About T18.net...
This site is dedicated to anyone with an interest in Thorp T-18 and/or Sunderland S-18 experimental aircraft.
T18.net is not associated with any company manufacturing parts/kits for either the T-18 or S-18, and mention of companies and/or products are not endorsements....
About the T-18...
The T-18 design was originally developed with the Lycoming 0-290G (ground auxiliary power unit) in mind, by John Thorp. Which was easily converted to a Lycoming 0-290D engine producing 125 HP.
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
T-18 is a very capable cross-country airplane. It will carry 2 people, 80 lbs. of
baggage, and depending on engine and prop, can cruise around 180 mph. Powerplants
range from Lycoming O-235 (115hp) to IO-360 (180).
The T-18 was designed to be built from twelve 4' x 12' sheets of aluminum ranging in thickness from 0.016 to 0.040. Ribs and fuselage
frames were designed to be hand formed with a mallet over plywood form blocks. Simple aluminum angle extrusions are used for stringers and longerons. The main wing spar caps are made from 1/4 "U" channel on top and angle on bottom with flat sheet for spar webs.
John Thorp designed the aircraft to be small, yet strong with excellent take-off and climb performance. The landing gear is a simple "A" frame of heavy wall 4130 steel tubing, heat treated to 180,000 lbs./sq. in. and bolted to the firewall with (3) 3/8" bolts. The engine mount is also attached to the "A" frame allowing landing stresses not to be transmitted directly to the fuselage. This landing gear system has proven to be rugged and durable. The T-18 incorporates the "flying tail" which John Thorp held the patent for. This design also incorporates a sliding bubble canopy, like a fighter style.
The
T-18 is a very historic aircraft. It was one of the first all metal
homebuilts. It was the first homebuilt to use the stabilator or all-flying-tail.
The stabilator was designed by John Thorp and was later used by Piper on their
line of Cherokee aircraft. Today you can see the extensive use of this design on
military aircraft. The T-18 was the first homebuilt aircraft to fly around
the world. It was also the first homebuilt airplane to fly to both the
geographic and magnetic north poles. The legendary Don Taylor completed all
of these feats in the early 1970's. His famous T-18 is now on display in the
EAA museum in Oshkosh, Wisconsin.
T-18 plans are available again through
Eklund Engineering. They are also developing a kit version, using laser cut
parts and of course John Thorp's matched hole tooling concept. The laser cut
parts are beautiful and it promises to be a wonderful kit. For more information
contact Eklund Engineering at: thorpt18@jps.net
or by phone at: (209)727-0318
No other homebuilt has done all the things that have been done by this airplane. It is no doubt
one of the best designed aircraft in the world.
T-18
Designations / Models
T-18
The original design by John Thorp in about 1963
T-18C
The original T-18 fuselage design, but incorporating Lu Sunderlands new Convertible
or folding
wing. Plans were available through John Thorp. The folding wing was a supplement
to the original T-18 drawings. The plans were taken off the market in 1984 when
John Thorp retired.
T-18W
Not many of these exist, but is the wide body version of the fuselage as
designed by Lu Sunderland, using the standard T-18 wing platform. Plans were
available through John Thorp. The wide body modification was a supplement to the
T-18 drawings. The plans were taken off the market in 1984 when John Thorp
Retired.
T-18CW
This is the predecessor to the S-18. It is the wide body version of the
fuselage, and also the Convertible or folding wing as designed by Lu Sunderland. Drawings were
available from John Thorp and they contained supplements for the fuselage and
wing modifications. The plans were taken off the market in 1984 when John Thorp
retired.
T-18L
This is my own designation for this model and I hope it will be accepted. This model uses both the standard fuselage and the standard wing plan form, but
incorporates the LDS airfoil designed by Lu Sunderland and used on the S-18.
There are no actual drawings for the "L" version, as builders have
taken it upon themselves to make the airfoil change.
S-18
This is the redesigned version of the T-18 by Lu Sunderland. A complete new set
of drawings were done and offered in 1985. It is basically the T-18CW.
About The S-18...
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.
The S-18 is available in kit form from Classic Sport Aircraft. Pieces and parts
for both the T-18 and the S-18 are available here also. For more information
contact them at:
s18thorp@lightspeed.net or by phone at: (559)539-2755
