Wow! I have a new airplane now.
Yesterday I started the day with testing my Sky Ranger without VG’s. Stall clean, small flaps, full flaps, no throttle and with 3.500 RPM + landings in same configuration. Then I mounted VG’s according to your advice, 7% chord from the tip of a VG.
Then fly tests again.
First of all, much to my surprise I noticed much bigger stall speed difference on 3.500 RPM than with no throttle. The plane was simply hanging on his prop at the speed of about 50 km/h (and to be honest although it was still stable I had no courage to push more due to the awkward position of the nose, it was never so high before).
The difference in stall speed with no throttle was clearly noticeable, but not that big, about 4-5 km/h less before the gentle and very short actually nose drop.
So, coming back to the airfield I assumed: “O.K., there is clearly some difference, though not that dramatic after all”. And I was wrong! The real difference was during landings. It’s like on the air cushion. First time in a Sky Ranger I was able to touch the ground at the speed below 60 km/h. And keep 70 km/h on the approach. I would not advice it to anybody, but I have to say it was very safe feeling now to fly very slowly with full flaps and some throttle just over the grass as if in PPG. Next I tried to level up a bit higher and the next time to simulate a mistake of ballooning after the first touch of the main gear. In both cases the plane had a nasty habit to test the landing gear after breaking too high. It used to jump high after such event like a kangaroo. Not after installing VGs. Apparently they help to remove bad habits (have you tested them against smoking by the way?). Now the plane smoothly touches down even from pretty high level up or balloon. Again, I do not recommend anybody to test those potentially dangerous positions of the aircraft. But I have to say this: they don’t look so dangerous now. Amazing.
I dare say that with VGs Sky Ranger would outperform CH701 in every respect being very docile and nice in (new) flight characteristics.
Good job JG, I got my money worth.
27 Apr 09
I have another Sky Ranger by now and installed another VG set (I had bought from you twice).
This time I installed 20 on each wing with 6 cm distance to each other, tips 7% from the leading edge. The rest – with 9 cm distance – I installed in slightly V shape, putting the tape about 2% backwards close to the fuselage.
The results are as follows:
1. I can fly solo 45 km/h with 2.200 RPM (Rotax 912S) with no break
2. I can fly solo 50 km/h with 1.800 RPM. The very gentle stall comes at around 45 km/h then.
3. With the full load and with my friend – instructor on board, at 3.800 RPM, the plane flights at no IAS – the angle of attack is so high the pitot tube works no more. The GPS indicated 26 knots GS at no wind. Then we make quite sharp turns at the speed around 55 km/h. At this speed and fully loaded the plane turns like on rails remaining far away from spin.
John, you made me much happier pilot. Now, with tundra wheels, I feel like I can fly and land anywhere. I touch the ground at 55 km/h and the front wheel I keep up even below 50 km/h. Snow, sand, mud, soft field – no more of a problem. Alternative landing spot is thus practically anywhere, if only the area is free from trees, fences and grid.