Official Freewing JAS 39 Gripen 80mm EDF Jet

[Pogo]

That looks good. It's amazing what you can do with common materials. My AL-37 is flying around with two margarine containers as fake nozzle extensions. :-)

I know, right? Enjoyed the video Harold- great flying. Did you ask about that scribing tool?-can't seem to find it now. Here's a link:

https://www.micromark.com/Panel-Scriber?gclid=CjwKCAiAlNf-BRB_EiwA2osbxSEPos7ZmwJdTFdrS9ArPPWVVNmMiW72tHoa59Zgv0OFMoaNrEuY_BoCt_MQAvD_BwE

Tom

[HaroldAnderson]

Great job indeed!
Why the landing gear down though?

It will fly slower with them down and seems a little more stable when making turns in high alpha. Try it! As an added bonus if you get too low and slow it turns into a touch and go instead of a belly landing followed by the 'walk of shame'. ;-)

[Mizer67]

It will fly slower with them down and seems a little more stable when making turns in high alpha. Try it! As an added bonus if you get too low and slow it turns into a touch and go instead of a belly landing followed by the 'walk of shame'. ;-)

I agree. I've mentioned in other threads that the main gear doors seem to provide some extra lift due to how they're shaped.

[Airguardian]

It will fly slower with them down and seems a little more stable when making turns in high alpha. Try it! As an added bonus if you get too low and slow it turns into a touch and go instead of a belly landing followed by the 'walk of shame'. ;-)

Very interesting... thanks!

I had one such 'walk of shame' today, btw...
Stalled due to excess AoA (nose-heavy CG and lack of thrust didn't help) and hit the dirt.
Interestingly enough the jet didn't crack, only received some scratches on the gun pod. :)

So I cleaned it up, deployed LG and took off again as if nothing, lol.

Kudos to Freewing on that one!

[SanExup]

Would you say you skirt the limits with your flying sometimes Jandro? Definitely not a criticism, more of an observation and admiration. I enjoy your videos!

[JLambCWU]

She’s quick too...

[JLambCWU]

...and of course she hangs out well, and plays nice with the 3D boys.

[JLambCWU]

SPEED DEMO
Getting the peak speed out of the 80mm JAS-39 Gripen. No wind, and over 130mph!
Then we slow it down and drag that High Alpha low and slooow.
Pushed by the 5500mah 70C from RoaringTop

https://rcjetwerx.com/batteries/6-cell-batteries/

https://youtu.be/NLuZylmdkXc

[janmb]

Never seen the fascination with speed in something as inherently sluggish as an EDF. Even the most powerful EDFs in the world ultimately are not particularly fast.

If top speed is a goal, a $200 propeller model will far better cater to that.

Discussing top speed of an EDF is a bit like trying to compare the finer points of what is faster of a tortoise and a dung beetle, when you could have gotten a rabbit.

By all means, each to their own, just providing some perspective.

[Mizer67]

Never seen the fascination with speed in something as inherently sluggish as an EDF. Even the most powerful EDFs in the world ultimately are not particularly fast.

If top speed is a goal, a $200 propeller model will far better cater to that.

Discussing top speed of an EDF is a bit like trying to compare the finer points of what is faster of a tortoise and a dung beetle, when you could have gotten a rabbit.

By all means, each to their own, just providing some perspective.

I consider things like top speed, thrust and max height useful proxies for comparing overall performance model to model amongst EDFs to know if I'd be interested in owning one for other than interest in the subject (for scale jets).

I don't particularly care about top speed per se, but kinetic can be converted to stored energy and a jet that can't climb can't replicate the real thing very well and also isn't that fun to fly in my opinion.

There's a dearth of any objective performance data available in the market and the mfgs. are inclined to either be silent or exaggerate the stats. in the hope of achieving more sales.

However the test methodology has to be consistent and even then there's opportunity for testing or instrumentation errors.

I'm not particularly interested in speed just for speeds sake. I'm more interested in (more) thrust than (more) speed, but one tends to lead to the other.

[Evan D]

So I wonder when the TVs are coming

[xviper]

So I wonder when the TVs are coming

Same here. Now that the TV units are available for the Mig (RC Castle), I guess the units for the Gripen could be as much later as was the release of the plane after the Mig. I'll wait till they are available for both planes before ordering. I can't fly for now anyway.

[Evan D]

I’m just being a smart a$$ since the web still says late 2020 and we all know it’s moved to next year. Motion knows, they just refuse to say anything.

[kallend]

I consider things like top speed, thrust and max height useful proxies for comparing overall performance model to model amongst EDFs to know if I'd be interested in owning one for other than interest in the subject (for scale jets).

.

When comparing speeds measured by GPS you have to take altitude into account. I believe those numbers were taken at an altitude that would give a 15% boost over sea level values.

[SanExup]

kallend I am asking because I'm unclear and want to understand. Are you saying that because the air is less dense at altitude the plane goes faster, which I understand, or are you saying that measuring speed at altitude is different with a GPS? Which I admit I don't know enough about gps devices, do they measure speed differently at sea level?

Or am I answering my own dumb question...

[janmb]

When measuring speed by GPS you have to take altitude into account. I believe those numbers were taken at an altitude that would give a 15% boost over sea level values.

As long as you fly parallel to the ground, GPS horizontal speed should not be affected by altitude

[kallend]

As long as you fly parallel to the ground, GPS horizontal speed should not be affected by altitude

To clarify - the measurement of speed by GPS is unaffected by altitude. GPS measures how fast it is moving relative to the ground (as does radar) and is unaffected by air density.

A plane IS affected by altitude - thinner air means less drag - and will go faster at altitude than at sea level on account of reduced air density, until the propulsion system loses effectiveness. (Which is why airliners cruise way up high - they can go faster).

So a GPS max speed measurement of a plane at 5,000ft does not mean the same max speed will be achieved at sea level.

[kallend]

kallend I am asking because I'm unclear and want to understand. Are you saying that because the air is less dense at altitude the plane goes faster, which I understand, or are you saying that measuring speed at altitude is different with a GPS? Which I admit I don't know enough about gps devices, do they measure speed differently at sea level?

Or am I answering my own dumb question...

GPS reports groundspeed. It isn't affected by air density.

The air density at 5,000ft is about 15% less dense than at sea level, so the drag on an airplane will be 15% less, so given the same power it will go faster.

[Mizer67]

When comparing speeds measured by GPS you have to take altitude into account. I believe those numbers were taken at an altitude that would give a 15% boost over sea level values.

Yes, that was my thought too seeing the mountains in the background but the OP was silent on my question on the other site. Plus in the video posted afterwards there's in at least one case a decent dive entry prior to the level flight across the runway.

I don't like to dive at all with a GPS as you build up speed from the dive that isn't replicable in level flight and the typical meter like that one only records a single max speed. Even a very slight dive can add a few mph to the reading you'll get, leading to overestimation. I'm sure the GPS reading is good for a few clicks though.

You can't even do a good upwind/downwind average with a GPS meter like this without taking off the opposite direction and flying slow or landing immediately after.

[janmb]

To clarify - the measurement of speed by GPS is unaffected by altitude. GPS measures how fast it is moving relative to the ground (as does radar) and is unaffected by air density.

A plane IS affected by altitude - thinner air means less drag - and will go faster at altitude than at sea level on account of reduced air density, until the propulsion system loses effectiveness. (Which is why airliners cruise way up high - they can go faster).

So a GPS max speed measurement of a plane at 5,000ft does not mean the same max speed will be achieved at sea level.

Ah of course. Completely agreed.

While a top speed record will probably be better at higher altitudes than lower, there are factors working in both directions though. While air density adds drag, it also adds thrust. Lower density hurts both, although drag surely is a far more significant factor here.