You talk about fast and slow. I went through this with my KR in the early 90. We all did. Most found out it is not how fast the air enters the inlet but the differential between inlet and outlet pressure. We installed 2 airspeed indicators 2 digital thermometers and 2 manometers (I think that's what you call them to measure pressure drop) We started lowering the bottom lip of the cowl under the plane. We found that once the pressure built up in the cowl the airspeed through the cowl did not change much when we picked up speed. To make a long story short we lowered the bottom cowl 3" below the firewall and 1" past the firewall and cured all our problems. This was on a VW 2180. When I installed an 0-360 lyc on my 47 Bellanca (Removed a Franklyn 165) we had to lower the bottom cowl to get the bigger engine cool. Someone mentioned the air going from the bottom up, There were a few airplanes in the 30's 40's and early 50's that pressurized the lower cowl. The original Bellanca 14-13 had the air going up through the cylinders.
--- On Mon, 12/7/09, Dene Collett <av...@telkomsa.net> wrote: From: Dene Collett <av...@telkomsa.net> Subject: Re: KR> New subject - This is not KR!-- now cooling systems, general To: "KRnet" <kr...@mylist.net> List-Post: krnet@list.krnet.org Date: Monday, December 7, 2009, 11:27 AM No offence taken but if I am not mistaken your aircraft has an aircooled motor in it and has a cooling system to keep it cool while the engine is producing power. Although I am not installing the motor in a KR, it is aircooled and has a cooling system which I would like to understand. I would have thought that the commonality between the two would make the subject pertinent here but maybe not on the corvair forum as that forum is dedicated to the corvair motor only?? Then again the corvair has been used in many different aircraft and each one of them has a cooling system..... A lot has been said about the ratio between the inlet size and outlet size but not much has been said about the relationship between power produced (heat), inlet size and airspeed. There has to be a relationship and a rule of thumb formulae there. According to a study I recently read by a german aeronautical engineer, the traditional cooling systems are upside down. According to her testing the lowest pressure area around the circumference of the cowl is on the top and highest is in the centre on the bottom. Obviously with higher speed aircraft like the KR ram air is enough to overcome this but the slower you go the more difficuilt it gets to create that pressure differential required. Look at the outlets on a cirrus in relation to the power (heat) they produce. They are tiny. The secret is airspeed as far as I am concerned. I am sure there are VW powered KR's out there producing no more that 65HP with bigger inlets and outlets. Either the owners of these KR's just hit the cooling bug with a big stick and overengineered it to avoid problems or the inlets and outlets had to be bigger due to the lower airspeed and therefore lower ram air pressure. Fortunately the KR flies fast enough to be able to create a lower pressure underneath in the higher pressure area to "suck" sufficiently. Take Mark Langford's KR for example. AT 100MPH the ram air pressure is already 4.92" water guage, at 120mph it is 7.09"wg.(figures obtained in an old sport aviation article) This alone is probably enough to cool the motor without worrying about creating an outlet system to help "suck" out the air. So, in theory, to cool a KR in cruise the outlet can be at static pressure and it should cool just fine providing the inlets are correctly sized to let enough air in and the outlet size is sufficient to handle the expanded air. It is a little more complicaed that this I know but this is basically how it works.(as I understand it). Comments??? Regards Dene Collett Avlec Projects cc Port Elizabeth South Africa _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
