Brodhead Pietenpol Association

Original Posted By: "John Dilatush"
John writes:>we would predict a rate of climb of 1056 fpm!>Yet he gets only max rate of climb of 700 fpm and sometimes less>This might indicate that his horsepower ratings are somewhat>optimistic.Well, I didn't want to over-inflate the claims that William makes, but they are there for the world to see on his website at http://www.flycorvair.com. Based on the actual, measured static RPM and actual, measured thrust that William's plane was getting, it developed more like 110 HP. The point was, as Mike Cuy explained, you need to know your plane's limitations based on what engine you have bolted to the firewall because there are things you just can't do with 65 or less horsepower up there. I will also point out that the climb rates that William stated were with passengers, in the busy traffic pattern at SNF. You really don't want to be climbing out at best climb in traffic or with passengers if there aren't any obstacles to clear, due to reduced visibility over the nose and speeds nearer to stall. Given that the plane was not being operated at best climb, the stated climbs were pretty good. William quoted some climb numbers higher than this to me but I didn't use them in my post because the point was made without them.To the rest of the folks on this list, be aware that John is running a turbocharged Subaru with a redrive, so his Piet will have truly stellar climb performance and if I were him I would challenge that Warner-powered Piet to a climb contest! And if I may again state my innermost feelings about the quintessential Piet image, it is of a plane that has a radiator out in front and an inline Ford 4-cylinder driving the prop!Oscar ZunigaSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________

Original Posted By: "Oscar Zuniga"
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Original Posted By: Mike Hardaway

Original Posted By: "Mike Hardaway"
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Original Posted By: "John Dilatush"
Sorry that I haven't followed this conversation completely, cause I justwalked in the door 2 hours ago from 5 days away.This debate comes along every year or so, and just wanted to throw in my twocents.If you look at sites estimating HP of certain engines, what they tell you isthat it's just physics, you can only get so much power out of a certaindisplacement engine, give or take, without supercharging, at a certain RPM.period. That's it.My Mentor, who has been in the business for alot of years, is very muchagainst these claims of high HP from a Corvair. He has built a few gearreduced Corvair engines, that put out more HP ( and wanted to gear them morefor more HP)His estimate of output for a nongeared Corvair is , I believe, around 50 to60 HP at normal prop. rpm. Think he said that they are very smooth whichgives you the feeling that it is more powerful.waltPS My a-65 piet climbs at 700 FPM, and I'm still smiling----- Original Message -----

Original Posted By: "walter evans"
50-60 hp at normal prop RPM's?? I assume you mean cruise??....even at cruise I KNOW the 'vair gives more than 60hp.DJ----- Original Message -----

Original Posted By: "DJ Vegh"
DJ,No , I think this is overall. He's not new to Corvairs, been working withthem for years. I'm not sure of the numbers, I can ask him next time I seehim.walt----- Original Message -----

Original Posted By: "Chris"
The Pietenpol airfoil as several others mentioned is something thatPietenpol came up with himself. I was curious how it compared to otherairfoils so I worked up a set of coordinates based on the published plans(and smoothed, as shown in the plans leaves a bit to be desiredmathematically as measurements closer than 1/32 for plans are not verypractical.) I then fed the coordinates to XFOIL, a rather nice CFD airfoilanalysis program with a neat viscous flow solver. Also, I had to guess abit at what the shape was at the leading edge as the plans are not verydetailed in that region. The data and coordinates are on the Air Camperpage within my personal web page which can be found at:http://www.angelfire.com/va2/aerodrome/It is a high lift/high drag airfoil as one would expect from a low and slowflier.Kevin Holcomb----- Original Message -----

Original Posted By: "Gene Rambo"
For what it is worth a late (1964 and newer 164") Corvair engine with .060oversize cylinders has approx. the same cubic inches as a Continental A-65,A-75 and A-80(170").The A-65 is rated at 2300 rpm and the A-80 at 2700 rpm.If the Corvair is no more efficient than the antique Continental it shouldhave approx 95 hp at 3100. We flew our plane for 160 hours with a Corvairwith a stock cam and then installed a C90-8 with 0-200 internals.The contwas lighter and had more torque and a longer prop and it would climb betterbut wouldn't go any faster and it used more fuel. Bill> His estimate of output for a nongeared Corvair is , I believe, around 50to> 60 HP at normal prop. rpm. Think he said that they are very smooth which> gives you the feeling that it is more powerful.> walt> PS My a-65 piet climbs at 700 FPM, and I'm still smiling>________________________________________________________________________________

Original Posted By: "Kent Hallsten"
Sometimes all the numbers and formulas really confuse my tired old brain,but I can add this.I had the pleasure to ride in Williams Corvair Piet at Brodhead, Gus was thepilot and as mentioned he is a big guy. The main thing I remember is the wayI was pushed back in the seat at the beginning of the T/O roll.I have had rides in about a dozen Piets and GN1s and Williams had by far themost seat compression.I don't remember anything about climb, guess I was too excited.I do remember that Williams Corvair was also the quietest Piet I have heard,you could hear the prop, and almost nothing else, when it flew overhead atsomething less than pattern altitude.Skip, still working on L/G and turning my hubs.....even at cruise I KNOW the 'vair gives more than 60hp.DJ> against these claims of high HP from a Corvair. > walt________________________________________________________________________________Subject: RE: Pietenpol-List: AirfoilDate: Tue, 10 Dec 2002 09:15:26 -0600