Messages

2131

Misc / HQ35/12 Airfoil

« on: March 25, 2008, 07:01:33 AM »

Yes,..........I think I agree with Alan in that probably the best thing for me is to go back to basics.  :roll:  
At the moment as soon as I hear one answer, my brain, (what there is of it) pops up another question.
The problem with understanding lift is that there seems to be no black and white answers. The 'goal posts' are not fixed

Think I'll click on Amazon Books and order a copy of that "Model aircraft Aerodynamics"

As I remember it,..................... "Pi multiplied by R squared over 4', ................ take away the number you first thought of!! "  

 Hmmmm, this could take a bit of time :?:

2132

Misc / HQ35/12 Airfoil

« on: March 24, 2008, 08:39:13 AM »

I've found a Clark Y airfoil diagram, still can't find a Go535 though. :x

2133

Misc / HQ35/12 Airfoil

« on: March 24, 2008, 08:15:58 AM »

Hmmmmmmmmmmmm :?:

Firstly Fred I have to say I'm very impressed with you being awake at such an early hour of the day.............very good :clap:

Now I'm starting to get confussed, which is very easy at my age!

Could you tell me please where I might be able to find a diagram of a Go535 and a Clark Y profile?

You see, I'm thinking if simply having a later stall and offering less drag is the only advantage of a symmetric wing over a plank, why not have a semi symmetric wing with slots in the LE. Surley they reduce  the stall yet offer less form drag than a symmetric wing.

2134

Misc / HQ35/12 Airfoil

« on: March 24, 2008, 06:30:32 AM »

Right...................... (I think :?: )
So now we come to the core of the matter, Fred.

A symmetric wing produces no lift at 0 degree of incidence, the same as a "flat" wing produces no lift at 0 degree of incidence. They both only produce lift by deflecting air downward. Neither wing produces any induced lift

A non-symmetric wing produces lift by both deflecting air downwards, via the underside of the wing, AND produces lift from the camber on the top of the wing. (What I call 'induced lift')

Assuming what I've just written to be true, Question; Why does any one bother producing a symmetricaly cambered wing when, according to the above, it flys no better than a plank of wood?
Why aren't all wings semi-symmetric or flat bottomed? They produce far more lift. (Induced and reactive lift)

I know there must be a reason for symmetric wings, but I just don't know what it is.  :!:

So come on Fred, you aerodynamic guru,..........hit me with the answer!

2135

Misc / HQ35/12 Airfoil

« on: March 23, 2008, 21:35:20 PM »

I'm thinking of a symmetrical wing. the camber on the top is equall to the camber on the bottom. Assuming zero angle of incidence and zero angle of attack where does the lift come from?

2136

Misc / HQ35/12 Airfoil

« on: March 23, 2008, 20:44:27 PM »

So Fred, you're saying that the shockflyer merely deflects air in one direction and the wing "reacts" in the opposite direction? like a rudder perhaps?

2137

Misc / HQ35/12 Airfoil

« on: March 23, 2008, 20:37:06 PM »

Okay,.............Thanks Fred, and you other guys, for replying. I must go away and think about this. It's all very interesting stuff. Hmmmmmmmmmmmmm.................!

2138

Misc / HQ35/12 Airfoil

« on: March 23, 2008, 20:27:04 PM »

Yes,..........I'm fine with the concept of lift being derived from having pressure exerted on the underside of a wing. As I remember from my school days (circa 1897) about 25% of a wing's lift comes from air 'hitting' the underside of the wing.
However. I'm sure we were taught that 75% of the lift comes from air having to travel over the greater distance over the top camber of the wing and thereby ahving to travel faster than the air traveling under the wing This causes a reduction of pressure on that top camber due to what I think was called the "Venturie" effect. (The same effect that causes petrol to rise from the float chamber in a carburettor. But let's not get bogged down with internal combustion engines. Horrid smelly things.)
This then leaves the wing with relatively higher pressure on the botton, and relatively lower pressure on the top, hence LIFT.

Am I right so far???

2139

Misc / Where does the lift come from?

« on: March 23, 2008, 16:40:22 PM »

Okay chaps,

If the lift from an aerofoil is suposed to come from the camber on the underside, how does a flat bottomed wing creat lift?