Hmmm...define high altitude [I have a 914 :)].
Seriously, the 1/4" tubing that faces the airstream is very thin wall,
thus more ID than the SS tubing supplied. It immediately enters a
generous water trap which is the same 1/4" ID poly tubing, so only
---From there to the check valve is it the narrower ID nylon (weight
reasons but fixable). The check valve should be effective as last
line of defense.
Europa's method to mitigate water ingestion is the two 1/8" holes,
which I assume is OK, but I worry about me being too sloppy with a wax
rag in that area. Also, as it's metal tubing in the breeze, I figure
it will freeze much more quickly with altitude if enough H2O's
present, whereas my vent tube is "heat-sunk" to the fin, allowing more
time for airstream to purge it.
I'm noting the posts re fuel going upstairs during refueling to the
filler area, meditating on the physics of that -- worse maybe in
monowheel attitude? I see a post suggesting a bigger vent. Me
wonders if just a 3/8" ID run from tank to highest point will mitigate
that, reducing the effects of capillarity. Think I'll try that and
put it on list for thorough testing prior to flight. Thanx guys!
Regards,
Fred F., A063 Tri-gear
Tom & Cathy Friedland wrote:
>
> Hi Fred
>
> Two concerns. One is 1/4" line. A drop of water can freeze and block the
> line.
> Especially at high altitude. The second is that your line must have a
> downhill
> course from the takeoff and cannot fuel or water collect in the down gravity
> loop? Again, freezing or friction sound like a problem. (?)
>
> Fred Fillinger wrote:
>
> > Along the same lines, I have the Mk 1 setup with the fuel fill on the
> > top, but no sight gauge. I ran the vent line (1/4" nylon) up to the
> > area of the fuel filler, where there's a check valve at that high
> > spot, and thence back to the vertical fin via a T-fitting water trap,
> > accessible through the access panel for the trim servo. The actual
> > vent is a chunk of 1/4" ali tubing floxed into a hole in the fwd face
> > of the fin.
> >
> > The check valve is a nylon T-fitting, with the hex fitting on one end
> > plugged with epoxy except for a vent hole, and a little ball bearing
> > and spring from the junk box. Turn the nylon fitting and adjust the
> > unseating pressure. Its purpose is to relieve any vacuum in the tank
> > should the vent line become plugged downstream. The fin location
> > provides pressurized air in flight. The motivation was this aesthetic
> > thing I have concerning an antler poking up from the fuse top. Should
> > work, no? Yes? Elegant even? :))
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