My airfoil Tail

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

Re: My airfoil Tail

Post by BDA »

Time for an update-

What this airfoil tail will do that seems better than stock(from memory):
- with a little flap it will fly the tail while taxi with little to no forward stick.

- when light, it will take off from 3 point

- on very slow approach to land if I use about 50% throttle the tail has enough authority to fly down the runway keeping the main wheels about 6’ off the ground while dragging the tailwheel on the runway at less than 25 mph indicated - it is rediculous!

- I can fly the tail with more than 1,800 pounds in the airplane

- I can land VERY short with the tailwheel well below the mains and maintain “level” flight below 30 indicated at more than 1,800 pounds gross.

- I can flare and touch the tailwheel at under 30 indicated, then fly away.

- it is fast, I have confirmed that I can do more than 115 mph in cruise.

The bad stuff:
- It is heavier than stock, I did not have to add weight to the tail section to make weight and balance.

- i have to use trim in level flight when empty, but it does not seem to effect my top speed.

My comparisons are just from memory, so if your plane will do these things as well, post up so we can compare.
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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BDA
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Location: Kenai Alaska

Re: My airfoil Tail

Post by BDA »

Update on the tail:
I have been very happy with the large airfoil - but - I had hoped for more…
When very slow (below 30mph) with very high aoa, the tail would still “drop out” with no warning, causing increase in aoa, which caused the wing to stall.
This is what I noticed with the other SS I have flown and was hoping the airfoil would eliminate this.
So I added VGs to the top of the stabilizer about 1” back from leading edge to see if that would keep the tail from stalling when really slow. It worked!
Now no matter how slow I go the tail never drops out first.
And with power I can go even slower and higher aoa than before. Hard to give a speed because airspeed inicator is lying at this speed anyway but I have seen below 20 on gps.

The other intangible is more stable and predictable.

My theory is that below a certain speed, the plane requires less downforce at the tail, at that point the tail can actually carry part of the load of the airplane by making lift.
But only untill it stalls - and the superstol tail sees VERY high aoa. So to keep it flying I made the leading edge of the horizontal airfoil a large radius and put VGs there to keep the air attached to the top.

I know this is very non-standard aerodynamics, but it is working. Very very well.
Clark in AZ
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Location: Cave Creek, AZ

Re: My airfoil Tail

Post by Clark in AZ »

Very interesting. Thanks for the pirep. What do you think of VG's on the bottom of the horizontal?

Thanks,
Clark
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BDA
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Location: Kenai Alaska

Re: My airfoil Tail

Post by BDA »

Yes, VGs on the bottom are a deffinite advantage.

I put them 3” in front of elevator hinge line
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BDA
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Location: Kenai Alaska

Re: My airfoil Tail

Post by BDA »

VGs on horizontal stabilizer
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