On Thursday, February 11, 2016 at 4:14:58 AM UTC-5, Bruce Hoult wrote:
On Thursday, February 11, 2016 at 4:09:52 AM UTC+3, wrote:
On Wednesday, February 10, 2016 at 8:03:15 PM UTC-5, Bob Caldwell (BC) wrote:
On Sunday, February 7, 2016 at 3:09:42 PM UTC-7, wrote:
I know this is a silly question, but I was reading an article by Dick Johnson that talked about holding a slight slip while thermally. This article was written before winglets and I was wondering if the same idea applied to gliders with winglets. Also, as for slipping to lose altitude for landing in a glider with winglets, does this place a lot of side load on the winglets. Should you not slip in landing with winglets?

Sorry for the questions, but would appreciate any help in this.

There are two other considerations:

A. The side of the fuselage meeting the airflow in a slight slip produces some lifting force.
And:
B: A bit of top rudder reduces the back pressure on the stick needed to hold your turn. That reduces the induced drag at the horizontal.

So what do you think?

Bob

I think both are a crock of stuff. Lift is better generated by a wing and top rudder only serves to make the turn rate lower than it should be for the bank angle.

The best LD ratio of the side of a fuselage is not very good, but if it's heading directly into the airflow then the lift is zero but there is still drag, which makes the LD ratio zero. Having just a little bit of yaw giving just a little bit of lift does not significantly affect the drag, so that first little bit of extra lift is for free.

I suspect that the gliders that seem to benefit for slight slip do so for 2 reasons.
First, as mentioned above, is that the slight slip in a glider with a good bit of dihedral will have the force opposing over banking provided without much or any control deflection. Profile drag and spanwise lift distribution benefit a bit.
Second is likely related to wing root separation issues which vary a lot from ship to ship. From my simple observation the gliders with larger well developed root fillets seem to be the ones that are not in the group described as benefiting from notable slipping.
One guys opinion.
UH