Jodel Project | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | Q&A

The story of wood verses timber
How February 2004 became wood month

Wood has no fatigue life, although metal attaching parts have fatigue lives. Wood is a non-strategic renewable resource. It’s the wood I reject that adds integrity of my Jodel.

During and following World War 2 the Australian aircraft industry was producing British Beaufort and Beaufighter aircraft at the Government Aircraft Factory and Mosquito aircraft at de Havilland’s. They were continually beset by material shortages. Aluminium alloys were in short supply and timber was investigated as an alternative for some structural components. The CSIRO Division of Aeronautics and of Forest Products found that Victorian mountain-ash and Queensland hoop-pine were acceptable for primary structures, whilst coachwood was a suitable substitute for imported birch plywood. A number of native Australian timbers as spruce substitutes were identified and details published as emergency wartime specifications (e)2D-811 for hoop pine, bunya pine, Queensland maple, bollywood, silver quandong and silver silkwood. (The Australian Standard for Aircraft Materials (1944))

The only timbers on Frank Rogers plan for the Jodel D150 (dated October 1976) are Sitkas spruce and Ash but these plans were drawn up prior to the emergence of “EXPERIMENTAL” in September 1998. Plywood specified is both Gaboon (Okoume) and Birch. Plywood these present no problem as both are available from Mister Ply and Wood at sensible prices. On the other hand although it is still possible to source Sitka Spruce it’s imported, expensive and excellent pieces of timber are not readily available. It’s likely that the very best Sitka spruce comes from old growth forests in Canada.

For my aircraft I have decided to use Australian hoop pine both timber and ply and Victorian mountain ash. This is my choice and all that remains is for me to select timber and ply of aircraft quality.

About hoop pine (Araucaria cunninghamii)
A large tree can attain 50 metres in height, hoop pine occurs naturally in drier rain forests from the Hastings River in NSW to Far North Queensland and in Papua New Guinea. It is grown in plantations, predominantly in South Queensland and this is where I sourced my timber.
Grain: Very fine and even textured. Growth rings usually detectable but indistinct.
Density: 575 Kg/cubic metre at 12 % moisture content. This compares with Sitka spruce which is reported to be 449 Kg per cubic metre. The average Jodel will contain 5 to 6 cubic feet of timber. Using hoop pine in the place of Sitka spruce will add about 12Kg in weight. It is generally considered that hoop pine is 10% stronger than Sitka spruce.

These are my requirements when selecting hoop pine:
? Plantation grown timber, kiln dried to 12% moisture content.
? Perfect grain direction (not less than 6 growth rings per inch)
? Absence of knots, grain waviness and excessive grain slope (not more slope than 1:12)
? Quarter cut.

References for selecting hoop pine for aircraft construction:
Commonwealth of Australia Department of Aviation Air Navigation Orders Part 108 Section 108.29of 21 May 1982.
An introduction to Timber Aircraft Building SAAA National Convention 2003

Feb 2004 visit from Bob Furness

Frank Rogers

I called the SAAA

Peter Bennett

Randell Krebbs (Marine engineer)

John Mills Director State Forrests

Thomas Philippa (ex teacher)

Arthur at Rosshaven Marine
Townesville

Bob Faddy

Timber Town Doors

Other contacts
Rudi Pleschutschnig

Alan Bradtke

Terry Ryan

Bob Furness

Customline Joinery Wauchope

Campbell and Jones Taree

Barry Graham Timber Coffs Harbour

Spoke to Nathan they can supply Clears #1 with knots? Furniture grade?