hello!

most (I'd say 60% or 70%) of the noise of an outrunner is made entirely by the prop tips. the falcon hobby 21 x 14 is ver efficient on this matter (i've been using it for like a month now. In our tests, and subsequently, my opinion, the real noise of the motor itself, say q80, q60, AXI, plett 30-10 is nothing compared to the real noise generator: the propeller. if you stand by the side of the propeller while turning and see the tip going back and forth from the propeller plane, that is generating a lot of noise. you do not see this on carbon props since they are much more sturdy.

two other things affect total final noise:

construction of the fuselage: wooden (say japanese or home made) kits are more silent than composite kits, like an integral, a spark or a Xigris. these last fuses work like a drum magnifying the vibrations in a sound box. BH made us realize this issue here in Colombia

how sturdy the firewall is: we've tried from an 1/8" lite ply one side glass laminated firewall, 1/8" lite ply one side glass laminated with a carbon rod firewall on the back, up to the 1/4" carbon fiber laminated plywood. this makes a real difference. you feel these effects specially on the integrated loop in the figure M, on the vertical 8 before the spin, etc.

but for the motor itself, alone: the outrunners are all so silent it makes no difference. even for the chinese (ok these are a little louder but not significant). when you hear an e plane at cruise speed you only hear an aerodynamical noise, just the sound of air.you hardly hear the noise of a bearing or the motor itself.

I remember my father fighting the noise in a Curare and on an Arrow while he had a Webra 61 Long stroke rear exhaust and a tuned pipe. they fought the noise a lot with the propeller selection.

Andrew, I did not mean to hijack the thread sorry...

Can't wait to see the Spark Evo on the air!

Marcelo Velez</p>