[DonMcKee]

I'm building an RV-14A, and decided to use dual CiES fuel senders in each of my standard tanks. I just wanted to share my experience with the next builder coming along.

TL;DNR version:

• the short, fat, floats used on the inboard senders do not fit through CiES' custom nutrings.
• the inboard senders were "clocked" opposite of their labeling, i.e. the one marked "INBD LH" will go in the right tank, and the one marked "INBD RH" will go in the left tank. Test your senders before installing!
• the default arm shipped with the outboard sender is too long to mount on the tank baffle. Explicitly ask for a 2.5" arm.

Long version:

Right off, I'd like to say that working with CiES has been easy, and Daniel, in customer support, has been very responsive, although apparently very busy. However, not all has been smooth sailing.

After a long telephone chat with Daniel at CiES, it seemed that ordering would be a relatively painless process. I explained that I intended to install the inboard senders in the "per plans" location on the inboard end rib, and the outboard senders on the rear baffle of the tanks, in the most outboard bay. AFAIK, all of the RV-14 builders who've posted regarding installing an outboard sender used the baffle location for mounting.

I decided to pull the trigger and order a set of four senders. The online order form let me select the type of aircraft ("RV-14"), and the number of senders I needed per tank ("2" or "4"). Per other's experience, I believed this was all the info CiES needed to complete the order. I was told 3 to 4 weeks to complete construction, at which time I'd be invoiced for the order. While in process, I decided to splurge and added 2 CiES fancy (gold plated? ) nutring kits to my order (a total of 4 nutrings, plus everything to get them mounted).

About 3 weeks after ordering, the senders were ready to go. I paid the invoice, and promptly received my order. Pretty quickly, I ran into issues:

• the arms of the outboard senders were sized more in line for mounting on on the rib, rather than on the baffle (but I think they were still too long for a rib mount on my std tank):

• the short-and-fat custom RV-14 floats used on the inboard senders were too fat to fit through their nutrings once attached to the rib (note: in the pics, the nutring is on the outside of the rib, but mounting it correctly didn't change anything):

• the inboard senders were "clocked" opposite of the intended tank where they were marked for (left vs. right).

Daniel, at CiES, was helpful and agreed to send a pair of shorter arms, which his records showed had been used by previous RV-14 builders. He also agreed to let me return one of the nutring kits for full refund, and I sourced a pair of new Textron/Cessna nutrings from a VAF builder to use as a replacement (Thanks, Phil S.!). As for the right vs. left tank discrepancy, Daniel said the senders were profiled per the info they had on file regarding the Van's supplied inboard rib, so there was either a manufacturing defect with my ribs, or Van's has changed their spec (BTW, there were a couple of other VAF posts from builders who said their senders were backwards). But, no matter, this one was an easy fix: the sender marked "INBD LH" will go in the right tank, and the one marked "INBD RH" will go in the left tank.

The replacement outboard sender arms eventually arrived, but they were still 3/4" too long! I artificially shortened the arm to the length I needed and sent pics and video to Daniel to show him what I needed, and how it would work in my tank. He said that they had one shorter arm I could try, but they have no records of any RV-14 builder who used arms this short (which was curious, because the pics in this PDF writeup, and a pic I found on VAF, appear to have arms the same length that I came up with in my trial-and-error testing. Hmm....). Anyway, this is what I needed (bottom), vs. what I received (top):



The next set of shorter arms arrived, and they looked like they would work. They turned out to be about 1/4" shorter than what I had during my testing, but a little short was better than a little long. Being a little short gave me mounting options, so that was okay ("Should the sender top out when the float contacts the top skin? When it reaches the expected max fuel level? Something else?"). I went ahead and mounted the new arms on the senders:



While all of this was going on, I'd made a cardboard mock-up of the baffle section over the outboard tank bay so I'd be able to test the sender location before cutting holes in the baffle. When I tried to mount the sender with the new, shorter, arm, it wouldn't fit through the CiES nutring. Argh! I decided to bend the arm to see if I could get it to work. It took a couple of bends to make it fit. It turned out that with the bent arms, the total sender length (5.6") almost matched what I came up with during testing (5.68"):



So, I this is what I'm going with. I returned the "reject" arms and nutring kit to CiES, and promptly received my refund for the kit.

For comparison, here is the succession of arms that I tried with the outboard senders:


Anyway, I hope something here is helpful for someone down the road.

 

[dmattmul]

Not to put down anyone’s build what you want but for the standard RV-14 tanks Vans senders record starting at 21 gals each side so you don’t get to see the first 4 gals used. Of course if you want to know the fuel totalyzer will let you know 42 to 50 gals. 42 gals readable volume is over 4 hrs of time in the air or 3 hrs with a 1 hr reserve. The Vans fuel senders have proven extremely accurate.

 

[DonMcKee]

... build what you want ...

Exactly. I want to have fuel gauges that'll be accurate full to empty.

 

[dmattmul]

Exactly. I want to have fuel gauges that'll be accurate full to empty.

Again, I'm into building what you want but just so I can understand what does it cost one to know exactly how much fuel is in your tank from 21-25 gals? (Maybe I need to consider if the 15 ever comes out) BTW my 10 I can't tell how much fuel is in the tank from 21 - 30 each side but of course the totalizer tells the story then. But if I had ER, would probably bite the money bullet.

Garmin even has a display for fuel remaining at destination.

 

[Richard Connell]

I’ve got ER tanks with just your bog standard resistive $50 stewart Warners inboard and outboard wired in series.
They calibrated up perfectly and always match the totalizer within a gallon for the full tank capacity and the totalizer is within half a gallon at each fill.
They are every bit as accurate as the plate capacitive senders that I had in my RV7.

Each to their own - one sender or two -$50 or $750 - but you can buy a lot of fuel for 2.5k+ that 4 Cies float senders cost and get no real world benefit.

Not relevant to this post but you have to wonder why some people spend 10x extra on a “more accurate” sender and then only put 1 of them in each tank and not measure the top 20% of the tank at all.

 

[bertschb]

...and get no real world benefit.

Some people consider improved reliability to be a real benefit. CiES claims a Mean Time to Failure of 60,000+ hours and offers a lifetime guarantee. Removing fuel tanks to replace failed SW senders is no big deal to some people. It's a very big deal to others which is why they are willing to pay the higher price for the CiES senders.

For some builders, money isn't the prime driver when considering equipment for their build. Safety, reliability and quality are more important.

 

[bkervaski]

Exactly. I want to have fuel gauges that'll be accurate full to empty.

I'm not sure if it was mentioned but you would need 2 fuel senders (4 total) per tank to achieve this due to the dihedral, regardless of the type or brand. If you're just using 2 fuel senders you have to choose what you want to get an accurate measurement from, top of the tank or bottom ... most would choose the bottom

 

[RVbySDI]

Some people consider improved reliability to be a real benefit. CiES claims a Mean Time to Failure of 60,000+ hours and offers a lifetime guarantee. Removing fuel tanks to replace failed SW senders is no big deal to some people. It's a very big deal to others which is why they are willing to pay the higher price for the CiES senders.

For some builders, money isn't the prime driver when considering equipment for their build. Safety, reliability and quality are more important.

I will preface my following statements by stating that this is just a comment on the fact that we have historically only had the use of only having fuel gauges to measure fuel compared to our current capabilities to use a different measuring tool for much better accuracy. As others have stated: build what you deam the best for your goals.

Having said that, the fuel totalizer provides much more accuracy than any of the fuel quantity gauges ever will. So much so that even though I do have fuel quantity gauges for both fuel tanks, I actually pay little attention to them. The fuel flow sensor(s) and fuel totalizer are accurate to within one tenth of a gallon. I really don’t think any amount of tinkering will improve any fuel quantity sensor enough to get that accurate.

I know at any given point in the flight how much fuel I am burning at that specific time; I know how many gallons per hour I am burning; how much has been used; how much is still left to use; how much time is left to empty; how many miles left to fly, in either knots or statute miles, to empty. All of that information is available to me for the full tank all the way down to the last one tenth of a gallon left in the tank. That is a lot of information that a fuel quantity gauge will not be able to give me.

 

[gasman]

Even when fuel is flowing out of a tank that lost a cap in flight, your totalizer would show fuel that was not there....

 

[chaskuss]

snipped
I decided to splurge and added 2 CiES fancy (gold plated? ) nutring kits to my order (a total of 4 nutrings, plus everything to get them mounted).
snipped
View attachment 88950
snipped

Don,
Excellent PIRIP post on your fuel senders. I have a question. Does Vans still supply the standard sender support rings with standard 'through hole" nut plates? See attached photo. This is a "designed in" fuel leak, as the fuel will leak between the threads of the #8 mounting screws & the stock provided nut-plates on the earlier models. Fuel then leaks out under the heads of the #8 mounting screws. Most builders blame the cork sealing gaskets for the access plate leaks and cure the problem by ProSealing the access cover to the inner fuel tank rib. This is a quick, easy cure. However, if you've installed an inverted fuel flop tube, you are supposed to change that hose every 5 years. The ProSeal cure "can" make removal of the access cover difficult or damaging. I was unaware of this issue until my RV guru pointed it out to me. He stated that no certified aircraft use "through hole" nut-plates in this location. They use a special sealed nut-plate [NAS 1473 -A08], which looks similar to an acorn nut with a sealing O-ring at the base.
NAS 1473-A08 Fuel Tank Nut Plates
Another solution is to use #8 pan-head screws which contain a groove & O-ring in the underside of the head, to seal the leak at the joint between the access cover & the screw heads. Be sure to specify Viton O-rings. Another solution is to simply apply the ProSeal under the heads of the access cover mounting screws.

Inner rib with Vans supplied K1000-08 "through" style nut-plates


Your gold anodized ring plates are equivalents to the NAS 1473 nut-plates show above.

 

[RVbySDI]

Even when fuel is flowing out of a tank that lost a cap in flight, your totalizer would show fuel that was not there....

True. I understand where you are coming from. The truth is that no system is 100% full proof. I did say I do have fuel quantity gauges also. My point was that there is a lot of effort with attempts to make fuel quantity sending systems accurate at all quantities when there are better methods for addressing that measurement. As for having a fuel cap missing and fuel flowing out of the tank, I hope my eyesight would still be good enough to look out the window and see the missing cap.

 

[DonMcKee]

Don,
Excellent PIRIP post on your fuel senders.

Thanks!

Does Vans still supply the standard sender support rings with standard 'through hole" nut plates?

Per plans, on RV-14s (and -10s), the inboard fuel sender it mounted directly to the inboard-most rib using 5 "through-hole" nutplates:



The RV-14 plans have you seal the senders from the outside, and instruct that "When finished, there should be a minimum 1/32 [0.7mm] layer of sealant between the rib and the sender" (to allow removal of the sender if ever necessary). I assume one would also seal the fastener heads so they can't leak.

 

[Richard Connell]

Thanks!



Per plans, on RV-14s (and -10s), the inboard fuel sender it mounted directly to the inboard-most rib using 5 "through-hole" nutplates:

View attachment 89326

The RV-14 plans have you seal the senders from the outside, and instruct that "When finished, there should be a minimum 1/32 [0.7mm] layer of sealant between the rib and the sender" (to allow removal of the sender if ever necessary). I assume one would also seal the fastener heads so they can't leak.

Another tip is to seal the sender plate with a 1/16 or a little more of sealant but only tighten the screws to 1/16 or so. Then leave until the sealant has cured somewhat before tightening up the plate fully to the 1/32 as instructed. A form in place sealant gasket.
When installing the screws for the last time use some sealant in the hole and around the head.
Hex cap screws will also make your life a lot easier if you need to remove in the future.

 

[chaskuss]

Thanks!



Per plans, on RV-14s (and -10s), the inboard fuel sender it mounted directly to the inboard-most rib using 5 "through-hole" nutplates:

View attachment 89326

The RV-14 plans have you seal the senders from the outside, and instruct that "When finished, there should be a minimum 1/32 [0.7mm] layer of sealant between the rib and the sender" (to allow removal of the sender if ever necessary). I assume one would also seal the fastener heads so they can't leak.

So Vans is still using standard "through hole" nut plates, but have eliminated the cork gasket and just tell you to ProSeal the sender to the rib. Your very nice gold anodized ring plate does not use through hole nut plates, so no leakage there. So you have to ask yourself, do you want to risk damage to your pricey sending units, by "gluing" them on? Or just make a cork or paper gasket? As long as you ProSealed the ring plates to the inside of the ribs, you can't get a fuel leak there, either.

 

[Richard Connell]

Vans always explicitly said to bin the rubber gasket and proseal the senders to the tank.

 

[DonMcKee]

Vans always explicitly said to bin the rubber gasket and proseal the senders to the tank.

True, but they're also referring to the gaskets included with the kit-supplied, inexpensive, SW automotive senders. According to Daniel, at CiES, they've never had any problems with leaky gaskets on their aviation senders. He said their rubber gaskets are formulated to work on fuel tanks, and will actually absorb a bit of fuel and swell to seal any minute gaps.

As an aside, before I posted, I'd hoped that this thread wouldn't drift towards debating the value of Stewart-Warner vs. CiES senders, or 1 vs. 2 senders per tank, but since it sorta has...

• I decided to go with CiES and pay the premium price for what I perceive to be higher quality, reliability, accuracy, and better technology. As they say, "It only hurts once."
• My budget allows me to (hopefully accurately and reliably) measure the full capacity of my tanks using dual senders, so that's what I decided to to.
• A phrase I learned related to emergency preparedness is "Two is one, and one is none" when it comes to redundant equipment, systems, etc. While it's true that the Red Cube fuel totalizer will accurately measure fuel used (and therefore, fuel remaining), that's only true if it's functioning as designed (and all of the fuel caps are securely in place ). My expectations are that my gauges and totalizer will read essentially the same values, and if they don't, I'll need to investigate.

As was mentioned earlier, "... build what you want ...."