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F22 Fail

skeplin

Senior Member
#1
So I decided to build an F22 after seeing how well they fly and how easy they are to assemble. I get everything installed -- motor, speed control, servos -- I get everything trimmed out and configured, elevon mixed, centered servos -- I program the speed control and balance the center of gravity with the battery so that it's just forward of the motor.

Excited, I drive to a local park and check everything. I power the motor up, let it go and it promptly climbs to about 8 feet and then nose dives into the ground. Awesome. :(

SO, I assume that either I have the motor pitched up somehow or the nose is too heavy. I thought the CG balancing compensates for that.

In short: any advice while I rebuild?


I've left off a lot of detail so here it is: Turnigy Park300 1600kv motor, 3S 500mah battery, 30a speed control.
 

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#2
What sized prop?

Did the motor cut out?

Are you sure the control surfaces were going the correct direction?

Did it "dive" or just nose over?
 
#3
Could actuley be tail heavy depending on how it behaved in the air. Did it pitch up first, then stall and nose dive? Usually a model can handle nose heavy and is always best for a maiden flite.
 

skeplin

Senior Member
#4
8x4 prop. I don't think the motor quit, it made noise up until it hit. It basically arced from my hand to the ground about 10 feet away. I'll post video though it's embarrassing.
 
#10
Primarily, what I see in the video is this:
-needs a more vigorous launch;
-needs more throttle on launch.

Planes can be heavy and still fly--they just need more thrust/speed to do it.

Are the control surfaces trimmed to neutral?
Was any control input (other than throttle) given on launch?
Is it foam board?

As FlyingMonkey says, "No need to be embarrassed". As long as you're having fun.

Cheers!
Randall
 

skeplin

Senior Member
#11
Thanks for all the advice everyone, I really appreciate it -- the good news is that I'm not entirely discouraged.

The control services were trimmed to neutral and it is foam board. There is quite a bit of duct tape on it however. I did not pull back on the stick at launch (excitement got the best of me.)
 
#12
That just didn't have any power and had no up in the elevator. Tail heavy at low power tends to settle butt first. If you balanced it correctly then you don't have to worry about it being tail heavy.

Was the prop on the correct way. Sounded noisy but not powerful. The raised letters on the prop need to face forward, on a pusher you turn the prop around from the normal way, raised letters toward the engine WHICH is towards the front
 

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#13
I'm thinking the same exact thing as MrClean. Lots of noise in that prop, should have seen more thrust from it. Quite possible it was put on "backwards".

We've all done it, and if anyone claims they haven't, then they either have flown nothing but RTFs, or they're lying. :D
 
#14
You video would also seem to me to suggest inadequate thrust.
So
How much does your F22 weigh complete?
With an 7x3.5 prop the Turnigy 300 should give 420g (14oz) thrust at full power drawing just over 7A.
Something like an F22 needs a thrust almost equal to its weight.
An 8x4 prop is recommended for this motor with a 2s battery.
On a 3s it will be drawing significantly more current, likely more than a 500mAh battery can provide.
 

zev

lumpy member
#15
before you fly next time, I recommend finding a feild with tall grass and doing a glide test. just chuck it, hard. that (i think) is the best way to balance a plane.

how high was the throttle at launch? plane like that should probably take of at 3/4 ish. if the prop is on right, and the motor is spinning the right way, it should just sort of fly out of your hand.
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#16
My F22 doesn't require a hard launch at all - very similar to what the video shows, with only about 1/2 throttle. It almost looks like the controls were reversed and instead of a climb you got a nose-dive. Or maybe just nowhere near enough UP trim.
 

skeplin

Senior Member
#18
I bought two types of props, CW and CCW though I'm not sure how to tell the difference between the two. I was getting quite a bit of pull from the plane. The motor should turn counter-clockwise right? Which type of prop do you need? Do you just take a normal prop and turn it around?

I had the throttle at a little over half.
 

FlyingMonkey

Stuck in Sunny FL
Staff member
Admin
#19
In this case, it doesn't matter which prop you use, as long as it's facing the right way, and the motor is spinning the correct direction for the propeller.

As mentioned before, there are raised numbers on one side of the propeller, this is the "top" or "front". If you lay the propeller on a flat surface, with these numbers up, the higher edge of the blade is the leading edge.