Chassis
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It says in the build manual that paneling the chassis will take some time if attempted correctly without really defining what correctly is. Well from my limited experience I would suggest that you make a template for the tunnel panels and the rear bulkhead and then see how they fit before transferring the dimensions (with adjustments) to metal. I made notes on the templates about how well they fitted along the various edges. My first attempt at the passenger tunnel panel based upon measuring the chassis ended up with something that was completely the wrong shape. Next I made a template and this still didn't fit perfectly but I was able to use this as a basis for the second attempt. Unfortunately I made the most basic error in not turning the panel upside down before cutting out and as such ended up with a near perfect panel with all the marks and scratches on the outside and the protective plastic film on the inside. Oh how I laughed.
The third attempt at the passenger side tunnel panel was attempted on some spare 18 gauge that Jeremy had included (I wonder if he foresaw this). Based on the previous experience this was now a very good fit. I had allowed sufficient clearance for the weld beads and returns to allow for the thickness of the material and the bend radius. The rivet holes were measured and centre-punched and the panel put to one side for when the chassis is back from the exhaust fabricators.
With hindsight I would say that paneling a surface that is not flat, with various cut outs is far from simple. The tunnel sides are perhaps one of the more difficult panels and being the first ones to do are quite a wake-up call. The difficulty is that you have to cut out fairly accurate holes to clear the handbrake mechanism and various chassis members before you can lay the panel on to check the fit. A set of templates would be really useful, but from the small variance I have seen I suspect that no two chassis are identical and making a template is good practice for the real thing.
The rear bulkhead panel was much easier and the template was only 3-4mm out along one side, despite measuring many times. The slight taper in this panel top-to-bottom means that if it is too narrow then it will sit too low and vice-versa. Remember to allow 2-3 mm for the thickness of the material and the bend radius when bending the returns. The aluminium panel produced from this was a good fit and again it is worth taking time over marking out where holes need to be cut for the rear wishbone bolts and handbrake cable. I marked out the holes for the 12mm suspension bolts with a 19mm socket, drilled lots of holes and filed the final shape with a half-round file.
Driver and passenger floor panels were very easy because they are flat and can simply be marked out by clamping the material to the chassis floor and drawing round the chassis. The panels supplied were already tapered and so it was easy to offer them to the chassis to fit the outer rail and tunnel rail and them trim the front and back ends off.
Once a 1mx2m sheet of 18 gauge NS4 was obtained I was able to make the driver side panel. The passenger side tunnel panel was a good fit if reversed, so this was used as a template with appropriate changes for the lack of handbrake and raising the lower edge into the pedal box and a few tweaks to the edges to get the alignment correct on the chassis.
The tunnel top was easy enough. I measured the length and width from the centre-line and the location of the gear stick hole and transferred these measurements onto the reverse of the sheet of 16 gauge. Nearly made the same mistake not reversing the measurements again with the gearlinkage mounts being off-centre. This panel needs to removable so I attached it with stainless M5 cap head screws into rivnuts.
The scuttle panel took ages to do for some reason. Fitting the main bulkhead was very simple transferring measurements directly from the chassis onto the panel with a marker pen. The battery box floor was simple enough but the sides took about 6 attempts to get a fit that I was happy with. I was a little disappointed to see a slight curve in the bend where the main bulkhead panel forms the rear of the battery tray, but I guess this is what you can expect if you don't have a sheet metal bender and use a kitchen table, long steel rule, bit of 2x2 and g-clamps.
I was slightly hesitant of starting the side panels because they seemed to have lots of attention in the build manual and thus I thought they would be difficult. They were actually quite easy. Once the clearance for the front suspension mounts and headlight is cut out the panel will lay on the side of the chassis and you can draw round the chassis with a marker pen. I used a 5mm drill to define the end of cuts into the panel to try and prevent it from splitting - this seemed very effective and a tidy way of making concave edges. I reversed the first side-panel to check the fit on the other side. It was necessary to slide the scuttle forward by 2-3 mm when marking out. In fact it turned out that the second panel, which was a copy of the first was a better fit! The bottom edge was the first to bend over and fix, this was very easy due to the aluminium being much softer than the NS4 and also thinner at 20 gauge. Once the bottom edge was bent and drilled I removed the panel and put some panel bonder on the outer edge of all of the chassis rails in order to prevent unwanted vibration or resonance. The panel was replaced and the bottom edge riveted followed by the returns around the top chassis rail and scuttle. I measured the length of material required around the rounded cockpit side rails and thought that I would need 3/4 of the circumference of 1", which was the diameter of the round tube. However this was only just enough to wrap just beyond 1/2 way round. With hindsight this is obvious as the diameter of this bit of the panel is bigger than 1". As it says in the build manual - leave plenty of material to fold round. Folding round was easy by hand and I formed the final shape by clamping inner and outer edge with g-clamps and wooden battens and then tapped over the final inner edge with a rubber mallet. I found that the front and rear edges of this rounded section of panel tended to stand slightly proud of the round-tube, which could then catch on someone getting into or out of the car. I decided to bond these down with some Araldite. Before the panel was attached I made a template for the exhaust cutout whilst the engine was in the bare chassis. I spent a while on this trying to decide whether to make a curvy cutout that followed the cross-section of the exhaust or a more simple hole. In the end it was obvious that I needed to allow sufficient clearance to fit the exhaust through, which was a rectangular hole and that the cross-section was generally trapeziodal, so I decided to make a trapezoidal hole following the angle of the down-pipe from cylinder 1. All holes in the side panels were very easy to make with lots of small holes drilled though, roughly snipped round with tin-snips and then filed to the final shape. It was very easy to file large amounts of material away due to the sides being soft and thin. I think that bonding the side panels to the chassis also made them very tight and less prone to distortion when working on them.
I followed the measurements included in the build manual for the front suspension cut outs. One mistake I did make with the side panels was in cutting out the big hole for the rocking arms relative to the line of the top chassis rail rather than the bottom one. Due to the slope of the top chassis rail relative to the bottom of the chassis (where the suspension is mounted relative to) this meant that the hole was too narrow at the rear and the top rocking arm would not go through. It was fairly difficult to file this edge down once it was on the car and would have been easier to get right whilst on the bench.
Overall the paneling took a lot longer than I anticipated. However I was being very fussy about the fit ensuring even panel gaps along chassis edges and getting the rivet lines straight and evenly spaced. As all my panels are going to be on show forever I thought I would rather spend an extra day or two getting it right.
One thing I did learn was that the absolute best way of cutting out the panels was with a jig-saw and fine metal blade. I tried tin snips and a guillotine, both of which tended to round over the cut edge or worse still snag and cause the panel to become distorted. I also found it very difficult to cut a straight edge with these and after cutting out the panels required a lot of filing to get a good straight edge again. On the contrary it was possible to cut a very accurate straight edge with a jig saw (on the reverse side of course) that required minimal filing to get a great edge. I had assumed that a jig saw would wander about and not cut a straight edge but this was not the case.