Official Freewing F/A-18C Hornet 90mm EDF Thread

[Hugh Wiedman]

Thanks Jandro 👍

I think I've actually got to the issues, I downed tools yesterday afternoon and went to the field. Got 3-flights in on the F-18 (5 on the L-39)

I put a 50 % exponential curve on the throttle

After around 3-minutes 30 seconds I landed with 60% left in the battery (I really didn't expect this). So with some mixed flying I reckon I can get over 5-minutes out of her

So, my conclusion is that given the power those motors are putting out, I must have inadvertantly been using much more throttle than I actually needed most of the time.

I suspect it's something to do with the power / rpm band for that motor/fan setup, a little like a the sweet spot on 2-stroke sports bike if I might use that analogy.

I'm going to use the same 50% throttle expo on the A-10 and am hoping it will significantly prolongate my flight times on that, in fact, I'm more optimistic that I will see a more dramatic change with the A-10.

Based on limited testing I would recommend people experiment with this, you can't really do any harm and with an exponential curve you've always got full power at the top of the sticks.

It's not been something I've done before on EDFs (I have done it on certain turbines that have had very distinct power band traits or spool-up characteristics but that is irrelevant here).

Famous last words I know, but I was really surprised by how she handles, in a good way, I really pushed my luck a couple of times (deliberately) flying close to the stall and she so far hasn't taken the bait. Not sure I'm going to move the CG back any further for now, for me she seems to sit on her tail nice enough in-flight (it's currently at 101mm).

Anyway... problem busted 👍

Andy

Veeery Interesting! Great that you got it worked out, knew that something was amiss on the short flight times, but I never even knew you could put expo in on the throttle. I'm using a Spektrum TX and never saw anywhere that I could dial in expo there, but then there's a lot of things on the TX that I have never fiddled with, so it could be there.

[DCORSAIR]

Yeah me too, interested in the expo throttle curve, something for sure I have never tried before, very interesting and I see your using Futaba like me so your info would be easy setting that part up.

[Airguardian]

I think I've actually got to the issues, I downed tools yesterday afternoon and went to the field. Got 3-flights in on the F-18 (5 on the L-39)

I put a 50 % exponential curve on the throttle (see photo below):

So, my conclusion is that given the power those motors are putting out, I must have inadvertantly been using much more throttle than I actually needed most of the time.

That's more like it!
Glad you sorted it out!

The expo curve idea is interesting although I'm more or less happy with mine being linear but may try it some day, FWIW. :)

[Aros]

Hmmm, I've never messed with throttle expo curves before...Is there a tutorial, aka "Throttle Curves For Dummies"? I have a DX18...I would like to try this out myself. Thanks for the info!

[The43rdHammer]

That sounds strange to me because the Hornet flies for quite longer than my average foamie jet. I typically clock between 4 and 5 min with my usual aerobatic shenanigans.
Something must be off!

Here's an uncut video for reference, featuring pretty throttle and aerobatic-intensive flights:

Flight times 3:45 - 4:05 - 3:30

Thanks Jandro 👍

I think I've actually got to the issues, I downed tools yesterday afternoon and went to the field. Got 3-flights in on the F-18 (5 on the L-39)

I put a 50 % exponential curve on the throttle (see photo below):



After around 3-minutes 30 seconds I landed with 60% left in the battery (I really didn't expect this). So with some mixed flying I reckon I can get over 5-minutes out of her:






So, my conclusion is that given the power those motors are putting out, I must have inadvertantly been using much more throttle than I actually needed most of the time.

I suspect it's something to do with the power / rpm band for that motor/fan setup, a little like a the sweet spot on 2-stroke sports bike if I might use that analogy.

I'm going to use the same 50% throttle expo on the A-10 and am hoping it will significantly prolongate my flight times on that, in fact, I'm more optimistic that I will see a more dramatic change with the A-10.

Based on limited testing I would recommend people experiment with this, you can't really do any harm and with an exponential curve you've always got full power at the top of the sticks.

It's not been something I've done before on EDFs (I have done it on certain turbines that have had very distinct power band traits or spool-up characteristics but that is irrelevant here).

Famous last words I know, but I was really surprised by how she handles, in a good way, I really pushed my luck a couple of times (deliberately) flying close to the stall and she so far hasn't taken the bait. Not sure I'm going to move the CG back any further for now, for me she seems to sit on her tail nice enough in-flight (it's currently at 101mm).

Anyway... problem busted 👍

Andy

[Hugh Wiedman]

To me this indicates the Admiral batteries have a higher series resistance the the RT & HRB batteries.

Are they the same/similar C rating? Significant difference in age or total cycles-to-date?

2814 W/117.1 A = approx 24 V (at the battery terminal)
2521 W/112.6 A = approx 22 V

Seems to point to ohmic losses inside the batteries.

2 V @ average 115 A = approx 17 mohm difference.

Absolutely the IR of each individual cell is higher in the Admiral than the RT/HRB/Hobbystar/Liperior/SCM, etc. etc. The current draw (Amps) and power (Watts) were measured using a GT Power meter connected between the tested battery and the tested EDF unit. The higher the watts, the more the thrust. The actual measured C of each specific battery (which I posted in my thread "Lipo Wars: Admiral vs HRB & RT) were measurements taken of over 100 different mah/C advertised rating/brands using the Progressive Internal Resistance Meter and C indicators. The algorithms in this meter are based upon the work done by Wayne Giles. All batteries were "relatively" same in age (mostly new to only 10 clycles), tested at 70 degrees (a very important constant in IR calculations/comparisons-probably the single biggest thing that can cause variations) and fully charged to 4.2 volts per cell. I've got a 6 page excel spreadsheet I created showing each battery (minimum of 6 of each brand and each mah/C to eliminate any single potential "bad" battery) comparing the advertised C to the actual tested C, the FoM (Figure of Merit-the higher the higher C discharge rate), the total IR for the battery and each specific cells amps and Internal Resistance. All I can say is I should have spent the 100's hours doing this flying instead of testing batteries!

That's a lot of electrical engineering speak (mostly way over my head), but on average, the Admiral 6000 50 C Pro's individual cells averaged 101 Amps to 112 Amps and the individual cells IR averaged 2.99 mohm to 3.55 (obviously the lower IR, the higher actual C) with the total IR of the battery ranging between 24.8 to 26.3. On the other hand, the RT (70C) and HRB (50C) (as well as other brands) had average Amps per cell in the 121 to 134 range, the individual cells IR in the 1.91 to 2.59 range and the total IR in the 17.8 to 21.5 range. Even the RT 6250 35C battery had numbers slightly better than the Admiral's. Liperiors were even better than RT & HRB and the few SCM's I've seen (although graphene) were much better. Only tested a few of the new Spektrum "Smart" batteries and frankly they weren't much better than the Admirals and just way over priced, IMO, but have some other interesting features that I really don't need. The consistency of each cell was also an important measurement in it's actual C measurement. I was able to "weed" out a couple "inferior" batteries within a specific brand and every new battery I get, I test it first to see how it compares to the exact same battery I already have. On several instances, I was shipped a battery that although individual cells were fairly consistent with each other, it was at least 15% below other exact same batteries in Amps and 20-25% higher in IR. Returned them and got a replacement that was more on par, so the meter did pay for itself.

[fredmdbud]

Battery: RT 5500 & HRB 6000
Current Draw: 117.1A
Power: 2814 Watts

Battery: Admiral 6000 Pro
Current Draw: 112.6A
Power: 2521 Watts

To me this indicates the Admiral batteries have a higher series resistance the the RT & HRB batteries.

Are they the same/similar C rating? Significant difference in age or total cycles-to-date?

2814 W/117.1 A = approx 24 V (at the battery terminal)
2521 W/112.6 A = approx 22 V

Seems to point to ohmic losses inside the batteries.

2 V @ average 115 A = approx 17 mohm difference.

[Hugh Wiedman]

Here are my provisional findings:

Current draw: 115A (stabilised)
Power: 2,450 Watts (stabilised)
Voltage at start of test: 25.02
Battery Admiral Pro 6S 6,000


Andy

Have no idea what this means or am able to draw any conclusions, but my power draws are a bit different on other batteries:

These are all with the 12 blade 1835 Kv inrunner so not sure how to compare to the 9 blade:

Battery: RT 5500 & HRB 6000
Current Draw: 117.1A
Power: 2814 Watts

Battery: Admiral 6000 Pro
Current Draw: 112.6A
Power: 2521 Watts

The Power draw is similar on my 12 blade and your 9 blade on the Admiral Pro, but a bit less on the current draw, but the Admiral is woefully less on both (>10%) when compared to other batteries. The HRB is also an advertised 50C and the RT is advertised at 70C. The Liperior 5000 45C and 6200 40C numbers are even higher than the HRB/RT for batteries costing $50 and $67 respectively, but don't have any of those in my inventory of 140 batteries and had to borrow them from a friend to compare. Gotta get me a few at some point, as well as would love to try out the SMC (Superior Matching Concepts-Graphene) batteries, slightly heavier and higher actual C costing in the neighborhood of $95. The Admiral Pros run us about $125 last I checked, the RT's about the same or a little less and the HRB's around $85.

[Mizer67]

I set my timer with the Hornet to 3:00 on the 9-bld to land at 3.78's.

I used to set my timer on the F-22 to 2:45 on the 12-bld to land at 3.78's.

Both are with 5000's and I usually land within a few tenths at most on the battery voltage using the above. I am not light on the throttle with either and don't use any batteries >5000 mah.

If I wanted to lick the bottom of the barrel on mah, I could probably extend both by 30 seconds flying normally, for me.

[Airguardian]

There’s no issues with thrust or physical performance that I can complain about, but it does seem to drain the juice extremely quickly (for me).

What flight times do you get?

Are my expectations too high?

Andy

That sounds strange to me because the Hornet flies for quite longer than my average foamie jet. I typically clock between 4 and 5 min with my usual aerobatic shenanigans.
Something must be off!

Here's an uncut video for reference, featuring pretty throttle and aerobatic-intensive flights:

Flight times 3:45 - 4:05 - 3:30

[The43rdHammer]

Here are my provisional findings:

Current draw: 115A (stabilised)
Power: 2,450 Watts (stabilised)
Voltage at start of test: 25.02
Battery Admiral Pro 6S 6,000

This kind of current draw would in fact only give a flight time of a little over 3-minutes at full chat.

Allow say +30% for throttle management, that takes you to 4-minutes (roughly what was being discussed on here).

I believe the motors and the aircarft are doing what they should, but that a point of inflection is being reached whereby thrust over a certain level is merely using up MaH and not actually making the aircraft fly any better.

The solution is a simple one, in my opinion, and that is to change the throttle curve, which I have done, to an exponential curve to help me better manage the energy consumption.

Will report back further in due course.

Andy

[Hugh Wiedman]

🤣



There's definitely something going with my 9-blade setup, the Admiral Pro 6000 batteries are warm but not hot and they are down to less than 30% after 2:30-3:00 minutes, that's not right.

I'm not the first to notice it on this forum.

Will take a look over the weekend, but appreciate the feedback on the numbers as I now have a datapoint to benchmark against 👍

Andy

That just doesn't sound right. I'm also getting at least 4 minutes on that same 12 blade inrunner in both of my F-4's, so 3:00 or less on the F-18 is definitely not right. I also remember (I think) that you only get 3:00 on the A-10 with 2 6000's, and I get over 5 minutes on 2 RT 6250's. And to add even more confusion to the mix, I used to fly the F-18 on a Roaring Top 6250 mah 35C battery (795g) with the old 9 blade 3748-1750 Kv Outrunner and would get almost 5 minutes of flight time. With the outrunner, a higher C battery had almost zero impact on the EDF thrust output over a lower C battery, so I could use that lighter and lower C battery with no problem.

Once I changed to the Inrunner, that 35C battery resulted in about 7% lest thrust than say a 50-70 C battery, so I ended up going with the HRB 6000 (825g) 50C-100C burst for a little better performance. Unfortunately, the Admiral 6000 Pro 50 C (836g) is heavier than the other 2 (HRB/RT) and the "Actual" C as tested by my IR meter (Progressive IR & C Meter) came out with an actual C of 25C (same as the RT 6250 35C) and well below the HRB 50C which tested at 35C and produced almost 9% more thrust. I get slightly less flight time with the 12 blade inrunner than I did with the 9 blade outrunner, but then I've also been flying it at least 25-40% "faster" while still using the same throttle positions. I could cut back the throttle so it would fly the same, but where's the fun in that!

You may have missed it, but I started a thread maybe a year ago called "Lipo Wars", where I tested a lot of different batteries of differing mah and C rating for actual C, and also tested them on power draws and thrust output on different outrunners and inrunners. Unfortunately the Admiral's tested at the bottom of the list and at the top of the price curve. And I have literally tons of Admiral 6000's / 5000's / 4000's / others, so not too happy about the results. In general though, their lower mah and lower C rated batteries are closer to the advertised labels. But I also found that outrunners don't benefit as much from a higher C battery but inrunners definitely do.

I don't pretend to know a lot about different batteries and different EDF's, only that I've tested a bunch and there is a big difference with some. An interesting example is that with one brand of 5000 mah 40C in my FL Spitfire, I get 7 minutes of flight time. With a different brand (same mah and C-but tested much higher than the first) I now get 9:30 of flight time, flying the exact same "routine". So I do believe that the battery makes a big difference. I've gotten to the point where each of my EDF's uses a different specific battery, based upon it's weight/mah/Actual C and what is the "driving" factor in each aircraft. As I've said before, the strangest one is my F-16 with the 12 blade inrunner. It actually flies better with an 8000 mah 100C battery than with a 6000 mah 50C HRB, despite the additional weight, but gives me over 5 minutes of flight time-where the 6000 is at 3:40.

But I used to have more fun when I just threw a battery in of whatever was handy, didn't even know what CG stood for and put my RX antennae wherever it fit right along side the battery (seems like last week ). Now those concerns/issues plague my every thought! Something to be said for "Ignorance is Bliss"!

[The43rdHammer]

.... I do like the sound of a 12 blade a bit better, but then I've always been a bit superficial.

🤣

.... With the 12 blade, I'm over 4 minutes of pretty aggressive flying using a HRB 6000 (landing with at least 30% battery capacity remaining) and can easily go to 4:30 or more ...

There's definitely something going with my 9-blade setup, the Admiral Pro 6000 batteries are warm but not hot and they are down to less than 30% after 2:30-3:00 minutes, that's not right.

I'm not the first to notice it on this forum.

Will take a look over the weekend, but appreciate the feedback on the numbers as I now have a datapoint to benchmark against 👍

Andy

[Hugh Wiedman]

There’s no issues with thrust or physical performance that I can complain about, but it does seem to drain the juice extremely quickly (for me).

What flight times do you get?

Are my expectations too high?

Andy

With the 12 blade, I'm over 4 minutes of pretty aggressive flying using a HRB 6000 (landing with at least 30% battery capacity remaining) and can easily go to 4:30 or more. But for me, the biggest difference is take-off distance on grass, less than 100 feet (even with all my extra weight). If I flew off of asphalt or a hard surface, it would probably be a different story and the 9 blade would be fine (although we have a 1000 foot runway, so who cares). I do like the sound of a 12 blade a bit better, but then I've always been a bit superficial.

[The43rdHammer]

FWIW, I like the 'high performance' 1900kv 9B inrunner setup :)

There’s no issues with thrust or physical performance that I can complain about, but it does seem to drain the juice extremely quickly (for me).

What flight times do you get?

Are my expectations too high?

Andy

[Mizer67]

I have a spare 12B 1835kv 90mm in my parts box. It's my favorite Freewing 90mm EDF.

That being said, I've got the 1900kv 9B in the F-18 and I don't mind it, at least not enough to spend the 5 min. to swap it out.

I don't think the 1835kv 12B is good for any additional top-end speed. In fact, based on what I've seen it's down a % or two. Thrust is the big difference. You tend to pay for the extra thrust with slightly shorter flight times in my experience with that motor in the F-22.

I have the new FMS 1850kv 12B 90mm and it's a good alternative to the 1835kv 12B FW EDF, but does take a little fitting. If you like the FW, the FMS is incrementally better, so it might be worth checking out if you're ever in the market for another. It's less expensive as well.

[Airguardian]

FWIW, I like the 'high performance' 1900kv 9B inrunner setup :)

[Aros]

The fact that I am an Expert at crashing these jets? LOL!!

[The43rdHammer]

Aros I bet you'll be looking forwards to the live show tomorrow (not) ... I wonder what all the questions will be about 🙃

I'm on your side big man.

Andy

[Hugh Wiedman]

I'm also discovering I'm not a big "fan" (nice, lol) of the stock 9-Blade inrunner in this particular model. Just doesn't have the scoot I would like so I will be heeding Hugh Wiedman's advice and snag one of those coveted 12 Blade power systems for her. Just gotta pad the ol' coffers for a bit first.

Just picked up another 12 blade last night so my entire fleet of 90mm aircraft has now been "beastified".

But I have no experience with the 9 blade inrunner, so I may be comparing apples to oranges.