Re: Restore and Rebuild 74 Mariner 18?
Re: Restore and Rebuild 74 Mariner 18?
i think the three reasons were cost, cost, and cost. Oh, and labor cost. skilled fabrication and TIG work like what ct did on his transom is really expensive compared to hiring a guy who can run a saw. given the quantities they were buying plywood in, wood transom prolly cost em <$10/boat and was plenty strong. ever heard of the WWII Mosquito airplane*? plywood. Marcos automobiles? plywood.
there is a possibility that the wood will help dampen motor resonances tho. ain't much that does uncontrolled resonance better than thin metal. this is part of the reason i'm coating inside of my hull with durabak, and i even considered gluing in some spare ashalt roofing (poor man's Dynamat)
*
http://en.wikipedia.org/wiki/Mosquito_bomber
The oval-section fuselage was a frameless monocoque shell built in two halves being formed to shape by band clamps over a mahogany or concrete mould, each holding one half of the fuselage, split vertically. The shell halves were made of sheets of Ecuadorean balsawood sandwiched between sheets of Canadian birch, but in areas needing extra strength— such as along cut-outs— stronger woods replaced the balsa filler; the overall thickness of the birch and balsa sandwich skin was only 7/16 in (11.11mm). This sandwich skin was so stiff no internal reinforcement was necessery from the wing's rear spar to the tail bearing bulkhead.[60] The join was along the vertical centre line.[61] This split construction greatly aided the assembly of the internal equipment as it allowed the technicians easy access to the fuselage interior.[62] While the glue in the plywood skin dried, carpenters cut a sawtooth joint into the edges of the fuselage shells, while other workers installed the controls and cabling on the inside wall. When the glue completely dried, the two halves were glued and screwed together. The fuselage was strengthened internally by seven bulkheads made up of two plywood skins parted by spruce blocks, which formed the basis on each half for the outer shell.[63] Each bulkhead was a repeat of the spruce design for the fuselage halves; a balsa sheet sandwich between two plywood sheets/skins. Bulkhead number seven carried the fittings and loads for the tailplane and rudder The type of glue originally used was Casein resin, which was later replaced by "Aerolite", a synthetic urea-formaldehyde, which was more durable.[64][nb 8] Many other types of screws and flanges (made of various woods)also held the structure together.[61]
The fuselage construction joints were made from balsa wood and plywood strips with the spruce multi-ply being connected by a balsa V joint, along with the interior frame. The spruce would be reinforced by plywood strips at the point where the two halves joined to form the V-joint. Located on top of the joint the plywood formed the outer skin.[62] During the joining of the two halves ("boxing up"), two laminated wooden clamps would be used in the after portion of the fuselage to act as support.[62][67] A covering of doped Madapolam (a fine plain woven cotton) fabric was stretched tightly over the shell and a coat of silver dope was applied, after which the exterior camouflage was applied.[68] The fuselage had a large ventral section cut-out, which was braced during construction, to allow it to be lowered onto the wing centre-section. Once the wing was secured the lower panels were replaced, and the bomb bay or armament doors fitted.[69]
A closeup of the nose of a B Mk IV showing the clear nose and the bombsight: this view also shows the engine nacelles for the single-stage Merlin 23s and the undercarriage.The all-wood wing was built as a one-piece structure and was not divided into separate construction sections. It was made up of two main spars, spruce and plywood compression ribs, stringers, and a plywood covering. The outer plywood skin was covered and doped like the fuselage. The wing was installed into the roots by means of four large attachment points.[61] The engine radiators were fitted in the inner wing, just outboard of the fuselage on either side. These gave less drag.[61] The radiators themselves were split into three sections: an oil cooler section outboard, the middle section forming the coolant radiator and the inboard section serving the cabin heater.[70] The wing contained metal framed and skinned ailerons, but the flaps were made of wood and were hydraulically controlled. The nacelles were mostly wood, although, for strength, the engine mounts were all metal as were the undercarriage parts.[61][71] Engine mounts of welded steel tube were added, along with simple landing gear oleos filled with rubber blocks. Wood was used to carry only in-plane loads, with metal fittings used for all triaxially loaded components such as landing gear, engine mounts, control surface mounting brackets, and the wing-to-fuselage junction.[72] The outer leading wing edge had to be brought 22 inches (56 cm) further forward to accommodate this design.[70] The main tail unit was all wood built. The control surfaces, the rudder and elevator were aluminium framed and fabric covered.[61][71] The total weight of metal castings and forgings used in the aircraft was only 280 lb (130 kg).[73]