General Gapping Questions

[JackW]

Hi Everyone

I have what might eb a series of obvious and silly questions but as I don't know I will ask anyway. I read Dean Lampe's thread and he was saying he was going to send his fantastic looking car back to the body shop to improve the gaps. It got me thinking and now I have a number of gap questions.

1. What constititutes a good gapping job? I would have thought that it was fairly even spacing across all the body panels but if there is more to it I would love to know

2. How hard is it to align the gaps? I know that some people spend ages on this makign them look as perfect as possible but surely it is just a case of lining up the panels then attaching them in place. Or maybe this is all there is to it but it is much easier said than done.

3. At what stage of the build would you normally attack this task? Do you build all the plumbing and wiring etc and then fit the body panles, or do you fit the body panels, get the gaps right, mark it all off, then remove them and do the other work, or is there some other order of sequence that this is done in.

Guys there is no rush to respond to this question because I am not at this point actually building a car but I would certainly love to know more about this topic. Obviously a well gapped car looks the business whilst a badly done job looks nasty.

Regards

Jack

 

[Cliff Beer]

Jack,

Good questions. This is a topic which is near and dear to my heart - I really notice such things and have always endeavored to have the gaps as perfect as possible on all my cars regardless of whether it's a built car or a restored car or even a new car.

Some things I have learned over time:

1. Fitting of body panels is best done as a preliminary to any body or paint work. It can be tough to go back and get a good fit when the paint is done. This seems obvious and very basic to me but suprisingly it seems to be lost of some folks, even some who are involved in the body business.

2. Proper fitment of body panels doesn't typically depend on having wiring and plumbing previously completed. There are exceptions where holes may need to be cut (and the edge finished) or something similar.

3. A good fit depends on alignment in each of the axis. Said another way, it's not just the gap that counts, it's also the alignment of the surface plane of the panel. This becomes particularly interesting where there are compound curves intersected by the panel gap. A very basic test to try in this regard is to run your hand across the panels and the gap - if you feel an "edge" so to speak which stands proud at the gap then there is some further fitment to do. Often it is best to align panels with a helper so that they can hold the weight of the panel (a door, for example) as adjustments are being made by you. This makes it easier to make fine adjustments.

4. Try to move the panel in only one plane at a time. In other words, don't try to adjust the panel in the X, Y and Z planes at the same time because typically adjustment in one plane is about all that can be precisely monitored and adjusted for.

5. Mark your starting point. For example, with a door adjustment, mark the position of the hinges on the adjustment backing plate. This helps you to guage how large or small the adjustments are that you're making. I use a black felt pen as this leaves a mark which can be removed with alcohol later.

6. Be patient.

7. Remove locking devices. If the locking devices are removed (door locks, for example) then the panel can be adjusted without the locking device affecting the position. Once the panel position/fit is correct, then re-install locking devices in the proper positioin and in such a way as to not change the correct panel alignment.

8. Finally, if you don't want to get down to using filler (bondo or lead) to improve the gaps (because you don't want to have to repaint a panel or the whole car) then split the difference. Said another way, make a compromise on the gaps (front and back edge of a door panel, for example) that looks as consistent as possible.

9. Not all gaps are necessarily the same. Depending on how a panel moves/opens, more or less clearance may be necessary - doors v. front/rear clamshell.

10. You'll often need to make some shims. Using washers of different thickness (a common less-than-perfect technique) isn't desirable because the surface area in contact with the mounting plate isn't that great. You can buy some aluminum sheet (easily cut) in different thickness and cut it easily into proper shaped shims.

Persist and be patient and you can get the gaps looking very good! Hope this is helpful.