Wobbly wings - spoilers out too soon

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Includes: Highlander, Escapade, Summit and SuperSTOL.
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BDA
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Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Wobbly wings - spoilers out too soon

Post by BDA »

As I fine tune the plane I am identifying causes for minor problems.

After I found a fix for the lazy slat I was still not satisfied with the stability I had on final below 40mph.
It was still like balancing on a beach ball, a smaller beach ball now but still balancing.
The wing would overcorect for every aileron input. Very manageable but not easy to fly, and I did not have confidence in where I was going to end up.

So I got to thinking about what could cause this - spoilers of coarse.
They are very important for very slow flight, but they were coming out and affecting lift with even very small aileron input.

A couple years ago I had a discussion with an experienced SS builder when I set the spoilers and he told me to set them “1/2” or so” below the surface of the wing. But I decided to follow the manual anyway and set them just a frog hair below the surface.

Now that I have a handle on how the plane acts I decided to try what I was told before and adjusted the spoilers about 3/8” below the surface, so that they only deploy when aileron is deflected more than 2”.

Took it out for a spin tonight - in the wind.
The plane feels different for sure, it still handles well, but not on a razors edge like before. It felt like an aerobatic plane before. Now a little more like a bush plane.
On final I came in with 40mph indicated, and it was much more stable. So I pulled back to 30 and then to 25. Still flying predictably, no wobbly wings.
I was happy with it before - but now...
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
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mac
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Posts: 60
Joined: Sun Jul 29, 2012 7:57 pm
Location: Grass Valley, CA.

Re: Wobbly wings - spoilers out too soon

Post by mac »

Shawn....were you able to make that change by only adjusting the rod end towards the wing leading edge or did you have to mess with the real rod end as well? Those inspection panels on the bottom of the wing make for challenging access points with larger hands! Hee.
Mark M.
N49SS in Phase 2....for good!
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BDA
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Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Wobbly wings - spoilers out too soon

Post by BDA »

Haha
Ya gorilla arms make it a long day!
I disconnected one end and ran that end out.

Had some nasty ring marks on forearms after.
Duct tape the edge before you start.

Put more time on it yesterday, in the wind,
Direct cross wind with 10-15 knot gusts.

I was trying to practice spot landing at 25 mph, it was work!!

Felt pretty lucky to land safely at 35.

I do not think I would have been able to play like that, before the adjustment.

Dragging tailwheel down the runway to the touchdown point (diagonally with crosswind) and gust picks me up (at 30mph) to start all over
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
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mac
Seasoned Member
Posts: 60
Joined: Sun Jul 29, 2012 7:57 pm
Location: Grass Valley, CA.

Re: Wobbly wings - spoilers out too soon

Post by mac »

Thanks Shawn. Yes, gusting crosswinds are a challenge with this airplane..........as with most. Big wing, lightly loaded, certainly doesn't help! My "interceptors" deploy at about 1.25 inches of aileron travel. Might try increasing that a bit and see what happens. Don't notice too much of an issue currently, but I usually make approaches at about 40mph IAS. Not sure what touch down speeds are. Never have time to look!!
Mark M.
N49SS in Phase 2....for good!
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BDA
Veteran Member
Posts: 707
Joined: Mon Aug 22, 2016 11:25 am
Location: Kenai Alaska

Re: Wobbly wings - spoilers out too soon

Post by BDA »

Mac mine are flush and starting to deply with around 2” aileron deflection now.
SuperStol XL Alaskan With Titan 340
N331AK. Shawn Taplin
Wing extensions,Symetrical Airfoil tail ribs (NACA 21)
Mods in progress: Heavier struts, Double slotted flaps
Goal: 15mph no wind
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