I have the new UCanDo SF and just started the build. It has SFG's that bolt to the wingtips, nothing unusual here. What is odd though is that the SFG's and wingtips are not parallel to the fuselage. The SFG's (and wingtips) point in towards the nose of the airplane quite a bit, maybe more than 5 degrees. What are they thinking? Anyone ever seen SFG's that have tow in like that? Looks like it would cause a lot of drag in straight flight! Ideas anyone? Thanks. http://www3.towerhobbies.com/cgi-bin...DUJC&P=ML#tech

Wing tip vortex generators or SFGs have the same function- when air approaches a thick wing, it doesnt like to go over but slides sideways over the wing. This washoff combined with the tendency of high pressure air at the wing tip to roll over the wing tip into the low pressure air above causes the tip of the wing to stall earlier. SFGs simply prevent that by acting as a fence. In the older UCD 60, this same effect was achieved by the triangular wing tips. These days is probably more "fashionable" to have SFGs, not triangular wing tips.

The toe in is probably there to line up with the air washing off. If it was not toed-in, the sideways force acting on the SFGs would simply snap them off. Remember, the idea is to straighten the airflow, side force is only in name.

This type of airplane is mostly a stunt airplane, not meant for flying circuits. If you intend to do that, dont install the SFGs. Its meant to be be flown mostly in one place, silly as it may sound, mostly in the vertical plane. If you fly too fast, the air going over the top surface will separate from the surface causing intermittent pulses in pressure. This will cause tug at the ailerons causing flutter and will lead to a crash

Ameyam

Ameyam

Thank you for the thoughtful reply. It sounds right on in every way. BTW, I sent an email to Great Planes and they contacted the designer. His reply was that the toe in was intentional and that it is there to provide added lift in KE flight. I have mixed feelings about that. If the KE flight has a high AOA involved, the bottom SFG would be providing the lift I think, and that sounds less stable to me than if the top SFG were providing more lift and "holding the plane up" rather than "pushing from the bottom", the plane up. What do you think? and thanks!

It looks to me that would be best if it had toe out.

What power are you putting on the UCD SF ?

The UCD SF had a lot of thing I like in a airplane.

Toe out would just add drag. Plus, it would generate low pressure pulses on one side in straight & level flight- just like a wing at high AOA & this would finally snap off the SFG. SFGs add stability in straight & level flight by acting like additional rudders & add rudder authority in KE.

SFGs arent new. Most of the Airbus and Boeing airplanes have had them for over a decade. Just look for the wingtips on these airplanes- Airbus has flat wingtips just like SFGs where Boeing has tips that curve upwards. Both have the same function

Ameyam