Rib stringing and taping
Wednesday, 17th April, 2019
After the disaster in November with the rudder and elevators it was not until March of this year that I psyched myself up for a second attempt. Fortunately, in ripping off the old fabric the underlying ply and balsa framework had sustained negligible damage, although some of the delicate metal fittings had become distorted during removal and these required restoration.
Solartex self-adhesive fabric is relatively easy to apply so long as care is taken to avoid wrinkles. The lightweight material is tacked onto the underlying wood using the tip of a warm iron, and the final drum tautness is achieved at the end of the process by gliding the iron over the stretched surface at maximum heat. The entire covering job took no more than a three to four hours, but the painstaking rib stringing and taping occupied me for well over a week.
Solartex comes with full and clear instructions, so I’ll skip this stage and focus on the stringing. First, however, I want to express my indebtedness to Col Pope for inviting me to ARC at Duxford for a thorough briefing on the rib tape pattern and sequence for the Mk IX rudder and elevators. Col’s notes and the many photographs I was able to take of the real thing, made the work immeasurably easier.
I describe the rib stringing process in detail in my book, ‘Spitfire in my Workshop’, although this time around I made some modifications that simplified the procedure for my second Spitfire model.
It could hardly be more straightforward: I used stout machinists thread with knots tied at approx 8 mm intervals (corresponding to the 1.5-in. pitch specified in full-size practise). Each run of thread is secured at the exact rib position using double sided tape. The sequence is:
– Cut the double-sided into strips of about 1/8-in wide
– Position these accurately on the model, aligning them carefully along the midline of their respective plywood sections
– Remove the protective strip from the double sided tape
– Carefully emplace the knotted thread and tamp it down carefully into the sticky surface. Trim the excess off from either end.
– Position the enclosing crimped rib tape over the top. Some faint pencil lines help here.
– Carefully bed the rib tape down on either side of the knots using fingers and finger nails.
I’m often asked where I get my crimped tapes, and the answer is that I have them commercially laser cut from strips of Tamiya masking tape. It’s expensive, but there is no other way that I know of; and the Tamiya product is thin, strong and beautifully flexible, making it ideal for this kind of work. I created my own ‘art work’ for the scaled-down crimped tapes using a computer graphics package. Clearly, support is needed during the cutting process, and I provide this in the form of A4-size acetate sheets. My 1:5 scale rib tapes are approximately 11 mm wide (corresponding to 2-in. in full size), so I ordered 18mm wide Tamiya tape for the job. At least three reels are required.