Sinclair and Rush have the three-metre extrusions delivered first thing this morning as it turns out Santa had dropped the previous down the wrong chimney. To optimise the use of these sections I've run with the 36" frame and 12" centre-body converted into metric measures, and you'll find the optimum procedure is to cut each length in half and then divide the remaining 1500mm into lengths of 580mm and 920mm apiece.
Thus two of the three-metre lengths will produce the entire frame, as seen here. One advantage of a switch to plastic, aside from the cost and weight savings, is that these extrusions come in white, which requires only a top-coat to render in Post Office red, or black which is suitable for drones 'as is'. In each event therefore we move closer to a consumer product.
The tube-connectors are a tight fit, nonetheless manageable for anyone with a rubber mallet and a tub of vaseline ~ stop the sniggering NOW please, not big nor clever. The M6 threaded tube-inserts to terminate the cantilevers are a push-fit but are unlikely to need reinforcing with pop-rivets. in fact there are nylon M8 inserts too, so that everything seen here could be 100% plastic. (Ed. If you think it's a good idea, ask your local turtle.)
Using a Mark 1 eyeball and averaging four measures, a 6mm drill-hole at 607mm from the end of each perimeter section (excluding connectors) should work. Meanwhile for the cantilevers, 310mm from the outboard ends (excluding inserts) works equally well. Plastic flexes even more than alloy, and therefore corrects any errors in measurement at the prototyping stage, where we are working to nearest millimetres rather than microns.
