The Olympic 99 uses a modified NACA 6409 with the trailing edge stock placed flat on the building board which gives a slight reflex to the true 6409. Lee Renaud derived the Oly 99 wing from the with the Thermic 100 wing.
A bit of moldie-oldie trivia... --Bill >From: [EMAIL PROTECTED] >To: [EMAIL PROTECTED] >Subject: Re: [RCSE] Predator configuration, Oly II airfoil >Date: Fri, 05 Jan 2001 05:02:23 -0600 > >At 09:13 PM 12/4/2001 -0800, you wrote: > >Didn't the Oly II have an E-205 airfoil as did most of the earlier > >Airtronics sailplanes and gliders? Larry Jolly should know the answer to > >this puzzle. > > Jerry Miller > >No. I am not sure but I think the original Olympic used an undercambered >airfoil. The Oly II used a true flatbottomed airfoil similar to the >Drifter and Sailaire. The Aquilia used a modified E387 while the Sagitta >used a modified E205. The undercamber was removed from both while the >leading edge radius of the E205 was increased. I compared the modified >E205 and E387 airfoils to the true airfoils about 20 years ago when I was >first started developing my airfoil plotting program. Not sure exactly why >the modifications but I remember Lee mentioning that he liked to increase >the leading edge radius to improve the stall characteristics. I also know >he sometimes modified a design so that the components would fit into >existing kit boxes rather than to stock two different boxes. > >A side note on airfoils. Back in 1978, I designed a trainer for a fellow >club member who was interested in switching to sailplanes but was short on >cash. I used a shortened fuselage from my unsuccessful 1976 F3B model and >needed a quick airfoil. (This was 5 years before I wrote my first airfoil >plot program.) I was impressed by the nice handling characteristics of the >Sailaire so elected to use a similiar airfoil. I didn't have coordinates >for the Sailaire airfoil so I measured the leading edge radius, maximum >thickness, location of the maximum thickness, and trailing edge angle. I >scaled the measurements down to a 10 inch chord and connected the top >points with a No. 64 french curve. The reason for using that particular >french curve was that I knew from previous models that the shape of that >particular curve was very close to the E387 top surface aft of the maximum >thickness when plotted to a 10 inch chord length. The resulting model was >named for the star, Spica, and the typical sailplane landing. The Spica >was my most successful sailplane design and I sold about two dozen >semi-kits over the next few years. > >I always refered to the airfoil used on the Spica as a Generic California >Flatbottom airfoil because of it's similiarity to a lot of the airfoils >used in sailplane kits of that era. When Michael Selig began his original >Prinston wind tunnel tests of model airfoils, I suggested that he include a >typical flatbottom airfoil as a baseline airfoil for comparison. He >thought this was a good idea and ask me to build a wind tunnel model of my >airfoil. The name was too long so the name was changed to the model which >used the airfoil. That's the way the Spica airfoil came to be in Michael's >first group of airfoils published in SoarTech 8. > >Now for the rest of the story. A few years later, I was surprised to read >in a Hobby Lobby ad that one of the models they were imported used a >computer designed airfol called the Spica. After a little investigation, >Jim Martin confirmed that the German manufacturer had obtained the airfoil >from SoarTech 8. So, for all you Xfoil users, that's the way we did it in >the good old days. > >Chuck Anderson _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
