Thorp Air Command - T18.net

Just getting around to researching this forum. I was a Navy guy and the A-1 (AD) Douglas Skyhawk outlived the F4U Corsair. The A-1 was designed near the end of WWII and saw extensive use in Korea and Viet Nam. The last A-1Hs (AD-6s) were decommissioned by VA-25 at Lemoore Naval Air Station in April or May of 1968. They transitioned to A-7s. The Air Force operated A-1s (some as Sandy missions where one pilot earned the Medal of Honor) until the end of 1972 when they were all transferred to the Republic of South Viet Nam Air Force. 2 A1-Es operated as TWA (Teeny Weeny Airlines - liaison airplanes) out of VA-125 in Lemoore NAS. One was lost in the Sierra Mountains in 1969 (both pilots survived), but the other was still flying until I left that squadron in September of 1970. I think that was the last operational A-1 in the Navy. Other countries operated the A-1s until the mid '80s.

The Phantom was an awesome airplane! The Navy and Air Force got a great deal on them. Lot of bang for the buck. The F-8 was probably the best air to air fighter, but the F-4 could do it all.

Sorry for the thread drift!

Marty Vanover
Tucson, AZ

Hi all,
I'm interested in building a S-18 with a folding wing. Reason - our hangarage costs in England have shot through the roof. I'd like to keep it at home and trailer to my local field - about 2 miles away. My only hassle is that my garage has a 7'6" width opening, so I am considering making a narrow wing centre and keep the wide body. Wing length will be adjusted to compensate.
Does anyone have a video of the wing folding process? or a procedure?
Does anyone tow (at <30mph) by simply putting a towbar onto the tailwheel fitting and pulling the Thorp in reverse?

all comments welcomed

Thanks
Graham

Hi all,
Thanks for all the answers and interesting points. The GAW-2 aerofoil could probably be improved with modern CFD to soften the stalls.
Back to my original question. What's the procedure for the wing folding and does it take 2 people? I'm interested in the practicality of doing it for each flight , say once every 2 weeks?
Thanks

It was designed to be done by one person. Although it is easier and safer with two.
You remove a small nose section via one screw.
Then you pull a pip pin on the aft spar.
Next you lift the pin lock and hammer out the main spar pins.
Then disconnect any pitot or electrical.
Go to the wing tip and pull out and lift.
If you rotate the wing trailing edge down, it stays attached at the aft universal
If you rotate it leading edge down, it comes off in your hands.
It is not heavy, but it is awkward. It is 72+”long and 50” in chord.
Cubes

If you go to my gallery you can see pics of my folding wing set up . As Cubes said it was designed to be a one man operation , but I did the wing fold/unfold operation for about 8 years and kept the A/C at home on a trailer in my hangar workshop/garage (next to my other 3 car garage ! ) You can never have enough garage space ! The trailer was modified from a Gus Gordon trailer design and travels very well at max freeway speed of 55 MPH . Once at the airport I would go from fold mode to flight mode with the help of my wife . She was more of a "safety person" to help hold the wing until I got the bad boy locked into the flight mode. Once into the flight mode I would just give the rear end a shove and the A/C would roll off the trailer down the 3 ramps . Going home I could do the operation solo and winch the A/C back onto the trailer with a 12 volt Harbor Freight 12 volt wench . Once on the trailer I would position a Harbor Freight adjustable roller stand under the wing tip to support it (just in case mother nature had other ideas !) . Then I would remove the gap cover , pull the quick release pin on the rear spar , lift the lock lever and use the plans built pin puller to remove the 2 main wing pins . Pull the wing out from the main fittings slightly , then pull the wing out until the U-joint hits the stop . Rotate the wing and move it to the rear of the trailer and place it in the cradle , rotate the wing support up and then cinch up the ratchet strap around the wing and secure it to the trailer . Same goes for the other wing . I left enough slack in the pitot static , lite wires so I did not have to disconnect them . Attach the (4) ratchet straps to the (4) bottom eye bolt on the belly of the A/C . Slide the ramps into the slots on the trailer , lock um down and then head home ! It would take me about 20 min. to off load and on load the A/C . This was after a few attempts to get my act together . A few years ago a hangar at KSEE became available so I jumped on it , but the 8 years of home hangaring saved me $500 x 12 x 8 years = $48,000 . If the time comes where I would need to bring the A/C home I can still do that ! Thank you Gus Gordon !

RB
NX115RX
2019

Responses in no particular order...

1. The aft spar on a regular T-18 wing just keeps the aft end of the wing from going nose up/down. The aft spars are connected by a single bolt and can rotate around the bolt. All bending moment is handled by the main spar. (As a number of people have noted).
2. The classic NACA airfoils all have a flaw in how the leading edge radius is laid out. I accidentally stumbled across this back in the early 90s when I tried to plot a 4412 airfoil on CADAM at work. The program could not draw what should have been a smooth curve and it kept "kinking" (for want of a better term) when trying to draw the top of the leading edge. I kept thinking that I was doing something wrong. I later realized what I was seeing when I started seeing articles in Kitplanes and other magazines, and the airfoils that guys like Roncz (sp?) and Riblett had developed. And, as I later learned, Lu Sunderland, who relofted the T-18 airfoil from the main spar forward, and did a fine job of it. And apologies for not knowing who did what and in what order for the newer airfoils.
3. Blunter is gentler when it comes to stall, for sure. The "sharper" leading edge of the original airfoil doesn't necessarily cut through the air better, since so much else goes into the overall drag.
4. If I'm recalling correctly, John Thorp's distinctive wing configuration (also seen on planes he did like the Fletcher) does two things:
a. It simplifies the fuselage carry-through and keeps from having the main spars crossing under the pilot's legs to create dihedral (or a huge bending moment at the side of the fuselage)
b. Minimal wing root drag by having the wing come out of the fuselage at a 90-degree angle.
5. At one Thorp gathering, there was an old(er) timer who mentioned learning to fly at Mines field (now LAX) and he noted how with the original wing and landing gear, a T-18 was barely at stall in a 3-point stance. Pertinent to not much of anything else, just posting for posterity.
6. FWIW, when I bought my kit, the outer wings were built, and I rebuilt them to Lu's airfoil, and built the center wing to match. I'd much rather have better stall behavior than a few extra knots at the top end, but there are other factors such as how well everything else is built and lines up that I don't think the LS airfoil is going to be noticeably slower. I could be wrong, but I'm not going to worry about those last few knots.

YMMV