Slips in turns and landing with winglets

On Thursday, February 11, 2016 at 9:14:08 AM UTC-5, wrote:
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

That would tend to correlate with early mentions of holding a slight slip in turns from George Moffat in regards to the Standard Cirrus and Nimbus II, both of which, IIRC, suffered from poor airflow around the wing roots while thermaling.

Chip Bearden

On Thursday, February 11, 2016 at 8:14:08 AM UTC-6, wrote:
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

I think there is a little more to it. It would be interesting to have wind tunnel data comparing the lift and drag of a complete glider in a pure coordinated 40 degree banked turn at CL max (ball centered, forward mounted yaw string slightly to the outside due to geometry), vs the same glider with enough slip to remove the overbanking force (ailerons neutral, top rudder). My guess is that some gliders will show a small but significant amount of drag due to deflected ailerons (which may be more than the drag of the yawed fuselage and deflected rudder), while others may be less affected.

All I know, it works good on all gliders I've tried it on - from K-21s to my LS6. It may be less of an issue with more modern gliders with smaller wings and less control deflections.

But hey, if you don't believe it, just keep on thermalling with that front mounted yaw string perfectly centered.... ;^)

Kirk
66

I was training a student in a 2-33. If you don't learn to slip that thing, you are going to land it all over the place. Let's just say I was fully practiced up on slips to land. So here I am at New Castle in my LS-6, I'm high on final, spoilers and flaps are not going to get it done, that's how high I was. So I put it in a big honking slip, didn't think about it just did it. Landing and roll out went fine, but something wasn't right, can't explain it but I never did it again, and I was shaking when I got out of the cockpit.
1. Read the POH
2. Practice first at altitude
3. remember what plane you are flying

SF

On Sunday, February 7, 2016 at 4:09:42 PM UTC-6, wrote:
Should you not slip in landing with winglets?

For the LS7 fitted with winglets (LS7-WL), the flight manual states:

WARNING: Sideslip with winglets prohibited, because during speed reduction stalling of the leading wing occurs (example: during left hand slip, stalling to the left!)

Jordan

No theory: After talking with Dick Johnson at a Hobbs contest I tried a slight sideslip in thermals in my winglet-free 20B. It seemed to help so I kept doing it. It did not help in my 27, which was designed to have winglets, so I stopped doing it.
I never flew the 27 with only one winglet and compared results turning to the winglet and away from it, so no idea if it would have made any difference or not. (PS: The only guy I saw, after landing, who had lost one winglet in flight on a 27 said he hadn't noticed any impact on his flying at all.)




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.

Go up, fly your ship, do whatever works best for your bird after testing things out yourself. If it worked for butler or AJ or Moffat, they must have known something they discovered with their particular ship. My 1-26 doesnt care all that much but I do have the advantage of being able to work the core of the core while most others dont have the turn radius to get and stay in there unless they are flying minden or marfa thermals.

The statement attributed to Dr Maughmer that winglets don't stall is baloney. They do stall and it is easy and interesting to observe by simply tufting them and watching as you increase yaw or slip in a turn.

I found on the Duo Discus XL the inboard winglet stalls at a yaw string angle of about 15-20 degrees (not sure how that corrolates to actual aircraft yaw angle). But the amount of slip required to cause the yarn tufts to blow backward was a little more than a pilot would naturally use. So Schempp has chosen a mounting angle that, while not optimum in perfectly straight flight, is tolerant of pilot "abuse." A stalled winglet is effectively a mini speed brake. Not welcome.

KS

On Sunday, February 7, 2016 at 5:09:42 PM UTC-5, 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.
Karl is more forthright, than I was going to be!
When I installed homebuilt winglets ( Maugner airfoil) on my 20E,
I set them at the recommended -ve angle to the horizontal axis
of 3 deg from the zero lift setting. Upon tufting these winglets,
it was quickly apparent that keeping them both unstalled was
almost impossible ( Note , the flow at the wingtip is not
along the axis) I added 2 deg extra negative AoI and the problem
became manageable, but I still now pay a lot more attention to
slip ( or not).

Slipping turns ( without winglets) are useful.
Years ago, flying a rented Libelle std I found climbing against the
Std Cirrus discouraging. After ballasting to aft CG and circling
with a fair amount of slip, I could climb with the best Cirrus
drivers. But they left me on the glide!

John firth; an old no longer bold pilot.