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FT Simple soarer, Can I get a little help from my friends?

#1
Frame: FT Simple soarer (speed build) 3ch.
Prop: 9x4.7sf
Power plant: Emax 2280kv (plans call for 1300kv)
Power source: Kinexsis 800mAh 2S
Servos: 8.5g

I can not get this thing in the air. I have been fighting this thing for weeks now.
The last time it crashed I thought I was going to jump on it and stomp the ever-lovin servos out of it!


---EXAMPLES---
No wind, Gliding, No input given. I tossed it and got a gentle, nice, (dare I say) perfect glide. So by this we know CG is not an issue.
-no video-

#1
Strong wing 5-10 knts, Gliding, No input given, 10' off my hand it noses up, stalls, gets blown backwards and belly lands, no damage.
https://youtu.be/2qe5PSV4zcU

#2
Strong wing 5-10 knts 1/2 throttle Thrust Angle 4-1/2 degrees down. 15' off my hand it noses up, stalls, noses down, face plants, crushes fuselage and increases TA to about 10 degrees.
https://youtu.be/r7l07lhdXuU

#3
Strong wing 5-10 knts full throttle, Thrust Angle about 10 degrees down. 20' off my hand it noses up higher, stalls, noses down, face plants.
https://youtu.be/BUyLl66udeo
>THROWS HANDS UP IN THE AIR<:confused:

So I started with 1/2 power in #2 video the Thrust Angle is at 4-1/2 degrees down.
(I know I cut it with a miter saw)

After the face plant in video #2 the Thrust Angle is closer to 10 degrees down.



I had been using a 5045 prop with exact same results.

The 9x4.7 is new, I was hoping that would get me in the air.

In my head I thought if the 9x4.7sf prop did not help I would try increasing the TA but before I could get it to the bench What ever is wrong, Newtons 3rd law and Gravity did the work for me after video #2 and the 1/2 throttle face plant.
:(saved me some work there:)


So friends, what now/next?

?Smaller motor? is all I can think of, but I'm not throwing all 2280kv at it.

I'm pretty frustrated,
I could use some help from my friends.
(So we never met and I have like 3 posts, dont worry I'm volunteering @ FF-E I'll meet you there.)
 
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SlingShot

Maneuvering With Purpose
#2
"....noses up, stalls".

The plane was launched directly into a stall. You must not let it nose up close to the ground. Launch it level. And don't let it balloon up. You might need to add some down trim as well.

Your plane is badly under powered as well. Although an experienced pilot could fly it with that motor, the design calls for a much larger motor. Stick with the 5 and 6 in props for the motor that you have. A 6x3 would be good.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#3
I agree with the small prop on a high Kv motor.

As for the launch, try the "No Power" launch into a glide and then slowly apply some power, (GENTLY). to see if you can firstly extend the glide and after a couple of glides try to see if you can get it to fly flat and level or possibly slowly climb.

You mention down thrust angle with such accuracy I hope you have checked wing and tail incidences with equal attention to detail.

Have fun!
 

JimCR120

Got Lobstah?
Site Moderator
#4
First off, human, thank you for such a well chronicled gripe. In a forum where sometimes we get merely cries like, "Help, it won't fly!" your detailed explanation with videos is so very helpful.

You say the first flight was ideal. Since then power and control somehow made things worse. I dare say most if not all of us have witnessed the same when learning to fly. I think you've focused on two important factors (CG & thrust angle). I agree with both posts above that focus on a third thing (control).

Often new pilots shoot for altitude first instead of airspeed not realizing that it is the airspeed that will make the wings life, giving you altitude.

My recommendation is the same as above. Focus on maintaining level flight and gaining airspeed before seeking altitude. When you are able to lengthen the glide you will eventually see how speed and altitude correlate in real life. Also, be gentle on the sticks. Control surface movement can be overdone making them do more slowing than directing.

By the way, flying over long grass can make for gentle crashes when they happen.

Don't give up. You will get past this as we all have.
&#8212;Jim
 
#5
Thank you all for your input, I really appreciate your willingness to give your thoughts. I have a question or two about your thoughts....

Slingshot, I am not quite sure what you mean when you say it is under powered. the FT spec for a motor is 1300kv, I have a 2280 on there now.

Hai-lee, regarding tail incidences, it is a FT speed build, the build went smoothly nothing has been cut or trimmed everything is sitting flush and square so it is a proper build. I would think the tail incidences are correct because when I throw it with no head wind, fully loaded(w/battery),without input I get a nice glide.

Jim, for as detailed as I have been I did fail to mention on the times (many off camera) I have attempted to give the control surfaces input they are unresponsive. It is like the only control I have is throttle. I do understand that the key to altitude is slow and steady. I have been playing with a micro Cessna 182 (WL toys) I have many hours of stick time on that >30 but <10. Oh detailes only makes sense to me, you guys are not psychic, if I would like good suggestions I better give good information,
I tend to over engineer $hi! too ;-[) <--see what I did there

The motor is the only thing that is not to spec. I would assume just throttling back as Jim suggests would allow it to fly but having tried it and the the zero power, zero input of flight#1 leads me to believe that there is something else at work. Its like the wing is generating too much lift. I watched the build video as I built it, do you guys think I could have made a fold at a wrong place thus making it generate to much lift?

So I have a 1300kv and a few 6x30 props on the way. What the hell it was only 12.99. After I put that on at least then I can say everything is in spec.
Saturday I will have new news weather permitting.....



scrap it and try another frame? ...........mmmmmm...........Optera
 
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Hai-Lee

Old and Bold RC PILOT
Mentor
#6
Thank you all for your input, I really appreciate your willingness to give your thoughts. I have a question or two about your thoughts....

Hai-lee, regarding tail incidences, it is a FT speed build, the build went smoothly nothing has been cut or trimmed everything is sitting flush and square so it is a proper build. I would think the tail incidences are correct because when I throw it with no head wind, fully loaded(w/battery),without input I get a nice glide.

The motor is the only thing that is not to spec. I would assume just throttling back as Jim suggests would allow it to fly but having tried it and the the zero power, zero input of flight#1 leads me to believe that there is something else at work. Its like the wing is generating too much lift. I watched the build video as I built it, do you guys think I could have made a fold at a wrong place thus making it generate to much lift?

So I have a 1300kv and a few 6x30 props on the way. What the hell it was only 12.99. After I put that on at least then I can say everything is in spec.
Saturday I will have new news weather permitting.....



scrap it and try another frame? ...........mmmmmm...........Optera
I understand that it was a kit and that everything fitted together perfectly but when I mentioned incidences it is quite possible that a warp in the wing or tail, which cane change the incidences across the span of the surface could be an issue.

Additionally if the folds in the wing were not glued to give the exact profile as in the "How TO' Additional lift could result at the expense of an altered CG location, (Wing profile not correct).

Finally the motor seems to be quite large, If the motor is too large then the airflow it generates across the wing could be giving a significant boost to the lift. If it is the case then trying shimming the motor mount such that the down thrust is decreased slightly. Try flight again and if a little better decrease thrust angle slightly again, if worse then increase down thrust beyond initial settings..

Whilst this might seem to be counter to logic it could be that the motor thrust being excessive might be the problem.

Just a few thoughts!

Have fun!
 

quorneng

Active member
#7
If this is the motor you are using then you are using the wrong prop and seriously overloading what is quite a small motor.
A 6x4 is recommended but with a 2s battery your Simple Soarer will be rather under powered. Using a 800 mAh 3s battery with a 6x4 would give you a reasonable performance.

The recommended 25g 1300 kV motor, say an Emax 2822, will drive the recommended 9x4.7 on a 2s battery.

.
 

SlingShot

Maneuvering With Purpose
#8
Slingshot, I am not quite sure what you mean when you say it is under powered. the FT spec for a motor is 1300kv, I have a 2280 on there now.
Those numbers can be confusing. Easier to go with weight at this point. The motor recommended by Flite Test is a 39 gram motor. Your motor is a 18 gram motor I believe.
 
#9
The KV number of a motor is the number of revolutions per minute per volt. For simplicity sake a 1000kv motor fed 10 volts will run at 10000 rpms under no load. It really has little to do with motor power which is in watts. Generally a higher KV motor is made for smaller props. So a micro quad will have a 4000kv motor while my simple storch runs an 1100KV motor. Basically the bigger the actual size of the motor the more torque is has.
Trying to force a low power high rpm motor to spin a larger prop can damage the motor and blow your ESC. As well, the motor just may not have enough torque to actually spin a larger prop to the proper speed.
A 2206 motor is 22mm in diameter with a 6mm high stator,. Usually these run around 2200kv and can spin a 5" prop fairly well.
A 2215 is the same diameter but the stator height (wingdings) is 15mm thus giving it a huge amount of torque compared to the 2206. These generally run around 1100KV and can run a 9 or 10" prop with no issues.
This is pretty basic as the actual size of the wingdings as well as type and number of magnets affect motor power but it is a good starting reference.
Also remember that a larger prop's blade tips will be moving in feet per second at quite a bit higher speed than a 5" prop at the same rpm. Thus the lower rpm for a larger prop.
 
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