Aircraft Research BT-11 Basic Trainer Project ?

[hesham]

Hi,

does anyone have a drawing to this beast,all Info about t here;

https://en.wikipedia.org/wiki/Aircraft_Research_BT-11

The Aircraft Research XBT-11 was to have been a basic trainer constructed by the Aircraft Research Corporation (formerly the Vidal Research Corporation) of Bendix, New Jersey, by molding "Weldwood", a "plastic" plywood composite material made of heat and pressure-processed phenol phenol-formaldehyde resins and wood similar to the Duramold process. The Duramold and Haskelite processes were first developed in 1937, followed by Eugene L. Vidal's Weldwood in 1938.[1] A production contract, proposed in 1940, was cancelled before any were built.

General characteristics

Crew: 2
Length: 27 ft 6 in (8.38 m)
Wingspan: 42 ft (13 m)
Gross weight: 4,431 lb (2,010 kg)
Powerplant: 1 × Pratt & Whitney R-985-25 radial engine, 450 hp (340 kW)
Performance

Maximum speed: 169 mph (272 km/h; 147 kn)

 

[Apophenia]

No drawing, I'm afraid. It's surprising that there don't seem to be images online of either the XBT-11 mockup or 1/15 wind tunnel model.

Does anyone have a copy of USAAF Technical Report 4615? There's bound to be images in that of the wind tunnel model if nothing else.

I've seen reference to the XBT-11 springing from the Summit HM-5 light aircraft prototype (NX25332). I assume they meant that the Summit's construction techniques were considered successful, not that the XBT-11 was in any way derived from the much smaller HM-5.

 

[hesham]

Thank you for the Info my dear Apophenia.

 

[riggerrob]

Americans made a bunch of Duramold prototypes during WW2.

Timm built 262 Duramold N2T trainers for the US Navy.

Meanwhile Canada built 1,069 Anson Mark V trainers with Duramold fuselages. Internal frames are less than 2” in thickness and width! There is an Anson Mark V on display at the aviation museum in Rockfliffe (a suburb of Ottawa).
DeHavilland developer a similar process to build Mosquitos. Even with the jet Vampire had a molded plywood cockpit!
The largest Duramold airplane was the Hughes Spruce Goose.

 

[riggerrob]

Summit HM-5 was much smaller, in the same range as the Globe Swift which it resembled.

From aero files.com
Registration NX25332
1939
2 place (side-by-side) cabin, low-wing monoplane with retractable gear
75 hp. Continental A-75 engine
Span 28’
Length 22’
Top speed 142
Stall speed 38
Designed by Howell Miller

 

[Apophenia]

Summit HM-5 was much smaller, in the same range as the Globe Swift which it resembled.

Indeed. The HM-5 can only have provided construction-technique inspiration for the XBT-11.

A few notes of moulded wood construction. There are more differences between the various processes than generally realized. Most of the US processes used phenol formaldehyde (PF) resins but their techniques varied.

Fairchild's Duramold process was developed by Virginius E Clark (of Clark Y airfoil fame) and used in Fairchild's own AT-21 Gunner trainer. Howard Hughes bought partial rights to the Duramold process - which was further developed at Hughes after they hired VE Clark. It was in Hughes' modified form that Duramold was used on the H-4 Hercules.

The Vidal-Weldwood Process used for the XBT-11 was similar to Fairchild's Duramold. Both used heat-activated synthetic PF resins to bond birch veneers while pressure moulds shaped the plywood. The difference was that Weldwood moulded fuselage stiffeners and skin in one step. The Canadian Anson Mk.V mentioned (and one-off Mk.VI) used this Vidal-Weldwood Process.

Timm used its own process, not Duramold - hence N2T-1 marketing referring to the 'Timm Aeromold Trainer'. With its Aeromold process, Timm stamped out parts shape blanks of flat spruce veneers (using dies and heated presses). The pieces were then assembled, impregrated with cold-setting PF resin, and vaccuum-bag pressure-formed.

The big deal about Timm's Aeromold process was that it required lower temperatures. The vaccuum moulding process was done at 100°F. Once the parts were set, they were removed from the autoclave, assembled into components and then further baked at 180°F to fully harden. Reputedly, Timm's Aeromold process resulted in the smoothest skin among moulded-plywood components. (Weirdly, Timm explored a possible wooden pursuit development of the H-1 racer. I assume that construction would have been in Timm's Aeromold process rather than Hughes' modified Duramold ;D )

BTW. the de Havilland process was quite different. Pioneered with the DH.91 Albatross airliner's monocoque fuselage, it was a plywood-balsa-plywood sandwich (whereas US techniques were birch - or sometimes spruce - plywoods). Moulding pressure was applied by a series of flexible steel bands wrapped over the male mould to created the shape.