What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Extended range fuel tanks

Vansconvert

Well Known Member
For anyone who has extended range fuel tanks, how are they working out for you? Would you do it again? If they are totally empty, are aerobatics ok?
 
For anyone who has extended range fuel tanks, how are they working out for you? Would you do it again? If they are totally empty, are aerobatics ok?

They are great. Aerobatics are fine with the tanks empty. Since a complete test program has not been accomplished, Hotel/Whiskey does NOT recommend spins.
There is at least one person who unintentionally did an aerobatic routine with the ER tanks full, but I wouldn't count that as a qualifying test.
 
Last edited:
There are a lot of threads on ER tanks. Including many different ways to build them in.

There are wing tips that have been turned into tanks. There are outboard leading edges that have been turned into tanks. There are tanks that slide into the lighting holes in the outboard leading edge. There are tanks that fit behind the seats and can be used for fuel or smoke oil, depending on how it is plumbed.

The challenge is how to you plumb them into your system.

I have seen suction pulling fuel from the outboard tanks into the inboard tanks and the only vent being on the outboard tank.

High and low fuel level indicators built into the tanks that automatically transfers the fuel from the outboard tanks to the inboard tanks as the inboard tanks use fuel.

Manually activated electric fuel pumps to move the fuel when the inboard tanks have enough capacity. (Turning on the pumps too soon results in pumping your fuel out the vent line.)

Another option is to use the standard Van's fuel valve and connecting an extra tank into the unused fitting.

My personal favorite would be to use a five-way Andair fuel valve (Left Outboard - Left Inboard - Off - Right Inboard - Right Outboard) and switch the fuel manually.

Try using the search function, you will find a few days worth of reading.
 
Bigger tanks can affect acro capability; longer tank will allow fuel to move farther outboard.

RE: "Manually activated electric fuel pumps to move the fuel when the inboard tanks have enough capacity. (Turning on the pumps too soon results in pumping your fuel out the vent line.)" : Here's something I never considered, but one of my friends who's a retired research scientist *did* think consider, and tested. If you're pumping fuel into one of the 'main' tanks with standard fuel venting, the real danger isn't pumping fuel overboard; it's over-pressurizing the tank. As long as it's just air exiting the vent, you're fine, but when fuel hits it, pressure can rise to over 5 psi if you're using a high rate pump. The restriction of 5-6 feet of 3/16" line won't flow fuel fast enough to keep pressure from rising.

FWIW, if you wet the leading edges for extra capacity, you can add quite a bit of fuel 10-15 gal/side) for very little hardware weight gain (not much over 1 lb per side).

Charlie
 
SafeAir1

I've got the SafeAir1 tanks in my 6. 4 1/2 gallons per side, gravity feed into main tanks. Great for long cross countries and tanking up on cheap fuel. Problem free for 500 hours.
 
Ditto for my 9A

I've got the SafeAir1 tanks in my 6. 4 1/2 gallons per side, gravity feed into main tanks. Great for long cross countries and tanking up on cheap fuel. Problem free for 500 hours.

They work great after 1 year, although I only have 125hrs on my 9A. My Aux tanks have a small electric pump for each wing which I can activate as capacity in the main tank allows. I have small switches located near the main fuel selector valve with LED indicator bulbs to remind me when activated. Each Aux tank pump takes 16 minutes to transfer to the main tank.
 
Last edited:
Procedure for fuel transfer with HW Aviation ER tanks

RE: "Manually activated electric fuel pumps to move the fuel when the inboard tanks have enough capacity. (Turning on the pumps too soon results in pumping your fuel out the vent line.)" : Here's something I never considered, but one of my friends who's a retired research scientist *did* think consider, and tested. If you're pumping fuel into one of the 'main' tanks with standard fuel venting, the real danger isn't pumping fuel overboard; it's over-pressurizing the tank. As long as it's just air exiting the vent, you're fine, but when fuel hits it, pressure can rise to over 5 psi if you're using a high rate pump. The restriction of 5-6 feet of 3/16" line won't flow fuel fast enough to keep pressure from rising.

My procedure is as follows. I start out on the left main. After 5 gallons as shown on fuel totalizer, I switch to right tank. After 5 gallons, I switch back to left tank and turn on transfer pumps. This transfers the 9 gallons from both ER tanks to the mains at the same time, thereby keeping lateral balance consistent.
 
FWIW, if you wet the leading edges for extra capacity, you can add quite a bit of fuel 10-15 gal/side) for very little hardware weight gain (not much over 1 lb per side).

Charlie

For the 9A wing, I did exactly that and gained 15.5 gallons per side, at a dry-weight-added cost of 17 pounds total, including transfer pumps, plumbing and wiring. I did the Tuckey-style tank mod with flow-through venting. I removed 5 structural ribs and installed 7 fuel ribs, added the rear baffle, and then the senders and fuel caps, plus transfer pumps and an access panel on each wing to get to them. I almost doubled my fuel capacity for only 17 pounds dry weight added - I thought that was a very good tradeoff.

For the connection between the inboard and outboard, I have dual parallel paths from the sump of the outboard to the top vent position on the inboard. One is a straight flowthrough and the other has a Facet low-pressure pump inline. During normal ops the straight flowthrough will draw fuel from the outboard to the inboard as I burn it from the inboard, and in the event my inboard fuel cap develops a leak and doesn't hold the minor vacuum required I can use the Facet to force it across. If the Facet is running while the inboard is full, the fuel will simply return to the outboard via the other straight-through line, no pressurizing the inboard tank.
 
Last edited:
Sounds reasonable to me; the big issue I mentioned was due to the standard vent line being 5-6 feet of -4 line, while the supply was from a high volume pump through a -6 line.
 
1 hour aux tank on right seat

I'm reading all kinds of ideas for permanent aux fuel tanks. In the tips, drop tanks that don't drop, Hotel Whiskey.....

I don't see where anyone removed the right seat, securely mounted a 10-12 gallon bottom feed tank inside the cockpit, connected it to the vans supplied fuel selector and vented it to the exterior. Im considering this and would like to hear comments on this wisdom or lack thereof. An extra hour is all I need. Simple install and removable later.

I want to fly this 21 gallon per side RV7A from NE Ohio to Tampa with one fuel stop and do it COMFORTABLY. I flight plan 10 gallons per hour but believe the burn is less with my YIO-360-M1B. Probably can do it now but both arrivals will not leave any margin for error.

Thanks
Tim
 
Last edited:
Bladder type ferry tank

Tim,

You might look into a bladder-style ferry tank. Turtlepac makes some specifically for small aircraft and there are probably other manufacturers. The smallest one I saw on a recent look at their site was 25 gal but they used to make them as small as ~10 gal. The price is higher than the rigid tank you describe, but the bladder does not need a vent and is designed to be held in place by existing harness.
 
I'm reading all kinds of ideas for permanent aux fuel tanks. In the tips, drop tanks that don't drop, Hotel Whiskey.....

I don't see where anyone removed the right seat, securely mounted a 10-12 gallon bottom feed tank inside the cockpit, connected it to the vans supplied fuel selector and vented it to the exterior. Im considering this and would like to hear comments on this wisdom or lack thereof. An extra hour is all I need. Simple install and removable later.

I want to fly this 21 gallon per side RV7A from NE Ohio to Tampa with one fuel stop and do it COMFORTABLY. I flight plan 10 gallons per hour but believe the burn is less with my YIO-360-M1B. Probably can do it now but both arrivals will not leave any margin for error.

Thanks
Tim

Here you go - 7.5 gallon tanks that can fit behind either seat in the 7/9 and extend about 3" into the baggage compartment. There's 2 hours of range for you without removing the passenger seat.

https://www.smoke-system-helper.com/tanks-only
 
This is a good start and might work....was hoping to do a minimum of 10 gallons and not add to aft CG

Put one behind each seat, that's 15 gallons. I have a pair of them myself, the construction is excellent.
 
This is a good start and might work....was hoping to do a minimum of 10 gallons and not add to aft CG

Originally Posted by airguy View Post
Here you go - 7.5 gallon tanks that can fit behind either seat in the 7/9 and extend about 3" into the baggage compartment. There's 2 hours of range for you without removing the passenger seat.

https://www.smoke-system-helper.com/tanks-only

I put one of those behind the copilot seat. It's worth 7.3 gallons, full to the neck. I tell my totalizer that it is 7 gallons. I have a fuel pump with built in check valve under the floorboard of the baggage which pumps into the left main. I start pumping once I've used 3 or more gallons on the left. Since bladder range is usually my limiting factor, I mostly use it for loading up where the gas is cheap and fill the mains only where it's not such a bargain.

With any kind of tailwind and LOP, 38 gallons is way plenty fuel. ROP into a headwind, more capacity is more better. I probably wouldn't have bothered to install it if I'd had the 42 gallons that newer models have. I just didn't want to be the guy that made everybody stop early.

Ed Holyoke
RV-6
 
Here you go - 7.5 gallon tanks that can fit behind either seat in the 7/9 and extend about 3" into the baggage compartment. There's 2 hours of range for you without removing the passenger seat.

https://www.smoke-system-helper.com/tanks-only

I helped Marvin in the design of the "7.5 gallons" behind the seat tanks. I have two installed in an RV6.

They have been used as separate fuel and smoke oil tanks as well as two (plumbed together) fuel tanks.

The way **I** use them (your mileage may vary) is to plumb them to the "center" position of the standard Van's fuel selector. So I have "Left", "Aux", and "Right" positions.

Startup and takeoff on "Left" tank, fly 15 minutes (which is usually enough to get me to altitude) and then switch to the "Aux" tank. Assuming **ONE** tank, I fly for 45 minutes. At 15 minutes into this tank, I get my 30-minute interval timer saying change tanks. I fly for another 30 minutes and THEN change to "Right" tank. After that, I continue to fly as normal on my standard tanks. SO, this gives me 45 minutes of time, assuming 10 gallons per hour. It makes the RV6 have about 45 gallons and this allows me to travel with RV7's having 42 gallons.

IMPORTANT: Each tank is VENTED to the outside and I have clear tuning on the side of each as a "sight tube".

I have not had any troubles with the tanks.

I may be able to dig up some old photos and video if anyone is interested.
 
interesting stuff here...

James, what is the weight of those 2 7.5G tanks?
How are they secured?
Vented outside, flex line to the bottom or side fuse?
Since I don?t have a spare port on my fuel selector, the plan is to T into the line from the right Wing tank. Gravity + suction should alleviate the need for an additional pump?

Thanks
 
interesting stuff here...

James, what is the weight of those 2 7.5G tanks?
How are they secured?
Vented outside, flex line to the bottom or side fuse?
Since I don?t have a spare port on my fuel selector, the plan is to T into the line from the right Wing tank. Gravity + suction should alleviate the need for an additional pump?

Thanks

Think about that one before you do it. Much of the capacity of the tank is going to be higher than the wing tank. You might vent some of it overboard. I mounted a Facet pump with a built in check valve under the floorboard of the baggage compartment. The pump prevents flow either direction when not in use. I make sure that I've used enough fuel out of the tank I'm pumping into before I start the transfer.

I teed my vent into that of one of the mains and haven't had any problems with that.

The tank comes with tabs welded on that will attach to the seat belt anchors. There is another tab at the top that attaches to the seat back cross brace. It's pretty rigid.

Ed Holyoke
 
interesting stuff here...

James, what is the weight of those 2 7.5G tanks?
How are they secured?
Vented outside, flex line to the bottom or side fuse?
Since I don?t have a spare port on my fuel selector, the plan is to T into the line from the right Wing tank. Gravity + suction should alleviate the need for an additional pump?

Thanks

What fuel selector do you have?
I would not merge with another tank.

I vent via INDIVIDUAL LINES to a 90 degree fuel fitting attached to the bottom of the fuselage right near where the flap extension rod enters the fuselage.

I don't recall the weight. I suspect the actual weight is on Marvins web site. This weight is not that far aft CG if you look closely as some of it is just below YOUR BACK.

For more dialog contact me at the gmail place. jclarkmail over there :). Or call me 8 OH 3, 238, 2ll3.
 
Just a thought from a maintenance guy, I have a customer with the behind the seat tanks in his 7. Working in the aft fuselage or under the panel is nearly impossible without removing the tanks which is not a 5 min job.
 
I have an Andair duplex selector, so no way to add a line here... and the reason I will have to Tee into an existing line.
Now whatever system I install will of course have a tap. Once say the right tank would be near empty, I would open said tap to xfer the fuel in that tank, whilst feeding the engine with the other one.
Not sure gravity would suffice for the transfer though...

Intended are a couple of longer flights for which additional capacity would be welcome, but no need for a permanent system.

Side note: usually flying my -6 at about 43% power (19/2000) returns a TAS of 130 kts at a fuel burn of about 5.5 usg. Longest flight to date 5:40 at the end of which I still had 6.5 usg left, indication verified upon subsequent refueling. So my endurance at those settings is almost 7 hours no reserve.
 
I have an Andair duplex selector, so no way to add a line here... and the reason I will have to Tee into an existing line.
Now whatever system I install will of course have a tap. Once say the right tank would be near empty, I would open said tap to xfer the fuel in that tank, whilst feeding the engine with the other one.
Not sure gravity would suffice for the transfer though...

I've got the same setup, what I have in mind is tapping into the return line from the fuel pumps (dual electric with a pressure regulator - excess returns to the tanks) and feeding the ferry into that return line. That way the duplex selector can be used to move the fuel into the wing tank of choice since it's merging with the pump overflow upstream of the duplex.

I'm going to use a Facet fuel pump with check valve for positive stop on flow either way unless it's energized to move the fuel from the ferry tanks to the wings.
 
Smoke system helper tank dual usage?

So from reading here it sounds like there might be a way that I could use my 4.25 gal smoke tank as an occasional fuel tank. I have the Van's fuel valve, so an extra port.

I would love to have that little extra fuel for those 1200 mile trips that usually require two fuel stops. Just wonder if it's a safe install and if it can be easily returned to smoke when needed.

What I've read was dedicated fuel rather than interchangeable to fuel then to smoke.

Cathy
 
So from reading here it sounds like there might be a way that I could use my 4.25 gal smoke tank as an occasional fuel tank. I have the Van's fuel valve, so an extra port.

I would love to have that little extra fuel for those 1200 mile trips that usually require two fuel stops. Just wonder if it's a safe install and if it can be easily returned to smoke when needed.

What I've read was dedicated fuel rather than interchangeable to fuel then to smoke.

Cathy

Howdy Cathy,

I'd be a little nervous about getting a slug of smoke oil in with the gas. Mixed into the fuel in a tank, it would lower the octane rating and possibly cause you detonation. A slug of oil right into the carb or fuel servo might be immediately catastrophic. You would need a positive way to know that the tank and lines were completely flushed out with fuel and the flushed fuel disposed of when you convert the system. Going back to smoke would be easier. You probably wouldn't want to pump a whole lot of fuel right into your pipes, but at least you wouldn't be as worried about failing the engine.

Ed Holyoke
 
Back
Top