Tank quantity sender

Hi,

A few years ago I had my tanks built by Evans Aviation.

I am a slow builder (6+ years into the project) and I am now almost ready to mate the wings, including the tanks.
I inspected the tanks recently and realized that there are no fuel level senders installed despite my request.
My fault, I didn't check before, too late now...

Both tanks are built with flop tubes fuel pickups.

What do I need to order from Vans now to install fuel level units?
I guess the only choice is a float type sender?
I have red somewhere that these can interfere with the flop tubes? Is that correct? If yes what is the solution?

Thanks,

Alain.

Alain,

When I built me tanks I installed both the capacitive and float senders with flop tubes in both tanks. Based on a recommendation from another local repeat builder I put the float sender in the back the next bay out. Vans pattern for the wire bend was pretty close for this location as well, just required about 5 minutes adjustment to allow the float full range.

Hope this helps.

Alan

Capacative

If you want capacative senders, Princeton makes a few.

answer to a question not asked...

Alain,

You didn't ask about this, but...

Are you planning on having an inverted oil system in the plane? Because if you're not, you could re-consider using the flop tubes. They are only useful if you do sustained inverted flight (not something most RV drivers do). The flop tube installation is significantly more complicated, with extra failure modes, such as additional joints and the potential for the tubes to hang up. And they drive other changes, such as moving the level senders to the next bay.

If you do typical 'gentleman's acro', meaning loops, rolls, cuban 8's, etc that have no sustained negative G's, then the flop tube does nothing for you. I say this as an RV owner/frequent acro flyer for over 20 years, who removed the flop tube from my current RV-4.

FWIW,

Charlie

wirejock said:

If you want capacative senders, Princeton makes a few.

Click to expand...

If the tanks are already closed, it's going to be mighty difficult to put in capacitive senders now. I would stick with the floats for ease of installation.

Alan Bumbaugh said:

Alain,

When I built me tanks I installed both the capacitive and float senders with flop tubes in both tanks. Based on a recommendation from another local repeat builder I put the float sender in the back the next bay out. Vans pattern for the wire bend was pretty close for this location as well, just required about 5 minutes adjustment to allow the float full range.

Hope this helps.

Alan

Click to expand...

I looked at this and it seems the only option with fop tubes. Thanks.

Are you planning on having an inverted oil system in the plane? Because if you're not, you could re-consider using the flop tubes. They are only useful if you do sustained inverted flight (not something most RV drivers do). The flop tube installation is significantly more complicated, with extra failure modes, such as additional joints and the potential for the tubes to hang up. And they drive other changes, such as moving the level senders to the next bay.

If you do typical 'gentleman's acro', meaning loops, rolls, cuban 8's, etc that have no sustained negative G's, then the flop tube does nothing for you. I say this as an RV owner/frequent acro flyer for over 20 years, who removed the flop tube from my current RV-4.

Click to expand...

I went with 2 flop tubes when I ordered the wings.
If I had to do it again I wouldn't have flop tubes...
I'll see how hard it is to modify and go normal pickup tubes.
If not too complicated I'll do the mod.
Thanks.

If you want capacative senders, Princeton makes a few

Click to expand...

If the tanks are already closed, it's going to be mighty difficult to put in capacitive senders now. I would stick with the floats for ease of installation.

Click to expand...

Tanks are closed, so capacitive is not an option at this stage.

Alain.

rv7charlie said:

Alain,

You didn't ask about this, but...

Are you planning on having an inverted oil system in the plane? Because if you're not, you could re-consider using the flop tubes. They are only useful if you do sustained inverted flight (not something most RV drivers do). The flop tube installation is significantly more complicated, with extra failure modes, such as additional joints and the potential for the tubes to hang up. And they drive other changes, such as moving the level senders to the next bay.

If you do typical 'gentleman's acro', meaning loops, rolls, cuban 8's, etc that have no sustained negative G's, then the flop tube does nothing for you. I say this as an RV owner/frequent acro flyer for over 20 years, who removed the flop tube from my current RV-4.

FWIW,

Charlie

Click to expand...

This is very, very good advice!

Our Airshow sequence has a couple of inverted maneuvers that we fly and they have at times been flown on the non flop tube tank, inadvertently during practice. The engine did not stumble until we rolled back upright. This happened after as much as 15 seconds while inverted.

Also, the chances of the flop tube hanging up and causing fuel starvation with lots of fuel in the tank IS VERY REAL!!!!!!!!!!!!!!


So, unless you wish to fly around looking at the terrain through the top of your canopy I would highly recommend getting rid of the flop tubes and get a new tank access cover that is prepunched for the float sender and install the standard plumbing and sender. That would be easier than cutting a hole in the back baffle and mounting the sender in the next bay.

My 2 cents!

Hi Alain

Drawing 16A in the lower right has a sketch of the flop tube installation. No detail as how to do it though. I used the original tank access plate, T-708, as a template for drilling the holes. I then also cut out the inner part of the T-708 to use as a doubler. Not sure if that was necessary, but its easy to do.


Above I have used screws and nuts just to hold the sender in place while adjusting, the final install used K-1000-08 nut plates. Inboard 2 baffles removed.



Don't forget that if you do go this route, you should wire up your senders before putting the tanks back on the wing, otherwise you'll just have to remove them once again!

So for installation of float senders through the rear baffle you will need a pair of float senders, pair of T-708, 10 K100-08 nut plates and 8-32 screws. Oh, and sealant of course.

Having said all of the above, simply removing the flop tubes might be much easier, especially if you now are not sure you want them. You'd need to plug the hole left somehow, there must be a way. After that you'll need all of the items mentioned above plus the normal fuel pickups and T-715 anti-rotation brackets.
The plans show the pickup made by the builder from 3/8 tube, but vans sell a pre- made pickup with a finger screen. much easier.

If you need the float senders, I have a set. I ordered with floaters from Vans in 2013 but ended up with capacitive.

I converted mine by removing the flop tube, capping the flop tube's bulkhead fitting, and installing the 'standard' fuel pickup and float sender in the inspection cover. Then new fuel line into the fuselage to the selector, and done.

Charlie

I used Belite bendable capacitance probes in the next outboard bay, mounted from the rear tank baffle on a blank cover plate. Location and set up is just like the float senders would be (per mod on 16A), just using cap probes bent into a ? shape instead of the floats. Floats are cheaper and do the job, was just a personal preference for me.

Chris

Removing flop tubes

Gents,
Thank you so much for all your advices.
I will be removing the flop tubes and install the standard fuel pickup with float fuel senders on the access panel.
Ordering the parts from Vans soon and will do the job when I receive everything.

Last question: what is the best solution to plug and seal the holes where the flop tubes pickup are coming out of the tanks?
Would a couple of simple AN caps on the AN fittings with sealant be enough (after removing the flop tubes of course) ?

Alain.

When I removed my flop tube several years ago, I simply capped the bulkhead fitting with a standard AN-6 cap.
https://www.anplumbing.com/adapters/caps-plugs.html
No sealant is needed for AN fluid fitting joints. (Obviously, you still need to seal the pass-through point of a bulkhead fitting, but nothing is needed where the fittings mate to each other.)

As long as the bulkhead fitting isn't leaking where it passes through the end rib, just cap it. I capped mine on the outside of the tank. Don't forget to stabilize the bulkhead fitting with another wrench when you remove the flop tube, and when you cap it. You don't want to risk twisting the bulkhead fitting in the rib, which could break the proseal seal and/or loosen the nut on the fitting.

Charlie