[Peter M]

Hi there

I've decided to tick off one of the entries on my bucket list later this year and fly from New Zealand to Australia (via Norfolk and Lord Howe Islands). My RV-6 (with 180Hp Mattituck O-360) has sufficient endurance with a brisk tail wind or no wind to fly the three sectors that range from 320 - 485nm. However, there's not enough safe endurance for my liking particularly if I strike head winds that prove stronger than forecast.

For flight planning purposes I use 35 litres/hr; my actual usage over the life of the aircraft is 31 litres/hour; I can get it down to 28 litres/hr when cruising at 6000 - 8000'. To provide me with an additional hour of fuel I plan to install a 40 litre Little Buddy portable fuel bladder from Turtlepac (see http://www.turtlepac.com/en/products/bush-plane-long-range-fuel-bladder.html). My plan is this:

The Little Buddy will be strapped to the passenger seat. It's designed to take up the shape of the seat with the fuel outlet positioned at the lowest point where the seat cushion meets the backrest.

The fuel hose will be connected to the centre mounted fuel selector via a fuel tap and drip-less fuel connector. This will allow me to remove the Little Buddy for re-fueling and when not in use.

My fuel selector has Off, Left, Right and an empty position at 6 o'clock. The empty position appears to be serviced by a port that's not connected. The Little Buddy will be connected to that. I presume the fuel selector was Vans supplied (I didn't build my aircraft).

I don't see the need for a fuel pump. As the seat is higher than the main tanks I believe fuel will be gravity fed and the engine pump and auxiliary electric fuel pump will be able to source fuel from the Little Buddy.

Takeoff and landing will be performed using a main tank. The Little Buddy will be used in cruise and when there's sufficient height to completely drain the bladder and let the engine stop.

How does this plan sound? Has anyone had experience with a similar fuel arrangement? Please let me know if I haven't thought of anything as I appreciate any advice on this important consideration for my trip.

 

[rv7boy]

My only comment is make sufficient runs over dry ground to make sure it (and you) work properly before heading out over the water with it. I'm remembering Lindbergh had the luxury of a trip across the USA to sort things out before he headed off to Paris. Of course you don't have as many valves as he did!

Good luck!

 

[Captain Avgas]

I don't see the need for a fuel pump. As the seat is higher than the main tanks I believe fuel will be gravity fed and the engine pump and auxiliary electric fuel pump will be able to source fuel from the Little Buddy.

I don't think that the fuel from the ferry tank will be gravity fed (at least not all of it) but I don't think that really matters. The engine driven fuel pump can suck fuel up from the fuel tanks so it will be able to do the same from the ferry tank.

I believe it is standard practice in the certificated world that the ferry tank fuel is pumped into an aircraft tank (hence the little 12 volt fuel pump). That is the safest option but of course it requires special plumbing. Pumping it into an aircraft tank means you can use all of the fuel in the ferry tank without having your engine quit. I think you might find that Turtle Pac will advise you strongly to pump the fuel to an aircraft tank rather than just source it to the fuel selector. I recommend you ring them and talk to them about the pros and cons of both options. It's an interesting topic so if you speak with Turtle Pak you might like to report back to this thread on what they say so that others may be better informed also.

However if you opt to pipe it straight to the selector you will not be the first in the Experimental category to do so. But in that case you would certainly want to test it out a couple of times over dry land as Don Hull has recommended before you ventured out into the Tasman.

If there wasn't a massive difference in price, I think I might also be tempted to go for the Turtle Pac Big Buddy (2 hours fuel) rather than the Little Buddy (1 hour fuel). In a tight spot it might be better to have a big buddie rather than a little buddie.

There's a whole lot of water out there in the Tasman Sea and lots of things can go wrong including erroneous weather forecasting. You may remember the Pel-Air Westwind ditching with 6 on board that occurred off Norfolk Island in 2009 when they couldn't land due to bad weather. Extra fuel gives you more options.

I've done numerous over water crossings in light singles (but not as big a pond as the Tasman). I swear that as soon as I get to the point where I can no longer see land behind me or in front of me the engine always sounds like it's running rougher.

 

[bkthomps]

turtle buddy = $1800-2000

ATL Fuel Cell = $300

I never understood the increased price justification so i got the ATL fuel cell

 

[Peter M]

Bob

Thanks for your thoughts.

Yes - TurtlePac warn that the engine should not be fed direct from the Little Buddy but I don't really understand why. They claim there is a risk to the engine fuel pump if the bladder is exhausted. Neither I nor my engineer can understand why. Perhaps its because there is no air in the bladder and it's designed to collapse as fuel is drawn. When all fuel is exhausted I guess the pump could begin to try and suck a void. However my engineer tells me that my fuel pump is a conventional "click/clack" style which is not likely to be damaged by such an event.

My preference is to avoid any modification to the existing fuel lines and to keep the installation tidy. Installing a pump and running lines through the vent or fuselage side to top-up a main tank is not preferred if it can be avoided.

I'd really like to hear from someone who has drawn directly from a ferry tank in the manner I've suggested and what their experience of that was.

I had considered the Big Buddy but I'm worried that it may interfere with the control stick movement.

Thanks for your interest in my plans

 

[rmartingt]

Another option to look at would be the Hotel Whiskey tanks that fit in the lightening holes in the wings; I think they cost about the same as your turtle buddy. I believe they hold about 4.5gal per side, so a total of about 34L. And you can leave them in and not have to take up a passenger seat. That's probably what I would go with if I were retrofitting instead of building extra fuel in from the start.

 

[Captain Avgas]

Another option to look at would be the Hotel Whiskey tanks that fit in the lightening holes in the wings; I think they cost about the same as your turtle buddy. I believe they hold about 4.5gal per side, so a total of about 34L. And you can leave them in and not have to take up a passenger seat. That's probably what I would go with if I were retrofitting instead of building extra fuel in from the start.

The OP says in his orginal post that he did not build his RV6 so I'm guessing that he is reluctant to want to embark on build modifications.

 

[Mark Albery]

I had considered a similar set up when I flew US to UK, but ended up using a polyethylene motor racing tank from Summit Racing. There are lots of sizes and shapes to choose from.

Apart from the cost saving, I didn't like the idea of feeding straight from a bladder to the fuel valve and pump. The normal method with a bladder tank is to transfer to a depleted fuel tank.

You do have to consider venting with a rigid tank, but that's not too difficult.

That spare port in the Van's fuel valve proved very useful. You just need to mark the tank pointer with an 'aux' position.

If you use it in cruise you can run the tank dry and don't really need a quantity gauge.

 

[Vlad]

I had considered a similar set up when I flew US to UK, but ended up using a polyethylene motor racing tank from Summit Racing. There are lots of sizes and shapes to choose from.



....

Can you expand on this Mark?

 

[Captain Avgas]

Bob

I'd really like to hear from someone who has drawn directly from a ferry tank in the manner I've suggested and what their experience of that was.

I believe that Jon Johanson ferried an RV6 from the US back to Australia with a collapsible ferry tank in the right seat. He simply piped it to the vacant port of a standard Vans fuel selector.

He can be contacted at: http://www.flymore.com.au/about.html

Or email him at: [email protected]

But bear in mind that sometimes you have to wait a bit for a reply.

As for using the Big Buddie, maybe it would fit if you disconnected the passenger joystick. It is removable.

Interesting comment from Turtlepac about concerns with the standard mechanical fuel pump sucking on a vacuum. Of course one has to be extra cautious with any modifications to a proven fuel supply system. Fuel systems are not an area that lend themselves to "intuitive" changes. You are wise to be researching this before proceeding.

 

[Mark Albery]

Can you expand on this Mark?

It was the one you can see in the back of this picture. A 10 gall circle racing tank. I made tie-down straps and put it in the front locker which had bracing for a smoke tank. It was the biggest that could fit in the locker and I had to remove the filler neck to slide it in place and re-fit it once in position. They come with -8 fittings, so you need to reduce to -6 to match the RV.

Venting was through the fire wall and exited in the scroll in front of the cowl exit ramp where there was warmth and protection to prevent the vent tube from icing (I was flying down to -20 C). The fuel pick-up tube fed a braided hose through the floor of the locker and into the spare port on the fuel valve.
The AFP pump has enough dry lifting capacity to prime the system, but to make sure that the supply was continuous when switching to the auxiliary tank I primed and started on that tank and then switched to the mains for taxy and take-off. I earthed the filler neck to the airframe, though I doubt that it had much effect in dissipating static on top of the fuel. The two 5 gallon jugs you can see were used for tankering emergency fuel in case of diversion. They strapped into the back seat harness.
Total cost of tank, hose, fittings etc was about $300.

 

[KRviator]

Perhaps the only issue - and I'm not even sure it is an issue - may be if you run the bladder tank completely dry.

Sure the engine will stop, but your fuel pump will then create a vacuum. Under normal circumstances, they're not operating in such an environment, and being (I believe) positive displacement pumps, continue to push air through the system until fuel replaces it. To counter this, I would recommend that you keep perhaps a litre or two in the bladder and switch back to your main tank. A litre should be easy to judge with such a small bladder, either by stopwatch, or by feel.

I am looking at a near-identical set-up for my soon-to-fly -9A, using a Turtle-Pac bladder and the spare port on my Vans fuel selector, to give me the legs to get to New Zealand, so it will be interesting to follow your progress.

 

[Larco]

I actually did this with the RV-6 we had. I had a poly fuel tank that I would put in the baggage area and plumbed it with a flexable line to the front port of the Vans fuel valve and installed a tee in the vertical tube of the main fuel tank vent inside the plane. I would take off on one of the mains and once airborne switch to the AUX tank and run on it for a predetermined time, then back to the mains. It worked very well and was easy to remove when not needed. I would use AN caps on the open fittings when the tank was out of the plane. I ran it out of fuel once, (I forgot to switch), the engine did quit but started to run immediately when the selector was moved to one of the mains. On longer trips it always removed the Pucker factor.

Good luck on a neat adventure. Larry

 

[PIN 37]

If the manufacturer of the Turtle buddy says dont run the fuel straight into the engine because of the risk to the engine driven pump, then I just cannot understand why you would even contemplate doing this. It would seem to me that the manufacturer knows about his product, anything else is guesswork and dangerous. (IMHO)

 

[jthocker]

I actually did this with the RV-6 we had. I had a poly fuel tank that I would put in the baggage area and plumbed it with a flexable line to the front port of the Vans fuel valve and installed a tee in the vertical tube of the main fuel tank vent inside the plane. I would take off on one of the mains and once airborne switch to the AUX tank and run on it for a predetermined time, then back to the mains. It worked very well and was easy to remove when not needed. I would use AN caps on the open fittings when the tank was out of the plane. I ran it out of fuel once, (I forgot to switch), the engine did quit but started to run immediately when the selector was moved to one of the mains. On longer trips it always removed the Pucker factor.

Good luck on a neat adventure. Larry

We have adapted a few 16 gal circle track tanks into some of our Teams RV8's.
Strapped into the rear seat and baggage area and with very expensive DriFit quick change fittings. They have worked very well, actually tested them over the airport and let the engine quit to see if it would re start when switched back to normal tank. It did! When the tank gets down to the last 2 gallons the fuel pressure and fuel flow starts fluctuating wildly, but the engine continues to run smoothly. When I get a STEADY low fuel pressure I keep my hand on the selector, when it reaches zero I switch tanks. The engine never stumbles.
Works for a lot of us.

 

[RickWoodall]

How to carry more fuel on rare occassions.

This thread has me thinking. When wx suits and winds allow, I have often thought of trying an epic cross country. I have flown 4 hours before between stops...that is plenty 99% of the time. BUT, I would be interested in pics and thoughts on easiest way to rig a tank from the passenger seat or baggage area to pump back into a wing tank. Summit tanks etc seem nice and reasonable price. I have lots of left over fuel fittings and getting a few braided hoses isn't a big deal...just trying to think the plumbing and safety stuff out. 5-8 gallons would be the goal. Show us what you did!

An 8 gallon portable tank with flex lines rigged to drop in for occasional use would be pretty sweet and a fun little winter project!

 

[N941WR]

For a side-by-side RV, I would look at this setup:http://www.smoke-system-helper.com/.

You can add extra fuel (7.5 gallons per tank and you can install two) without adding an extra pump and if you have the Van's fuel value then the plumbing is easy. You will have to add an external vent. (I have an Andair fuel valve and will have to change it when/if I buy two of their tanks.)

James Clark (jclark on this forum) helped sort the tanks out and runs one for fuel and one for smoke oil.

 

[jclark]

More on side by side cabin AUX tanks ...

For a side-by-side RV, I would look at this setup:http://www.smoke-system-helper.com/.

You can add extra fuel (7.5 gallons per tank and you can install two) without adding an extra pump and if you have the Van's fuel value then the plumbing is easy. You will have to add an external vent. (I have an Andair fuel valve and will have to change it when/if I buy two of their tanks.)

James Clark (jclark on this forum) helped sort the tanks out and runs one for fuel and one for smoke oil.

True that!!!

There is a link to pictures from me (and another another installer as well) in a thread elsewhere about extended range tanks for side by side RV's.

I initially did a 10 gallon tank that I placed in the passenger seat. But that would not allow for a passenger on a long trip so I looked for an alternative. The options mention by John Thocker were not as nice for the side by side.

Working with Marvin of http://www.smoke-system-helper.com/ we came up with a tank that is 7.5 gallons - 28.39 liters, (7 gallons useable - 26.5 liters) and fits behind the seat back. It intrudes in the baggage area bout 3 inches. As mentioned I have two and they work fine.

In my case, my operational mode is:

Take off and fly 15 minutes on WING tank of choice
Switch to AUX tank and fly for 45 minute (about 7 gallons the way I fly)
Switch to other wing tank and continue my "change tanks every 30 minutes routine".

I use the Van's supplied 4 port fuel selector as that was what we already had in the plane and it was going to be more work in my case to replace with the 4-port Andair (which I prefer). The AUX position is in the CENTER.

I can couple the two tanks for a total of 15 (14 usable).
Both tanks are VENTED.

If the tanks get below 7 gallons the fuel pressure goes DOWN (cavitation).

I have a "sight tube" on the side of each one.

Feel free to ask me questions.

James