K3 Fuel Sight Gauge and Vent Line

[bbryan]

Got to install a fuel level sight tube on side of 13gal. tank. From other pics looks like it doesn't matter if you install sight tube tilted front or back, but if I install high point of tube toward front spar can I tee vent line with top of sight tube or do I need to tap a separate hole for vent line to header tank.

[cap01]

the model IV has another hole and fitting besides the sight guage fittings for the vent . looks like youll probably have to drill and tap one .

[Geowitz]

I have seen some fuel occasionally go back up the vent line which would make it harder to determine fuel quantity if it's pouring into your sight gauge. If it were me I would tap another line. You can build up a 1/2 inch or so cylinder of fiberglass on the outside of the tank to drill and tap so you have more material for the fitting to bite into.

[HighWing]

I don't think there would be a problem with using a T on top - using the same port for the vent and top of the sight gauge. I designed a low fuel indicator system using the vent line and have been watching the vent line for many years.

What I have found: When the air first shows on the top of the sight gauge - Model IV - there is approximately 9 gallons of fuel left in the tank. For the first four gallons of fuel burn, the sight gauge and the fuel vent will be essentially full. After the air begins to show it will be only air in the vent/sight gauge. I doubt the air movement in the vent line - and yes the fuel level does move - would affect the sight gauge as far as accuracy. I redesigned the Low Fuel sensor for this reason as well as to make it Ethanol resistant.
Lowell

[bbryan]

Great Info, I went ahead and built up three areas for the fittings. Highwing, how did you make your low fuel switch. I been working on that too with a prox switch, tubing and a metal float but haven't perfected it yet.

[GWright6970]

When I get closer in my build, this is what I will be installing:
http://www.highwingllc.com/lowfuel.html

Cheers!
Grover