J

jtrollin

Well Known Member
Has anyone thought about putting a tab in their tanks the way Piper aircraft does? I was thinking of doing this, but did not know if the dihedral of the wing causes all the fuel to flow to the inside of the tank so the tab would not work.

thanks,
 
Yes and no, John.....

....they'll work even with the dihedral. My Air Tractor holds 117 gallons per side:eek: and it has a 3/4 tab in each tank, or around 90 gallons. The fuel is almost to the top at the inboard rib but that's really moot since all you want to know is how much is in the tank and it works well.

Regards,
 
I put them in. About half way up the rib on the outboard tank rib. I'm not flying yet so I don't know but I'm guessing that the tab will indicate somewhere between 2/3 and 3/4 full. I took great care to be sure that tabs in both tanks were at the same height so that they will indiacte. The nice thing about tabs is that they're fixed, whatever they indicate will never change.

Bevan RV7A wiring
 
The fuel capacity is so low

The fuel capacity is so low and the performance so high it is hard to imagine taking off with partially full tanks. However I never used the ones that were in my Archer for 22 years either. I belong to the "only when you're on fire" school for wanting to have less fuel on board.

Bob Axsom
 
I put them in. About half way up the rib on the outboard tank rib. I'm not flying yet so I don't know but I'm guessing that the tab will indicate somewhere between 2/3 and 3/4 full. I took great care to be sure that tabs in both tanks were at the same height so that they will indiacte. The nice thing about tabs is that they're fixed, whatever they indicate will never change.

Bevan RV7A wiring
Click to expand...

you have any pictures of what you did?
 
Why?

The reason Cherokees have that tab is because they can't climb out of ground effect with four people and 50 gallons of fuel on a hot day.

RV's don't have that problem.

When you can cruise at 200 mph on the same fuel burn as a Cherokee you don't need 50 gallons on board. And I've never heard of an RV not being about climb out of ground effect at gross any density altitude. Mine could get better than 1000 fpm at 5000 ft, even loaded to 1950 lbs -- and I only had 160 hp.
 
no pictures

I took pictures of the whole tank build process but since I didn't have any film in the camera I don't actually have any pictures of the complete tank build. I'm sure I'm not the only one who's done this. I've since switched to digital.:)

Bevan
 
Is this what you had in mind?

Here are a photos of what I did:


I just riveted them in place with a longer rivet and Prosealed over the tab. Hope this helps.
 
I did much the same as the above photo. BUT, instead of riveting, I used a screw(platenut on the tab) that holds the tab on. Allows me to make a new tab for any hight to meet a fuel quality calibration.
Great idea I have never used even once.
Thought with my longer tanks I might use it.
NOT.
Accurate highly calibrated fuel flow becomes my key to fuel amounts.
 
With the 7A, when the fuel level gets down to the top of the angle piece on the bottom of the tank below the cap, there is 5 or 6 gallons remaining. Fuel above the angle piece is gravy.

Like Kahuna says, an accurate fuel flow system works quite well. You can run one tank down to nothing and know exactly what remains.
 
Yes performance may not be an issue like a cherokee (or my favorite big brother the warrior) but it makes math eaiser when you pop that cap and look in and know how much you have. In my training days, especially on those hot days, they didnt top the tanks for performance. It was always comforting to me to look in and see the tab and know I had 23 gallons each tank without math or a fancy stick.

Good ideas can be borrowed. Hence the 1955 Chevrolet V8.
 
I made my fancy stick...

...out of a 3/8" dowel that was purchased at the Lowe's Aviation Dept.

Larry
 
I made a tab like Fred Bauer (post #7 link) and it works great. I actually drilled tiny holes (#55 or something like that) in the tab at every gallon (above about 6, which is what is downhill of the dihedral) with two holes for even gallons and one hole for odd gallons. When I remove my cap, the holes are small enough that they hold fuel and it is easy to see/read the fuel level that way. I also used a scriber to put gallon numbers on the Al tab (made of 032, by the way). Never gets lost or misplaced.

greg
 
Greg Arehart said:
I made a tab like Fred Bauer (post #7 link) and it works great. I actually drilled tiny holes (#55 or something like that) in the tab at every gallon (above about 6, which is what is downhill of the dihedral) with two holes for even gallons and one hole for odd gallons. When I remove my cap, the holes are small enough that they hold fuel and it is easy to see/read the fuel level that way. I also used a scriber to put gallon numbers on the Al tab (made of 032, by the way). Never gets lost or misplaced.

greg
Click to expand...

Thanks Greg!

I am about to install the fuel caps on my RV-8 and you have an idea worth stealing.

Thanks again!

:)
 
Bump

I read something in another thread a few days ago about how it would be nice to be able to open the fuel cap and look in and be able to gauge how much fuel is in the tank. So that got me thinking about putting a couple of ProSeal marks on the baffles on either side of the fuel tank.

I went flying with my friend in his Bonanza yesterday and noticed the tabs in his tanks. As I thought through it this morning, I thought I had the original idea of making my own tabs and riveting them to my fuel cap flange, only to find out others have already been there, done that.

I read through all the responses here about the usefulness of such a tool, but since I'm about to rivet the tanks I think one of the two options is worth the effort at this point in my build. However, I have no idea what distance from the filler skin would be useful. I initially thought I'd just put two or three ProSeal dots evenly spaced on the ribs and figure out what fuel quantity that is later, but then I used the brain God gave me and decided to post the question here on VAF.

If anyone can offer any useful measurements of inches from a reference point = fuel quantity (for a tail dragger), that would be really helpful.

Thanks,
Rob
 
Fuel level

I marked the inside of my tanks with a 1/8 x 1in line every inch from the bottoming on the outside tank rib with pro seal. Will calibrate when I fill tanks.

2da8afc39b5985bd5e47800da2d26400.jpg
[/IMG]
William Bennett
CW4 RET USA
RV8A flying
RV7 finishing
 
Last edited:
Kitfoxbill said:
I marked the inside of my tanks with a 1/8 x 1in line every inch from the bottoming on the outside tank rib with pro seal. Will calibrate when I fill tanks.

2da8afc39b5985bd5e47800da2d26400.jpg
[/IMG]
William Bennett
CW4 RET USA
RV8A flying
RV7 finishing
Click to expand...

I was thinking about something similar to this. I'm not sure if I'll be able to see them very well, but it won't take much time or weight to put a few reference lines in there.
 
I ended up marking the inboard rib with ProSeal every inch. It only took about 30 minutes from start to finish.

gallery_11575_1360_326634.jpg
 
Fuel Level

I took a lowes paint stick when the tank was empty and made marks every gal works very well.
Bob
 
Speaking only for the 6A tanks, each gallon had a different space between lines.
I marked my stick at the fuel pump. And it is within 4/10 of a gallon for a total fill up.

I used oak. It is a hard wood and does not wick up quickly. I have a loop that I stick
my finger in to keep from dropping it into the tank. Markings were done with a Sharpie fine line.
 
I also used an oak dowll rod. I marked it in 5gal increments, then used a box cutter to cut each mark completely around the dowll, marked the cut with a Sharpie, and then clear epoxy coated the entire dowll.

At this point I had a very shiny dip stick that was difficult to determine the level of the wet fuel due to the high gloss on the stick. The last step was to use some fine sandpaper to eliminate the gloss, and the results are a very useful dip stick.

I made a holder for this stick and for the fuel sample cup on the back side of the pilots seat. Very convent to use and store.
 
what's an inch worth?

I too am interested in this idea ? I think it is a great ?second opinion? on such an important bit of information (how much fuel do I really have?). With regard to the question of, ?how much fuel is an inch for an RV7/8 tank? (the -7 and -8 tanks are the same, right)? If I interpret the link in post #19 correctly, Kevin Faris used a trimmed down carpenter?s square and it doesn?t look as if he took any length off of the bottom of the square, so an inch from the bottom of his tank, was worth very close to 6 gallons. (Using his calibration table at the bottom of the website ? partially reproduced below) It looks like for every additional inch, you add 3 more gallons ? all the way to the ?below the ring? - I assume that means just up to the ring flange. So, wouldn?t an inch be worth an inch in an RV-7 / RV-8 tank regardless of if you marked it on the rib in ProSeal, or made a carpenter square, or dipstick? I would love to know if Gasman and Noelf are seeing the same ?per inch? readings as Kevin shows, BUT both Gasman and Noelf have -6 tanks, and I don?t know how similar, the -6 tank is to the -7/-8, so I guess it doesn?t matter ? based on Kevin?s calculations, every inch after the first one is worth 3 gallons??

(From Kevin Faris - partially reproduced)
Tank dipsticks in ground attitude:
STICK LEFT RIGHT
1" 6 gals. 6 gals.
2" 9 gals. 9.5 gals. (slight variance here)
3" 12 gals. 12 gals.
4" 15 gals. 15 gals.
5" 18 gals. 18 gals.
Below ring 21 gals. 21 gals.

Thanks to Kevin for doing the calculations and Bob Collins for bringing it to my attention :D
 
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