New to the hobby, here's my dream

[nycgags]

My dream (likely impossible but who knows):
Fly an RC plane autonomously from East to West coast. If impossible without creating a huge craft, what is max distance I could achieve converting an EDF Sailplane to solar? Burst up to 30 seconds glide for "x minutes" and continue 30 second bursts and re-charging lipo along the way.
I found this 1200 mm wing span example:
https://www.banggood.com/TOPRC-Swif...-RC-Plane-PNP-p-1693224.html?cur_warehouse=CN
What are realistic expectations for performance? How long would it glide for and how much time is needed for this EDF to get up to a gliding altitude? It claims to go 100 mph on a 2200 mAh battery (4S).

30s might not even be needed, 100 mph for 30s = 0.8 miles or ~4k feet, what are the limits (imposed by FAA or otherwise) for most gliders? So maybe calculate battery needed for 10s bursts, and then I would need to calculate how much sun + time is needed to replenish that battery used. 10s burst eats up ~6% of the 2200 mAh battery (estimated 5 minute flight time)

Assume a 14 hour day of perfect sunshine coast-to-coast +3 hours of time zone difference, if I did that right it gives you 17 hours of available sun to charge the Lipo.

Distance needed to travel approx. 3,000 miles from East to West coast which would require average speed of 176 mph, clearly not possible in 1 shot with an RC, but what is the best we could do? How fast is this sailplan w/ EDF motor and battery attached, 30 mph overly optimistic? 510 miles for 17 hours

 

[JasonK]

Fly an RC plan autonomously from East to West coast.

lots of issues there with the FAA regarding BOV/etc.

You wouldn't want to do an EDF, you would want basically a 'powered' glider, something that have a very good glide slope.

I would check out https://www.youtube.com/user/rctestflight as he has done multiple Solar plane project trying to get to 100% solar powered flight (which would be a requirement to make it that distance for an electric motor based plane).

Your other option, might be a very fuel efficient fuel engine (fuel has a much higher energy/mass ratio then any current battery), but I don't know if something like that would scale to an 'RC sized' plane.

 

[nycgags]

Thanks, BOV?

https://www.faa.gov/jobs/abbreviations/

 

[JasonK]

beyond visual line of sight
I got the acronym wrong - bvlos is the correct acronym.

basically the rules for hobbyist (and I think 107s without an explicit exception) is that you or someone standing right next to you has to be able to see the aircraft unassisted (other then corrective lenses).

 

[JasonK]

and if your thought to solve that is to drive along with the plane, I do believe there is also a rule against piloting from a moving vehicle.

 

[nycgags]

and if your thought to solve that is to drive along with the plane, I do believe there is also a rule against piloting from a moving vehicle.

Haha, damn, but it is fine for the govt. to do it, because we can trust them, and they are smart, sigh.

 

[quorneng]

nycgags
You need to establish the average power consumption of the plane against the size & power provided by the solar panel.
At the moment it is just about possible to sustain flight with a very efficient and slow flying plane with the sun at the highest angle.
Even at 100 mph the journey is going to take about 20 hours flying time.

 

[nycgags]

nycgags
You need to establish the average power consumption of the plane against the size & power provided by the solar panel.
At the moment it is just about possible to sustain flight with a very efficient and slow flying plane with the sun at the highest angle.
Even at 100 mph the journey is going to take about 20 hours flying time.

Cool, Cape Canerval to San Diego is a little less than 2200 miles, looks like the FAA prohibits my dream though unless I do it illegally, but probably a dumb idea. I chose that route just looking at the prevailing winds today, it seems like the best route to go against the jet stream (at least today?).

Keep in mind it is a Sailwind (aka glider design with EDF attached) so I do not need the engine running 100% more like 5% to get the glider up to the appropriate altitude, I assume it could maintain it in 5-8s bursts, I do not know how efficient the lipos/engine combo are when it comes to stopping/restarting the engine.

 

[nycgags]

So total theory craft here, 5s burst to get up to altitude (not including original ascent). Assume 5 minute glide time for each burst (total guesstimate). Provides 3600 bursts for a normal 5 minute fly time out of that battery (no solar support).

I chose 5s @ 100 mph = 733 feet theoretically assuming flat 100 mph speed is achieved

5 minutes x 3600 = 300 hours of flight time

Even if I am off by a factor of 10 (I probably am) that is 30 hours of flight/glide time.

30 hours to go 2200 would need a speed of 73 mph, probably still unachievable, but if we now add in solar support to recharge LIPO and use the EDF to help maintain speed? It seems from a theorycraft perspective that I am close.

 

[JasonK]

So total theory craft here, 5s burst to get up to altitude (not including original ascent). Assume 5 minute glide time for each burst (total guesstimate). Provides 3600 bursts for a normal 5 minute fly time out of that battery (no solar support).

5 second burst from an EDF to get enough altitude for a 5 minute glide... at 73mph? not likely.

You do know that air drag is proportional to velocity squared, correct? I doubt anything is going to 'glide' at 73mph at any type of glide slope that would also allow you to only need a 5 second burst of power every 5 minutes to maintain height. How are you coming up with these numbers? (what type of plan can keep a glide slope that can be maintained with a 5 second burst of power every 5 minutes - outside of a glider keeping up with thermals - which you can't rely on for distance flying)

It seems from a theorycraft perspective that I am close.

no... not really

 

[CarolineTyler]

Check out RCTestFlight, he's successful created solar planes that could fly as long as there is sun. So that coast to coast could be done, one day at a time...... maybe.
https://www.youtube.com/user/rctestflight

 

[nycgags]

How are you coming up with these numbers? (what type of plan can keep a glide slope that can be maintained with a 5 second burst of power every 5 minutes - outside of a glider keeping up with thermals - which you can't rely on for distance flying)

Did you click the link of the plane in the OP? It is capable of 160km/h aka 100 mph, do the math for distance traveled over 5s. How many feet do normal (RC) gliders normally climb to before they glide, is it more than 733 feet or about half as much? If the latter I am sure that height can be achieved over 5s. Also for my education, how long would I expect this plane to glide on its own for under optimal conditions (no thermals)?

I did make a mistake but not with the 5s burst, for a normal flight time of 5 minutes for the normal config of the plane, there are (approximately) 60x 5 second bursts available not 3600.

 

[nycgags]

Check out RCTestFlight, he's successful created solar planes that could fly as long as there is sun. So that coast to coast could be done, one day at a time...... maybe.
https://www.youtube.com/user/rctestflight

I have seen a lot of his videos, he puts out good content.

 

[JasonK]

Did you click the link of the plane in the OP? It is capable of 160km/h aka 100 mph, do the math for distance traveled over 5s. How many feet do normal (RC) gliders normally climb to before they glide, is it more than 733 feet or about half as much? If the latter I am sure that height can be achieved over 5s. Also for my education, how long would I expect this plane to glide on its own for under optimal conditions (no thermals)?

I did make a mistake but not with the 5s burst, for a normal flight time of 5 minutes for the normal config of the plane, there are (approximately) 60x 5 second bursts available not 3600.

sure, I do not get that out of the stats on that page, because there is acceleration time needed, planes go slower when climbing, maximum glide time is going to be at a speed lower then that (or it would be losing altitude fairly quickly). but I have already explained why above.

 

[quorneng]

nycgags
Have you noticed the flying time claimed for that EDF glider is 'about 5 minutes'. If it could stay up for longer don't you think they would have claimed that.
I expect it can achieve 100 mph but only under full power and that would result in a duration of 2 or 3 minutes giving a straight line distance of 3 or 4 miles.
Nothing wrong with having a goal but you would have to improve the performance by several hundred times to get even close to a coast to coast distance.

 

[nycgags]

Check out RCTestFlight, he's successful created solar planes that could fly as long as there is sun. So that coast to coast could be done, one day at a time...... maybe.
https://www.youtube.com/user/rctestflight

I shot him a message, big fan of his work, interested to hear his take on an EDF glider, if I heard his last video correctly he put 10k mAh of Tesla batteries in his latest solar, that is an INSANE amount of battery power, nearly 5x what the model I posted in the OP uses.

 

[nycgags]

nycgags
Have you noticed the flying time claimed for that EDF glider is 'about 5 minutes'. If it could stay up for longer don't you think they would have claimed that.
I expect it can achieve 100 mph but only under full power and that would result in a duration of 2 or 3 minutes giving a straight line distance of 3 or 4 miles.
Nothing wrong with having a goal but you would have to improve the performance by several hundred times to get even close to a coast to coast distance.

Yes I read that. Did you read my multiple posts stating I would only use the engine to climb to a gliding altitude in short 5s bursts followed by gliding times of ~5 minutes? It's a sailplane, they are built to glide.

The plane weighs 950g, rctestflight's Volantex Ranger 2400 has 8 cells, each cell is 5000 mAh, compare that with the paltry 2200 mAh in the OP so his clearly weighs more and its not even close, the 1600 weighs 1050g, so I don't see what the problem is.

 

[JasonK]

you do realize that if 'power up' then glide was more efficient then flying at a cruse speed, rctestflight would already be doing that, correct?

Air resistance (IE power lost to air friction) scales related to the square of the velocity -> drag = a * velocity ^ 2 (where A is a constant based on multiple factors, but won't change meaningfully in this situation). meaning when your punched up to a high speed your wasting a bunch of power doing that.
When your climbing you have to spend energy to build up the potential energy from the difference in altitude -> this amount of energy will be the same if you do it at a high speed or low speed, however the drag loss will be higher at high speed.

lets do some math:

Velocity	Drag	Drag Duration	energy lost to drag	potential energy gained	Total energy spent to climb
x	ax^2	2t	2atx^2	w	w + 2atx^2
2x	a(2x)^2	t	4atx^2	w	w + 4atx^2
4x	a(4x)^2	1/2*t	8atx^2	w	w + 8atx^2

As you can see, it takes more energy to climb at a high speed then to climb at a slow speed (even after factoring for the time over which your climbing).

 

[nycgags]

you do realize that if 'power up' then glide was more efficient then flying at a cruse speed, rctestflight would already be doing that, correct?

Air resistance (IE power lost to air friction) scales related to the square of the velocity -> drag = a * velocity ^ 2 (where A is a constant based on multiple factors, but won't change meaningfully in this situation). meaning when your punched up to a high speed your wasting a bunch of power doing that.
When your climbing you have to spend energy to build up the potential energy from the difference in altitude -> this amount of energy will be the same if you do it at a high speed or low speed, however the drag loss will be higher at high speed.

lets do some math:

Velocity	Drag	Drag Duration	energy lost to drag	potential energy gained	Total energy spent to climb
x	ax^2	2t	2atx^2	w	w + 2atx^2
2x	a(2x)^2	t	4atx^2	w	w + 4atx^2
4x	a(4x)^2	1/2*t	8atx^2	w	w + 8atx^2

As you can see, it takes more energy to climb at a high speed then to climb at a slow speed (even after factoring for the time over which your climbing).

So what I have learned, is you do not need to climb at full throttle, if you climbed at 1/5 full throttle (20 mph), you expend a considerable less amount of battery power and lose a considerable less amount of energy due to drag. Instead of a 5s climb it could be a 25s climb (or less depending on target altitude), but since you are only using 1/5 throttle you are using a considerable less amount of battery power.

 

[JasonK]

So what I have learned, is you do not need to climb at full throttle, if you climbed at 1/5 full throttle (20 mph), you expend a considerable less amount of battery power and lose a considerable less amount of energy due to drag. Instead of a 5s climb it could be a 25s climb (or less depending on target altitude), but since you are only using 1/5 throttle you are using a considerable less amount of battery power.

you still seem to be making the assumption of -> speed goes up instantly with increased throttle... it doesn't it causes an acceleration and the reason you cap out at a given speed is that motor thrust goes down as speed goes up and drag goes up, so for a given prop rotation speed and airframe there is an equilibrium point between thrust that the motor is creating and the air drag on the aircraft. however the aircraft accelerates to that speed, it doesn't instantly speed up and the rate of acceleration will go down as it gets closer to the equilibrium speed (as the net force will be going down).