Thorp Air Command - T18.net

Believe it or not, we have used the 2x4 and sledge hammer method to "massage" the radius from pointy to more round. Be careful and you won't have to use too much Aerodynamic Smoothing Compound. Working the trailing edge of the ailerons can also produce surprising results.

_________________
Bob Highley
N711SH
SN 835
KLAL

Just build new wings. I read in one of the newsletters that it only takes a weekend to build outer panels from scratch. LOL!

(I think there was a lot of marketting done in the old days.)

So I borrowed your advice(s)
and added one more.
I biffed the leading edge back with this hammer and a Duct tape covered 2x4.
I could add some ultrlight fairing compound to inprove the profile.
I could add a leading edge cuff from aluminum sheet like the STOL kits sold for CESSNAs

Yikes!!! I don't think sledge hammers are allowed around airplanes!!!

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

Worked on the plane D. R. is presently flying.

_________________
Bob Highley
N711SH
SN 835
KLAL

Well it did work, in this case.
I spent the morning at the airport, put the wheel pants on and made a template from 1" foam board.
I Biffed the leading edge with a duct tape covered 2x4 and the KO hammer, while comparing leading edge profiles.
Marilyn and I went test flying.
The stall, power off (well, really 1500 RPM) was lowered from over 70 to about 66 MPH with less wing & pitch drop. Next, 1 notch flaps + 64 MPH, 2 notches flaps = 63 MPH.
The 2 Notch flap stall was the most controllable.
The wheel pants were a very happy suprize. Full throttle @ 2500 ft increased from the 152 MPH without, to about 164MPH @ 2600 RPM
The leading edge reprofile will be ongoing, but the first attempt made the plane mo-betta.

As a self professed master of the sledge, with more practice than I care to admit, I never, EVER would have predicted it was possible to modify the flying characteristics of an aircraft in a "positive" way through the use of that (now defined as precision) tool.

I am profoundly humbled.

WOW ! Bada Bing, Bada Boom !

RB

Hi Scott, I too had a left wing that was a little heavy, especially when I flew solo. I put a elec Tab on the left aileron, fixed it. Some just use a fixed tab, this is very simple and you can keeper Flyin . Dan

I may employ that tab, but right now I'm onto the next step:
I called out the local CFII with some Thorp T-18 time, and took him on a familiarization flight before I sent him out to teach Marilyn, who is also a CFII, but all in Cessnas. I breifed Darrell on the wing and stall situation up to this point.
We had a good time, with higher ceilings, we decided to work those stalls a bit. The clean stall was as described eariler today, but the 1 notch flaps stall got our attention on recovery during the second evolution: as I recovered with quicker but less profound control, there came a buffet like we should have gotten before the stall, then it cleared as speed increased. Darrell commented on a possible secondary stall, and we set up for a third try at 1 notch flaps low power. This one we wanted to play around in, some rudder, some aileron, to see what we would get. Well, after the stall break with left wing down, I did a minimal recovery and got the buffet again, and stronger than before, followed by a strong secondary stall that required some definite forward control before the roll to level. Not sure about the rudder position on that one...although I'd been careful to keep the ball centered as best I could up till then.
The stall with 2 notches of flaps is much more controllable, with no apearant secondary this time
I'm reading the NLs on stall strips....which N883FF does not have.
Darrell wants to see this improved before we start Marilyn's transition training.

Mr MacPhee, Rich Dan and all, Thanks for the pointers on final approach and round out.
Now that I have some improvement in the left wing, your numbers are very good.

My little 2 cents, for what it's worth -

1) It hardly takes any time, effort, or material to put stall strips on. They should all have them.

2) Keep in mind the shape of the leading edge as it is shown on the drawing when making these adjustments. That's the shape to strive for on both wings.

d

Bruce Finney went flying in his fine ship today, and we met at 883FF for some brainstorming; he has some plans I can reference.
Today I tried 2 things:
1) Stall strips
2) Leading edge
the strips really changed the stall profile, just as advertised, except 883FF still drops the left wing, and worse with 2nd notch flaps, although, at quite low indicated airspeeds of about 65, 63, & 61 @ 1500 RPM.
There is good stick shaking warning, but also a lingering secondary with quite a sink rate until power is added, then when it hooks up again the climb is suprising. Like 1000 fpm DOWN becomes 1000 fpm UP.
These are the basic 6" long 3/8x3/8" balsa triangle sticks from the local aerospace hardware store, held on with packing tape.
I would like to try John Thorps reccomended 8" long 1/2x1/2" strips too.

The leading edge cover didn't work out so well. On climb out, I noticed some of the Duct tape pulling away in a small area on the inboard side and the top.
I stayed in the pattern, extended long for a Cessna and landed, keeping the speed down.
It DID make a difference, and the landing was the slowest touch down yet with out left roll in the flare or anything.

You might want to try a larger stall strip on the wing that stalls last (or a smaller or no strip on the heavy wing) to convince both wings to stall at the same time. Your stall speed will never be as slow as if both wings had the fatter leading edge but it might work to get it to stall straight ahead. Then just live with the slightly higher stall speeds or build a new wing on the heavy side with the proper radius (or biff it a little more)!

Bernie Fried
N18XS

883FF got a workout today.
I added 2 home made vortex generators to each wing, took it for a flight with 10 gallons gas, then filled it and tried twice at gross weight, with the wife and with Darrell the flight instuctor.
The change was profound. The 3 stall speeds did not change, but the ailerons retain effectiveness.
When it stalls you can pick up the left wing with aileron, one time. Then it will stall with a forward pitch, and left roll pretty mild. If I recover with minimal forward stick to regain roll, the A/C settles into a stable decent at up to 2000 fpm! A shot of power and a speed gain of 10 MPH reattaches the wing, and it climbs away.
Top speed at 2500 ft was the same or reduced by no more than 2 MPH. It's hard to tell, but at 4000' TAS worked out to 171 MPH.
The picture shows the 3/8x3/8" x 6" balsa stall stip, and 2 "Hall" type Vortex Generators .4" tall x 1" front to back. The have a 20 degree angle on each blade (40 degrees between the two on each VG)
They are placed with the trailing edge @ 12% of cord, measured over the skin. The inboard VG is 2" outboard of the panel fairing, the second one is 12" outboard of the first.