When I flew the Dakota slotted wing Cub I was also very impressed. I was seeing 22 mph stalls on the ASI even at low power and wing angles. I though "WOW these slots REALLY do work, this is almost TOO good to be true". After a few minutes I pushed the excitement aside and though "wait a minute, this IS too good to be true"!
I then turned the GPS on and aligned the plane directly up wind and did a number of stalls at different power setting and wing angles. Then I turned directly down wind and did the exact same power settings and wing angles. Averaging both sets of stall numbers, the VERY best I could get it down to according to the GPS was 38 mph with lots of power and a very steep wing angle.
My theory..... the slot, when "open" (steep wing angle), diverts a lot of the normal under wing air pressure, up through the slot and away from the pitot tube. This gives you a 30% incorrect ASI reading and makes you think you're really stalling at 22 MPH.
Fact: a set of Dakota slotted wings weighs 58 lbs more then a set of stock Piper wings. In order for them to be of ANY benefit, they have to produce an additional 58 lbs of lift to offset "themselves". I'd guess they would also have to produce that (58 lbs), plus another 150 lbs of lift before you'd notice any REAL difference in your airplane's performance. And this "additional" lift is subject to the slot being open (steep wing angle) and producing, a varying proposition at best.
When in the take off phase they're not really "open" until you rotate and at that point you're already ready to fly anyway. On landing you're slowing down so much that there is less "high speed air" flowing through the slot and when you flatten the plane out to land so you don't hit tail first, there is little to no additional lift being produced because they're effectively closed. You now just have the additional 58 lbs, mounted WAY up high that you're trying to slow down and not nose over, and it ain't helping matters. At some point you have to get your and the plane's weight moving forward STOPPED.
On floats I think they're a different story. Climbing on step they're "open" and producing.
This is just my un-educated opinion and personal observations and again no slam on the manufacturers of these products.
When I bought my Dakota wings I could have purchased a set of Dakota slot wings, no problem. The Alaska Dakota rep at the time basically said "for wheel / ski work, forget it, for floats they're the ticket for getting off the water short".
Take care,
Crash
)
The Great Debate: to slat or not to slat that is the question?..............8)
