----- Original Message ----- From: "Harry Veeder" <[EMAIL PROTECTED]> To: <vortex-l@eskimo.com> Sent: Tuesday, February 20, 2007 7:34 AM Subject: Re: [Vo]: Re: Lifter aerodynamics
> > Yes I mean drag, but there may be other aerodynamic forces to consider. > Also I don't think the profile is aerodynamic because the boundary is not > crisp like a fuselage. > > Does gf mean g-force? If so that a percentage of the acceleration due to > gravity or a force as in force = ma ? Yes, gram force, that's about 1 cN. Yes, thrust is a force. > The fact that a certain current coincided with lift off does not necessarily > provide a comprehensive explanation of what makes it go. For example, the > current drawn by spark plug does not account for the motion of the blade > on a lawn mower. Ah but the ion wind force formula is not some empirical formula as you seem to suggest -I posted Sigmond's derivation-, and it accounts for the measured lift (=the weight since aerodynamic drag is negligible: you can see on the Excel screenshot on the Blazelabs page that the wind speed is less than 1m/s = 3.6km/h) within measurement errors. That's enough proof for me, but YMMV. > Anyway, if an accelerometer were mounted on a lifter the actual dynamic > forces involved could be estimated more accurately. You can also measure acceleration on the video (if you can find a way to view it ;-). And since the mass is known you will find the force via f=ma, a good exercise indeed. Michel > > Unfortunately I can't view the video on my antiquated iMac. > > Harry > > Michel Jullian wrote: > >> I agree that the lifter's ion [induced] wind adds to the aerodynamic drag >> during ascent (I think that's what you're saying, note you could say the same >> of a helicopter's propeller induced wind) >> >> Anyway in the case of the lifter this wind is relatively slow (of the order >> of >> 1 m/s, about 100 times slower than the entraining ions which are not very >> good >> "paddles" and not very numerous), and the profile is usually quite >> aerodynamic, so the corresponding drag is quite small. This means that in >> practice the thrust needed for takeoff isn't much more than the device's >> weight. >> >> Example (Blazelabs 100g payload lifter): total weight of lifter + payload = >> 187gf, let's see what current is needed for a thrust of 187gf. The gap being >> 92mm, by applying the EHD thrust formula: >> >> thrust in gf = 0.5*i*d with i in mA and d in mm >> >> we find that we need a current of 4.1mA (187/(0.5*92)). In practice Xavier >> found that the lifter almost took off at 4.2mA, and definitely flew and >> tensed >> its tethers at 4.4mA: >> >> http://www.blazelabs.com/e-exp14.asp (do watch the video) >> >> Michel >> >> ----- Original Message ----- >> From: "Harry Veeder" <[EMAIL PROTECTED]> >> To: <vortex-l@eskimo.com> >> Sent: Monday, February 19, 2007 9:54 PM >> Subject: [Vo]: Lifter aerodynamics >> >> >> >>> An "ion-wind" may produce enough force to let the lifter hover, but can >>> it produce enough force to let the lifter (and its expanded >>> electro-aeordynamic profile) _ascend_ through the air? >>> >>> Harry >> >> >
