Metal thickness also determines whether the panel will be dented. Testing and observations have shown that the threshold size for hail to dent a steel vehicle body panel is hard ice one inch in diameter. Softer aluminum panels and bright metal trim material may be dented by hard ice that is one-half inch in diameter.

Hail that impacts a metal vehicle panel produces a dent that is conical in shape and has shallow sides. The center of the dent usually sustains a slight crease and no loss of paint. With paint intact, most dents can be removed without painting the vehicle. Thus, hail-caused dents can be removed by having the vehicle repaired at a business that does paintless dent removal.

Because hailstones fall randomly and, generally, are wind-driven, impact marks will be distributed randomly on exposed surfaces, usually striking from one direction, that of the storm. The windward side of a vehicle will sustain greater damage than those panels protected by the other vehicle sides, buildings, or adjacent automobiles. Any vehicle panels elevated above nearby protection (neighboring objects, such as other cars or fences) and on the windward side will sustain greater impact and damage. All exposed surfaces will be impacted including the softer, more-easily damaged components of vehicles, such as bright trim.

Historical Research

The first step in assessing vehicle damage is to obtain background information from the owner as to when and where the vehicle was located at the time it was impacted. Obtain weather records for the incident time and location, including publicly reported facts about hail size and storm direction, and assess the vehicle damage in light of that information.

If possible, inspect the vehicle at the incident location to confirm whether any environmental factors such as trees, buildings, or other obstructions could have shielded the vehicle and affected the distribution of the dents. For identification purposes, document the vehicle's make, model, color, vehicle identification number, license plate number, mileage, and date of manufacture. Also record its exterior characteristics, such as composite or aluminum body panels and other critical trim pieces.

Before inspecting for hail damage, be sure that the vehicle's surface is clean. If the vehicle is not clean, it must be washed to ensure that all dents are observed and that the subtle details of each dent will not be obscured. Closely examine each dent panel-by-panel, and number and list its characteristics. Look for the presence of creases or scratches and whether these impacts have a half moon shape, round bottom, and consistent size, as well as any other distinguishing characteristics. Mark dents with contrasting-colored tape placed adjacent to the dent, using various colors to differentiate types of dents, e.g., blue for dents with typical creases, white for dents with scratches in the dent center.

Dents that are caused by natural hail will vary in size, have shallow bottoms, and have very light creases across their widths. A hail-caused dent will not exhibit a scratch in its center, will be randomly located on a panel, and will not be arranged in a pattern in relation to other dents. Natural hail is relatively soft and, typically, does not harm paint.

On the other hand, intentional, mechanically caused dents often are created with metal tools that tend to be much harder than natural hail. As a result, marks made by metal tools generally are uniform in size with sharp, crescent-shaped creases, accompanied by scratches in the paint. When evaluating the dents on each panel, be aware that door-dings, scratches, and pebble-chips, all from normal wear, are considered unintentional mechanical damage. These imperfections are easily identified and typically exist where hail dents would not occur. A small amount of unintentional damage is to be expected, especially with older vehicles.

Next, step back and examine and evaluate the dents (now indicated by pieces of tape) on each panel to determine if the distribution is random or if there are patterns to the dents such as circles, triangles, arcs, or straight lines. Multiple dents in patterns, or non-random dent distributions, indicate intentional, mechanically caused damage.

Finally, the entire vehicle must be examined to evaluate the overall dent distribution. A greater number of dents on flat panels and a few dents on one side of the vehicle are typical of the wind-blown characteristics of hail damage. The distribution of the dents will be directional, and dents usually will not be present on all panels of the vehicle. A few dents or no dents on flat panels and numerous dents on all side panels are common characteristics of intentional mechanical damage.

To document the damage, photograph the vehicle with the tape attached. Take general photographs of the vehicle and close-ups of each panel. Take several close-ups of dents to show any non-typical characteristics, such as scratches in the paint, sharp creases, or deep dents. Sometimes, close-up examination of a scratch in the dent center can lead to identification of the tool used to make the dent.

After evaluating the characteristics of each dent, the distribution of dents on each panel, the overall distribution of dents on the vehicle, and the weather data, the true cause of the dents may be assessed: hail-caused or mechanically generated.

Robert N. Fleishmann is a licensed Professional Engineer with Haag Engineering Co.