All those weird and wonderful postwar homebuilt U.S. one-offs...

here is a Thalman T-4,strange concept.

Not so strange, the T-4 followed the same wooden geodetic construction employed by Harry J. Thalman [1] and William Earl Player when they helped form Plxweve Aircraft. [1] (Construction techniques followed those of Thalman's Oregonian mentor, George Yates - bending strips of cedar around heated former moulds.) While fellow Mormon, Player, designed both parasols and low-winged aircraft, Thalman favoured mid-wings - as on his single-seat T-3/T-3B. In general construction technique, the T-3 and T-4 were similar - the T-3 being fabric-covered, the T-4 having a fibreglass covering.

Attached is a cutaway drawing from Sport Aviation, 22 August 1961, pg.22

Thalman and Player were joined by a third geodetic aircraft builder - John Greenleaf of Portland, OR, to form the Plxweve Aircraft Company in 1940. [2] Greenleaf then arranged financing through Ralph Hemphill of Los Angeles. As a result, the Plxweve Aircraft Co. became a division of another Hemphill-controlled firm - Aero Industries Technical Institute, Incorporated (Aero ITI). Ralph Hemphill became President of the Plexweve division but refused further investment. The money was run through quickly and much legal wrangling ensued.


What followed is confusing. Plxweve's CT-6A monoplane (NX19994) is referred to either the Greenleaf CT-6A or Player CT-6A. Jane's infers that Greenleaf was the company name but I find no other record of such a firm. At some point, the partners went their separate ways. In 1949, Harry formed Thalman Aircraft Inc. at Salt Lake City. In the same year, he designed the Talman T-4 which, AFAIK, flew in 1951. [3] Convinced that serial wooden geodetic construction would be less expensive than by-then conventional metal construction, Thalman spent the next decade trying to get the T-4 into production. At one point, Thalman approached the Cache Chamber of Commerce in Utah for start-up funds of $50,000 (and a suitable workspace) to launch T-4 production - presumably near Logan, UT. The Chamber passed.

By 1957 Thalman Aircraft Corp. had relocated to Mount Pleasant, UT, with plans to establish T-4 production there. In a letter to Flying Magazine (March 1957, pages 6 & 8), Mount Pleasant resident Rex C. Staker [4] writes that the production T-4 was to be offered with 150-, 170-, or 180 hp engines. According to Aerofiles, Thalman Aircraft also took over a concept from Van Nuys-based ATS (Aircraft Technical Services Inc., Floyd E. Snow) in 1959. That ATS design was described as a 4-place mid-winged cabin monoplane ("reportedly 50 percent complete"). If I understand correctly, Thalman Aircraft then began reworking this laminar-flow winged design as a "twin-engine development". Our Harry seems to have been getting a bit distracted.

By 1960, Thalman Aircraft Corp. was doing business as Thalman Industries (sometimes given as Thalman Aircraft Industries). However, the firm was now planning to relocate to Roseburg, OR - 900 miles to the west. Roseburg businessman Lynn Andreas had become president and it was Andreas who was announcing the construction of a new factory on 5 acres of leased land at the Roseburg municipal airport. Early reports said that site ground preparation work had begun and that a "plywood plane" would be built. [4] Harry Thalman is quoted, saying that his aircraft will sell for less than $14,000. [5]

According to local media reports, [6] the production type's structure - under its fiberglass shell - would be an aluminum honeycomb. [7] That jives with an article in Sport Aviation August 1961 - Geodetic Aircraft Structure by Keith D. Powell, EAA. On page 22, Powell writes that Thalman was "now working on another midwing featuring a plastic bonded honeycomb sandwich airframe." Reportedly, circa 1958, Harry began losing interest in geodetic structures Still, the move to aluminum honeycomb seems odd. Lynn Andreas was also president of the Oregon Red Cedar Co. As such, you would think that he would have a stake in retaining Thalman's usual wooden construction. This change may suggest that Harry Thalman had that commonest of inventor's problems - a tendency towards endless tinkering.

Contemporary reports say that Thalman was "working on a fifth model which will include a number of modifications, such as a more powerful motor, sweptback tail assembly, and electrically-operated landing gear and flaps." These all sound like sensible updated for a production variant. But the The News-Review report says that an "all-hydraulic retractable landing gear" was to equip the production type. [8] Perhap more of Harry's tinkering? Needless to say, that Roseburg factory never materialized. I've misplaced the reference but, in the early '60s, some airport was holding the parked Thalman T-4 until storage fees in the order of $800 were paid. Obviously Harry was skint.

By 1963, Harry Thalman was working as a mechanic for Kelsey-Ellis Air Service at Salt Lake City Airport. The T-4 was in storage (and possibly disassembled by then) but Harry was still flying the T-3B. On 15 March 1963, Harry was doing flying cross-country when he flew into a blinding snowstorm. Harry Thalman died instantly when he crashed his T-3B monoplane in a gully outside of Grantsville, UT.


[1] Harry J. Thalman: born 25 March 1911 at Challis, Idaho; died 15 March 1963.

[2] The connection between the three men was probably wooden geodetic construction pioneer, George Yates of Beaverton, OR. Thalman, at least, took instruction from Yates. And Yates' partner, Alland D. Greenwood would also later be involved with the Plxweve Aircraft Company. I'll do more on George Yates later.

[3] Not 1953 or 1957 as is sometimes reported. Another sources claims that the T-3 was the first product of Thalman Aircraft. Not so. The T-3 had first flown back in 1941 (suggesting that Thalman was, at this early date, already drifting away from Player and Greenleaf).

[4] I can find no direct connection between Rex Clay Staker and Thalman Aircraft. Perhaps Mr. Staker (later listed as an insurance agent) was simple a proud citizen of Mount Pleasant?

[5] Statesman Journal, Plane Factory Is Planned At Roseburg, Salem, OR, 31 July 1960, page 2.

[6] The News-Review, Roseburg Aircraft Plant Proposed, Roseburg, OR, 12 April 1960, page 7.

[7] In earlier work, Thalman apparently incorporated some paper honeycomb in construction.

[8] The Eugene Guard, U2 of the Upper Umpqua, Eugene, OR, 26 July 1960, page 22. Apparently, reporter Jerry Uhrhammer was taken with the T-4's comparatively long span and tried to make a bizarre tie-in with the Lockheed U-2 spy plane (then in the news).


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A bit more on Harry Thalman designs.

Thalman T-1

Aerofiles mentions the 1935 Thalman T-1 - describing it as a 2-seat, open-cockpit monoplane. The T-1 (c/n 1, 12793) was powered by a 60 hp Thalman engine ... but I haven't been able to find any other information about the T-1.
Does anyone have more on this elusive type?

There are a number of mentions of Harry Thalman in the Frank Kelsey photograph collection at Archives West. One that especially intrigues is entitled "H. Thalman 'Special'".

Wikipedia has the T-1 listed as "Thalman T-1 a.k.a. Argonaut". This mis-naming is a confusion with the much earlier Thaden T-1 Argonaut transport aircraft. But since this error originate with Wikipedia, it is now endlessly repeated by online sources.

Thalman T-2 (??)

As Aerofiles' creator, the late K.O. Eckland, said: "Logically a T-2 was designed, as well, but no data were found." We can probably assume that Harry did some work on a second design or he would not have passed over the designation number.

Thalman T-3 - 1941 single-seat, single-engined mid-winged monoplane, x 1
-- Experimental a/c* by Harry J. Thalman, Salt Lake City, UT, NX28374
- T-3 : Fuselage & cantilever wings, fabric-covered wooden geodetic const.
- T-3 : 1 x 55 hp Velie M-5 5-cyl. air-cooled radial, span 12.49 m
- T-3 : Fixed 'taildragger' u/c; strut-braced low-set horiz. tailplane
- T-3B: Revised airframe with a T-tail,** spats fitted to main wheels
-- * T-3 often listed as a 'homebuilt' but but production was planned
-- ** Aerofiles says T-4 was conv. to T-tail, confusion with the T-3B?

Attached is a 3-view drawing showing the Thalman T-3B (with an inset view of the T-3 tailplane).

Thalman T-4 - 1951* single-engined, mid-winged, 4-seater monoplane, x 1
-- * Testflying in 1952, other sources give dates of 1953 or even 1957
- T-4 : Fuselage & cantilever wings, GRP-covered wooden geodetic const'n
- T-4 : 1 x 135 hp Lycoming O-290/170 hp Lycoming O-340,* span 12.19 m
-- * HO4 engines were mounted beneath extended, streamlined windscreen
- T-4 : Electric/manually-retr. tricycle u/c, foldable single-spar wing
-- aka Thalman Midwing Monoplane

Thalman T-5 (??)

The refined and tweaked production variant of the T-4 has been described as a "fifth model". Initially, the changes were described as including "a more powerful motor" (meaning the 180 hp Lycoming?) and electric flaps and undercarriage operation. A more stylish, swept tailfin was also going to be adopted. However, shortly afterwards, a complete change in construction was announced. In place of wooden geodetic construction (with some paper honeycomb), the production type was to have a structure primarily made up of advanced bonded aluminum honeycomb.

With such a radical change in structural technique, might this "fifth model" have warranted a change of designation?


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George Yates of Beaverton, OR, and Wooden Geodetic Airframes

When discussing Harry J. Thalman's designs, I acknowledged that his mentor had been wooden geodetic construction pioneer, George Yates of Beaverton, Oregon. Thalman made several trips from Salt Lake City to Beaverton to learn about geodetic construction techniques from from Yates.

In 1932, Yates had produced his geodetic Oregon O (N15508) powered by a 40 hp Salmson 9AD radial. Yates' method of geodetic construction consisted of bending spruce strips over former moulds. The Oregon O was developed into the 1935 twin-engined Greenwood-Yates Bi-Craft (NC15546) with 50 hp engines. Yates and partner Allan D. Greenwood (a pilot and Oregon state aircraft inspector) formed the North Pacific Aircraft Corp. to market the Bi-Craft (note: Aerofiles says Seattle but Pacific Aircraft was actually based in Portland, OR).

Allan Greenwood had been chief flight instructor at the Adcox School of Aviation where he trained military pilots for Chiang kai-shek. In 1934, Greenwood was appointed to the Oregon State Aeronautics Board. There, aircraft inspection and licensing duties brought him into contract with George Yates. [1]

In 1934 Yate's Aircraft had produced the 'Stiper', a one-off, single-engined parasol 2-seater for Beaverton businessman Elmer Stipe. The 'Stiper' was powered by a 125 hp Martin 4-333 inverted 4-cylinder (previously known as the Model D-4 Chevrolair). [3]


If George Yates is remembered at all today, it is for his 1940 Bi-Motor - a geodetic-construction light twin design. (On the first link, below, note Oregon aircraft registration license plant No.20 attached to the cowling.)


In 1945, an updated Oregon O parasol was built. Named the Gilbert Experimental (no clue who/what 'Gilbert' was), N1333N was powered by a 125 hp Martin 4-333 inverted 4-cylinder. This was the type of engine as on the 'Stiper' - it might even have been the same actual engine. I have no other details, but here's an image of the Gilbert Experimental's geodetic fuselage while under construction:

-- View:


[1] With respect to the Thalman story, it should be mentioned that Allan Greenwood would also later be involved with the Plxweve Aircraft Company - having been invited to LA by an unnamed Plxweve engineer. [2] Greenwood arrived in Summer 1940 but, by March of 1941, Plxweve Aircraft Company was effectively bankrupt. Greenwood was amongst those sued by Plxweve's financier and President, Ralph Hemphill. In the end, the courts found no fault with Greenwood - in fact, Hemphill was ordered to pay Greenwood for his efforts.

[2] This may well refer to Plxweve's Chief Engineer Curtis Bates. However, as a wooden geodetic designer from Oregon, Allan Greenwood would also have been well-known to Messrs Thalman, Player, and Greenleaf.

[3] The Chevrolair was not - as is often claimed - a car engine adapted for aviation use. It was a purpose-designed aero-engine by the Chevrolet Brothers Aircraft Company. This engine was designed and Chevrolet Brothers firm started after Arthur and Louis Chevrolet had left the automotive industry. The new company was overtaken by its creditors who sold rights to the engine to the Glenn L. Martin Company.
From Flying 1955-2,

a triplane,designed by Mr. George Frisbie.


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Is there a particular advantage to that MOC now?

Geodetic construction was really only relevant during the 1930s, when they wanted to convert to stressed skin, monocoque construction, But could not afford the weight of true monocoque structures. So they build pseudo-monocoque (geodetic) structures with dozens of holes. Fabric was still the lightest materail for covering airframes. Fabric worked well up to about 300 miles per hour, then they needed rigid skins.

3D printing reduces labour costs for installing all those dozens of stringers.
Mind you, composite manufacturers have been using automatic winders to lay fiberglass or carbon fiber tapes on male molds for decades. Like geodetic, composites use three or more different layers, laid at different angles to carry the various loads. The ability to lay tapes exactly in line with loads allows them to carry loads with the minimum of excess material (e.g. sheet metal).
Thank you, Sir. Learned something useful there. Always quite taken by the method myself.
About Sorrell aircraft and Projects,

we know that,he began to construction homebuilt aircraft from 1950s.
and his series are not completed,can see SNS 2,4,6,7,8,9 & 10,no sign
for SNS 1,3 & 5 ?.


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Yes. Engines that I've seen associated with the Guppy are:

- 1 x 18 hp OMC Cushman 200 Truckster HO2
-- Aircraft conv. of Outboard Marine Corp. boat engine
- 1 x 18 hp Onan HO2 (later Cummins Onan) generator conv.
- 1 x 25 hp Citroën GC HO4 (aero-engine conversion)
- 1 x 32-35 hp Rotax 377 HO2 2-stroke aircraft engine
- 1 x 36 hp Volkswagen HO4 (aero-engine conversion)

I've also seen the Rotax 447 mentioned ... although 42 hp seems excessive for the SNS-2. Perhaps this is confusion between the Rotax 337 and the SNS-8's Rotax 447 option?

Oh, and BTW, SNS-3 is the designation for the Sorrell Biggy Rat - a 1969 Lycoming 0-290 powered single-seat biplane. The Biggy Rat (N3717) looked like a more streamlined Guppy with very thin wings.


Makes you wonder if the Sorrell Golden Condor and Sorrell Intruder ever had designations ;)
From Air Pictorial 1955,

what was this Sits-Besler aircraft ?.


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Good Day All -

I picked up this negative on EPay last week - any ideas what it is? Forward fuselage, or at least the engine cowling, reminds me of the Curtiss Robin.

Enjoy the Day! Mark


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Delt-Air 250 plans available on Ebay. One of a handful of true delta wing homebuilts. The original plane was destroyed with the loss of its designer. Someone bought the plans to rebuild the aircraft, but nothing was ever done with the plans or the aircraft.


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Delt-Air 250 plans available on Ebay. One of a handful of true delta wing homebuilts. The original plane was destroyed with the loss of its designer. Someone bought the plans to rebuild the aircraft, but nothing was ever done with the plans or the aircraft.
Those drawings came from the article in EAA Sport Aviation about the aircraft. Let me see where I put the scan I made and will post that.

Enjoy the Day! Mark


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From Aviation magazine 1986,

the Eaves Catfish.


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Might be an entirely different aircraft altogether. The one from avweek is 1951 vs 1954, and 150hp engines vs 85 is a big difference. Maybe the builder found their first twin underpowered and made a second?

Russell E. Northrop 1-A Special - likely a goodyear class racer
russel northrop 1-a special av week 52-6-30.png
Russell E. Northrop 1-A Special - likely a goodyear class racer
Indeed Sienar, a Goodyear racer built in 1952.

"Goodyear Formula One Air Racing 1947-1967" Volume 1 by Robert S. Hirsch, Wing Canyon Publishing 1998
"The Experimenter" March 1955


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Those drawings came from the article in EAA Sport Aviation about the aircraft. Let me see where I put the scan I made and will post that.

Enjoy the Day! Mark
Good Day All -

Attached is the drawing and the cover of the Sport Aviation that covered the Delt-Air 250 prior to the fatal first flight attempt.


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