Official Freewing JAS 39 Gripen 80mm EDF Jet

[Mizer67]

Sorry, haven't measured other than with my eyes and ears.

I put together my Gripen stock setup to run a quick test your experience with increasing the timing on the ESC.

• On Medium timing at 23.08V, I recorded 1944W and 90A draw using the stock 9-bld inrunner and Hobbywing ESC.
• On High timing at 23.06V, I recorded 2099W and 97A draw
• So there's a 7% increase in watts and amps going from Medium to High timing

I did not record static thrust back to back to determine if the extra power was translating into extra thrust or speed, but there does appear to be an increase on the face of it, although your stock ESC might not be up to the task as I imagine on 25V+ at peak that you'll be over the 100A limit.

[Airguardian]

Well, there it is.
If someone does static thrust tests, please let us know!


Bet a good part of that DOES translate into thrust.

[Mizer67]

Well, there it is.
If someone does static thrust tests, please let us know!


Bet a good part of that DOES translate into thrust.

Did my best with my scale and came away with 2400 grams (approximately) on high and 2300 grams (approximately) on medium timing at 23V.

So a ~4% increase in static thrust give or take for ~7% increase in amps. It's difficult to measure with precision on my scale and did fluctuate, but was always higher on "high" timing.

[kallend]

If you downloaded the STL files for the 1:9 scale Sidewinder from my Thingiverse collection, I have made some minor changes (improvements, I think).

[KevinMar]

If you downloaded the STL files for the 1:9 scale Sidewinder from my Thingiverse collection, I have made some minor changes (improvements, I think).

Just finished gluing mine together, what are the changes?

[jkallend]

Just finished gluing mine together, what are the changes?

Added (fake, of course) rollerons.

[flightaddict]

Hi guys,

I've set mine up with a FrSky S8R allowing the gyro to do the elevon mixes with normal stabilization and auto level as a recovery option and used the Ale2 and Ele2 channels from the S8R to run the canards by reversing the ELE2 channel so that both canards go in same direction operating only in pitch through and mix. The Ale2 Ele2 are not stabilized, just fed through. Now I'm thinking of putting the ALe2 and Ele2 channels through a HobbyEagle A3 Pro to function as Airguardian described to work in stabilization mode to keep the airflow correct over the main wing. I will fly it with a switch so that the canards are either manual positive/negative deflections with up/down elevator, or pitch plus stabilization or just stabilization with pitch input from stick locked to stick center,(1550uS). Does anyone see any issues with this? Thanks for any help.

[Mizer67]

Well, there it is.
If someone does static thrust tests, please let us know!


Bet a good part of that DOES translate into thrust.

I dropped my Gripen EDF + ESC into my A-4 Skyhawk. I used the FMS EDF I had planned for the Skyhawk in my Gripen until I get my 8S setup sorted.

The Skyhawk is my slowest plane, so the extra speed from the 1920kv unit I thought would do it some good. Because it's so slow and draggy, it might not be the best test platform for this run, but I did run some back-to-back speed tests to see if "High" timing made a difference in flight. This is all from level flight @ sea level approximately. Temp was 65F or so, so not far from a standard day. Although very humid and foggy this morning.

Near as I could determine:

High timing: 96 mph
Medium timing: 92-94 mph

High timing costs an extra ~20-30 seconds of flight time to land at 3.78.

I'd say it's a marginal result and well within the margin of error for the test.

[Evan D]

What were the numbers for the stock A-4 set up? Was there a significant difference, better or worse? I ask because in the Avanti threads some people say the new inrunner is a decrease in performance and others say an increase.

[kallend]

What were the numbers for the stock A-4 set up? Was there a significant difference, better or worse? I ask because in the Avanti threads some people say the new inrunner is a decrease in performance and others say an increase.

I have been rather disappointed with the Freewing inrunner performance in both the 70 and 80mm sizes. And the 80mm inrunner's motor diameter of 36mm sure blocks a lot of area, It's the same diameter as their 90mm motor only shorter. The FMS inrunner motor is only 32mm in diameter.

[kallend]

Duplicate - ignore.

[Mizer67]

What were the numbers for the stock A-4 set up? Was there a significant difference, better or worse? I ask because in the Avanti threads some people say the new inrunner is a decrease in performance and others say an increase.

While I bought the A-4 ARF Plus, I did have an 1857kv 12-bld inrunner full setup in the A-4 briefly that I had as a takeoff from another plane and didn't see a significant difference.

Speed readings were 89-94 mph, all taken on medium timing in that case, in level flight.

My take is that any increase in timing, at least on the A-4, doesn't make a significant enough difference to notice in flight and does cost some in flight time. I think any difference in top speed between the 1920kv and the 1857kv prior is also in the noise and may depend on individual motor wind. The 1920kv motor might be good for perhaps a couple of mph at most depending on the plane and motor.

[Marktur]

It’s flying day!!! Just wondering what is the best way to use the canards as air brakes like the full scale jet? That’s a lot of down throw for normal fight. I found a set of JP wheels with brakes laying around... they’re heavy but I may be able to use them and remove some lead to keep the cg. I’m thinking an independent switch or slider and mixing in exaggerated canard down with up Elevon. Thoughts?

[Evan D]

I adjusted mine so the full up throw was at the limits of the servos in one direction so I could get "to the stops" down for air brakes. I also linked the correct amount of up elevon so if I hit it in flight it would still fly.


.

[kallend]

It’s flying day!!! Just wondering what is the best way to use the canards as air brakes like the full scale jet?

I offset the neutral mechanically to give a lot of 'down' and then adjusted sub-trim (a lot) to bring the canards back to the correct flying position with the stick centered.

I then mixed into the canard enough 'down' from the chosen airbrake switch to give maximum down deflection. The airbrake switch is only enabled with the gear down and the throttle closed. The airbrake switch I chose is a 3-position, with 2 positions being 'off''.

I suppose I could accidentally activate in the air, which would be bad, but it would take several mistakes to make this happen and I could only blame myself.

I've been using the same scheme on my Eurofighter.

[Pogo]

While I bought the A-4 ARF Plus, I did have an 1857kv 12-bld inrunner full setup in the A-4 briefly that I had as a takeoff from another plane and didn't see a significant difference.

Speed readings were 89-94 mph, all taken on medium timing in that case, in level flight.

My take is that any increase in timing, at least on the A-4, doesn't make a significant enough difference to notice in flight and does cost some in flight time. I think any difference in top speed between the 1920kv and the 1857kv prior is also in the noise and may depend on individual motor wind. The 1920kv motor might be good for perhaps a couple of mph at most depending on the plane and motor.

Mizer, thank you for doing your earlier Amp and thrust and now these speed measurements- as you've concluded the slight increase in thrust and speed don't seem worth the reduced flight time. It's pretty much winter here and mine's apart for some mods so this experimentation would've had to wait till spring.
Tom

[Mizer67]

Mizer, thank you for doing your earlier Amp and thrust and now these speed measurements- as you've concluded the slight increase in thrust and speed don't seem worth the reduced flight time. It's pretty much winter here and mine's apart for some mods so this experimentation would've had to wait till spring.
Tom

Yes, that's true. One of the benefits to living in Florida for sure. I'd peg the increased speed at ~2 mph from the timing on the A-4, or about a 4% increase. Although, it is difficult with the instrumentation I have to be that precise but neither my eyes nor ears could tell any real difference flying it back to back. Still that kind of result (7% amps = 4% more thrust and 4% more speed) matches what I'd expect given the speed vs. drag curve.

However, on a plane with less parasitic drag, you might see more benefit. I'm not really sure where to peg the Gripen in that respect, but mine seems to have a top speed roughly equal to my Mig-21 on the same power setup, so it's more slippery than the A-4, which may lead to seeing a larger benefit from the timing change.

That being said, I'm not inclined to put the stock power plant back into the Gripen to test it out. I may try it on the FMS 2100kv fan just to see the result or my 8S setup when I get my new batteries in.

[kallend]

While I bought the A-4 ARF Plus, I did have an 1857kv 12-bld inrunner full setup in the A-4 briefly that I had as a takeoff from another plane and didn't see a significant difference.

Speed readings were 89-94 mph, all taken on medium timing in that case, in level flight.

My take is that any increase in timing, at least on the A-4, doesn't make a significant enough difference to notice in flight and does cost some in flight time. I think any difference in top speed between the 1920kv and the 1857kv prior is also in the noise and may depend on individual motor wind. The 1920kv motor might be good for perhaps a couple of mph at most depending on the plane and motor.

My **guess** is that you would see a more noticeable improvement in climb rate than in top speed.

[4qr1hu9n7]

Nice jet. But. Freewing could have added the second bearing on the card axles. Also I find that the main landing gear door hinge pins break extremely easily. I replaced them with carbon pins. I will be using the 4000 mah smart battery. It is pushed as far back as possible. Plus I had to add ballast to bring this plane within the balance range.

[kallend]

Nice jet. But. Freewing could have added the second bearing on the card axles. Also I find that the main landing gear door hinge pins break extremely easily. I replaced them with carbon pins. I will be using the 4000 mah smart battery. It is pushed as far back as possible. Plus I had to add ballast to bring this plane within the balance range.

Did you see my heavy nozzle? It's a way of adding tailweight (up to 120g) without affecting the appearance (in fact it probably improves it).

https://www.thingiverse.com/thing:4650359