You are amazing. Thrust, not watts! Watts is a smokescreen. You can't simply say it takes X# of watts to fly X airplane! Total BS! It takes less thrust to fly a simple trainer successfuly than a scale or aerobatic airplane of the same weight! Using your watts per pound formula is pure bunk. In the gas world, a trainer weighing 5 lbs could easily be flown on a .25 motor while a
5 lbs scale job would need a .40 and a 5 lbs 3D aerobat would do better with something even bigger still to get the right performance. THRUST is a function of pitch also. You can get more thrust (and speed) from a 8" pitch prop than a 6" pitch prop at the same RPM!
15 models? Now THERE is a real test! Try about 500 models of every size and description for me alone and probably over a 1000 for E-Power Test Labs. You know, you CAN learn something new! Ya think?
Besides that, discussions of helicopters in this dialogue is totally bogus! Totally different technology, etc. No bearing at all. All helicopters use heavily geared motors.
If you go to Horizon Hobbies website and look at the E-Flight series of motors, they are numbered to the corresponding glow engines. IE: Power 46 =
46 Glow, the Power 60 = 60 Glow. You need about 150 Watts per pound for real good performance. The page also tells you how much battery power you need.
Oh, a degree in engineering and electrical sciences..the experiences of a thousand people or so on the e-zone who fly electric models and pass their experience on..plus test data done of 30 motors and props or so over a few months..
A long time back, before I became the "consummate" skilled RC pilot that I am now, (harrumph! ) and I was trying to takeoff in grass that was too long for the short wheels and low belly of the little .15 powered Lazy Bee. I finally broke ground almost at the runway's end, and had to pull up, or crack up in some very tallll weeds.
The plane was not ready to fly yet, but I made it, anyway. Did I say that it wasn't ready to fly yet?
It went into mushing flight, and I had but a few inches between the wheels and the weeds. I pulled back more. And more. I was keeping my altitude, and it was by this time pointed almost straight up, hanging on the prop.
I stirred the sticks madly, keeping it from settling into the weeds. A few of the guys standing around were starting to turn their heads, pointing, and nudging to the next, saying, "Hey, look at this! I didn't know he could do a torque roll! Why didn't you do it a little closer to you, so you could see what it was doing?"
One of them asked, "Hey, when did you learn to do that?"
"Right now!" I replied. "It sorta' just happened!"
Well, finally, luck caught up, just as skill ran out. It finally flopped over into the weeds, after hovering for nearly a minute, I guess, but I was really sweating it. No damage, since it had no speed, and the grass was tall.
So really, not much skill is needed to hover. Lots of luck can take skill's place, at least for a minute, or so!
Ah, but it does..you just have to answer the question for yourself.
The thrust formula doesn't work either, unless you answer the question 'at what speed'
At least one can GUARANTEE that 50W/lb with a pitch speed more than twice the stall speed will actually fly.
There is no thrust figure that will GUARANTEE flight
At best it will GUARANTEE a hover.
The same thrust can be obtained with widely different powers..do you really think a 50W plane is going to fly the same as a 500W plane, just because they produce the same thrust?
Power sets an absolute upper limit on the rate of climb and the top speed of a given aircraft.
Power is the rate of gain of potential energy in the climb. Power is MEASURED in lb feet per second, as well as bhp and watts...
Power is drag times speed , in level flight.
Saying that thrust is what determines how a plane flies is as silly as saying that the tractive effort on the back axle of a stationary car will determine how fast it goes and how fast it will accelerate..its only true for the first instant. You will, for example, get the very best traction out of a 100bhp tractor..infinitely better than a 3000bhp drag car..but the car will do 230mph, the tractor a mere 15..
I challenge you to put a top fuel car back to back with a bulldozer, and have the top fuel car wing the 'tug of war'.. ;)
Power to weight governs a cars acceleration, and an aircrafts rate of climb, and power to drag governs the top speed of both. With aircraft on the wing, the drag is, at medium speeds, more or less proportional to weight. Only at super speeds does the actual profile drag dominate, and the induced drag fall stay relatively constant.
If you want the actual figures, 1 watt per lb of output power equates to
44.25 feet per minute climb rate. If your unpowered sink rate is less that 120 feet per minute, 3W/lb out of the prop will keep you aloft indefinitely.
Conversely if you want to achieve a 30 mph vertical climb, that's about
60W/lb out of the prop. Allowing for about 50% inefficiency in the power train, thats about 120W/lb.
Now measuring thrust will at some point possibly determine that you HAVE that 50% efficiency, and are not just stirring the air to no avail, but it cannot get away from Newtons laws, which tell you that if you do NOT have that power to weight you will NEVER achieve that sort of climb.
likewise, if you want a plane that will break the sound barrier going straight up, you need at least an output power of 20 times that - 1200w/lb.
In reality, because of drag, it's got to be more than that.
Static thrust is completely meaningless, because once the plane starts to move, that thrust changes. possibly dramatically.
I fly wet and the electrics are a sideline that I dabble in from time to time as a joke. That being said, the direct answer to your question is six electrics but enough wet birds to stock a small hobby shop. Smallest wet engine in my active use collection is a .15 glow and the largest a 3E -
75i..
I fly a lot, so my active engine collection is diverse. I used to fly OS ABC engines a lot, the definition of a worn out engine was when the prop would free wheel while deadstick These days when my Saitos begin loosing compression, I sell them and move on.
Wait a minute- you can take a 5 pound plane vertically easily and consistently with a one horsepower engine, about 3/4 of a kW- so this is a good rule of thumb. Maybe some f16 you heard about somewhere had 5 kW per pound, which I doubt, but it certainly doesn't _take_ that much to make a plane fly vertically. Check your facts and your attitude. Anyone who makes as many typos as do you, "Natural Philosopher," has no business quoting anything to anybody!
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