----[Please read http://ercoupers.com/disclaimer.htm before following any advice in this forum.]----
Syd, I used to teach propeller aerodynamics, and this is one of the points that Fred Weick himself studied in his days as a propeller aerodynamicist. Fred did wind tunnel tests on propellers at the speed of sound, and the compressability effects which occur at that speed cause more drag than they do thrust- so the propeller begins to fight against itself- cancelling out what it is trying to achieve. There was an early turboprop/jet combination (one of them is on a pedestal at Bakersfield airport) which had a geared prop on the nose. It resembled an F-84G, but had a short stubby propeller with really fat blades. Didn't work too well. Also, Hamilton Standard was developing an "unducted fan" for airline use, they tested it on a DC-9 and it was able to achieve a propulsive efficiency of about 85%. This is the highest propulsive efficiency ever achieved, but that efficiency could only be realized at Mach .8. It too had short stubby blades, but were scimitar shaped, and had variable pitch- which proved to be it's demise. The idea has not gone any farther.......yet jan z fresno ca On Mon, 11 Dec 2000 20:13:43 -0800 Syd Cohen <[EMAIL PROTECTED]> writes: > ----[Please read http://ercoupers.com/disclaimer.htm before following > any advice in this forum.]---- > > The X-1 is a tricycle gear airplane. The X-15 landed on skis. And > my understanding of prop planes and > the sound barrier: In order to get the airplane that fast, the > propeller blades have to exceed the > speed of sound by quite a bit, and as soon as part of the blade does > exceed the speed of sound, it > becomes ineffective due to the shock waves that build up around it. > I also may be wrong about this, but > that is what I once heard. > > Syd Cohen > > Mike Dean wrote: > > > ----[Please read http://ercoupers.com/disclaimer.htm before > following any advice in this forum.]---- > > > > Didn't X-1 land on skis. And I do believe they were in a trike > configuration. > > Please correct me if I'm mistaken. > > > > As for a prop job breaking the sound barrier. There is an mention > in this months > > Sport Aviation about a group that is planning on building a > composite version of the > > Bugatti that hangs in the AirVenture Museum in Oshkosh. They plan > to try to exceed > > Mach 1 with it. Not to say I believe they will, but they say > they're going to try. > > > > Seems I read somewhere that, among other reasons, propellers could > never get enough > > bite to exceed Mach. If you turned them that fast the blades would > simply get lost > > in the wake of the blade in front of it. Sound familiar to anyone? > > > > Mike > > > > -----Original Message----- > > > > Yes, but if you remember, when 'Chuckie' did this he didn't take > off with his rocket, he was 'air > > launched'. And as for the 'controlled crash' (taildragger > landings) I don't remember and I don't have > > time right now to look it up as I'm about ready to leave for town. > Was the X-1 a trike or a > > taildragger? Not his '51, it'll 'never' break the sound barrier. > No prop-job ever has yet anyway. > > > > Gotta run....... > > > > Bob > > > > __________________________________________________ > > To unsubscribe from this list please send > mailto:[EMAIL PROTECTED] > > > > ___________________________________________________________ > > T O P I C A http://www.topica.com/t/17 > > Newsletters, Tips and Discussions on Your Favorite Topics > > __________________________________________________ > To unsubscribe from this list please send > mailto:[EMAIL PROTECTED] > > ___________________________________________________________ > T O P I C A http://www.topica.com/t/17 > Newsletters, Tips and Discussions on Your Favorite Topics > > __________________________________________________ To unsubscribe from this list please send mailto:[EMAIL PROTECTED] ___________________________________________________________ T O P I C A http://www.topica.com/t/17 Newsletters, Tips and Discussions on Your Favorite Topics
<<attachment: winmail.dat>>
