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Old 05-18-2021, 11:45 AM   #1
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Rollover Safety: Fiberglass hightop vs Poptop

Hi everyone,

I've been scouring the forum and the rest of the internet, but have come up with very little compelling info regarding this topic. I'm interested in how installing either a fiberglass hightop or a poptop on a van impacts the rollover safety of the vehicle?

I see that the Sportsmobile penthouse for the low-roof mercedes vans meets "Roof Crush Resistance Test FMVSS 216" but they don't list any safety requirements or tests of their E-series installations. I don't see any safety requirements listed on the Colorado Campervan website for their poptops, nor on the Fiberine website for their fiberglass tops.

I can only assume that whatever top is installed on the van is not going to be as strong as the original van roof structure, so I guess the question to be asking is - how much material is removed in order to install these tops, and how does that impact rollover safety? I want to know what I'm signing up for in terms of safety before we start traveling with our family in one of these vans. These kinds of decisions were a lot easier before we had kids to worry about!
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Old 05-18-2021, 12:12 PM   #2
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Rollover safety is based how top heavy the vehicle is. Add a lift kit...less safe...add a ton of weight to the roof..less safe.

I'm not sure what scenario you are envisioning but they don't have a test for what the roof material is made of.

Think about this...some cars come without a sunroof and they also have an option for a full panoramic sunroof. Glass vs sheet metal? Doesn't matter, it is the vehicles ability to maintain its structure without collapsing. The safety rating doesn't change.

The penthouse or fiberglass top is a technique used for decades. The structure remains intact at the important points.

Your assumption of strength may or may not be valid but it is based on an imaginary scenario that doesn't match standard testing. Feel free to expand on your theory.
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Old 05-18-2021, 12:40 PM   #3
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I see it like this. Take a steel box and remove one side, replacing with a piece of fiberglass. Toss it around your driveway for awhile and see which side gets destroyed first. It will be the fiberglass side.

For that reason I would worry about the seat belts a lot more than the one side that used to be stronger but no longer is.
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Old 05-18-2021, 01:49 PM   #4
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Rollover Safety: Fiberglass hightop vs Poptop

From what Iíve seen, the SMB Sprinter Penthouse design is essentially the same as their E-van design. So Iíd assume similar results if the Ford PH was actually tested. Apparently Mercedes required certification for SMB to get designated as an approved vendor. Likely Ford did not (or SMB is not an approved vendor, I donít know).

With the steel L-channel that SMB uses to reinforce the opening, combined with the fiberglass top, I feel that itís perfectly safe. The original steel roof is not that thick and I doubt it would provide much more, if any, protection than the fiberglass roof. One issue that has been raised is the PH top detaching in a roll-over incident. I believe SMB updated their design to have seatbelt sort of latches front (2) and rear (1) in addition to the j-hooks. My 2011 van has them, my 1998 didnít.

I agree with Eric, too, about seatbelts. I know they are certified, but the captains chairs with integrated seatbelts just donít look as secure to me as ones where the upper belt is bolted to the van wall.
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Old 05-18-2021, 01:52 PM   #5
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Take 86scotty analogy and add a box frame inside the panel structure. The fiberglass panel might crack but the frame would be intact. That is more accurate.
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Old 05-18-2021, 02:34 PM   #6
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Thanks everyone for your replies! See my thoughts below. Hopefully this will continue to generate some good discussion.

simplesez - I suppose I should have asked my question a different way: if/when the vehicle rolls over, how well will the body of the vehicle withstand the crush force? Will it be more likely that the body caves in on a vehicle with a hightop/poptop? There may not be a test for what material the roof is made of, but there is a roof crush resistance test that SMB claims to meet with their Mercedes otp. I understand that poptops and fiberglass tops have been used for a very long time, but that doesn't necessarily mean they are as safe as the OEM van body. Of course using the OEM van body as a reference for "safe" is perhaps not a great assumption either. Regarding your example of a car with or without a sunroof, to me that is a different situation because the car mfg knows and plans for the fact that a sunroof will be offered on some models. So the surrounding areas are designed accordingly to meet whatever requirements they have, with or without a sunroof.

86scotty - I see what you're getting at, but I'm not necessarily concerned about what breaks first. Rather, I'm concerned about whether the roof will cave in if the vehicle rolls over. In your analogy, which box takes less force to cave in, the box with 6 steel sides, or the box with 5 steel sides and one fiberglass side? My bet is the box with 1 fiberglass side.

BrianW - thanks for your input regarding the design of the Mercedes penthouse to the E-series penthouse. It makes sense to me that the design would be very similar between the two in order to minimize design/mfg effort for SMB. Also very good information regarding how they use steel L-channel to reinforce the roof opening.

In general, I appreciate everyone's reasoning for why they feel the poptop/hightop is safe. But I'm wondering if there is any data out there, or if any of the various manufactures make any claims of meeting certain safety requirements (like SMB and the roof crush test).
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Old 05-18-2021, 07:42 PM   #7
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Yours are good questions. They have me wondering.. who are the folks that design these tops and how they attach to the body? Are they professional engineers who perform the load and structural analysis that is called for, and are able to certify the results? Or are they more like mechanics who just take their best guess at what "seems adequate" without really knowing how safe the structure actually is? Hopefully it's the former and not the latter!
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Old 05-18-2021, 07:53 PM   #8
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Everyone knows Van's are not the safest vehicle out there. A high center of gravity with fairly narrow (at least rear) wheel width makes for a tippy van.
If you have ever seen a van after it rolled the sheetmetal top skin and the 4 or 5 stamped metal crossbraces are no match for the forces involved when a van rolls.
I would think in some cases a raised roof van would be safer. From the aspect it would be harder to get that big box to roll over.


There is no question that 15-passenger vans are over-involved in single-vehicle rollover crashes compared to other passenger vehicles. From 1991 to 2000, 33 percent of passenger vehicles involved in single-vehicle, fatal accidents experienced a rollover, compared to 52 percent for 15-passenger vans involved in such crashes. A shocking 81 percent of all 15-passenger van occupant fatalities occurred in single-vehicle rollover crashes.
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Old 05-18-2021, 08:10 PM   #9
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Quote:
Originally Posted by Lilnuts2 View Post
A shocking 81 percent of all 15-passenger van occupant fatalities occurred in single-vehicle rollover crashes.
I wonder if lack of seat belts isn't behind this statistic. Typically, is everyone in a 15-passenger van secured by a full set of lap belt and shoulder harness, or is it more akin to riding in the city bus. ie, most occupants are not secured in any way? A rolling van with multiple unsecured passengers is bound to end badly.
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Old 05-18-2021, 08:25 PM   #10
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In my 2002 15 pass, all passengers have seatbelts but only the driver and the front passenger belts are alarmed.
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