the plane increases the pressure inside the tank to a value higher than the surounding air pressure.
I don't see the value of having a fuel filter per tank. A single one after the header tank would be sufficient The other thing is, if you have two fuel filters between the tanks and the central header tank then they will have to be inside the cockpit. This will lead to smells and potential fuel spillage inside the coskpit when ever you replace them. The only logical place would be just after the taps above the doors on each side but as you know fuel spilt on the windows causes damage

Posted: Tue Apr 10, 2007 9:24 pm
by Bennie Vorster
Posted: Wed Apr 11, 2007 1:03 pm
by Bennie Vorster
Posted: Wed Apr 11, 2007 1:39 pm
by Quentin Ferreira

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QUENTIN FERREIRA