Famous Case - Spruce Goose

Famous Case #1: gluing together the world’s largest airplane (in 1947)


spruce gooseThe Spruce Goose was an aircraft built by the aircraft designer Howard Hughes, a very successful engineer, aircraft pilot and businessman, under a 1942 contract with the US War Department. A need had been identified at that time to transport war materiel and personnel from the United States to Great Britain when supply ships were running the risk of being sunk by German submarines.

Because of the shortage of aluminium, Hughes decided to build the aircraft mainly from wood. Wood composites were already used for their lightness and strength in smaller aircrafts and boats. Despite the name, the chosen wood was birch.

The aircraft was huge for the time, with a length of 66.65m, a wingspan of 97.54m and a height of 24.18m. It weighed 114 tons empty and 180 tons fully loaded (60 tons of cargo). It was propelled by eight radial engines. It was designed as a “flying boat” taking off and landing on water, reaching a speed of 408 km/h and a range of 4,800 km. By comparison, the first Boeing 747-100B “Jumbo Jet” measured 70.6m from tip to tail and had a wingspan of 59.6m. It weighed 162 tons empty and 333 tons loaded, thanks to its four more powerful jet engines.

The Hughes H-4 Hercules prototype aircraft was completed after the war ended so it was never made operational. Hughes personally flew it for the first time in November 1947 over a short distance at a speed of 217 km/h and an altitude of 21m off the Californian coast water. It was then retired and is now kept on display at the Evergreen Aviation Museum in McMinnville, Oregon, close to Portland.

wood compositeThe glue holding the wood composite together was a thermosetting urea and/or phenol-based resin capable of resisting moisture, heat, cold, bacteria and fungi and providing  high structural stability. It was supplied by the Plaskon division of the Libbey-Owens-Ford Glass Company in Ohio.

The composite was made using the Duramold process. Birch piles are impregnated with resin and laminated together in a mould under heat and pressure. Weight-for-weight, the composite is stronger than aluminium.

Plaskon resin was also used to make assault boats during the Second World War.

Today 70% of urea-formaldehyde resins are used by forest industry products: particleboards, fiber boards, hardwood plywood and laminating adhesive (source: Wikipedia).


spruce goose


Famous Case - HMS Victory

Famous Case #2: Caulking HMS Victory

Portsmouth HMS Victory 200Modern sealants are convenient to use but are no match for traditional techniques when it comes to historical ships.

HMS Victory, Nelson's flag ship during the battle of Trafalgar on 21 October 1805, is on permanent display in Portsmouth, UK.
Needless to say, not only it had to be extensively repaired after the battle and its successive uses before retirement, but the 251-year old ship must undergo regular repairs to withstand rain, dry rot, death watch beetle and visitor's feet.
For the last fifteen years, modern marine caulking sealants were used on the deck, but it was subsequently found that they could not withstand the natural movement of wood, and soon water leaks appeared.

The gaps between the deck planks that must be made water tight are about 6mm wide.

Portsmouth HMS Victory Here Nelson Fell 200In a recent renovation campaign, the modern sealant was removed manually and replaced by oakum and pitch. Oakum is a loose hemp or jute fiber.Previously, oakum used to be made in workhouses, prisons, and by children from old ropes and cordages. Nowadays, a machine is used for that purpose. The caulking is done by pressing the oakum in the gaps and pouring hot tar pitch derived from pine sap or from petroleum residues. A tool called a caulking iron is used to manually pack the caulk. The operation can be viewed at https://vimeo.com/47098266.

Pine tar pitch is made by carbonizing pine wood or bark in anoxic conditions, allowing the low-boiling components to volatilize. Process is similar to Birch Tar Glue.


Portsmouth HMS Victory Poop 72dpi



Famous case - Art & Epoxy Resins

Famous case # 3: Jean Dubuffet sculpture using epoxy resins


art resine epoxy crop200Epoxy adhesives were developed in the 1940s (see the Science section).
Initial applications were high-performance gluing for military vehicles, including aircraft.
At the end of the sixties, art also seized epoxy resins *.
Some artists like Jean Dubuffet have made it one of their main working material to make sculptures of various dimensions, some of monumental size such as those of the Enamel Garden in the Netherlands.

(* Although the use has been to call them epoxy, the correct term is polyepoxide resin)