Thorp Air Command - T18.net

My T-18 stalled at 54-55 mph with 2 notches of flaps (approx. 20 deg.?). That was at around 1500#. It had (has) the "standard" wing, with Sunderland airfoil, and was eventually 968# empty - it was lighter at first, but gained quite a few pounds (about 30) in 28 years. They did make a small difference in the stall... I'm sorry that I don't have any firm numbers. They also resulted in considerably more ground effect, resulting in slower touch down speeds. I did flight tests when I built them, installing one on the left wing and leaving the original Thorp tip on the right. A considerable amount of left stick was necessary to overcome increased lift. The stick force was measured with a spring scale, but I don't remember what it was anymore - I documented all of that, but can't find it now... drives me crazy. Some of it may be in the old newsletters. I had a good amount of time in the bird before installing them, and then somewhat over 1000 hours with them. I loved the feel of them on my T-18.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Hi Guys,

I still haven't got the airplane home due to weather etc. but the owner that rebuilt the machine a few years ago, 2015, says that it weighed 1212 empty and now with the change of prop' to a CATTO it will have lost 60lbs so I am looking at an empty weight of 1150lbs. The handbook copy that came with it says that it stalls at 80mph clean and 77mph with full flap. Those speeds have been verified as correct by others that have flown it. All a but quick. I see VG's in my future and a few tire and tailwheel changes!!
Speedbird 1.

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N872DD
200hp Lycoming

Speedbird1,

I haven't checked the forums in a few weeks and missed your request for comment on DD. Sorry about that. Congrats on your purchase. It's has a bunch of great features and I'm hoping you'll enjoy many hours flying it.

More later on my thoughts about it, but it flew great when we took it to TPF. It just wasn't the right setup for me at the time.

Congrats again!

Speedbird1,

I have VG's on my plane on the outer wing panels and just forward of the rudder. They did not change the stall speed but really tamed the stall to a mush from a sudden, no warning event. I also added the stall strips to get a stick shake prior to stall. The VG's on the vertical tail reduced the dancing on the petals upon landing. I did not notice any change to cruise speeds with the VG's. Also when I am in ground affect I have total aileron control at low speeds. They are the ones out of Australia made by a company called Stolspeed.

My plane stalls at about 65-67 mph flaps up. Less than that with 30 degrees flap.

Sounds like you will be able to lighten it up a bit by looking at light weight started, smaller battery and removing older legacy stuff.

Regards,

Jim

Hi Guys,

I still haven't got the darned thing home to Montana yet, what with weather and silly paperwork issues that will be fixed easily, but I am off to the hospital next week, so it will have to wait.
Dr, Drift. I would like to see your pictures and comments, please, via PM if you have time??
Speedbird 1

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N872DD
200hp Lycoming