Designed to conform with the famous mckenzie river drift boat, specmar aluminum drift boats are constructed of marine grade aluminum for all welded construction. boats are designed for assembly. Designs available in aluminum…. aluminum is also a superb material for boatbuilding by the person qualified in aluminum welding. aluminum boats using welded marine alloy construction are strong. Stephen pollard aluminum designs. glen-l is proud to offer designs by stephen pollard for welded aluminum construction complete with cad files. stephen pollard is the author of one of our most.