Why would you weld in the floor??? You'll change the design stress of the boat and introduce new fatigue points. Aluminium dust can explode in correct circumstances. Refer extract:
"During fabricating operations, aluminum fines may be generated by such activities as grinding, sawing, cutting, sanding or scratch brushing and at least some of them will be fine enough to be potentially explosible. The term “dust” or “powder” is frequently used to describe such particles. It is difficult to be specific about dimensions, but if all the particles are larger than 500 microns, an explosion will probably not be sustained. It is more likely, however, that a mixture of coarser and finer material will be generated, and if the material is 420 microns (40 mesh) or finer, then it has the potential for explosion.
Finer particles burn readily when their ignition point is reached, and tend to ignite the coarser particles as well. In the case of aluminum, an explosion can result if ignition occurs while the particles are suspended in air as a dust cloud, since the burning extends from one particle to another with extreme speed.
Examples of potential sources of ignition are open flames, welding equipment and cutting torches, matches and cigarettes, faulty electrical equipment and static electrical discharges. Such conditions must be avoided in areas where dust producing operations are carried out." [emoji848]
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