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Baggage compartment fuel tanks

captainron

Well Known Member
I saw one RV at LOE that had one but didn't get much information about it. Does anyone have any experience doing this? The baggage area in the -7 measures 36" by 21", and a tank of that dimension and 4" high would hold 13 gallons, or about 3.2 gal. for every inch of height. Seems that even a 3" tall tank wouldn't take up that much room, and would provide an extra hour of fuel.
 
Prolly work just fine except I wouldn't want 13 gallons of fuel in the cockpit with me. Wingtip tanks mo' better.
 
Grumpy,
Even without the extra tanks your 7 should able to fly further than the gas hog you fly now! Put the tip tanks in like Robby has. But I have to say have have thought about a cabin tank for a cross ocean trip.
 
Extra fuel is nice

I returned from John Wayne Airport in Santa Ana, California to Drake Field, Fayetteville, Arkansas today. One stop in Albuquerque, New Mexico for fuel and total flight of time 7 hours 47 minutes. I have two tip tanks totaling 17 extra gallons of fuel. The other concern about the baggage compartment tank is the aft CG location.

Bob Axsom
 
mdredmond said:
Prolly work just fine except I wouldn't want 13 gallons of fuel in the cockpit with me. Wingtip tanks mo' better.
Actually if you talk to the folks at Van's, if you have to do extra tanks, they prefer you do fuselage tanks rather that tip tanks. That extra weight slung out on the wing tips does unpredictable things to spin characteristics. So while making yourself feel better about not having fuel in the passenger compartment, you could spin the plane into the ground. This was in an issue of RVAtor.
 
Well compromise for what you want

If you go by what Van's Aircraft says you are going to have an airplane that Van's Aircraft wants you to have. If you know what you want you have the option of slanting the compromises to suit your preferences.

If you go with the fuselage configuration, Van told me in 1996 he would prefer that you put in a header tank behind the instrument panel. Whatever you do, think out everything, plan it well considering fueling operations, flight operations, maintenance, etc. then if it is still what you want to do, do it. It's your airplane.

Bob Axsom
 
Gas hog?

TSwezey said:
Grumpy,
Even without the extra tanks your 7 should able to fly further than the gas hog you fly now!

GAS HOG!??? Hey, 13 gallons will get me around the pattern once, plus a little bit left over!
 
Vertical

Hi Ron,
Make it narrow but as wide as the baggage area and go vertical to the top of the crossbar. If you build it 6" X 36 X 20 it will yield 2.5 cu ft. Since 1 cu. ft. = 7.48 gals, you have the capacity for over 18 gallons or 108 lbs. I know, I know only 70 lbs is what Van says. Jon Johannson packs 300 lbs of fuel in the back seat of his -4.

Ron, this still leaves room for a small suitcase. I'd fly the airplane with increasing weight back there and find the max you can live with.

Heck, I started my ag career in a factory backpack Super Cub that had a factory installed 80 gallon hopper in the back. I flew it with 60 gallons (500 lbs) back there many times, three full turns of down trim and landed it that way. It's "doable".
Regards,
 
I'm in the later planning stages of building my extra fuel tank for the baggage compartment. Mine transfer (2 tanks) into the left main fuel tank. What exactly is your question? CofG, safety, size, weight, securing, plumbing, venting?

Steve
RV7A
Flying
 
sjhurlbut said:
I'm in the later planning stages of building my extra fuel tank for the baggage compartment. Mine transfer (2 tanks) into the left main fuel tank. What exactly is your question? CofG, safety, size, weight, securing, plumbing, venting?

How about sharing all of the above....
 
I thought a few times that a portable "180 lb" tank, with a desk-type top, that straps onto the passenger seat might be a handy accessory to have on cross country solo flights. It possibly could be sized to store behind the seats when empty and replaced by a passenger. :rolleyes:
 
BillyBob said:
How about sharing all of the above....

I can expand on some. Firstly CofG. The max weight I can have (taking into account my weight and takeoff fuel (43 Gal in main tanks) is 200 lbs. But that value puts me at the far back CofG and during takeoff I burn from the left tank. So in the climb and for the first hour or so, the CofG moves aft and exceeds the rear value. So you need to play with CofG issues. My baggage load is set for 150 lbs. There are other issues as well for myself including the 2nd fuel tank in the passenger seat. Obviously you need to play with CofG and track the change in CofG as the fuel is burnt. The basic method I use is burn 1 hr left tank, transfer that amount of fuel from aux tanks. I then switch to right tank (to ensure continued flow) for 15 min and back to left tank until all aux fuel tanks are empty.

Safety - fuel in cockpit is not great. A risk you need to take depending on your goals and reasons for all the fuel. Keep in mind as well, that gross weight may be exceeded (ferry permits allow this) and landing within the first few hours of takeoff is not a option. At least if your want the gear to stay in place.

Size - Depends on your canopy style. You can't build a tank (36" by 21") to fill the baggage floor. You won't be able to get it in and out. Test with a cardboard tank first. You can get bladder tanks made as well.

Weight - see CofG.

Securing - bolts to bulkhead near flap control tubes as well as into floor ribs. My baggage floors are removable with flat head screws. If you riveted the floor or used dome screws, you need to rethink how to secure the tank.

Plumbing - I have 2 fuel selectors. One normal one (left and right) to feed the engine. The second selector is labelled baggage tank and passenger tank (wife doesn't like that name). The fuel transfers into the left tank only via 5/16 alum line, fuel pump, and check valve.

How do you know how much has been transfered and how much is left in the tank? A few options. You can measure the fuel flow and turn the transfer pump on for a predetermined amount of time. Compare to insitu fuel gauge reading after the transfer. You can plumb a clear fuel line on the outside of the aux tank to see the level of fuel left (same as low cost high wing fuel gauge). I use a combination of timing (fuel flow) and a fuel press gauge. When the tank is empty, the fuel gauge oscillates from 0 to 5 psi. During transfer is about 2 psi. The guage measures "transfer press." not fuel press at engine.

Venting - needs to be obviously. My vent is the same as the main tanks vents. Goes out he bottom (under baggage area) and is cut to face forward. Don't put it right behind one of the exhaust pipes.

Other issues - how to fill the tank? Who wants to hold a big heavy black fuel hose while sitting on the wing? The hose hits the canopy rails, canopy fiberglass, leaves black marks and dirt. Not great. Extend the fill up hole to reach the top of the back of the seats. This is where the clear fuel hose outside is useful so you don't over fill the tank and spill into the cockpit.

I'm in the early stages of finishing and testing mine. You mileage may vary.

Steve
RV7A
 
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cobra said:
I thought a few times that a portable "180 lb" tank, with a desk-type top, that straps onto the passenger seat might be a handy accessory to have on cross country solo flights. It possibly could be sized to store behind the seats when empty and replaced by a passenger. :rolleyes:
This has been my thinking also, as I fly mostly solo and I would like to be able to fly midwest to/from CA with only 1 fuel stop like Bob Axsom. This seems an easier retrofit to a flying side-by-side RV. The extra fuel & tank would appear as a passenger on takeoff. I would use the "center line" tank first, and then go into the normal L-R-L-R... sequence. The tank would be designed so that it is easy in, easy out; vented to the outside.

The one person I remember doing it this was was Manuel Queiroz in an RV-6:
http://www.chasingthemorningsun.com/prep.htm

When I asked Manuel about his seat tank, I think he said that because of the regulations in his country, it had to be designed and tested to 6? Gs.

It would seem that the issues involved in this type tank, if you can accept the extra fuel inside the fuselage, would be what type valve to use for switching tanks ("make before break") and the venting in case of ending upside down ("check valve"?)
 
Extra fuel

Thanks, guys, for all the feedback on this. When you are
just looking at the empty fuselage, you do a lot of wondering, "what if's?".
 
Baggage Tank Kit

There's a gentleman at Winter Haven, FL that used to sell a baggage tank kit. He's got a beautiful RV with one in it. The info he gave me a year or so ago was; 12.5 Gallons Max, $350 plus pump. He plumbed the fuel neck into the pilot side of the fuse. It was a clean looking install. Another benefit I saw was that it brought up the useable bottom of the baggage compartment several inches so it made small things alot easier to access back there. I bet they know him at KGIF. Winter Haven has a fly-in on Nov 11th. Maybe he'll be there.
 
Ron

Thanks for reminding me of my age! My tank is only as good as the Van's tank capacity. As the Van's tank drains mine fills up. So at least for me extra fuel in the wings / right seat / baggage area or any pace else was never a consideration. Now maybe we could work a deal with the Air Force and do some mid air refueling.

Good luck in your build and fly safe.

Frank @ SGU and SLC wiring a 7A ..............................
 
fstringham7a said:
Ron

Thanks for reminding me of my age! My tank is only as good as the Van's tank capacity. As the Van's tank drains mine fills up. So at least for me extra fuel in the wings / right seat / baggage area or any pace else was never a consideration. Now maybe we could work a deal with the Air Force and do some mid air refueling.

But I still have questions..... ;)

In your case (& mine) you use a tank with 2 bladders inside. As one gets used up, you can fill the other one. :)

1. Why are people using pumps to transfer aux. fuel into the main tanks? Why not properly design a right seat tank with sump and pickup tube, out the front to the fuel selector valve. The rough height is about the same as the wing tanks.

2. What are others doing about a low point drain and sumping quick valve?

3. Tank baffling or antislosh foam???
 
Baggage Tank in an RV-10

I have designed a baggage tank for my RV-10 that nestles up against the rear seats under the large lateral cross bar. I am estimating that the triangular shape will yield approximately 12-14 gallons of capacity.

I decided from the outset that I did not want to be filling a fuel tank from within the cabin so I designed a two pump system that will allow me to fill it or alternatively, drain it into the right wing tank. I picked the right wing tank because that is the tank that you select when landing.

I created a cavity beneith the baggage floor that has a false floor upon which I can mount the plumbing and pumps. I wanted to be able to pull the whole affair out should I need to service or modify it.

The tank is designed to fit through the baggage door.The tank extends from the right hand fuselage side wall to just over the center tunnel.

There is a rectangular section welded to the end of the tank which extends down into the cavity through the baggage floor. This section acts as a sump and it has the fuel pickups located about one inch from the bottom. A fuel drain is in the very bottom and it extends out through the bottom skin.

The aux. tank is plumbed directly to the Aux. Fuel tank inlet on my andair fuel valve as well as through the pump circuit that is tee'd into the right wing supply line. I plan to only use the transfer function on the ground.

I decided to put this tank in the baggage area to help with the RV-10's CG issue of running out of elevator trim authority when flying with full tanks and occupants in the front seats only. Many people carry some extra weight in the baggage compartment to compensate for this. I am simply a believer that you can't have enough of either fuel on board or altitude.

If anyone has any question about this installation I would be happy to elaborate.

Dave Hertner
#40164
 
To the point about spin issues with tip tanks, has anyone built extended mains using outer bays in wings?

Extra work, for sure, but this seems like a nice compromise to tip tanks, while eliminating extra plumbing, transfer pumps, etc. Also keeps CG within envelope while keeping gas out of the cockpit.
 
bumblebee said:
To the point about spin issues with tip tanks, has anyone built extended mains using outer bays in wings?

Extra work, for sure, but this seems like a nice compromise to tip tanks, while eliminating extra plumbing, transfer pumps, etc. Also keeps CG within envelope while keeping gas out of the cockpit.
Yes, I believe this has been done successfully by several people. But it would be best done while building the wings. It doesn't seem like a simple & easy retrofit to an already built & flying plane; which is what I think people are looking for in this thread.

Dave Hertner & sjhurlbut, please check PM. Thanks
 
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And on that note - how easy/difficult would it be to add an outboard wing tank (not tip tank, though that would apply also) to a QB wing? I want to use the QB wing, but I also would like to have at least tip tanks, or the factory mains plus aux in the wing.
 
Yes

Michael Stewart, aka "Kahuna" in Atlanta added half of a wing tank to each side of his Super 8. He bought one wing tank skin, cut it in half and extended his tanks two bays, IIRC, and moved the filler cap out to the end to have enough fuel for the 0-540. He also sealed an area behind the spar for a smoke oil tank,
Regards,
 
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