Chevy express - Questions on how to use all roof space using ladder racks.

[gsnz]

Hi all! I had another thread asking about solar panels on a chevy express, and I was pointed to ladder racks as being a great way to not drill into the roof, and have something I can shift around.

I really like ladder racks compared to the single unit racks that offer zero adjustability in the cross bars. I like ladder racks because if I change solar panels, the only thing I need to do is move one of the racks to get the edges of the new panel lined up to the crossbars, and then I can bolt the new panels into the ladder rack.

So I've been looking at the profile of the chevy express, as well as the typical mounting points where people tend to place the three ladder racks on a chevy express. Typically, it looks something like this:



As you can see, as the gutter reaches the front doors, it slopes downwards, and the seems to be why they mount the front rack further back - so that the rack is roughly still the same height as the rest of the two racks mounted along the flat part of the gutter.

The issue I have with this of course, is there is a sizeable amount of roof space in front of the front ladder rack that would largely be unused! I could fit another 100 watts in this space!


So I thought, okay, I can just buy another set of racks, and place another one at the furthest point forward where the gutter is still mountable to:


With this though, the crossbars at the front door section are not vertically level with each other. So at this point I see two solutions -

1. Go with round bar ladder racks at the front of the van so I can mount a smaller solar panel towards the front of the van at a downward sloping angle:


OR
2. Keep flat square bar racks, but find a way to shim the front-most bar such that it is level with the rack bars behind it


I'm not exactly sure what I'll do in this situation. My desire is to keep all the panels flat on the roof

Anybody have any thoughts on how to account for this sloped gutter and still use all of the valuable space of the express? Is there a way to keep the panels flat through the entire length of the roof?

 

[maki2]

you may have forgotten to think the idea through for the potential negative consequences of what safety issues your idea might create. It is easy to get caught up in the exciting benefits of having more solar gain and forget that our ideas can also create other issues.

You do not want to have a large area underneath of overhang like that at the front edge of the vehicle. If you are driving at 75mph that is essentially hurricane force winds (or stronger if driving into a head wind). Your forward solar panel will then aerodynamically be forced into a lift up and off your vehicle stress situation. Plus it will increase your fuel consumption by interfering with the intended smooth air flow up and over the top of your vehicle.

So keep your panels further back on the roof where they are positioned closer to the surface or let that forward panel slope down reduce the size of the gap.

But of course there is another possible solution. Some people put a curved section of metal at the front edge of the panels to help redirect the wind force up and back over the top of the panels which keeps the lifting stress reduced while also improving gas mileage with less wind stream turbulence that is created by a gap under the front panel edge.

 

[tx2sturgis]

I agree: Instead of messing with physics and aerodynamics by adding a panel over the front curved shapes, I'd just reduce power consumption and/or use an additional portable panel when stationary, rather than risk damage to the panels and a loss of MPG due to the spoiling of the aerodynamic surfaces.

 

[user 22017]

I agree: Instead of messing with physics and aerodynamics by adding a panel over the front curved shapes, I'd just reduce power consumption and/or use an additional portable panel when stationary, rather than risk damage to the panels and a loss of MPG due to the spoiling of the aerodynamic surfaces.

People with truck campers have figured out ways to block the wind from traveling under the overhang (bed area). If the gap is small, some use pool noodles. For larger gaps I have seen deflectors in that area. Can't remember how they made them. They call it porpoising when the wind catches that overhang. It is no fun driving when it does that. I had to switch to back roads in Minnesota.

Here is a small store bought deflector: https://www.mainlineoverland.com/products/ikamper-wind-deflector

Edit: That won't work for you, because your panel extends pretty far forward in the diagram. I'll look for the wind dams that truck camper folks built, because their overhangs are even longer.

Edit 2: Found discussion about air tabs. Never heard of them. http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/27017146/gotomsg/27023864.cfm#27023864

 

[tx2sturgis]

Yep, on my pickup topper I have installed several airtabs and 2 aero spoilers, one is a DIY FRP version and one was metal-shop cut and bent from stainless...the result is that the mpg is about the same or better as the stock pickup got without the topper.