Ventus bT

We recently purchased this a/c & really enjoy flying it. However there
are two minor problems with the vent line from the removable 18L fuel
tank:
1) We initially put 15L in the tank & over a period of approx 10hrs
flying, we've lost 3 - 4L due to it sloshing about & draining
overboard. The vent line exits in the main wheel box, so we end up
with an oily streak along the underside back to the rudder after each
flight. The PU(?) vent line is approx 5mm ID. I was thinking of
inserting a restrictor in the line close to the tank, with an ID of
approx.2mm, to see whether this reduces the volume lost. Obviously
we'll need to ensure this never becomes blocked.
2) The vent line simply pushes onto a metal tube, exiting the top of
the tank. There is a miniscule leak at this connection, just enough to
cause a petrol odour in the cockpit when you first climb in. I was
thinking of fitting a small hose clamp to see whether it solves the
problem.
Any comments or suggestions welcome. Regards, Bill

You could try a vent tank valve in the line to prevent fuel loss.
The link below might help. Of course you would have the cost of
an EASA minor mod to add.

http://www.newton-equipment.com/tank_vent_valves.html



At 20:12 18 March 2011, BillT wrote:
We recently purchased this a/c & really enjoy flying it.
However there
are two minor problems with the vent line from the removable
18L fuel
tank:
1) We initially put 15L in the tank & over a period of approx
10hrs
flying, we've lost 3 - 4L due to it sloshing about & draining
overboard. The vent line exits in the main wheel box, so we
end up
with an oily streak along the underside back to the rudder after
each
flight. The PU(?) vent line is approx 5mm ID. I was thinking of
inserting a restrictor in the line close to the tank, with an ID of
approx.2mm, to see whether this reduces the volume lost.
Obviously
we'll need to ensure this never becomes blocked.
2) The vent line simply pushes onto a metal tube, exiting the
top of
the tank. There is a miniscule leak at this connection, just
enough to
cause a petrol odour in the cockpit when you first climb in. I
was
thinking of fitting a small hose clamp to see whether it solves
the
problem.
Any comments or suggestions welcome. Regards, Bill

http://www.newton-equipment.com/tank_vent_valves.html

These valves are made for cars and will probably not work well in a
glider since on the road you are hardly going to find yourself going
up quickly (e.g. strong thermal - tank has to vent air to the
outside) AND not draining fuel from the tank towards the engine. While
flying the glider this could result in the valve being closed because
of turbulence (- fuel goes up the line and into the valve) and the
expanding air doing some damage to the system.

I'd try some cheap inline fuel filter mounted vertically so that the
fuel would have to go *up* through the filter to get out. If some fuel
gets to the filter it can retain a few cm^3 and i'd say there is a
good chance of the fuel getting eventually sucked back into the tank
if the filter located high enough. As an additional benefit you'd have
a barrier to insects or dust from the outside but it won't get clogged
more than the vent line itself.

Don't forget to ask for a Form One though...

On newer SH gliders the fuel vent line goes all the way to the top of
the vertical fin. Perhaps you could connect the vent line to an unused
ASI probe in the fin and reap the benefits of a slightly pressurized
fuel tank ! :-)