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Old Sep 09, 2014, 09:42 PM
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Jet Legend JAS-39 Gripen EDF

I have been holding out for a delta wing as I just like the way they handle and how much more forgiving they are.

So, I just picked this one up;

http://www.rcgroups.com/forums/showthread.php?t=2241135

I was surprised to see that it has intake ducting already installed!

I have 2 power systems and need to decide what way to go. I have a Stumax SM110-52 and a DynEmax. The intake ducting looks a bit too small for the DynEmax but just about right for the Stumax. I am thinking about 4k watts out of the Stumax and according to this thread, a similar plane flies (not really well albeit) on approx 3100 watts.

http://www.rcgroups.com/forums/showthread.php?t=783925

I see that the specs from Jetlegend suggests 12-26lbs thrust and that the Stumax can produce just over 13lbs. Looks like the DynEmax can get between 15-25lbs. But, with the Dynemax I will probably have to have a cheater hole or maybe leave the nose gear door off and just not connect it to the intake ducting.

So what would you do? Add a little weight, tackle the ducting/cheater hole issue and go for the DynEmax or keep it light and go for the Stumax?
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Old Sep 10, 2014, 03:10 PM
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Reinard did one with and xps fan, he eventually changed it for a kingtech k80 turbine. im not sure edf is going to do it for you.

here are some videos below

Skymaster JAS 39 Gripen/ XPS-Dynamax Graspiste.wmv (3 min 26 sec)


Skymaster JAS 39 Gripen Erstflug mit XPS Dynamax 30032010.wmv (4 min 5 sec)


Jet together Niederöblarn 2011 (5 min 40 sec)
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Old Sep 10, 2014, 03:47 PM
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Ah, thanks for the videos! Any idea of he documented the EDF install anywhere? I wonder how similar the JetLegend and Skymaster are?

Thanks!
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Old Sep 10, 2014, 05:03 PM
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They are the same plane, just the internals will probably differ slightly.

here is his thread

http://www.rcgroups.com/forums/showthread.php?t=1219859
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Old Sep 10, 2014, 05:12 PM
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Cool, thanks for the info!
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Old Sep 17, 2014, 09:30 PM
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Gear is installed and I am waiting on some additional air system pieces. I got the fan test mounted with the inlet lip on today. Man it is nice working on a plane this size! So much easier...
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Old Oct 04, 2014, 10:20 AM
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Ready for maiden. Maybe this week. A couple pictures.
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Old Oct 05, 2014, 08:02 PM
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A little too windy for a maiden today. Did get in some taxi tests however,

Jet Legend JAS-39 Gripen EDF Taxi Test (3 min 42 sec)
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Old Oct 17, 2014, 12:43 PM
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Waiting for video on this nice bird.
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Old Oct 18, 2014, 07:52 PM
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Dang, thought I already posted it!

Jet Legend JAS-39 Gripen EDF Maiden (2 min 39 sec)
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Old Oct 18, 2014, 08:41 PM
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Nicely done! What is your final weight?
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Old Oct 18, 2014, 08:48 PM
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Right at 24 lbs. I have since changed to 14s 5300 Gens Ace 30c (instead of 5000 Nanotechs) and added a couple cheater holes in the top hatch. There is no weight increase with the battery upgrade. If all goes well the 2nd flight will be tomorrow. I am planning on getting the gear up on the first downwind and see how she does all cleaned up with the cheaters. Hopefully I will find that she is flyable without blowing up my lipos
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Old Oct 24, 2014, 02:07 PM
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Nice job getting it up and down in one piece. You're breathing like an F-18 pilot pulling 9G's!! Looks nose heavy to me - were you pulling a lot of elevator going around?

I have read that these are tricky to fly - the wing area is actually not that much for the weights the plane builds out to. Reading up on the turbine version build logs on RCU, getting good controllable approaches / landings is all about setting up the canard correctly so you get just a little up, and not too much or things get wild. There is one guy in particular - an eastern block fellow with and orange and red one - who seems to have figured out the correct settings and has a video. It is used the same way you would use flaps.

I've also read about issues with the canard linkage either being weak or having issues - I think there may be upgrade parts, or maybe that was already done on the airplane...
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Old Oct 24, 2014, 02:21 PM
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Thanks. Yeah I did back to back maidens... The first was a Tamjets F16... In hindsight, I didn't need that Redbull before hand!

Yep, I followed that guys setup info but have tweaked it a bit since the maiden. I added a little down elevator mixed with the canards when set for landing (as he suggested but I didn't do). I didn't feel like it was nose heavy but be aware that I didn't retract the gear for that flight so the CG was a bit more forward for landing/takeoff.

If all goes according to plan, I will get a flight in tomorrow with new batteries, cheater hols and gear up this time!
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Old Oct 24, 2014, 05:38 PM
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Great job techspy! That is not the best airframe for EDF but you made it happen. Eventually you should be able to get some flaperon mixed in...as the real ones do. Those control canards are probably tricky to get just right...but should make for a good flying delta once you get it all set. Looks to fly great already! The Grippen has grown on me over the years...
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