ArmedZagi

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I got the building bug after I saw the article "Lateral Manuvering Explained" in MA magazine 2 months ago... The wing has 580in^2 and the winglets have a total of 112in^2. They have a ground clearance of 2in. I figure if it becomes a necessity I can make piano wire skids for them. If I use them I'll make it so they attach with wing bolts or machine screws.

Took them out to the field yesterday, didnt wind up using them. Everyone at the field had a diferent opinion as to what they would do. Some say it would increase roll rates, and make the ailerons more sensitive. Others said they would slow the roll rate from the extra weight at the tips of the wing.

I thought they would increase rudder authority, provide extra lift on knife edge, and reduce the severity of this planes tip stalls. So whats the deal, what will they really do?

Heres a few pictures of it. In the pics the winglets arn't attached, their only held on with T-pins.

mesae

Why don't you fly it and let us know what they do?

ArmedZagi

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I'd rather know what to expect before I tried...never re-kitted this plane in 50+ flights and don't want to start now . I guess what I'm asking is, could this modification make the plane unflyable or unreasonably difficult to control?

mesae

Very unlikely.

The only potential danger I can think of in adding side area like that is if too much area is added forward of the CG. In that case, it's possible to have divergent yaw stability (ask me how I know). Your extra side area is distributed fore and aft of the CG so I don't see any controllability issues with your mod.

Those plates have at least two unrelated functions: Inhibition of spanwise flow and additional lateral area for maneuvering. Judging by the large size of your plates, you were going for both, which is fine.

Based on an article we have all read, I am considering adding some much smaller temporary tip plates to my Giles, to see how they do. The plane already knife-edges extremely well, but the claims that tip plates can reduce or eliminate wing-rocking in harriers and clean up snaps have intrigued me. I can do decent harriers with this plane but they are not easy, and the snaps could do with a bit of cleaning up.

ArmedZagi

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Cool, thanks. Think I'll try them saturday..if my new tx battery comes in by then...

mesae

Let us know how it goes!

ArmedZagi

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I finally worked up the nerve to fly the Extra with the winglets on today... The difference is unbelievable, I was only able to make it tipstall when I cut the throttle all the way back and pulled full up elevator. It WILL NOT tipstall inverted, I tried. It will knife edge at less than half throttle now. It taxies marginaly better. And I no longer need aileron coupling with rudder, only minor corrections from wind.

The most incredible change however, I can get it to hover. No joke ( I have witnesses! ). I've never gotten it to do that before...I'm not sure how the winglets affected this...Maybe the extra weight on the tips made it more stable? It's still not a fantastic 3D plane but the change is undeniable.

They do have a couple of (not terribly) bad effects though. Rolls are slightly less axial. However I found that down elevator takes care of this. Landings are obviously more difficult from the 2" clearence below the wing...but I can live with that.

Not everything went right today though, my scratch built no name plane went in from about 60' today. The front wing bolts finaly pulled through the balsa. I did have the presence of mind to put full down elevator in it to finish breaking off the wing and tail feathers which floated nice and easy back to earth (I didnt feel like rebuilding EVERYTHING). It survived better than I excpected and it should be flying next weekend, if the new servos come in from tower...I stripped two of them. Everything else to fix I have here at home. I'll put washers under the wing bolts this time.

Heres a couple pics of the wreakage...

Edit PS: When I first flew the Extra with the winglets...My hands were shaking worse than on my first solo

proptop

My Feedback: (8)

Nice AZ...hey, try some flat turns w/ just the rudder. You might have to fight a little bit of roll couple with the ailerons, but you should be able to do some new manuvers with tip plates that big![8D]

mesae

Hey, thanks for sharing that. Did you try any intentional snap rolls with it? I'm very curious as to how those are affected by the plates.

ArmedZagi

My Feedback: (1)

It snap rolls almost as well as it did before I put the plates on...however it loses speed faster through them now. Before when I did a snap roll with full deflection it would make it through about 4-5 revolutions before the rolls slowed way down...now it slows in about 2.

Also, I forgot to mention in my post above, the overal effectivness of the rudder was increased by... I'd have to say 50-70%...Flat circles were MUCH tighter...

I still cant get over how different it flies. I definatly recomend these to anyone with a plane similar to this. At least try it, if you dont like the change you can always take them off...

mesae

I wonder if that's due to the extra drag of the tip plates while sideslipping in the snap. It's useful info. I'll want to be careful not to make mine too big.

What elevator deflection did you use in your snaps?

ArmedZagi

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As in degrees? I'm not positive what its set at....lemme go check...

...25 degrees is what its set at on full deflection (25 degrees up...not total) thats more than enough on this plane. I used to have the elevator set with 40 degrees...but without a radio with the capability of Exponential... it got a little twitchy on landings. Now that the wingtips are on I might start bringing it back up.

mesae

Thanks. I suspect 25 degrees is more than enough for a deep (both wings fully stalled) snap roll if your CG isn't too far forward. If you snap with less deflection, you might find it retains more energy. Full-scale aerobats use just enough elevator to stall the inside wing - meaning much less drag and speed loss. The winglets do complicate things a bit. Don't know when I'll get to mine - have lots going on, including a potential new job and move.

ArmedZagi

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Also...I finished my rebuild on the scratch built at 12:36 monday morning...yes 12:36AM

And forgive the color scheme...I used basicly the first thing I grabbed out of the cabinet...Im thinking about adding a yellow trim line around the chrome on the fuselage...

mesae

That didn't take long. How do you like that chrome look on the nose?

ArmedZagi

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It looks alot meaner than it used to...Hopefully I wont go blind watching it on a sunny day...

Edit: I went ahead and added the yellow trim...I like it. Hadnt noticed until now..but the covering really wrinkled up over the fiberglass on top of the fuselage...