Is there a thrust to pound ratio to use as a rule of thumb????
i am converting a gas plane designed for a .25 engine my current setup is giving 16 ozs thrust
plane weight is almost 3 lbs rtf or am i looking for something that doesnt mean anything
plane is basically a trainer type
fairlynew here
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I think there was an article last month in the AMA magazine by Bob Aberle that had the information you are looking for. If it wasn't last months, it was within the last 2-3 months. I don't have a copy of the magazine with me right now, but if you get the AMA magazine, take a look. I'm sure what you are looking for is there.

a "basic" rule of thumb is 100w electric per pound..... obviously quite a bit more for 3D, etc....

but that gets you into the ballpark

thanks but the watts per pound deal and how to calculate has not gotten thru to me yet
could you elaborate???

Figure out the weight of your aircraft, ready to fly. (include the weight of batteries and motor) Then, multiply the weight (in lbs) by 100. Forexample: an 8 lb. airplane would require 800 watts.

ok is this watts being used at full throttle or available watts
how do i calculate the # i need
do i use ampmeter on wire going to motor??
as i said this is getting by me
sorry for multiple posts but my puter said it want going thru

We're talking about Watts at full throttle, or available Watts. Same thing.

As a general rule of thumb, 100 Watts per pound will give you roughly the same performance as a glow engine. Doesn't matter how big the plane is. 3 pound plane? 300 Watts. 15 pound plane? 1500 Watts. All you need is a good estimate of how heavy the plane will be when it's ready to fly. Most airplane kits come with a weight range specified on the box. Go with the highest value on the box, maybe even add 10%.

Watts, Amps, and Volts are always measured at the battery, at full throttle. That's where the rule of thumb is based.

The reason we don't really care about thrust is that it's only half the picture. You can have a 2lb airplane with 8lbs of thrust, but there's the possibility that it won't fly. Yes, it'll hover and go straight up, but it won't FLY. Why? There's also a SPEED component to the thrust from a propeller. If the speed component is less than the stall speed of the airplane, the airplane's wing won't make lift, and the plane won't fly.