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RV10 ER Tanks

Richard Connell

Well Known Member
Today VHXRK officially graduated from RV10 to RV10ER.
I had approximately 100h on her before I started this project in late Jan.
It took 90h to build the new tanks and around 50h to complete the modifications on the airframe.
As others have mentioned, the quality of the parts, jigs and instructions are top notch.
I opted to put in two SW senders in each tank, modifying the inboard sender to place both senders in series.
I calibrated each tank for both flight and ground attitudes in 5L (1.25gal) increments.
This resulted in a nice smooth sensible calibration curve that calibrated all the way from empty to full. A big improvement from the stock single sender RV10 setup.
As Ken sez, the fun factor goes down a bit on a flying 10. Make sure you have a comfortable crawler and some goggles. You’ll spend a lot of time under the wing making metal on top of yourself! You may also learn some new words removing and installing the tanks.
All that said this is a very achievable modification to a flying 10. I’m very glad I made the effort.
It would be trivial on wings under construction.
Here’s some random pics.


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Very nice job!

Although I am using the CiES senders in my ER tanks, I am interested in specific details as to how you modified the SW senders. If you can provide more information, I believe that will be useful to others building ER tanks that don't want to spend the big bucks for the CiES senders.

As you mentioned, building and installing these tanks on SB 10 or 14 wings would be incredibly easy. It's also easy to install better fuel caps (like the Newton Aero 300's) at the same time.

Ken did an outstanding job designing and fabricating these kits.
 
Interested to see if you have any dimensions or more pictures of where you drilled on the SW senders to install the terminal post. Did you get it so close to the sending unit you had to grind down the insulator pieces or no?
 
Richard-

Thanks for the writeup and pictures. I am about to embark on this project on my flying (and painted!) RV-10.

Krea-

Do you have any more info on the Newton 300 caps - is a new flange needed, etc?

Thanks,
Thomas
 
Great job Richard! Congratulations. You've set a new speed record for ER tank installation. If you're not careful, you'll have people lining-up to have you modify their planes :)

Thanks for sharing your experience and the photos are super helpful as well.
 
Great job Richard! Congratulations. You've set a new speed record for ER tank installation. If you're not careful, you'll have people lining-up to have you modify their planes :)

Thanks for sharing your experience and the photos are super helpful as well.

Haha Thanks Ken.
I think I'm cured of the desire to build anymore tanks for now!
I marvel at your ability to provide parts of such accuracy that one can undertake such a project. It really is amazing.

Krea and Thomas:

The tank skins are punched for the Newton SPRL flange
T-00007B. Vans provides this standard flange with a plastic cap. I ordered the flange only and then ordered the metal locking cap from Spruce:
https://www.aircraftspruce.com/catalog/appages/newton_sprl.php

Ill post again later some more details about the sender modification for everyone.
 
Dual Tank Senders In Series.

I used the standard SW senders.
the outboard one is per plans.
The inboard one has an electrical bulkhead terminal installed into the sender plate.
Access is tight so I found the smallest one I could.
The stud is around 3/16, the hole in the plate is 1/4 an the OD of the delrin bushing halves is probably 1/2 or maybe 9/16 - I didn't measure it.
It didn't come with any specs or instructions so I had to work my way up with drill bits slowly on the first one until I had the right size.
The bushings have a step to keep them centred and a Viton Oring on each side.

I had to neaten up the phenolic insulator on the inside of the sender to push the passthrough as close to the centre of the plate as possible.
Then I bolted it up, crimped some AWG14 onto a ring and prosealed it throughly. Don't trust the thread leak path.

The other end of my AWG14 is soldered onto the sender where the chassis ground used to be. I removed the original black wire grounding the sender.
So the signal wire from the outboard sender effectively becomes the new ground for the inboard sender. Its important obviously that this doesn't touch any part of the airframe and that you remove entirely the ground side wiring of the original inboard sender.

The access hole had to be dremeled out a touch to make room for the passthrough. you don't want to overdo this. There's still about 1/4 of prose gasket there.

Calibration was straight forward. I opted to calibrate in 32x5L increments out of curiosity to see what the curve would look like. I forgot to take a photo of the curve. ill update this thread with a photo next time I get a chance.

One thing I noticed is that you need to be patient with waiting for the fuel to drain inboard, and you need to give the wings a wiggle up and down to make sure the sender wipers move. I suspect they need some wearing in and/or stationary on the ground there can be just a smidge of friction. In flight I'm sure motion/vibration would negate this.

Ive flown 2h and had the tanks sit full for 3 days with no leaks so I'm calling it good. In flight, the totals remaining on the tanks + Fuel flow used have been within 1/2 Gal of total useable so I'm pretty happy. ill see how it is further through the range as I've only burnt 70L (15gal) so far.

Ive scribbled a diagram at the bottom as well. sorry the photos aren't in order.

Hope this is useful!




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Richard-

Thanks for the writeup and pictures. I am about to embark on this project on my flying (and painted!) RV-10.

Krea-

Do you have any more info on the Newton 300 caps - is a new flange needed, etc?

Thanks,
Thomas

On my standard tanks, I installed the Newton caps that Van's used to sell. Their flanges had a lot of curvature and took significant effort to shape to the curve of the RV-10 skin.

I've bought a set of Newton caps for the ER tanks (on Spruce they have a model that is specifically recommended for the RV-10) and the new caps are much flatter and look like they will fit a lot better. I haven't started fitting them yet, though.
 
On my standard tanks, I installed the Newton caps that Van's used to sell. Their flanges had a lot of curvature and took significant effort to shape to the curve of the RV-10 skin.

I've bought a set of Newton caps for the ER tanks (on Spruce they have a model that is specifically recommended for the RV-10) and the new caps are much flatter and look like they will fit a lot better. I haven't started fitting them yet, though.

I bought the AERO 300 NON LOCKING FUEL CAP. Is this the set you bought?

I was steered to that part after reading a note in the "Reviews" section posted by "Robin V" (formerly of Newton) on the "AERO 300 - A30 LOCKING AND NON-LOCKING FUEL CAP" product page.

Cap Review.jpg
 
I think Richard covered pretty much everything, but I wanted to provide a little additional detail (and thanks Richard for the explanation of the SW sender series mod).

I installed the Newton Aero 300 caps in my original slow build tanks. They were the smaller opening version and the Newton provided Vans flange worked well.





As Richard mentioned, the new ER tanks for the 10 (and I assume the 14) have the larger opening designed for the Newton SPRL plastic cap. At the time we built our ER tanks, either I was unaware, or Newton had not offered an all metal locking SPRL replacement cap - so we installed the smaller diameter flange and cap. The downside of this is a small reveal around the flange which can be a benefit to reduce paint chipping, but also requires additional effort to ensure the flange is centered on the opening. (Ours is centered, it just looks off center in this picture).

 
I bought the AERO 300 NON LOCKING FUEL CAP. Is this the set you bought?

I was steered to that part after reading a note in the "Reviews" section posted by "Robin V" (formerly of Newton) on the "AERO 300 - A30 LOCKING AND NON-LOCKING FUEL CAP" product page.

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According to my Spruce order history, this is what I bought:

https://www.aircraftspruce.com/catalog/pnpages/05-26740.php

The one you linked appears to be the one with a lot of curvature to the flange.
 
In these pics you can see that the Newton caps I bought (details above) Are smaller in diameter than the hole in the ER tank skins, but that there's a ridge, unlike in other pictures, and the overall difference appears to be less.

That ridge should allow me to fill the empty space with a decorative bead of Proseal or some other flexible sealant like Silpruf (not sure if that's fuel proof).
 

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Cap

The more commonly used cap, not necessarily on RV's but on many others, is the Usher cap. Available with flat or contoured flange. Been around for decades.
 
The more commonly used cap, not necessarily on RV's but on many others, is the Usher cap. Available with flat or contoured flange. Been around for decades.

Quite true and it’s what we had on our RV-7. If you have ever used a Newton cap (OEM on Cirrus, Diamond and others) - you would never want to use an Usher cap again. The Newton operates with a gentle finger pull - no prying with a fuel strainer screwdriver or other tool. Much better engineered mechanism than the Usher in my opinion.
 
My 7 had the Newton caps. I took one look at the ushers when they arrived and put them in the cupboard. As Krea says they are a step change up from the Ushers. You’d never go back.
My original 2017 vintage RV10 skins were punched for the usher caps and I again used the newtons.
Sometime after then Vans changed to the SPRL and the hole got bigger.
I’ve actually got a cupboard full of usher caps and flanges I’m sure they are worthless but someone local will lose one one day and I’ll have a spare for them!

These caps are a good example of the incremental improvements that Vans has made over the years that mostly pass people by unless you’ve seen/tried all flavors.
The SPRL flange is a beautiful machined, anodized and pre drilled flange that fits the tank curvature perfectly. No tweaking or filing of the flange. It’s literally impossible to mess up.
 

Thanks again for the information on using SW senders in the ER tanks. Nice to have a lower cost option than the CiES senders to be able to read full to empty, especially with the additional fuel available.

My preference is still the CiES senders with all of the electronics outside of the fuel tank, higher MTBF and greater accuracy. All of that does come with a very steep price, though.
 
Thanks again for the information on using SW senders in the ER tanks. Nice to have a lower cost option than the CiES senders to be able to read full to empty, especially with the additional fuel available.

My preference is still the CiES senders with all of the electronics outside of the fuel tank, higher MTBF and greater accuracy. All of that does come with a very steep price, though.

No worries. Hopefully its of use to people.
 
Dual tank senders in series

Richard,
Did the components used to modify the inboard sensor come in a kit? It appears that way from the pictures. Any further details on the parts source and process?

Thanks!
 
Richard,
Did the components used to modify the inboard sensor come in a kit? It appears that way from the pictures. Any further details on the parts source and process?

Thanks!

https://www.ebay.com/itm/192904676611

Hi Todd,
This is the bulkhead fitting I used.
Install check out the pics. Drill hole. Bolt on. Proseal.
Just make sure you give yourself enough room to make a nice seal on the sender plate to the tank rib.
 
HELP ON THE SENDER WIRING

Okay folks I am driving myself crazy here. I cannot figure out how to wire up these senders. Here is my spefifics....
I have my RV10 Sky Designs ER tanks almost assembled.

I am using the Vans Stewart Werner floats. I opted out of CIES. I have added the additional outboard sender to the tank which only has a range as indicated in the plans from half to full. The IB sender has full range empty to full.

I was talking to Ken from SD and he pointed me to someone in AU who added a tank pass through fitting to the sender. I was told there is nothing like this available in the US?? WHAT IS THE POINT OF A PASS THROUGH GOING IN THE FLANGE OF SENDER... see this link from AU. If someone has another link for here in the US I would be appreciative.
https://www.efisolutions.com.au/electrical-bulkhead-terminal-submersible-e85-compa


I spoke with Garmin this morning and THEY told me I can run both IB and OB sender grounds together and have just one ground wire per wing side running up to the GEA24. ????????

AS FOR THE POWER I AM UNDER THE IMPRESSION I NEED SHIELDED WIRE 22AWG and I need to run power wires in a series formation to the GEA24. BUT HOW.....

SO WHAT I NEED HELP WITH IS DO I EVEN NEED A PASS THROUGH OR CAN I JUST RUN THE SHIELDED POWER WIRES WITHOUT IT THROUGH SERIES. IF SOMEONE CAN TELL ME SPECIFICALLY HOW THE POWER WIRES ARE RUN I WILL APPRECIATE IT. (do the power wires get tied together and then one power wire per wing side run to panel?????)

PARDON MY IGNORANCE HERE. I AM A FIRST TIME BUILDER AND LEARNING ALONG THE WAY. The dual senders in these ER tanks is not a normal config and its taking some research to figure out how I will do it for it to function and operate properly.

ANY HELP WILL BE GREATLY APPRECIATED:)
 
which only has a range as indicated in the plans from half to full. The IB sender has full range empty to full.

I don't think this is right, you wasn't to have the outboard sender arm swing from the bottom of the tank to the top of the tank. Same as the inboard sender.
Ideally this corresponds to the full range of motion on the sender in both cases - but its probably not critical.

I was talking to Ken from SD and he pointed me to someone in AU who added a tank pass through fitting to the sender. I was told there is nothing like this available in the US?? WHAT IS THE POINT OF A PASS THROUGH GOING IN THE FLANGE OF SENDER... see this link from AU. If someone has another link for here in the US I would be appreciative.
https://www.efisolutions.com.au/electrical-bulkhead-terminal-submersible-e85-compa


I spoke with Garmin this morning and THEY told me I can run both IB and OB sender grounds together and have just one ground wire per wing side running up to the GEA24. ????????

AS FOR THE POWER I AM UNDER THE IMPRESSION I NEED SHIELDED WIRE 22AWG and I need to run power wires in a series formation to the GEA24. BUT HOW.....

SO WHAT I NEED HELP WITH IS DO I EVEN NEED A PASS THROUGH OR CAN I JUST RUN THE SHIELDED POWER WIRES WITHOUT IT THROUGH SERIES. IF SOMEONE CAN TELL ME SPECIFICALLY HOW THE POWER WIRES ARE RUN I WILL APPRECIATE IT. (do the power wires get tied together and then one power wire per wing side run to panel?????)

PARDON MY IGNORANCE HERE. I AM A FIRST TIME BUILDER AND LEARNING ALONG THE WAY. The dual senders in these ER tanks is not a normal config and its taking some research to figure out how I will do it for it to function and operate properly.

ANY HELP WILL BE GREATLY APPRECIATED:)

The senders are resistors that measure resistance to GROUND. There is no power involved anywhere. There is no need to have any shielded wires anywhere.

Theres no problem with just connecting the two senders (resistors) together in parallel and pinning them both to the same pin on the GEA24. This is by far the simplest method. No pass through required.
However, it means you are likely only using a smaller range of the GEAs resistance 0-500Ω.

The senders measure from 30Ω to 240Ω. If you put them in parallel (joined together - no pass through) then you are effectively measuring 15Ω to 120Ω.
In series (with a pass through - see pic below) you are measuring 60Ω to 480Ω.

I don't think in practise it makes too much difference, but I was happy to experiment with doing it the hard way and im happy to report that the fuel gauges appear to be very close to the totaliser (which I know is accurate to within 0.25Gal at each fill. which is pretty good for 41Gal tanks)

have a read of this if you havent already too: https://vansairforce.net/community/showthread.php?t=214497&highlight=series+parallel

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this is what Ken sent me as far as the OB sender goes and the trave is only from 50%-100%. I emailed him about this and he said the following:

"There is no way with the Stewart Warner sender to get more degrees of travel...you gotta work with what you've got and, at least in this case, half travel on the outboard sender is fine.

I think this thread: https://vansairforce.net/community/showthread.php?t=214938 will do you the most good in terms of understanding the electrical modifications you'll need to make to the outboard sender. Probably the most challenging aspect will be the pass-through stud. Richard Connell is in Australia, so the source he went to for that little electrically isolated stud won't work for us here in the USA. I tried briefly to find an equivalent item from a domestic source but nothing came-up within the first few minutes of searching. If/when you find something that works, please let me know...that will be helpful to others who are sure to have the same question."
 
That’s interesting. That diagram wasn’t available AFAIK when I did mine so my float arm looks nothing like that.

It’s a bit of a pretzel, but my float ends up just ahead of the J stiffener and articulates through the whole range right down to the bottom. I accept that it may not quite get to the same total full height, but my calibration as still moving right up to the last 1/2 gal so I don’t think I’m missing any range at the top.

I don’t want to call into question Ken’s drawing but I’d be keen to know whether there could be some deadband between the top of the inboard float and the bottom of the outboard float with that geometry.
 
It does look a little larger than the ones I found. 13.9mm hole is getting big. There really isn’t that much room to play with.
It does also look like it is designed to pass through a thicker material too.
It may work if you shave of some of the sender plate facing side.
I’d probably try find a smaller one.
 
At this point it’s getting so frustrating…. But it’s all a learning experiment….. no pun intended haha!
What do you think of this pass through

https://www.racetronix.biz/p/bulkhe...MI2M2F9JLm_gIVdAhlCh0_RgDhEAYYAyABEgJ9AfD_BwE

That is too big. I bought it and it wasn't going to work so I ran my own. Bought a 6/32 stainless bolt and nut and washers and used hdpe plastic dowel from online metals. Then drilled the center out of the dowel so the bolt could fit through and a slightly larger size dowel with center drilled out to fit over the smaller dowel and set as a washer on each side.

I plan to do a decent write up with pictures in the thread Richard started but not sure when I'll get to it. I leak tested tanks and they passed so it worked out.
 
I was planning alternatively on mounting the pass through to the baffle instead of in center plate?? I am trying to wrap my head around what will have to be different in that case??
 
I was planning alternatively on mounting the pass through to the baffle instead of in center plate?? I am trying to wrap my head around what will have to be different in that case??

You have to modify the inboard sender anyway so it makes sense to have it all in the one place. Whatever you do with the outboard sender wire you still need to solder it onto the ground tab of the inboard sender inside the tank. Not too hard I suppose.
If you like I can buy some of these cheap small ones here and post them to you guys snail mail.
Let me know if anyone is interested in that.
 
I was looking at your pics in detail and I think I am going to try and make one tomorrow. I ordered the larger pass through fittings but if I have to get a smaller size I will let you know. Thanks

Your pictures look like it shows the outboard sender wire goes to the post on the inboard sender?
 
I was looking at your pics in detail and I think I am going to try and make one tomorrow. I ordered the larger pass through fittings but if I have to get a smaller size I will let you know. Thanks

Your pictures look like it shows the outboard sender wire goes to the post on the inboard sender?

Yep. The signal wire from the outboard sender becomes the ground for the inboard sender. The senders have a black ground wire which goes from the actual sender to the chassis (you can see a rivet and terminal) You need to remove that black ground wire from the inboard sender and replace it with a wire from the inside of the pass thru stud to the sender. Now they in series.

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Ahhhhh gotcha….. yes I just removed the black wires from the inboard senders!:)

Then on the outside part of the pass through it runs in to gea 24?

And nothing is under the inboard screw terminal?

I think I got it now
 
Ahhhhh gotcha….. yes I just removed the black wires from the inboard senders!:)

Then on the outside part of the pass through it runs in to gea 24?

And nothing is under the inboard screw terminal?

I think I got it now

Outboard screw terminal wires to inboard pass thru.
Inboard screw terminal wires to GEA24
 
Gotcha now your pictures all make sense and the light bulb went off in my head. Haha:)

I was talking with Ken earlier and he said as an alternative I can just install it into the rear baffle. I have to find decent location to drill rear baffle hole.
 
Gotcha now your pictures all make sense and the light bulb went off in my head. Haha:)

I was talking with Ken earlier and he said as an alternative I can just install it into the rear baffle. I have to find decent location to drill rear baffle hole.

Yeah it’s simple once you “see it” :)

That’s fine, I’m sure that’ll work as well. keep in mind:
-It’s an extra hole
-in the rear baffle is inaccessible with the tank installed - if you have a leak.
-you’ll need to make the wire long enough to pull out the inboard sender hole, solder to the sender then push it all back inside. Making sure it don’t foul the sender.
 
ER Tank Sender Mod

If anyone needs the pass thru terminal for the Stewart Warner senders as Richard used, I have two sets available. Decided to go with Cies senders. Terminals were imported from AUS, so quick turnaround for US locations. PM for more info.
 
thank you I appreciate it! :) Being in the experimental catageory we are all here to learn something and I just wanted to pass it on to others as you did to me.

Thank you. Have you ever been to AirVenture??

PS It must be kick *ss to fly around Australia. I would love to do that one day with some ferry tanks but time will tell!!
 
Hey great video! I just received my ER tanks and will work on them when the wing kit comes in. One question I had for you was where did you end up sourcing the pass-thru hardware?
I appreciate you putting the video together, it makes a lot sense now that I can see it! Thanks! And thanks to Richard Connell, too!
 
hey John thank you for the praise. Yea, I was spending a week looking this up and doing research. Since these tanks are newer on the market there isnt really much help out there. I also posted a few videos on the wing spar alterations if you want to click on my link below for my YouTube channel. I was confused about a little and I had to read the plans several times. I got it though and the first tank was leak free effective this morning. I am doing the right side now and I'm pretty sure I can buid a second leak free tank :) Fingers crossed!

I lived in AZ for 7 years. I went to ERAU in Prescott and then lived in Tuscon for 3 years. Miss it out there but not the Phoenix heat haha. Also miss In 'n Out:-(

here is the link for the pass through

https://www.racetronix.biz/p/bulkhead-stud-6mm-delron-viton-ss/bhs-6mss?dfw_tracker=58263-BHS-6MSS&gclid=EAIaIQobChMI2M2F9JLm_gIVdAhlCh0_RgDhEAYYAyABEgJ9AfD_BwE
 
hey John thank you for the praise. Yea, I was spending a week looking this up and doing research. Since these tanks are newer on the market there isnt really much help out there. I also posted a few videos on the wing spar alterations if you want to click on my link below for my YouTube channel. I was confused about a little and I had to read the plans several times. I got it though and the first tank was leak free effective this morning. I am doing the right side now and I'm pretty sure I can buid a second leak free tank :) Fingers crossed!

I lived in AZ for 7 years. I went to ERAU in Prescott and then lived in Tuscon for 3 years. Miss it out there but not the Phoenix heat haha. Also miss In 'n Out:-(

here is the link for the pass through

https://www.racetronix.biz/p/bulkhead-stud-6mm-delron-viton-ss/bhs-6mss?dfw_tracker=58263-BHS-6MSS&gclid=EAIaIQobChMI2M2F9JLm_gIVdAhlCh0_RgDhEAYYAyABEgJ9AfD_BwE
Awesome, thank you so much for the link, and yeah of course on the praise! I've enjoyed watching your videos, and actually decided to pull the final trigger on buying the ERs after watching your unboxing. They showed up super quick, even all the way out to AZ. I'm sure I'll be reading the plans a lot as well, so I appreciate you and the videos.

And yeah, I'm a fan of In 'n Out, definitely good stuff. I lived in MD for a bit for work, and I missed it quite a bit. Although I'll be honest, I miss Yuengling now being out here ;) And very cool about ERAU! I'm actually going there now (my work is paying for it) going through their masters of space operations program, it's been a ton of fun.

Thanks again for the link, and bulkhead pass throughs are orders!
 
Basic DC electricity fascinates me so I'm drawn to threads like these despite my "lack of standing" - no ER tanks and no plans to add any.

I understand the desire to instrument everything as fully as possible to fully exploit the capabilities of our whiz-bang glass panels. The resistive float senders are not capable of accurate display of fuel quantity in RV wing tanks due to dihedral and their location. in the root end of the tank. The first portion of fuel burn from a full tank will not change the reading from the sender. I assume this is also true of the senders in the ER tanks in use here. Wiring them in series makes the most sense (although wiring them in parallel with a series resistor added to the ER sender should also give a "calibratable" and usable resistance curve). This will give a setup where the first portion of fuel burned from each tank is not measurable by the float senders, and the calibration curve will have two "flat spots" as the total fuel load fuel is burned off.

So a question arises - since we can't expect linearity from the float senders and we are almost certainly running totalizers in these sophisticated panels: why do we even need to equip the outboard/ER tanks with a sender at all? Seems we should have a good idea from the stopwatch and selector valve how much is in the ER tanks at any given time (or your roll trim requirement will tell you) - and once we get down to fuel levels that are critical to know for safety of flight, the senders in the factory tanks will let you monitor the burn of the final fifty gallons with good accuracy. If one lost track of fuel burn in the first sixty gallons (or maybe the ER tanks both sprang a leak in flight or a fuel cap popped off and was lost?) and was surprised to see the fuel in the inboard tanks already being consumed, it seems to me that the second sixty gallons, where accurate measurements are available with only inboard tank sensors, should give the pilot about five hours to arrive at a safe landing and sort things out on the ground.

Just my KISS bias creeping in I guess. Maybe there are regulatory requirements for every tank in the aircraft to have a gauge. I personally think I'd wire parallel or omit the ER senders altogether if I were to install extended range tanks. Are we sure the pass-through terminal insulators are gasoline-resistant in the long term? (We thought ProSeal was fuel-resistant forever until we started seeing evidence that maybe it wasn't).

If this was discussed earlier in the thread and the rationale was established, I apologize.

Carry on; fly safe.
 
……(snip)…..So a question arises - since we can't expect linearity from the float senders and we are almost certainly running totalizers in these sophisticated panels: why do we even need to equip the outboard/ER tanks with a sender at all? Seems we should have a good idea from the stopwatch and selector valve how much is in the ER tanks at any given time (or your roll trim requirement will tell you) - and once we get down to fuel levels that are critical to know for safety of flight, the senders in the factory tanks will let you monitor the burn of the final fifty gallons with good accuracy. Just my KISS bias creeping in I guess……

All 100% valid points and definitely not “needed”. I’m going with the CiES fuel senders in my -14 build with the ER tanks and have gone back and forth with trying to decide if I should put the duel senders or not. In the big scheme of things, and IMHO, the duel senders really don’t add very much complexity or cost but does give you that little bit extra utility. At this point, I’m planning on going with duel senders as well. However, with that being said, I definitely think the duel senders are a lot more of a want rather than a need.
 
Hi Bill,
Theres another thread about the rationale somewhere.
Keep in mind its one tank, not an additional tank.
Its unlikely a certified plane would get away with having the gauges only read 60% of the tanks capacity. But yes you can fly like that. Most 10s have the same problem to a lesser degree.

cheers

Basic DC electricity fascinates me so I'm drawn to threads like these despite my "lack of standing" - no ER tanks and no plans to add any.

I understand the desire to instrument everything as fully as possible to fully exploit the capabilities of our whiz-bang glass panels. The resistive float senders are not capable of accurate display of fuel quantity in RV wing tanks due to dihedral and their location. in the root end of the tank. The first portion of fuel burn from a full tank will not change the reading from the sender. I assume this is also true of the senders in the ER tanks in use here. Wiring them in series makes the most sense (although wiring them in parallel with a series resistor added to the ER sender should also give a "calibratable" and usable resistance curve). This will give a setup where the first portion of fuel burned from each tank is not measurable by the float senders, and the calibration curve will have two "flat spots" as the total fuel load fuel is burned off.

So a question arises - since we can't expect linearity from the float senders and we are almost certainly running totalizers in these sophisticated panels: why do we even need to equip the outboard/ER tanks with a sender at all? Seems we should have a good idea from the stopwatch and selector valve how much is in the ER tanks at any given time (or your roll trim requirement will tell you) - and once we get down to fuel levels that are critical to know for safety of flight, the senders in the factory tanks will let you monitor the burn of the final fifty gallons with good accuracy. If one lost track of fuel burn in the first sixty gallons (or maybe the ER tanks both sprang a leak in flight or a fuel cap popped off and was lost?) and was surprised to see the fuel in the inboard tanks already being consumed, it seems to me that the second sixty gallons, where accurate measurements are available with only inboard tank sensors, should give the pilot about five hours to arrive at a safe landing and sort things out on the ground.

Just my KISS bias creeping in I guess. Maybe there are regulatory requirements for every tank in the aircraft to have a gauge. I personally think I'd wire parallel or omit the ER senders altogether if I were to install extended range tanks. Are we sure the pass-through terminal insulators are gasoline-resistant in the long term? (We thought ProSeal was fuel-resistant forever until we started seeing evidence that maybe it wasn't).

If this was discussed earlier in the thread and the rationale was established, I apologize.

Carry on; fly safe.
 
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