Who agrees with me?

[CVA59]

So, some of you know that I have recently returned to flying/building after a 8+ year hiatus. My return has been with getting into EDF's for the first time and anything electric. As I have said before, I have always flown glow fuel prop planes. I recall flying for 8 minutes or more and landing because I was ready to land and not because I am being forced to land like it is now. So, my "observation" is this; am I the only one who cannot understand why we only get 3 minutes +/- on a 4S or 6S pack in a EDF? We live in a world where technology on most all fronts is beyond comprehension in some case yet the age old "battery" seems to still be 10-15 years behind. Don't get me wrong, I am thankful we do get at least 3 minutes or so nowadays because it used to be shorter times than that. I don't really want to go back to fuel mainly because of the mess. Plus, I love the way the EDF's look, fly and sound so that is not an option for me anymore.

I recently maiden-ed my 4S 70mm Rebel for the first time. I flew several times w/o incident but it "seemed" within a matter of seconds of takeoff my 3 minute timer was beeping at me. I had a fellow flier double check me and every time and the timer was accurate. It felt like no sooner than I was airborne and started getting into a rhythm, I hear my timer beeping. YES, all packs were fully charged and double checked by my meter and a fellow flier so it was not a pack charge issue. I did get the full 3 minutes out of every pack so I know they were at full capacity.

I guess I am just surprised at with all this world of technology, why can't someone design an electric system that will allow for at least 6-8 minutes of flying or more?

[Elbee]

CVA59, I figured if battery tech was available that was affordable and safe, we'd have it. Capacity physics is what I think is the limiting factor. Weight v Horsepower. Then there's the size thing, i.e., wingspan v wing loading. I would like to see longer flight times, as well. Again, those were the days when you needed a break so you landed. Hope you're on target and there are greater capacities with tolerable weight ratios on the horizon. Best, LB

[Skyboom]

Or motors that use less amperage and create same amount of thrust. I can see it in the near future. It's keeping it to a price point we can afford.

[fhhuber]

The issue with short EDF flights is due to multiple factors. Mainly it comes down to weight.

EDF is an inefficient way to power a model. To get the same performance (all else being the same) using an EDF as a conventional 2 blade prop you need appx 1.5 times the power. You are adding thrust tube and inlet drag on the airflow you are trying to use for thrust. The high rm of the EDF fan creates massive friction on the fan itself (some of the tip drag is mitigated by the fan shroud almost preventing formation of tip vortices on the blades or it would be worse)

This means you have to carry 1.5 times the battery weight if you want the same duration and performance. The EDF is already going to suffer appx 30% loss of duration because the added weight would 100% prevent the same performance.

The the fan shroud itself is heavy... to compensate for that weight, you have to carry less battery capacity vs the watt demand of the power system. So you lose more duration.

Then we demand higher performance from an EDF model than from most conventional prop models. Jets "are supposed to be fast" That means we are demanding more amps from the smaller batteries.... Pwer needed to increase speed is a CUBED relationship. 2 times the speed need 8 times the watts. But we are already demanding 1.5 times the watts. 1.5 times the speed of the prop plane you need 1.5 * 1.5^3 power vs the conventional prop.... slightly more than 5 times the power and we have a SMALLER battery (if we want the same takeoff weight for the same size airplane)

The EDF models end up heavier because of the EDF and wanting more than 2 minute flights... and more weight needs more power just to stay in the air. Even when flown "economy mode" we are fighting the inefficiency of the EDF and a heavier airplane. So you cant fly it at moderate throttle as long. You are using a smaller battery and demanding more watts.

Carry enough battery to get the same flight time as the conventional 2 blade prop model and... your minimum takeoff speed will be higher than the speed you can attain with wheels on pavement.

*****************

When we get better batteries for EDF and better motors for EDF... we get the better batteries and motors for the conventional prop planes.
EDF will always have shorter flight time.

[Woodcock]

I get pretty good flight times in my EDF's. But I'm not a speed demon like some, but ya got to take off. Unlike many here, I honestly enjoy just flying around using as little battery as I can manage.

So I think smoothing & polishing the air intake, fan shroud, fan blades, & exaust will go a long way to extend your flight times. Not an easy thing, but think about it. Have you ever bought a new room fan? You ever notice how well it blows when it's new, clean and shiny vs. after it gets just a little dusty. I've often wondered why no one ever mentions this? In the early days of Nitro Ducted Fans when building a new plane we always focused on finishing the inside air channels just a smooth and shiny as possible. After all we almost always had a big nitro engine & expansion chamber in the flow tube blocking plenty of air already.

I've thought about it. I haven't figured out how to attack this in my EDF's yet. The way pretty much all the Jet models are these days, make it almost impossible to do anything to smooth the internal flow channels. Foam has all those little injection flowers, plus is very porous. I'm certain it makes it very inefficient. The new EDF Units blow so much harder than the old gas ones is what overcomes this.

In short if you smooth & polish the internal air channels, it makes it more efficient allow a lower throttle setting to attain the same performance. Now who's going to do it? LOL I think I'll just suffer thru with the shorter flight times.

Best Regards
Woody

Yea, I do agree with you mate. I would love better flight times for sure.

[F22trainer]

My dad’s VIP squadron would polish and wax the planes every year to use up the budget money. They also documented the airplanes always increased True airspeed by around 5 knots and used less fuel for trips. Check out NASA research at Dryden site.

[CVA59]

Thanks for the input guys. Sometimes it is just hard to overcome the physics of something like this to the degree that is works mostly in our favor. I hope some time not too far away the EDF flight times will improve and such that it won't break the bank. LOVE the EDF's just wish I could have my cake and eat it too, LOL.

So, let me throw this out, would it be possible to use a small RX pack for the control surfaces and leave the flight pack for strictly the motor? I know that would add the weight of another smaller pack but in addition, if the flight pack lost all it's juice and I could not get down in time at least I would have the control surfaces still operable and hopefully glide it in as much as possible. Would this be doable in a EDF or totally impractical?

[Woodcock]

Thanks for the input guys. Sometimes it is just hard to overcome the physics of something like this to the degree that is works mostly in our favor. I hope some time not too far away the EDF flight times will improve and such that it won't break the bank. LOVE the EDF's just wish I could have my cake and eat it too, LOL.

So, let me throw this out, would it be possible to use a small RX pack for the control surfaces and leave the flight pack for strictly the motor? I know that would add the weight of another smaller pack but in addition, if the flight pack lost all it's juice and I could not get down in time at least I would have the control surfaces still operable and hopefully glide it in as much as possible. Would this be doable in a EDF or totally impractical?

I want to say lots of people do that, but as I don't know how many, I think that's a good idea. Needs to be something larger in my opinion, probably not to practical in say a single 64mm EDF.

Woody

[rifleman_btx]

I fly my FMS FA18F model for 6 minutes comfortably. Not a speed demon but its still fun to me.

[Hoomi]

The fact that we have electric planes at all is a testament to the advances in batteries and motors. When I was a teenager back in the 70s, electric flight wasn't a practical option. Even with alkaline batteries, which were the best commercially available at the time, the amount of battery weight to power flight would have been too great for a model plane to lift. Even when NiMH came into its own in the 80s, it was still barely adequate for much in the way of powered flight. LiPo and Lithium Ion batteries now offer sufficient output power to weight ratio that we can not only get an airplane off the ground, but they can actually power SCALE jet models.

Y'all remember the early "jets" for RC, I'm sure. Most were glow-engine powered with a propeller, and semi-scale wings to provide enough lift to fly in any kind of practical sense. They looked kind of like the jet they were modeled after, but nothing that could have been called a scale model. (Imagine trying to make a flyable F-104 Starfighter without LiPo and brushless motor EDF technology, or without dropping big bucks on a scale jet engine).

I suspect we WILL see continued advancements in this area, but for now, this relative newbie is thrilled with what we have right now, compared to what used to be available.

[F22trainer]

The fact that we have electric planes at all is a testament to the advances in batteries and motors. When I was a teenager back in the 70s, electric flight wasn't a practical option. Even with alkaline batteries, which were the best commercially available at the time, the amount of battery weight to power flight would have been too great for a model plane to lift. Even when NiMH came into its own in the 80s, it was still barely adequate for much in the way of powered flight. LiPo and Lithium Ion batteries now offer sufficient output power to weight ratio that we can not only get an airplane off the ground, but they can actually power SCALE jet models.

Y'all remember the early "jets" for RC, I'm sure. Most were glow-engine powered with a propeller, and semi-scale wings to provide enough lift to fly in any kind of practical sense. They looked kind of like the jet they were modeled after, but nothing that could have been called a scale model. (Imagine trying to make a flyable F-104 Starfighter without LiPo and brushless motor EDF technology, or without dropping big bucks on a scale jet engine).

I suspect we WILL see continued advancements in this area, but for now, this relative newbie is thrilled with what we have right now, compared to what used to be available.

In mid-80’s, an electric ducted fan was the equivalent of a standing joke, used frequently by writers at RCModelers magazine. Astro Cobalt motors were just beginning to scratch the surface...
doah, I think there’s a joke there too.
And, that was about the same time I bought this model with an OS 20 and World Engines TX/RX system for $100.
I have more flights on it now, than I ever had when it was gasser and all of them longer than any flight with the 2 stroker, plus I was never able to do a touch and go with it until it got converted because the engine always quit about 4 minutes in flight- every landing I did was dead stick!
No wonder I got proficient with gliders and had more fun.

[Woodcock]

In mid-80’s, an electric ducted fan was the equivalent of a standing joke, used frequently by writers at RCModelers magazine. Astro Cobalt motors were just beginning to scratch the surface...
doah, I think there’s a joke there too.
And, that was about the same time I bought this model with an OS 20 and World Engines TX/RX system for $100.
I have more flights on it now, than I ever had when it was gasser and all of them longer than any flight with the 2 striker, plus I was never able to do a touch and go with it until it got converted because the engine always quit about 4 minutes in flight- every landing I did was dead stick!
No wonder I got proficient with gliders and had more fun.

Trainer, my very first RC Model was a Gental Lady, LOL. Ya know when I went to powered jobs, I couldn't believe how easy they were. No looking for lift, trying to plan a landing on a rocky hill. Dodging all the hang gliders, (I would usually just land and wait, or leave). I loved it.

Woody

[fhhuber]

The move to brushless motors vs rare earth brushed saved about 30% of the motor weight for the same power. In reality that's less than changing from a heavy spinner to a light one.

LiPo on the other hand allowed storing twice the watt-hr of energy in the same space at half the weight of NiCd or NiMh. Plus allowed far higher current delivery. Saving half the weight f the heaviest single thing in the airplane plus doubling duration or power is huge.

My first experience with LiPo was dropping in a 2S LiPo in a motorized sailplane, nt changing the ESC or motor. I had to add lead weight for CG and still got triple the flight time. This is back when 8C LiPo were considered pretty good and 20C LiPos were a dream.

Modern LiPos are lighter and more compact than those of the early 2000's. I still have a 3S 1800 mah 8C (which can still deliver 2 amps for 30 min, but wont deliver 3 amps. Not bad for an appx 15 year old pack). This old pack is physically larger and heavier than a new 3S 3300 mah 35C I had delivered 3 weeks ago.

We don't notice the tiny incremental improvements to the LiPo every year. They ARE getting better.

Also about 18 months to 2 years ago, Castle released a firmware update that when loaded on my Phoenix ICE 100 ESC gave a noticeable improvement in both top airspeed and flight duration. NO HARDWARE CHANGE AT ALL. And the batteries were cooler at the end of the flight.
I like higher efficiency at no charge....

I play with altering the "duct" passages in foam models. Usually the only thing that really helps is getting better air intake to the EDF. Sometimes the difference is marginal, sometimes its extreme.

Art Tech had a F-18 that I bought that had a 900 mah 10C 3S in front of the nosewheel. The poor thing could barely take off. Struggle to get it above 100 ft so I could get the nose down and after a brief dive it got much happier. However any maneuver that bled off airspeed was a very bad idea.
After some educated guess carving at the tiny cheater hole slots, carving a hatch behind the nosewheel for a 1800 mah 15C 3S LiPo (double the battery weight but far better current delivery) and pretty much no other changes the thing could lift off comfortably at 3/4 throttle into a 45 deg climb-out and at full throttle the only thing I had to worry about was G forces taking off the horizontal stabs. (eventually even the CF reinforcements I inserted failed, ending the airplane)
I told Art Tech about the modifications and,,, their next version had the 1800 mah behind the nosewheel, but they hadn't fixed the cheater holes.

[icepirate3]

Something I do to ease the pain of the short flights is to always have at least 1 or 2 props that give me the long flight times and fly the EDF's in between. I have also brought nothing but EDF's to the field and had a blast! A lot of it has to do with your mindset going into each flight I think. My flights usually consist of 2 WOT passes with loops, rolls, or high alpha's on the downwind. Or with the Hawk I have been working on knife edge's and 8 point rolls and can squeeze out 5 minutes on a 4000mah pack with 3.8 remaining pretty consistently. Watching some of Gooniac33's vids he is getting some very impressive flight times out of his FMS F/A18. Now that I have accepted the flight times I get, especially out of the larger jets I am fine with it. 3 minutes of intensity is all my brain can handle anyway.

[Jhnybgd]

Something I do to ease the pain of the short flights is to always have at least 1 or 2 props that give me the long flight times and fly the EDF's in between. I have also brought nothing but EDF's to the field and had a blast! A lot of it has to do with your mindset going into each flight I think. My flights usually consist of 2 WOT passes with loops, rolls, or high alpha's on the downwind. Or with the Hawk I have been working on knife edge's and 8 point rolls and can squeeze out 5 minutes on a 4000mah pack with 3.8 remaining pretty consistently. Watching some of Gooniac33's vids he is getting some very impressive flight times out of his FMS F/A18. Now that I have accepted the flight times I get, especially out of the larger jets I am fine with it. 3 minutes of intensity is all my brain can handle anyway.

Agreed!
I fly em hard for 3 then land...I'm worn out.
I can get 4:30 out of my 8S F4 but normally land at the 3:30 mark.

Now the Eflite Viper is so nice to fly I would like another couple minutes with it,although I am able to squeeze 4 minutes from my 3300mah,I usually fly to hard and land at 3.

[CVA59]

Thanks guys. I know it is all in my perceptions. I thinking on my next outing I will just fly, take a short break and fly again. I have been flying pretty much back to back and that really makes the times go by quickly.

One of my issues is a place to fly the EDF's. We have small club here but it is bumpy grass and I don't like flying there even with my prop planes. The good side of that club is that there are a few other fliers to talk to in between flights to pass some time. Right now I have been flying alone at our sports complex and a very big Church parking lot as long as no one is present or even close by. I am trying to start a new club here but R/C planes around here seem to have lost most of its following from a few years ago.

Otherwise, I will keeping buying packs as I can afford it.

[Valkpilot]

Agreed!
I fly em hard for 3 then land...I'm worn out.
I can get 4:30 out of my 8S F4 but normally land at the 3:30 mark.

Now the Eflite Viper is so nice to fly I would like another couple minutes with it,although I am able to squeeze 4 minutes from my 3300mah,I usually fly to hard and land at 3.

Where you fly can also be a mitigating factor. Most of the places I see in videos are nice wide open spaces of which I am extremely jealous of, so you don't have to deal with high trees, 20 ft drop-offs at the end of the runway which lead into heavy brush(see attachment). Add to this a walking trail under one end of the runway, and people who can't wrap their heads around the fact that there's a reason for all the warning signs, three minutes is quite a bit of time.

[CVA59]

Where you fly can also be a mitigating factor. Most of the places I see in videos are nice wide open spaces of which I am extremely jealous of, so you don't have to deal with high trees, 20 ft drop-offs at the end of the runway which lead into heavy brush(see attachment). Add to this a walking trail under one end of the runway, and people who can't wrap their heads around the fact that there's a reason for all the warning signs, three minutes is quite a bit of time.

Yes, both places I fly I have to literally drop it in carrier landing style to avoid trees and power lines. It's not bad but a little nerve racking at times. I am actively hunting for a more EDF friendly place to fly.

[xviper]

I last flew in the late 60's and it was all "glow". Life got in the way and I didn't pick it up again till earlier this decade when electrics started getting big. It made getting back so much easier (and quieter and cleaner). My first EDF was an exciting experience and every flight was "pedal to the metal" and didn't last long. That was fine by me because 3 minutes of hard butt clenching was plenty. As I got more experienced, I learned to back off and fly in a more relaxed way and was able to stretch out the flight time but flying a jet at lumbering paces wasn't all that fun so each flight was a mix of throttle use but I was still satisfied with 4 minutes or so. I even experimented with my Avanti S, flying it like an old lady driving to church on Sunday. I got nearly 10 minutes out of it and I could have gone a couple minutes longer but I was so bored, I could have taken a quick nap. I don't fly like that - ever.
I believe there is battery technology out there right now that would allow us to fly for much longer times but that tech is still cutting edge and the price for such batteries would be prohibitive and I wouldn't buy them anyway. I am quite happy and satisfied with the state of RC electric flight as it is now. I have no need to fly for 10 minutes each time on each plane. I usually take several planes with me and flying each one for 4 to 5 minutes twice is plenty for me. 8 to 12 flights per day, sometimes 5 days a week is just fine.

[CVA59]

I last flew in the late 60's and it was all "glow". Life got in the way and I didn't pick it up again till earlier this decade when electrics started getting big. It made getting back so much easier (and quieter and cleaner). My first EDF was an exciting experience and every flight was "pedal to the metal" and didn't last long. That was fine by me because 3 minutes of hard butt clenching was plenty. As I got more experienced, I learned to back off and fly in a more relaxed way and was able to stretch out the flight time but flying a jet at lumbering paces wasn't all that fun so each flight was a mix of throttle use but I was still satisfied with 4 minutes or so. I even experimented with my Avanti S, flying it like an old lady driving to church on Sunday. I got nearly 10 minutes out of it and I could have gone a couple minutes longer but I was so bored, I could have taken a quick nap. I don't fly like that - ever.
I believe there is battery technology out there right now that would allow us to fly for much longer times but that tech is still cutting edge and the price for such batteries would be prohibitive and I wouldn't buy them anyway. I am quite happy and satisfied with the state of RC electric flight as it is now. I have no need to fly for 10 minutes each time on each plane. I usually take several planes with me and flying each one for 4 to 5 minutes twice is plenty for me. 8 to 12 flights per day, sometimes 5 days a week is just fine.

Wow, I cannot imagine flying 5 days a week. I am very happy with the experience even if it is only 3+/- minutes. I just wish it had at least 6-8 minutes each flight to get it all out of my system, LOL.

So, having said all they we have discussed here. Where do you guys speculate the battery technology will be in another 5-10 years and will it even be affordable? When would you guys draw the line of the cost of EDF's being too much?