Polars etc

[kd6veb]

Hi Gang

I spent a little time nearly 2 years ago on the published Phoenix polars. To obtain the best L/D for the glider draw a tangent to the polar curve from the origin. With both sets of polars that I had then the best L/D for the 15 meter wings came out at 28.5 and for the short wings 22. I checked those results with reviewing long glides of IGS files with SeeYou on a PC. I found pretty good agreement overall.

My perception is that the most touring motor gliders have best L/Ds between 25 and 30 and that the Phoenix is as high performance as any touring motor glider. We do give up performance because of side by side seating. fixed undercarriage and a non retractable prop. The disadvantage compared to a high performance glider is that you have to spend more time climbing to make up for your increased sink rate. That's one of the reasons I have purchased a DG1001M. Glide is 46 compared with 28.5. An XC to the Whites can be done in a significantly shorter time than with a Phoenix. Regardless at this time I am keeping the Phoenix which I enjoy immensely as a high performance power plane and a glider as I commute between San Jose, CA and Minden NV.

Dave

[No longer active on TMGA]

My Phoenix (30:1) will have to thermal more often than my ASH 26 E (50:1) and it won't go as far, but I'm hoping it will let me have soaring flights I can't or won't make in the 26 E. Two examples come to mind:

• traveling to the waves that are 90 NM upwind - the 26E can't fly fast enough to get there before it's out fuel; the Phoenix will get there twice as fast and still have hours of fuel
  
• straight out distance flights, which the 26E can easily do, followed by a fast trip home the next day, which the 26E can't do
  

The ability to quickly travel to remote soaring and easily return from it afterwards will, I believe, often compensate for the lower performance by providing more overall "fun value". The Phoenix will also have an unfair advantage: it will have a hangar, so I can be ready to fly much sooner and more easily than the 26E, which I keep in a trailer.