Still plugging away...

Progress is starting to pick up. Here are some of the bodywork/composite mini-projects underway.

Dents and Recesses

I've always liked the appearance when car badges sit inside a recess rather than being slapped on a flat surface, and I've always liked the Aston Martin wing badge, so I've gone to a lot of trouble to make wing-shaped dents in the bodywork. 

Step One was making a CAD model and 3d printing the reverse of what I wanted - a wing shaped bulge to use as a plug (in my hand, above). These have to be finished quite smooth, waxed, and sprayed with PVA so that the composite resin won't stick to them. Then I cut a hole in the bodywork and mounted the plug in place. I used latex caulk to form a vacuum seal around the edges of the plug - only necessary if you plan to vacuum bag the part.

I used glass microspheres and epoxy resin to make filler paste (above). It's hard to get composites to form neatly into nooks, crannies, or corners, so sometimes it's helpful to lay down some filler into the spots that may be difficult to fill out (below). I had already painted on 3 or 4 layers of white gel coat before I started with the filler.

Above: filling in the edges of the mold. In this picture you can see I have already ground a chamfer into the inside of the fiberglass. I did not take a picture, but before laying up the composite I used a grinder to rough up the inside surface of the fiberglass

Above: I started the layup with a light layer of epoxy resin, then a layer of fine fiberglass cloth, then several layers of chopped strand fiberglass matt - some of it cut to fit in to the low areas - then a layer of medium fiberglass cloth.  I wet each layer with epoxy resin before adding the next layer. The last layer of chopped strand and the final layer of cloth extend well beyond the original edges of the hole. 

Then I put down a layer of peel-ply (which doesn't stick) then a layer of resin flow (the red net-like material) then a layer of vacuum breather (the fluffy white stuff). Then I used double sided tape to seal clear plastic over all of that, then attached the vacuum line and turned on the pump. This draws all the layers of the composite tightly together and removes the excess resin.

The vacuum pump and vacuum bagging materials are courtesy of Pops Racer, who had them laying around unused in the shop and was kind enough to donate them for this project.

Above: after about 24 hours curing time, I peeled the plug off from the outside. I used white gel coat so it looks separate from the gray bodywork, but you can't actually feel the joint. This is a smooth outer body surface with a wing-shaped dent in it... success! There are some screw holes I will need to fill (screws used to hold the mold in place) but that will not be a problem. This will all look seamless when painted.

Similar process for the fuel cap recess, except I wasn't able to get the vacuum to seal properly on the curved inner surface of the fender. Even without the vacuum, the peel ply, resin flow, and vacuum breather really helped me to manually compress the layup together without making a huge mess. Above is the layup from the inside. The yellow is a layer of Kevlar, which is a nightmare to cut, but adds a lot of strength to the layup. I figured the fuel cap and filler hose will put some stress on this area and it will be good for this to be extra strong.

Here's the fuel cap recess seen from the outside. There is a good deal of caulking to clean up and I will need to use a body saw to cut the hole for the fuel filler cap. The greenish-looking stuff is PVA, the mold release agent that (along with the wax) allows the mold to be removed instead of becoming a permanent part of the layup. This washes off easily.

I am quite pleased with how this turned out also.

Also Underway...

I have been working on a license plate nook. The Replicar bodywork is set up for long skinny UK plates, and doesn't really work for US plates. Below: I used CAD and 3d printing to create the desired shape of the recess. Then cut out a hole for the 3d print and bonded it in place. There was a nontrivial amount of filling and sanding and priming and still more sanding to get this to the needed level of finish. Then I waxed it and sprayed on PVA, and took this picture:

If orientation is challenging, note that the bodywork is sitting in my garage upside down for these steps. Subsequent the picture above, I painted on a few layers of gel coat and used the resin-with-microspheres filler to fill in the corners of the recess. Then I will lay up fiberglass to create a mold, then cut this part out of the bodywork, and lay up new fiberglass. A natural question is why, having reached this step, do I need to make a mold and lay new fiberglass? Don't I already have the shape I want? Well, yes, I do have the shape I want... but not the strength I need. This is just a 3d print held in place with epoxy glue and bondo. A few flexes of the bodywork and cracks would appear around the join. By laying in new fiberglass, the added shape can be as strong or stronger than the original bodywork.

Also not pictured, there is a smaller wing-shaped recess in the rear bodywork just around the corner from the picture above. 

Update 1

I finished the layup on the license plate recess above and pulled the mold this morning.

I got a few cracks in the gelcoat when I pulled the mold. It's always a question whether to do some filler/primer/sanding to clean up a not-quite perfect mold, or whether to repeat and try to pull another mold. I have never yet gotten a mold to come off perfect - there's always at least a little bit of cleanup for me, at least.

Above: the yellow material is Kevlar cloth - the same stuff they use to make body armor. Using this was a tip from my father, who recommends a layer of Kevlar anywhere one is using fasteners on fiberglass because it doesn't take much of a stress point to crack the gelcoat/paint layer - not an attractive look. 

Totally unscientific, but I was impressed with how strong the layup for the fuel filler cap turned out. Or at least the impression of strength it gives. The Kevlar has that quality where you rap it with your knuckles and it sounds and feels like it's going to be indestructible.

An entire roll of Kevlar is WAY more than I need for my bolt points, latches, and hinges, so I decided to throw a layer down wherever I have cut into the bodywork. Most of this is probably unnecessary, but I've got plenty of Kevlar so why not use it? Newbie tip: get the special scissors for cutting Kevlar. They're about $25 on Amazon and would be a bargain at twice the price. Without them, cutting Kevlar was an exercise in frustration.