Wind deflector part 2

After creating the template (see last post), I applied masking tape to the polycarbonate where it would be cut. Then I marked the shape of the template on to the masking tape, including the eye bolt hole centres. A soft cloth was put on the bench to avoid any scratches when cutting. The deflector was cut to the shape of the template using an electric jig saw (use the correct blade and a very slow speed to avoid melting the material - I used speed 2 out of 5). The part cut from the bottom was supported by tape to avoid it snapping when the cut was near to the end.

Polycarbonate cut to shape

Next the four holes for the seat belt anchorages (eye bolts) were drilled. A 4mm hole was drilled first as a pilot hole with a sharp HSS bit. After checking that the pilot holes were in the right place, these were then drilled to size, using a 22mm hole saw.

The edges of the polycarbonate were shaped with a file. Then they were finished off with P80, P400 and P1000 wet n dry paper. Finally the edges were buffed with a foam pad and G10 polishing compound, using the polishing machine. The edges now look like glass.

The fixings, but note that the screws used were 30 mm long

Next the deflector was temporarily fitted on to the roll hoops using just the seat belt eye bolts. The six fixing holes (to locate the P-clips) were marked on to masking tape.

A soft cloth was placed on the bench again to protect the polycarbonate and then the holes were drilled out gradually to 6 mm. It is advisable to drill in to a block of wood to stop the polycarbonate cracking. The deflector was then temporally attached to the roll hoops again, with the P-clips and using M6 x 30 mm button head screws with nylon nuts to make sure they were in the correct position.

Once I was happy with the fit and finish, I removed the protective film from either side of the polycarbonate. Then I wiped the dust from the polycarbonate with a soft cloth.

The deflector was then fixed in its final place. The metal washers go under each screw head and against the outside of the P-clip, with nyloc nuts to stop the deflector working lose (make sure that the plastic washers are against the polycarbonate to reduce the likelihood of cracking). Finally the eye bolts were refitted, along with the seat belts.

Finished wind deflector in place

Does it work? Well it doesn't stand out or detract from the Cobra's lines. It does cut down on the wind behind you head significantly, but it does not totally eliminate it. To do that a hood, a hardtop or a tin top would really solve the problem.

Wind deflector part 1

Yes, I am a wuss! Its official. The back draught of cold air and buffeting in the Cobra at this time of year especially (when it is cold) needs taming. I do have a beany hat and a scarf to help keep out the worst of the cold. But most importantly, my wife prefers her hair the right way round!

I researched the subject on the Internet, the Cobra Club Forum and read an article by Paul Hutton (which is really good) in the April 2017 publication of the Snake Torque magazine. From this research I reckoned that there was a way of cutting down the draught on my neck and my passenger's without detracting from the Cobra's lines. So here is what I have done.

Template

First the four seat belt eye bolt anchorages were unscrewed from the roll hoops. The wind deflector will fit behind the seats and onto the face of the hoops. Masking tape was applied to the body on the cabin side of the roll hoops to prevent any marks.

Eye bolts removed and masking tape applied

The template was made of hardboard. Duct tape was used to hold the hardboard in place each time it was removed and refitted.

Duct tape on back to hold template

First, the hardboard was marked up to follow the body of the car, then cut with a jig saw. After the first cut, it took a bit of messing about to get the right gap all the way across at the bottom.

Hardboard with first line drawn

Once I had this sorted I marked up the top and sides. The deflector extends 50mm beyond each roll hoop towards the outside of the car.  If the deflector extends any further it will scoop up the air passing down the side of the car and channel it behind your head, defeating the whole thing!

Then I marked up a slope - from the top middle of each roll hoop to the outside (about 75mm down from the top), before marking rounded corners. The top corners were a 75mm radius and the bottom corners a 25mm radius (hope this will be ok for the hood or hardtop I get). The template was then cut with a jig saw and planed to get smooth edges. Next I marked the eye bolt holes using a hammer against the hardboard and the mounting hole. The centre was then marked and drilled using a 6mm bit. After checking the holes were in the right place, I drilled them out to 22mm using a step drill. The hole needs to be big enough to clear the shoulder of the eye bolt.

Template cut and eye bolt holes drilled

Finally I put the eye bolts in place finger tight to check they were clear of the hole sides.

Final template with eye bolts in place

I have allowed a 5mm gap between the deflector and the body. This will allow the pressure inside the cabin to be equalised.

Material

Laminated glass - this option was beyond my capabilities to work with. It would need to be laminated to avoid it shattering if hit by a stone. Glass is expensive, not easy to cut or drill and is also quite heavy. So this was ruled out.

Perspex - easy to cut and drill. Cheap to buy and widely available. Loses transparency over time, can warp when exposed to UV light and can break in to large shards if hit by a stone. So this too was not an option for an open sports car with no top.

Acrylic sheet - easy to cut and drill. Stable dimensionally, to UV light and stays clear. It has greater break resistance than glass. On impact it breaks in to relatively large pieces, rather than small pieces or shards. Withstands large changes in temperature. Lightweight. Better transparency than glass. Expensive and harder to source.

Solid polycarbonate - similar properties and strength to acrylic sheet. Easier to source and less expensive than Acrylic.

So polycarbonate it was. I have ordered 8mm thick which by all accounts is about right. Any thinner and I risked it vibrating or flexing at speed. Any thicker and it is over doing things. The size of the polycarbonate sheet ordered is 1220mm x 360mm. Prices seem to vary quite alot over time (oil prices?), but Century Plastics in Sheffield seemed to have the best price at around £30 including VAT and carriage and their service is great.

My next post will be cutting, drilling and fitting the deflector.

Roll over hoops - part 5 - The Final Fix!

I have not done anything for the past couple of weeks. The last job I did was to drill the roll over hoop holes in the body and loosely fit the bars. So now I needed to check the fit to the chassis, then fill the hoops with expanding foam, before the final panel body trim, the fitting of the grommets and the escutcheons.

The hoops were removed and the studs (I think that bolts are used on the GDJAG) fitted to the outer legs, after applying some grease (note that the shorter thread went into the roll over bar).

The hoops were fed through the holes in the body and the boot floor. Next the nuts were loosely fitted to the outer bar studs, before the other bolts were put in place by hand. A ratchet strap was used to help get the studs/bolts and the bars aligned.

Hoops bolted in to place.

Ratchet strap helped pull the legs in to position.

Once I was happy with the fit, the holes were finally marked up to allow 5mm gap for the grommets to fit into the body top holes and a 3mm gap around the legs in the boot floor to allow some clearance for body to chassis movement. The hoops were taken out and bolts and studs were removed, before the body holes were finished off with the Dremel.

Then it was on to the messy job of filling the hoops with expanding foam. GD recommend this to reduce the noise transmission from the chassis. I used Polyfiller Expanding Foam, but as they say other brands are available! Do use disposable gloves (supplied) as this stuff is not easy to get off your hands if you get it on them.

Each of the escutcheons were drilled in the three places marked for 4mm stainless button head bolts. First I drilled the holes for the 4mm button head bolts in the escutcheons, the grommets and the body. I then put the escutcheons and grommets onto the appropriate legs. The fitting of the grommets onto the legs is not easy! I used Vaseline to help them slide into place on each leg (it is amazing what this stuff can do!). Next I masked around the bottom of each hoop's legs, then I sprayed water into the legs to help cure the foam. I then squirted foam into each leg of the hoops (after putting on the gloves!) and quickly inserted the bolts/studs into the holes to avoid the threads being clogged up. This also makes sure that the foam does not leak out.

Chalk was then rubbed around the six holes in the boot floor. The boot carpet was laid in place and pressed around the holes to leave a chalk imprint on the underside. The carpet was removed and cut in a star pattern within the chalk marked holes. The inner area of the carpet hole was removed to aid fitting.

After the foam was cured, I left it overnight, I finally tightened the studs into the outer legs, using mole grips. Once this was done, the hoop was again put through the holes, then through the carpet into the boot floor holes. The bolts and studs were tightened in place from underneath the car.

Bolts/stud tightened in place

GD say that silicone is not needed as water does not get in through these holes, so I didn't apply any.

The grommets were manoeuvred into place, through the holes in the top of the body. Again a fiddly job. Then the escutcheons were lowered into place and were fixed in place with the 4mm button head bolts and nyloc nuts. 17 of the 18 bolts went through okay, the 18th 'disappeared', probably into a cavity between the matting layers. This hole will need filling and tapping to get the bolt to bite.

Just need to fix the escutcheons.

Inside the boot

Second hoop done and escutcheons fixed in place

The loom was re-clipped into place and the carpet re-fitted to the sides. Then the eye bolts for the harnesses were fitted. To get them in the vertical position, I needed to file a small amount off the hoop mounting points. Grease was applied to the eye bolts to help them go into place.

Eye bolt in hoop

Job done!

Roll over hoops - part 4

A glass of wine and a good night's sleep sorted out the measurement discrepancy. It was simply that I had measured the body surface and this was curved. So it was similar to having a triangle and the sloping side was longer! Once I put a level and measure on I saw that the holes were in the right place. Phew!

So I was raring to go. I cut out the remaining big hole (50 mm to start with), then made sure that the hoops fitted. They did.

Bars fitted back to front to check hole spacing

Using the plumb line, I marked the underside of the deck and drilled a pilot hole upwards. I then cut out the smaller hole (40mm to start with) for the third leg from the top of the deck. I tried to open up thehoop legs so that the holes were 304mm apart using a hydraulic jack , but that did not work. They sprung back.

Trying to spread the bar legs

After opening up the holes a little, I fed the roll over hoop into the holes, then removed it and adjusted the holes again with the Dremel. This was a bit like doing the hokey cokey, in out, in out .... until it was right, opening up the hole by a small amount each time until the legs of the hoop seated on the mounting points of the chassis.

One bar done

Then it was on to the next one. A repeat of the first hoop.

Both bars/hoops fitted

The rear legs needed a bit of springing to get them in the holes, but an easy job. So the main holes were cut and the bars fitted. Done!

Now the hole needed opening up to allow a 5mm gap around each leg of the bar for the grommets. To make sure this was a perfectly round hole I marked it using a pencil and the inside of a washer.

Hole marked up to allow 5mm gap around hoop leg

One very happy Cobra builder. Next I will aim to fit hoops with the grommets and escutcheons.

Roll over hoops - part 3

It was time to drill the hole for the third leg of each hoop in the boot floor and start to drill the holes in the deck on the body!

First I applied masking tape to the area behind the seats (the deck), to avoid any drill marks, should I slip. The saddles were then fixed with the loosely fitted nuts and bolts, where the wishbones are fixed to the chassis rear most mounting point. Once in place the holes were marked from underneath. I marked the outer edges of the saddles and the hole centre lines. After moving the saddles, I then then marked the hole centres and drilled a pilot hole. Not a lot of space to do this! Once the holes were drilled, the saddles were moved out of the way - they can be rotated on the bolts. Each hole was then opened out with a hole saw from within the boot making sure that the mounting hole was central.

Third hole drilled in boot floor. Bolt helps see if it is centred.

Next a plumb line was used to mark the point to drill under the deck. The plumb line gave a vertical reference to the hole centre. To do this I had to climb into the boot, so that I could see the lower hole and mark the underside of the deck, to get a centre to drill a pilot hole. Using the 90deg attachment for my drill I made a small hole upwards. This was then checked with the plumb line to make sure it was were I thought! Slight adjustments were made to the holes.

Plumb line through top hole

Checked holes were in line

Final check that mounting point lined up. You can see that the hole centre is slightly off

Next, out came the bigger hole cutter. I used a spirit level on the drill to make sure that I drilled straight down. Using the pilot hole I drilled from the outside of the rear deck into the boot. This was repeated at the other side. One leg of the roll over hoop was then offered through the hole to make sure it fit.

First leg in place

Both outer holes drilled and roll over bars inserted back to front

At this point I wanted to check that I could secure the legs in place. However, the bolts supplied would not go in through the outside holes due to the shock absorber mounting points. A quick call to the factory and I was advised that a stud was used to secure it to the chassis. The wrong bolts had been packed by a former employee and not checked before they went out. The threaded section of the bolts are not long enough to cut down, so studs and nuts will be sent from the factory!

So not to be beaten, I marked and drilled a second hole for the nearside bar (the bars are supposed to be 304mm centres - they were not - one was 306mm and the other 300mm). These can be sprung apart with a wooden block/jack or pulled together with ratchet straps. With a small amount of trimming the two legs of the nearside roll over hoop went through to the chassis and on to its mounting points.

Nearside bar in its reversed position. Just the third hole to drill here.

The two legs within the boot

Then I marked and drilled the pilot hole for the off side hoop's second leg. Curiously this was 10mm wider than the roll over hoop fitting centres (the centres were 300mm wide), so at this point I went inside and got a glass of wine and tried to work out why! Tomorrow may bring a solution!

Roll over hoops - part 2

The hole at the other side of the car (nearside) was drilled, like the first and opened out..

Two holes drilled

A straight line was marked across the boot of the car, using a straight edge. Bolts in the two holes were used to position of the line.  The hole centres were marked 304mm (12 inch) apart, from each inner hole centre. The loom needed to be unclipped on the nearside and the carpets pulled back. A small screw driver helped check that the holes were lined up with the mounting points. Once I was sure that the hole centres lined up, they were opened out to 55mm (the bars are 51mm) to allow the roll over bar legs to go through.

Two bolts used to check the hole centres

So all four big holes drilled in the boot floor. May need to open them up a little more, but that is for another day if required!

Four holes drilled, centred and opened out

So, steady progress. The two holes for the third legs will have to wait.

Roll over hoops - part 1

Seats

Couldn't resist putting the seats in the car to see what they looked like!

Really happy with the look!

Had to cut the carpet out from around the handbrake bracket, then bend the bracket a little to gain clearance with the drivers seat.

Setting up the car

Next I levelled the car on axle stands. The chassis is the thing that is set to the level, not the body. It needs to be level side to side and back to front. This took hours!

Front wheels

Whilst it was up on the axle stands, I checked whether the front wheels, when on full lock, touched the inner wings. They did! So using the Dremel, I dressed the lip on the inner wing back a little to create some clearance. This was required at the front and back of the front wheels.

Small area removed from inner wing to allow tyre clearance

Roll over hoops

Now to the butt nipping bit! I have been putting this one off, but the time has come when I can't do this any longer.

The items involved in fixing the roll over bars are the two stainless steel hoops, the saddles/brackets and the fixings. These differ from the GDJAG to the Euro, in that the fixing points have different spacing. So unlike me, do not assume that a template from a JAG will fit. It won't. You will need to make your own template if you can't blag one (not that I really needed one)!

Roll over bars, saddles and bolts

The saddles/brackets are made of steel and needed to be painted before fitting. I used Hammerite satin black spray.

Levelling up the chassis was important as it will allow the plumb bob to line up with the mounting vertically. The rear half of the chassis was the most important as this is where the bars are mounted. Finding flat areas of the chassis to check the level, however, was a challenge!

Now to some real work. A 5mm hole was drilled up through the inner front mounting point of the chassis into the boot floor. I used a 90 degree chuck adapter for the drill and plenty of dexterity to get the drill in place around the suspension! Why has no one invented a bendy drill? Next I made an undersized hole (about 40mm) with a hole saw. Finally I marked a circle using the mounting hole as a centre point and opened it up with the Dremel. I then made sure that the mounting point was in the centre of the new large hole. It was, phew!

Hole with chassis mounting point below

First hole in [place with bolt designating the centre of the hole

The other holes will wait until I am fresh to the job. So now for some wine and a feet up!