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I guess I don't understand these things either but I have an opinion and it is open to flames. But this is how I see it.
It takes energy (Motor, engine, Fuel) to push anything through the air. And the more laminar flow you have on the wing the less it takes (everything else being equal). It is very hard to get that LF back to any percentage of the chord (be it 30% or 60%). But while cruising it is very important.
Looking at other airplanes, Boeings, Lears, Meridians, etc., what you see it some VG's placed in very strategic places to solve slow speed problems. To certify a Meridian it has to meet a slow speed number and when they just increased the Gross Weight of the newest one by 200 lbs (I think). They had the choice of making a bigger wing or adding VG's to lower the stall speed at the higher weight, which is what they chose. So the new VG's allow them to do that but they are not retro to the older certified models. On the Lears and Boeings you see them by the Ailerons or Flaps very far back where they get taller but on any new wing design you don't want VG's anywhere if you can do without.
For the speed loss, it is simple, you know that they would blow off if they were not glued down so it takes energy to push them through the air. Then the question is where do you get it back? I'll let the VG supporters answer that. I know of a case in South America where a guy need the VG's on his A36 to allow him to fly in and out of his 1800 ft grass field. He did an extensive before and after test and at the best altitude combination they slowed it down 4 Kts. all other speeds and alt. were worse.
It is interesting that when they certify an airplane they can claim a top speed, with no antennas, boots, VG's, or anything and then only make one airplane, such is the case with Malibu's where only one was built without boots which cost about 5 kts.
I think that VG's are very interesting engineering wise but should be retractable. So let's get someone working on that.
Why do we put our antenna's inside anyway? Winglets are in this same boat.
Keep sanding,
Jim Hergert
N6XE, "An Sex Y" L4P
Winglets, 215 hrs, no cylinders
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