Question s regarding mounting panels on a curved roof?

[PNW_Steve]

Sorry about all of the off topic posts.

That picture would suggest you can mount a number of panels if you have the linear space to run them.

What I can't tell you is what type of bolts or lugs you should use for those channels. It would depend on the roof material and structure (if any) that makes the roof rigid.

I have the space.

I am confident in my ability to attach the Unistrut to the roof securely.

The roof consists of steel frame members about 24" O.C. covered with 15 gauge steel that is riveted to each frame member.

My biggest concern is that I support the panels adequately.

An option that I am contemplating is to follow the example in the picture and add 2 "L" brackets at each end of the panels.

[SunEagle]

This has been fun and interesting but I am still looking for thoughts on the mounting method shown in the picture?

Thanks

S.

Sorry about all of the off topic posts.

That picture would suggest you can mount a number of panels if you have the linear space to run them.

What I can't tell you is what type of bolts or lugs you should use for those channels. It would depend on the roof material and structure (if any) that makes the roof rigid.

[littleharbor]

Thanks all for your participation.

Looks like I am going to have to "wing it".

I think that I will try the method that I asked about and supliment it with some "L" brackets on the ends of the panels.

Just thought Id mention. I mounted a 120 watt panel on the downward sloped roof on my 5th wheel. Worst place as far as wind coming over the roof of my truck is concerned. I used 4 , 2 1/2" x 2 1/2" angle brackets and self tapping screws. One thing I did was clean the surface of the roof at the mounting points then used 3M 5200 sealant/adhesive under the bracket. Very minimal attachment plan. Well even at 75 MPH on Arizona highways and many years of travel the panel is as solid as the day I mounted it. I'm not recommending using such minimal attachment methods but what I am saying is that you really don't need to overengineer this mounting plan if the wind while traveling is your main criteria.

As I mentioned a few posts back I would build an air foil at the leading edge.

[Ampster]

I posted some where on this thread about some $10 brackets (set of 4) but it must have got deleted. I did a google search and some Amazon parts came up. I have actually seen them on flat roofed RVs.

[PNW_Steve]

Thanks all for your participation.

Looks like I am going to have to "wing it".

I think that I will try the method that I asked about and supliment it with some "L" brackets on the ends of the panels.

[J.P.M.]

This has been fun and interesting but I am still looking for thoughts on the mounting method shown in the picture?

Thanks

S.

FWIW, if vehicle and/or road vibration were not a consideration, I'd use standard residential rails attached to the panels, but to be safe, I'd pay attention to the rail to panel clips/attachment method, as standard type clips, etc. may not be designed for the cyclic vibration and stress they might likely encounter in this application.

As for the attachment to the vehicle roof in the photo, it's hard, for me at least, to comment on the method shown in the photo. Bolting as appears to be used per photo may be a sufficient method as long as sealing against moisture ingress can be adequately addressed, but the quantity, size, spacing and sealing/gasketing of such bolting makes it impossible for me to comment on the adequacy of the design. It looks nice, but without knowing what the design conditions are that need to be met, from engineering design and safety standpoints, its adequacy cannot be known or estimated.

[PNW_Steve]

This has been fun and interesting but I am still looking for thoughts on the mounting method shown in the picture?

Thanks

S.

[PNW_Steve]

For me at least. Some people like to boon dock where there aren't any trees. So using solar panels will help extend their batteries.

My wife (and I) prefer a grid tie power connection and parking in the shade with our RV. To each their own.

Yeah... Not much shading problem in Yuma

We like to spend time in AZ and Sonora in the Winter.

[SunEagle]

Haha, that is the irony of putting solar panels on an RV.

For me at least. Some people like to boon dock where there aren't any trees. So using solar panels will help extend their batteries.

My wife (and I) prefer a grid tie power connection and parking in the shade with our RV. To each their own.

[Ampster]

The problem with RV type solar panels is that most people like to park in the shade to keep their coach cooler. But for some reason the lack of direct sunlight seems to reduce the pv production output.

Haha, that is the irony of putting solar panels on an RV.

[J.P.M.]

And at speed, the suction underneath will pull the panels onto the roof . Lots of tricky stuff happens after 40 mph. Thats when wind starts getting some real energy in it

Depending on deflector design orientation and intended purpose, I believe you may have the direction of the vertical forces reversed. I would think that for the simple example of still air and a 60 MPH vehicle velocity, and a flat deflector at some angle at the front of the roof of the vehicle with the deflector's leading edge at the vehicle roof and the trailing edge height ~ the same height as the panels (or a straight vertical bluff for that matter) and reducing the relative air velocity under the panels, that the relative air velocity would be greater above the array than below the array. If that's the deflector orientation and result, Bernoulli's Principle would tend to result in lower pressure for greater fluid velocity over the panels and so an upward force from higher pressure below the panels would be exerted on the panels/array and so cause the array to have an upward (tensile) force on the array supports. That's an oversimplification for description of the principle.

As you write, tricky (and I'd add unexpected) stuff can and will happen in the real world. If the deflector orientation were to be changed from what I described so that the relative magnitude of the flow velocity beneath the array was greater than above, the induced force on the array would be downward. But I can't see a downward force from the simple initial conditions I've specified and the deflector orientation as I initially specified. For most real world conditions, I might also be concerned about flow induced vibration of the relatively flimsy panel surfaces and the fatigue damage that might result, but that's just one of any number of tricky things you mention that might be addressed if a rigorous analysis to be done.

[Mike90250]

The first thing I'd consider would be adding a foil at the leading edge to deflect all wind over the panels

And at speed, the suction underneath will pull the panels onto the roof . Lots of tricky stuff happens after 40 mph. Thats when wind starts getting some real energy in it

[Ampster]

And just how would you go about that ?

If you are referring to the foil it depends on the foil.and where it is mounted in relationship to the front of the bus. Right now it is a concept suggested by littleharbor. As far as specifics, I will leave that up to the OP to decide what works for him.The foil could be placed a few inches ahead of the panels or he could drill some holes in it.
If you are referring to parking in the shade it would depend on the time of day.

[J.P.M.]

At 60 MPH I am not sure it would make them much hotter because you could design the foil to allow some air but deflect the uplift forces. The biggest heat issue will be when you are stationary. If you park in the shade that wont be much of an issue.

And just how would you go about that ?

[SunEagle]

At 60 MPH I am not sure it would make them much hotter because you could design the foil to allow some air but deflect the uplift forces. The biggest heat issue will be when you are stationary. If you park in the shade that wont be much of an issue.

The problem with RV type solar panels is that most people like to park in the shade to keep their coach cooler. But for some reason the lack of direct sunlight seems to reduce the pv production output.