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Help! Mini Arrow needs a lot of down to fly level

#1
Hey guys first time posting! So glad to be a part of this community!

I just built a mini Arrow and it is my first wing I have ever built and flown and it is incredible! I was hoping you guys could give me some suggestions though for my plane. When I fly it under throttle the plane acts as if I'm holding full up elevator or elevon rather. It just goes straight up and I have to push quite a bit of down elevator like almost FULL down in order to hold level flight.
I should also add that the plane does not do this when throttle is below 75%.

The odd part is that the cg is where it is specified to be by the plans 1.75" from firewall and the elevons are set at the recommended level said by Josh Bixler in the build video. Also thrust angle looks for the most part perfect.

So what gives? Btw I should say I'm running power pack A.
 
#2
That's funny, mine needed more up trim than specified by Josh! Most planes will pitch up at high throttle if they are trimmed to fly level at low throttle. If you post a video of it, we might have some more ideas. It is a really great flyer when it is trimmed up properly!
 
#3
Provided that the "C of G" is marked and in the right spot and there's no warping of the surfaces the only other thing that would make it pitch up under power is the thrust angle of the motor. Seems like you have the motor angled up a little to much (looking from the back).
With flying wings the vertical thrust angle should be in line with "C of G".
A quick fix is to shim it with something under the top two motor mount screws reducing the thrust angle so the thrust angle is line with the "C of G".
 
#4
the only other thing that would make it pitch up under power is the thrust angle of the motor.

I agree with Andrew looks like you need to change your thrust angle. Nearly full elevator is too much. You’ll never get it perfect, at least I never gotten it perfect with my Veras wing. When you get it closer, you can mix the throttle to the elevator. I trim my wing to fly level at full throttle, then change the throttle to elevator mix to give it a good glide slope when power is off.
 
#7
I've never used a power pack. My arrows tend to get a 2206 high kv motor. I learned early on I don't like swappable pods. I just make sure there is access to service the components and glue everything in permanently. Less slop that way and stronger.
 
#9
Do it! More power! One thing you'll have to be careful of is CG. That's a lot more weight hanging off the back! Put all the electronics you can in the bays, and you'll probably need a little weight up front. She should fly, probably.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#11
To ensure that your setup is correct on a flying wing you should, (at height), cut the throttle and try to keep the wing in level flight by feeding in up elevator control until it reaches maximum. When at maximum "UP" the wing should slowly decrease its altitude without stall or anything similar. If the CG is too far forward the nose of the wing will bounce up and down as it glides down and if the wing wanders from side to side or drops a wing then it is setup with the CG too far aft.

With the CG set properly THEN and only THEN you can test the thrust angle of the motor but flying in level flight and opening the throttle to full. If the wing climbs the thrust angle is too high, (for a pusher that is), and if it noses down the thrust angle is too low, (again for a pusher).

With a properly setup motor thrust line, the throttle should have ZERO effect upon the pitch of the wing in flight.

The speed the wing travels at has no effect upon pitch!

Have fun!