[mattz280]

Does anyone here notice that their Z's body panels are not perfectly straight. I mean, if you look at the panels (especially the doors and hatch around the lock) from the right angle in a well lit area the body appears to be slightly "rippled". It's very slight though, you cant see it by looking at the panels from the side or by feeling them. I've noticed this in most Z's I've seen (I hear light colours hide this better). It was really bad on this silver 240 I saw. I've also noticed this on an old charger and a chevy (much more so than the Z's). However, most new cars have little or none of this. New Audis/BMW's/Volvos etc. have perfectly straight panels.

Also, fiberglass panels seem to be worse then steel ones.

What causes this? Age, or manufacturing techniques????

Thanks

 

[Unknown User]

A lot of it has to do with manufacturing tolerances. Most 240s when they were new were very straight. Very high end cars usually have a lot more time spent on them before they are painted. The main thing to remember new vrs. old. Most 240s have had 30 years of doors being slammed windows being rolled up and down and who knows how many paint jobs. All this translates to flexing which translates to maybe a "not so straight car".

 

[mattz280]

Yeah, your reasoning makes sense. I notice its more the doors then anything else, which, being slammed all the time get stressed. However, I have new Nissan fenders and they are for the most part straight, but even they are just very slightly rippled near the inspection lids (not that you would notice if you weren't looking for it). The roof seems to be very straight, as does the hood and quarter panels.

 

[spork]

the reason the fiberglass ones seem to be worse than the steel ones is because when fiberglass cures...the heat from the curing process usually tends to slightly ripple the panels.

 

[steve 260z/300zx]

Most cars will suffer this. The antidote is to use a high build primer and block sand the car. This will completely eliminate the problem.

I don't think age has as much to do with it. Obviously panels (like doors) will alter their adjustment over time (i.e. seals wear or dry out, weight on a worn hinge bushing, etc). This will mostly just affect the gap between panels and they can be re-adjusted. From factory these gaps were OK, nothing special, not much better or worse than any other car from the period (ever seen a 50's Ford truck?). New cars (especially BMW's and other high-end vehicles) have extremely precise close fitting panels from factory.

 

[escanlon]

If you are referring to the overall look of a given body line along several panels, this is due to manufacturing sheet metal parts.

If you are talking ripples along a body line in a single panel, then that is indicative of a poor body repair at some time, or shrinkage of the repair material (bondo or primer).

When sheet metal is bent to form the skin of the door, fender or rear panel, it is usually a cold form press that forces the metal into shape. This method transfers the shape of the mold into the sheet metal via deformation of the metal and stresses the alignment of the metal molecules. This imparts added strength to the sheet metal thus formed as compared to a hot form process. The problem with this is that when the skin is then, once again, pressed around the frame of the door, or fender frame, or chassis, the original deformation doesn't yield in a uniform manner, and as a result the bend in the metal is not as sharply defined.

Almost all cars with the sheet metal bent around the inner frame work demonstrate this deformation, it actually shows up somewhat as a "bulge" 2-3 inches away from the frame member that continues all the way to the other member.

Look at a car from the side, and down, you'll note that the front and back part of the door, are relatively "straight" , but you can discern a slight bulge outwards by the sheet metal in the center of the door. The fenders and rear quarter panel will also demonstrate the same.

This difference in the surface protrussion can then be seen as mismatched panels or as reported earlier, a ripple.

All the posts above are each right in what they address.

One note, yes the best way to eliminate this and yield a front to back continuously flat / gently curved body is to use a high fill primer and to sand it with a long board. However, care must be taken not to overly fill around door openings, since these are usually lower than the rest of the body panel, it is too easy to leave them thick and then prone to edge chipping and damage.

For what it's worth