Fabricating a rear spoiler
Discussion
Hi, I was hoping somebody could help me 
I would like to make my own rear spoiler 
Its to be a sort of ducktail, similar to the one on the Beautiful Ferrari P4, but I am strugling with what material I should use to make the initial mold from, and where to obtain it 
I tried using a builders expanding foam 
and I am still trying to pick all the bits of hardened foam out of the dogs hair, my hands, my hair, the work bench this stuff sticks like S***T to a blanket 
what are you supposed to contain it in, to make the basic shape, its to be approx 74 inches long, stick up about 5 inches along the rear of the car, then drop down the back of the wheel arch 7 inches, but the whole thing is only to be about 1/4 inch thick, anyway, now appealing for help / suggestions, please 
I would like to make my own rear spoiler Its to be a sort of ducktail, similar to the one on the Beautiful Ferrari P4, but I am strugling with what material I should use to make the initial mold from, and where to obtain it I tried using a builders expanding foam and I am still trying to pick all the bits of hardened foam out of the dogs hair, my hands, my hair, the work bench this stuff sticks like S***T to a blanket what are you supposed to contain it in, to make the basic shape, its to be approx 74 inches long, stick up about 5 inches along the rear of the car, then drop down the back of the wheel arch 7 inches, but the whole thing is only to be about 1/4 inch thick, anyway, now appealing for help / suggestions, please There are some decent books for fibreglass work available, these should be a decent start:
www.amazon.co.uk/Competition-Car-Composites-Practical-Haynes/dp/1859606245
www.amazon.co.uk/Fiberglass-Composite-Materials-Forbes-Aird/dp/1557882398
Supplies should be available from:
www.cfsnet.co.uk/
I haven't done any hands on construction like this but I'd imagine a typical process would be as follows (book would confirm)
1. Construct pattern from foam - modelling foam would probably work (not sure what density) or you could cast a block of foam using a MDF bathtub type construction, but remember that the foam will expand greatly so ensure pressure isn't going to build up and destroy your "mould"!! you'll then need to shape this how you want it, and probably seal/paint it in some way. Remember, the surface quality you get on the pattern determines the quality of the final component!
2. Take a GRP mould from the pattern (2/3/More parts depending on complexity!), remember to use some form of mould release agent to ensure the grp doesn't stick to the pattern!
3. Take GRP component from the mould.
There are a lot of areas where you could experience difficulty unless you are clear of the processes so I would recommend doing as much reading as possible to help you get the best quality component at the end!
Have fun & post some pics up as you go along so we can all see how you are getting on!
www.amazon.co.uk/Competition-Car-Composites-Practical-Haynes/dp/1859606245
www.amazon.co.uk/Fiberglass-Composite-Materials-Forbes-Aird/dp/1557882398
Supplies should be available from:
www.cfsnet.co.uk/
I haven't done any hands on construction like this but I'd imagine a typical process would be as follows (book would confirm)
1. Construct pattern from foam - modelling foam would probably work (not sure what density) or you could cast a block of foam using a MDF bathtub type construction, but remember that the foam will expand greatly so ensure pressure isn't going to build up and destroy your "mould"!! you'll then need to shape this how you want it, and probably seal/paint it in some way. Remember, the surface quality you get on the pattern determines the quality of the final component!
2. Take a GRP mould from the pattern (2/3/More parts depending on complexity!), remember to use some form of mould release agent to ensure the grp doesn't stick to the pattern!
3. Take GRP component from the mould.
There are a lot of areas where you could experience difficulty unless you are clear of the processes so I would recommend doing as much reading as possible to help you get the best quality component at the end!
Have fun & post some pics up as you go along so we can all see how you are getting on!
I can't see casting your own foam blocks ever working. You can get 4" insulating foam in 8'x4' sheets, glue them together if you need more thickness? Not quite sure what material it is, not expanded polystyrene, it's harder and got a yellow tinge to it. If that isn't good enough then I suggest you contact a plastic wholesaler and see what they can suggest. Maybe you can even get hold of the stuff they make surf boards from?
If the finished item is to be an integral part of the rear clip and only 1/4" thick then I would start by making a polystyrene block which fits completely the rear contours of the car and has the shape of the underside of the spoiler crafted into it but wider and taller than the finished spoiler. Cover this in thin material like bed sheet using white wood glue. This is now the mould for the core of the spoiler. If required corrections can be made using filler. Prepare it with some sort of release agent which may be no more technical than clingfilm. Prepare how you are going to secure the mould to the back of the car. Gaffer tape would seem the most likely candidate.
Prepare the area the spoiler will bond too so you have a good key. This needs to be both the back and the top of the existing boot lip. Cut a strip of glass woven cloth as wide as required and as deep as the spoiler and the bonding area on the back of the boot. Lay the cloth out on a sheet of polythene. Wet the bonding area on the back of the car only (not the top) wet the glass cloth. Drape the cloth over the boot lip with the right amount hanging down the back bonding area and stipple the cloth onto the bonding area. Now place the mould in position trapping the cloth between the mould and the back of the car.
The cloth currently draped over the top of the boot can now be pulled up and onto the mould ensuring you stipple out all the air bubbles.
This has now formed the shape of the spoiler underside. Its finish is not important as that will be corrected with filler. You can now either wait until this has cured or carry on laying up the required spoiler thickness and its bonding to the top of the boot.
When cured remove the mould and get in there with a sander reducing the oversize spoiler down to the size and shape required. Finish with filler.
Enjoy
Steve
Prepare the area the spoiler will bond too so you have a good key. This needs to be both the back and the top of the existing boot lip. Cut a strip of glass woven cloth as wide as required and as deep as the spoiler and the bonding area on the back of the boot. Lay the cloth out on a sheet of polythene. Wet the bonding area on the back of the car only (not the top) wet the glass cloth. Drape the cloth over the boot lip with the right amount hanging down the back bonding area and stipple the cloth onto the bonding area. Now place the mould in position trapping the cloth between the mould and the back of the car.
The cloth currently draped over the top of the boot can now be pulled up and onto the mould ensuring you stipple out all the air bubbles.
This has now formed the shape of the spoiler underside. Its finish is not important as that will be corrected with filler. You can now either wait until this has cured or carry on laying up the required spoiler thickness and its bonding to the top of the boot.
When cured remove the mould and get in there with a sander reducing the oversize spoiler down to the size and shape required. Finish with filler.
Enjoy
Steve
Genuine fullsize ultralight aeroplane wings are made of foam.
You use a hot wire and a template to create the shape, but you could just as easily use a surform and sandpaper, to get the shape that you want. Then you just seal the thing up in glass fibre layups (cloth), using epoxy resin to bond the glass fibre cloth in place.
When finished, the strength is phenomenal.
Composite Construction
You use a hot wire and a template to create the shape, but you could just as easily use a surform and sandpaper, to get the shape that you want. Then you just seal the thing up in glass fibre layups (cloth), using epoxy resin to bond the glass fibre cloth in place.
When finished, the strength is phenomenal.
Composite Construction
Edited by dilbert on Sunday 10th December 21:59
The stuff you want is polyurethane foam, which you can buy in sheets from companies who sell GRP moulding products and is like a denser version of the stuff you got in the can.
Very light and very strong, it's widely used in composite moulding sandwiched between two layers of GRP to stiffen things up. Got some in my Quantum.
Also used by companies like TVR who basically stick lots of sheets together to form a big block and then attack it with surforms etc to get the shape they want. If you're really good you end up with a Griffith.
Was often used by the custom car crowd to make one-off spoilers in the 1970s. Make the basic shape from the foam, glue to car, cover in fibreglass and filler then sand smooth. Easy!
Very light and very strong, it's widely used in composite moulding sandwiched between two layers of GRP to stiffen things up. Got some in my Quantum.
Also used by companies like TVR who basically stick lots of sheets together to form a big block and then attack it with surforms etc to get the shape they want. If you're really good you end up with a Griffith.
Was often used by the custom car crowd to make one-off spoilers in the 1970s. Make the basic shape from the foam, glue to car, cover in fibreglass and filler then sand smooth. Easy!
Gassing Station | Bodywork & Detailing | Top of Page | What's New | My Stuff