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Flaperons and over driving a motor

#1
Information 1:
I custom built a carbon fiber bodied, foamboard wing plane and it flys fast...because it is so heavy. Not a big deal except on landings. So I tried dialing in some flaperons and it gets really squirelly. I am using a Spektrum dx9 and setup flaperons. It is a pretty short plane. Here is a little video of my first flight / crash. I had other successful flights after I stopped using flaperons.

Question 1:
What is the starting settings you use to get a mix going. I started with 30% flaps with 8% elevator. Is this way out of line? Suggestions?

Information 2:
For another build, I am doing a carbon fiber stick with wings, single motor. I have a 2204 on there now and it flys, but that motor is too anemic for my taste. I have lots of 4s 1500mah batteries and that is what I am flying it with now. I am thinking about swapping out that motor for another I have sitting around(see link). The problem is it is only rated for 3s.

Question 2:
If I down propped it to say an 8 or 9" prop do you think it would take a 4s? If you think it would burn up what percentage of chance? If it is a 90% chance of burning it up, I will get another motor. 10% chance of burning it up? I'm probably going to run that chance.
 

TazRC

Obsession, not hobby
#2
Hi Merck,

For 3S vs 4S question:

According to HURC, Current rating for the GT2215/10 motor is: 24A Max or 280W for 30 seconds. If you put a wattmeter on it with a 4S and try different props, you might find a prop that runs within those specs.
 

quorneng

Well-known member
#3
Merck
If you get and use a Watt meter you can reduce the chance to zero that you will burn up a motor.
'Trial and error' is fine for many things but for high powered electric motors (which is what RC flight motors are) it is a poor (and expensive) method.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#5
Merik,

Those aren't insane numbers, but are they the right ones? No easy way to tell without flying it. I've had compensation mixes that are fairly aggressive (high single digits) and I've had them very sedate (a point or two). Depends on your airframe and the relative throw of your surfaces.

So how do you find "right"? Go fly. You're flying Spektrum, so set the flaps to a three position switch, then set clean to the top (0%, 0%) and 30% flaps to both of the other steps . . . and I'd say go 4% elevator on the first, and 8% on the second. Go high, get into a cruising speed, click down one position and let her settle into her new cruise holding the elevator to force her to fly level. Are you giving her nose up/down to keep her flying level? Keep in mind where you're holding the elevator. Pick up some more altitude, click the second position and settle. Did it get better, worse or did your manual elevator trim change direction?

If you nailed it, and one of those positions settles into a level cruise after a second or two, you've got your setting. If it got worse going to setting 2 "right" is below setting 1. If it swapped, it's between 1 and 2. If it got better, it's above setting 2. Land (using the best setting you have -- feel out your stall speed and behavior while you're up there) and adjust the two settings to narrow in on "right" and fly again.

Ideally, you'll pull the switch, see the plane balloon a bit and settle back in to a slower level flight without touching the sticks or trims.


Since this transition can be a bit harsh, I do recommend you slow it down -- I typically set my flaps to deploy over 2s. It's a bit of personal taste -- I have friends who set it to instant . . . but personally I feel it makes it worse when you fall into the trap.

What trap, you say?

One point of caution: Flaps on landing can be a trap. When you deploy them you can safely slow the plane well below the typical stall speed of the plane -- it's the whole point of flaps for landing. If your landing is running long, it can be tempting to retract the flaps a bit.

DON'T DO IT.

If you've slowed to "just above" the deployed stall speed and retract the flaps you've just hard-stalled the wing . . . and down you go . . . with no altitude to recover. Rule of thumb -- on final, flaps only go out, never in. Only pull them back in after you land or speed up (not just throttle up) to abort.
 
#6
Crafty Dan! How dare you use logic to solve my problem!
Love it. So much great information. Thanks for the HUGE and great explanation.