Here is a front projection of the round K former (carries perspex bubble), the outer profiles of formers J, H, G, F, E to complete the nose section. The lines across the formers join the slot locations for the stringers. In addition, lines join the locations of the top and bottom of the slots for the nose longeron. The round K former profile is composed of 3 circles: the outer profile curve, the inner profile curve and a circle that lies between them. That circle gives the location of the stringer brackets that attach the stringers to former K which are inset from the outer profile of K. All points in the drawing are given in XY coordinates from the centre line and datum.
All the Avro drawings are headed by the warning “WORK TO DIMENSIONS”. Until I was given some very good advice on this forum, I did not understand the significance of the warning. Basically, the drawn curves and their position are unreliable. The only trustworthy method is to use the dimensions given from the aircraft vertical centre line and the horizontal datum line; to use the numbers exclusively.
I have done this. My drawing unit is a millimetre with fractions to 2 decimal places; i.e. to 1/100 of a millimetre. With rounding errors, this means that I am working to approximately 1/10 of a millimetre full scale. My guess is that this drawing is accurate overall to within +/- 5 millimetres full scale. I should do a proper error analysis and, when I do, hope there are no surprises.
All formers except the last E and all the stringers, their locations and their fastenings to the formers are all now fully determined. Two items here remain to be determined: the construction of the front part of former E and the manner of attachment of the stringers to this former. Further than that, all the intercostals which form the floor of the section, the windows and the escape hatch need to be determined.
One thing that has struck me is the complexity of the nose longeron curve, or at least of the top and bottom of the longeron slots. I suspect this was not part of the original design. The turret deck and turret are canted up at the front by around 3 degrees. I suspect the complexity of the longeron is to allow a change in the angle of the turret deck etc. That is, this angle of 3 degrees was not in the original design. I know there were problems of disturbances in yaw of the aircraft when the turret was turned to the beam. I wonder if this upwards angle of 3 degrees was implemented to reduce the yaw disturbance as the turret was rotated.
Though a neophyte I am very impressed with the design of the structure. Particularly as there appear not to have been any antecedents. The fuselage of the Lancaster subject to small alterations was that of the Manchester. But the design of the Manchester seems to have come out of the blue. As an example, the Hawker Hurricane is very clearly derived from the biplane Hawker Fury etc. For most Hawker aircraft there is a chain of design antecedents. Many of the design elements of a Hawker aircraft have been tried and tested with one or more previous aircraft designs. For the Manchester, nothing! How I wish I could find someone to ask. Not in this life sadly!
Mike
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March 20, 2011 at 6:25 pm