Geoff Bye 2

Hi All.   just seen Richard Hammond explaining how the A380 is based on a mongolian eagle with a bike pump for legs.   Anyway, interesting the way he used an aspirator to increase the gas flow into a large simulation of an inflatable slide.   i always remember the test beds at Rolls Royce when i worked there.   when running an RB211 the jet efflux is directed up the detuner with the result that the airflow around the engine being drawn up the detuner by the Aspirator effect was incredible.   i remember some aluminium scaffolding being picked up from the side of the bed and blown up the detuner and out onto Sinfin golf course.   anyway where is all this going?   i was wondering if anyone has tried using an aspirator in the airstream from an EDF unit.   just wondered before i shell  out for the bits for an experiment that might not work.   regards   Geoff

Hi All.  been learning to fly with Midlands flight training and need to get a plane now really.  i like the idea of a large stable plane, so i've been looking at the Protech Ibis.  what do you experts out there think of it.  Also need a club in the Derby area to join that does IC and is accepting new members, any thoughts anyone.  did a search on the BMFA site and only got DRCF at Ashbourne which is a big club and not taking newbies on. i have plenty of time to fly in the week as i work from home, but weekends are a bit stuffed.  any thoughts folks.  all help gratefully received  Geoff

Hi Phil, nearly. as the wing has thrust from the engine, pushing the ball up the hill gains potential energy in the ball. this potential energy can then be used on the way down the hill.  work is done by the engine so energy is added to the system which can be converted to lift energy.  and as force =pressure X Area. the area of wing that has a pressure increase is smaller than the area that has a pressure decrease so the net effect is positive lift.  regards Geoff

If the don't arrive at the same time there will be a shortage of air above the aerofoil and that means a vacuum. This is my whole point. the velocity of ball 1 and 2 is the same in the direction and relative to the arrow and therefore they arrive at the TE at the same time ball 1 only moves up and down relative to ball 2. as ball 1 is pushed up the slope the pressure increases, as it goes back down the slope it is pulling the wing up to meet it. like a camshaft pushing down a valve

Thanks Phil, i'll accept it doesn't matter which bit is moving.  But going back to my original question. The ball is moved up and out of the way in a vertical direction. so how does the ball suddenly get some energy to accelerate backwards. it must accelerate along the surface of the wing for Bernoulli to be valid. as the velocity has to increase for the pressure to drop. or is it just that due to the curvature of the wing the molecules are accelerated up and down more and therefore the their vertical velocity increases, reducing pressure.  regards  Geoff

i agree in terms of drag, but not in terms of lift generation.  consider this. we have a flat plate angled down at 45 degrees. and a tennis ball aimed at the middle of the plate. firstly the tennis ball is fired at the plate which is static. the ball will be deflected up and over the plate and carry on behind it.  now we have the ball suspended in space and move the plate at the ball. the ball will now move up and forwards away from the plate as we have now accelerated it forwards in the same way we hit a golf ball.   so you see the relative motions are the same but the effects are different due to which part has the energy. Geoff

Think of how a cheap air brush works........blow fast moving air over an open pipe with one end dipped in paint..........it sucks the paint up the pipe........The faster moving air over the top of the aerofoil sucks the wing upward.  this is where my problem comes in. With an air brush you have blown the air over the pipe. the compressor inputs energy to the airflow and accelerates it.  in the sky the air is not moving backwards at all and what force accelerates the air as energy will be needed to do this.  in order for the relative speed of the air to go up the wing will have to slow down as it is the only thing moving forwards.  confused as ever. don't do physics but am a chartered engineer with own engineering business designing engines. Geoff

My Personal theory is this.  Bernouli has little to do with lift generation. as the air is not flowing. what force is applied to the air molecules that would cause them to speed up around the top surface, if they have further to go they should just arrive later than the below molecules.  if you blow over the wing then bernouli does have an effect as the air has velocity and thus can be accelerated around the curvature, in the same way a venturi works in a carb. and you actually have something imparting a flow regime in the air such as your lungs putting energy into the air.  there are 2 forces primarily at work.  firstly the angle of attack ( AOA ) is effectively compressing the air under the wing generating some of the lift,  hence why a flat plate angled up will generate lift.  Secondly, as the wing passes through the air, the molecules of air are pushed up and out of the way, this is drag. as the molecules now try to re-attach themselves to the curved surface as it falls away, (coander effect) the wing is sucked up to meet the pulling down of the molecules ( Newton ). If the curvature is too great or the AOA is to steep the coander effect is not sufficient to maintain attachment to the surface and flow seperation occurs.  Regards Geoff ( anti bernouli league )

Hi All. Just been reading the article in Novembers RCME about how aerofoils work and got me thinking on an old problem i have with it all.  My problem is this.  all the theory assumes air flowing over the wing.  But this is not the case for a flying machine. the air is static ( no wind) and the wing is moving through the air.  If the air is not flowing how can bernouli have an effect.  The molecules of air can only be moving up and down with the profile of the wing as it passes by. so they have no rearwards velocity with which to speed up and slow down to change the pressure and thus give lift.  the molecules of air have a relative velocity to the wing but the body of air is still not flowing.  please someone put my mind at rest. and i've got me tin at on just in case.  regards  Geoff

put me in the draw too please

I can thoughouly recomend Colin Chapman of midlands flight training. really nice guy and a superb teacher, he puts up with my poor flying while i'm learning.  He operates around welingborough area so is quite close to you i think.  Give him a call for a chat about it on 07711 963939.  He'll probably be flying, but will call you back when he's landed if you leave him your number.  Geoff, (also learning)

first time entry for me. regards  Geoff