Changing width of Fibreglass Rear Arches

The overall rear end width of your Locost will depend on your use of axle/IRS, wheel/tyre width and your wheel offset. Luckily for me (NOT) I ended up needing rear arches of about 240mm (9 ½ inches). This proved to be a huge curse as all the arches on offer were just too small or miles too wide. I was OK with modifying rear arches but did not fancy buying new rear Locost arches for £120 plus, and then cut and shut them and re-spray them. Trying to get second hand items was getting just as hard, as everyone was looking for second hand units and paying good money for them, the Locost bug really has swarmed big time.

 Eventually after what seemed like years I purchased a rear set for £50 through E-Bay and travelled about 45 miles to pick them up. I knew much about engineering cutting and fixing but had little experience with fibreglass. I visited a classis Morris Minor restorer and asked his advice, He told me I had to remove all paint, gel, dirt, grease from the joining faces and sand them back to pure clean fibreglass to get a perfect bonded joint. I bought fibreglass resin, matting and hardener from my local Wilco motorist centre ready for my final rejoining.

Lets Get To Work!

The arches were offered up in position on the Locost car and small blocks of wood placed on top of the tyres lifted the arches up to the correct height, to set up position against the body. The arches in position looked good, but were about 50mm too wide, so the tyres were set well inside the arches and it looked a total unprofessional bodge! I measured exactly how much cut would make the arches sit just outside the tyre edge, and look professional. I used a small block of wood and drilled a hole at this distance from one edge, big enough to hole a marker pen. With the arch still in position, I marked a cut line along the arch, using the wood block/pen marker. This would make the cut arch fit the body line perfect, to any lumps or dips in your rear side panel.

The cut is made to the inside edge of the arch, and has the 90degrees mounting edge on it, refer to drawing!

The arches were removed and the cut made using a 4 ½ inch grinder with a narrow 1mm cutting disc in it. This cuts like knife in butter so be careful, take your time and prepare the job before you do it! Cutting to the exact size allows you to remount the cut off flange to the arch giving you final width and a mounting flange again. The cut off was trimmed until it fitted back inside the inner edge of the wheel arch. Fitting it inside the original arch makes the 2 radius's slightly different so I started clamping around the join which will re-match the pair. When I finally would join the pair I thought clamping would be a bit tedious for one person so I drilled 4mm holes, about 6-7 of them equal distant apart around the join. I used short M4 brass screws and nuts to keep both parts clamped together. When I was satisfied with the result it was offered back up to the Locost body side and now looked the correct width.

The arches were removed again, both sides taken apart and the M4 screws removed. A soft pad in the 4 1/2 inch grinder was used to remove all the paint and dirt from each surface to be joined until they were clinically clean. A mix of resin and hardener was made up for one side arch and each mating face to be joined, coated with a generous covering using an old paintbrush. Working quickly, the two parts are assembled together and the M4 screws and nuts assembled and tightened, making a good joint. When the resin has set after time the screws can then be removed. # some of the screws will be locked into the nuts with resin and will break when you try to remove them# this is why brass screws were used, as they are soft and will break easily and can be knocked out with a 4mm diameter pin punch.

The overlap on the inside of the join was cleaned back with the softpad and 1 or 2 layers of resin and matting applied to reinforce the join. On the outside of the arch, the 4mm screw holes were filled using body filler, and any imperfections, deep scratches were filled with body stopper ( a very fine body filler applied with a knife). After applying a few good coats of etch primer, and rubbing down to a smooth un-blemished finish, the arches can be finally sprayed to the final colour to match the Locost body panels.

I had purchased carbon effect stone protectors, for the arches and I cut these down in size to match the new size arches. I fitted these once again using M4 brass screws and locknuts. The brass screws look good against black carbon fibre effect. The arches are screwed to the body sides using M6 stainless steel bolts with mudguard washes and 6mm locknuts. A rubber edging strip is used to give a clean looking edge against the body sides, and the mudguard washers, give a bigger contact area and prevent damage around the 6mm mounting screws.

If you are unsure about working with fibreglass, try looking at supplier sites as they usually give you good information about using their products and goods tips and techniques. Just a little example of what i looked at - Laminating

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