Replies to This Discussion

Permalink Reply by Tim Garrett on May 21, 2014 at 8:47pm

Very interesting! I used to slope soar RC sailplanes so I know what your saying. I just wouldn't have expected a 750 (low aspect ratio wing) to be able to do much with it. What speed would you be expecting at 2850 rpm without the ridge lift? Do you know what angle of attack you are at with and without the ridge lift at the rpm?

• ▶ Reply

Permalink Reply by John Austin on May 21, 2014 at 9:15pm

I'm slats-off, 600 series tires, so a little cleaner than a stock 750. Usually see about 82 kts TAS @ 2850. The wind was reported at KCSV at 11 kts gusting to 19 kts and the wind was not perpendicular to the ridge, more of a quartering tailwind relative to me and the ridge. So let's say the constant wind speed was under-reported (the reporting station was about 20 miles away) and be really generous and say I was getting 15 kts from the wind. That would boot the ground speed up to 97 kts and I was showing 107 kts (123 mph !!!) on the GPS.

I can't give an exact angle of attack, but, just as we do in sailplanes, I definitely had to trim the nose down to maintain level flight, which of course accelerated my groundspeed. So all that is to guess I was getting the last 10 kts from the ridge lift?

But heck, that's nothing! In the ASW-20, I've hit 110 kts IAS in level flight on the same ridge, and that's with no engine!  ;>)

John

• ▶ Reply