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Extra fuel in the wing tips 🛫

romanov

Well Known Member
Hello, I am looking for some professional
advise about extra fuel in the wings.
The guys from WhiskeyHotel are not answering
so maybe there are more guys who can help?
 
It has been done many times over the years by various builders. You might have do some forum searches to find what you are looking for.

Several Harmon Rockets have been made with wing tip fuel tanks.(Before the F1's came along with larger main tanks as standard) Those tips are the same air foil /wing tip profile as the 4, 6 ,7 and 8 wing. You might check with John Harmon in Bakersfield CA for photos and contacts that have done it. Most often personally designed and fabricated. Some have a recessed fuel filler cap inside a hinge door similar to the oil inspection door on the engine cowl. There are lots of different solutions.
 
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For an RV-14 a ferry tank in the baggage compartment should be a lot easier, carry more fuel and you can take it out when not needed.

Various molded race car tanks work, or make your own to be a glove fit. Carbon fiber honeycomb boards work well for this. My neighbor that flew his Lancair 4 non-stop from Guam to Jacksonville Florida made 5 ferry tanks using this material. They are a work of art.

Carl
 
Hotel has a setupu for the -14 now. A friend just installed it. They are nice. They are slow to respond but the product seems very good. I'd keep trying or leave a voice message the owner or his daughter usually get in touch.
 
Hotel has a setupu for the -14 now. A friend just installed it. They are nice. They are slow to respond but the product seems very good. I'd keep trying or leave a voice message the owner or his daughter usually get in touch.

Can you post more info on this? Do you have a link? Googling "Hotel" brings up quite a lot of results... :D
 
I have been thinking about different ways to get an extra hour?s worth of fuel in my new RV-3. I checked with the folks at whiskey hotel and they report that none of their kits will work in a 3.

I?m back to thinking about converting the wingtips to fuel tanks. Of course you wouldn?t want to do any aerobatics with fuel in the tanks, but I?m looking at it as a pretty efficient (I.e. minimal additional weight) way to add a few gallons.

I?m thinking they could gravity feed to the main tanks. Fuel management would consist of burning the mains down enough to accept the extra tip fuel. Open electrically-operated valve and let the fuel flow to the mains. Of course a person would want some way to make sure the fuel actually transferred and you?d want to have alternate landing plans if you couldn?t positively verify the transfer.

They?d probably go unused 95% of the time, but an extra hour worth of gas would be pretty handy for certain of my 550nm-ish trips.

My hangar is already a disaster of fiberglass dust from installing wheelpants on the Midget Mustang. Maybe now?s the time?!?
 
Hello, I am looking for some professional
advise about extra fuel in the wings.
The guys from WhiskeyHotel are not answering
so maybe there are more guys who can help?

Both Chuck and Jeff fly for American Airlines, so they may be on a trip. They will respond when they get your message.
 
Extended range tanks

I saw a magazine photograph of an RV.... 8 perhaps, with a large external belly tank which gave a CLAIMED 3,000 mile range. Does anyone have further knowledge of this. It would certainly be an interesting thought.

Brent Owen
 
I've used Hotel Whiskey tanks in both of my 10's and the 7, and have installed them in other customer's airplanes as well. Be patient. I'm sure they will get back to you. It is a good product, tried and proven.

Vic
 
It has been done many times over the years by various builders. You might have do some forum searches to find what you are looking for.

Several Harmon Rockets have been made with wing tip fuel tanks.(Before the F1's came along with larger main tanks as standard) Those tips are the same air foil /wing tip profile as the 4, 6 ,7 and 8 wing. You might check with John Harmon in Bakersfield CA for photos and contacts that have done it. Most often personally designed and fabricated. Some have a recessed fuel filler cap inside a hinge door similar to the oil inspection door on the engine cowl. There are lots of different solutions.

A other popular option from John is bigger tanks. He sells new skins for extended tanks to get you about 58 gallons total- a bit more if you reverse the end ribs. Ive looked at a variety of options for more fuel and bigger tanks keeps winning as the most reliable way to go in the long run. My Rocket will be so modified eventually.
 
Having read a lot of these ?extra fuel? threads and still being undecided on whether I wanted to incorporate extra tip tanks or LE tanks or just a temp tank in the baggage compartment, I contacted Andair directly and ordered this:

The extra positions can be capped (and labeled INOP).

I think it was an extra $40 or so, but gives me a lot of flexibility.

I really like that I won?t have to affect the standard fuel system.


201810071-10-large1.jpg
 
26 gallon tanks on my RV6

I wanted a little extra range so I got some 6' tank skins from John Harmon (don't know if he makes them anymore) I then cut them back so I had one extra bay.

I did several structural changes to the spar and to the top wing skins to accommodate the extra weight. Has worked perfect for 1300 hours.

Steve
 
I just installed the hotel whisky Er tanks in my completed 10. I did so without removing the main tanks. It was not an easy task, but it can be done. I have used them now on several trips. I really wish I had installed them when I built the plane. I did make a slight modification to the transfer system. I added a ?T? in the transfer line and a 2psi pressure switch to confirm that fuel is indeed flowing into the main tanks. I did not feel relying solely on the fuel gauges to confirm the transfer was a reliable solution.
 
I put one of those baggage compartment smoke oil tanks in my 6 for an additional 7 1/2 gallons. I have a pump under the floorboard to move the fuel to a wing tank as soon as I make room for it.

Ed Holyoke
 
Romanov,

Couple of thoughts. Some have mentioned just building bigger tanks. I like that idea, if the plane is not aerobatic (or you don't intend to do acro), but... If you plan on acro, there'd be no way to keep fuel weight confined to the design location. That affects spin characteristics, makes it more difficult to manage quantity, etc.

Several of us who are building 2 seat RVs have simply (ha ha) wet a few bays of the outboard leading edge to add capacity. This is probably the lightest way to do it. I think that all the parts for a pair of 13 gallon tanks weighed about 2 lbs (plus fuel line, valving, etc). Plumbing has been done multiple ways. If you bring the aux tank lines to the fuel selector in the cockpit, you can keep the fuel delivery system almost completely stock. Not a small consideration, since many homebuilt accidents are related to fuel delivery issues.

FWIW,

Charlie
 
Romanov,

Couple of thoughts. Some have mentioned just building bigger tanks. I like that idea, if the plane is not aerobatic (or you don't intend to do acro), but... If you plan on acro, there'd be no way to keep fuel weight confined to the design location. That affects spin characteristics, makes it more difficult to manage quantity, etc.

Several of us who are building 2 seat RVs have simply (ha ha) wet a few bays of the outboard leading edge to add capacity. This is probably the lightest way to do it. I think that all the parts for a pair of 13 gallon tanks weighed about 2 lbs (plus fuel line, valving, etc). Plumbing has been done multiple ways. If you bring the aux tank lines to the fuel selector in the cockpit, you can keep the fuel delivery system almost completely stock. Not a small consideration, since many homebuilt accidents are related to fuel delivery issues.

FWIW,

Charlie


Not sure what your pro/con analysis is suggesting here. Building a larger tank a few bays towards the tip is less overall weight than "wetting" a few bays AT the tip, and certainly results in a lower MMOI. The bigger tank also has zero changes to the supply plumbing, which is better than "almost completely stock".

Adding bays to a fuel tank design has some drawbacks, but from a systems integration and weight perspective its about the best way to go.
 
My point was, that if it's an acro-capable a/c, I want to keep it as close to 'stock' configuration as I can for acro. By keeping the aux fuel in separate tanks, with minimum achievable weight gain to make the tanks, I'd hope to preserve acro ability (with empty aux tanks) and still have the option of extra range and/or tankerage.

Everything's a compromise; I accept the compromise of an extra position on the fuel selector, to keep acro capability.

For non-acro planes, I like the idea of just making the tanks bigger, as I said in the 1st paragraph of my earlier post.

Does that help?
 
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Not sure what your pro/con analysis is suggesting here. Building a larger tank a few bays towards the tip is less overall weight than "wetting" a few bays AT the tip, and certainly results in a lower MMOI. The bigger tank also has zero changes to the supply plumbing, which is better than "almost completely stock".

Adding bays to a fuel tank design has some drawbacks, but from a systems integration and weight perspective its about the best way to go.

"Just make the tanks bigger" is a lot more easily done on a slow-build 4 or 6. Much more difficult on a later kit because the spar is pre-punched for rivets outboard.

Separate leadung edge tanks a bit further outboard aren't going to impact the MMOI much worse and they're lot easier (relatively at least) to integrate on a - 7 or later, especially if you don't mind them not being removeable.
 
I went the "extra tank" route on my 9A (a la Pat Tuckey), I kept the original tanks as almost stock and converted the outboard leading edges from structural to tankage. I added a small non-fuel bay about 6" wide between the two tanks, with an access plate, to contain a transfer pump and connections. Then the outside leading edge was turned into a fuel tank by removing 5 structural ribs and installing 7 fuel ribs (same as the inboard fuel ribs) plus end plates and a baffle with Z-plates to the spar in the back. My outboard tanks are not removable - they remain riveted to the spar just as the original plans called for, and if I develop a major leak in them I'll simply abandon them in place and use only the inboards. I use a rocket-style fuel vent at the wingtip that feeds the outboards with air, and the lowest point (fuel pickup) of the outboards is connected to the highest (vent) point of the inboards, to provide flow-through venting and automatically transfer fuel from outboards to inboards as the engine burns it from the inboards. This preserves a two-tank fuel valve in the cockpit to simplify the plumbing. The outboards have a 15.5 gallon each side measured capacity and only add a handful of pounds (11 pounds total, if memory serves, including transfer pumps) to boost total fuel available from 36 to 67 gallons. Being honest about it, I'm going to say this mod (both wings) added 100-125 hours of additional build time.

I do not make landings with fuel in the outboards - the weight of the fuel and the long lever arm increases the bending moment on the wing root and could cause damage there - so I only use the extra tankage when I know I will burn the outboards dry in flight, often landing with full inboards and avoiding a fuel purchase at a high-price location. I have about 330 hours on the airplane now and make a lot of long cross-country trips with it - I probably have close to a quarter of my total time with fuel in the outboards and love the mod.
 
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Can someone explain to me what it is about the hotel whiskey tanks that justifies a $2500+ pricetag? Maybe I need to see a parts list to help me feel good about spending that amount for what seems like a minimal amount of material.
 
When one gets older the fuel capacity is directly proportional to ones bladder, for me that's 2 hrs tops:D
 
Can someone explain to me what it is about the hotel whiskey tanks that justifies a $2500+ pricetag? Maybe I need to see a parts list to help me feel good about spending that amount for what seems like a minimal amount of material.

I wouldn't pay that much. On the other hand, I did pay almost 20 grand for a few thousand dollars worth of parts when I bought my -7 kit. What's your time worth, and do you have the skills/tools to make them yourself?
 
I wouldn't pay that much. On the other hand, I did pay almost 20 grand for a few thousand dollars worth of parts when I bought my -7 kit. What's your time worth, and do you have the skills/tools to make them yourself?

Exactly correct. HW designed them, built them, marketed them, and has been at least moderately successful selling them. Some people have more dollars than time and are willing to make the trade. It's called capitalism.

You don't have to buy them, you can always build your own.

This is exactly the same reason we are paying north of $25,000 for a O-360 series new engine today, as well. What can Lycoming say that justifies the price? They don't have to say anything to justify it - because we keep buying it.
 
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I’m thinking I can enclose the space in the wingtips and make a composite tank. Shouldn’t be more than about $50 in fiberglass and resin (have most of it on hand anyway), another $150 for some Jeffco sealant, a couple of fuel caps, some fuel line, etc.

All told, less than $500 in materials. If I don’t use them (probably 90% of the time), they just sit there empty. When I do use them, I’d certainly want to limit my flying to airliner-style gentle because of the additional loads and stresses.

Wetted tips just seem like a simple, non-intrusive option. With the help of a good friend who’s an expert with composites, I fabricated a 15 gallon header tank out of pre-preg fiberglass. It wasn’t terribly complicated or terribly difficult.

Honestly, my biggest fear is removing the wing tank to provide access to install a port for inbound fuel transfer. The tanks have been off my RV-3 at one point or another, I just haven’t been the one to do it. The flathead screws aren’t painted, so aside from concerns of scuffing the adjoining skins, I am hoping to do it without damaging anything.

As I get older, my range is becoming more and more bladder limited, but I’ve known folks to use a relief tube with some success, so I’m considering that option, too. None of this stuff is high on my list of priorities, so it may never happen. Just always brainstorming ideas to create the perfect plane!
 
The tip is quite floppy until it's screwed to the wing, and as strange as it sounds, it can be 'rotated' around the end rib quite a bit while fitting it (see the many threads on lining up the tip trailing edge to the aileron trailing edge).

What stopped me on the wet tip idea was the need to keep the flange area perfectly shaped to fit the wing. The only way I could see to do that was to buy a couple of extra wing ribs, skin, etc to make a jig, or to attach the tip to the wing and build a jig around the tip. Seemed like a lot more work/expense than just wetting the leading edge. If the wing had already been built, that would have changed the equation a bit.

My total expense for two leading edge aux tanks was the fuel fill caps/housings and the plumbing hardware. Scrap aluminum sheet, rivets and proseal (already on hand) were all I needed for the tanks themselves.
 
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My point was, that if it's an acro-capable a/c, I want to keep it as close to 'stock' configuration as I can for acro. By keeping the aux fuel in separate tanks, with minimum achievable weight gain to make the tanks, I'd hope to preserve acro ability (with empty aux tanks) and still have the option of extra range and/or tankerage.

Everything's a compromise; I accept the compromise of an extra position on the fuel selector, to keep acro capability.

For non-acro planes, I like the idea of just making the tanks bigger, as I said in the 1st paragraph of my earlier post.

Does that help?

Makes sense. I think I glossed over your concerns about maintaining acro capability. Roll rate will slow with bigger tanks and spins would have to be fully explored again, but beyond that I'm thinking the typical RV style sloppy/ fun acro would remain essentially intact. I certainly get upside down with the Rocket on virtually every solo flight and I intend to keep doing the same when I install the big tanks.

Of course when they are full, then that will define the "airliner" profile. Which brings up another point with my particular mission. When goofing off, I typically fly with min fuel. If I manage to land at home with near full tanks, I will usually offload most of the fuel if I know my next few flights will be local.
 
I?m thinking I can enclose the space in the wingtips and make a composite tank. Shouldn?t be more than about $50 in fiberglass and resin (have most of it on hand anyway), another $150 for some Jeffco sealant, a couple of fuel caps, some fuel line, etc...

I'd take a good look at how the shear load of that new tank is addressed. The L-39 uses a similar attach method for its 26 gallon tip tanks, but the fasteners going into the upper and lower skin are large, numerous and in double shear. In addition, there is a hefty lug that ties the Tank into the main spar.
 
I'd take a good look at how the shear load of that new tank is addressed. The L-39 uses a similar attach method for its 26 gallon tip tanks, but the fasteners going into the upper and lower skin are large, numerous and in double shear. In addition, there is a hefty lug that ties the Tank into the main spar.

The L-39 is also designed for significantly higher aerodynamic loads.

I know you know that, I'm just sayin... sometimes overkill is appropriate caution, and sometimes it's just overkill.
 
Im not suggesting a copy of the L-39, but hanging a wet tip off a bunch of #8 screws countersunk into fiberglass will take some careful study.
 
I've seen several load tests at fly-ins when uncaring/unaware parents use wingtips as baby changing tables! Those chubby infants with a full diaper have got to be pushing the weight of 5 gallons of 100LL!

:D
 
I've seen several load tests at fly-ins when uncaring/unaware parents use wingtips as baby changing tables! Those chubby infants with a full diaper have got to be pushing the weight of 5 gallons of 100LL!

:D

They?d need to be really chubby:
5 gal gas = 30 lbs, at 3.8 g = 114 lbs.
 
Airliner-gentle? Some dim memory is stirring as I read this

whether it was here or on the Matronics list, I don't recall... a certain airshow RV pilot was stating that adding fuel capacity to the wings had no penalizing effect on aerobatic gross weight and might even lessen stress in the spar by bending it the other way when pulling G's - and Van's be darned if they disagreed with him. I was not so sure I agreed with the aerodynamix that were being propounded, but nevertheless, there it was.

Anyone else recall that?
 
Don't recall that particular thread, but there are multiple issues; not just wing bending moment/gross weight. Yes, spreading the load out along the wing can reduce the bending moment at the root, *but* spin characteristics and control effectiveness can change radically. At least for me, that's the reason to keep the plane as close to stock as possible for acro.

edit: Not meant to say I wouldn't add aux fuel; I'm doing that on my -7. Just that I made every attempt to keep added weight to a minimum, and kept the ability to fly with fuel in only the original tanks when flying acro.
 
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I'm just getting started so maybe I'm way off base here but my understanding is the HW Aviation tanks function by pumping from a small auxiliary tank into the main tank via a bung in each main tank. They even sell the bung kits separately that you can install when building to make it easier to add extended tanks in the future if you so decide.
Would it be possible to install an additional bung in each wall of the fuselage with a hose leading to each main tank, then have a removable additional tank (like an RV12 tank?) that you could secure in the baggage compartment with a single pump and a fuel selector switch? Then have a hose leading to each of those bungs in the fuselage wall. You could install the tank and hoses when needed for long trips, then remove it if you don't need it or want to do aerobatics/spins. It would have the additional benefit of being able to visualize a volume gauge in the tank while flying to verify that the fuel has transferred to the mains.
Maybe there are factors I'm not considering but I would think it would be lighter and cheaper than two separate tanks plus the benefit of being able to remove it. Granted you would use up most of your baggage capacity with a full tank but maybe a vertical tank right behind the seats (e.g., like a briefcase shape right behind the seat) would help keep the COG a little more forward. crazy?
 
What's the mission? If you're just doing solo distance record stuff, sure. But if you're doing it to tanker fuel and/or for travel with a friend, then as you said, you lose both baggage volume and payload, because all the bending loads are in the center of the airframe. You're also riding around with a lot of gas in a temporary, removable container in the cockpit with you. Even without fire, a leak could be overwhelming. And depending on your alternate choice of built-in tank 'method', it can be significantly heavier. My two leading edge aux tanks added around 30 gallons capacity at the expense of about 2 lbs additional weight (probably around 4 lbs total, including fuel lines).

Your choice on plumbing. Mine is (was, at the time) a bit of a special case. I knew I was going to be using automotive style injection, so the engine is fed from only one tank (ala turbines). The other three tanks are all aux tanks, and the fuel selector just picks which one transfers to the main. Downside: no backup tank (but *many* a/c have only one tank, or a header that's fed from selected tanks). Upside: no switching tanks and no need for a duplex fuel selector.

If you want behind the seats tanks, here you go:
https://www.smokingairplanes.com/products/
His tanks can be plumbed as aux tanks.
 
The smoke tanks are about exactly what I was envisioning. Though the more I think about the W&B, I realize it would be quite limiting in terms of eating up your baggage capacity.
Your tanks adding 30 gal additional capacity at only 4 lbs is impressive. What are they made of? I couldn't imagine aluminum tanks being that light. I like the thought of your auxiliary tanks all feeding into one main, or how the HW Aviation aux tanks feed into the mains. Considering many engine-out issues are related to fuel delivery, if an issue with delivery from the aux tanks were to ever occur, I'd think it would be likely to be discovered when you still have several hours of fuel left, rather than a potentially really bad time.
I realize Im getting a bit ahead of myself. I'm doing my empennage build at Synergy in February so even thought I haven't started building yet, I just ordered my QB fuselage & wings so that the project doesn't stall out waiting for them after finishing the empennage. So I'm trying to be proactive and am researching things I need to think about ordering for the wings & fuselage. thanks for the pointers.
 
Mine are so light because I wet 3 bays of each outboard leading edge. Only added weight are the fittings, fuel line, and some scrap aluminum to cover the lightening holes in the nose ribs. Would be a bit more effort on a quick build, but it's doable with a modified technique.
 
Has someone already tried to "simply" build bigger standard tanks?
So enlarging the tanks by two or three ribs spanwise?
 
Yes, I do not have any links but at least one person has made an RV14 with essentially RV10 fuel tanks. Giving you 60 instead of 50 gallons.

Do the 10 and 14 have the same airfoil and chord length? So do the 10's tanks fit?
 
Hi Malte,
some guys have extended their tanks all the way to the tips.
But doing any change to the original design (in Germany) will probably not excite your counselor and the LBA. That?s why I made a removable tank for the rear baggage area for my -8. Even then the LBA required quite some calculations and fulfilling of "building codes".
 
I did make a slight modification to the transfer system. I added a ?T? in the transfer line and a 2psi pressure switch to confirm that fuel is indeed flowing into the main tanks.

Bill;
Can you give some info on the 2 psi switch you used. Mfg, source, etc.
I just ordered the tanks last night at 6:30. Hotel Whiskey answered within the hour. HW is under new ownership and apparently have solved the previous communication problems. Off to a great start.
 
Stewart Warner Hobbs Pressure Switch 1 PSI Normally Open 2 Terminal - p/n 78628. I did not remove the main tanks for the installation. So I did not use the Bung fitting provided by HW. Instead I used a bulkhead flare that I sealed on both sides with proseal in the top rear corner of the main tank. I also cut a 4" X 6" panel opening in the wing to perform the installation and to inspect and access the pumps etc. It was not an easy task to work in that confined space, but it can be done with lots of patience.
 
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As this is an interested crowd, I am selling the 5-way valve I showed in post 14 of this thread. Please check the classifieds...

Might be useful for someone watching this thread.
 
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