Roger,
The fuel vent on the belly makes sense for a few reasons. Not only does it
look better but when the tank is full and the vent spits some fuel it
dosen't run down the side of the fuselage. Also in a crash if the fuselage
ends up upside down - you won't have a fuel tank drain right next to your
ear.
The problem is coming up with a suitable air brake for the line. Some have
installed a bottle in the top of the fuselage and run the vents into it but
Cliff had a great idea when we were building. We used the fuel fill pipe as
the air brake - heres how.
The vent line and sight guage line were teed together (my sight guage runs
up the back - baggage compartment - side of the fuel tank) and that was run
up to a fitting drilled through the side of the fuel fill pipe near the top.
I used one of the fittings that was supplied with the aux fuel tank.
Another fitting was also added to the fuel pipe and the vent line was run
---From that down to the bottom of the fuselage - near the fuel drain. It is
well off to the side so the tire won't throw up debris into the vent.
So far this has worked great. If you fill the tank so full that it comes up
the pipe - when it gets to the level of the fitting the fuel then just runs
out the vent in the belly and just drains onto the ground. There is quite a
bit of area in the top of the fill pipe for the air brake. The fuel sight
guage on the back of the tank bulkhead is easy to see while filling so I
know exactly when the tank is full. I have an electric guage and a fuel
totalizer to monitor my fuel levels while in flight.
You might be able to see some of this on my website pictures - but I plan on
adding better pictures of this system to my "mods" page soon.
Bob Jacobsen
A131
From: "Roger Sheridan" <rogersheridan@btinternet.com>
>Subject: Fuel Tank Vents
>Date: Sat, 11 Nov 2000 21:05:54 -0000
>
>Dear All,
>
>Am keen to elicit any opinions on siting the fuel tank vent underneath
>rather than on top as per the manual. Has anybody done this successfully
>and/or obtained PFA approval?
>
>Sight gauge syphoning needs to be avoided, why not link the sight gauge
>vent
>and tank vent? I think that should prevent syphoning. (My seat back sight
>gauge doesn't go up to the roof)
>
>Rain entering the tank should be avoided.
>
>Vent underneath would be more prone to blockage by dirt/mud but the extra
>drilled hole should prevent total blockage.
>
>Any opinions gratefully received!
>
>Cheers,
>
>Rog Sheridan.
>
|