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Extended Range Fuel Tanks for RV-10 & RV-14

Sky Designs

Active Member
Sky Designs is pleased to announce that ER Fuel Tank Kits for RV-10 and RV-14 are now available.

Our ER tanks are the same as "standard" but extend two rib-bays further outboard to allow for approximately two hours greater endurance. They allow (optionally) for a second fuel quantity sender in the outboard-most rib bay of each tank. The design also incorporates a "fill-tab" for partial fueling -or de-fueling if you're a "Scrappy" wannabe - to a known level.

Pricing and other details can be found at https://www.skydesigns.aero/products
 

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Is this sealing up parts of the existing outboard leading edge for fuel, or are you having to build both the longer fuel tank and the, now shorter, OB leading edge?
 
Retrofitting ER Tanks

Retrofitting to a completed and flying airplane - RV-10 or RV-14 it's the same - requires:

Removing your existing tanks

Shortening the outboard leading edge skin - the kit comes with a drill template for accomplishing this task

Drilling holes in the spar web for the (now relocated further outboard) W-1008 splice rib and the two additional T-1012 tank attach zee's - the kit comes with a second drill template for accomplishing this task

Adding the necessary tank attach screw holes outboard of where the old tank ended then installing doublers and nutplates on the spar flanges - the doublers that are supplied in the kit also serve as drill templates

Building a completely new - longer - fuel tank.

On RV-10, the kit comes with a doubler for creating a fourth W-822 access opening cover on the bottom of the wing. On RV-14, the existing three access openings are enough to access all the places you need to go.

As long as the bottom outboard wing skin has not been installed - as is the case with QB wings - the wing modifications are quite simple but once that outboard bottom skin is on, the "fun-factor" goes way down because access to the spar flange - especially the lower flange - becomes limited. In the case of a finished and flying airplane, we suggest using blind rivets rather than solid rivets to attach the nutplates to the spar flanges.
 
There are five RV-10 builders at Synergy Air South all adding Ken’s ER tanks. Some of us are already flying and others are getting ready to build their wings - (Tank parts just arrived from Sky Designs so there will be a couple of retrofits and others will be new builds).

The thing that sold me (aside from the extra fuel capacity) was the designer/engineer of these tanks. Knowing that Ken was involved in the original design of the RV-10 put any of my concerns to rest.

I built my wings and original tanks to accept the Hotel Whiskey tanks, but the quality of those tanks seems to have gone downhill, the plumbing is much more complicated and the additional fuel is outboard near the wingtips.

Ken’s design is (as expected) elegant and simple, plus it doesn’t modify the fuel feed system at all. One fuel filler per tank versus an additional cap in the wingtip for HW. He also modified the stiffeners to accommodate an outboard CiES sensor - so you can have accurate fuel quantity from nearly full to nearly empty.

The parts are well made and Ken’s instructions are incredibly detailed and thorough. Although I’m not excited about a couple of days of fun with pro-seal, I am excited about the additional capability this modification will add to an already very capable airplane.
 
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Me too!

Wish this would have been available several years ago!

I agree, since I'm one of the first retrofits being done. Sure would have been easier to do when we were building the wings and tanks originally.

Either way, Ken's design is top notch and I think will become a very common option on the 10's and 14's. I really don't see a downside, especially on a slow build wing.
 
Yes

I agree. I have the HW er tanks so I won’t retro fit but it would be nice. Also be nice to have the multiple sensors to read actual fuel level!
 
I ordered up a set of ER tanks for my RV-14 as soon as I heard about them. I’m a huge fan of long range flying and can certainly leave fuel behind if the flight calls for that. Ken has been gracious with his time explaining the details to me. As a sucker for mods, I pretty much want whatever Ken is offering.
 
The thing that sold me (aside from the extra fuel capacity) was the designer/engineer of these tanks. Knowing that Ken was involved in the original design of the RV-10 put any of my concerns to rest.

Bingo.

Ken - glad to see you continuing to put high quality parts on the market!
 
Looking for stock tanks

Great idea!

If anyone orders these, I would be interested in your removed standard -10 tanks.

Thanks

-Jeremy
 
I have the tanks you need!

So like Phil, I too enjoy mods and ordered my ER tanks from Ken! I have a set of -14 tanks available for sale now that were built/finished up with Synergy Air South. They have been pressure checked with no issues. Let me know if you’re interested. I can’t wait to get the ER tanks built and added to the wings. FUSE & Finish kits, and a few other parts, are being shipped soon! Can’t wait to do more building!
 
RV-10 Slow Build Tanks

Great idea!

If anyone orders these, I would be interested in your removed standard -10 tanks.

Thanks

-Jeremy

I have a set of slow build tanks that will be removed from our RV-10 when we install the new ER tanks. They have Newton caps (much better than stock), are plumbed for HW tanks and have a return fitting (we have SDS).

We have one small seep at a rivet that will be dealt with once the tanks are removed. I expect there will be much less than 100 hours on these tanks when we replace them.

If you are near the Twin Cities, I can possibly deliver these to you sometime next year.

Email me at krea dot ellis at gmail dot com and we can discuss.
 
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I really like the idea of these on my RV-14A build.

One thing I'm trying to understand is the optional additional fuel sensors. How would those work, i.e. how would you wire those in your EFIS?

Do they replace the inboard sensors, or is there a way to average the two together?

-Dan
 
I really like the idea of these on my RV-14A build.

One thing I'm trying to understand is the optional additional fuel sensors. How would those work, i.e. how would you wire those in your EFIS?

Do they replace the inboard sensors, or is there a way to average the two together?

-Dan

I spoke with Cies at Oshkosh last year. You actually put two sensors in each tank and when wired they act together, accurately reading from 0 to full…
 
The use of a sender in the most outboard rib bay is an option and does not replace the inboard sensor.

Because of wing dihedral, the outboard end of the tank is higher than the inboard end of the tank. This means that the outboard end of the tank may be partially empty while the inboard end of the tank is still full.

With a single (inboard) sensor, the fuel quantity indicator says "full" from the tank being truly full until the fuel level drops to the point that the inboard rib bay is not completely filled and the sensor float comes off the top of the tank. While there is some time when "full" isn't really full there is never a time when "empty" isn't really empty.

The advantage of a second (outboard) sensor is that as soon as the outboard end of the tank empties, the fuel quantity indicator shows a decline. Some pilots like having this advantage whereas other pilots feel it isn't worth the cost, weight, or complexity. That is the beauty of it being an option.

EFIS's are able to use multiple senders. The fuel sender type and wiring configuration will be defined by the installation manual.

There's a nice write-up on this topic in the RV-14 wiki: https://www.dropbox.com/sh/xu5p6f4l...0&preview=RV-14+FUEL+TANK+MOD+VAF+Reduced.pdf
 
Minimum fuel

Regardless of what the fuel gauges say, I always dip each tank with my calibrated stick as part of my preflight inspection. On my RV-7A, the stick will come out dry with 4-5 gallons in the tank. Obviously I fuel up before flying when the level is that low.

Can you tell us how much fuel remains on the -10 extended range tanks before you can 'see' the level with a dipping stick and what the level is when it reaches the fill tab?
 
Tabs & Minimum Fuel

Here is a summary of partial-fuel conditions for both planes:

RV-10ER:
50 gallons total usable when "filled to the tabs"
(25 US gallons (usable) remaining in each tank)

19.6 gallons total usable when the outboard rib bay is empty
(9.8 US gallons (usable) remaining in each tank)

RV-14AER:
40 gallons total usable when "filled to the tabs"
(20 US gallons (usable) remaining in each tank)

11.4 gallons total usable when the outboard rib bay is empty
(5.7 US gallons (usable) remaining in each tank)


RV-14ER:
26 gallons total usable when "filled to the tabs"
(13 US gallons (usable) remaining in each tank)

5.0 gallons total usable when the outboard rib bay is empty
(2.5 US gallons (usable) remaining in each tank)

The ER tanks are the same for both "flavors" of RV-14, the differences between RV-14AER and RV-14ER are a fall-out of the different ground attitude of the tri-gear and taildragger configurations.

I hope y'all find this information useful!
 
Oh, darn it, the last thing I want to do is build a whole new set of tanks, especially since mine have been holding a light pressure without leaking for over two years now, but I may just have to get these!
 
Can you describe the build process for the new tanks? Is it essentially identical to the factory tanks? Are there any jigs or special drilling fixtures required, or are the ribs, skins, and rear baffle plate pre-drilled/punched?
 
Yup, the build process is identical to the factory tanks...no jigs other than those used when building a standard tank. We provide drill templates for locating the tank attach holes in the spar and outboard leading edge skin.

All the holes in the skins, baffle, and ribs are pre-punched.

Just for fun, here is a photo of a partially assembled RV-14ER tank that was taken at a top secret location in the Nevada desert.
 

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Yup, the build process is identical to the factory tanks...no jigs other than those used when building a standard tank. We provide drill templates for locating the tank attach holes in the spar and outboard leading edge skin.

All the holes in the skins, baffle, and ribs are pre-punched.

Just for fun, here is a photo of a partially assembled RV-14ER tank that was taken at a top secret location in the Nevada desert.

Is there any chance you would share the installation instructions so I can familiarize myself with the mods I'd need to make before making a decision?
 
Any chance you’re coming up with -7 and -8 kits next?

Yes Please! While the standard tanks are just adequate for my planned uses, a little extra will be great for those headwind days. I'm contemplating a small fuselage tank, but this is a much cleaner idea.
 
Do these completely replace the parts in the wing kit? Still waiting on my wing kit, and this mod sounds very interested. Was wondering if I would need to delete anything from the kit.
 
Do these completely replace the parts in the wing kit? Still waiting on my wing kit, and this mod sounds very interested. Was wondering if I would need to delete anything from the kit.

The ER fuel tank kit we supply is combined with parts from the kit to allow you to produce the larger capacity fuel tanks.

For a standard-build wing kit you delete the standard tank skins, standard tank baffles, and four outboard leading edge ribs...
and add...
two T-1004-L tank ribs, two T-1004-R tank ribs, one T-1012.

We have prepared lists of deletions and additions for both standard-build wing kits and a QB wing kits for both RV-10 and RV-14. Just contact us and say which airplane you're building and whether your wing is standard build or quick build and we'll send you the list!
 
I will definitely be using these when I build my RV-14A wings.
 
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No Changes to Aerobatic Weight & Load Factor

Aerobatic gross weight & aerobatic load limits remain unchanged with ER tanks whether full, at minimum fuel, or any amount between the two.

The rolling moment of inertia and yawing moment of inertia are necessarily higher with full tanks as opposed to empty tanks - this is true with standard tanks as well as ER tanks.
 
For a A model, the extra fuel will bring CG forward. For a tail dragger, I would imagine that it brings it back.

C/G has nothing to do with landing gear configuration. Extra fuel on a -14/A will move the C/G forward.
 
C/G has nothing to do with landing gear configuration. Extra fuel on a -14/A will move the C/G forward.

I would imagine it would move the CG forward on the -10 which will cause the need for more ballast in the rear single pilot from what I hear now of people having to add weight stock?
 
RV-14 ER W&B

This is an interesting question...at the beginning of the development effort I was worried about it - won't the ER fuel make the loaded airplane nose heavy?

The additional fuel's effect on CG location turned-out to be smaller than I had expected. You can study the attached image if, like me, you're a number-nerd but the quick & dirty summary is as follows:

For RV-14, with a light pilot and max fuel, the difference in CG position between "standard fuel" and "ER fuel" is only .03 inches or 0.1% chord.

For RV-14 ER, loaded to the MTOW of 2050 lb with 100 lb baggage and 67 gallons of gas, the difference in CG position between "standard fuel" and "ER fuel" is .24 inches or 0.5% chord.

In retrospect, it should not have been such a surprise to me that the weight of the ER fuel made such a small difference in CG position - aircraft designers strive to place the fuel as close to the CG as possible. This minimizes the change in CG that necessarily happens as fuel is burned-off. (Duh:rolleyes:)
 

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QB Tanks for Sale

I have a set of QB tanks for sale that were pressure tested from Vans for sale. If I go this route, I’ll have another set of slow build tanks for sale.

Jeff
 
Sky Designs ER tank PIREP

Just thought I would give a report on these if anyone is interested. I had 104 hours in the entire process, 26 of which involved modifying finished (not on the plane or painted) wings. All of Sky Designs components are of excellent quality and the drawings are very clear.
 
Thank you, Wes, for the PIREP. The RV-10ER and RV-14ER kits are maturing nicely and we're getting the (hopefully) final glitches worked-out.

Nice to know how many "Wes-hours" you've invested in the retrofit process...that is a good benchmark number for others to be aware of. It will be fun to see your completed airplane next year at OSH.
 
I do have a couple of questions, can anybody tell me (RV-10):

Which end of the outboard leading edges shortened? If the W-1008 splice rib is relocated, this implies to me that the inboard-most two bays are eliminated, is that correct? Like, where the stall warning is normally installed that I was thinking about removing anyway? ;)

If I'm in a partial state of assembly, one outboard leading edge completed and the other not started. But no tanks started. Assuming a New Build Kit in this case? Of course I'll confirm if I decide to order, but just curious.
 
It is the inboard end of the outboard leading edge that is shortened.

Yes, the inboard two bays are eliminated.

Yes, this means that the place where the stall warning is normally installed is removed. Most folks are installing EFIS systems that give you stall warning via the AoA system so the "flipper-vane" stall warning is redundant. (You can, however, relocate it along with the W-1008 splice rib)

You are in a great place to go with the "New Build" version of our RV-10ER kit.

Please let me know if you have any other questions :cool:
 
Thanks Ken, appreciate the quick response!

I am planning to install an AoA compatible pitot anyway, so was thinking of ultimately removing my stall indicator so that's good news!
 
I too just purchased Ken’s ER tanks for my RV 10. I am at a snafu in decision making between going with the CIES or Stewart warner floats. Either way I am installing two floats per wing but the price difference is substantially different. Anyone have any thoughts to just going with the Vans floats??? Ken told
Me he never had any problems with his. Thoughts
 
I too just purchased Ken’s ER tanks for my RV 10. I am at a snafu in decision making between going with the CIES or Stewart warner floats. Either way I am installing two floats per wing but the price difference is substantially different. Anyone have any thoughts to just going with the Vans floats??? Ken told
Me he never had any problems with his. Thoughts

The SW senders are cheap and reliable. I don't see a reason not to use them.
 
SW are fine

I'm building ER tanks now, and have the SW ones installed and hooked up to my G3X. They have been very accurate and reliable, and from all I've seen as long as you have a good ground they should remain so for many years.

That said, I bought the CIS ones since I hated the idea of changing them out in 15-25 years or so... which is my best guess for their MTBF. With luck I be around and still flying for it to have been my problem.

Derek
 
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I'd be interested in knowing how you would hook up dual SW floats and have them read properly.

Dual CiES senders in each tank of my about to be installed ER tanks.
 
I'd be interested in knowing how you would hook up dual SW floats and have them read properly.
.

Just hook up both outputs, running each thru a series resistor, to the efis input. Modern efis units can be calibrated every few gallons. No need for the system to be linear.
 
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