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Discussion Starter · #1 ·
Hey Guys,

Just finished mounting my solar panels to my roof rack. I'm hyper anxious about these things becoming airborne during driving. I couldn't use the Renology mounts that were provided with the panels so I bought some Rafter connectors to mount the solar panels to my roof. Once installed they were really sturdy but they are thinner metal than the renology ones which made me paranoid, so I'm going to install rope wire to be insurance in the case these panel mounts fail.






On top of this was thinking about buying/making a roof rack fairing strip to reduce noise and airflow on the underside of the panels during transit. I searched the forum and wanted to see if anybody had done something like this. https://www.thefitrv.com/rv-tips/building-a-roof-rack-mounted-wind-fairing-for-the-travato/ or if anybody had bought one and installed it. My solar panels are 25.5" wide and are spaced roughly 6-8 inches apart so total its about 60" of coverage needed in roof fairing.

happy van-ing!
 

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I think you have a sufficient system to keep the panels on. After all there are people who have nothing under their roof brackets but double side adhesive tape! Those folks have not reported any lost panels (yet).
 

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I agree with RD, those rafter ties should be plenty strong. A number of the roof rack companies (Yakima, Thule, etc) make wind deflectors. But it seems most folks don't feel the need, so why not give it a try without first. If you go that route, consider moving your panels together to close the gap and use a single extra-wide wind deflector. Or, you could fabricate your own.
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi,
Nice job.


I agree with the others that the attachment looks secure.


On the fairing...


I'm a bit skeptical that a fairing like the one FitRV used would reduce drag and improve gas mileage.


On the plus side, it cuts off some of the flow under the panels and this should help a little bit with skin friction drag, and it may have a little better drag coefficient by smoothing the airflow over the rack/panels a bit. But, on the negative side, it increases frontal area substantially, and drag depends directly on frontal area.


Consumer Reports did a little test on racks with and without a fairing and came up with this...
What's the Impact of Carrying Stuff on the Roof?

Securing things on the roof increases aerodynamic drag, making the engine work harder and hurting fuel economy.
When we tested a 2013 Honda Accord at a steady 65 mph, it got 42 mpg with nothing on the roof. Adding an empty bike rack dropped the mileage by 5 mpg. A wind deflector reduced the wind noise but cut gas mileage to 35 mpg. And with two bikes on the rack, gas mileage dropped to 27 mpg, a whopping 15-mpg difference overall.
Similarly, when we tested a 2008 Camry with a large car-top carrier, fuel economy dropped by 5 mpg. Going across town, this may not be a concern. But on a multistate family road trip this summer, a carrier or rack on the roof would have a real impact on fuel costs. And it could create some annoying wind noise.



https://www.consumerreports.org/fuel-economy-efficiency/how-to-get-the-best-fuel-economy-now/

So, adding the fairing decreased wind noise a bit, but reduced MPG by about 6%. The effect on the van might be a bit less as their base car is cleaner than the PM.



You might consider adding a bullnose fairing to the front of the solar panel, and a boattail fairing to the back of the solar panel - both only as thick as the panel itself. The bullnose should reduce airflow separation just behind the leading edge of the panel, and the boattail should reduce pressure drag on the back of the panel. Aerodynamics is tricky, but it would be hard to go wrong with these two fairings.



Gary
 

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This is a custom fairing I have had for about 4 years. Before the van was uplifted I got about 22 MPG and after unfitting, more weight plus rack, awning, and solar panels on top, I get about 17 MPG. Not sure really about the effectiveness of the fairing in mitigating drag. It does not cover the awning but I do not notice any noise from the rack, awning and solar panels.
 

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Discussion Starter · #8 · (Edited)
I forgot to mention that I also had added a small strip of VHB 3m tape to the bottoms of the rafter ties in order to properly seat and add further adhesion to the solar panels. I wasn't super impressed with its stickyness unless It needed longer to "set" than I had given it time for. So i'm glad I've gone the route of using the Rafter ties to the metal bar frame.

Also my panels are rear mounted, I don't know if that will make the need for a fairing less or greater.
 

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2018 159 High Roof gas, BC, Canada
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Hi,
Nice job.


I agree with the others that the attachment looks secure.


On the fairing...


I'm a bit skeptical that a fairing like the one FitRV used would reduce drag and improve gas mileage.


On the plus side, it cuts off some of the flow under the panels and this should help a little bit with skin friction drag, and it may have a little better drag coefficient by smoothing the airflow over the rack/panels a bit. But, on the negative side, it increases frontal area substantially, and drag depends directly on frontal area.


Consumer Reports did a little test on racks with and without a fairing and came up with this...
What's the Impact of Carrying Stuff on the Roof?

Securing things on the roof increases aerodynamic drag, making the engine work harder and hurting fuel economy.
When we tested a 2013 Honda Accord at a steady 65 mph, it got 42 mpg with nothing on the roof. Adding an empty bike rack dropped the mileage by 5 mpg. A wind deflector reduced the wind noise but cut gas mileage to 35 mpg. And with two bikes on the rack, gas mileage dropped to 27 mpg, a whopping 15-mpg difference overall.
Similarly, when we tested a 2008 Camry with a large car-top carrier, fuel economy dropped by 5 mpg. Going across town, this may not be a concern. But on a multistate family road trip this summer, a carrier or rack on the roof would have a real impact on fuel costs. And it could create some annoying wind noise.



https://www.consumerreports.org/fuel-economy-efficiency/how-to-get-the-best-fuel-economy-now/

So, adding the fairing decreased wind noise a bit, but reduced MPG by about 6%. The effect on the van might be a bit less as their base car is cleaner than the PM.



You might consider adding a bullnose fairing to the front of the solar panel, and a boattail fairing to the back of the solar panel - both only as thick as the panel itself. The bullnose should reduce airflow separation just behind the leading edge of the panel, and the boattail should reduce pressure drag on the back of the panel. Aerodynamics is tricky, but it would be hard to go wrong with these two fairings.



Gary
Wow! That's a serious impact from the fairing. Anyone with thoughts on why the additional decrease in fuel mileage? My own gut feeling would be that at worst, it would have been a neutral effect and would have more likely even improved it a tad.

I will be a long-distance traveller and so I would feel a 6% reduction in mileage.
 

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2018 3500 Ext
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Interesting consumer reports article, outside of the testing being done for comparison at the legal speed limit... perhaps going slower is better, right? Isn't that the usual case?
 

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I expect flex panels taped or glued to the roof would be a viable system now they have been out a while. Near zero increase drag.
https://smile.amazon.com/ALLPOWERS-...ateway&sprefix=flex+sola,aps,362&sr=8-18&th=1
I am really leaning toward the flex panels for my build. Not only do you have reduced gas mileage, but also noise, more difficult to clean roof, more weight up high, and increase in side sway in crosswinds. I know polycrystalline panels are more efficient but I can just add another panel.
 

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I think you have a sufficient system to keep the panels on. After all there are people who have nothing under their roof brackets but double side adhesive tape! Those folks have not reported any lost panels (yet).
Perhaps they are too embarrassed to do so. I know I would be.
 

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I am really leaning toward the flex panels for my build.
I've always been curious how folks mounting flex panels deal with all the roof ridges and valleys on a PM. I keep imagining a scary big roof-vent adapter.

RE: VHB tape mounts, I just bumped into https://amsolar.com/. They have been manufacturing and installing solar panel mounting hardware for years that only attach with VHB tape, a mere 2 sq.in. on each corner. No one has ever reported a panel detach. And why would they keep installing them if they did? Surface prep and heat is the key. They have instructional videos.
I am grateful for all the fairing wisdom and experience. I think I'll just stop worrying about it ;)
 

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2018 159 High Roof gas, BC, Canada
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I've always been curious how folks mounting flex panels deal with all the roof ridges and valleys on a PM. I keep imagining a scary big roof-vent adapter.

RE: VHB tape mounts, I just bumped into https://amsolar.com/. They have been manufacturing and installing solar panel mounting hardware for years that only attach with VHB tape, a mere 2 sq.in. on each corner. No one has ever reported a panel detach. And why would they keep installing them if they did? Surface prep and heat is the key. They have instructional videos.
I am grateful for all the fairing wisdom and experience. I think I'll just stop worrying about it ;)
Myself, I stopped worrying (more or less...) the "other" way. In that I've already cut a 14x14 hole in the roof plus a small one for the wiring gland, plus a ton of screws through the roof. ...a few more screw holes don't bother me (much...). :)
 

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This is a custom fairing I have had for about 4 years. Before the van was uplifted I got about 22 MPG and after unfitting, more weight plus rack, awning, and solar panels on top, I get about 17 MPG. Not sure really about the effectiveness of the fairing in mitigating drag. It does not cover the awning but I do not notice any noise from the rack, awning and solar panels.
Hi,
I am in the process of selecting a system that will support my solar panels installation as well as an awning (Thule probably) when I am ready for this. I have seen so many posts that my head is spinning ... What awning did you purchase and why?
Thank you,
Valerie
 

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PSA,
The owner believes a fairing would have prevent this damage, "My front panel tore out of two Z clips, folded in half like a taco"
75008

these are the mounts
75017
 

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PSA, The owner believes a fairing would have prevent this damage, "My front panel tore out of two Z clips, folded in half like a taco"
Sounds to me like the Z-clip fasteners, or the roof rack itself, was under-engineered. The vast majority of us have kept our panels in place without a fairing.
 
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