Saturday, January 30, 2010

Flat Glass - Legacy of the Tin Tent

Ultra Van #366 (Tin Tent) has seen a lot of changes in its time. After all, you don't get a motorhome that will beat 20 seconds in the quarter mile by accident. But most obvious - and perhaps most radical - is the flat glass windshield.

In 2004, when many UltraVanners were wondering if replacement windshield scarcity be would be the Achilles' heel that finally forced their beloved coaches off the road, 30-year UltraVeteran Walt Davison decided to see if it would be possible to fabricate a custom windshield out of cheap and readily available flat-plate laminated safety glass.

Walt wanted the largest span of flat glass that would fit into his Ultra without irreversibly altering the structure. He also felt that the main section should be rectangular to permit easy repair while traveling away from home.

He found that he could fit a 76.5" x 22" sheet of glass in place if it were set back from the original center section by 5 inches at the bottom and 2 inches at the top. This left the glass nearly flush with the body at the outboard corners.

Careful layout was required to generate two irregular smaller glass pieces to fill in at each side.

The original Ultra Van windshield installation used a simple H-section rubber seal that slipped over the glass on one side and the body sheet metal on the other. This technique was typical for the time, and it works adequately as long as the windshield curvature matches the body contour. It does tend to develop leaks easily though, and requires frequent seal maintenance.

Current practice, however, is to take advantage of modern sealant technology and bond the glass in place. For this you need structure to overlap the glass, so Walt and his assistant constructed support angles out of 0.040" aluminum sheet and sealed & riveted them to the existing Ultra Van structure. Because of the large inset of the lower main glass, they also installed additional supports underneath.

The glass panels were set into place with small rubber pads behind them, and quarter-inch wood shims underneath them, to create spaces which were then filled with transparent silicone RTV. The seams between the window facets were also filled with the clear sealant. After this cured, the wood shims were removed and the resulting gaps were filled with more of the RTV.

Once the glass was securely installed, the aerodynamically shaped fairings had to be created out of urethane foam, e-glass cloth, and polyester resin. After shaping, glassing, filling, sanding, more filling, and copious additional sanding, the fairings were painted to match the coach and bonded into place using clear RTV and white 3M 4200 sealer.

The final touches included modifying the windshield wiper arm to fit the new configuration, and installing interior panels to give a finished appearance. Walt is a professional pilot (retired), and has always been fanatical about weight reduction, so his interior treatment is somewhat unique.

Because they can be so hard to find, many Ultra Van owners buy extra OEM windshields whenever they find them available, and store them against future need. These can cost anywhere from $1000 on up to whatever the market will bear, and in the event of an accident away from home, the panels have to be shipped to the coach location - delaying an already painful repair job.

Though Walts flat glass project took well over 60 hours of skilled labor to complete, the glass itself only cost $100 for the large section and $25 each for the four smaller pieces - making them quick, cheap, and easy to replace literally anwhere in the country.

Walt was quite pleased with the finished product, though he acknowledges it would not be right for everyone. As long as the OEM glass continues to be available, it is undoubtedly an easier solution.

Walt retired from Ultra Van ownership in 2007, but he is still an active member of the Ultra community, and is more than happy to answer questions and give advice backed by his 32 years operating four different Ultras (#371, #452, #286, and #366). He can be reached easily through the Ultra Van message board at Yahoo! Groups.

For many more photos of Ultra Van #366, please see Scott Pilkington's photo album: Walt Davison's 366, Innovation and thought at every turn

Photo Credits:
Tin Tent in Almond Grove
Tin Tent in Big Sky Country
by Walt Davison

2nd image from top
by Flickr user erikogan

Interior photo
by Dan Kling (owner, UV #299)

All other images
by Scott Pilkington (owner, UV #350)

Most of the information in this post, and several of the photos were taken from the following newsletter articles:
Whales on Wheels Vol XXV #4 (2004, Jim Isbell editor)
"New Flat Windshield From Walt 'lite' Davison"

Whales on Wheels Vol XXVI #1 (2005, Jim Isbell editor)
"A Solution to a broken windshield, the Flat windshield"
by Walt Davison

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