Could MAX III fly with a 3 hp model engine ?

I was asked this when I stated earlier that the best fuel consumption 0.69 liters / hour was obtained at 89 mph ?

Here is the proposed OS 120 AX; http://www.rcgroups.com/forums/showthread.php?t=478975

It produces 3.1 hp. Not bad.

I have earlier stated that landing gear alone produces more drag ( 2 x ) than the whole ac...and using flaps ( fully ) will also multiply the drag ( 4 x ).

This MAX III has half the hp:s as the Cri Cri ( 2 x 22 hp recommended ). Which weighs around 70-84 kg empty ( original Cri Cri had 2 x 9 hp engines and weighed 64 kilos).

In order to glide fast MAX has to have retracts and half the drag of an glider. The best open class gliders have 60 kg/m2 wingloading ( around the same as
MAX III with a heavy pilot and full load of fuel ).

To reach the record braking mileage of 450 MPG the MAX has to be very clean and relatively lite in order to cruise at 1.7 hp power ( almost half of what OS 120 AX produces ). Possibly it needs also plane to be very lite built ( even 70 kg or less ) and pilot not heavier than 75 kilos + prop optimized just for this speed.

So in theory 120 AX could do it but it would have to be towed into air...and no gusts or change of wind direction that would make pilot to use more power is not tolerated either. Also the torque of the engine to drive a reduction ( normally with 22 hp engine not needed ) gear might take 50% of the engine power out so perhaps we need a good thermal to fly MAX III with a OS 120 AX. : )

Thanks for the comment.

Here is how the very lite and underpowered models fare with MAX III:


  1. Hmm... Ikävät mutta realistiset kysymykset sensuroidaan.. Ei taida toimintamatka olla enää 3500 mailia..

  2. Ei ole sensuroitu mitään realistista...mutta selvät solvaukset ja henkilön mustamaalaukset on sensuroitu.

    Nyt varsinkin on toimintamatka 3500 merimailia koska polttoaine tankki mahtuu runkoon ja siiven suureneminen pienentää indusoitua vastusta ( mikäli foilivalinta oikea ).

    Se, että mikä on potkurin ja voimansiirron tehohäviöt, vaikuttaa eniten kulutukseen. Jos vaan kone ei enää yhtään kasva ja rakenne säilyy hyvin kevyenä ollaan edelleen hyvin liitävässä kevyesti moottoroidussa lentolaitteessa.