Q300 OBP Coming back to life

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Q300 OBP Coming back to life

Postby ACourtney » Fri Sep 28, 2012 9:15 pm

Q300 OBP is the Gold Coupe that we are rebuilding for Desmond Gorman. The car itself was known to MOC members as the Grey Coupe belonging to Becky Falstein. It passed through another owners hands, who whipped the original 1380cc engine (for a GTM I'm told) and never fitted the standard 1275cc replacement.

ImagePic004 by Alistair Courtney, on Flickr Before starting work.

Desmond didn't like the original grey colour and wanted something more vibrant, so a full respray was in order. He also didn't like the leaky old sunroof, with its rotten seals and rusty clips. In fact Desmond wanted a solid roof and the best way to do that is to mould the roof in place. So the first job was to make a mould for filling in the sunroof. Fortunately, I now have a Mk3 Coupe of my own, waiting for its own rebuild (someday!), and it does have a solid roof so the roof was polished up and used as the plug for a new roof mould.

Blue car roof.jpg
Roof polished up ready for laying up mould
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The rest of the car was not as smart, but I still didn't want to cover it with splashes of resin so I masked off the rest of the car with plastic sheeting and then layed up the mould in the traditional way: First the roof got six coats of wax, then I applied two layers of gelcoat - I figured that I would probably be using this mould again - before laminating with six layers of CSM and a section of coremat for extra rigidity.

Gelled roof.jpg
Gelcoat applied to roof
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Last edited by ACourtney on Tue Jul 05, 2016 9:04 am, edited 2 times in total.
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Re: Q300 OBP Coming back to life

Postby ACourtney » Fri Sep 28, 2012 10:26 pm

Mould before trimming.jpg
Mould just after lifting - yet to be trimmed.
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Once the mould was trimmed and ready for use, it was time to turn our attention to the car itself.

It is easier laminating down on to a horizontal surface and, as the car was to be stripped for the respray, it made sense to invert the car and layup the new roof section within the old sunroof opening.

First the old sunroof was removed. Apart from a couple of rusty self tappers, it came away easily enough and left a reasonably clean surface behind. The old sealent came off rather too easily, which is probably why the sun roof frame was rusting.

Bare roof.jpg
After removing sunroof
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Then the big job of stripping the car down began. The subframes came away quite easily. The engine had been removed by the previous owner, which made the job easier still. With all the panels removed and just a few items of interior trim remaining the shell was ready for the rotisserie:

Bodyshell on rotisserie.jpg
On the rotisserie, ready for roasting.
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The rotisserie was made from the A-frames that form the rotisserie for the 2+2 moulds. If the frames are strong enough to support a full set of moulds and a finished Cortez bodyshell, they were going to cope fine with just a bare Gold coupe shell ;) . The attachment frames at each end were purpose made and attached to some of the strongest, thickest parts of the bodyshell (including a pair of front subframe mounts at the very front).
The rotisserie also gave me the chance to give the underside a good clean.
Last edited by ACourtney on Tue Jun 07, 2016 10:06 am, edited 1 time in total.
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Re: Q300 OBP Coming back to life

Postby ACourtney » Fri Sep 28, 2012 11:05 pm

With the car rotated on its side, it was an easy job to fit the roof mould. However, I wanted a good tight fit as I wanted the new section to be perfectly aligned with the original roof line to keep the filling, sanding and flatting to a minimum. So as well as some G-clamps I used a dozen bolts through both the roof and mould to clamp them tightly together. This of course meant drilling holes in both the roof and the mould, but the holes in the roof would be easy enoughto fill with bridging filler later on.

Mould fitted.jpg
Mould clamped and bolted in place.
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The mould had off course been prepared with six coats of wax and a coat of PVA, whilst I had also polished and waxed the old roof surface so that any excess resin that got between the mould and the roof would not stick to the roof - in the event I saw none so I must have got the mould fitting pretty snugly.
Also before fitting the mould I had taken the grinder to the inside edges of the opening, feathering back the first four or five inches (sorry to the continentals for the continued use of imperial measures, but I started on cars working with my Dad who was a good old fashioned British engineer and used good old fashioned British units) of GRP to give a tapered edge. This meant that I could apply progressively larger pieces of mat to increase the overlap and blend the new section into the old smoothly. But the first step of course is the gelcoat and with the car now fully inverted, painting this in was simplicity itself. Being a Midas, the original gel is pretty thick, so I double gelled it to match:

Gelled opening.jpg
Opening now double gelled - note also the tapered edges.
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And once the gel had gone hard, but tacky, it was ready for laminating. The first layer of glass matting fitted exactly to the old opening, and then the next overlap by around 1 1/2" to 2" all around. The next layer was another 1 1/2" to 2" larger still and the last layer overlap all around and coved the whole roof area bounded by the reinforcements front and rear - with some holes left to clear the bolts. I didn't really get a very good photo at this stage as the freshly laminated glass matting just looked blurry in the photos taken further back, but a close up of one corner came out clearer:

Laminated roof.jpg
Close up of newly laminated roof.
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Re: Q300 OBP Coming back to life

Postby ACourtney » Fri Sep 28, 2012 11:14 pm

Well this has taken me quite a bit of time posting it all up, so I'll just post one last photo before calling time. This was clearly not the end of the story. In fact it was just the end of the first of many stages, but this is how the roof looked immediately after removing the mould:

Mould off.jpg
With the mould off, the new roof surface was almost perfectly aligned.
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More next time.
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Re: Q300 OBP Coming back to life

Postby lankyjames » Sat Sep 29, 2012 7:46 am

Excellent work there! Really interesting to see all the processes that go on to achieve this!

With my rusty roof I had considered the same treatment, but I've also realised I use the sunroof cavity...for extra headroom...

Looking forward to another installment
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Re: Q300 OBP Coming back to life

Postby Stuart » Sun Sep 30, 2012 8:57 pm

That's very interesting Alistair. I have a couple of questions, what do you use for grinding the chamfer? and do you have to grind the join from the outside and fill?
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Re: Q300 OBP Coming back to life

Postby ACourtney » Mon Oct 01, 2012 9:10 pm

The next step is indeed to laminate some strips of glass CSM over the top of the join. The new section may have got a good bond, but only from one side. I wanted to be sure that the roof was as strong as, if not stronger than the original, so I had to take the angle grinder to the top surface and created a tapered area around 3 inches wide either side of the join line to allow additional glass to be laminated on top.

Roof ground back again.jpg
Roof join ground back in preparation for laminating in additional CSM strips
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To achieve a good smooth taper, I start with a flexible grinding disc in the angle grinder, probably P80 grit. Once I have roughed out the taper I smooth it off using P120 production paper on my trusty old 3M body file. It is important to achieve a smoothly blended edge to the old gelcoat so that the new filler blends into it gently. Otherwise sudden changes between gelcoat and filler can show through the paint as shadows.
The sharp eyed will have noticed that I also tapered back around the bolt holes. These were filled from both sides with bridging filler (glass loaded polyester, such as Isopon P40).
Two layers of CSM strips were then laminated across the join, starting with one layer about 4inch wide and then a layer at 6 inch wide. Once that had set hard it was time to apply the filler.
I prefer to use aluminium powder filled bodyfiller, such as Metalik or Chemical metal. My preference is based on experience gained over the years and is probably a bit of overkill for a GRP body. Most bodyfillers, such as P38 and Easy Sand use talcum powder as the filler agent. It is cheap and makes sanding easy. However, it is hydrophillic, i.e. it attracts and holds water. This is why repairs on steel panels with talc based bodyfiller can rust through and start to lift. On GRP panels if the talc based filler isn't sealed properly it will take in moisture and expand leading to ripples and bumps. Having said that, part of our paint process is a layer of epoxy undercoat which is strong, flexible and pretty impervious to water, petrol etc. So maybe my expensive taste in bodyfiller is just overkill.

The filler stage is where the efforts of making a good mould and getting it fitting tightly to the roof really paid off. Having the new roof section perfectly aligned to the old roof section minimised the amount of filler required and the amount of flatting back with the bodyfile. Not only does that make it easier work it makes for a better job all round.

At this stage we had a minor family crisis which meant that I couldn't get to the workshop much for a couple of months. I also got out of the habit of photographing every step, so there were no more photos until the car was in the spray booth. However, one side benefit of my slowed process was that it gave the new section a few months to settle down and release excess styrene. One problem when painting newly moulded GRP panels is that they continue to release styrene for some time - hence the "newly moulded" styrene smell that comes free with every Midas kit - and the styrene can create micro-bubbles in the newly applied paint. The usual treatment is to place the car or panels in a low bake paint booth overnight to speed up the aging process, but leaving it to stand for a fews months can only help.

Well the next stage was getting it all painted, but I'll save that for another time.
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Re: Q300 OBP Coming back to life

Postby Stuart » Tue Oct 02, 2012 2:28 pm

I'm looking forward to seeing the shell in paint.

I'll be needing to fill in my sunroof at some point, I realise your way is best, but may have to laminate just a panel into mine, just hoping a mk2 roof is close enough for making the panel.
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Re: Q300 OBP Coming back to life

Postby b1zbaz » Wed Mar 13, 2013 9:48 pm

Come on we need more info on this car
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Re: Q300 OBP Coming back to life

Postby lankyjames » Wed Mar 13, 2013 10:04 pm

I have pictures of this car in its paint...but I will ask AC if it's okay to post first :)
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