Section XIX The Scuttle, Bonnet, Firewall & Nosecone

The " Crocodile " Bonnet was not, in my opinion, an ideal solution. It was therefore decided to fit the more traditional style of Bonnet with a Scuttle, Bonnet and the fibreglass Nosecone as three separate units, although this would involve at lot more work. The Scuttle and Nosecone being rigidly fixed to the car and the Bonnet either clipped or strapped in place. If you intend to fit the standard RHSC's Crocodile Bonnet, read no further. Visits to Kit Car Shows would indicate that there are many Bonnet permutations other than the one described.

Note:- Since carrying out the modification described below I have been advised that the Bonnet is supposed to sit somewhat above the dash tube with a suitable spacer. The higher scuttle raising the top rail of the windscreen. It is essential that the seats are lowered as much as possible, by removal of all the undergear, so that your eye level is below the windscreen top rail. These points need checking out before any cutting. As the build has proceeded there have been no problems with the suggested design.

Section XXI covers fitting the Heater/Demister and the Wipers.

A trial fit of the two pre-formed Bonnet halves showed that if the Bonnet was to sit down flush onto the curved dash tube AND line up with the chassis side rails it was nearly 2" too wide. It was also too wide at the nose cone end by a somewhat lesser amount. As the Bonnet comes as a fully folded and louvered unit correcting any errors would be a major problem, since to do the job properly needed a guillotine and a folder capable of taking at least 50" The obvious solution was to remove the 90 deg centre fold, guillotine off the excess material (not the same front to rear) and to refold the two flanges. Due to lack of suitable equipment most builders would be unable to carry out this work and as I did not feel confident farming out the folding work to a sheet metal worker away from the actual car, a solution was needed that left the builder in full control and one that could be done more or less " in house " with available equipment.

The work was done as follows:-

The fold down the centre of each half was carefully removed using a pair of left handed tin snips, taking extreme care not to mark the top surface or distort the Bonnet, but leaving as much metal as possible in place, the Bonnet was then reassembled in the final position, hard down onto the dash tube, the nose cone and the side rails, but with the two halves now overlapping. Use "G" clamps at the scuttle end and cut a dummy former from 19mm chipboard for the Nosecone end. Use a rope tourniquet round the Bonnet and chassis to really pull it home tight onto the 19mm former and the side rails. While the Bonnet was in this position, the proposed scuttle/Bonnet joint was marked off. The best position is over the centre of the vertical chassis tubes located at a point that will give the new Bonnet a length of 910mm with a scuttle 290mm long. This also corresponds to the rear wall of the Battery Tray. Note the cut needs to be a VERTICAL slice relative to the floor. The exact centre of the Bonnet was established and a snip cut through both pieces at the centre of each end. The excess material was cut off by the local sheet metal company. Tin snips are useless, they distort as they cut.

Caution. Check that the sheet metal clamps on the guillotine do not deform the louvres when cutting.

The two halves were then pop riveted to pieces of 19mm x 19mm x 3mm Alloy angle, using 3.2mm x 8mm long Stainless Steel rivets, running almost the full length of the Bonnet. Take care not to rivet too close to the ends or at the location of the proposed lateral cut. Stop the angle about 25mm short of the inside of the scuttle tube and the nose cone flange. The outside vertical face of the angle should line up to the exact cut edge of the Bonnet. The joint can be made perfect, once riveted, by dressing back to the angle with a fine file if required, but it will be covered by the alloy Tee piece. The two halves are now joined up as per the original design, but the joint is covered by a 16mm x 19mm x 1.6mm Tee shaped piece of alloy. The only supplier I could find for this Tee section was Coach Trimming Supplies of Birmingham but they do good a mail order service. See links page for supplier. This covers the gap 100% and gives a very finished look. In my opinion far better than the original design, but a lot more work. Make sure to fine polish the Tee before fitting as you cannot do it later without marking the Bonnet. Make sure the pop rivets are wide enough apart to miss this Tee piece and stagger the internal bolts to miss the pop rivets. It is a lot easier if all the holes in the Angles and the Tee section are drilled as a unit and then the holes spotted through to the Bonnet. Use dummy packing if required under the Tee section to raise it 0.7mm above the angles as the Bonnet must fit in here.(use the Bonnet off cuts) There is an AutoCAD sketch of the joint. See Appendix II Link to AutoCAD Drawings When pop riveting, work from one end only to avoid blisters. The Bonnet panel must sit dead flush to the upper surface of the angle and also make sure both angles are DEAD STRAIGHT and matched as a pair. I used a drill jig to get the rivets 100% in line and spot on pitch. It is essential to bolt the angles together during pop riveting. They will NOT pull into line after riveting without distorting the Bonnet somewhere. If you rivet as a pair all in one go then they must match. Perfection is required in the alignment and pitch of the rivets as this is one of the first places the eye rests. Also make sure the joint is dead centre. There is also an AutoCAD drawing of the proposed rivet pitches which works out at approx. 64mm. Use this drawing to make the drilling jig.

This is not an easy task to do well, but you are in 100% control all the time and you only do it once, hopefully.

We now come to the worst part, cutting the scuttle off. After plucking up considerable courage it was cut off using a normal hacksaw, cutting from the two ends and the middle. Not easy but it can be done if you are careful. Use a new fine blade, some metal will still need to be cut by hand, as the hacksaw frame gets in the way. Dress up the cut ends with a fine file and fit the scuttle halves to the dash tube and the side rails with 6mm Pop rivets. It is vital that you get the position of the scuttle correct, it must be measured BACK from the recess in the Nosecone when this is in its final position. Allow an extra 12mm FURTHER BACK to allow for the Bonnet rubber, and also give a nice overhang into the cockpit. Don't forget you have to fit a padded dash panel onto the scuttle tube and this is quite thick. You also need to allow room to fit the heater vents underneath. All this takes a bit of forward planning but you only get one go. I got this wrong and had to cut about 10mm off the Bonnet so it would fit. This leaves the end of the scuttle open, and this needs to be filled by the ply Firewall. Before finally fitting the scuttle make sure it is in perfect alignment with the Bonnet and Nosecone. There is an AutoCAD drawing showing a section through the firewall joint. Other builders have used an electric jig saw with a fine blade or a metal cutting disc in an angle grinder, both these methods need a very steady eye and hand and some practice. The rear louvres may allow rainwater to fall into the drivers footwell and onto the electrics. Blank off the louvres and/or fit panels underneath if required. Another possible solution would be to fit a nice Stainless Steel Piano Hinge on the centre section instead of the Tee to give a real vintage style opening Bonnet !! How nice to be able to open up each half. This type has been seen at shows, so it can be done. If you bolt the two halves together initially with the Tee you can always fit the hinge later if required.

Firewall

The Firewall is made from a 1220 x 330 x 19mm piece of good quality marine ply. First cut a very precise fitting template from substantial cardboard, and transfer the shape to the ply. Check and re-check all cut-outs, ie:- side tubes, steering column, pedal box stay, cut out for the centre "Tee" and finally the Heater aperture. You will also need holes for the wiring loom, speedo cable, washer jet tubes, heater operating cables and anything else you can think off. All these holes are best put in whilst the Firewall is off the car. Once the Firewall fits perfectly just inside of the scuttle a further 4mm at 7.5 degs to allow fitting of the Bonnet support/scuttle joint will need removing. See Appendix II Link to AutoCAD Drawings This makes this assembly very clear. Once you are 100% sure of the Firewall fit give it a couple of coats of varnish. Do not forget that the two side tubes are angled at approx. 25 degs, so the two 38mm holes will also slope down (8.5mm in 19mm) Tricky, needs plenty of work with the rat tail Surform. A couple of alloy angles are also fitted to the tunnel top/rear firewall joint. The Polo Heater assembly was fitted BEFORE the firewall was offered up to the car together with all the electrical connections on the PWS Instrument loom. see photo of the completed Firewall prior to fitting.

Before finally fitting the Firewall, fit all the items under the scuttle, the Wiper gear and Motor, Washer jets and tubes, Demister vents, Switches and Controls etc. All these items must be fitted and designed to come out downwards and rearwards into the car with the scuttle in position, as once the scuttle and Firewall are finally fixed there will be no top access, and none at all from inside the engine bay. Just like any other car really. The scuttle is not very long so there is quite good access from inside the car once the Dash is removed. Note that having removed a couple of inches from the centre of the Bonnet the wiper and heater apertures are closer together than the standard RHSC's design. Once all the above work is completed the Firewall can be finally fitted to the scuttle. Finish off with a Bonnet rubber moulding. Once the Firewall is fitted it should (hopefully) never need to be removed. The work on the modified Bonnet, scuttle and Firewall has taken months of careful work which is now more or less complete.

When fitting the Bonnet and Firewall attention should be given to the ingress (or lack of) water into the car. This problem is largely overcome in the "crocodile" Bonnet as there is no joint to worry about, apart from the lower edges. All holes into the passenger area should be sealed, as water will get in. You will need to drill a hole in the footwells for water to drain out. Leave this until the car is completed and find the lowest point. Fit a rubber bung. A run in the wet will soon show up where the water can get in. See also the SVA note in Section XII Internal Sheet Metal Work.

Rear View Mirrors

Although every picture of a 2B in the RH brochure shows mirrors fitted to the Scuttle, mine failed the SVA as being too low. As usual the RH supplied mirrors are next to useless as the only place they will fit properly is on the Scuttle. Tiger Racing supply Universal Rear View Mirrors that can be fitted approx half way up the screen pillars in a more suitable location. Tiger Racing use these on their kit cars and have had no reported SVA problems. see Section XXV The SVA Test. The height of the mirrors can be determined by stretching a piece of string from the 10m marker line (see the SVA manual) just clearing the upper portion of the rear mudguards. Where this line meets the windscreen pillars marks the LOWER EDGE of the mirrors. This came out to approx 850mm on my car. Add a bit for luck, but as the car sits down when loaded vision will improve. Watch out that the roll bar is not to evident in the field of vision, pack the mirrors out if required. I put a pair of Tiger Racing mirrors as far up the Windscreen pillars as possible and passed with no trouble. See photo in the SVA section.

Final position of "Tiger" Mirrors

Interpretation of the SVA Regulations.

These details are taken from the Draft Version of the SVA Manual March 2004, so please check with the current version. The Mirror Test Procedures require the services of a Baltimore lawyer to unravel, as they are quite involved. First of all measure from the ground the height to the upper edge of the mirror lens for the nearside, offside and interior mirrors. Note these heights on the SVA tabular sheets, mine were 1000mm interior and 910 exterior (pg.2 right hand figures in the SVA manual Section 10) Note the Y dimensions (820 and 746mm) and the Z dimensions (475 and 432mm) respectively. Now refer to pg. 4 (this needs to be printed out in colour) The upper green block on pole 4 is set at 1000mm and the lower green blocks on poles 2, 4 & 6 are set at 820mm. The lower red blocks on poles 1 & 3 are on the floor, whilst the upper red block on pole 3 is set to 910mm. The lower blue blocks on poles 5 & 7 are set at 432mm and the upper blue block on pole 5 is set at 910mm. This does assume that both exterior mirrors are positioned on the car at the same height, modify these dimensions to suit your own car. With reference to the floor layout on pg.1 the poles are placed 10m to the rear of your "eye position", not the mirror position, with (a) & (c) lines set at the extreme width of the car (usually the Rear Mudguards on a 2B). Pole 4 is on the cars centre line, pole 3 is in line with line (a) and pole 5 in line with (c). Pole 1 set 2.5m from pole 3. Pole 7 set at 2.1m from pole 5. Poles 2 and 6 are set 1.8m either side of pole 4.

When seated in the car with the seat in the rearmost position, all the appropriate coloured blocks should be visible by turning the head left to right only. There are other conditions but these are best read from the manual. If your mirrors do not meet the viewing requirements they will need to be re-located. The best method is to get an assistant to hold the mirror "where you think it needs to go", check for visibility and move the mirror around until you are happy. THEN FIT. Otherwise you may finish up with loads of unwanted holes. Even if an interior mirror is fitted a nearside external mirror will still be required. I removed the Headrests from the RH (Vectra/Rocarro) seats for the SVA test, no comments from the tester, just a pass.

Nosecone

The Nosecone can now be fitted using the Bonnet front edge, which is more or less fixed, (see above) as a guide to its fore/aft position and height. First carefully cut out the front hole and sand to remove any burrs. Two 3" Stainless hinges are pop riveted to the lower front cross member and the lower edge of the Nosecone bolted to the hinges between two pieces of alloy plate. This allows the Nosecone to pivot forwards for total access to the radiator/fan assembly. Thread the 4 short studs on the Grill M3 and drill the Nosecone carefully to accept the studs. Secure with 4 x M3 nuts and washers. Loctite in place. The rear of the Nosecone is held in place by a couple of "L" shaped brackets and these double up as anchor points for two wire straps that prevent the Nosecone falling forward onto the floor. The wire straps were fabricated by the local boatyard and are covered in neoprene tube to stop any rattles. See photos below. The rear edges of the Nosecone sides are more or less in the "as moulded state" and these were covered by a couple of lengths of clip-on rubber edge moulding to satisfy the requirements of the SVA. It gives quite a neat finish to the edges and will be left on.

Bonnet Clamps

The new detachable Bonnet comes out at approx. 910mm o/a. If you have done your cutting well, the main support for the Bonnet is the chassis side tubes, and four vertical location dowels are suggested, this will stop the Bonnet splaying outwards and help it keep its shape. A couple of thin internal hoop shaped angles, riveted in will stiffen up the front and rear of the Bonnet quite well, as will the centre angles & Tee infill. The Bonnet is held in position by four SVA approved Lolocost Flexi Bonnet Catches, see Pg 48 of the new RH catalogue. These are manufactured by SOUTHCO Part No. C7-10. For mounting details go to Southco's web site www.southco.com where you will find all the information you want. I used a simple drill jig to get all the holes at the correct centers and also avoid any scratches. The Bonnet is further secured by a couple of short "period style" leather straps from Coach Trimming Supplies of Marston Green. I doubt if these are SVA approved and this may be a belt and braces approach but I have heard far too many stories of Bonnets flying off. They did in fact fail the SVA, see Section XXV The SVA Test. For the re-test they were removed.

Leather Safety Straps (SVA Fail)

Both the Bonnet and Nosecone sit onto full length strips of 35mm x 6mm self adhesive foam. This gives a soft platform for the Bonnet and stops rattles. All sharp Bonnet edges are covered with chrome "Mini" style "U" trim.

All this work takes hours of patient careful work, but the Bonnet is a central feature of any car and it is well worth the going that extra mile for perfection.

Indicator Wiring	Check Straps	Nosecone clips	Bonnet clips

Clearances

Check all clearances for items in the engine bay before final fitting. The underside of Bonnet lies close to the engine Oil filler cap and the top of the Weber carburettor air filter. With the Bonnet and Nosecone sides hard down onto the chassis and lamp brackets the underside of the Bonnet is 30mm off the filler cap, less the alloy angle still leaves 10mm clear which should be plenty. Clearance for the air cleaner on top of a Weber downdraft carburettor is a bit more problematical, but my build has turned out OK. My 2B Bonnet is probably as low as you are likely to get, as it sits directly onto the scuttle top tube. If you have a problem try the Demon Tweaks disposable foam filters. Watch out for the possibility of water entering the car via the Bonnet louvres.

See also the section on Radiator fitting.

Go to Section XX

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© Colin Usher 2005