Fuel Gage (or lack thereof)

[cainbird]

I have a Model 4 with 13 gal and 6 gal wing tanks. I have a very difficult time judging my fuel level. One tank has a piece of clear fuel line coming out of the bottom of the tank and looping up to the top where it reinters the tank. This is inside the wing root. The other tank has nothing. The tanks are not painted so if you look real hard, and the lighting is just perfect, and you roll the plane back and forth, you might see the fuel level through the fiberglass. Often times I think I am getting low on fuel and top off only to find I still had 10 gallons of fuel left. I am looking for ideas for a decent fuel sight guage. Does anyone have any good ideas or photos?

Thanks~Cain B

[SkySteve]

Most of us have some kind of clear tubing in the wing root that goes from the top of the tank to the bottom of the tank along the edge toward the cabin so you can see the fuel level. Others have a fuel gauge in the same place that has a backing with gallons marked on it. Kitfox Aircraft sells this one and it appears to be really nice. Many of us have also added an in-panel Fuel Flow Meter that you can set when you fill up. It will show you your current fuel usage during flight, how much fuel you have remaining and give you an audible low fuel warning. I use mine all the time and it has ended my worries about fuel exhaustion.

[Av8r_Sed]

I've got the tube in the wing root with a vinyl fuel gauge placard background I more or less copied from the factory's design and had made at a local sign shop. With the colored stripes behind the clear tube, the fuel filled portion refracts the light and the stripes appear vertical. The empty portion of the tube just shows horizontal stripes. It seems to be simple and effective.

-- Paul S

[DesertFox4]

Just a thought on fuel flow instruments. They calculate your current fuel flow and give you calculated fuel remaining. They are not a substitute for frequent checking of your fuel tank site gauges. Several cases have been reported where a fuel cap had been accidentally left off during refueling or put on backwards by a line person and large quantities of fuel had been over-boarded in a very short time. Your fuel flow meter will not give you any warning in this situation. Your tank site gauges are the only reliable indicator of fuel on board. I love my GRT fuel flow set up but only as supplemental information, not primary.

[HighWing]

A note on Paul S's post. The diagonal stripes do work. On my first model IV, I did a detailed fuel calibration on the site gauge adding fuel sequentially and marking the placard. what I found (and this is from memory). At the first air at the tip of the gauge, I had nine gallons in both three point and level flight. From there three point and level flight differed especially at the lower quantities - probably in the neighborhood of two to three gallons. I have seen placards stating full at the top of the site gauge, but the actual 9 gallons was far from that. Paul's gauge showing 3/4 at the top is pretty close. As I recall (and this is more sketchy) on the ground if you could see fuel at the bottom of the site gauge, you had three gallons. I have to decide if I want to do the calibration again - lot of work. So far this time, all I have done is use a Brother label maker and put series of slash marks on a half inch label and tie it behind the site tubes - no quantity marks. Fox 4s note is wise advice. In the latest Sport Aviation there is an article on a fatality using calculated fuel vs. gauged fuel. It was in a Lancair IV which I have experience with that prompted the read. Totally different fuel tank geometry, but I have personal experience with the fuel cap issue - facing forward, but only one tang secured - line boy and unchecked by me. It sucked out nearly the whole tank on our leg from the Desert Fox fly-in to a scheduled fuel stop in Ely, Nevada - about a two hour flight. I watched the whole thing on the gauge and flying companions verified the fuel loss overboard.
Lowell

[SkySteve]

Good points about looking at your fuel. There's always something good about logic and checking things yourself.

[dholly]

When I changed my old fuel tank sight tubes I ran them outside of the root rib and added a wire inside, both of which helped a lot. Then I painted some scrap aluminum sheet in black for a root rib cover and ran some white electrical tape behind the sight tubes. Even better, particularly through my covered butt rib windows. I haven't marked graduations yet because I am changing out the tail spring, but Paul's template couldn't have come at a better time. Thanks!

[cainbird]

Thanks Guys. This is the info I was looking for. Dholly, I like the way you added contrast with the different background. It also cleaned up the wing root nicely. Av8r_sed, I like the decal indicating how much fuel is available in flight and on the ground. My right (13gal) tank already has the fuel sight tube (or loop) installed. My left (6gal) tank has nothing. So I guess now I need to figure out how to install a nipple at the top and bottom of the tank for a fuel sight on my left tank. I can then incorporate some of the great ideas you guys have used.
I also thought about installing an inline fuel shut off on my 6 gallon tank. I could then run my 13 gallon tank dry and then switch over to the 6 gallon tank knowing I have 6 gallons remaining. I wonder however if this would cause a problem with only the 13 gallon tank being vented back to the header tank. Any thoughts?

Thanks~Cain B

[Av8r_Sed]

Cain,
On my fiberglass tanks I used the rubber grommets from JBM Industries and got the push in right angle fittings from a local power equipment shop. I used the blue Bing fuel line with a brass wire inside to help it hold shape. I'm not sure if the same arrangement would work for your 6 gal tank.

Here's a link for the grommets: http://jbmindustries.com/ROTAX.htm

-- Paul S

[Av8r_Sed]

Cain,

Here's a detail photo of my sight gauge.

-- Paul S

[Dorsal]

Nice workmanship!

[dholly]

That pic really shows the refraction phenomena well. That really makes capturing the level with a quick glance much easier. Definitely need to do that now. :)

[GWright6970]

It is threads like this that makes this site soooo valuable.... THANK YOU EVERYONE! This will help me a lot!

[Peteohms]

When I changed my old fuel tank sight tubes I ran them outside of the root rib and added a wire inside, both of which helped a lot. Then I painted some scrap aluminum sheet in black for a root rib cover and ran some white electrical tape behind the sight tubes. Even better, particularly through my covered butt rib windows. I haven't marked graduations yet because I am changing out the tail spring, but Paul's template couldn't have come at a better time. Thanks!

Dholly,

What did you use for the tubing?

[dholly]

Tygon 2375 Ultra (http://www.processsystems.saint-gobain.com/uploadedFiles/SGPPL-PS/Documents/Flexible_Tubing/FT-Tygon-2375Ultra.pdf) by Saint-Gobain. So far no yellowing with E-Free premium auto gas.

[cap01]

Also tygothane c-210-a works well