M100S

[B Sharp]

Robbie, I was also worried about the effectiveness or lack of when I built the frise ailerons on my 1:3.5 scale Oly 463. I shouldn't have bothered my little head about them - they handled exactly like ailerons - they banked the model perfectly.
Brian.

[RobbieB]

Hello, hello, hello! What's all this then?

I just knew it.................................

Brian, it's the large gap that I have concerns about. On the full size you can almost get your hand all the way through from bottom to top. Surely can't be doing the wing's efficiency any favours? Not to mention how far the leading edge of the up-going aileron protrudes below the bottom of the wing.

Shroud fitted:

[Peter Balcombe]

Robbie,
I thought that the large amount of up-going aileron LE droop below the wing surface was the main point of the Frise aileron, in order to create drag on that side to counter adverse yaw.

I would have thought that the increasing amount of gap as you go out along the aileron is also likely to be intentional.
Maybe the intention is to take air from the high pressure side of the wing at that point to reduce lift - helping to drop the down-going wing, or even to blow it over the upper surface of the aileron?
I’m sure an aerodynamicist could explain all.

[John Vella]

Sorry if I am teaching you the obvious Robbie, but here we go . In normal flight the leakage is minimal. On application of a normal aileron the upward going wing on a high AR glider produces more drag than the deflection of the downward going wing due to operating in higher pressure air. This ADVERSE yaw can be overcome usually by differential movement. However the FRISE aileron provides an equally effective solution. On application of upward aileron movement the leading edge does two things by increasing drag (Good for adverse yaw) and vents high pressure air from below the wing to the top of the aileron increasing the downward rolling force. This system is about control effectiveness not just efficiency, especially at higher angles of attack. Regards John.

[B Sharp]

Robbie, the top surface gap on my Oly 463 is negligible when there is no aileron deflection but the gap between the lower LE of the aileron and the lower wing surface is rather more substantial. This is in order to allow the lower nose of the aileron to rotate upwards into the wing when the surface is deflected downwards (if that makes sense).
When the surface is deflected upwards there is a very substantial portion of the aileron nose protruding below the surface of the wing as well as a mighty gap. This is due to the position of the aileron pivot points on the lower surface of the aileron. (pivot is in the scale position) At the same time the gap on the upper surface between the aileron and the wing opens up and you get a good view of the grass below.
As I said before I was concerned as to the handling and effectiveness but it turned out ok. As john said, the whole point of the frise arrangement was to create drag as well as negative lift. However this is only partially effective in my model and also the full size machine. On my model I still have to put in a chunk of rudder to avoid adverse yaw. This is exactly like the full size Oly463 where it was normal to lead with a bootfull of rudder on the turns to keep the initiation sweet (if my memory serves me well).
Brian.
P.S. I am cleaning up my models at the moment. I will try and get some pic of my ailerons later today and post them here if it helps.

[B Sharp]

I checked my Oly463 wing this afternoon and took a few photos as promised. My memory of the gaps was not as accurate as I thought previously. However the amount that the nose of the aileron protrudes below the bottom surface is still quite significant. I hope this is of a little help Robbie.
Brian.

[Geoff Pearce]

I checked my Oly463 wing this afternoon and took a few photos as promised. My memory of the gaps was not as accurate as I thought previously. However the amount that the nose of the aileron protrudes below the bottom surface is still quite significant. I hope this is of a little help Robbie.
Brian.

Looks like a good cleaning job Brian

[RobbieB]

Thanks for the interest and the comments guys and the photos Brian.

I am familiar with the principle of frise ailerons in all their guises, it was just a little nervousness regarding the performance in the case of the 100 - that gap being so big and all.

The aileron has a sculptured LE and together with the hinge point being outside the lower surface of the aileron, as the aileron moves the gap remains constant throughout its travel:

...that being quite significant even at neutral.

I'm sure all will be well - as long as I get a good roll rate I will be happy as for sure, I'll need it as the those flippin' brakes have made the wings a bit on the heavy side.

[Peter Balcombe]

Nice job Robbie

[B Sharp]

I bet you had fun getting that to the correct shape Robbie.
Brian