# Can a SkyPup break the FAR103 constrained distance without refueling/landing record by flying an electric motor?

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#### patrickrio

##### Well-Known Member
The Current record is held by a Mitchell Wing. I have not been able to find the record, but I believe it was set by some guy named Gary something in the eighties and it is somewhere between 300-400 miles. I think a guy named Jon did a completely weight confirmed distance of 309 miles in 2000. A first step to this task is to find the ACTUAL official and unofficial weight and fuel limited record distances. Input appreciated...

There are two other Mitchell Wing records, one in the 600 mile range and another in the 800 mile range. Both of these flights definately exceeded the 254lb weight limit as well as the 5 gallon fuel limit. They are not the records we are after.

The SkyPup likely cannot break the record with an internal combustion engine.... the 5 gallon fuel limit and the airframe that is more draggy than a Mitchell Wing mean that the 5 gallon fuel limit will favor the Mitchell Wing.

BUT a SkyPup airframe is a decent amount lighter than the airframe of a Mitchell Wing. In fact, some SkyPup airframes can weigh less than 150lbs without engines. This leaves a potential 104lbs or more for a motor/battery solution that might be able to break the distance record.

I propose that we figure out and source and price a complete solution that weighs less than 104lbs and can likely fly a skypup for 400 miles or more.

If we can do it, we leave all the info here ready for some SkyPup owner to take up the challenge.

You guys in?

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#### patrickrio

##### Well-Known Member
As a first pass at equipment, I suggest the Open PPG SP140 motor and maximum battery packs to fit under weight.

I can only find an empty weight of the entire PPG backpack , propeller, cage etc of 31lbs. The first 2.2kw of power weighs 22lbs and each additional 2kw weighs 16lbs. So, at a first pass, we can get a 104lb solution that has AT LEAST 8.2kw of battery power on board. Cost would be less than $8095. 8.2kw is likely a VERY conservative number for power capacity possible. I calculate a weight of 101lbs INCLUDING the whole PPG flight kit and we only need the motor battery and electrical management from that. Cost is also likely high because of this. Also, the motor has a continuous rating of 25kw/33.5 hp and the SkyPup can fly quite comfortably on as low as 18 hp.... so we could save weight with a smaller motor too. Actually, if I remember correctly, the 80s Mitchell Wing record was flown with an 18 hp motor to make weight with 5 gallons of gas and was VERY underpowered. We could probably do the same with the Skypup motor choice too, if necessary. In order to calculate if we are in the vicinity for necessary power capacity, we need to get calculations for the flight efficiency of the SkyPup... I don't have these... but one of you does!!! Energy calculations would be done at maximum distance/efficiency speed for the SkyPup as this is the same method used to fly the Mitchell Wing flights. Last edited: #### Vigilant1 ##### Well-Known Member Lifetime Supporter No constraints on budget? Proposed way of working this out: 1) Determine or realistically estimate how many HP the IC Skypup needs to cruise at best range airspeed. Multiply by 746 to get watts required, at the prop, for flight. 2) Find and price an electric motor that big, with enough surge HP for takeoff and climb. 3) Batteries: Power draw at cruise will be about 115% of the motor output (controller losses, motor losses, cable losses). 4) Determine max allowable battery weight now that we know weight of the motor. Be sure to allow for the weight of any structural beef-ups needed to accommodate the batteries in a SkyPup airframe. 5) Research real, available batteries, cells, and BMS systems to see how many watt/hours you can get into your available weight budget. Prices will vary a LOT between OTS batteries (e.g. Battleborn LiFePo 1800 w/h batteries, 31 lbs,$900) and DIY battery built up from 'factory second" cells purchased off Alibaba with an aftermarket BMS.
6) Assure the C-rate of the batteries can meet the required current draw.
7) Divide the available battery watt hours by the cruise power draw to determine flight duration and range.

Sorry, I don't want to do the research, but this is one approach.

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#### John.Roo

##### Well-Known Member
You are right that electric motor is lighter than combustion engine.
Unfortunatelly is energy density in cells MUCH smaller than energy stored in fuel.
5 US gallons = 19 lit.
That is a lot of energy....
Look for FAR 103 airplane with best L/D. It should look like a glider and the only way ho to go that far (over 300 miles) is good soaring day.
To brake record done with IC engine with electric motor you need airplane like:

Atos Wing

or Archaeopteryx

I am affraid that SkyPup has lower L/D than Mitchel Wing so no way to beat this record with electric or IC motor....

#### Vigilant1

##### Well-Known Member
You are right that electric motor is lighter than combustion engine.
Unfortunatelly is energy density in cells MUCH smaller than energy stored in fuel.
5 US gallons = 19 lit.
That is a lot of energy....
.
Right. When converted to mechanical energy at the prop by a small 4stroke engine, 5 gallons (30 lbs) of fuel provides about 50kw/h of energy. If using the OTS Battleborn batteries, we'd need to buy 28 of them to match that. They'd cost about $22,000 and weigh about 900 lbs. Liquid hydrocarbons pack a LOT of energy in a small weight/size. In answer to the OP: No, an electric Pt 103 legal Skypup almost certainly cannot fly farther than an IC powered Skypup that is Pt 103 legal (5 gal of gas onboard). Last edited: #### patrickrio ##### Well-Known Member The issue here is available weight for the battery pack to keep below the 254lb weight limit. This is where the Skypup catches up to the Atos Wing. For example, the Air Atos Wing weighs 265lbs empty (already overweight) and only has 4kw of battery on board at that weight(I think... I have seen 5kw listed too). We know that the Skypup can probably carry 2x or more battery and make weight. the skypup is non THAT much less efficient when flown at it's most efficient speed.... The empty weight of the Archaeopteryx is 197lbs with motor and battery. So it likely is an even better candidate than the Skypup if it can carry another 60lbs of batteries...... it already has a motor onboard! My gut tells me you can do it in the skypup though... I think it's current distance record with 5 gallons is already 270 miles..... It is pretty efficient. #### Hot Wings ##### Grumpy Cynic HBA Supporter Log Member The first 2.2kw of power weighs 22lbs and each additional 2kw weighs 16lbs Kw or KwHr? The Skypup has a L/D of 12:1 ......... per WikiP That leads to 33 pounds of thrust at best L/D (@400 lbs)which is generally around 45 MPH for this type of ultralight. 400 miles then takes 8.3 hours Using my ICE rule of thumb 1 hp yields 4 pounds of thrust. (big assumption) Therefore it takes about 6Kw for level flight. (seems reasonable) 6Kw x 8.3 hrs = 50 KwHr If the numbers provided are KwHr then 50KwHr - 2.2 (initial power weight) = 47.8 (additional power weight) --------- 47.8/2 KwHr x 16 lbs = 382 pounds for the additional power packs The Mitchell wing, especially with a pilot pod is much cleaner aerodynamically and the best L/D can be at a significantly higher speed than the SkyPup. I'd start with that air-frame for this project. I've run the numbers (backwards/forwards/up side down/and inside out). A hybrid power train in a part 103 legal Mitchel wing can reach the 400 mile goal using pretty much OTS parts and batteries. A slightly up-sized system is on my to do list for the AV-361 that I'd like to build someday if I can find the time. Less time typing here on HBA would help with that....................... #### Dana ##### Super Moderator Staff member First a Mitchell Wing is far more efficient than a Skypup. Second, even though an electric motor is lighter, the mass energy density of any battery is so much worse than gasoline, it'll never go as far. Third, any distance record for an ultralight will be accomplished by soaring, even if it's helped by an engine, so soaring performance is more important than the powerplant. I believe the (unpowered) paraglider distance record is at 365 miles now, that's a 7 hour flight. #### patrickrio ##### Well-Known Member Right. When converted to mechanical energy at the prop by a small 4stroke engine, 5 gallons (30 lbs) of fuel provides about 58kw/h of energy. We'd need to buy 32 of those OTS Battleborn batteries to match that. They'd cost about$25,000 and weigh about 1000 lbs.

Liquid hydrocarbons pack a LOT of energy in a small weight/size.
You are correct on all of this, of course. BUT the Mitchell Wing record is held with a 2 stroke motor because of weight limits.... A four stroke could not fit in the past. You may be able to break the Mitchell Wing records though with one of the new 4 stroke paramotors coming out.... they are pretty light!!

so we are comparing the efficiency of a 2 stroke engine package to the efficiency of an electric package. Thrust to thrust, I think the 2 stroke MIGHT turn gas into thrust horsepower at an efficiency of 10%. An electric package can do 60% i think. So as a rough calculation:

The Skypup may be able to carry up to 90lbs of batteries with a light motor or 3 times the weight of gas (this is pushing it, but an easy calc....)
The efficiency is 6 times higher.

can we carry enough battery with these numbers?

#### Vigilant1

##### Well-Known Member
You are correct on all of this, of course. BUT the Mitchell Wing record is held with a 2 stroke motor because of weight limits.... A four stroke could not fit in the past. You may be able to break the Mitchell Wing records though with one of the new 4 stroke paramotors coming out.... they are pretty light!!

so we are comparing the efficiency of a 2 stroke engine package to the efficiency of an electric package. Thrust to thrust, I think the 2 stroke MIGHT turn gas into thrust horsepower at an efficiency of 10%. An electric package can do 60% i think. So as a rough calculation:

The Skypup may be able to carry up to 90lbs of batteries with a light motor or 3 times the weight of gas (this is pushing it, but an easy calc....)
The efficiency is 6 times higher.

can we carry enough battery with these numbers?
No, three people have already explained why. Try the math yourself and see. The major problem you'll have is this: A modern small 4 stroke IC engine converts fuel into mechanical energy at a rate of 1 gallon of fuel gives 10,000 watt hours. That fuel weighs 6 lbs. To get that same 10,000 watt hours from OTS LiFePo batteries requires about 170 lbs of batteries.
The 5 gal of fuel allowed under Part 103 will require about 850 lbs of batteries to match. Your goal is not possible regardless of airframe. I'm sure there batteries with higher energy per lb, but not enough to bridge this gap. The mechanical energy readily available in the allowed 5 gallons of fuel requires batteries that weigh about 3x the max empty weight of a US ultralight.

FWIW: Real world example. Pipistrel Alpha Electro batteries weigh 270 lbs total. they provide 21kw/h of energy. This same amount of mechanical energy can be provided by 13 lbs of gasoline fueling a typical 4:stroke engine.

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#### patrickrio

##### Well-Known Member
Kw or KwHr?

The Skypup has a L/D of 12:1 ......... per WikiP
That leads to 33 pounds of thrust at best L/D (@400 lbs)which is generally around 45 MPH for this type of ultralight.
400 miles then takes 8.3 hours
Using my ICE rule of thumb 1 hp yields 4 pounds of thrust. (big assumption)
Therefore it takes about 6Kw for level flight. (seems reasonable)
6Kw x 8.3 hrs = 50 KwHr
If the numbers provided are KwHr then
50KwHr - 2.2 (initial power weight) = 47.8 (additional power weight) --------- 47.8/2 KwHr x 16 lbs = 382 pounds for the additional power packs

The Mitchell wing, especially with a pilot pod is much cleaner aerodynamically and the best L/D can be at a significantly higher speed than the SkyPup. I'd start with that air-frame for this project.

I've run the numbers (backwards/forwards/up side down/and inside out). A hybrid power train in a part 103 legal Mitchel wing can reach the 400 mile goal using pretty much OTS parts and batteries. A slightly up-sized system is on my to do list for the AV-361 that I'd like to build someday if I can find the time.

Less time typing here on HBA would help with that.......................
The Mitchell Wing can't make a true 254lbs empty with the pilot pod and the old engines as I understand it... but I have never weighed one myself. It also had to use a less efficient 2 stroke in the past just to make weight. The weight limited records are with light and inefficient 2 strokes and limited aero for the pilot. There are some new 4 stroke paramotors coming out that might work though... The airframe has no room for additional battery weight so it is FOR SURE not a good place to start for battery power if you must stay below 254lbs. The Archytaeopteryx has available weight and a good L/D ratio so maybe it is a better place to start. Its glider weight is 119lbs so 133lbs available for batteries and motor.

Another way of calculating. Gas has 116,000 btus per gallon or 580,000 btus in 5 gallons which is equivalent to about 170kwh of energy. A Skypup can already go 270 miles on this gasoline energy with a Zenoah G25 2 stroke engine. electric powertrains are about 6 times as efficient as 2 strokes at producing thrust I believe, so 170*1/6*400/270=42kwh of battery needed to go 400miles with electric..... 32.5kwh to go 310 miles with electric

not looking good.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
The Mitchell Wing can't make a true 254lbs empty with the pilot pod and the old engines as I understand it...
Most won't make weight. The original U-2 prototype, with retractable gear, was just a little over #200.
Modern paraglider engines along with some carbon rods can help with the weight.

There are probably even better airframes for this particular goal/task. Maybe a Marske design?

#### patrickrio

##### Well-Known Member
Kw or KwHr?

The Skypup has a L/D of 12:1 ......... per WikiP
That leads to 33 pounds of thrust at best L/D (@400 lbs)which is generally around 45 MPH for this type of ultralight.
400 miles then takes 8.3 hours
Using my ICE rule of thumb 1 hp yields 4 pounds of thrust. (big assumption)
Therefore it takes about 6Kw for level flight. (seems reasonable)
6Kw x 8.3 hrs = 50 KwHr
If the numbers provided are KwHr then
50KwHr - 2.2 (initial power weight) = 47.8 (additional power weight) --------- 47.8/2 KwHr x 16 lbs = 382 pounds for the additional power packs

The Mitchell wing, especially with a pilot pod is much cleaner aerodynamically and the best L/D can be at a significantly higher speed than the SkyPup. I'd start with that air-frame for this project.

I've run the numbers (backwards/forwards/up side down/and inside out). A hybrid power train in a part 103 legal Mitchel wing can reach the 400 mile goal using pretty much OTS parts and batteries. A slightly up-sized system is on my to do list for the AV-361 that I'd like to build someday if I can find the time.

Less time typing here on HBA would help with that.......................
OK.. lets find out how far away we are from making it with the Archytaeopteryx using the same calculations above but with a 96lb pilot to really push the envelope.... so 350 lbs at 65mph best l/d speed (guess) and we are going calculate for 310 miles distance instead because I think that beats the official powered ultralight record.

L/D = 28/1
12 pounds thrust at 350lbs at best L/D at 65mph more efficient than skypup like Mitchell Wing
310 miles take 4.75 hours
ICE rule of thumb leads to 2.2kw for level flight
2.2kw*4.75hrs = 10.45kwh

These calculations are pushing it, as it is for a 96lb pilot and calculated to JUST BARELY beat the 309 miles that I think is the official verified weight and gallons of fuel checked FAR103 legal distance for the Mitchell Wing using the Archytaeopteryx. But I think you could get 10.45kwh of battery and a minimum motor into that airframe under weight. Maybe my calculations are aggressive though....

using 135lbs available and the Open PPG motor and batteries you can fit 12.2kwh of battery in less than 133lbs. with very careful improvements by using a lighter motor and more efficient and larger diameter 2 blade prop you might be able to get slightly better efficiency and hold a few kwh more battery.

And you probably could ridge soar or something to improve that. You can definitely break the record in this plane under electric power.

It is also true that the Archytaeopteryx can absolutely shatter the current distance record with one of the new 4 stroke PPG motors and 5 gallons of gas.... the limit with soaring would probably be the 30 min before sunrise and 30 min after sunset allowed flight envelope and how much you could improve your ground speed with tail winds and increased indicated/calibrated level airspeed at altitude. It is probably capable of over 2000 miles in a dawn to dusk flight in perfect high altitude soaring conditions with a tailwind.

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#### trimtab

##### Well-Known Member
In high school, a friend flew a sky pup he and his father built (in the town it was designed in) for 9 hours straight at 10k' to 16k' almost entirely without the engine running.

I've had hang glider flights of 155 and 204 miles at average speeds of 45-49 mph. My L/D was likely in the 6:1 or 7:1 range at those speeds (UP TRX, pretty capable XC machine).

The sky pup and similar designs likely cannot meet a 12:1 L ratio at cruise...I'd guess perhaps 6 or 7 to one.

The calcs above using l/d are legitimately motivated, but perhaps a different mission profile could make an e-103 a more attractive option. The Pup could be a capable, cheap, light weight platform for a a lot of fun for playing in the mountains with or without the motor on.

Of course, so would a 20:1 rigid wing with a sustainer. 30 minutes of endurance in a package that could yield 30 lbs of thrust at 12k' DA in a foot launchable package could easily turn a lot of normal 2 hour hang gliding flight into 4-5 hour extended XC flights.

Of course, this has been done with ICE's for 3 decades. They didn't appeal to most hang glider pilots for various reasons, but a down level migration from powered pilots might be something.

#### John.Roo

##### Well-Known Member
"It is also true that the Archaeopteryx could probably absolutely shatter the current distance record with one of the new 4 stroke PPG motors and 5 gallons of gas...."
I agree.

So the only limitation will be your budget...
Here you can see prices.

#### patrickrio

##### Well-Known Member
And, for future reference... the point where a FAR103 ultralight powered with electric passes flight time/distance of a gas powered is easily calculated if we know how many times more energy efficient (thrust generated/battery power used) versus gas (thrust generated/gasoline energy used)

It appears that electric has a better efficiency ratio in comparison to gas in airplanes than in cars. When compared to 2 stroke efficiency in airplanes, it looks like electric is about 6 times more energy efficient.

so the 170kwh of energy in 5 gallons of gas should be approximately equivalent to 28.33kwh of battery Once an ultralight carries approximately 28.33kwh of battery, it should be in the vicinity of the max operating time/distance of an equivalent gas powered ultralight carrying 5 gallons of fuel.

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#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Can it (400 miles) be done on pure electric under part 103?
454 pound part 103 @ 28:1 L/D (probably possible with a custom airframe) = 17 lbs of thrust (using my 4/1 rule of thumb) = ~3000 W. This is well within the model motor range so...........

Based on a quick run through some online model calculators:
30 Inch prop* yields about 70% efficiency at 60 MPH - selected as the best design L/D because it is just under the part 103 limit. Thus we need a 4.2Kw motor.
4.2 Kw @ 95% system efficiency = 4.4 Kw of battery.
4.4Kw x 6.6 hours = 29.5 KwHr for the task. This doesn't include any climb energy or assistance from thermals.
SWAG ... cut the power needed in half = 15ish KwHr of battery? IF that is actually enough then the battery pack, using the 8#/KwHr example ends up in the 120 pound range.

454 gross weight (AC 103-7 standard plane) - 120 battery - 96# jockey that can fly an ultralight = 238 pounds for plane and power system (minus battery weight).

MY conclusion:
It looks like it should be possible - but not easy.

* Picked based on "feel" from previous calculations in this speed/power range. Lots of variables here with electric motors and reduction units.

#### Vigilant1

##### Well-Known Member
But is using thermals, etc really cricket?

If I foot launch my SWIFT glider (25:1 L/D) from a hill, glide over to the cooling towers of a nearby powerplant for a lift to 8,000’, hop over to another source of lift, etc and keep repeating that for 20O-400 miles, I'm not sure what that proves about the airplane.

A guy in South America flew over 1700NM in his sailplane using lift from mountain waves, he had no engine at all, but he needed lots of kwh worth of lift.

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#### patrickrio

##### Well-Known Member
We can also calculate when an airplane with the efficiency of Archaeopteryx has a 4 hour autonomy. Since it is basically capable of flying at max FAR103 speed this represents the limits of usefulness for an out and back flight distance of 2 hours each way without recharge and about 110 miles distance without using altitude and winds at differing altitudes to affect the trip.

It is probably right about 10kwh of battery. The minimal 12.00 Hamburger machine. (10 dollar hamburger with 2 dollars of electricity at 20 cents a kwh)

#### Dana

##### Super Moderator
Staff member
At this point, the FAA interpretation is that batteries are part of the aircraft's empty weight... so a 120# battery leaves only 134# for airframe and engine.