Not with Lithioum cells.
I just had a peek at an example cell - E-tech 1200. Now that is 1.2AH at
3.6V roughly - will tolerate 5A, and peak at 10A (just) so that is 36W (peak) of cell and weighs in at .85oz.Compare with a Nicad sub C where you get maybe 50W of power at 2 oz, but will flatten it in about 3 minutes trying, and you can see that the LiPos are ahead on power density by a factor of two, and on energy density by about FIVE.
So about 60 of those in series/parallel will get you the battery power - thats 51oz of pack, or a shade over 3lb. In fact you wouldn't use those - the Thunder Power Lipos are bigger but I don't have definite data on em.
I'd guess another lb or so for the motor, giving a total of about 4.5lb of power pack to equal a 3bhp motor, AND most importantly, gearable too, so that the prop efficiency can be totally matched for either speed or thrust, depending.
I'd guess that would be a close match for a 180 size engine.
Throttle it back to half power and its good for 15 minutes.
AND it won't wear out, make a racket,deasdstick without warning, has (almost) infinite throttle control and won't generate slime, or consume expensive fuel. Bearings eventually go, but not that fast. No side load. Just thrust by and large (although some gearboxes will put a side load on).
If it wasn't for the cost, there would be no technical reason - just a few emotional ones - to ever buy an IC engine again.
Ahnd if these thiungs DO get the volume (and LIPOS have come out of laptop computers and cellphones, PIC controllers and power FETS are commodity items from the switched mode power supply industry, and the motors are just miniature three phasers, or mass volume produced itemns that go in power tools and electric windows etc..) then the prices WILL come down. There is far less machining on a brushless motor and far less assembly than on a big 4 stroke, the controllers are just a board stuffed with electronics, and lithiumn batteries are ultimately not expensive on materials - just a huge amount of R & D to get over costwise.
Nope, the days of 'slap in a cheap .40' are numbered. It will be 'slap in this integrated motor/controller and plug in this pack, and stick an
11x6 on it and go fly'I remember when model shops stocked flat rubber motors.
In 20 years IC engines will be as rare as wakefield motors :-)