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Su-47 build/question thread.

Foam Addict

Squirrel member
#21
I Wasn't clear again, sorry about that I'll edit my post to clarify for later.

While the fuse is only 6" wide, I have 8-9" of usable space. A 6x3 prop is my prop of choice using a 3 cell.
Auw should be around 13-14 oz using a 1300mah 3 cell. For duration or speed (depending on how heavy my left thumb is), a 2200mah 4 cell and a 5.5x4.5 allows for about a 15min flight at an auw of around 16 oz
 

xuzme720

Dedicated foam bender
Mentor
#22
That should be a nice workable setup. Make sure you have front to rear bracing around the slot to keep it from folding there. Most of the designs have either a keel that runs outside the slot or some other type of rigid bracing like CF or skewers, etc.
 

Foam Addict

Squirrel member
#23
Woohoo!
After a lot of fiddling with the CG, I finally got 6 stable glides with the Berkut!
Never mind that the last one had a servo glitch. And it lost its head... A day late for a Halloween costume.
image.jpg
 

Foam Addict

Squirrel member
#26
Well... It flies... But I have zero canard authority. It needs around 60 degrees of deflection to have any response. After 3 flights, 2 on film, I was unable to clear a barbed wire fence, and tore the plane into 6 Pieces. I will start a new one in around a week, after a hobbyking order comes in.
 

xuzme720

Dedicated foam bender
Mentor
#27
The canards might need to be a little larger, or the Cg needs to be adjusted a bit further back. Were you having to hold in 60 degrees of up to fly or would it take that much just to see any response? If it was taking that much to see any response, was the same deflection needed on both up and down?
 

Foam Addict

Squirrel member
#28
I adjusted the CG to the point where the plane lost control, and I still needed around 25 degrees of canard to maintain altitude, and then 40-60 degrees to notice an effect. I never used down, I had no idea whether I could bring it back up!:p
Edit: here is a flight photo.
image.jpg
 
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xuzme720

Dedicated foam bender
Mentor
#29
I'd say the canards might need to be a little larger then, or mix some elevator in with the canards. There is a lot of flat area to overcome...
 

Foam Addict

Squirrel member
#30
Yes! My Grandfather wants to buy the parts to build a 125% version. I also discussed the aerodynamics of the plane with a friend, and we decided to go with a canard, aileron, taileron setup. We also found the problem with the canards. I swept my wings too far forwards, and the canards were behind the leading edge. They are supposed to be out in front...:black_eyed:
I have a new design using a turnigy 2826-6, a 6x5 or 7x3 prop, and a standard sized canard servo. I also redesigned the torque rod for the canards to eliminate slop. This will fly well yet!
 

Foam Addict

Squirrel member
#31
image.jpg
As promised: SU-47 mk II
Decreased wing sweep, elevators, ailerons and canards.
44" span, 50" length. Either Turnigy 2826-6 or NTM 3536 1400kv motors, 7x3 prop.
 

Foam Addict

Squirrel member
#37
Umm, okay, I need some advice, two rudders and possibly a gyro. First off, mk II flies great... After I doubled the size of the fins, and added an elevator mixed to the canards.

image.jpg

However, if it gets too slow in a turn it goes into a beautiful knife edge. "What's the problem with that Josh?" Well, it won't come out. I nosed it straight in with severe damage to the nose because I had zero aileron authority in the KE, and pitch gave me two options, down or down to the left. Any ideas?
P.S. Finished photo!
 
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xuzme720

Dedicated foam bender
Mentor
#38
Sounds possibly like a tip stall. Something you'll have to deal with on swept winds, even those with reverse sweep. One or two things to try. One is try some wash-in at the tip. Sometimes used on conventional wings as wash-out to keep the tip from stalling. The second one is to fly faster and don't get so slow.
I don't always trust Wiki, but in this case, it seems to be good info. http://en.wikipedia.org/wiki/Washout_(aviation)
 

xuzme720

Dedicated foam bender
Mentor
#40
umm... How hard is the launch throw? I know these planes really don't like it be too slow. Until you get enough air over the control surfaces they tend to want to tumble...