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4 tanks 84 gal of fuel on RV-7

Not long enough though.......

.......because even at 7 GPH, that's only 12 hours. Jon Johannsen has 18 hours of fuel in his 150 HP -4:eek: 300 lbs of that is in the back seat! He's now made three trips around the world and ferried a -7 from Osh to Sidney with a tank in the passenger seat!

His story is on Vans webb site. I also have his book.

Regards,
 
Not on a RV-7

I'm going to start the never ending debate of the RV-7/8 wing not being as strong as the RV-6 wing. We already know of the RV-8 wing failure early on in RV-8's. I know Van has gone back and beefed them up a bit in some key areas. Putting that much weight on the end of the wing (moment arm) with that short stubby box spar in my opinion is asking for trouble. I'm sure there is some engineer out there that can throw some numbers out at us but common sense tells us you're stretching it when you do something like that. I am putting 47 gallon tanks in my RV-6. That will extending the tank over one bay (11") into the leading edge skin. I am going to .032 leading skins and one piece top skins. I will be also going to one piece bottom skins as well. There will be strengthing is the spar area with some more stiffeners and ribs to boot. Unless this guy has but some different flange strips on the back side of the spar web I would think that hanging all that weight out there would be overstressing the outer portion of the wing. I know that weight out there would counter the bending moment of the airplane flying to a certain degree but not cancel it out. Just my 2 cents.
 
Pierre
"Jon Johannsen has 18 hours of fuel in his 150 HP -4 "
I understand he has further modified the RV4 to a wet wing with 1000litres = over 30hours endurance
John
 
Aden Rich said:
I'm going to start the never ending debate of the RV-7/8 wing not being as strong as the RV-6 wing. We already know of the RV-8 wing failure early on in RV-8's. I know Van has gone back and beefed them up a bit in some key areas. Putting that much weight on the end of the wing (moment arm) with that short stubby box spar in my opinion is asking for trouble. I'm sure there is some engineer out there that can throw some numbers out at us but common sense tells us you're stretching it when you do something like that. I am putting 47 gallon tanks in my RV-6. That will extending the tank over one bay (11") into the leading edge skin. I am going to .032 leading skins and one piece top skins. I will be also going to one piece bottom skins as well. There will be strengthing is the spar area with some more stiffeners and ribs to boot. Unless this guy has but some different flange strips on the back side of the spar web I would think that hanging all that weight out there would be overstressing the outer portion of the wing. I know that weight out there would counter the bending moment of the airplane flying to a certain degree but not cancel it out. Just my 2 cents.
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I'll make the assumption, that it's like the "around the world -- Voyager"; where the wing tips scraped the ground on the takeoff roll due to the heavy fuel weight. But once lift takes over, it's the wings supporting the fuse.

L.Adamson --- RV6A
 
I emailed the owner of the around the world RV..he said that he didn't make any mods to the spar..his response email..

We didn?t change the wing spar. The weak point is the connection to the middle part of the spar. You should not land with full tanks, or take-off on rough runways. On long legs, we burn off at first the outer tanks. 1 or 2 Gal remaining in the outer tank will not have a big impact. You can?t feel any difference.
 
WING TANKS

There are numerous examples of tip tanks and extra wing tanks for certified aircraft. Using the Piper Twin Commanche as an example the standard tip tanks are 30 gallons total. The gross weight with tip tank fuel is increased by 225#. There is no modification to the structure. Some Twin Commanches also have 20 gallons in nacelles in addition to the standard and tip tanks for a total of 140 gallons vs 90 gallons stock. Single Commanche also uses same tip tanks.
 
Nick said:
I've thought many times about doing something very similar. The only thing I dont' like about Pats setup is using the stock PP Skins. The double rows of rivets don't sit well with me.
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Call John Harmon (661-836-1028) and he'll roll you some 0.032 leading edge skins. Just let him know how long you want them.
 
Would it be possible to have Harmon roll the .032 skin 1 or 2 ribs longer, thus increasing the fuel to about 55 or 60 gals total...? This seems doable, plus you would save the time of building 4 separate tanks..and I can't think of when I might xcountry far enough to need 84 gals..but 60 or 65 would be nice and needed..
 
Yep....

....it's the solution most of the guys use when they build Rockets and Super 8's and -6's with the 0-540 engines...around 54 gallons IIRC.

Regards,
 
"Standard" HR2 tanks are 21 gallons each, though a lot of guys go a bay or two longer (approx 4 gallons per bay). The skins for the "standard" HR2 tanks are 55", including overhangs and trim allowances. Call John to see how wide of a tank skin he can roll.
 
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With the extended tank skins from Harmon I guess you would also need a longer tank spar and extra Z brackets...what else?
 
A suggestion...

Be sure to scrounge up a ride in an RV going cross country with 4 hour legs planned before deciding on the "long range" option. My longest was about 4.25 hours, and I was ready to get out. And, I followed that by another similar leg right after refueling. Some don't mind it, but it is might be best to try it before adding the complexity.
 
Just 84 gallons?

120.jpg


This RV-6, that was owned by Jeff Nielsen at the time I took the photo, can carry 120 gallons of fuel. Turbocharged O-320. Jeff has operated the airplane as high as 28,000 feet. More than 24 hours endurance, with reserves.

This is an experimental!
 
Stock 42 is plenty for me.

With my factory tanks I've got close to 5 hours duration when leaned properly. My bladder, on the otherhand, is ~3 hours, and by then, I'm ready for a short break. Don't plan on any 'round the world flights, so I'm happy with what I've got. With an empty weight of about 1050 that leaves me with more than enough remaining payload for two adults and a fully loaded baggage compartment.
 
Before you guys get TOO far into you 84 gallon tanks, you might want to talk with your inspector/DAR. Most inspectors are going to want to see some engineering data before they sign off on something that far out.
 
Why?

Mel said:
Before you guys get TOO far into you 84 gallon tanks, you might want to talk with your inspector/DAR. Most inspectors are going to want to see some engineering data before they sign off on something that far out.
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Mel,

Is it the responsibility of the DAR to to validate the airworthiness of the design?

I read this at the EAA site:
http://members.eaa.org/blaa-blaa-blaa

Asking for "engineering data" before signing of an experimental seems to be outside the scope of inspecting construction. What about one-off designs? Is the DAR now taking responsibility for the design of the airplane?

This is counter intuitive to me. FAA "approval" of kits is not a validation of the airworthiness of the design, it is a pre-approval that building it will conform to the 51% rule. Therefore, deviating from it with custom designed features is going to make the 51% go up, not down.

My understanding is that an RV7, for example, is not recognized by the FAA as an airworthy design. It is validation of construction and the testing performed by the pilot which allow it to be declared airworthy. I think by the pilot.

It seems the questions & inspection should be about construction, not design.

I'm not saying that good advice should be ignored, but I'm struggling with my understanding of this.
 
To a point, you are correct. However the inspector/DAR is signing off that the aircraft is "in a condition for safe operation." If he/she thinks that your modifications or designs are not safe, he/she may deny your application.
 
Hawkeye,

You mention what is often mentioned in articles about various airplanes, and it bugs the heck out of me. What does your bladder duration have to do with how much gas capacity your airplane should have? Nothing, in my opinion.

Do you buy gas for your car every time you need to pee?

I like airplanes with large fuel capacities. it provides more range if desired, allows you to buy fuel at places where the price is more favorable, provides better IFR planning options, allows you to fly off somewhere for the day and return without having to refuel, etc.

Let's all stop referencing the bladder situation, please!
 
pvans said:
Hawkeye,

You mention what is often mentioned in articles about various airplanes, and it bugs the heck out of me. What does your bladder duration have to do with how much gas capacity your airplane should have? Nothing, in my opinion.

Do you buy gas for your car every time you need to pee?

I like airplanes with large fuel capacities. it provides more range if desired, allows you to buy fuel at places where the price is more favorable, provides better IFR planning options, allows you to fly off somewhere for the day and return without having to refuel, etc.

Let's all stop referencing the bladder situation, please!
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Thank you - that's been bugging me for a long time. People have gotten in the mindset that you always take off with full fuel, and burn it all on that trip, so if you carry 7 hours of fuel it will be 7 hours before you can find a toilet. BS. We don't fly part 135 scheduled ops in our RV's - we can make a stop anytime (and nearly anywhere) to take care of "business". Aside from making very long legs on transoceanic flights, fuel is a completely separate consideration from biological needs.

If you decide to go flying at 9AM on a Saturday when the weather is just too beautiful not to, and you've already had 2 cups of coffee that morning, you know good and well that your bladder range is about 45 minutes - but you don't take off with only 7 gallons of fuel, do you?
 
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airguy said:
Thank you - that's been bugging me for a long time. People have gotten in the mindset that you always take off with full fuel, and burn it all on that trip, so if you carry 7 hours of fuel it will be 7 hours before you can find a toilet. BS. We don't fly part 135 scheduled ops in our RV's - we can make a stop anytime (and nearly anywhere) to take care of "business"...
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Maybe I'm wrong, but I thought the point being made was that you don't have to stop to pee. How do you think the glider folks make those 12 endurance flights? I can tell you that they don't stop when they need to pee.
 
n5lp said:
Maybe I'm wrong, but I thought the point being made was that you don't have to stop to pee. How do you think the glider folks make those 12 endurance flights? I can tell you that they don't stop when they need to pee.
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I didn't look at it from that perspective, but you're equally correct. Either way, it simply reinforces my point (and pvans) that bladder range and fuel range are separate considerations and need not be tied together.
 
OK, now that we all agree about landing and buying gas, let's get to the more important challenges. We need to find a way to accomplish aerial refueling, and I do not mean hoisting buckets or jerry cans on a rope from a truck.
 
Not much mention of other tanks, is a removable aux tank behind the seats going to affect cg to much? seems like that would be easier for the relatively few flights that needed extra fuel.
 
n5lp said:
120.jpg


This RV-6, that was owned by Jeff Nielsen at the time I took the photo, can carry 120 gallons of fuel. Turbocharged O-320. Jeff has operated the airplane as high as 28,000 feet. More than 24 hours endurance, with reserves.

This is an experimental!
Click to expand...

Isn't Jeff's plane neat? But he can only put 96 gallons in his wings (two tanks per side). The rest he gets from another tank or tanks in the luggage compartment I believe; I have never seen it in that configuration.

You know in the wing is the best place to carry fuel, it doesn't increase structure load at all while flying, but landing, that is another story. Better burn off a lot of fuel first! Jeff told me that his heaviest takeoff was 2200 pounds gross.

Hans
 
The Doc is right.......

....in that the structure isn't burdened in flight, only landing. At a Cessna dealers' convention in Wichita one year, an aeronautical engineer mentioned the Cessna 310 and other wingtip fuel tank types....it makes them stronger. When you load the fuel outboard, it puts a downward moment on the spar, actually helping it to not bend upward and they can build a lighter spar, he said...makes good sense. Just watch landing with full tips.

Regards,
 
miyu1975 said:
With the extended tank skins from Harmon I guess you would also need a longer tank spar and extra Z brackets...what else?
Click to expand...

John can bend up the tank baffles for you too. If you're doing a -4, or -6 you'll need to extend the the spar stiffeners and tank attach doublers.

AlexPeterson said:
Be sure to scrounge up a ride in an RV going cross country with 4 hour legs planned before deciding on the "long range" option. My longest was about 4.25 hours, and I was ready to get out. And, I followed that by another similar leg right after refueling. Some don't mind it, but it is might be best to try it before adding the complexity.
Click to expand...

If you're doing the fuel mod for actual extended range as opposed to just increasing your refueling options, you need to seriously consider as comfortable a seat as you can afford. I once flew an RV-6 with simple upholstered foam rubber cushions, and I was ready to stop after 30 minutes. I've also sat in well-designed automotive seats for six hours at a stretch without problems. I beleive it can be (has been) done for RV's too.
 
I am building a -7, and will call Harmon tomorrow to find out about rolling me a bit longer tank skins and the spar to go with it. My obj is make the 21 gal tanks 30 gals. I am going to be ordering my wings this week from Vans so this is the perfect time to find out what I need to do. If Harmon can roll the skins for me then I guess I can delete that from the wing order with Vans.??
 
found this on "The List" on vans website..Maybe vans already larger tanks?...anyone looked into this before?

T-401PP-L-OVSZ OVERSIZE FUEL TANK $102.60
I can't tell if this for an RV7 or what though..
 
For those that are planning marathon flights, keep this in mind. A DVT (deep vein thrombosis), aka blood clot, has been associated with fliers. And last time I checked, my 7A wasn't exactly cavernous but did have more leg room. People who fly four hours or more have three times the risk of developing blood clots compared to periods when they did not travel. The longer the flight, the higher the risk.

If you develop a DVT, you will require complete anticogulation to dissolve the clot and treatment isn't for just a few days. Just ask one of my good friends who is a pilot - I had to work with him on his treatment.

Left untreated, the DVT can dislodge and travel to the lungs causing a PE (pulmonary embolism) which can be fatal.

Best prevention, fly for several hours, land, get out, and walk around. Ambulation is one of the best means of prevention (walking around).

Bottom line, no matter what the length of the trip, plan legs accordingly...your health may depend on it.
 
Webb said:
Best prevention, fly for several hours, land, get out, and walk around. Ambulation is one of the best means of prevention (walking around).

Bottom line, no matter what the length of the trip, plan legs accordingly...your health may depend on it.
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Or you could get a G suit and do some high G maneuvers every few minutes, or do some negative G maneuvers, or fly upside down. :D
 
miyu1975 said:
I am building a -7, and will call Harmon tomorrow to find out about rolling me a bit longer tank skins and the spar to go with it. My obj is make the 21 gal tanks 30 gals. I am going to be ordering my wings this week from Vans so this is the perfect time to find out what I need to do. If Harmon can roll the skins for me then I guess I can delete that from the wing order with Vans.??
Click to expand...

That's one way to do it, I opted to convert the outboard leading edges into auxiliary fuel tanks, they will add 15.9 gallons each for a total fuel capacity of 67.8 gallons.
 
nucleus said:
You know in the wing is the best place to carry fuel, it doesn't increase structure load at all while flying, but landing, that is another story.
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This statement entirely ignores inertial loads, which CAN be significant with that much fuel in the wings. Also doesn't speak to changes in dynamic maneuvering flight, which probably will be significant.

Any rolling or yawing rotational acceleration induces inertial loads in the wing, which any competent aero engineer would analyze. These loads are then combined with the straight aerodynamic loads (mentioned in the quote above for steady state flight) and the resultant NET loads are then used for structural design criteria.

Also (yes there's more): increasing mass about the vertical and longitudinal axes of the airplane will greatly affect dynamic stability in rolling and/or yawing maneuvers. How much will spin dynamics be affected? How about turbulence or gust encounters? Ground handling? Landing gear loads (mentioned already)? Braking loads (if operating significantly over gross)?

I just want readers here to think about the unintended impact of making large modifications like this. A Wi-Fi connection + Google is no substitute for competent engineering analysis. Aero engineering IS NOT always a "steady state" type of analysis environment. These large "TLAR" transgressions from professionally engineered systems worry me! :eek:
 
Say Bill,

.....wasn't the little Grumman American placarded against spins because the rotation would send the fuel to the wingtips in that round spar/fuel tank?...making spin recovery difficult, if not impossible.

Regards,
 
pierre smith said:
.....wasn't the little Grumman American placarded against spins because the rotation would send the fuel to the wingtips in that round spar/fuel tank?...making spin recovery difficult, if not impossible.

Regards,
Click to expand...

That's why for extra range on an RV, it's better to add separate outboard tanks, (whether it be SafAir, tip tanks, leading edge mod, etc.) rather than extend the main tank the full length of the wing. Placard against aerobatics with fuel in outboard tanks, and plumb the system to prevent fuel from inadvertently migrating from inboard tank to outboard.
 
Pierre - I think you're exactly right about the spin limitation on the Grumman with full fuel. The last student I trained from scratch did all his training in a Grumman AA-1C "Lynx" and even with the larger tail, I think I remember the spin limitation. Thx for the point-out on that!

Operationally, I really do like the idea of having more fuel. Its directly comparable to having more options available. But like Longranger said, we'd need to placard the airplane away from areas that could involve transgressions beyond safe structural and/or stability limits. My main point is that unless you have a good analysis of these barriers, then all I can say is good luck in your test pilot career...
 
....so which model has the longest legs????

...so to start another 'war', there's some long rangers who are using the -9, and it makes some sense , with the longer wing, different airfoil etc. it could be the most efficient at high altitude cruise, right?
...not saying the wing wouldn't need some beefing up, but could it be the best wing to start with?
Are there advantages to the 4 over the -8? or are they all within a few percent of the same drag, when you start to load them up like this?
 
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