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Help! Pusher Kraken Mod, lost some "elevator" authority.

kilroy07

Well-known member
#1
Okay, so I nosed in my Kraken.
I don't consider it a "crash" as I was flying FPV and all I saw was trees. (post flight, I realised I stalled her.)
Now, I don't know about you, but I've had my fill of fishing planes out of trees...
(I STILL have the wings to a FireBird Stratos in the trees of a local park and that's been over 6 months now...)
So... as this build is my "test bed" I decided to transition her to a pusher.

Here's the build...
IMG_8005[1].JPG
A "ramp" to use FT's power pod design.
IMG_8006[1].JPG
Located 8" off the wing's outer panel seam line.
IMG_8007[1].JPG
Then the powerpods are placed inverted on top.

I had to use 2 EXTRA 2200 batteries to get the CG to balance as before... mind you, that's a total of 4 batteries packed right up on the nose to get her to balance where the original Kraken balances.

I am not happy, because as it is, I lost quite a bit of "up" authority (Elevator)... I could NOT get her to loop any more....

So my question is...
Should I look at the thrust line (currently set at 5% down) OR
Should I decrease the nose weight.... Drop a battery or two?

After I get her looping again (as she did as a tractor) I'll publish the plans for the mod (unless someone wants to experiment... Just PM me.)
 

Merv

Well-known member
#2
Sounds like you have added about 12 oz of battery. That’s quite a bit of weight. She may just not be able to loop anymore. You could try moving the CG aft, I’d recommend no more than 1/4 inch at a time. If the Kraken is anything like the Veras it will get squirrelly when you’ve gone too far.
 

PsyBorg

Wake up! Time to fly!
#3
Also you moved the motors behind control surfaces so far less air flow to push against. May need larger control surface to compensate.
 

quorneng

Well-known member
#4
As Colin chapman of Lotus famously said "To improve performance - add lightness".
Doubling the weight of batteries is unlikely to improve anything.
The power to fly is directly proportional to the weight so with same power but more weight means you will have less 'spare' available for anything else like climbing out of trouble!
If you are having trouble achieving the required CofG don't add weight but move the existing weight (batteries) further forward even if that means extending the nose.
 

FroggerJon

I landed it!
#5
Some observations from seeing her fly yesterday...

1. She looked nice and stable in cruise, so my guess would be that you’re SLIGHTLY nose heavy and the extra weight is the reason for the lack of maneuverability compared to the og build.

2. I’ve noticed that even when I don’t have to add weight, I have to move my cg back or significantly adjust thrust angle when converting from tractor to pusher. Something about moving the motors from below the wing in the front to above the wing in the back make the balance point shift to achieve the same handling.

Just my $0.02. And also, well done! It was a blast chasing such a big wing!
 

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