ALLEN MILLYARD
In the penultimate RC374 article the fairing is built.
They say variety is the spice of life, and it certainly is for me regarding my motorcycles, as I like all styles and sizes of bikes. While at Stafford show with my recently completed Honda RC374, back in October, I found myself drawn to the Velocette parts stand nearby and began thinking about my relatively standard 1950 Velocette 350 Mac in my shed back at home. My RC374 and Velocette Mac are two completely different bikes that are light years apart in design and technical complexity. Anyway this got me thinking, “Why have I got a standard Velocette Mac? Maybe I should make it into a 50º V twin?” I spent a bit of time talking to Patrick on the Velocette parts stand and noticed that he had a complete top-end for a Mac for sale. I bought it on a whim and I have since been totally absorbed in converting my Velocette 350 Mac into a 700cc 50º V-twin, maybe I will talk about that in a later edition if it proves to be of interest to CMM readers. Back to my RC374 and the next job, the fairing: Honda only made two 297cc RC174 sixes and they both were fitted with glass fibre fairings but I like the look and feel of the hand beaten aluminium fairings that were fitted to earlier Honda racers. My RC374 was not striving to be an exact replica so I decided to make the fairing from aluminium. For me aluminium is a lot nicer material to work with, no smelly resin and no itchy strands of glass to deal with, also it’s easier for me to fix if I get a dent. I bought a sheet of 1.6mm 1050 grade half hard aluminium, which is easy to cut with tin snips. I had been looking at the photos in my book and decided that the best way to
make the fairing was in three bits and then weld them together. The first thing I did was cut out and make the two lower side-panels, these were relatively easy parts to make due to their shape; they are predominately flat with simple curves and a rolled edge. I started by propping my photo book up behind the chassis so I could see the outline profile of the fairing then by eye I marked out the shape onto the aluminium sheet and cut it out using my tin snips. I always cut a bit big to allow me to adjust the shape and size as I go along. I held the cut out flat sheet against the side of the chassis and could see the shape it needed to be. I started by using my wooded bossing hammer and dished wood former to create the shape I was looking for, gently forming the metal to the desired shape. When the shape was basically right I finished and smoothed out the surface using a steel panel beating hammer and steel dolly. I wasn’t after a glass smooth surface but more of a hand finished surface with patina like on the period photos I’ve seen online. The rolled edge was quite easy to do using a pair of pliers and a hammer. First I marked a line around the edge of the panel about 8mm in from the edge then I folded the edge along this line a bit at a time using the pliers until the whole edge was bent up about 90º. Then using my steel hammer I tapped the edge over until it was tightly folded. I then used a fine file to clean up the edge followed by some fine emery paper to finish off. Then I repeated the process on the other lower fairing panel. The next job was to mark out and drill the mounting holes so that I could fit the lower panels to the frame before making the front panel. I had decided earlier on that because I had retained the starter motor assembly I would make a cut out in the fairing to allow the engine to poke through each side to reduce the apparent width of the fairing. After a bit of fettling both lower panels fitted nicely and I was then ready to make the front panel. This was by far the hardest bit to make being a full compound curve, almost a half hemisphere, so I started by cutting out a piece of aluminium sheet and hammering it with my bossing hammer and wooden block. This took a fair amount of time: you just have to keep hitting away until the shape forms in front of you. At first it’s a just lot of big dents and ripples but gradually over time it starts to take shape and, as I said before, always cut big so you can trim after. I won’t say it was easy because it wasn’t, it was especially difficult to make because the front panel needs to be symmetrical, line up with both side panels and the Perspex screen. The Perspex screen will not tolerate any stress from the aluminium fairing and must fit perfectly with no gaps or it will crack when the screws are tightened. It took me several days to finally get the fit and look right.
The next job was to trim and weld the three parts together; to do this I first mounted both the side-panels and aligned them so they were even each side, then I offered up the front panel, marked the three mounting holes and carefully drilled them. Then I secured the front panel to the fairing frame with the sides overlapping the side-panels. Next I scribed a line on each side-panel and trimmed to size until the front panel dropped into place ready for welding. I tack welded on the bike to ensure accuracy then removed the fairing to complete the welds and file them flush. After a bit of final adjustment the fairing fitted and looked good. I bought a half bubble racing screen from Skidmarx Ltd and offered it up to my fairing, marked around it with a Sharpie pen and carefully cut the screen with a Dremel saw. Then I drilled the holes to secure it to the fairing. The trick when drilling small holes in thin Perspex screens is to use a blunt drill because you don’t want it to grab as it breaks through as this could crack the screen. Take it slowly and don’t push too hard and always rest the Perspex on a soft-faced surface to support the back when drilling. When all the holes were drilled I made a set of M5 slot head screws from titanium bar and mounted the screen. The last part of the fairing to make was the belly pan; this was a simple part to make being a gentle curve with three holes each side to secure it in place. The RC374 was really taking shape now and was almost ready to be stripped down for painting. cmm