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Jun 23, 2020, 09:58 PM
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OMPHobby S720 in the rain ...

OMPHobby S720 in the rain (6 min 27 sec)

In the rain !

What a PITA . Wind on the way , so of course I had to fly this morning ( No wind ) .. And naturally it had to rain .

OMPHobby S720 with a Eachine 119 S-FHSS Rx . Yes, I get to fly it on the Taranis ( F something rain )

What should have been fun , was and wasn't .

A) Taranis = Rock solid ! Just Chalk and Cheese .. Fact Trashmitter is chalk ! If anything elevator needs expo .
B) S720 = Has a tendency to drop it's nose if you use the elevator ( stabilised mode )and then after 1 or two meters flies level . This is a bad tendency during a landing .
C) I broke the S720 = Yes , on my first landing ( due to the rain ) I made the mistake of letting the model have neutral elevator .. This resulted in the S720 dropping the nose and the wheels caught the grass and tore the landing gear back . Yes the bottom of the fuse where the gear goes in , was torn ( Foam ) . Thankfully a easy repair . ( I keep flying and landing )
D) Ailerons = are a little soft .. A little more would be nice .
E) King Kong 5045 prop = For this flight I had hacked on a King Kong 5045 prop to see if it would work as a replacement for the factory prop which apparently is a little hard to find ( buy ) . Current draw is close to factory prop , but the thrust did seem a bit down . Plan was to stunt the S720 a bit to test out the prop , but that rain ! ( I did a little )

On the factory Trashmitter , not impressed !
Bound and flying on the Taranis Q , a completely different animal .
It is a little quirky ( nose drop in Stabilised mode ) , but nothing you cant learn to live with .
Certainly much higher performance than the T720 . A little sensitive on the elevator , nothing some expo wont cure .

On the Taranis , I would call it 8.5 out of 10 . Maybe it was the rain ? But for now I am calling it at 8.5
I think OMPHobby has to just do the S720 Bind and Fly , forget the Trashmitter , and just plug in a Rx for DSM / S-FHSS / FrSky / FlySky .... Just forget about bundling the S720 with that Trashmitter .

The Trashmitter works with the T720 , only because the T720 is such a stable platform .

I do think that I am going to enjoy the S720 ( For Sure ) and next time I fly I may need to try the 6030 Gemfan
Last edited by old4570; Jun 25, 2020 at 08:35 PM.
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Jun 23, 2020, 11:55 PM
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The flight stabilisation is quite quirky on the elevator. Normally putting the link on a different hole should fix that, and then you can regain the lost travel easily by afjusting on the transmitter. However, with the direct connection of the servo to the control surface, this is no option. Adding expo on the transmitter will help soften the controlled elevator response, but not the gyro's correcting responses, as these are still having 1:1 ratio.

Best thing might be to turn the servo for the elevator in a mere pivot point, adding an extra lever that is 90 degree to the one that the elevator surfaces slide over, and put the servo inside the fuselage, with a control rod to the extra lever. Then you can mechanically adjust the response of the elevator to the gyro corrections, and reducing it's twitchy response, while with travel adjust on transmitter, make sure there is still plenty of throw on the stick response.

I assume you are already using a heavier battery, to reduce the tail heavy nature of the plane with stock battery? Apart from that, a bigger battery also handles the current draw better. My stock battery was puffed after a few flights, even though I never drained it below storage voltage. So it just can't handle the peak current load well, it seems.
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Jun 24, 2020, 12:33 AM
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Got to watch the current ..
I talked about current draw somewhere ..
So I am trying to stick under or match what the factory prop does .

Should be under 6A Current draw ..
Factory prop pulls 4.6A Full throttle + some ( I saw up to 5A )

5A 2s , = 40Watts ( around ) .. Hmmm ...

Anyways , I use the zippy 350 2s , seems like a good cheap battery .
When I came home I still had 53% battery left ..
So around 5 minutes should be super safe .

Next I will try the 6030 gemfan , pulls much less current .

Yeah , the gyro .
Lots of porpoising ..

I would pull up and then give neutral stick and the gyro would push the nose down ..
I would then pull up and go neutral and the gyro would push the nose down .

Comical I guess . Trick would be to be more gentle on the elevator ( Expo ) and lean on it gently till you get to the altitude you want .

Thats how it was with the landings , I had to lean on the stick to keep the nose up otherwise the gyro would drop the nose . It's not like the T720 which lands itself with no user input . Just cut power and the model does a perfect landing . ( That is not the S720 )

Be interesting now that it's on the Taranis , be nice if you could dial down the gyro sensitivity .
Hmmm , can you dial down the gyro sensitivity ?
I mean rather than a 2 position switch , one of the rotary switches ? ( ?????/ ) Or mix in a rotary ?
Like with a heli gyro !!!!
Jun 24, 2020, 02:08 AM
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I have been using my Jumper from the start never even put batteries in the factory transmitter. FRsky xm+ receiver works nicely. I also have not used the stock battery. Seems too small and plane is tail heavy. 900mah from my XK x520 fits perfect. A Tattu 800mah also just fits in (a bit fatter than the 900mah, but shorter). Both perform well. I do have 30% expo dialled in. If anything it still wants to climb and at least for me, throttle off and glide home is a breeze. Just about stalls before touch down and is a dream to land (so far). Busted a stock prop on first flight by being too enthusiastic. Pain about the 5045 props, especially since I spent quite a while getting two made up to fit nicely. They will do as emergency spares. Replacement stock props arrived fairly quick from Aliexpress actually. Guess I just did not know where to look for the spares!
Jun 24, 2020, 02:38 AM
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I should have a few props on the way to try ..
Would be tempted to try a 6x3x3 , but thats a two bladed spinner .
Hmmm , guess I could try 3D printing a 3 blade spinner ?

Fitted a Gemfan 6030 to the S720 .. See how that goes .
Will add expo to the elevator next time I fly .

Dont forget , you can calibrate the Gyro for level flight .
If it climbs under power , yeah , it might glide real nice .. A little like gently leaning on the elevator to keep the nose up .
Jun 24, 2020, 03:03 PM
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Pretty much perfect flying weather today and I had a pretty much perfect flight! What was not perfect? Not charging up extra packs so I could fly more!!

The climb is nothing to worry about. It is not severe and I prefer that it climbs a bit than dives ! The extra nose weight of the bigger battery really helps it IMO. I don’t see any of the porpoising that others have mentioned, even when hand launching at high throttle (which I have to do because the council is not cutting the grass due to coronavirus). I am very happy with this plane. However, I also just bought an Eachine P51 mini mustang for a bit of fun too! I also need to give my XK X520 an outing at some point, but the S720 is so easy to transport due to the removable appendages!
Jun 24, 2020, 05:55 PM
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The porpoising might be the gyro & rearward CG ..

I can say for sure the gyro pushes the nose down with 100% certainty . ( In full stability )
Is it the CG ? or a overly sensitive gyro ? That I cant say . ( Both ? )

More weight in the nose certainly would tame what is in essence a very responsive little plane . I wonder about the gyro ? can you adjust gain VIA the radio ?
Jun 27, 2020, 12:11 PM
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I also have some expo built in that may help control, but won’t affect the gyro input. I probably should give the stock battery a go. It just looks so small and when I checked CG it was way off what I would like (which is about 1/3 back from leading edge of wing, which I know is simplistic and there are “proper” ways to work that out). The 900mah battery results in GC just about where I would expect. I know others have said using stock battery with extra weight in the nose helped reduce porpoising a lot. I guess if the flight controller was like a racing quad FC that you could hook up to a pc and change settings, then altering gyro settings would probably be possible. I can’t think of any way to do that as it stands.
Jun 27, 2020, 08:34 PM
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I threw in 40% expo which looks to have taken care of it ..

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