Glaring error rectified
Sunday, 30th April, 2017
I made brief mention in my last blog of the glaring omission of an access door in the newly installed port side upper wing fillet of my model. This evoked for me an earlier and yet more serious error when, while skinning the fuselage, I left off the much larger door to the battery compartment in the starboard side.
It is a drawback of the litho plate cladding technique that it is almost impossible to remove the delicate aluminium skin once it is fixed in place with contact adhesive. Yes, it will come off with brute force, but not without taking a lot of the balsa substrate with it and doing irreparable damage to adjacent panels. If a repair is to to be effected, it has to be done in situ.
I began by cutting a template for the access door in a scrap of litho plate. The eagle eyed will note that I simplified its shape slightly so as to increase the chances of success. The template is then taped securely into position on the model.
Now for the tricky stage, which requires a very sharp and fine-pointed scriber. I used a stout sewing machine needle chucked in a pin vice.
The process, which cannot be rushed, particularly during the opening stages, involves repeated light strokes of the scriber using the fixed template as a guide. At first the strokes must be feather light for it is very easy to slip, with almost certain disfigurement to the metal panel. But slowly, as a groove is formed the pressure can be increased. I can help to add a tiny drop of machinist’s cutting oil to smooth the process and prevent judder.
Eventually, after half an hour’s work in this case, the needle point starts to break through the 11 thou thick alloy. Then it is just a matter of persevering until a clean, regular and all-round cut has been effected.
With the template removed the slight ridges created along the cut line can be removed with fine abrasive paper and the job is done and ready for the routine rivet detail.
I was lucky to get away with the same sin twice in a row. Yes the gap around the small door is probably slightly overdone – yet a small price to pay in the face of omitting it altogether!