Fender Fabrication - an ongoing saga.....

As suggested previously, applying foam to the OE steel fenders really is not that difficult - messy yes, difficult no.  The trick of course is in the shaping.  When I started the right front fender I did not have the tire/wheel mounted.  What was probably a bigger mistake was that I did not have the ride height, rake, toe, camber etc., even roughly set.  When I sent the car in to Hamlin Fabrication to have the new nose installed, the rear clip installed, roll cage repaired, and dash support/steering re-done, I had this done as well.  Of course it will get tweaked again once the car is running, but for a first guess it is pretty good.  Once ALPINA supplied me with the host of photo's, I was able to spend more time reviewing them from various angles which ultimately helped me with some of the details.

When the foam is applied it expands nearly 10:1 so what you get is sort of a "blob".  From there I used a combination of hack saw blade, bread knife (don't laugh it works great), sure form file and various grits of sand paper (.40-.80 grit).  Once the foam is dimensionally where you want it to be and is as smooth and even on all surfaces as you can get, the next step is to coat it with a combination of polyester finishing resin, micro spheres and cabo-sil.  The micro spheres help in the sanding of the resin (as well as thicken it somewhat), and the cabo-sil thickens the resin more and acts as a hardener.  The thickening properties of the cabo-sil are more important than the hardening.  Basically you are trying to get the consistancy of thinned out body filler. The combination of these materials over the foam creates a "shell" and locks in the outer surface.  From this point the outer surface is sanded smooth.  There still will be inconsistencies in the finish at this point so this is when you start with the seemingly never ending process of applying body filler.

This is some "re-work" I did on the left side fender, you can see how the foam expands.

Now it has been shaped (or re-shaped I should say)

Here is a look at what the finishing resin looks like after being applied over the top of the foam.

Early work on the right side fender.......

So now you have seen some of what didn't work out in reconstructing the ALPINA 2002 Grp. 2 front fenders.  As previously mentioned, these fenders (wings) were totally unique.  As I have found out (the hard way) pretty complex shapes.  I spent a lot of time studying photo's to get them where they are today, which I believe to be as close to the original as possible.  I would certainly be broke if I had needed to do this for a living.  Of course now with the benefit of this experience it will be much easier to construct the rear flares as well as the front spoiler.  First things first.  I didn't take any photo's of the form work I did in "foaming" up the fender.  Basically what I did was build approximately 4" high form around the entire perimter of the steel fender. After that I filled the form with 2lb expanding foam.  From there I started to shape the fender. Here are some of those pictures.

I cut the steel of the OE fender in the basic shape of the sculpted ALPINA fender.  This is actually a rear tire/wheel as I had not had the front tires/wheels mounted yet.

Here you can see that I have done a lot of shaping of the foam to get to this point. I used a serrated bread knife, shure form file, and .40 grit sand paper to get to this point.

Another look from a different angle.

Now I have the correct front tire/wheel on so that I can make sure that the fender is wide enough. When ALPINA raced the car they used DUNLOP racing tyres which are no longer available. The only tire that is still available in the correct size is manufactured by AVON. This is a 11.0x23.5x15 AVON racing tyre.

Mold work and some more early mistakes

I found these pictures the other day - this was some more of my early work.  My thought at this time was that I would make balsa wood bulkheads and "stringers" (stringers as in horizontal supports - from my model airplane days).  I figured by making the bulkheads it would be easier for me to make duplicates and thereby be able to create a mirror image on the left side.  I figured I would fill the voids with expandable foam and then carve the foam off to the edges of the balsa bulkhead/stringers......it didn't work.

The front piece is actually .75oz glass matt with polyester resin. I did end up using this as part of the form when I switched to the foam method.

A little about mold making.......

I don't consider myself to be an expert in this by any means as there are a lot of folks out there that do this for a living. I decided to attempt to make the "plugs" which are essentially the forms from which molds are made.  The plug simply put is and exact replica of the part itself.  After the "plug" is made, then the mold is made off of the plug and then the part made from the mold.  I thought I would take a shot at making the plugs for the car since I had the most information in terms of pictures etc., from which to work.  I decided to start with the right/left front fenders.  The worst I figured is that I would fail and then have to pay someone to make them.  Initially I only had a few pictures from which to work, none of which had very clear resolution -this made things difficult as I had to really guess at a number of different features.  I had actually foamed up the first fender and had started to shape it before I received the photo's from ALPINA.  This was mistake #1.  Mistake #2 was again rushing ahead with out the front tires mounted on the wheels, and part of mistake #2 was not having the ride height and rake set for the car.  Ultimately these mistakes cost a lot of time and a fair amount of money (more time than money though).  There is a lot of great information available on mold making and working with GRP on the internet.  I purchased a copy of "Competition Car Composites" by Simon McBeath which has been an invaluable resource to me - easy to read and understand.

The following are some of the early work done on the right front fender.

This is the 13"x15" rear tire on the front, I had not mounted the front wheels yet which are 11"x15" ALPINA 3-Piece Racing.

Wheel only.

Another angle.

Basically what is done is a perimeter is made around the fender - basically making the surface more or less a bath tub. From there, 2lb polyester expanding foam is poured onto the fender. The foam expands to as much as 10x, hardens off and then is carved to the rough shape.

More in the next update......

ALPINA-BMW Grp. 2 "Wings" (Fenders)

The fender flares (or "wings") as they are referred to for the BMW-ALPINA Grp. 2 race car were for lack of a better term (one-of-a-kind).  Up until 1973 the ALPINA style "bubble flare" or "pig cheek" as some refer to it was pretty common place with most bmw race cars/teams.  While I am not familiar with the rules for that particular period, it is well known that one could fit a wheel of approximately 9" maximum (rear) within the confines of that type wing.  After 1973 a number of different type of "wings" became more evident.  The most common was the SCHNITZER boxed flare which allowed for up to a 13" diameter rear wheel (SCHNITZER was using a 13"x13" rear wheel in 1974).  GS Tuning had a similar flare to the SCHNITZER - very close in looks with minor differences.  Then there was ALPINA.  The front/rear wings on the 1974/1975 ALPINA Grp. 2 car were completely different.  First, the ALPINA car utilized 15" diameter wheels - the first to do so - reason being was that one could fit a larger braking system within the confines of the wheel. The rear wheels on the ALPINA car are 13"x15" and the fronts are 11"x15" (they are massive). 

They are very unique in that in 1974 they had a sculpted or squared off inner arch - some say that it was to emulate the "A" in ALPINA.  I won't argue, it makes sense to me.  I have to say the look has really grown on me - Iike it a lot. In 1975, the livery of the car was changed to the Black color with the more typical of the era blue/green ALPINA deko stripes.  While I have few photo's of the car from that period, what I can tell is that it appears that ALPINA changed the front inner arch to a rounded arch, but left the rear squared off (why I don't know).

Fast forwarding to today, at some point in its long distant past, the original "wings" were discarded and new Gruppe 5 style wings were installed (see my other blogs for pictures of this).  The molds for the fenders were long since destroyed so what that means is making new plugs/molds/parts from pictures.  I decided to engage in this work myself - it has been an interesting and rewarding process so far, although I still have a long way to go.

These are some of my really early attempts,when I was just starting to figure out what things looked like.  I hadn't received a dozen or so digital images from ALPINA as of yet either - these were a huge help.

First, I purchased two used standard BMW 2002 front fenders.  I essentially mocked them up with the wheels to see how much steel I would have to cut from the inner arch, which was cut with an angle grinder.  The following photo's illustrate some of the materials I was fooling with during this process.