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FT Delta with "The Beef" swappable pod and 2200 MAh lipo...a no-go

#1
Well, I tried my best in flying my Delta with "The Beef" motor package from lazertoyz - the one meant for the Baby Blender (i.e. the GT2215/09 - 70g motor and a 30A ESC). Well, I think with that pod, compounded by a heavier 2200MAh battery...is really a no-go.

I continuously launched it..and it would go up and straight...and then unvariably make a steep left turn..and then right into the ground. After looking at video and flying with more experienced folks...problem I really think is that the Delta in itself has little to no glide slope as is (with the Blue Wonder motor combo), that when it becomes so heavy, that motor doesn't do the trick anymore...it becomes a flying brick only experts might be able to handle!

Let me know if anyone else has had any experience experimenting with stronger motors on the FT Delta!
 

engineer

Senior Member
#2
I have been having similar issues with the FT Flyer (larger motor, 2200mah bat). I'm wondering if the torque from the motor and the short and lightweight wings don't play well together. Also, it might be a big difference in wing loading?
 
#3
Yes, the torque on that motor definitely impacts my ability to fly it at all - as it immediately rolls to the left before I can manage to do anything about it. Even with the Blue Wonder, I'd notice how much 'easier' it was to fly left turns, rather than coax the plane to make a right turn.

Also, with the Blue Wonder on, you had to keep it under power, otherwise it would go into a steep decline... which obviously worsened putting the "Beef" powerpod onto it!
 

ivan747

Junior Member
#4
I was reading about wings on Wikipedia and came across one interesting piece of information: flat, symetrical wings (like the ones used in the Flyer and almost used in the Delta) are ver inneficient and in reality are only used for supersonic flight. When you go from 24g to 70g+ in the motor, you don't get 3 times the power. Add to that the extra weight of the battery. Now you have a heavier plane so you need either a more efficient wing or more speed. But the motor you put in doesn't quite cut it in terms of power. The motor and battery combo needs more power for its weight.

Add to that the toque effect you are described and we got problems. Add to that the fact this doesn't have a rudder to trim off.

Maybe you can correct for the spin by adding more weight in the bottom of the plane.

It's just a theory. I don't fly RC yet but I do know about planes in theory.
 

xuzme720

Dedicated foam bender
Mentor
#5
I wouldn't add more weight. That's making a bad problem, worse. One thing to try, and it's free, is to throw the plane harder. Go to full throttle and once it's stabilized, throw the plane just slightly above the horizon but HARD! More airflow over the wings is your best defense against torque roll.

If that doesn't work, time to put that powerpod on Jenny Craig!
 
#6
I was reading about wings on Wikipedia and came across one interesting piece of information: flat, symetrical wings (like the ones used in the Flyer and almost used in the Delta) are ver inneficient and in reality are only used for supersonic flight.
This statement is both correct and incorrect at the same time. What it fails to take into account is scale. The size of a wing relative to the size of an air molecule has a huge effect on how it behaves. The speed of a vehicle also effects how it behaves. This is reflected in a dimensionless unit known as the Reynolds Number. Vastly simplified, the Reynolds Number is the product of the wing chord and airspeed. Model airplanes have very short chords and fly at very low speeds, so they have very small reynolds numbers. Full size aircraft have very large wings and fly at high speeds, so they have a very large Reynolds Number. The airfoils that are appropriate for small Reynolds Numbers are vastly different than those appropriate for large Reynolds Numbers.

It turns out that at small Reynolds numbers, a flat plate airfoil really isn't all that bad. It can be improved by adding undercamber, and thickening the leading edge, but not a whole lot. This is why slow flyers like the Old Fogey can generate so much lift with such a simple airfoil.

It is worth noting here that when you add more weight, you need to increase airspeed to generate generate more lift to balance out the weight. As you increase the airspeed, the Reynolds Number increases, and the flat plate airfoil is no longer appropriate.
 
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engineer

Senior Member
#7
Wow, rockets, I did not expect a Reynolds Number answer (vastly simplified indeed!). I had not considered that a 8x4 might push the flyer into turbulent flow. However, I think the Delta is using a KFm2 step, which is not a flat-plate, and in low Reynolds number is reputed to act like a profiled wing. Again, I'm not sure that it's breaking through that barrier, but i could be wrong!
 
#8
I was mostly responding to Ivan's comment, and you are correct, this would be more applicable to the FT Flyer which is just a flat plate.

The reality is that these planes with large motors are not flying well for a combination of multiple reasons: wing loading, torque steer, the possibility of airfoil issues, not to mention CG. Each alone might not be a big deal, but put them all together and suddenly you have an un-flyable airplane.
 
#9
Thanks! Finally flew it with a smaller motor..and it flew again! Still - it's a twitch plane that likes to fly left and I'm no expert yet at trimming while in flight - or in my case: keeping the thing in the air and from nose diving into the ground!