I have the RAF48 airfoil with the Diehl wings, but I really don't think that that has much to do with the plane lacking stability at higher altitudes. ?My plane has 1 foot more span on the tail than Joes, and an extended cord on the rudder with a forward strake on the vertical stab. ?I flew my KR for 500 hrs with original KR-2 tiny tail. ?I thought it lacked stability at any altitude, although it is rare that I ever get to fly below 8500'. ?
Since I am based above 7000', I modified my plane to perform where I normally fly, which is usually 8500 - 13,500'. ?I have taken a lot of criticism for the mods I've done to my plane as apparently every time I talk about stability, I end up calling someone elses baby ugly. ?I usually end up descibed as inept pilot that needs a plane that handles like a truck. Something else to consider is that service ceiling is defined as where the plane stops climbing at least 100 fpm on a standard day at gross weight. ?While several of us can climb our planes to incredibly high altitudes, I would bet that in most cases, it was a cool or cold day and the plane was loaded pretty lightly. ?I know I did that on Dec 24 with a pretty light load of fuel and not much else in the plane. ?Those numbers are just for bragging. ?The reality is, that on a a standard day loaded at gross, those of us with big engines are usually good for 15 or 16,000'. ?However, what you really need to know is how is the plane going to perform on a hot sticky summer day while enroute to the Gathering loaded at least at gross while you are dodging cloud tops with weather closing in underneath you. ?For me under those conditions, if the weather goes above 13,500', I'm looking for somewhere else to be. ?I can get higher, but usually the weather is going up faster than I can climb. ?I generally don't carry O2, so don't spend much time above 13,500 anyway. Jeff Scott Los Alamos, NM > ----- Original Message ----- > From: Larry&Sallie Flesner > Sent: 03/24/14 04:56 PM > To: KRnet > Subject: Re: KR> Service ceiling > > At 05:04 PM 3/24/2014, you wrote: > >Amen to that! Trying to fly a squirrelly plane is why I didn't take > >note of the 100 fpm point. At that kind of altitude, the max > >attainable indicated airspeed and the stall speed get awfully close > >together, so it's a fine line between stalling and climbing any higher... > >Mark Langford > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > You and Joe both fly the new airfoil. I wonder if the RAF 48 handles > the same way. Jeff Scott, what airfoil do you have and how does it > handle at that altitude? > > Larry Flesner
