Fitting solar panel to roof rails ?

[headlight]

When I had my solar fitted I was told that there was only room for a single 115 watt panel.
I have roof rails/rack but was told you couldn't fit solar panels to it.
As the rails/rack are designed to have a top box or similar fitted I would have thought that they would take a solar panel ok ?
Would there be any problems in fitting a solar panel to the roof rails/rack on my Swift Suntor ?
Also my MPPT is a Victron 75/15.
The most amperage I have seen the 115 watt panel I have producing is 6 amps.
Would my MPPT handle another identical 115 panel presumably doubling my amperage to 12 amps ?

 

[Tombola]

Would my MPPT handle another identical 115 panel presumably doubling my amperage to 12 amps ?

yes, approx max input voltage is 75 and 15 amp

your 2 panels will be about 35-40 volts

 

[meanders]

I suspect that fitting them to the rails would create significant aerodynamic problems when moving at speed. If we'll away from the roof, the buffeting would likely rip them off, (or the rails ). If very close to the roof it would tend to create a vacuum which could crack the panel or delaminate the roof.

I wouldn't risk it.

 

[Otter Spotter]

If you used the bifacial solar panels then because your panel would be further away from roof than normal you may benefit from the extra power generated. Even better if your roof is white
Belt and braces panel fitting should keep them safe from flying off.

 

[headlight]

yes, approx max input voltage is 75 and 15 amp

your 2 panels will be about 35-40 volts

Yes the max voltage my panel has produced is 22v so 2 panels would be well under the 75 max input voltage.

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[headlight]

I suspect that fitting them to the rails would create significant aerodynamic problems when moving at speed. If we'll away from the roof, the buffeting would likely rip them off, (or the rails ). If very close to the roof it would tend to create a vacuum which could crack the panel or delaminate the roof.

I wouldn't risk it.

That is basically what the installer said.
However a panel would be lighter than a loaded top box and no more un-aerodynamic so would it really put greater strain on the rack/rails.
Obviously the panel would need suitable support.

 

[Lenny HB]

yes, approx max input voltage is 75 and 15 amp

your 2 panels will be about 35-40 volts

Better to wire them in parallel to avoid shading problems.

 

[headlight]

Better to wire them in parallel to avoid shading problems.

Will the rack/rails take the force/load of the panel though as the installer said no even though the rack/rails (Fiamma) are obviously meant to take force/load otherwise why would they be fitted ?

 

[Otter Spotter]

Will the rack/rails take the force/load of the panel though as the installer said no even though the rack/rails (Fiamma) are obviously meant to take force/load otherwise why would they be fitted ?

Depends on the rails fitting to the vehicle, are they bolted on to roof or snapped into a female fitting in a groove? I suspect they will be bolted, if so may be worth undoing the boots and putting some ‘locktite on before tightening up again.

 

[headlight]

Depends on the rails fitting to the vehicle, are they bolted on to roof or snapped into a female fitting in a groove? I suspect they will be bolted, if so may be worth undoing the boots and putting some ‘locktite on before tightening up again.

Each length ways rail is attached by 3 brackets, each bracket has 4 screws into the roof and mastic.
There are 3 adjustable cross pieces that are bolted to the length ways rails.

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[meanders]

That is basically what the installer said.
However a panel would be lighter than a loaded top box and no more un-aerodynamic so would it really put greater strain on the rack/rails.

I am afraid It would be much more aerodynamic as it's thin so acts like aerofoil. Like a wing it will create lift whenever the front is at the slightest angle to the airflow. It's complex, but if you have an overcab bed for example, the air goes over the top and then drops down to roof level. Depending on where the panel begins, the speed and other factors, it could be just beginning to rise having created a low pressure as it drops down the back of the overcab.

The second issue is the gap between the roof and the panel will act like a Venturi creating significant low pressure, tending to suck the panel down.

I guess with complex modelling and wind tunnel measurements, you could see if it was safe or not, but it's not simple physics I am afraid.

It's your call though. Your panel, your roof, your rails and your van. My fluid dynamics training is half a century old.

 

[Otter Spotter]

I am afraid It would be much more aerodynamic as it's thin so acts like aerofoil. Like a wing it will create lift whenever the front is at the slightest angle to the airflow. It's complex, but if you have an overcab bed for example, the air goes over the top and then drops down to roof level. Depending on where the panel begins, the speed and other factors, it could be just beginning to rise having created a low pressure as it drops down the back of the overcab.

The second issue is the gap between the roof and the panel will act like a Venturi creating significant low pressure, tending to suck the panel down.

I guess with complex modelling and wind tunnel measurements, you could see if it was safe or not, but it's not simple physics I am afraid.

It's your call though. Your panel, your roof, your rails and your van. My fluid dynamics training is half a century old.

So with the aerofoil being sucked down is that going to create a stable panel ? Just asking

A deflector at the front of the panel would help solve your concerns.

 

[PP Bear]

I think you’ll find that you’ll suffer from a similar effect as to that which caused this bridge failure.

Have to remember that there’s glass involved.

Suppose the only answer is to try it and see and hopefully no problems for you or flexing at higher speeds.

 

[PP Bear]

Or fit something like these to deflect any wind.

 

[PP Bear]

I was looking for more details for you and found this in the process, so worth passing on.

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[Jimbohorlicks]

I had a swift Sundance with roof rack and fitted 2 solar panel to the side rails with u bolts. Never had any issues and were easy to clean underneath.
If your concerned you could always fix on a wind deflector ,but don't forget your driving a mhome not a racing car.

 

[headlight]

So this is my roof.
As you can see I have a bulge because of the over cab bed.
What would be the problem with fitting a panel immediately in front of the small roof vent ?
I know that it would be on a slight front to back angle but it could be fitted to the roof with corner brackets the same as the present panel.
I doubt I would lose that much output due to the angle ?

 

[headlight]

And it would stop any potential issues caused by attaching a panel to the rails.

 

[cyberyacht]

Just park with the back of the van facing south and you'll improve the panel output. If you fit a deflector you'll need a DRS for the straights to cut down the drag.

 

[headlight]

I'm just wondering if there would be any issues with fitting the panel on a slight angle.
Output wise although in the middle of the day I might lose a bit of output at other times I could gain a bit so overall probably would be very little difference ?

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[Lenny HB]

I'm just wondering if there would be any issues with fitting the panel on a slight angle.
Output wise although in the middle of the day I might lose a bit of output at other times I could gain a bit so overall probably would be very little difference ?

The most reduction would be when facing south any other way round probably won't have too much effect.
Try the panel before you fix it & see what happens.

 

[headlight]

I had a swift Sundance with roof rack and fitted 2 solar panel to the side rails with u bolts. Never had any issues and were easy to clean underneath.
If your concerned you could always fix on a wind deflector ,but don't forget your driving a mhome not a racing car.

Can you remember how your rack was attached to your roof ?
I'm a little surprised that my roof rack brackets are screwed into the roof and not bolted.

 

[jumar]

Fitting a panel on rails woul give you the opportunity to make a tilting system...I did and by jolly it makes so much difference..

 

[headlight]

I have now spoken to 3 installation firms and Brownhills.
All have said that they won't fit a panel to the roof rails.
They have all also said that they won't fit a panel to the over cab bed roof area as they say that that part of the roof is constructed differently to the rest of the roof and has no structural integrity.
My only option therefore would be a portable solar suitcase.
Any recommendations for a solar suitcase around 100-115 watts please ?
Not Renogy as I have already had a bad experience with their products and after sales.

 

[Jimbohorlicks]

Can you remember how your rack was attached to your roof ?
I'm a little surprised that my roof rack brackets are screwed into the roof and not bolted.

Yes mine were aso screwed in and also sixaflexed .The fixing was sturdy.
I note that you were also thinking of a portable panel.Ifvyou have the storage space then I would try that option first as it doesn't appear that you would be installing any panels yourself ,although they are fairly easy to do.
As an aside I did see a van with a portable set up using a flexible panel .It was lighter weight ,bigger than a suitcase panel but more amps.

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[headlight]

Yes mine were aso screwed in and also sixaflexed .The fixing was sturdy.
I note that you were also thinking of a portable panel.Ifvyou have the storage space then I would try that option first as it doesn't appear that you would be installing any panels yourself ,although they are fairly easy to do.
As an aside I did see a van with a portable set up using a flexible panel .It was lighter weight ,bigger than a suitcase panel but more amps.

I have been advised against flexible panels due to their high failure rate.
I have also been advised not to connect another panel to my present Victron 75/15 MPPT controller ?
I would fit a rigid panel to the roof rails and connect to my present MPPT myself if it wasn"t for the fact that 4 firms have told me that it will either rip off or rip the rails off damaging the roof.
I am still dubious about the above advice considering that if I fitted a top box, like say a Thule, the surface area would be larger than the panel so surely would create more lift and downward force than a panel ?
I don"t really want to use a solar suitcase if I can help it.

 

[Jimbohorlicks]

I wasn't advising a flexible panel to be fixed to your roof,but used as a portable panel. The failure of the flexibles is mainly due to excessive heat build up ,when stuck on a roof ,but as a free standing panel ( fasted to tent poles)there would be airflow all around ,keeping it cool.
I happen to have a spare roof panel that I use as a portable panel ,it just fits nicely in a wardrobe when not in use and I used an older pmw controller that was available and it's just wired up as a plug in panel when we are off grid to charge up a pair of lead acid batteries.

 

[monzer]

It's maybe deceiving with the direction the photo is taken but what length have you got from your existing panel up to where the over cab starts? Maybe enough room for a 2nd panel in there length ways?

 

[headlight]

It's maybe deceiving with the direction the photo is taken but what length have you got from your existing panel up to where the over cab starts? Maybe enough room for a 2nd panel in there length ways?

View attachment 644058

Unfortunately not quite enough room.