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Classic Sport Aircraft S-18 / S-18T




John Thorp retired in 1985 and took the T-18 plans off the market. Lu Sunderland, having worked with John on a wider fuselage and folding wing option for the T-18, did a complete rework of the drawings and produced plans for the S-18. The S-18 is then a redesign of the Thorp T-18. The fuselage body is 2" wider and 5" longer than the standard T-18. Also it has a newer NASA computer designed Wing Airfoil, which is stated to lower the stall speed by 6-8 knots. This airfoil also allows a more gentle stall with adequate warning. The top and cruise speeds remain the same. An S-18 with an 160hp Lycoming IO-320 and Hartzel Constant Speed propeller will cruise around 180 mph at 8500 ft (MSL) on less than 7 GPH (gallons per hour of fuel).
The S-18, like the T-18 is an all metal 2 place side-by-side high performance aircraft. Control response is exceptional and control forces are well harmonized. The S-18 is a very capable cross-country airplane. It will carry 2 people and 80 lbs. of baggage. Powerplants range from Lycoming O-235 (115hp) to IO-360 (180).
Parts can be provided with matched holes so that parts fit together saving a lot of time in construction. Also parts are scribed to outer mold-lines or trim lines. No jigs are required. The airplane is built using 1/8" solid aluminum rivets, but can be built using 1/8" stainless steel pop rivets (but not recommended).
The S-18 has a folding wing designed by Lu Sunderland which can be swung around parallel to the fuselage making the airplane less than 8 feet wide. So that it can be trailered home or stored in small spaces.
Test Flights were completed on the S-18T Tri-Gear in May of 2003.

The S-18 was available in kit form from Classic Sport Aircraft. Pieces and parts for both the T-18 and the S-18 are available here also.

Engine: Lycoming O-360
Propeller: constant speed
Wingspan 20' 10"     
Length 18' 6"  
Wing area: 86 sq.ft   
Gross Weight 1600 lbs.   
Empty Weight 1000 lbs.     
Useful Load 600 lbs.     
Fuel - Standard Tank 29 gallons     
Fuel - Wing Tank 24 gallons     
Rate of Climb 1500 fpm     
Luggage Capacity 80 lbs.     
Range (standard) 540 SM               
Range (with optional wing tanks) 900 SM     
Cruise - 75% power 180 mph     
Top Speed 200 mph     
Stall: 63 mph
Cockpit width; 40 in
Seating 2 side by side   
Engine options: Lycoming 290, 320, or 360

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