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Bonnet fitted - click for larger size

15. Bonnet

Bonnet Panels

The aluminium bonnet is made up of 4 panels. There are 2 plain tops which are hinged down the centre and 2 louvred side panels which are fixed. All are supplied a little longer than required and need to be trimmed to the correct length and angle. Notice the protective covering on the aluminium.

Centre Hinge

Hinge components - click for larger size The supplied brass hinge (which is chromed later in the build) first has to be cut to length. It is best to take the same amount from each end otherwise the position of the bolts will look unbalanced. A 3/4" p-shaped flap is also cut from each end (without the hinge pin) and these are used with small aluminium mounting blocks to mount the hinge to the cowl and the scuttle. Before mounting them, however, it is necessary to countersink them and round their ends.

Holes must be drilled in the hinge for the bonnet top fixing screws (M4 stainless socket head bolts) and great care must be taken as they will be prominent down the centre of the bonnet. It is certainly best to dot punch all these first and use a pillar drill.

Top Panels

Fitting bonnet - click for larger size The top panels are aligned with the hinge and the ends measured & trimmed very carefully (back end first). Having first marked a line, I used a jigsaw to cut close to it and then finished off with a file. Standing the panel on its end on a flat surface (e.g. some thick MDF - medium density fibreboard) enabled me to see any imperfections. I also found a 3mm drill bit useful as a way to check the gap between the panels.

Once the panel is trimmed to size, it can be clamped to the hinge which is used as a template to drill the holes for the panel fixing screws. I first drilled just one each end and one in the middle and then assembled it with screws to double check before drilling the rest (with the clamps no longer needed). The left (nearside) panel is also reinforced with a piece of aluminium angle.

Side Panels

Bonnet side bracket - click for larger size Surprisingly the side panels seem to be more awkward. The sides are supplied with the fronts of the bottom edges shaped and folded to clear the crossmember but I found this gave insufficient clearance in my case. I made some adjustments and then set about trimming the panel to the correct length. This time I found it easier to trim the front end before the back. A piece must also be cut from the back of each end of the top flange to make room for the bonnet rubbers. Note that the thicker rubber supplied goes around the cowl and the body tub and the thinner self adhesive rubber goes along the side shut lines. Of course, neither are fixed until the body has been painted.

The supplied brackets (after slight bending to match the angle between the body and the panel) were then fitted to the ends of the flange. The bottom will be held in place by the front wing but I decided to add a further fixing near the bottom of the back end to hold it in.

Bonnet Catches

Bonnet catch - click for larger size The striker (or stud) part of the catches were bolted to the edge of the bonnet tops so that the M4 bolts did not coincide with the side panel bracket bolts. This then gives adequate clearance. After experimentation on an off-cut of GRP and careful measuring in situ, I decided that the main (sprung) catch plate would be mounted 68mm below the shut line (i.e. about 71mm below the striker plate). This provides a fairly strong pull which helps to compress the bonnet rubbers.

The catches have a small rubber buffer which pushes rather hard against the side of the bonnet panel. So I used a new Stanley knife blade to pare a little away to make the catch sit more comfortably and not pop off.

A small cover was made and added to the base of each hinge as a precaution for the SVA test.


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