Originally posted by rms
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Official Freewing JAS 39 Gripen 80mm EDF Jet
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Originally posted by Captain Moron View PostBloody hell there must be someone with some good comments on the Gripen out there. The Gripen surely is not that bad
Is it!!!!!!!!!!!!Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion
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Originally posted by Gary S. View PostI am going to 8s on mine, but its fun to fly stock. True its not fast and must run with over 50% power most of the time witch is unusual compared to my other edf's. It lands great looks awesome and is a worthy addition to any fleet, in my opinion. Also I have found and still testing, so no conclusion, that trimming the leading edge of the canards down a few mm seems to increase stability. (Jury still out on that one but so far so good).
Having a look at just about any air show, landing sequence or similar will easily demonstrate that the full size uses the canards in a pitch down attitude almost exclusively, and especially in any high alpha scenario (which for deltas equals pretty much all the time as long as we're talking sub-sonic)
And that is my gripe with the default configuration - poor CG makes the jet need to use canards for up pitch or even lift - neither of which should be the case. Pretty much the only case where you will see significant pitch up canards is during takeoff to help rotation.Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion
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Originally posted by janmb View Post
That is indeed the case, and showcases the main purpose of the canards in the first place: Form the airflow over the main wing.
The fixed canard with trailing edge flap on the Viggen on the other hand, are almost only for the airflow over the main wing.
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Originally posted by TangoVector View Post
According to the guys at SAAB the Gripen uses its leading edge flaps to get best airflow over the wing, the canards are for faster reaction in pitch and keeping the hydraulic system smaller. Some good links about that awhile ago.
The fixed canard with trailing edge flap on the Viggen on the other hand, are almost only for the airflow over the main wing.
The Gripen uses canards very much like the other modern deltas - which means they are pitch down 98% of the time.
All modern jets, including canard deltas, use slats to shape the main wing - that is a completely separate topic. What the canards do is change the relative alpha of the airflow actually hitting the main wing.
A fine example here, by "our" full size version from Cosford. This is a 9 minute display, including lots and lots of examples of high G positive pulls. Have a close look at the how often you see canards above neutral (or even at neutral). (spoiler: 0)
Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion
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Originally posted by TangoVector View Post
According to the guys at SAAB the Gripen uses its leading edge flaps to get best airflow over the wing, the canards are for faster reaction in pitch and keeping the hydraulic system smaller. Some good links about that awhile ago.
The fixed canard with trailing edge flap on the Viggen on the other hand, are almost only for the airflow over the main wing.
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Originally posted by Captain Moron View PostBloody hell there must be someone with some good comments on the Gripen out there. The Gripen surely is not that bad
Is it!!!!!!!!!!!!
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"Technically" you do see the Gripen and Rafale using canards 'pitch-up' as trim compensation for elevon-flaps, but that is very specific to reduce angle of attack during landings to facilitate pilot view of the runway and have more clearance to prevent tail strikes. BUT THAT'S IT! You don't see them using canards 'pitch up' in any other type of 'normal' flight conditions. Particularly not in high alpha!
BTW, don't expect SAAB to tell you about all the exact details of their flagship aircraft.
The canards are very obsiously used for so much more than 'increased pitch authority'.
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Originally posted by Airguardian View Post"Technically" you do see the Gripen and Rafale using canards 'pitch-up' as trim compensation for elevon-flaps, but that is very specific to reduce angle of attack during landings to facilitate pilot view of the runway and have more clearance to prevent tail strikes. BUT THAT'S IT! You don't see them using canards 'pitch up' in any other type of 'normal' flight conditions. Particularly not in high alpha!
BTW, don't expect SAAB to tell you about all the exact details of their flagship aircraft.
The canards are very obsiously used for so much more than 'increased pitch authority'.
As can be seen very clearly in the video I linked, the canards contribute very little to pitch up authority at all. Sure, they do probably move the CoL forward a little bit, but not a whole lot. The the control surfaces commanding the pitch maneuver are exclusively the elevons.Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion
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Originally posted by Mizer67 View Post
I think somewhere out there there's a light, high voltage setup that strikes the balance between optimum CG, thrust and weight. Evan may already be close with his (I think) light batteries. When I find it this plane should be a lot of fun. I thought my 8S Jetfan setup flew poorly given the very nose heavy CG, even with 3500 watts on tap. Fixing the CG on mine with heavy batteries adds a lot of weight which creates a vicious circle.
Honestly, my opinion is this is a plane where its performance is primarily kneecapped by it's nose heavy CG. Fixing that requires lots of weight and that has all kinds of negative effects on an already heavy for the size plane.
We need a weight reduction program for the front of the plane as rms was indicating, then perhaps things will start moving in the right direction.
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Originally posted by Evan D View PostI really think 8S shines on this plane. The JF/ HET 1738 or 1865 just work well. The 1738 has a little less power but gets a easy 4:30 on 5000mAh while the 1865 gets you that vertical at 4:00. I really like the Hobby King Plush 120HV. Cheap, small, light, works perfect and good for 8S.
I prefer 6+2 for 8S and can't find any that I really like. The PowerHobby 5000mAh 100C 8S pack is the best I can find for this and is 765g and fits great flat on the battery tray or upright moved back a tad more. There may be a 4+4 option but I have very limited use for 4S 5000 packs.
I agree the #1 thing is weight and balance on this plane. We need a way to get rid of the tail weight we are putting in it. Going to lighter 3500-4000mAh 8s is NOT an option.
I agree it needs ~5000s for the flight time too, but can't find any that are significantly less that my 4000's are in weight. Everything 8S is around 850 grams that I can piece together for 5000's. 4500's run around 800 grams best case. I think it needs to fly with maybe 750 grams of batteries at most. 700 would be better but seems out of reach. What's the Powerhobby 8S weigh? I couldn't locate a weight.
Aside from removing the pilot, there's not much else in the nose that can come out either. Perhaps one of the single wheel nose gears from another plane (F-15 perhaps?) might help slightly to make this more like an "E" model at the same time.
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I'll take a look tonight, but with some foam shaving is it possible to move the fan unit back some? I haven't really touched mine sans for 3d printing ordinance, but I feel like the weight savings in the front and CG adjustment are the way to go. I remember one person cutting foam to move their battery back, that seems like a good place to start. I'm sure there's more we can do!
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The PowerHobby 5000mAh 100C 8S pack is 765g. They also have a 5000 50C 8S but it's bigger and heavier. You'll need a 8S charger for these.
Originally posted by Mizer67 View Post
I could barely eek out 3:00 with ~15% left in the pack with 8S 4000's.
I agree it needs ~5000s for the flight time too, but can't find any that are significantly less that my 4000's are in weight. Everything 8S is around 850 grams that I can piece together for 5000's. 4500's run around 800 grams best case. I think it needs to fly with maybe 750 grams of batteries at most. 700 would be better but seems out of reach. What's the Powerhobby 8S weigh? I couldn't locate a weight.
Aside from removing the pilot, there's not much else in the nose that can come out either. Perhaps one of the single wheel nose gears from another plane (F-15 perhaps?) might help slightly to make this more like an "E" model at the same time.
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Originally posted by HockeyMac! View PostI'll take a look tonight, but with some foam shaving is it possible to move the unit back some? I haven't really touched mine sans for 3d printing ordinance, but I feel like the weight savings in the front and CG adjustment are the way to go. I remember one person cutting foam to move their battery back, that seems like a good place to start. I'm sure there's more we can do!
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