RJ,
When we were building SR#025 we considered using the Murphy vent out the top
of the cabin roof. However, I had a picture in my mind of my plane on its
back with fuel leaking out near my head and this made me uncomfortable. Of
course if I ever do roll over (knock, hard, on wood) fuel will probably leak
out in other places so who knows if this really matters.
Anyhow, we looked in our C185 parts and maintenance books and copied the
Cessna tank vent design in both tanks. I don't remember the cost of the vents
but I do remember they were one of the items that really made me say ouch when
I bought them. I also left on the Murphy vented caps plus I have a cross vent
tube running from the highest point in the left wing, through the cabin, to
the highest point in the right wing. If I ever need to go back to the Murphy
design I can use this tube for that purpose.
I did have a problem with the Cessna vents. When I topped off my tanks the
vents leaked pretty bad until fuel drained down below the level of the vent
tube exit in the end of the tank. To remedy this, while doing my test flying
I stopped filling the tanks to the full 80 gallon capacity, or I filled full
and took off quickly before leaving too big a slick on the tarmac.
For a real fix just last Sunday I drained the plane down to unuseable fuel and
modified the 1/2 inch aluminum vent tubes coming out the end of the tanks so
that instead of coming straight out the tanks and then turning down and out
the bottom of the wings, they now come out of the end of the tanks, turn up to
touch the top of the wing skins and then drop down out of the wings. This
high point in the vent tube should stop the dripping when I have full tanks.
I should know if this works tomorrow when I re-fill my tanks. (The total
drain down was done so I could calibrate my fuel tank dip tube. My electric
float gages read accurate when I'm in level flight but are way off on the
ground (as designed)).
Hope this helps,
Chris Gill, N4965, Anchorage, AK
On 10/16/2001 9:58 PM,
RJ.THOMAS@HALLIBURTON.COM wrote to MURPHY-REBEL:
-> Guys,
->
-> I guess I have succumbed to the "Cessna did it, so it must be right"
-> syndrome; I am thinking about venting the fuel tanks with vents that exit
-> the bottom of the wing near the strut attachment points. I plan to install
-> a vent fitting in the outboard tank rib near the main spar. I think I need
-> a check valve or an anti-siphon loop or something in that vent line to
-> preclude the unwanted loss of fuel on the ramp, but cannot figure out what
-> exactly I would need to do here. Given that I don't have access to a Cessna
-> that I can disassemble, can anybody give me some guidance as to what is
-> acceptable practice?
->
-> Cheers, rj
->
-> R J Thomas
-> Lafayette, LA
-> Super Rebel 3500
-> N140SR
->
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