Safe to mount rigid panels on the over-cab roof of a class C?

[daveemac]

I have two 200W panels on the roof of my 21' class C Toyota RV, which has an aluminum roof. I mounted them on the flat part of the roof about 1' before the roof slopes to the over-cab, hoping to reduce wind drag.

Now I'm thinking about installing two 100W panels, but the only space left is over the cab.

I'm wondering: do you think the wind drag on these angled panels would significantly reduce MPG? Also, I mounted with VHB tape, which seems to work well with the aluminum roof--would the pull on a panel over the cab be much greater than on the flat part of the roof, and would VHB still be sufficient? Typical speed is 60mph, might go 70-75 if I were in a hurry.

THANKS!

 

[VentureOutThere]

I did exactly that on my slide in truck camper. It has been working great for almost a year. I didn’t notice any reduction in mileage, which was pretty bad to start with.

Solar Panel Installation on Our Truck Camper. Squeezing it all in place with VHB Tape and Unistrut.

 

[chrisski]

I would not secure a glass panel to an RV roof with only VHB tape, and less so at the front of the vehicle. I would want the tape to be secondary, with some sort of physical anchor as primary like a screw.

If you could find flexible panels to tape up there, I do that. All four sides taped with 4” roofing tape with no gaps. That’s $60 of tape Per panel. My flex panels did not match my glass panels and required a separate charge controller.

I’ve measured temps of up to 170 on the roof with an IR gun. That loosens up a lot of adhesives. I had a latch on the side of the RV secured with two sided eterna bond, and that slipped off in the heat. VHB is different, but I’m not sure how it would stand up to extreme heat.

Tape only is a very opinionated topic. You’ll find a few that recommend proper isnataltion with tape and flex panels, more that say not to.

Especially in the winter months, I get much more production out of portable panels angled into the sun.

 

[daveemac]

Thank you very much for your reply.

I went with VHB partially because that's what Will recommends for my situation...unless he changed position recently. My panels are rock solid up there, so far at least. VHB is used by some automakers in some situations where rivets used to be used...

 

[chrisski]

Thank you very much for your reply.

I went with VHB partially because that's what Will recommends for my situation...unless he changed position recently. My panels are rock solid up there, so far at least. VHB is used by some automakers in some situations where rivets used to be used...

I guess you've had luck with it. Will may recommend VHB. I know "RV with Tito" does also.

 

[daveemac]

I did exactly that on my slide in truck camper. It has been working great for almost a year. I didn’t notice any reduction in mileage, which was pretty bad to start with.

Solar Panel Installation on Our Truck Camper. Squeezing it all in place with VHB Tape and Unistrut.

Thank you very much for this, I only saw the 2nd reply initially. I'll watch your video this evening, thanks again!

 

[daveemac]

Are you getting pretty good harvest even though the panels are inclined? Thanks

I did exactly that on my slide in truck camper. It has been working great for almost a year. I didn’t notice any reduction in mileage, which was pretty bad to start with.

Solar Panel Installation on Our Truck Camper. Squeezing it all in place with VHB Tape and Unistrut.

Are you getting pretty good harvest even though the panels are inclined? Thanks

 

[midwestsolarnoob]

I like the idea of using different sized panels to fit space but I could have sworn I’ve read not to use anything but identical panels due to the least efficient will drag the whole array down. Is that not true? As I have a Turtletop VanTerra that we’re in the middle of converting to an off grid tiny home. Which more panels would be great! Especially the idea of flexible where the roof tapers down over the front cab area.

 

[Aussieguy]

you can hook the 2 100w panels to their own controller
or play with finding best series / parallel combo

 

[HRTKD]

I like the idea of using different sized panels to fit space but I could have sworn I’ve read not to use anything but identical panels due to the least efficient will drag the whole array down. Is that not true? As I have a Turtletop VanTerra that we’re in the middle of converting to an off grid tiny home. Which more panels would be great! Especially the idea of flexible where the roof tapers down over the front cab area.

User experience with the flexible panels hasn't been that good. Production hasn't lived up to the specs, panel life is poor (compared to standard panels) and some are seeing delamination.

If you're going to install flexible panels, make sure they are easy to remove so when they go bad or you get fed up with them, you don't have to work too hard to take them off.

 

[chrisski]

On my RV, I have 6 x 100 watt panels flat glass to one SCC, and 6 x 175 flexible panels to a separate SCC.

IMO, it’s easier install flat panels than tape. I find working with roofing tape pretty hard.

 

[HRTKD]

IMO, it’s easier install flat panels than tape. I find working with roofing tape pretty hard.

It's a sticky situation for sure.

 

[midwestsolarnoob]

User experience with the flexible panels hasn't been that good. Production hasn't lived up to the specs, panel life is poor (compared to standard panels) and some are seeing delamination.

If you're going to install flexible panels, make sure they are easy to remove so when they go bad or you get fed up with them, you don't have to work too hard to take them off.

I’ve been seeing that said a lot about the flexible panels. Makes sense. What about running different sized panels to the same scc? Is it worth it? Essentially I have the space on the roof for 4x 450w panels. Can I use portable suitcase panels as an add on? Or would it be better to use another scc to handle the portables?

 

[HRTKD]

I’ve been seeing that said a lot about the flexible panels. Makes sense. What about running different sized panels to the same scc? Is it worth it? Essentially I have the space on the roof for 4x 450w panels. Can I use portable suitcase panels as an add on? Or would it be better to use another scc to handle the portables?

Use a second solar charge controller.

I have 640 watts on the roof and 640 watts on the ground. I thought about putting the two strings in parallel on the same solar charge controller. But decided to use two solar charge controllers. At the very least, it showed me how much more power is produced from tilted panels. But it also gives me more flexibility.

 

[chrisski]

I’ve been seeing that said a lot about the flexible panels. Makes sense. What about running different sized panels to the same scc? Is it worth it? Essentially I have the space on the roof for 4x 450w panels. Can I use portable suitcase panels as an add on? Or would it be better to use another scc to handle the portables?

Every different set of panels needs its own SCC. I have thee different SCCs including one for 9 x 100 watt panels, set up 3s3p that are suitcase panels

 

[carl2591]

I would not secure a glass panel to an RV roof with only VHB tape, and less so at the front of the vehicle. I would want the tape to be secondary, with some sort of physical anchor as primary like a screw.

If you could find flexible panels to tape up there, I do that. All four sides taped with 4” roofing tape with no gaps. That’s $60 of tape Per panel. My flex panels did not match my glass panels and required a separate charge controller.

I’ve measured temps of up to 170 on the roof with an IR gun. That loosens up a lot of adhesives. I had a latch on the side of the RV secured with two sided eterna bond, and that slipped off in the heat. VHB is different, but I’m not sure how it would stand up to extreme heat.

Tape only is a very opinionated topic. You’ll find a few that recommend proper isnataltion with tape and flex panels, more that say not to.

Especially in the winter months, I get much more production out of portable panels angled into the sun.

I can tell you from experience if the VHB tape is installed correctly it is going to take more than like 75 mph winds to remove them from alum surface.. I would image it seem that is not enough but the place in oregon that has installed 100's if not 1000's by now on all sorta roof using just VHB 4950 tape with non that i am aware of coming off. some panels have been damaged by tree limbs that can disrupt the mount..

I would not no problem attaching panels to the front of the class C,, not sure where he is saying to put them with no picture of rig. if you clean the mounting area with alcohol let it dry, press the tape on firmly and give it 24 hrs, more if cooler, to cure and ti will be hard to just pull off the roof by hand.. I have 5 panel attached to roof of airstream this way for over 3 yrs now traveling full time and no issues.

 

[HRTKD]

I can tell you from experience if the VHB tape is installed correctly it is going to take more than like 75 mph winds to remove them from alum surface.. I would image it seem that is not enough but the place in oregon that has installed 100's if not 1000's by now on all sorta roof using just VHB 4950 tape with non that i am aware of coming off. some panels have been damaged by tree limbs that can disrupt the mount..

I would not no problem attaching panels to the front of the class C,, not sure where he is saying to put them with no picture of rig. if you clean the mounting area with alcohol let it dry, press the tape on firmly and give it 24 hrs, more if cooler, to cure and ti will be hard to just pull off the roof by hand.. I have 5 panel attached to roof of airstream this way for over 3 yrs now traveling full time and no issues.

In most cases, when we object to using adhesives (tape or glue) to secure a panel to an RV, we're talking about rubber roofs. The bond that the tape has to the rubber roof and the panel is far greater than the bond that the rubber roof has to the substrate below it. I worry about any RV surface that is adhered to the substrate. That includes fiberglass. An Airstream at least has rivets.

I've seen RV trailers going down the road with a bulge on the roof where the rubber roof material is no longer adhered to the substrate.

 

[carl2591]

In most cases, when we object to using adhesives (tape or glue) to secure a panel to an RV, we're talking about rubber roofs. The bond that the tape has to the rubber roof and the panel is far greater than the bond that the rubber roof has to the substrate below it. I worry about any RV surface that is adhered to the substrate. That includes fiberglass. An Airstream at least has rivets.

I've seen RV trailers going down the road with a bulge on the roof where the rubber roof material is no longer adhered to the substrate.

FOR sure not rubber.. alum only.. some fiberglass composite wall board type roofs might work but rubber is a screw down to wood for sure. the rubber is just floating or with a not so strong glue under it..

 

[McCarthy]

I have two 200W panels on the roof of my 21' class C Toyota RV, which has an aluminum roof. I mounted them on the flat part of the roof about 1' before the roof slopes to the over-cab, hoping to reduce wind drag.

Now I'm thinking about installing two 100W panels, but the only space left is over the cab.

I'm wondering: do you think the wind drag on these angled panels would significantly reduce MPG? Also, I mounted with VHB tape, which seems to work well with the aluminum roof--would the pull on a panel over the cab be much greater than on the flat part of the roof, and would VHB still be sufficient? Typical speed is 60mph, might go 70-75 if I were in a hurry.

THANKS!

If one of your panels flies into my windshield, and I survive, I'd sue you for every cent you may have.

There are many examples where the tape didn't hold up and panels took off. I made a list in a post a while back. Do it right and install a proper rack, with proper hardware.

Just one example.