3D Joy

I think there will be a good amount of fuel left in the tank after the 40 mile trip. That is provided you don't do too many loops while traveling.

If the plane travels 20 miles an hour (which will most likely be more), it would take 2 hours to do the trip. In reality the trip should take less than 2 hours so with 50 ounces it should be OK.

My experience is that only the flying style can account for about as much as twice the fuel economy.

My ZDZ 80 RV on 32 onces flies for 15-18 minutes with about 8 ounces reserve. That computes to about 1.5 oz/minute for 3D flying. With 50 ounces and 4 ounces reserve that makes 30 minutes for 3D flying!!

Then you have a smaller engine and a plane that flies on its wings. The engine is rugged so it can be lugged down a fair bit with a bigger prop than recommended. It could be leaned but I really think only a big prop and 50 ounces would well be enough.

shakeelsid

You are so right 3D joy. these 3D planes defy gravity as well as aerodynamic logic for being way overpowered. Any good 3D plane has 2:1 thrust to weight ratio - which means that they would prop hang at half throttle and hover at slightly above idle. A ZDZ 80 powered 3D plane would be be around 20 lbs with small aerodynamic crossections and wet areas - all the recipies for very low drag at these 3D speeds. I fly both these new fangled 3Ds and the traditional classics - I dont find a major difference in the fuel consumption of similar engines in these two different type of machines. One putters around on its wing and does an occasional loop and stall turn, the other is flown on the prop most of the time - but both burn more or less the same fuel - they are both running at about the same RPM.

Isnt this a wonderful world

3D Joy

That was not exactly my point. My plane is a fat 33% at 24.2 lbs dry. The engine works quite hard and flies a good amount of time with not that much fuel.

I'm sure the G62 is even more fuel efficient than my 80RV.

Kweasel

My Feedback: (29)

Its going to take full throttle to keep ahead of farmers on tractors. Forty miles is a long cross country in the full scale version.

Tired Old Man

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Wrong!!!

I'm willing to bet that with a little good tuning and the right prop you can make close to 250 kilometers on about a gallon of gas at speeds in excess of 35 knots. I wouldn't bet if I didn't already know I'd win with a very comfortable margin

RTK

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[8D]

ROGER RUSSELL

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JUST THINKING HERE

With this being a gas engine and a pumper for a carb,
CAN THIS BE DONE...............

Hook up two gas tanks "Y"ed into the carb?

1. Would this then draw from both at the same amount?

2. Empty one out first then the other?

3. Cause a air bubble if one emptied out before the other?

4. Am I just trying to out think this to early in the morning on a Saturday?

rc bugman

My Feedback: (30)

Do not hook them with a Y. The fuel draws at different rates depending on the internal friction and filling is a problem.

Hook up the tanks in series. Vent line of tank 1 to clunk in tank 2. Works great, I do it all the time

elson

ROGER RUSSELL

My Feedback: (12)

It was mentioned that way earlier, might try this if fuel is a ? mark. add another 12-16oz tank somewhere in cabin of CUB.

shakeelsid

If you only want a straight cruise, it is very easy to add extended range fuel tank in a plane like a cub - I did it once by tie-wraping a two litre washing up liquid bottle to the spar carry-through super structure. Fuel transfer was gravity feed to the main tank and air vent of the main tank was plumbed into the vent of the auxillary tank. just make sure there are no leaks in the fuel cap on the main tank. You will also be able to fly very stable as long as fuel remains in the main tank as there is no CG change. once you are on your main tank you will need to trim the airplane every few minutes or so. No flip flops allowed with this system though.
My Guess, your 1/3rd scale cub shall be good with a zenoah 62 at around 38- 40 lb. This gives you a good 10 lb fuel load - with a good prop selection and carb tuning I dont see why you couldnt cover 200 miles on this much fuel.

A company I used to work for made reconnaissance UAVs. They used Limbach L-275Es in their 200 pound drones. We used to fill a five gallon tank (basically a pressure tested plastic jerry can) with regular gas and send them out on 200 mile auto sorties. many a times we would use about half the fuel. L275 is a much more refined engine and auto sorties did use sophesticated engine managment, but still, I see no reason why you couldnt go 100-150 miles fairly easily. Do put in a wing leveler and if possible a pitch stability gyro. Fuel burn is drastically affected if you keep diving and climbing to maintain altitude in a cruise. Model airplanes are very very difficult to fly precisely manually for a long time.

happy going
sid

Tired Old Man

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I hate to be the one to tell you this, but that UAV you worked with got some really crappy milage

rc bugman

My Feedback: (30)

With your airframe capable of lifting a lot of wt, why cut it close? Make the main tank out of a 1 gal plastic thinner/oil container and mount it on the CG. Hook the clunk line to a 16 oz head tank vent line to insure constant flow to the engine. Hook the head tank to the carb. Vent the main tank to the outside. You now have 144 ozs of fuel and your plane will carry it just fine. Your G-62 will burn about 2 ozs per min at wide open throttle and you carry enough fuel for 72 minutes. If WOT is 60 mph, you have the 60 miles flown in 60 mins and 12 mins of reserve fuel.

The plane won't even notice the few extra lbs of fuel.

Elson

Kweasel

My Feedback: (29)

Today UAV buyers seem to want maximum loiter time over speed and utility. In the corner of my shop stands an eight foot tall VTOL UAV designed to be a very economical alternative to tilt- rotor UAVs. It has been flying at various sizes since 1990 and was demonstrated successfully for the Army, and nobody wants it. After viewing some old footage of prototypes its clear we were 100% 3D long before modelers embraced it.

Tired Old Man

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You got that right, on all counts

shakeelsid

Its been like 12 years since I left them so I can tell you that yes the UAV we made was no predator - but even predator wasnt that good those days. This was sort of middle of the line small tactical uav - long loiter time is required in a strategic uav. and anything over 100 mission miles per gallon is fairly decent in real UAV world.

Antique

My Feedback: (4)

We have some high speed race planes powered by Herbrandson engines using the Stihl 090 chainsaw cylinders, same as the Limbach...Speed is 220+ mph...We take off, fly six laps on a 1600 foot 2 pylon race course, and loiter around waiting to land...the fuel tank is a gallon jug...We drain out the fuel before refilling...Usually have about 1 inch of fuel left in the tank...
Fuel mileage ? almost none Really crappy would be good in comparison

shakeelsid

So....
What else do you expect going 220 mph. Limbach was 274 cc twin opposed, and really not the very best of engines. It was a big thing in the days before 3D large scale models, when when you could count all big engines for UAVs on one hand alone - heck I had a modeler friend who had lost part of his finger in a bout with a Kawasaki 51 - even he could count them all.
what RPM do you run on your stihl 90 - what prop? you should be getting in excess of 15 hp to go that fast. We used to have those target drones with a 38 hp wankel rotary doing that sort of speed. The engines were more or less disposable, as a re-run after any extended full throttle operation required major surgery. We scrapped many of those rotaries during test phase, and they were routinely used as wall ornaments or anchors. I wish I had salvaged a few, they would be very nice on a large warbird or biplane.

Antique

My Feedback: (4)

The reply was just to illustrate how much fuel an engine CAN use...Our Herbrandson twin drone engines using 090 cylinders run about 9000 rpm with a 21x27 carbon prop, on glow fuel...
I have one of the Limbach engines here....

shakeelsid

Vow, 21-27 at 9000 - thats more like 35 HP. I didnt realize it was a twin[:@]. Must be an awesome sight, sound and smell.

Tired Old Man

My Feedback: (1)

I'm kinda familiar with your plane. It's design and size has been modified and used many times since then. I was giving you a bit of a hard time on the mileage thing. There have been tremendous strides in fuel economy since then, without sacrificing speed

NM2K

My Feedback: (14)

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But, if the large UAV was connected via satellite up/down link and possessed even a limited FLIR/RADAR array, the alternators required to power the equipment would have contributed significantly to the high fuel consumption. Even a seriously powered video transmitter would eat up a considerable amount of electrical power.

Whatcha think?

Antique

My Feedback: (4)

The Herbrandson twin started with Stihl 090 cylinders, later changed to their own design because of a problem with the cylinders breaking off at the hold down nuts...
Mahle made two different versions of their cylinders, the latest in an attempt to get as much mileage from the fuel as possible..There are some creative transfer ports in the latest cylinders...Dyno tests showed 26 hp stock...I think the UAV missions were about 6 hours running at 7000 rpm, so fuel economy was a factor...Apparently the program ran out about 20 years ago, so when our supply of parts runs out there are no more...
The engines I have came from Aquila drones, run as pushers with the engines in the rear...