Storm Highway by Dan Robinson
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                   Monday, April 13, 2015

Vehicle hail shields for storm chasing: my build & why I'm adding them

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After many years of halfway considering the idea, this spring season I will finally be chasing with a set of hail shields on my car. For the uninitiated, hail guards/shields protect glass windows, mirrors and sometimes headlights/taillights that can be broken by hail as small as golfballs. No company makes or sells hail guards for use while the vehicle is in motion (inflatable covers exist only for parked vehicles), so they must be custom-built. First, I'll list my reasons for choosing to employ hail shields, then I'll go into the specifics of my rig.

The case for hail shields

  1. Supercells produce large hail. Most supercell thunderstorms observed in storm chasing produce at least baseball-sized hail. No further explanation needed on this point!
  2. Hail encounters happen to storm chasers of all experience levels. It is true that accidental encounters with damaging hail are rare, and can be avoided most of the time by a reasonably-experienced storm chaser. But notice that "rare" means "it can still happen". I consider myself lucky to have avoided a truly bad hail encounter in all my years of chasing. I've had a few nervous tangles with large hail, but so far only one that has taken a window. No chaser is immune to a vehicle-totaling hail event, and I have to assume that one day my own luck will run out in that regard.
  3. A multiple-window loss can cost more than a chase season. In 2013, wind-driven 2-inch hail broke my rear window, which cost $500 to replace. A typical outcome when caught in a higher-end baseball/softball hail swath is to lose the windshield, rear window and one or two of the wind-facing side windows. For my car, Safelite's web site quoted $1,434 to replace these windows (before taxes and disposal fees). A truly disastrous hail encounter that broke ALL of the windows (less likely, but still possible) would cost $2,600. For a minivan or SUV, those costs would be much higher depending on the size of the windows. I have heard of one chaser who had $8,000 in window damage on his SUV! In addition to windows, one also needs to consider rainwater damage to equipment and upholstery inside of the vehicle, and the potential for injury from shards of broken glass. Comparatively, the cost of materials of my sheild project is coming in around $300.
  4. I don't claim storm chasing hail damage on my insurance. I have never felt like it is a good idea, much less ethical, to make an insurance claim for a hail-broken window that resulted from storm chasing. At most, I'd think you could do that once without consequence (raised rates or your insurer dropping you). Since that basically makes me self-insured for hail damage, and I don't have a bottomless chase fund, it's up to me and me alone to mitigate the financial risks. A hail shield rig ($300 one-time cost outlay for materials and maybe $100/year in extra fuel expense to prevent $1,500 or more in expenses) seems very practical and sensible to me. If the shield rig saves just my front windshield once, it's paid for itself.
  5. Eliminating the hail concern improves chase positioning possibilities and safety. Now when I say this, I don't mean that I now will intentionally drive into softball-sized hail just for the heck of it. What I do mean is that *if* a situation arises where I *could* encounter large hail, I can proceed with confidence. If you've been chasing for a while, you know exactly what I mean - those situations happen all the time. It could be when driving south through the western/middle part of the forward-flank core of a supercell where some baseballs may be lurking. Or, it could be following behind a tornado with a hail-filled RFD on your tail (think of May 12, 2005 in South Plains, Texas - Google it!). Most importantly, this opens up ALL possible escape routes without the concern for hail damage being a factor of hesitation. If you ever need to bail where softballs may be, you can make that decision quickly and confidently.
To me, the low cost of the hail guards is simply a no-brainer good investment. I don't see them as a license to be reckless, but rather to add a strategic advantage and another layer of safety to my chasing.

Hail Shields/Guards: Basic functions and requirements

Hail shields are very simple rigs to build - they consist only of a frame to hold some kind of heavy-duty wire mesh, screen, grating or grid that can withstand impacts of hailstones up to softball size.

Shield Materials: The preferred material for hail sheilds is heavy wire mesh or wire shelving panels. These are lightweight and can withstand the impact forces of softball-sized hailstones at terminal velocity. Some chasers have used Lexan or plexiglass panels for their shields - though these are generally not preferred due to the fact that they scratch/discolor easily and can break/dislodge with a strong enough wind gust. I chose wire shelving for my shields.

Frame supports: The shields must be supported by frames and/or beams. Welded or bolted steel or aluminum beams (either L or box type) can be used for this purpose. I chose aluminum due to its high strength and low weight.

Vehicle mounts: A roof rack makes for the easiest hail shield rig mount. Some chasers have used high-strength magnets, straps or direct-drilled mounts to the roof, doors and/or body panels. I chose to drill into my car's roof and attach permanent mounting bolts.

Requirements for safety and function: There are several important safety considerations/requirements for vehicle hail shields:

  1. Structural integrity: The shields, hardware, fasteners, mounts and the entire rig itself must be able to withstand the extreme vibrations, g-forces and aerodynamic stresses involved with being mounted on a vehicle. They must hold up to highway speeds, rough roads, tight turns, heavy braking, vertical forces (up and down) and rapid acceleration. Any part of a hail shield rig that becomes dislodged could severely damage another vehicle and/or cause an accident. It is for this reason that I chose to drill into the roof of my car and attach permanent mounting bolts rather than use straps or magnets. If a roof rack is used for mounting, be sure it can support the additional weight of the rig.
  2. Visibility: The shields and their frames must not obstruct the driver's view out of the windows in any direction during normal driving. This is both to allow for photography and video, but is also necessary to stay in compliance with the law.
  3. Vehicle access: The shields and their frames must not block access to any of the vehicle's doors.
  4. Adequate hail defense: The shields must absorb repeated impacts from the largest hailstones without allowing any part of the hail or the guards to contact the windows. Lighter mesh shields are prone to bending/denting inward with each hailstone strike, and should be mounted far enough from the glass to avoid contact. There have been incidents where a mesh shield panel was struck and bent inward far enough that it actually broke the window it was protecting! Wind-blown hail is another serious concern - most hail will be approaching from a slight angle instead of straight down. The higher the winds, the steeper this angle. Guards that only protect hail falling straight down will not provide protection from wind-blown hail.
Additional personal considerations: In addition to the basic requirements I listed above, I wanted my rig to do the following:
  1. Be easy to mount and remove without tools: I wanted a rig that could be installed or removed in 15 to 20 minutes, without tools if need be, mainly to facilitate the next point:
  2. Have the ability to break down and transport inside of the car: Since hail shields significantly lower the gas mileage of the car (due to added weight and wind resistance), I wanted a rig I could carry inside the car on long chase trips. The rig could then be assembled and mounted on the morning of a chase where there was a risk for a large hail encounter, then removed once a series of hail-risk-present chases concluded. I would then preserve my car's MPG on the long trips to and from the Great Plains, as well as during long repositioning days in between chases. It turns out that my finished rig reduces my car's MPG from 38-39mpg highway to 30mpg highway, so this stowing capability turned out to be just as important as I'd expected.
  3. Have a deployable second stage: I wanted a set of shields that would provide good protection from near-straight-down trajectory hail in their basic configuration, but also have a deployable "Stage 2" set of shields that would protect from wind-blown hail on a temporary basis. Basically, this Stage 2 would be a "batten down the hatches" mode for an expected large hail encounter. Since these "Stage 2" shields would interfere with the visibility out of the windows (for both photography and driving safety), they cannot be left deployed full-time. Some mechanism, either automatic or manual, would be required to lower the Stage 2 shields.
  4. Be as unobtrusive as possible: Unlike in the past, I prefer to have a car that does not look much like a storm chasing vehicle. A hail shield rig is difficult to make 'blend in', but I wanted to try and keep it as low-profile as possible.

My hail shield rig design

I settled on this design that satisfied all of my requirements (click to enlarge the drawing):

Vehicle hail shield rig plans

(The hardware is not shown in this drawing, see the parts list below) The rig's main frame is made from 1" aluminum box beam. Cross members are either 1" aluminum box beam or L-beam. The shield panels are all either 12" or 16" wide wire shelving panels, cut to fit where necessary. The rear window shields are supported by an independent set of box and L beams, hinged in three places to allow the trunk lid to open. The front windshield section is self-supporting (cantilevered), but I added two vertical 1/4" threaded rod stabilizers to prevent the slight bouncing movement that was present.

The shield panels are attached to the frame members using 1/4" bolts and 1 1/2" fender washers. All critical attachments have at least two bolts. Wing nuts are used on all bolts that must be removed for breakdown and storage. 75lb cable ties are used to provide a backup securing method should any of the bolts work loose. The Stage 2 side panels are hinged using multiple 75lb cable ties, and are raised/lowered manually. The stage 2 panels are stowed and secured with metal carabiners, which also serve as a redundant securing method should the cable ties fail. The entire rig is spray-painted with flat black RustOleum.

The total cost for all parts was slightly under $300, and the total weight of the rig is just over 50lbs. The entire thing took two days to build.

And here is the final result:

Vehicle hail shield rig

Parts List

3" x 1/4" hex bolt2
5" x 1/4" hex bolt4
2" x 1/4" hex bolt30
1/4" hex nut20
1/4" hex connector2
1/4" wing nut24
3" x 1/4" clevis (pivot) pin4
1/4" clevis (pivot) pin clip4
2" cotter pin2
2" x 2" x 1/2" steel L-bracket2
18" x 1/4" threaded rod2
1 1/2" dia 1/4" fender washer52
1" square x 96" aluminum tubing (box beam)3
3/4" square x 36" aluminum tubing (box beam)2
1" x 96" aluminum L-beam1
3/4" x 36" aluminum L-beam1
16" x 48" wire shelving panel10
12" x 72" wire shelving panel2
12" x 48" wire shelving panel2
8" 75lb cable tie100
2" metal carabiners8
RustOleum flat black spray paint can4
Clear silicone sealant tube1

Vehicle hail shield rig parts

I chased with my shield rig mounted on the car between April 2-9, putting over 800 total miles on it. I encountered no problems (no loosening bolts or vibrations) other than the reduction in MPG. I lowered the stage 2 side guards twice when making intercepts of supercells - once on April 8 and again on the 9th - but did not encounter hail larger than nickel size.

That is great idea. With the way the price of everything keep going up I don't blame you. One advantage is it keep you guys out of harms way. Stay safe.
- Posted by Sonia Groves Hazlett from London, Oh

Dan, Think of your El Reno experience. I would imagine that you would certainly have had this in place and deployed on that day. Would the additional drag not have made your escape that much more difficult? My 2 cents. Have a great storm season, and stay safe.
- Posted by John from BC, Canada (But moving back to North Texas soon.)

John, that's true - however, I'd like to think that in the next El Reno storm, I wouldn't be anywhere near in the same position in the first place. If ever in a similar situation, I'd be on a hair trigger to bail north into the hail core, which I can now do with no worries.
- Posted by Dan R. from New Baden, IL

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